Petrogenesis of Paleocene-Eocene porphyry deposit-related granitic rocks in the Yaguila-Sharang ore district, central Lhasa terrane, Tibet

Accepted Manuscript Petrogenesis of Paleocene-Eocene porphyry deposit-related granitic rocks in the Yaguila-Sharang ore district, central Lhasa terrane, Tibet Junxing Zhao, Guangming Li, Noreen J. Evans, Kezhang Qin, Jinxiang Li, Xia’nan Zhang PII: DOI: Reference:

S1367-9120(16)30249-8 http://dx.doi.org/10.1016/j.jseaes.2016.08.004 JAES 2781

To appear in:

Journal of Asian Earth Sciences

Received Date: Revised Date: Accepted Date:

19 March 2016 2 August 2016 2 August 2016

Please cite this article as: Zhao, J., Li, G., Evans, N.J., Qin, K., Li, J., Zhang, X., Petrogenesis of Paleocene-Eocene porphyry deposit-related granitic rocks in the Yaguila-Sharang ore district, central Lhasa terrane, Tibet, Journal of Asian Earth Sciences (2016), doi: http://dx.doi.org/10.1016/j.jseaes.2016.08.004

This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

Petrogenesis of Paleocene-Eocene porphyry deposit-related granitic rocks in the Yaguila-Sharang ore district, central Lhasa terrane, Tibet

Junxing Zhao1,2, Guangming Li*1, Noreen J. Evans3, Kezhang Qin1, Jinxiang Li4, Xia’nan Zhang1

1. Key Laboratory of Mineral Resources, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beitucheng West Road 19#, Chaoyang District, Beijing 100029, China 2. Economic Geology Research Centre (EGRU), School of Earth and Environmental Sciences, James Cook University, Townsville Qld 4811, Australia 3. John de Laeter Center, TIGeR, Department of Applied Geology, Curtin University, Perth, WA6945, Australia 4. Key Laboratory of Continental Collision and Plateau Uplift, Institute of Qinghai-Tibetan Plateau Research, Chinese Academy of Sciences, 4A Datun Road, Chaoyang District, Beijing 100085, China *Corresponding author: [email protected]; [email protected]

1

Abstract The Paleocene-Eocene ore deposits in the Gangdese Metallogenic Belt, Tibet, are thought to have been formed during the main period of India-Asia continental collision. This paper reports the whole-rock major element, trace element, and Sr-Nd-Hf isotopic compositions and zircon trace element contents of volcanic and intrusive rocks from the Paleocene Yaguila skarn Pb-Zn-Ag deposit and adjacent Eocene Sharang porphyry Mo deposit in the central Lhasa terrane, Tibet. Geochemical signatures and Nd-Hf isotopic compositions indicate that the Yaguila Cretaceous rhyolitic rocks were formed by the melting of ancient continental crust, whereas the Paleocene causative granite porphyry may have resulted from the interaction between mantle-derived and crustal-derived materials when continental collision was initiated. The dramatic increase of εNd(t) values between emplacement of the granite porphyry and later porphyritic biotite granite suggests a greater involvement of mantle materials during the crystallization of the barren biotite granite stock. The post-ore Miocene granodiorite porphyry has a similar geochemical signature to the Sharang Miocene dykes, suggesting they were both generated from melting of enriched lithospheric mantle. Nd-Hf mixing calculations indicate an increasing contribution of mantle materials in Paleocene to Eocene intrusions, consistent with the regional tectonic model of Neo-Tethyan oceanic slab roll-back and break-off. Zircons from both the Yaguila and Sharang ore-related porphyries have higher Ce anomalies than those from the barren granitoids, suggesting that Mo mineralization was closely related to highly oxidized and differentiated magma. The 2

fertile intrusions in the Yaguila-Sharang district contain EuN/EuN* values from 0.3 to 0.6, higher than the non-mineralized intrusions. The processes of early crystallization of plagioclase and/or SO2-degassing from underlying magma can explain the observed negative Eu anomalies in zircon. Key words: petrogenesis; magma oxidation state; zircon trace elements; porphyry deposit; Tibet.

3

1. Introduction Porphyry deposits are typically associated with highly oxidized magmas, facilitating the transport of metals and sulphur from the mantle to the shallow crust (Richards, 2003; Cooke et al, 2005; Sillitoe, 2010). However, the lack of suitable igneous minerals (such as primary Fe-Ti oxide and hornblende) in felsic intrusions, combined with (typically) intensive hydrothermal alteration, often hampers the determination of relative magma oxidation states. Fortunately, zircon rare earth element (REE) signatures have been shown to reflect the chemical and isotopic nature of the magma at the time of zircon crystallization, and zircon Ce4+/Ce3+ ratios reflect the oxidation state of the parental magma (e.g. Ballard et al., 2002; Liang et al., 2006; Han et al., 2013; Qiu et al., 2013; Shen et al. 2015). Miocene porphyry Cu-Mo deposits in the Tibetan continental collisional zone are characterized by an adakitic composition (e.g. Hou et al., 2004; Li et al., 2011; Yang et al., 2015a), high oxidation state (e.g. Xiao et al., 2012; Wang et al., 2014), and high magmatic water content (Lu et al., 2015). In addition, they occur in a post-collisional environment (e.g. Hou and Cook, 2009; Qin et al., 2012; Richards, 2015). Recently, more Paleocene-Eocene ore deposits associated with granitic stocks have been reported in the Gangdese Metallogenic Belt (e.g. Zhao et al., 2012; Yang et al., 2015b; Zheng et al., 2015) (Figure 1). This belt primarily hosts collision-related deposits associated with Tibetan tectonic evolution (Hou and Cook, 2009; Qin et al., 2012). Previous studies have compared the magma oxidation state of causative porphyries between the Paleocene-Eocene and Miocene deposits (Wang et al., 2014; Zheng et al., 2015; Sun et 4

al., 2016). However, because the intrusions in the Yaguila-Sharang district record magmatism from ~65 Ma to 50 Ma (Gao et al., 2011, 2015; Zhao et al., 2014, 2015), establishing the relative oxidation state of intrusions in this area would add important constraints to district-scale studies of magmatic sources during the main period of India-Asia continent-continent collision (Hou and Cook, 2009). This study concerns with two adjacent deposits (Figure 1): The Paleocene Yaguila skarn Pb-Zn-Ag-(Mo) deposit contains 10.5 Mt ore at an average grade of 4.25% Pb, 2.15% Zn, and 95.35 g/t Ag (Geological Survey Bureau of Henan, 2009) and the Eocene Sharang porphyry Mo deposit contains 0.63 Mt metal molybdenum with an average grade of 0.061% (No. 6 Geologic Exploration Team of Geological Survey Bureau of Tibet, China, 2009). Given the previous geochronologic and geochemical studies of the Sharang intrusions (Zhao et al., 2012; 2014) and the Yaguila causative porphyry (Gao et al., 2015), we present new geochemical and Sr-Nd-Hf isotopic composition data for magmatic rocks from the Yaguila deposits. We examine zircon Ce and Eu anomalies in the Paleocene-Eocene intrusions from the Yaguila and Sharang deposits, including both mineralized and barren intrusions. These data are combined to elucidate the petrogenesis and oxidation state of Paleocene-Eocene mineralizing magmas during this key period of India-Asian continent-continent collision.

2. Regional and deposit geology The Lhasa terrane can be divided into the southern, central and northern 5

subterranes, bounded by the Shiquanhe-Nam Tso Mélange Zone (SNMZ) and Luobadui-Milashan Fault (LMF) (Figure 1). In the southern Lhasa subterrane, the east-west-trending

Gangdese

batholith

mainly

consists

of

extensive

Jurassic-Cretaceous Andean-type arc magmatism and Paleocene-Eocene felsic magmatic activity (Coulon et al., 1986; Harris et al., 1990; Chung et al., 2003; Wu et al., 2010). Most reported porphyry Cu-Mo deposits are hosted in Miocene adakitic dike swarms or stocks, crosscutting or intruding the Gangdese batholith and meta-sedimentary formations in the southern Lhasa subterrane (Chung et al., 2003). These formed since the Early Miocene, during post-collisional extension (Hou et al., 2004). In the northern subterrane, Mesozoic volcanic rocks occur within the Lower Cretaceous volcano-sedimentary sequence (Pan et al., 2012), and Cretaceous plutonic rocks intrude the Jurassic-Cretaceous sedimentary sequences (Xu et al., 1985). It is still unclear as to whether this subduction-related magmatism is associated with southward Bangong-Nujiang oceanic subduction (e.g. Zhu et al., 2009) or northward Neo-Tethyan oceanic subduction (e.g. Zhang et al., 2012). Porphyry-type or skarn-type deposits associated with extensive intermediate-felsic volcanism and magmatism in the north are rarely reported. In the central Lhasa subterrane, Carboniferous-Permian

meta-sedimentary

sequences

and

lower

Cretaceous

volcano-sedimentary sequences are intruded by widespread Mesozoic granitoids (~210-90 Ma) with abundant dioritic enclaves (Zhu et al., 2011), Paleocene-Eocene granitoids (Ji et al., 2009) and volcanic rocks of the Linzizong Volcanic Succession (Mo et al., 2007). Most intrusions associated with porphyry-type and skarn-type 6

deposits belong to I-type granitoids (e.g. Hou and Cook, 2009; Zhao et al., 2012; Yang et al., 2015b; Zheng et al., 2015), and some are associted with S-type granite or Linzizong rhyolitic stocks, such as the Chagele skarn Cu-Pb-Zn deposit (Gao et al., 2012) and Narusongduo skarn Pb-Zn deposit (Ji et al., 2012). Both the Yaguila and Sharang deposits lie in the north of the eastern section of the Gangdese Metallogenic Belt (Figure 1). Regional stratigraphy includes (from oldest to youngest): 1) Pre-Ordovician Songduo Formation of metamorphic calcareous siltstones and schists; 2) Upper Cretaceous-Lower Permian Laigu Formation of epicontinental clastic carbonate sediments (the host rocks of the Yaguila deposit); 3) Upper Permian Luobadui Formation of carbonate sediments with interlayers of intermediate-mafic volcanics; and 4) Upper Permian Mengla Formation with siliceous detrital rocks (the host rocks of the Sharang deposit). The contacts of these strata units are northeast- and east-striking fault systems, and these strata are unconformably overlain by Cretaceous rhyolitic pyroclastic rocks and the andesite-dacite-rhyolite of the Eocene Pana Formation. They are intruded by multi-stage Jurassic to Miocene intrusions. The chronologic sequences of volcanic and intrusive rocks in the Yaguila and Sharang deposit have been defined in previous studies (Table 1, Gao et al., 2011, 2015; Zhao et al., 2014, 2015; Zheng et al., 2015).

2.1 Yaguila skarn Pb-Zn-Ag (-Mo) deposit

The primary ore occurrences in the Yaguila skarn deposit, including ten Pb-Zn orebodies and one Mo orebody (Geological Survey Bureau of Henan, 2009), are 7

hosted in the NW dipping Upper Carboniferous-Lower Permian Laigu Formation (C2P1l), a 2500 m thick sequence of clastic and carbonate sedimentary rocks comprised of 3 lithological subunits (Figure 2). The lowermost, Unit 1 (C2P1l1), exposed in the south part of the deposit, is a sequence of sandy slate with minor hornfels beds greater than 300 m thick. Unit 2 (C2P1l2) is the main ore host rock with a thickness on the order of 1200 m, and is composed of metamorphosed quartz-rich sandstone interbedded with discontinuous lenses of marble ranging in thickness from 7 to 35 m. This unit conformably transitions into the overlying 840-m-thick unit 3 (C2P1l3), which consists of sandy slate, meta-quartz sandstone, shale and hornfels (Geological Survey Bureau of Henan, 2009). Skarn mineralization extends beyond the Laigu Formation into the overlying felsic volcanic layers (Figure 2 and 3A). The emplacement of the deep Mo-mineralization-related granite porphyry (molybdenite Re-Os age of 65 Ma, Gao et al., 2011; zircon U-Pb ages of 69-66 Ma, Gao et al., 2015; Zhao et al., 2015) was controlled by a reverse, northeast-striking, northwest-dipping fault (F1) in Unit 2 of the Laigu Formation (C2P1l2). The F1 fault contains minor Mo mineralization associated with silicic alteration of the adjacent wall rocks. Smaller-scale F2 and F3 faults, generally parallel to F1, are recognized in the dolomite unit of the Laigu Formation and are the hosts of Pb-Zn mineralization (two orebodies in the southern part of the deposit, shown in Figure 2). Four types of igneous rocks have been recognized at Yaguila (Gao et al., 2015; Zhao et al., 2015; Figure 2): rhyolitic volcanic rocks (135-128 Ma), granite porphyry (69-66 Ma), porphyritic biotite granite (61 Ma) and granodiorite porphyry (18 Ma). 8

Rhyolitic volcanic rocks (exposed area: ~2.5 km2) are volumetrically the most abundant igneous rocks, comprising anhedral phenocrysts of quartz (~10-15 vol%) and K-feldspar (~3-5 vol%) along with minor zircon and apatite in a cryptocrystalline groundmass. The stock of granite porphyry (Figure 5) is a medium-grained porphyry with phenocrysts of plagioclase (~10-15 vol%, 0.3-2 mm), K-feldspar (~3-5 vol%, 0.8-3 mm), quartz (~2-4 vol%, 0.5-1.5 mm) and minor biotite (~1 vol%). Sericitisation and Mo stockwork mineralization are concentrated along the contact zone between granite porphyry and rhyolitic volcanic rocks (Figure 3A). Porphyritic biotite granite intrudes the Laigu Formation and rhyolitic volcanic rocks in the north and west of the Yaguila deposit. Rare Pb-Zn-Mo mineralization has been found in the stocks, and no contact relationship has been found between porphyritic biotite granite and granite porphyry. The porphyritic biotite granite contains euhedral to subhedral plagioclase (~30-35 vol%), K-feldspar (~25-30 vol%), quartz (~20-25 vol%) and biotite (5-8 vol%) with accessory minerals of zircon, apatite and magnetite. Finally, northeast-striking Miocene dykes of granodiorite porphyry (containing phenocrysts of plagioclase, biotite, amphibole, K-feldspar and trace quartz) cross-cut all other igneous rocks and skarn mineralization at Yaguila. Sericitic and chlorite-epidote wall-rock alteration is associated with vein-type Mo mineralization. Sulfide minerals are mainly molybdenite with minor pyrite and sphalerite. The alteration of the skarn-type Pb-Zn mineralization is mainly characterized by grossular-andradite garnet, pyroxene, and wollastonite. The dominant retrograde assemblages are quartz+calcite+chlorite+epidote+actinolite, 9

typically accompanied by sulfide minerals such as pyrrhotite, pyrite and chalcopyrite. Sphalerite and galena typically occur with quartz and/or calcite ± chlorite±epidote as disseminations or veinlets in the skarns. Although no geochronological data for Yaguila Pb-Zn mineralization has been published, several lines of evidence indicate a close relationship between the Mo-mineralized granite porphyry and skarn-type Pb-Zn mineralization: 1) The granite porphyry intrudes into strata altered to hornfels (quartz + molybdenite ± calcite ± sericite veins in chlorite halos), and the intrusion causes chlorite-epidote alteration overprinting at the contacts (Figure 3A-B and photograph in Figure 4D in Zhao et al. (2015)); 2) The sulfide assemblage of molybdenite, sphalerite and galena can be found both in the retrograde skarns (molybdenite + pyrite + galena + pyrrhotite, Figure 3C) and in quartz+molybdenite+sphalerite veinlets (Figure 3D); 3) The Zn and Mo ore grades are consistently high in the Mo orebody (such as in drillhole ZK309 and adit PD401, Geological Survey Bureau of Henan, 2009); 4) The oxygen isotope composition of fluids related to Mo mineralization (-0.3 to +1.8 ‰, veinlets samples in Mo orebody) and Pb-Zn mineralization (-2.2 to +5.8 ‰, samples covering both skarn- and veinlet-type mineralization from different Pb-Zn orebodies) is controlled by different degrees of meteoric mixing process (Zhao et al. unpublished data).

2.2 Sharang porphyry Mo deposit

Located to the south of the Yaguila deposit, the Sharang porphyry Mo deposit is hosted by granite porphyry, in the southern part of the multiple-intruded Sharang 10

complex, which was emplaced into the Upper Permian Mengla Formation (Figure 4). This bedded formation is composed of siliceous detrital and carbonate rocks, predominately including grey-white metamorphosed quartz sandstone, quartz schist and dolomite. Two SES-S dipping (dip angle: 40°-50°), syn-ore reverse faults and a post-ore SE-dipping normal fault are identified in the area. The Sharang complex comprises three stages of igneous intrusion as defined by contact relationships and petrological, geochemical and geo-and thermochronological features (Figure 5 and 6, Zhao et al., 2012, 2014 and 2015): 1) Pre-ore stage rocks contain quartz monzonite and quartz diorite; 2) Ore-forming rocks (52.9-51.6 Ma, Figure 5, Zhao et al., 2014) consist of granite, porphyritic granite, granite and fine-grain granite porphyries and associated magmatic-hydrothermal breccia pipes, with a mineralizing age of 52.3 Ma (molybdenite Re-Os age, Zhao et al., 2014) and an alteration age of 51.1 Ma (sericite Ar-Ar plateau age, Zhao et al., 2015); 3) Post-ore Miocene intrusions are composed of granodiorite and dacite porphyries and lamprophyre dykes. The ore-related granite porphyry contains phenocrysts of K-feldspar, plagioclase and skeletal quartz in a fine-grained groundmass of quartz, plagioclase, K-feldspar and minor biotite. Porphyritic granite, the central facies of granite porphyry observed in drill cores, has graphic or micrographic intergrowths. Fine-grained granite porphyries, predominantly located in the shallow part of the complex, have a finer porphyritic texture and fewer phenocrysts of quartz and K-feldspar. Geochemical data indicate that Sharang intrusions have a high-K calc-alkalinic to shoshonitic, metaluminous to slightly peraluminous composition (Zhao et al., 2012). They are enriched in large ion 11

lithophile elements, and depleted in high-field strength elements, Nb, Sr, P and Ti. REE patterns show slight enrichments in light REE (LREE) relative to heavy REE (HREE) and weak negative Eu anomalies (Zhao et al., 2012). The Sr-Nd-Hf isotopic signatures of the Sharang ore-forming intrusions indicate that the magma source incorporated a higher proportion of old continental materials (Lhasa terrane basement) than the source of the pre-ore intrusions (Zhao et al., 2012, 2015).

3. Sampling, analytical techniques and results

3.1 Sampling and analytical techniques

The rocks in the Yaguila deposit were extensively altered and the least altered samples were selected for geochemical analyses. The causative porphyry has been extensively studied (Gao et al., 2015; Zheng et al., 2015) and we selected two rhyolitic rocks, a porphyritic biotite granite and a granodiorite porphyry for whole-rock geochemical and Sr-Nd isotopic analysis. Zircon grains from the Paleocene-Eocene intrusions in the Yaguila and Sharang deposits were analyzed for trace elements, and all zircon grains analyzed here for Lu-Hf isotopes have been previously age dated (Zhao et al., 2014, 2015). The Sr-Nd isotope analyses, major elements, trace and REE elements analyses were performed at the State Key Laboratory of Lithospheric Evolution and Key Laboratory of Mineral Resources, respectively, at the Institute of Geology and Geophysics, Chinese Academy of Sciences (IGGCAS). Major elements were 12

determined on a Shimadzu XRF-1500 X-ray fluorescence spectrometer using fused glass disks, with precision better than 5%. Trace element composition was determined by ICP-MS (Finnigan ELEMENT-2) after acid digestion of samples in a Teflon pressure vessel. Analyses of rock standards (GSR-01 and BCR-2) indicate precision and accuracy better than 5% for major elements and 10% for trace elements and REEs. Conventional wet chemistry methods were used to determine FeO content (titration). Sr-Nd isotopes were analyzed on a MAT262 mass spectrometer using procedures described by Chen et al. (2002). All measured fractionation corrected to

146

143

Nd/144Nd and

Nd/144Nd=0.7219 and

During the period of data acquisition, the mean was 0.710256 ±11 (2σ, n=14), the mean

143

87

86

86

Sr/88Sr ratios were

Sr/88Sr=0.1194, respectively.

Sr/86Sr ratio of NBS987 standard

Nd/144Nd ratio of Jndi-1 standard was

0.512111±12 (2σ, n=11). Standard BCR-2 yielded

143

Nd/144Nd = 0.512626±12 (2σ,

n=10), in good agreement with the recommended value of 0.512633 (Raczek et al., 2003) In situ zircon Hf isotopic analyses were performed using an ArF excimer laser ablation system, attached to a Neptune Plus Plasma multi-collector ICP-MS, at IGGCAS. Detailed instrumental settings and analytical techniques can be found in Wu et al. (2006). Ablation spots for Lu-Hf isotopic analysis (50-65 μm spots) were placed overtop of pits previously ablated for U-Pb dating (30-32 μm spots; Zhao et al., 2015). The weighted

176

Hf/177Hf ratio of zircon reference standard GJ-1 (0.282021

±0.000007, 2σ, MSWD=0.8, n=25), in good agreement with the value of 0.282015±0.000019 (2σ, n=25) reported by Elhlou et al. (2006); Mud Tank zircon 13

yielded a weighted

176

Hf/177Hf ratio of 0.282500 ±0.000007 (2σ, MSWD=1.6, n=24),

which agrees with the recommended value of 0.282504±0.000044 (2σ, n=158) (Woodhead and Hergt, 2005). Trace element analysis of zircon was performed by LA-ICP-MS (GeoLas 2005 coupled to an Agilent 7500a), at the State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Wuhan. Detailed operating conditions and data reduction protocols have been described by Liu et al. (2008, 2010a).

Areas

without

mineral

inclusions

and

cracks

(as

indicated

by

cathodoluminescence images) were targeted for analysis with a 40 μm spot and 10 Hz laser repetition rate. Before analysis, the sample surface was cleaned with ethanol to eliminate possible contamination. Each analysis included a background acquisition of approximately 20-30 s (gas blank) followed by 50 s data acquisition. Off-line integration selection, background and drift correction, and quantitative calibration for trace element analyses were performed using ICPMSDataCal (Liu et al., 2008, 2010a). Zircon trace element compositions were calibrated against USGS references glasses (BCR-2G and BIR-1G, preferred elemental concentrations from the GeoReM database, http://georem.mpch-mainz.gwdg.de/) and in-house standards (Liu et al., 2010a).

3.2 Results

3.2.1 Major and trace elements

All analytical results are listed in Table 2, along with results from previous 14

studies. The Yaguila rhyolitic rocks are characterized by 70.6-78.4 wt% SiO2, 13.3-16.6 wt% Al2O3, 0.19-0.38 wt% MgO, and variable contents of K2O (2.71-8.35 wt%), Na2O (0.02-0.12 wt%), CaO (0.02-0.20 wt%), Fe2O3 (0.19-1.02 wt%) and FeO (0.22-1.10 wt%). They are classified as calc-alkaline to shoshonitic (Figure 7) and exhibit similar primitive mantle-normalized patterns, displaying enrichment in large ion lithophile elements (LILE, such as K, Rb, Th) and negative Nb, P, Ba, and Sr anomalies (Figure 8). The volcanic rocks have moderately fractionated REE patterns with a LREE/HREE ratio of 6.19-12.86 and moderately-strong Eu negative anomalies (δEu of 0.32-0.52). These geochemical features are similar to those of ~130 Ma felsic volcanics, such as the Zenong dacite-rhyolite (Zhu et al., 2009; Liu et al., 2010b) and Luozha rhyolite at Namulin (Liu et al., 2012) in the central Lhasa terrane (Figures 7 and 8). The Paleocene causative granite porphyry (66.5-62.6 Ma) has high SiO2 (70.9-77.5 wt%) and high-K calc-alkaline to shoshonitic (4.02-8.66 wt% of K2O) composition (Gao et al., 2015; Zheng et al., 2015). The newly analyzed porphyritic biotite granite (60.9 Ma) has a high-K calc-alkaline composition, with higher Na2O and lower K2O contents than the granite porphyry (Figure 7). Both Yaguila Paleocene intrusions

present

similar

primitive

mantle-normalized

patterns

and

chondrite-normalized REE patterns (Figure 8). The porphyritic biotite granite has a total REE content of 200 ppm, LREE/HREE ratio of 11.9 and a δEu value of 0.61. Although the Miocene granodiorite porphyry has a relatively high loss on ignition (Table 2), it still shows temporal and geochemical similarities to the Sharang Miocene 15

dykes (Figure 8), yielding a higher LREE/HREE ratio of 23.6 and a (La/Yb)N ratio of 37.0.

3.2.2 Sr-Nd-Hf isotopes

The whole-rock initial Sr, Nd and zircon Hf isotopic compositions of the Yaguila volcanic and intrusive rocks are given in Table 2 and Supplementary 1. The Yaguila rhyolitic volcanic rocks (YG09-10 and YGZK309-438) have high Rb/Sr and 87Sr/86Sr ratios, which result in unrealistic initial 87Sr/86Sr ratios. However, both samples have similar

147

Sm/144Nd and

143

Nd/144Nd ratios, and calculated εNd(t)

values of -12.3 and -12.9 with TDM2 ages (two-stage depleted mantle ages) from 1929 to 1976 Ma. The Nd isotopic compositions of the rhyolitic rocks are much more similar to those of the causative granite porphyries (65-63 Ma), which have εNd(t) values from -13.3 to -13.5 and TDM2 ages from 1916 to 1969 Ma (Zheng et al., 2015). The porphyritic biotite granite (YG09-15, 61 Ma) exhibits an initial 87Sr/86Sr ratio of 0.707476 and εNd(t) value of -4.9, with a younger TDM2 of 1268 Ma. The Miocene granodiorite porphyry (YG09-01) has a similar initial

87

Sr/86Sr ratio (0.709630) and

εNd(t) value (-3.1) as the Sharang Miocene dykes (0.705983 to 0.706772 and -0.9 to -3.1, Zhao et al., 2012). The Yaguila Cretaceous rhyolitic volcanic rocks (sample YG309-438 and YG09-10) exhibit low 176Lu/177Hf ratios (<0.002) with 176Hf/177Hf isotopic ratios from 0.282265 to 0.282544, and calculated εHf(t) values from -15.3 to -5.3. Zircons from the causative granite porphyry (PD401-13) yield 16

176

Hf/177Hf isotopic ratios from

0.282602 to 0.282848, and εHf(t) values from -4.7 to 3.6, a similar range to that of zircons measured by Gao et al. (2015). The barren porphyritic biotite granite (YG09-15) has a

176

Hf/177Hf isotopic ratio ranging from 0.282721 to 0.282845

(n=19), and εHf(t) values from -0.6 to 3.8. Zircons from the Miocene granodiorite porphyry (YG09-1) display a range of

176

Hf/177Hf ratios from 0.282794 to 0.282903,

with an average εHf(t) value of 2.7±0.6.

3.2.3 Zircon trace elements

Trace element contents for Yaguila and Sharang zircons are reported in Supplementary 2. All zircon in each sample define a single group in terms of the REE contents and normalized REE patterns (Figure 10). All chondrite-normalized REE patterns are characterized by a steep increase from LaN to LuN with a strong positive Ce-anomaly and negative Eu-anomaly (Figure 10). Crystallization temperatures are estimated using the Ti-in-zircon thermometer from the equations of Ferry and Watson (2007), as follows

Where

and

represent the activities of SiO2 and TiO2. The activity of SiO2

is assumed to be 1 as all the analysed intrusions contain primary magmatic quartz, and the activity of TiO2 is assumed to be 0.7, similar to most felsic melts (e.g. Watson et al., 2006). The calculated results are listed in Supplementary 2 and Figure 11, and are summarized in Table 3. 17

Zircon Ce4+/Ce3+ ratios can be used to estimate magmatic oxidation state (Ballard et al., 2002; Trail et al., 2011; Burnham and Berry, 2012). The calculation of Ce anomalies requires an estimation of Ce3+ from the concentrations of La and Pr, which are extremely low in zircon and close to or below the detection limits of LA-ICP-MS (Supplementary 2). Magmatic oxygen fugacities can be calculated from the Ce anomalies and the Ti-in-zircon thermometer proposed by Trail et al. (2012), as follows

Where

represents the intensity of the Ce

anomaly,

represents the ratio of Ce concentration in zircon and the melt,

and

and

are the partition coefficients for La and Pr. We

use the lattice-strain approach (Blundy and Wood, 1994) to obtain the and

values based on whole-rock and zircon REE

concentrations, and the values of

and

are listed in Supplementary 2 and

Figure 11, and summarized in Table 3. During the calculation, we use the whole-rock composition to represent the composition in the melt component when zircon crystallized. However, the crystallization of LREE-rich minerals before zircon (e.g., apatite and monazite), might lower the LREE contents of the residual melt, making the whole-rock geochemical approach inappropriate (Dilles et al., 2015). In this study, the effect of crystallization of these minerals should be small as the P contents of the igneous rocks in Yaguila and Sharang district are lower than 0.2 wt% (Table 2). 18

Moreover, inclusions (such as apatite and titanite) in zircon grains were carefully avoided during analysis to ensure acquisition of the true REE concentrations in zircon, and P and Ca were selected as the monitor elements. The zircon Eu anomalies (EuN/EuN*) were calculated based on normalized Sm and Gd concentrations. The calculated Eu anomaly values for the Yaguila zircon grains range from 0.15 to 0.38 (Supplementary 2 and Table 3). The EuN/EuN* values for the Sharang pre-ore intrusions are much lower, varying from 0.12 to 0.27 while the values for the Sharang intrusions in the ore-forming stage are high, ranging from 0.40 to 0.61.

4 Discussion

4.1 Origin of the Yaguila volcanic and intrusive rocks

4.1.1 Cretaceous rhyolitic volcanic rocks

The Yaguila Cretaceous rhyolitic volcanics have previously been postulated to represent the products of partial melting of crustal materials from the Lhasa terrane basement (Gao et al., 2015). In this study, both La/Sm-La and La/Yb-La plots of early Cretaceous rhyolitic volcanic rocks in Yaguila, together with other regions in the central Lhasa terrane, suggest that a partial melting process likely controls their generation (Figure 12A and 12B). No other coeval mafic and intermediate volcanic rocks have been found at Yaguila (apart from rhyolite). However, Kang et al. (2008) and Zhu et al. (2009) report that the early Cretaceous Zenong Group (130-110 Ma) in 19

the western section of the central Lhasa terrane is composed of basaltic andesite, andesite and dacite, recognized as the product of melting of mantle wedge beneath the central Lhasa terrane. The Yaguila rhyolite is enriched in LREE, Al and Th (Figure 8), indicating that this high-silica (70.6-78.4 wt% SiO2) volcanic rock may have been generated during re-melting of crustal materials, dehydrated by the heat from the mafic magma (Tepper et al., 1993; Guffanti et al., 1996). In addition, the primitive mantle-normalized spider diagrams (Figure 8A), chondrite-normalized REE patterns (Figure 8B) and Nb/Ta ratios (Figure 12C) of the Yaguila rhyolitic volcanics are more similar to those of the upper crust than the lower crust (Rudnick and Gao, 2003). Furthermore, our Nd-Hf isotopic results yield negative εNd(t) values (-12.9 to -12.3), negative zircon εHf(t) values (-15.3 to -5.3) and ancient TDMC ages (~1.7 to ~2.1 Ga), indicating that these rock were derived from melting of ancient continental crust, similar to the early Cretaceous volcanic rocks (Figure 9A and 9B) in the central Lhasa terrane (Zhu et al., 2009).

4.1.2 Paleocene granite porphyry and porphyritic biotite granite

The Yaguila Paleocene granite porphyry and porphyritic biotite granite show an enrichment in LREE and LILE, and pronounced depletions in Ba, Sr, Nb and Ta, suggesting an “arc-like” signature similar to the Sharang ore-forming intrusions (Zhao et al., 2012), Linzizong Volcanic Succession (Mo et al., 2007) and coeval Paleocene-Eocene Gangdese granitoids (Ji et al., 2009). The depletion in Nb and Ta might result from the separation of Ti-bearing phases (such as ilmenite and titanite) in 20

the magma source (Rollinson, 1993) and the Eu depletion requires extensive fractionation of plagioclase and/or K-feldspar in the magma chamber. All these features indicate that the residual mineral assemblages in the source of the Yaguila Paleocene intrusions would be hornblende+plagioclase+Ti-bearing phases. Moreover, we model the process of fractionation crystallization of the main rock-forming minerals for Yaguila Paleocene intrusions and Sharang Paleocene-Eocene intrusions using Sr vs. Ba (Figure 13A) and Sr vs. Rb diagrams (Figure 13B). The model reveals that strong fractional crystallization of plagioclase and K-feldspar occurred during the formation of the Yaguila granite porphyry, and suggest a higher degree of crystal fractionation for the Yaguila granite porphyry than for the Sharang ore-forming intrusions. Additionally, the Yaguila granite porphyry yielded a similar Nd isotopic composition to the Cretaceous volcanics (Figure 9A). The wide range of zircon εHf(t) values (-4.7 to 3.6 in this study, and -13.9 to 3.6 if all published data is considered; Figure 9B) indicates complex interaction between mantle-derived and crustal-derived materials when continental collision initiated (70-55 Ma, Yin and Harrison, 2000; DeCelles et al., 2014; Wu et al., 2014). Moreover, the dramatic increase in εNd(t) values from the granite porphyry to the porphyritic biotite granite (Figure 9A), suggests that more mantle material was incorporated at the time of crystallisation of the barren stock (at ~60 Ma).

21

4.1.3 Miocene dykes in the district

As post-ore intrusions, the Miocene Yaguila granodiorite porphyry, and Sharang lamprophyre, dacite porphyry and granodiorite porphyry were emplaced in the short timespan from 22 to 18 Ma (Zhao et al., 2014, 2015). They can be characterized as ultrapotassic (K2O>3.0 wt%, Na2O>3.0 wt%, K2O/Na2O>2, MgO>3.0 wt%, Foley et al., 1987) or adakitic according to their geochemical features (Figure 14A and 14B), suggesting the district-scale existence of coeval ultrapotassic and adakaitic magmatism. All the Miocene rocks in the district show similar primitive mantle-normalized spider diagrams and chondrite-normalized REE patterns (Figure 8), and display enriched Sr-Nd isotopic compositions (Figure 9A and 14C) and positive zircon εHf(t) values (Figure 9B). This suggests they may be derived from a similar magma source. Regionally, post-collisional Miocene potassic-ultrapotassic rocks distributed in the western-central section of the Lhasa terrane were emplaced from ~25 to 10 Ma (e.g. Turner et al., 1996; Zhao et al., 2001; Guo et al., 2007). Miocene adakitic lavas were distributed across the Lhasa terrane (~25-10 Ma, Chung et al, 2003), and some adakitic dykes or stocks are related to Miocene porphyry Cu-Mo deposits (e.g. Hou et al., 2004). Searle et al. (2011) suggested that the coeval Miocene ultrapotassic rocks and adakites could have originated from a hot, enriched mantle lithosphere and a garnet-bearing eclogitic lower crust (at ~30-10 Ma; Chung et al., 2003, 2009; Guo et al., 2007). As these rocks also have distinct Sr-Nd isotopic compositions (Figure 14C), we propose that the Miocene magmatism in the Yaguila-Sharang district might be derived from the partial melting of enriched mantle 22

lithosphere, triggered by the upwelling of asthenospheric melt.

4.2 Preferential input of mantle material to the magma source

The importance of a mantle contribution to crustal growth of the southern Lhasa subterrane since the Mesozoic, in association with Neo-Tethyan oceanic subduction and the India-Asia continental collision, has been emphasized by previous studies (e.g. Chung et al., 2005, Ji et al., 2009; Mo et al., 2007; Wu et al., 2010). In this study, the proportional contribution of crustal and mantle materials, as indicated by Nd-Hf isotopic mixing calculations (Figure 15A and 15B), clearly shows that more mantle material was incorporated into the intrusive sequences from Paleocene to Eocene in the Yaguila-Sharang district. This provides a district-scale representation of the evolution of the Gangdese ore-forming intrusions during the main period of India-Asia continental collision. In the initial stage of continental collision (70-60 Ma), Pb-Zn deposits in central Lhasa (coeval with the Yaguila deposit), were related to syn-collisional granites or S-type granites (Figure 1), generated during crustal re-melting with only limited mantle material added to the magma source (Wang et al., 2012; Gao et al., 2015; Zheng et al., 2015). As subduction-type magmatism continued, mineralization in the southern Lhasa terrane (andesite-related vein-type Au-Ag deposits; Huang et al., 2013; Gangdese I-type granitoids, such as skarn Mo and Fe deposits, Li et al., 2011; Huang et al., 2013) was accompanied by emplacement of the Linzizong volcanic succession. The collision process continued from 60-50 Ma and most mineralization occurred 23

within I-type granitoids in both the central (e.g. Sharang porphyry Mo deposit) and southern Lhasa terrane (e.g. Jiru porphyry Cu-Mo deposit), related to Neo-Tethyan oceanic slab roll-back and break-off (Hou and Cook, 2009; Zhao et al., 2012; Yang et al., 2015b). Our Nd-Hf isotopic mixing model (Figure 15A and 15B) reveals a higher influx of mantle material into the fertile magma source during this interval, which can be explained by the current model of Neo-Tethyan oceanic slab roll-back and break-off (Zhao et al., 2014; Wang et al., 2015). The present work also provides support for this tectonic model on a district scale, and further enhances the tectonic model indicated by previous regional studies (e.g. Chung et al., 2005; Hou and Cook, 2009).

4.3 Magma oxidation state

Zircons from the Paleocene-Eocene intrusions are characterized by positive Ce and negative Eu anomalies. Ce and Eu occur in multiple valence states (Ce as Ce 3+ and Ce4+, Eu as Eu2+ and Eu3+) in magmatic environments and partition differently into zircon depending on magma oxidation state (e.g. Ballard et al., 2002; Trail et al., 2012). Zircon Ce anomalies and magma oxidation state: Causative porphyries and intrusions in both deposits are clearly characterized by higher Ce anomalies (denoted as (Ce/Ce*)D) than barren or pre-ore stocks (Figure 16). However, zircon (Ce/Ce*)D ratios are affected by oxygen fugacity, melt composition and the temperature at which zircon crystallized (Trail et al., 2012), based on experimental granitic melt 24

compositions with different atomic ratios of Al/(Na+K) (ASI values of 0.50, 0.85 and 1.25). In this study, we set the oxygen fugacity buffer according to experimental results at ASI=1.25 (Figure 16) and plot the zircon (Ce/Ce*)D values of the studied samples against calculated Ti-in-zircon temperatures (Figure 16). All the data plot above the Ni-NiO buffer (NNO). The Yaguila barren stock compositions scatter between the magnetite-hematite (MH) and NNO buffers, but at similar crystallization temperatures, while the zircon (Ce/Ce*)D values of the granite porphyry plot above the MH buffer. For Sharang, most pre-ore and pre-forming intrusions plot between the NNO and MH buffers. Metals and sulfur can be directly derived through fractional crystallization and partitioning of Mo into exsolved aqueous magmatic-hydrothermal fluids in porphyry Mo systems (Candela and Bouton, 1990; Audétat an Pettke, 2003; Mustard et al., 2006; Audétat, 2010; Bali et al., 2012). During differentiation, the oxygen fugacity of a magma increases (Czamanske and Wones, 1973), which facilitates much higher solubility of sulfate (S6+) relative to sulfide (S2-) (Carroll and Rutherford, 1988), and more efficient extraction of Mo into the melts, resulting in a higher Mo concentration in the hydrous silicic melt (Audétat, et al., 2011). This is supported by our results in that both the Yaguila granite porphyry and porphyritic biotite granite are highly differentiated (Figure 13), but the oxygen fugacity of the Mo mineralizing magma is much higher than that of the barren granite (Figure 16). For Sharang Eocene calc-alkalinic magmatism, fractional crystallization processes might control the evolution of multiple intrusions (Zhao et al., 2012; this study), which resulted in the 25

fO2 of the granitic intrusions in the ore-forming stage being higher than that of the pre-ore quartz monzonite and quartz diorite (Figure 16). Therefore, both the Yaguila and Sharang Mo mineralization are closely related to highly oxidized and differentiated magma. Zircon EuN/EuN* ratios: Zircon grains from the Paleocene-Eocene granitiods show moderately negative Eu anomalies and the Sharang pre-ore intrusions show strongly negative Eu anomalies (Figure 10, 11B and 11C). The EuN/EuN* ratios in zircon can be also be regarded as a measure of the magma oxidation state, and a clear increase of the EuN/EuN* ratios along Sharang intrusive sequence is observed in this study. The negative Eu anomalies in zircons can result from the early crystallization of plagioclase in the magma reservoir when crystallization of the early pre-ore intrusions began. This explanation is consistent with decreasing negative δEu values and CaO contents in the whole-rock compositions along the Sharang intrusive sequences (Zhao et al., 2012). Early plagioclase crystallization may also explain the whole-rock geochemistry of Yaguila Paleocene intrusions where strongly negative Eu anomalies are noted in the Yaguila granite porphyry and barren porphyritic biotite granite (Figure 8), accompanied by a high degree of plagioclase fractionation (Figure 13). However, the variation of EuN/EuN* values in zircons can be also accounted for by processes other than plagioclase fractionation. Dilles et al. (2015) proposed that SO2 degassing from magmas with a relatively low Fe/S ratio can also account for small negative Eu anomalies (mostly EuN/EuN* >0.4), and that mineralizing intrusions contained higher variable EuN/EuN* than those in earlier non-mineralized intrusions 26

from the same magmatic suite. Fertile intrusions in the Yaguila-Sharang district contain EuN/EuN* values from 0.3 to 0.6, higher than the non-mineralized intrusions which supports the Dilles et al. (2015) observation. Plagioclase-bearing rocks have not yet been found in the stratigraphy of the district but the possibility of assimilation of plagioclase-bearing rocks (Ballard et al., 2002) cannot be completely excluded.

5 Conclusions Based on new elemental and isotopic data for the Yaguila deposit, we conclude that: 

Cretaceous rhyolitic rocks were formed by the melting of ancient continental crust;



The Paleocene causative granite porphyry likely originated from the interaction between mantle-derived and crustal-derived materials when India-Asia continental collision was initiated;



The post-ore Paleocene barren porphyritic biotite granite resulted from a higher influx of mantle material into the magma source;



The post-ore Miocene granodiorite porphyry might have been generated from melting of enriched lithospheric mantle given that these samples have a similar geochemical, enriched Nd isotopic and depleted Hf isotopic composition to the Sharang Miocene dykes.

Mixing calculations using Nd-Hf isotopic data show an increasing contribution of mantle material from Paleocene to Eocene intrusions in the Yaguila-Sharang 27

district, consistent with the regional tectonic model of Neo-Tethyan oceanic slab roll-back and break-off. Zircon trace elements reveal that both the Yaguila and Sharang ore-related porphyries have higher Ce anomalies than barren granitoids, suggesting that Mo mineralization is closely related to highly oxidized and differentiated magma. The fertile intrusions in the Yaguila-Sharang district have EuN/EuN* values from 0.3 to 0.6, higher than the non-mineralized intrusions. The process of early crystallization of plagioclase and/or SO2-degassing from underlying magmas can explain the observed Eu negative anomalies in zircon.

Acknowledgements This study is granted by NSFC (No.41402080), General Financial Grant from the China Postdoctoral Science Foundation (2014M550836), the 2014 State Scholarship Fund by CSC (first author) and Strategic Priority Research Program of the Chinese Academy of Sciences (Grant number XDB03010303). The authors would like to extend their gratitude to Drs. Zhuyin Chu, Chaofeng Li and Dingshuai Xue for their assistance in whole-rock geochemistry and Sr-Nd isotope analyses, to Prof. Zhaochu Hu with their help in the analysis of zircon trace elements, to Dr. Yi Hu, Dr. Luying Jin and Dr. Yanbo Cheng for the useful discussion and comments, and to Academician Ji Duo, Senior geologists Dengkui Su, Gang Yan of Tibet Bureau of Geology and Exploration for the support of the field work. We are grateful to editor-in-chief Prof. Mei-Fu Zhou, associated editor Dr. Derek Wyman, Dr. 28

Chengbiao Leng and two anonymous reviewers, for insightful and constructive reviews of the manuscript.

References Audétat, A., 2010. Source and evolution of molybdenum in the porphyry Mo (–Nb) deposit at Cave Peak, Texas. J. Petrol. 51, 1739-1760. Audétat, A., Dolejš, D., Lowenstern, J.B., 2011. Molybdenite saturation in silicic magmas: occurrence and petrological implications. J. Petrol. 52, 891-904. Audétat, A., Pettke, T., 2003. The magmatic-hydrothermal evolution of two barren granites: a melt and fluid inclusion study of the Rito del Medio and Canada Pinabete plutons in northern New Mexico (USA). Geochim. Cosmochim. Acta. 67, 97-121. Bali, E., Keppler, H., Audetat, A., 2012. The mobility of W and Mo in subduction zone fluids and the Mo–W–Th–U systematics of island arc magmas. Earth Planet. Sci. Lett. 351, 195-207. Ballard, J., Palin, M., Campbell, I., 2002. Relative oxidation states of magmas inferred from Ce(IV)/Ce(III) in zircon: application to porphyry copper deposits of northern Chile. Contrib. Miner. Petrol. 144, 347-364. Barth, M. G., William, F., McDonough, W. F., Rudnick, R. L., 2000. Tracking the budget of Nb and Ta in the continental crust. Chem. Geol. 165, 197-213. Blundy, J., Wood, B., 1994. Prediction of crystal-melt partition coefficients from elastic moduli. Nature 372, 452-454. 29

Burnham, A.D., Berry, A.J., 2012. An experimental study of trace element partitioning between zircon and melt as a function of oxygen fugacity. Geochim. Cosmochim. Acta. 95, 196-212. Candela, P.A., Bouton, S.L., 1990. The influence of oxygen fugacity on tungsten and molybdenum partitioning between silicate melts and ilmenite. Econ. Geol. 85, 633-640. Carroll, M., Rutherford, M.J., 1988. Sulfur speciation in hydrous experimental glasses of varying oxidation state--results from measured wavelength shifts of sulfur X-rays. Am. Mineral. 73, 845-849. Chen, F., Satir, M., Ji, J., Zhong, D., 2002. Nd–Sr–Pb isotopes of Tengchong Cenozoic volcanic rocks from western Yunnan, China: evidence for an enriched-mantle source. J. Asian Earth Sci. 21, 39-45. Chung, S.-L., Chu, M.-F., Ji, J., O'Reilly, S.Y., Pearson, N.J., Liu, D., Lee, T.-Y.m Lo, C.-H., 2009. The nature and timing of crustal thickening in Southern Tibet: Geochemical and zircon Hf isotopic constraints from postcollisional adakites. Tectonophysics 477(1-2), 36-48. Chung, S.-L., Chu, M.-F., Zhang, Y., Xie, Y., Lo, C.-H., Lee, T.-Y., Lan, C.-Y., Li, X., Zhang, Q., Wang, Y., 2005. Tibetan tectonic evolution inferred from spatial and temporal variations in post-collisional magmatism. Earth Sci. Rev. 68, 173-196. Chung, S.-L., Liu, D.-Y., Ji, J.-Q., Chu, M.-F., Lee, H.-Y., Wen, D.-J., Lo, C.-H., Lee, T.-Y., Qian, Q., Zhang, Q., 2003. Adakites from continental collision zones: Melting of thickened lower crust beneath southern Tibet. Geology 31, 30

1021-1024. Cooke, D.R., Hollings, P., Walshe, J.L., 2005. Giant porphyry deposits: characteristics, distribution, and tectonic controls. Econ. Geol. 100, 801-818. Coulon, C., Maluski, H., Bollinger, C., Wang, S., 1986. Mesozoic and Cenozoic volcanic rocks from central and southern Tibet: 39 Ar-40 Ar dating, petrological characteristics and geodynamical significance. Earth Planet. Sci. Lett. 79, 281-302. Czamanske, G.K., Wones, D.R., 1973. Oxidation During Magmatic Differentiation, Finnmarka Complex, Oslo Area, Norway: Part 2, The Mafic Silicates1. J. Petrol. 14, 349-380. DeCelles, P.G., Kapp, P., Gehrels, G.E., Ding, L., 2014. Paleocene-Eocene foreland basin evolution in the Himalaya of southern Tibet and Nepal: Implications for the age of initial India-Asia collision. Tectonics 33, 824-849. Dilles, J.H., Kent, A.J., Wooden, J.L., Tosdal, R.M., Koleszar, A., Lee, R.G., Farmer, L.P., 2015. Zircon compositional evidence for sulfur-degassing from ore-forming arc magmas. Econ. Geol. 110, 241-251. Elhlou, S., Belousova, E., Griffin, W., Pearson, N., O’Reilly, S.Y., 2006. Trace element and isotopic composition of GJ-red zircon standard by laser ablation. Geochim. Cosmochim. Acta. 70, A158. Ferry, J., Watson, E., 2007. New thermodynamic models and revised calibrations for the Ti-in-zircon and Zr-in-rutile thermometers. Contrib. Miner. Petrol. 154, 429-437. 31

Foley, S. F., Venturelli, G., Green, D. H., Toscani, L., 1987. The ultrapotassic rocks: characteristics, classification,and constraints for petrogenetic models. Earth Sci. Rev. 24, 81-134. Gao. S.B., Zheng, Y.Y., Tian, L.M., Zhang, Z., Qu, W.J., Liu, M.Y., Zheng, H. T., Zheng, L., Zhu, J.H., 2012. Geochronology of magmatic intrusions and mineralization of Chagele copper-lead-zinc deposit in Tibet and its implications. Earth Sci.: J. China U. Geosci. 37, 507-514 (in Chinese with English abstract). Gao, Y.M., 2010. Regional metallogenic rule and geological characteristics of Yaguila-Sharang mineralization concentration area. Chinese Academy of Geological Sciences Ph.D. Thesis 1-157 (in Chinese with English abstract). Gao, Y.M., Chen, Y.C., Tang, J.X., Li, C., Li, X.F., Gao, M., Cai, Z.C. 2011. Re-Os dating of molybdenite from the Yaguila porphyry molybdenum deposit in Gongbo’gyamda area, Tibet and its geological implications. Geol. Bull. China 30, 1027-1036 (in Chinese with English abstract). Gao, Y.M., Lan, Z.W., Chen, Y.C., Tang, J.X., 2015. Geochronological and geochemical constraints on the origin of Yaguila Cretaceous and Palaeogene ore-bearing quartz porphyries, Central Lhasa Terrane, Tibet. Geol. J. doi: 10.1002/gj.2731. Geological Survey Bureau of Henan, China, 2009. Detailed survey report of Yaguila Pb-Zn deposit in country of Gongbujiangda, Tibet. Exploration report 1-136 (in Chinese). Griffin, W., Pearson, N., Belousova, E., Jackson, S., Van Achterbergh, E., O’Reilly, 32

S.Y., Shee, S., 2000. The Hf isotope composition of cratonic mantle: LAM-MC-ICPMS analysis of zircon megacrysts in kimberlites. Geochim. Cosmochim. Acta. 64, 133-147. Guffanti, M., Clynne, M.A., Muffler, L., 1996. Thermal and mass implications of magmatic evolution in the Lassen volcanic region, California, and minimum constraints on basalt influx to the lower crust. J. Geophys. Res. 101, 3003-3013. Guo, Z., Wilson, M., Liu, J., 2007. Post-collisional adakites in south Tibet: products of partial melting of subduction-modified lower crust. Lithos 96, 205-224. Han, Y., Zhang, S., Pirajno, F., Zhou, X., Zhao, G., Qü, W., Liu, S., Zhang, J., Liang, H., Yang, K., 2013. U–Pb and Re–Os isotopic systematics and zircon Ce 4+/Ce 3+ ratios in the Shiyaogou Mo deposit in eastern Qinling, central China: insights into the oxidation state of granitoids and Mo (Au) mineralization. Ore Geol. Rev. 55, 29-47. Hou, Z.Q., Cook, N.J., 2009. Metallogenesis of the Tibetan collisional orogen: A review and introduction to the special issue. Ore Geol. Rev. 36, 2-24. Hou, Z.Q., Gao, Y.F., Qu, X.M., Rui, Z.Y., Mo, X.X., 2004. Origin of adakitic intrusives generated during mid-Miocene east-west extension in southern Tibet. Earth Planet. Sci. Lett. 220, 139-155. Huang, W., Liang, H., Wu, J., Wang, C., Zou, Y., Wang, X., Xu, J., Charllote, M.A., 2013. Study on the metallogenesis during the early stage of continental collision in southern Gangdese, Tibet. Acta Petrol. Sin. 29, 1439-1449 (in Chinese with English Abstract). 33

Ji, X.H., Yang, Z.S., Yu, Y.S., Shen, J.F., Tian, S.H., Meng, X.J., Li, Z.Q., Liu, Y.C., 2012.Formation mechanism of magmatic rocks in Narusongduo lead-zinc deposit of Tibet: Evidence from magmatic zircon. Miner. Depos. 31, 758-774 (in Chinese with English abstract). Ji, W.Q., Wu, F.Y., Chung, S.L., Li, J.X., Liu, C.Z., 2009. Zircon U-Pb geochronology and Hf isotopic constraints on petrogenesis of the Gangdese batholith, southern Tibet. Chem. Geol. 262, 229-245. Kang, Z.Q., Xu, J.F., Dong, Y.H., Wang, B.D., 2008. Cretaceous volcanic rocks of Zenong Group in north-middle Lhasa block: products of southward subducting of the Slainajap ocean? Acta Petrol. Sin. 24, 303-314 (in Chinese with English abstract). Le Bas, M.J., Le Maitre, R., Streckeisen, A., Zanettin, B., 1986. A chemical classification of volcanic rocks based on the total alkali-silica diagram. J. Petrol. 27, 745-750. Li, J., Qin, K., Li, G., Xiao, B., Chen, L., Zhao, J., 2011. Post-collisional ore-bearing adakitic porphyries from Gangdese porphyry copper belt, southern Tibet: Melting of thickened juvenile arc lower crust. Lithos 126, 265-277. Li, Y., Xie, Y., Chen, W., Tang, Y., Li, G., Zhang, L., Liu, Y., Liu, X., 2011. U-Pb age and geochemical characteristics of zircon in monzogranite porphyry from Qiagong deposit, Tibet, and geological implication. Acta Petrol. Sin. 27, 2023-2033 (in Chinese with English abstract). Liang, H.-Y., Campbell, I.H., Allen, C., Sun, W.-D., Liu, C.-Q., Yu, H.-X., Xie, Y.-W., 34

Zhang, Y.-Q., 2006. Zircon Ce4+/Ce3+ ratios and ages for Yulong ore-bearing porphyries in eastern Tibet. Miner. Deposita 41, 152-159. Liu, W., Li, F.Q., Yang, X.Y., Yuan, S.H., 2012. Zircon U-Pb age and geochemistry of early Cretaceous rhyolite in Luozha area of Namling County, Tibet. Geol. China 39, 1151-1161 (in Chinese with English abstract). Liu, W., Li, F.Q., Yuan, S.H., Zhang, W.P., Zhuo, J.W., Wang, B.D., Tang, W.Q., 2010b. Volcanic rock provenance of Zenong Group in Coqen area of Tibet: geochemistry and Sr-Nd constraint. Acta Petrol. Miner. 29, 367-376 (in Chinese with English abstract). Liu, Y., Hu, Z., Zong, K., Gao, C., Gao, S., Xu, J., Chen, H., 2010a. Reappraisement and refinement of zircon U-Pb isotope and trace element analyses by LA-ICP-MS. Chinese Sci. Bull. 55, 1535-1546. Liu, Y., Hu, Z., Gao, S., Günther, D., Xu, J., Gao, C., Chen, H., 2008. In situ analysis of major and trace elements of anhydrous minerals by LA-ICP-MS without applying an internal standard. Chem. Geol. 257, 34-43. Lu, Y.-J., Loucks, R.R., Fiorentini, M.L., Yang, Z.-M., Hou, Z.-Q., 2015. Fluid flux melting generated postcollisional high Sr/Y copper ore–forming water-rich magmas in Tibet. Geology 43, 583-586. Mišković, A., Schaltegger, U., 2009. Crustal growth along a non-collisional cratonic margin: a Lu-Hf isotopic survey of the Eastern Cordilleran granitoids of Peru. Earth Planet. Sci. Lett. 279, 303-315. Miller, C., Schuster, R., Klotzli, U., Frank, W., Purtscheller, F., 1999. Post-Collisional 35

Potassic and Ultrapotassic Magmatism in SW Tibet: Geochemical and Sr-Nd-Pb-O Isotopic Constraints for Mantle Source Characteristics and Petrogenesis. J. Petrol. 40, 1399-1424. Mo, X., Hou, Z., Niu, Y., Dong, G., Qu, X., Zhao, Z., Yang, Z., 2007. Mantle contributions to crustal thickening during continental collision: Evidence from Cenozoic igneous rocks in southern Tibet. Lithos 96, 225-242. Mustard, R., Ulrich, T., Kamenetsky, V.S., Mernagh, T., 2006. Gold and metal enrichment in natural granitic melts during fractional crystallization. Geology 34, 85-88. No.6 Geologic Exploration Team of Geological Survey Bureau of Tibet, China, 2009. Exploration report of Sharang Mo deposit in Gongbo'gyamda County, Tibet. Exploration report, 1-141 (in Chinese). Othman, D.B., Polvé, M., Allègre, C.J., 1984. Nd-Sr isotopic composition of granulites and constraints on the evolution of the lower continental crust. Nature 307, 510-515. Pan, G.T., Ding, J., Yao, D., and Wang, L., 2004, Geological Map of Qinghai-Xiang (Tibet) Plateau and Adjacent Areas, Chengdu Institute of Geology and Mineral Resources, China Geological Survey: Chengdu, China, Chengdu Cartographic Publishing House, scale 1:1,500,000. Pan, G., Wang, L., Li, R., Yuan, S., Ji, W., Yin, F., Zhang, W., Wang, B., 2012. Tectonic evolution of the Qinghai-Tibet plateau. J. Asian Earth Sci. 53, 3-14. Peccerillo, A., Taylor, S.R., 1976. Geochemistry of Eocene calc-alkaline volcanic 36

rocks from the Kastamonu area, northern Turkey. Contrib. Miner. Petrol. 58, 63-81. Peucat, J., Vidal, P., Bernard-Griffiths, J., Condie, K., 1989. Sr, Nd, and Pb isotopic systematics in the Archean low-to high-grade transition zone of southern India: syn-accretion vs. post-accretion granulites. J. Geol., 537-549. Qin, K., 2012. Thematic Articles “Porphyry Cu-Au-Mo deposits in Tibet and Kazakhstan”. Resour. Geol. 62, 1-3. Qiu, J.-T., Yu, X.-Q., Santosh, M., Zhang, D.-H., Chen, S.-Q., Li, P.-J., 2013. Geochronology and magmatic oxygen fugacity of the Tongcun molybdenum deposit, northwest Zhejiang, SE China. Miner. Deposita 48, 545-556. Raczek, I., Jochum, K.P., Hofmann, A.W., 2003. Neodymium and strontium isotope data for USGS reference materials BCR-1, BCR-2, BHVO-1, BHVO-2, AGV-1, AGV-2, GSP-1, GSP-2 and eight MPI-DING reference glasses. Geostandard. Newslett. 27, 173-179. Richards, J.P., 2015. Tectonic, magmatic, and metallogenic evolution of the Tethyan orogen: From subduction to collision. Ore Geol. Rev. 70, 323-345. Richards, J.P., 2003. Tectono-magmatic precursors for porphyry Cu-(Mo-Au) deposit formation. Econ. Geol. 98, 1515-1533. Rollinson, H.R., 1993 Using geochemical data: evaluation, presentation, interpretation. Longman Scientific Technical, London. 352p. Rudnick, R.L., Gao, S., 2003. Composition of the continental crust. Treatise on Geochemistry 3, 1-64. 37

Searle, M.P., Elliott, J.R., Phillips, R.J., Chung, S.-L., 2011. Crustal-lithospheric structure and continental extrusion of Tibet. J. Geol. Soc. Lond. 168, 633-672. Shen, P., Hattori, K., Pan, H., Jackson, S., Seitmuratova, E., 2015. Oxidation condition and metal fertility of granitic magmas: zircon trace-element data from porphyry Cu deposits in the Central Asian Orogenic Belt. Econ. Geol. 110, 1861-1878. Sillitoe, R.H., 2010. Porphyry copper systems. Econ. Geol. 105, 3-41. Sun, S.-s., McDonough, W.F., 1989. Chemical and isotopic systematics of oceanic basalts: implications for mantle composition and processes. Geol. Soc. Lond. Spec. Publ. 42, 313-345. Sun, X., Zheng, Y., Xu, J., Huang, L.H., Guo, F., Gao, S.B., 2016. Metallogenesis and ore controls of Cenozoic porphyry Mo deposits in the Gangdese belt of southern Tibet. Ore Geol. Rev. dx.doi.org/10.1016/j.oregeorev. 2016.01.009. Taylor, S.R., McLennan, S.M., 1985. The continental crust: its composition and evolution. Blackwell Scientific Pub., 312p. Tepper, J.H., Nelson, B.K., Bergantz, G.W., Irving, A.J., 1993. Petrology of the Chilliwack batholith, North Cascades, Washington: generation of calc-alkaline granitoids by melting of mafic lower crust with variable water fugacity. Contrib. Miner. Petrol. 113, 333-351. Trail, D., Watson, E.B., Tailby, N.D., 2012. Ce and Eu anomalies in zircon as proxies for the oxidation state of magmas. Geochim. Cosmochim. Acta. 97, 70-87. Trail, D., Watson, E.B., Tailby, N.D., 2011. The oxidation state of Hadean magmas 38

and implications for early Earth/'s atmosphere. Nature 480, 79-82. Turner, S., Arnaud, N., Liu, J., Rogers, N., Hawkesworth, C., Harris, N., Kelley, S., Van Calsteren, P., Deng, W., 1996. Post-collision, Shoshonitic Volcanism on the Tibetan Plateau: Implications for Convective Thinning of the Lithosphere and the Source of Ocean Island Basalts. J. Petrol. 37, 45-71. Wang, B.D., Guo, L., Wang, L.Q., Li, B., Huang, H.X., Chen, F.Q., Duan, Z.M., Zeng, Q.G., 2012a. Geochemistry and petrogenesis of the ore-bearing pluton in Chagele depist in the middle of Gangdese Metallogenic Belt. Acta Petrol. Sin. 28, 1647-1662 (in Chinese with English abstract). Wang, R., Richards, J.P., Hou, Z.-Q., An, F., Creaser, R.A., 2015. Zircon U–Pb age and Sr–Nd–Hf–O isotope geochemistry of the Paleocene–Eocene igneous rocks in western Gangdese: evidence for the timing of Neo-Tethyan slab breakoff. Lithos 224, 179-194. Wang, R., Richards, J.P., Hou, Z.-Q., Yang, Z.-M., Gou, Z.-B., DuFrane, S.A., 2014. Increasing magmatic oxidation state from Paleocene to Miocene in the Eastern Gangdese Belt, Tibet: implication for collision-related porphyry Cu-Mo±Au mineralization. Econ. Geol. 109, 1943-1965. Wang, Q., Chung, S.-L., Li, X.-H., Wyman, D., Li, Z.-X., Sun, W.-D., Qiu, H.-N., Liu, Y.-S., Zhu, Y.-T., 2012b. Crustal Melting and Flow beneath Northern Tibet: Evidence from Mid-Miocene to Quaternary Strongly Peraluminous Rhyolites in the Southern Kunlun Range. J. Petrol. 53, 2523-2566. Watson, E., Wark, D., Thomas, J., 2006. Crystallization thermometers for zircon and 39

rutile. Contrib. Miner. Petrol. 151, 413-433. Williams, H.M., Turner, S.P., Pearce, J.A., Kelley, S.P., Harris, N.B.W., 2004. Nature of the Source Regions for Post-collisional, Potassic Magmatism in Southern and Northern Tibet from Geochemical Variations and Inverse Trace Element Modelling. J. Petrol. 45, 555-607. Woodhead, J.D., Hergt, J.M., 2005. A preliminary appraisal of seven natural zircon reference materials for in situ Hf isotope determination. Geostand. Geoanal. Res. 29, 183-195. Wu, F.-Y., Ji, W.-Q., Wang, J.-G., Liu, C.-Z., Chung, S.-L., Clift, P.D., 2014. Zircon U–Pb and Hf isotopic constraints on the onset time of India-Asia collision. Am. J. Sci. 314, 548-579. Wu, F.-Y., Ji, W.-Q., Liu, C.-Z., Chung, S.-L., 2010. Detrital zircon U-Pb and Hf isotopic data from the Xigaze fore-arc basin: Constraints on Transhimalayan magmatic evolution in southern Tibet. Chem. Geol. 271, 13-25. Wu, F.Y., Yang, Y.H., Xie, L.W., Yang, J.H., Xu, P., 2006. Hf isotopic compositions of the standard zircons and baddeleyites used in U–Pb geochronology. Chem. Geol. 234, 105-126. Xiao, B., Qin, K., Li, G., Li, J., Xia, D., Chen, L., Zhao, J., 2012. Highly Oxidized Magma and Fluid Evolution of Miocene Qulong Giant Porphyry Cu-Mo Deposit, Southern Tibet, China. Resour. Geol. 62, 4-18. Xu, R.H., Schärer, U., Allègre, C.J., 1985. Magmatism and metamorphism in the Lhasa block (Tibet): A geochronological study. J. Geol., 41-57. 40

Yang, Z.-M., Lu, Y.-J., Hou, Z.-Q., Chang, Z.-S., 2015a. High-Mg diorite from Qulong in southern Tibet: Implications for the genesis of adakite-like intrusions and associated porphyry Cu deposits in collisional orogens. J. Petrol., egu076. Yang, Z., Hou, Z., Chang, Z., Li, Q., Liu, Y., Qu, H., Sun, M., Xu, B., 2015b. Cospatial Eocene and Miocene granitoids from the Jiru Cu deposit in Tibet: Petrogenesis and implications for the formation of collisional and postcollisional porphyry Cu systems in continental collision zones. Lithos 245, 243–257. Yin, A., Harrison, T.M., 2000. Geologic evolution of the Himalayan-Tibetan orogen. Ann. Rev. Earth Planet. Sci. 28, 211-280. Yu, Y.S., Yang, Z.S., Duo, J., Hou, Z.Q., Tian, S.H., Meng, X.J., Liu, H.F., Zhang, J.S., Wang, H.P., Liu, Y.C., 2011. Age and petrogenesis of magmatic rocks from Jiaduobule skarn Fe-Cu deposit in Tibet: Evidence from zircon SHRIMP U-Pb dating, Hf isotope and REE. Miner. Depos. 30, 420-434 (in Chinese with English abstract). Zhang, K.-J., Zhang, Y.-X., Tang, X.-C., Xia, B., 2012. Late Mesozoic tectonic evolution and growth of the Tibetan plateau prior to the Indo-Asian collision. Earth Sci. Rev. 114, 236-249. Zhao, J., Qin, K., Li, G., Cao, M., Evans, N.J., McInnes, B.I., Li, J., Xiao, B., Chen, L., 2015. The exhumation history of collision-related mineralizing systems in Tibet: Insights from thermal studies of the Sharang and Yaguila deposits, central Lhasa. Ore Geol. Rev. 65, 1043-1061. Zhao, J., Qin, K., Li, G., Li, J., Xiao, B., Chen, L., Yang, Y., Li, C., Liu, Y., 2014. 41

Collision-related genesis of the Sharang porphyry molybdenum deposit, Tibet: evidence from zircon U–Pb ages, Re–Os ages and Lu–Hf isotopes. Ore Geol. Rev. 56, 312-326. Zhao, J., Qin, K., Li, G., Li, J., Xiao, B., Chen, L., 2012. Geochemistry and Petrogenesis of Granitoids at Sharang Eocene Porphyry Mo Deposit in the Main-Stage of India-Asia Continental Collision, Northern Gangdese, Tibet. Resour. Geol. 62, 84-98. Zhao, Z. D., Mo, X. X., Zhang, Z. C., Guo, T. Y., Zhou, S., Dong, G.C. , Wang, Y., 2001. Post-collisional magmatism in Wuyu basin, central Tibet: evidence for recycling of subducted Tethyan oceanic crust. Sci. China Ser. D Earth Sci. 44, 27-34. Zheng, Y., Fu, Q., Hou, Z., Yang, Z., Huang, K., Wu, C., Sun, Q., 2015. Metallogeny of the northeastern Gangdese Pb–Zn–Ag–Fe–Mo–W polymetallic belt in the Lhasa terrane, southern Tibet. Ore Geol. Rev. 70, 510-532. Zheng, Y., Sun, X., Gao, S., Zhao, Z., Zhang, G., Wu, S., You, Z., Li, J., 2014. Multiple mineralization events at the Jiru porphyry copper deposit, southern Tibet: Implications for Eocene and Miocene magma sources and resource potential. J. Asian Earth Sci. 79, 842-857. Zhu, D.C., Zhao, Z.D., Niu, Y., Mo, X.X., Chung, S.L., Hou, Z.Q., Wang, L.Q., Wu, F.Y., 2011. The Lhasa Terrane: Record of a microcontinent and its histories of drift and growth. Earth Planet. Sci. Lett. 301, 241-255. Zhu, D.C., Mo, X.X., Niu, Y., Zhao, Z.D., Wang, L.Q., Liu, Y.S., Wu, F.Y., 2009. 42

Geochemical investigation of Early Cretaceous igneous rocks along an east–west traverse throughout the central Lhasa Terrane, Tibet. Chem. Geol. 268, 298-312.

43

< Figure captions> Figure 1. Simplified regional geological map of the Gangdese belt with major Paleocene-Eocene ore deposits, Mesozoic-Cenozoic intrusions and Cenozoic Linzizong Volcanic Succession, modified from Pan et al. (2004). Three units of the Lhasa terrane (including northern Lhasa subterrane, central Lhasa subterrane and southern Lhasa terrane) have been separated by the SNMZ and IMF after Pan et al. (2012). The major Paleocene-Eocene ore deposits (and associated ages) in the southern Lhasa subterrane include: Qiagong skarn Fe deposit (Li et al., 2011); Jiru porphyry Cu deposit (Zheng et al., 2014 and Yang et al., 2015b); Jialong skarn Fe deposit, Sadang vein-type Au-Ag deposit and Duodigou skarn Mo deposit (Huang et al., 2013). In the central Lhasa terrane: Chagele porphyry Cu-Mo deposit (Gao et al., 2012); Jiaduopule skarn Fe-Cu deposit (Yu et al., 2011); Narusongduo skarn Pb-Zn deposit (Ji et al., 2012); Mengya’a skarn Pb-Zn deposit (J.X. Li, unpublished data); Yaguila skarn-porphyry Pb-Zn-Ag-(Mo) deposit from (Gao et al., 2011); Sharang porphyry Mo deposit (Zhao et al., 2014). IYZSZ=Indus-Yaluzangbo Suture Zone, BNSZ=Bangong-Nujiang Suture Zone, SNMZ= Shiquanhe-Nam Tso Mélange Zone, LMF=Luobadui-Milashan Fault.

Figure 2. Simplified geological maps and cross-section of the Yaguila skarn Pb-Zn-Ag (-Mo) deposit, modified from Geological Survey Bureau of Henan (2009) and Zhao et al. (2015). Sampling positions identified by a star.

44

Figure 3. Distribution of intrusions and ore bodies in the adit of PD401 at Yaguila (A), with micrographic photos of Mo mineralization at Yaguila, including quartz+molybdenite+sericite+calcite veins in the contact between granite porphyry and hornfels (B), pyrrohotite+molybdenite+galena sulfide assemblages (C) and quartz+molybdenite+pyrite+sphalerite+calcite veins (D) in the skarn-type orebodies. Q=quartz, Cc=calcite, Ser=sericite, Mol=molybdenite, Po=pyrrohotite, Gn=galena, Sphal=sphalerite, Py=pyrite.

Figure 4. Simplified geological maps and cross-sections of the Sharang porphyry Mo deposit, modified from No. 6 Geologic Exploration Team of Geological Survey Bureau of Tibet, China (2009) and Zhao et al. (2015). Sampling positions identified by a star.

Figure 5. Micrographic photos of causative granite porphyry in Yaguila (A) and Sharang (B) deposits (cross-polarized light). Kf=K-feldspar, Q=quartz, Plag=plagioclase, Ser=sericite, Cc=calcite.

Figure 6. Graphic illustrations of the intrusion sequences in Yaguila and Sharang deposits. Geochronologic data are from Gao et al. (2011, 2015) and Zhao et al. (2014).

Figure 7. (Na2O + K2O) versus SiO2 diagram (A), classification from Le Bas et al. 45

(1986), and K2O versus SiO2 diagram (B), classification from Peccerillo and Taylor (1976). All data plotted for TAS diagram have been recalculated to 100% on a volatile-free basis for volcanics. Other Cretaceous felsic volcanics (~130 Ma) in the central Lhasa terrane are from Liu et al. (2010b, 2012) and Zhu et al. (2009).

Figure 8. Primitive mantle-normalized and chondrite-normalized REE patterns for volcanic and intrusive rocks at Yaguila. Primitive mantle and chondrite normalization factors are from Sun and McDonough (1989). The composition of upper crust, lower crust and total crust are from Rudnick and Gao (2003).

Figure 9. (A) Whole-rock εNd(t) vs. crystallization age diagram of the magmatic rocks from the Yaguila and Sharang deposits. The Nd isotope evolution curve of the depleted mantle (DM) is constructed using the present-day and

143

147

Sm/144Nd=0.2137

Nd/144Nd=0.51315 (Peucat et al., 1989). (B) Zircon εHf(t) vs

crystallization age diagram. The Hf isotope evolution curve of the depleted mantle (DM) is constructed using the present-day 176

176

Lu/177Hf =0.0384 and

Hf/177Hf =0.28325 (Griffin et al., 2000). Sharang data from Zhao et al. (2012,

2014). Data for early Cretaceous volcanics in the central Lhasa subterrane are from Zhu et al. (2009). The grey line represents the Nd-Hf isotopic evolutional trend of the analyzed samples in the district.

46

Figure 10. Chondrite-normalized REE patterns for zircons from the Paleocene-Eocene intrusions. Chondrite values are from Sun and McDonough (1989).

Figure 11. Zircon U-Th plots (A), EuN/EuN* ratios vs (Ce/Ce*)D ratios (B) and calculated Ti-in-zircon temperatures (C). Zircon Th/U ratios primarily range from 1.0 to 1.5, and Th/U ratios in zircons from the Yaguila granite porphyry plot between 0.5 and 1.0.

Figure 12. Diagrams of La/Sm-La (A), La/Yb-La (B), and Nb/Ta-Nb (C) for Yaguila Cretaceous rhyolitic volcanic rocks. Data for other felsic Cretaceous volcanics in the central Lhasa terrane (~130 Ma) are from Liu et al. (2010b, 2012) and Zhu et al. (2009). The fields for primitive and depleted mantle, chondrites and missing silicate reservoir in the Earth are from Barth et al.(2000). Data for the Himalayan leucogranites are from Wang et al. (2012b) and references therein. Data for upper and lower crust are from Rudnick and Gao (2003).

Figure 13. Sr vesus Ba (A) and Sr vesus Rb (B) plotting diagrams for Yaguila Paleocene intrusions and Sharang Paleocene-Eocene intrusions. Labeled vectors correspond to up to 50% fractionation crystallization of the main rock-forming minerals, such as hornblende (Hbl), muscovite (Ms), biotite (Bio), K-feldspar (Kfs) and plagioclase (Plag). The partition coefficient chosen in this study and detailed calculations are listed in Supplementary 3. 47

Figure 14. Geochemical plotting diagrams for Miocene dykes in the Yaguila and Sharang deposits (data from this study and Zhao et al. (2012)): A) K2O-N2O plots for the discrimination of ultrapotassic, shoshonitic and calc-alkalinic rocks, following the method of Foley et al. (1987) and Turner et al. (1996); B) (La/Yb)N-YbN plots with fields of adakites from Hou et al. (2004); C) Sr-Nd compositions of Yaguila and Sharang Miocene dykes, and adakitic, potassic-ultrapotassic rocks in southern and northern Tibet from 30-10 Ma. Data for potassic rocks in southern Tibet (20–10 Ma) are from Williams et al. (2004). Data for ultrapotassic rocks in southern Tibet (30–20 Ma) are from Miller et al. (1999) and Gao et al. (2007). Data for adakitic rocks (20-10 Ma) in southern Tibet (20-10 Ma) are from Hou et al. (2004). Symbols in the figure are identified in Figure 9.

Figure 15. Illustration of mantle contributions to the Paleocene-Eocene magmatic rocks (Zhao et al., 2012, 2014; Zheng et al., 2015; this study) at Yaguila-Sharang district, Tibet. The percentage of mantle contribution in the melts was calculated using zircon Hf isotopes (A) and whole-rock Nd isotopes (B), using binary mixing modeling following the method of Mišković and Schaltegger (2009). ‘Mantle’ refers to juvenile crust associated with subducted Tethyan ocean crust and the India-Asia continental collision. The assumed end-members of Hf isotopic binary mixing modeling (data from Zhu et al., 2011) include: zircon 48

εHf(t)=+18.8, Hf=8811 ppm for the most mafic components; ε Hf(t)=-20.5, Hf=12761 ppm for the most felsic components. Nd isotopic end-members are εNd(t)=+10, Nd=1.2 ppm for depleted mantle (Taylor and McLennan, 1985; Peucat et al., 1989), and εNd(t)=-22, Nd=26.0 ppm for lower continental crusts from Othman et al. (1984). The detailed calculations are provided in Supplementary 3.

Figure 16. Calculated (Ce/Ce*)D vs. temperature for the Paleocene-Eocene intrusions in the Yaguila and Sharang deposits. The curves for the oxygen fugacity buffers are ASI=1.25 (Trail et al., 2012), including magnetite-hematite (MH), Ni-Ni oxide (NNO), and Fe-wustite (IW) buffers. The calculated ASI values for Yaguila and Sharang Paleocene-Eocene intrusions are > 1.25. Table 1. Description of the location and mineralogy of volcanic and intrusive rocks in the Yaguila and Sharang deposits, Tibet.

Table 2. Major-element, trace-element and Sr-Nd isotopic compositions of the Yaguila volcanic and intrusive rocks.

Table 3. Summary of zircon trace element and Nd-Hf isotopic compositions of the Paleocene-Eocene intrusions in the Yaguila and Sharang deposits.

49

Supplementary 1. Zircon Lu-Hf isotopic data for volcanic and intrusive rocks in the Yaguila skarn Pb-Zn-Ag deposit

Supplementary 2. Zircon trace element compositions of the Paleocene-Eocene intrusions in the Yaguila and Sharang deposits.

Supplementary 3. Calculations: Partition coefficients used in the calculation of mineral vectors for the process of fractional crystallization and Hf-Nd isotopic mixing calculations.

50

Figure 1-R2

86°E

88°E

90°E

Linzizong Volcanic Succession Lake Jurassic granite Paleocene-Eocene Serling Co Cretaceous granite Nyima deposits Deposit name Paleogene granite (zircon U-Pb age /mica Ar-Ar age Neogene granite /molybdenite Re-Os age)

92°E Amdo

Triassic granite

32°N

N

Nam Co

Chagele(63.3 Ma) Narusongduo(62.5Ma)

Qiagong(68.8Ma)

Maizhuo kunggar

Lhasa Nyemo Jialong(61.1Ma)

100

Himalaya

Duodigou(66.7Ma)

Jiali

Yaguila(65.0 Ma) Sharang (52.3 Ma) Gongbogyamda

Jiaguopule(50.9Ma)

Xigaze KM

Fig.2-Fig4

Sadang(62.6Ma)

Jiru(50.8-48.3 Ma) Nanmulin

0

Lhasa terrane

Nagqu

Damxung Mengya’a(54.2 Ma)

LMF

96°E

Qiangtang terrane

BNSZ

SNMZ

30°N

94°E

IYZSZ

Nyingchi

30°13′58″

Figure 2-R2

92°41′00″

A

92°41′37″

92°42′14″

Q

5200 (m)

A

170°

B

Q 5100 F1

5000

PD401-13 Figure 3

C 2P 1 l 3 30°13′25″

C2P1l3

4900 F2 F3

4800

C2P1l2

C2P1l2

4700

A

100 m

YG09-10

F F2 F3

54° 72°

71°

F1

C2PC1l2P l2 2

1

YG09-01

B

30°12′21″

N C2P1l

0

500m

1

C 2P 1 l 1 Q

CC2PP l1 1 1 l 2

1

Upper Carboniferous -Lower Permian Laigu Fm.

30°12′52″

4600

YG309-438

YG09-15

B

Q

Cretaceous rhyolitic volcanic rocks

Quaternary sediments

3: Sandy slate and C2P1l3 Unit meta-quartz sandstone

Pb-Zn mineralized skarn

Unit 2: Meta-quartz

C2P1l2 sandstone and marble with

Pb-Zn ore body

C2P1l1

Mo ore body/ Horizontal projection

intercalation of limestone Unit 1: Silty slate with intercalation of meta-quartz sandstone Granodiorite porphyry dyke

71°

F

F

Fault

Porphyrytic biotite granite

Geological boundery

Granite porphyry

Suspected boundary

Sampling position

Figure 3-R2 Click here to download high resolution image

30°12′00″

Figure 4-R2

92°40′00″

92°40′30″

92°41′00″

92°41′30″

92°42′00″ 5400 (m)

SRD08-10

A

90°

B

ZK0205 ZK0105

5200

SRZK0105-92

ZK0905

B F

30°11′30″

A 5000 F

48°

P2m Q

SRD-28

26°

4800

Por-γ

SRZK0905-225

P2m

4600

100 m

SRD-6

30°11′00″

30°10′30″

ZK0405

ZK001

SRZK0207-7

48° 28° F

F

41°

43°

500m

ZK0105

B

Q

Quaternary sediments

Granite porphyry

P2m Upper Permian

Granite

Mengla Formation Lamprophyre dyke

F

N 0

ZK0905

A

SRD08-5

ZK0207

┴ ┴

Quartz diorite

Granodiorite porphyry

Quartz monzonite

Fine-grain granite porphyry

Hydrothermal breccias

Porphyritic granite

Magmatic breccias

F Fault Geological boundery 28° Strata Occurrence

Sampling position

Figure 5-R2

Figure 6-R2

Yaguila

Age / Ma 140

120 80

60

Sharang

Rhyolitic volcanic rocks (135-128 Ma)

Ore-forming granite porphyry (69-66 Ma) Yaguila Mineralization age (65.0 Ma)

Porphyritic biotite granite (61 Ma)

Pre-ore dioritic intrusions (56-53 Ma) Ore-forming granite porphyry (53 Ma) Sharang Mineralization age (52.3 Ma)

40

Granodiorite porphyry dykes (18 Ma)

20

0

Post-ore dykes (22-18 Ma)

Syn-ore intrusions (53-51Ma)

Figure 7-R2

Trachytetrachydacite (Qz-monzonite)

A

3

B

8 K2O (wt%)

Andesite (Diorite)

7 5

Rhyolite (Granite)

Trachyandesite (Monzonite)

Su Alka ba lic l ka lic Basaltic andesite (Gabbroic diorite)

Na2O+K2O (wt%)

9

10

Dacite (Granodiorite)

6

Shoshonite Series

4 erie

)S aline

lk lc-a a s C -K ( Serie h e g n i i l H alka s leiite) Serie CalcLow-K (Tho

2 0

1 45

50

55

60 65 70 75 SiO2(wt%) Rhyolitic volcanic rocks

80

85

Other early Cretaceous felsic volcanics in the central Lhasa terrane

s

45

50

55

60 65 70 75 80 SiO2(wt%) Granite porphyry Porphyritic bioite granite Miocene granodiorite porphyry

85

Figure 8-R2

1000

1000

Upper crust

100

10 Total crust

Lower crust

1

10

1

10

Yaguila Paleocene intrusions

100

10

D

Samples/Chondrite

1 1000

100

10

1

Rb Th Nb La Sr P Hf Eu Ti Yb Ba K Ta Ce Nd Sm Zr Tb Y Lu

Yaguila Miocene intrusions Granodiorite porphyry Other Miocene dykes at Sharang

100

10

E 0.1

Lower crust

Granite porphyry Porphyritic biotite granite

C

0.1 1000

Rhyolitic volcanic rocks Other early Cretaceous felsic volcanics in the central Lhasa terrane

Total crust

1 1000

100

Yaguila rhyolitic volcanic rocks

B

Samples/Chondrite

Samples/Primitive mantle

100

A

0.1 1000

Samples/Primitive mantle

Samples/Chondrite

Samples/Primitive mantle

Upper crust

F 1 La Ce Pr Nd SmEu Gd Tb Dy Ho Er Tm Yb Lu

Figure 9-R2

15

A

5

Intrusions at pre-ore stage Intrusions at ore-forming stage Intrusions at post-ore stage

Chondrite

0

Early Cretaceous volcanics in the central Lhasa

-5

B

Depleted Mantle 2σ(εHf(t)) 1σ(age)

10

Sharang

Zircon εHf(t)

Whole-rock εNd(t)

Rhyolitic volcanics Granite porphyry Porphyritic biotite granite Granodiorite porphyry

Depleted Mantle

10

20

Yaguila

Chondrite

0

-10

-10

-20

-15 0

30

60

90

Age/Ma

120

150

0

30

60

90 Age/Ma

120

150

Figure 10-R2

A Samples/Chondrite

10000

B Sharang Paleocene-Eocene intrusions (Pre-ore stage) 10000

100

100

1

1 PD401-13 Granite porphyry YG09-15 Porphyritic biotite granite

0.01 C

10000 Samples/Chondrite

Yaguila Paleocene intrusions

Sharang Eocene intrusions (Ore-forming stage)

0.01

10000

100

100

1

1

0.01

SRD-06 Granite 0207-7&SRD-28 Granite porphyry La Ce Pr NdSmEuGdTb DyHo Er TmYb Lu

SRD08-05 Quartz monzonite SRD08-10 Quartz diorite

0.01

D

Sharang Eocene intrusions (Ore-forming stage)

0905-225 Porphyritic granite 0105-92 Fine-grained granite porphyry La Ce Pr NdSmEuGdTb DyHo ErTmYb Lu

Figure 11-R2

1000

1000 Temperature (°C)

1. 0 1. 5

B

Th/U

1000

(Ce/Ce*)D

U (ppm)

1. 8

A

0. 3 0. 5

10000

100

Yaguila Granite porphyry Porphyritic biotite granite Sharang Intrusions at pre-ore stage Intrusions at ore-forming stage

C

900

800

700 Ti-in-zircon thermometer

100 100

10 1000 Th (ppm)

10000

600 0

0.2

0.4 0.6 EuN/EuN*

0.8

1.0

0

0.2

0.4 0.6 EuN/EuN*

0.8

1.0

Figure 12-R2

15

35

A g ltin

e lm d tr ia tren a

g ltin

Fractional crystallization trend

Nb/Ta

20 15

15

PM DM

10

10 3

Missing silicate reservior?

20

P

6

C

25

e lm d tr ia tren a

25

P

9

30

B

30

La/Yb

La/Sm

12

Fractional crystallization trend

5

5

0

0

Chondritic ratios Upper crust

Lower crust

Himalayan leucogranites

0 0

20

40

60 La (ppm)

80

100

0

20

40

60 La (ppm)

80

100

0.1

1

10 Nb (ppm)

100

Figure 13-R2

B

=1

0

1000

A

0.9

Plag An15

0.8

100

Plag An50

Kfs 0.5

Hbl

Kfs

100

Ms

Plag An15

Yaguila Granite porphyry Porphyritic biotite granite Sharang Intrusions at pre-ore stage Intrusions at ore-forming stage

0.7 Ms

0.6

R

R

Hbl

Plag An50

1000

Rb (ppm)

Ba (ppm)

b/ Sr

b/ Sr

=1

10000

Bio

Bio

10

10 10

100 Sr (ppm)

1000

10

100 Sr (ppm)

1000

Figure 14-R2

6

A

150

Sharang lamprophyre MgO>3 wt%

5

C

0

Ultrapotassic rocks in southern Tibet (30–20 Ma) Potassic rocks in southern Tibet (20–10 Ma) Adakitic rocks in southern Tibet (20–10 Ma)

120 Sharang Lamprophyre

-3

2

Adakites

90

εNd(t)

Shoshonitic

Ult rap

ota

3

2:1

(La/Yb)N

ssi

c

4 K2O (wt%)

3

B

60

1:2

Sharang lamprophyre

-15

0

0 0

1

2

3 4 Na2O (wt%)

5

6

-9

-12

30

Calc-alkaline

1

-6

0

5

10

15 YbN

20

-18 25 0.7000

0.7100

0.7200 0.7300 0.7400 (87Sr/86Sr)i

Figure 15-R2

Zircon Hf isotopes 100

A

80

Mantle contribution (%)

Mantle contribution (%)

100

60 40 20 0

B

80 60

Whole-rock Nd isotopes Yaguila Granite porphyry Porphyritic biotite granite Sharang Intrusions at pre-ore stage Intrusions at ore-forming stage

40 20 0

50

55

60 Age (Ma)

65

70

50

55

60 Age (Ma)

65

70

Figure 16-R2

Yaguila (Paleocene) Granite porphyry Porphyritic biotite granite

Sharang (Paleocene-Eocene) Intrusions at pre-ore stage Intrusions at ore-forming stage

1000

(Ce/Ce*)D

100 MH

10

NNO IW

1 1100

1000

900 800 Temperature (°C)

700

600

Table 1-R3

Table 1. Description of the location and mineralogy of volcanic and intrusive rocks in the Yaguila and Sharang deposits, Tibet. Deposit Yaguila

Sharang

Sample

Location

Lithology

Mineralogy*

YGZK309-438

30°13′00″N, 92°41′44″E

Rhyolitic volcanics

Q, Kf, Plag

YG09-10

30°13′02″N, 92°42′28″E

Rhyolitic volcanics

Q, Kf, Plag

PD401-13

30°12′54″N, 92°41′56″E

Granite porphyry

Pheo: Kf, Q, Plag, Bio; Groud: Kf, Q, Plag, Bio

YG09-15

30°12′51″N, 92°41′07″E

Porphyritic biotite granite

Pheo: Kf, Q, Plag, Bio; Groud: Kf, Q, Plag, Bio

YG09-01

30°12′48″N, 92°41′48″E

Granodiorite porphyry

Pheo: Plag, Bio, Hbl, Q, Kf; Groud: Kf, Q, Plag

SRD08-05

30°10'59"N, 92°41'38"E

Quartz monzonite

Plag, Bio, Q, Kf, Hb

SRD08-10

30°12'00"N, 92°41'49"E

Quartz diorite

Plag, Bio, Hbl, Kf, Q

SRD-6

30°11'00"N, 92°41'18"E

Granite

Kf, Q, Plag, Bio

0207-7

30°10'59"N, 92°41'17"E

Granite porphyry

Pheo: Kf, Q, Plag, Bio; Groud: Kf, Q, Plag, Bio

SRD-28

30°11'15"N, 92°41'38"E

Granite porphyry

Pheo: Kf, Q, Plag, Bio; Groud: Kf, Q, Plag, Bio

0905-225

30°10'54"N, 92°40'54"E

Porphyritic granite

Kf, Q, Plag, Bio

0105-92

30°10'54"N, 92°41'09"E

Fine-grained granite porphyry

Pheo: Kf, Q, Plag, Bio; Groud: Kf, Q, Plag, Bio

*Pheo=pheocryst, Kf=K-feldspar, Q=quartz, Plag=plagioclase, Bio=biotite; Groud=groundmass, Hbl=hornblende.

Table 2-R3

Table 2. Major-element, trace-element and Sr-Nd isotopic compositions of the Yaguila volcanic and intrusive rocks. Sample Name

YG09-10

Rock type Age/Ma

YGZK309-438

ZK06

YG09-15

YG09-01

Porphyritic biotite

Granodiorite

granite

porphyry

PD06

PD402

PD301-1

PD401-8

PD401-1

PD401-4

PD401-7

YL-30

YL-32

YL-33

Granite porphyry (Quartz porphyry in Gao et al. (2015) and Zheng et al. (2015)) 1

Rhyolitic volcanic rocks 136

ZK301-86

134

125

60.8

17.9

66.5

66.2

62.6

Major elements (wt%) SiO2

78.2

78.4

70.6

70.9

69.2

77.2

73.1

75.2

77.5

74.7

76.3

70.9

77.1

72.3

75.9

76.2

TiO2

0.15

0.15

0.22

0.29

0.32

0.54

0.03

0.44

0.53

0.08

0.65

0.68

0.44

0.21

0.14

0.15

Al2O3

13.3

13.3

16.6

14.6

13.6

12.1

13.2

9.8

11.6

12.7

13.2

13.8

8.8

14.7

13.1

13.1

Fe2O3

0.19

0.73

1.02

0.82

0.96

0.76

0.31

0.10

0.88

0.13

0.85

0.62

0.49

0.64

0.30

0.37

FeO

1.10

0.60

0.22

1.32

1.10

1.31

0.22

1.96

0.90

0.22

1.56

3.79

2.42

1.22

0.65

0.68

MnO

0.10

0.10

0.02

0.06

0.05

0.06

0.18

0.10

0.05

0.10

0.08

0.16

0.22

0.20

0.02

0.02

MgO

0.20

0.19

0.38

0.51

1.07

0.83

0.16

1.01

0.69

0.15

0.92

1.63

1.75

0.16

0.14

0.24

CaO

0.20

0.20

0.02

1.87

2.91

0.35

2.36

1.55

0.09

1.19

0.22

0.46

2.43

1.09

1.47

1.12

Na2O

0.03

0.02

0.12

4.06

0.71

0.20

0.18

0.13

0.58

0.25

0.11

0.13

0.45

1.44

2.10

2.38

K2O

2.71

2.71

8.35

3.97

3.88

4.49

6.98

5.72

5.70

8.66

4.02

4.64

3.33

5.76

5.56

5.75

P2O5

0.03

0.03

0.04

0.09

0.10

0.13

0.03

0.08

0.08

0.02

0.12

0.15

0.11

0.04

0.02

0.02

LOI

3.56

3.68

1.88

0.82

6.14

1.88

3.09

3.84

1.47

1.77

1.92

2.30

1.80

1.34

0.51

0.43

Sum

99.8

100.1

99.5

99.5

100.1

99.9

99.8

99.9

100.1

99.9

99.9

99.2

99.3

99.2

99.8

100.0

Trace elements (ppm) Ba

360

130

704

707

540

1966

224

584

415

411

346

344

260

1592

554

601

Rb

156

281

468

137

217

254

334

296

254

354

168

236

288

262

203

218

Th

33.3

28.7

23.6

20.5

36.1

15.7

11.0

8.27

13.8

18.4

16.5

18.7

14.6

36.4

33.3

31.1

Nb

16.8

17.6

13.1

10.9

11.9

13.3

18.1

8.02

12.4

13.3

14.5

16.0

9.91

15.1

13.0

12.8

Ta

1.49

1.28

0.86

0.93

1.24

0.94

2.05

0.62

0.85

1.45

0.98

1.17

0.70

1.18

1.16

1.10

Sr

10.4

7.04

51.6

208

76.0

14.6

63.5

67.1

34.0

56.3

11.6

12.9

51.6

117

146

125

Zr

169

228

212

162

116

240

29.8

284

235

50.9

251

185

260

223

134

140

Hf

5.61

7.15

6.65

4.24

4.00

6.78

2.08

7.87

6.27

2.39

7.17

5.84

6.90

6.17

4.39

4.41

La

48.1

64.3

83.6

48.5

32.1

13.5

8.85

19.3

24.5

18.2

37.9

45.0

35.0

81.5

43.4

41.1

Ce

93.3

123

161

86.8

60.4

36.0

18.1

41.4

50.6

36.5

77.8

91.1

65.9

162

89.2

85.8

Pr

11.0

14.5

16.8

9.45

5.79

4.81

2.11

4.72

5.50

4.07

8.32

9.41

6.80

17.1

10.1

9.68

Nd

41.5

51.6

62.7

32.7

20.6

21.7

8.21

18.8

21.4

15.6

31.5

35.0

25.3

60.8

35.8

35.3

Sm

8.53

9.06

10.7

5.58

3.02

4.87

2.90

3.74

4.01

3.67

6.02

6.51

4.79

10.8

7.21

7.16

Eu

0.89

1.26

1.74

1.13

0.71

0.85

0.34

0.52

0.71

0.46

1.10

1.18

0.88

1.74

0.94

0.88

Gd

8.34

7.12

9.87

4.63

2.06

4.97

3.46

3.68

3.66

3.71

5.76

6.33

4.88

9.05

6.50

6.40

Tb

1.49

1.07

1.28

0.72

0.28

0.70

0.62

0.52

0.48

0.6

0.78

0.86

0.69

1.35

1.03

1.00

Dy

9.07

5.59

6.65

4.07

1.21

3.94

3.91

2.90

2.69

3.78

4.33

4.83

3.93

7.28

5.89

5.62

Ho

1.75

1.00

1.25

0.78

0.20

0.78

0.77

0.56

0.54

0.80

0.85

0.96

0.77

1.44

1.21

1.19

Er

5.39

3.19

3.43

2.27

0.63

2.19

2.16

1.60

1.63

2.48

2.43

2.74

2.22

4.35

3.5

3.42

Tm

0.85

0.52

0.45

0.36

0.08

0.29

0.31

0.23

0.23

0.38

0.34

0.38

0.31

0.60

0.50

0.50

Yb

5.15

3.22

2.84

2.32

0.62

1.93

2.06

1.44

1.56

2.66

2.25

2.50

2.02

3.90

3.21

3.30

Lu

0.81

0.52

0.39

0.38

0.11

0.27

0.28

0.19

0.23

0.42

0.33

0.35

0.29

0.57

0.50

0.49

Y

54.1

31.7

31.1

23.3

6.10

20.7

22.9

14.9

14.3

24.0

21.8

25.2

20.2

41.3

34.4

34.2

Pb

75.6

121

38.5

82

34.7

22.3

23.0

U

5.08

3.17

2.65

4.79

4.28

4.20

4.00

47.2

125

1.77

8.60

0.785058

0.819195

0.709007

0.711816

0.000019

0.000012

0.000013

0.000011

0.707476

0.70963

0.726610

0.727476

0.728054

87

Rb/86Sr

87

Sr/86Sr 2σ

87

86

( Sr/ Sr)i 147

144

143

144

Sm/

Nd

0.1285

0.1126

0.1016

0.0925

Nd

0.511917

0.511933

0.512348

0.512466

0.511915

0.511931

0.511926

0.000010

0.000010

0.000010

0.000011

0.000005

0.000006

0.000008

0.511803

0.511834

0.512308

0.512455

0.511876

0.511887

0.511882

εNd(t)

-12.9

-12.3

-4.92

-3.12

-13.5

-13.3

-13.4

TDM2

1976

1929

1268

1087

1916.05

1956.91

1968.8

References

This study

This study

This study

This study

Nd/

2σ (

143

Nd/

144

Nd)i

Gao et al. (2015) 1

Granite porphyry data are summarized from Gao et al. (2015) and Zheng et al. (2015).

Gao et al. (2015)

Zheng et al. (2015)

Table 3-R2

Table 3. Summary of zircon trace elements and Nd-Hf isotopic compositions of the Paleocene-Eocene intrusions in the Yaguila and Sharang deposits. Deposit Yaguila

Sharang

Lithology

Age/Ma

Zr εHf(t) a.v.1

εNd(t)

Zr (Ce/Ce*)D2

Zr EuN/EuN*3

Ti-in-zircon/°C

lnfO2

Granite porphyry

67-65

-13.9 to +3.6

-13.5 to -13..3

331 to 691

0.30 to 0.38

639 to 703

-26.4 to -17.8

Porphyritic biotite granite

60.9±0.3

+1.7

-4.9

13.6 to 80.8

0.15 to 0.38

645 to 724

-43.5 to -28.3

Quartz monzonite

56.1±1.4

+3.3

-2.0

18.4 to 28.6

0.12 to 0.14

859 to 904

-20.8 to -17.6

Quartz diorite

53.1±0.6

+2.1

-0.6

23.1 to 59.5

0.24 to 0.27

773 to 831

-26.7 to -15.6

Granite

52.9±0.5

+-1.7

-3.5

101 to 211

0.47 to 0.58

745 to 770

-19.4 to -11.8

Granite porphyry

52.9-52.6

+-0.9

-4.6 to -3.4

73.2 to 131

0.42 to 0.52

684 to 780

-28.0 to 15.1

Porphyritic granite

52.3±0.4

+-1.2

-3.9

73.4 to 140

0.40 to 0.59

701 to 768

-25.3 to -18.5

Fine-grained granite porphyry

51.6±0.4

null

null

60.8 to 85.3

0.50 to 0.61

714 to 760

-27.4 to -20.8

1. a.v.=average value; 2. The (Ce/Ce*)D values were calculated using the definition of Trail et al. (2012) and lattice strain model (Blundy and Wood, 1994) using liner regression from Nd to Lu; 3. EuN/EuN* were calculated by EuN/(SmN*GdN)1/2, where the abundances were normalized to chondrite values.

Highlights: Cretaceous rhyolites were formed by the melting of ancient continental crust. There was a higher mantle flux into the source of magmatism from Paleocene to Eocene. Miocene granodioritic dykes were originated from the enriched lithospheric mantle. Mo mineralization is closely related to highly oxidized and differentiated magma.

51