Origin of Eocene adakitic magmatism in northwest Turkey

Journal Pre-proofs Origin of Eocene adakitic magmatism in northwest Turkey Merve Özyurt, Şafak Altunkaynak PII: DOI: Reference:

S1367-9120(19)30499-7 https://doi.org/10.1016/j.jseaes.2019.104147 JAES 104147

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Journal of Asian Earth Sciences

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10 October 2018 28 October 2019 12 November 2019

Please cite this article as: Özyurt, M., Altunkaynak, S., Origin of Eocene adakitic magmatism in northwest Turkey, Journal of Asian Earth Sciences (2019), doi: https://doi.org/10.1016/j.jseaes.2019.104147

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Origin of Eocene adakitic magmatism in northwest Turkey Merve Özyurt1 and Şafak Altunkaynak2 1Department

of Geological Engineering, Karadeniz Technical University, 61080, Trabzon,

Turkey; 2Department of Geology Engineering, Istanbul Technical University, Maslak, 34469 Istanbul, Turkey.

ABSTRACT In this study, we focus on adakitic porphyries, which are rare and recently discovered in the northwest (NW) Turkey. We present a comprehensive dataset including their petrography, geochemistry, and 40Ar/39Ar geochronology to gain insight into the causes, timing, and possible melt sources of adakitic magmatism in the absence of active subduction. The studied adakitic porphyries are found as stocks, dikes, and sills associated with the Orhaneli plutonic complex, which intruded into ophiolitic and blueschist rocks of the Izmir–Ankara suture zone (IASZ). The porphyries yielded 40Ar/39Ar biotite ages of 53.70 ± 0.29 to 53.84 ± 0.16 Ma (early Eocene), indicating they were coeval with the Orhaneli pluton. They are represented by porphyritic microgranite and microgranodiorite and consist of quartz, plagioclase, K-feldspar, hornblende, and biotite. These adakitic porphyries are similar to those found worldwide, and display distinct geochemical properties such as high SiO2 and Sr at 63.80–69.43 wt% and 1129–1719 ppm, respectively; low Y and Yb at 6.2–12.8 ppm and 0.53–1.07 ppm, respectively; high ratios of Sr/Y and LaN/YbN at 169–2645 and 10–215, respectively; enrichment in large-ion lithophile elements (LILE) and light rare earth elements (LREE); depletion in high-field-strength elements (HFSE); and insignificant or lack of Eu anomaly (Eu/Eu*) at 0.87–1.11. However, they differ from adakites by their potassic nature with high

87Sr/86Sr

0.706249–0.706577 and 15.669–15.700, respectively, and low

and

143Nd/144Nd

207Pb /204Pb , i i

at

isotopic values

(εNd -2.94–0.59), all of which correspond to continental adakites (C-adakites). Overall evaluation of major-trace elemental composition and isotopic data revealed that adakitic porphyries were generated by partial melting of mafic lower crustal rocks and heterogeneous lithospheric mantle and their interaction. Assimilation and fractional crystallization (AFC) played an important role during the evolution of these melts at shallow crustal levels. Collectively, the geochemical characteristics, timing, and nature of the adakitic porphyries and the geological background of the region indicate that the adakitic magmatism was not formed above an actively dehydrating subducted slab; rather, these characteristics are consistent with magmatism that is more typical of intraplate tectonic settings. We infer that upwelling of the asthenospheric mantle as a result of steepening and breaking of the subducted Tethyan oceanic slab or partial delamination of the base of the lithosphere would raise the geothermal gradient beneath the suture zone and increase heat flow to trigger the generation of K-rich C-adakite magmas in NW Turkey during the early Eocene.

Keywords: NW Turkey, continental adakites, Eocene, geochemistry, 40Ar/39Ar geochronology.

1. Introduction Adakite is the most recent and ever-evolving genetic term used by petrologists to describe intermediate to felsic magmatic rocks with distinct geochemical characteristics including SiO2 ≥ 56 wt%, Al2O3 ≥ 15 wt%, MgO ≥ 3 wt% but rarely above 6 wt% MgO, high concentrations of light rare earth element (LREE) and Sr/Y and La/Yb ratios, and the lack of an Eu anomaly (Defant and Drummond, 1990; Castillo, 2006). The origin and petrogenetic significance of adakite, which have attracted the attention of numerous researchers, have been investigated worldwide for the past three decades. It was initially considered to occur in island arc settings at margins of young (≦25 Ma) and hot oceanic slab subduction (Defant and Drummond, 1990; Castillo, 2006; Moyen, 2009). However, numerous recent petrological studies have proposed that a wide range of magmatic rocks with these distinct geochemical characteristics have also been generated in a variety of intraplate tectonic settings through various crust–mantle interaction processes including magma mixing and fractional crystallization (FC; Defant and Drummond, 1990; Martin et al., 2005; Richards and Kerrich, 2007; Xiao and Clemens, 2007; Moyen, 2009; Castillo, 2006, 2012; Zhang et al., 2013, and references therein). These rocks are generally regarded as adakite-like or adakitic rocks, continental (C)-type adakites, or pseudo adakite and have been reported in post-collisional settings around the world (e.g., Wang et al., 2004; Guo et al., 2006; Kamei et al., 2009; Castillo, 2012; Gao et al., 2004; Chung et al., 2003, and references therein). Although investigations on adakitic (adakite-like) rocks have enriched our understanding of crustal evolutionary processes occurring at different tectonic settings, this has led to some confusion and debates on the occurrence and petrogenesis of adakites (Castillo, 2012). In recent years, magmatic suites with adakitic signature have also been reported throughout northern Turkey and the surrounding areas including Greece, South Bulgaria, and

Iran, which comprise part of the Alpine–Himalayan orogenic belt. According to these records, adakitic magmatism occurred in two different episodes: in the late Mesozoic (Genç and Kayacı, 2012; Yılmaz-Şahin et al., 2012) and in the Cenozoic (e.g., Topuz et al., 2005, 2011; Jahangiri, 2007; Varol et al., 2007; Karslı et al., 2010, 2011; Eyuboğlu et al., 2011; Altunkaynak et al., 2012a,b; Marchev et al., 2013; Dokuz et al., 2013; Rosetti et al., 2014; Ahmadian et al., 2016; Alirezaei, et al., 2017; Omrani, 2018). Most studies seem to agree that the first episode (late Mesozoic) of the adakitic magmatism was derived from partial melting of the subducted oceanic crust (e.g., Genç and Kayacı, 2012; Yılmaz-Şahin et al., 2012). However, the specific heat source needed to provide a magma source for generating a second episode (Cenozoic) of adakitic magmatism has led to controversy among the petrogenetic models, which generally ascribe this to slab break-off or delamination of the lower part of the lithosphere in a postcollisional setting after the northward subduction of the Neo-Tethys along the southern border of the Sakarya Zone (e.g., Kadıoğlu and Dilek, 2010; Karslı et al., 2011; Altunkaynak et al., 2012b; Marchev et al., 2013). In contrast, Eyuboğlu et al. (2011) proposed that the second episode of this adakitic magmatism was generated by slab window-related processes that occurred during the ridge subduction in a south-dipping subduction zone. Therefore, the petrogenesis and the tectonic setting of the second episode of adakitic magmatism remains the topic of considerable debate. Although, the adakitic magmatism in eastern Turkey is relatively well documented (e.g., Eyüboğlu et al., 2011; Karslı et al., 2010, 2011; Topuz et al., 2005, 2011), exceedingly few studies have considered adakitic magmatism in western (W) Turkey (e.g., Varol et al., 2007; Altunkaynak et al., 2012; Şen and Şen, 2013; Gençoglu-Korkmaz et al., 2017). The study area is located in the Orhaneli area (Bursa) of W Turkey, where calc–alkaline plutonic rocks and hypabyssal associations with adakitic characteristics are widely distributed. We have previously discovered rocks with adakite signatures in this region and presented

major-trace elemental and Sr-Nd isotopic data of them in Altunkaynak et al., 2012b. However, this study reported limited conclusions, and a more detailed and systematic field, petrographical, geochemical, and geochronological investigation was needed to enhance our understanding of the Cenozoic adakitic magmatism in western Anatolia. In this study, we present a new comprehensive dataset including petrography, major-trace element geochemistry, Pb isotope composition, and

40Ar/39Ar

geochronology of porphyries together with field

observations to more effectively explain the timing, origin, and melt evolution of the adakitic occurrences in northwestern (NW) Anatolia. We evaluate our new data together with our previously published major-trace elemental and Sr-Nd isotopic data obtained from adakitic porphyries and related rocks (Altunkaynak et al., 2012b) and those obtained from neighboring regions to reveal the general characteristics of adakitic rocks in northwest Turkey as a case study of adakitic magmatism in a post-collisional setting. 2. Geological setting and field characteristics of adakitic porphyries Located at the eastern part of the Alpine–Himalayan orogenic belt, NW Turkey is a critical area where diverse magmatic successions representing the complicated tectonomagmatic evolution of the Tethys are well preserved (Fig. 1a). The basement geology of NW Turkey is a collage of different tectonic units including the Rhodope Massif (RM), the Intra–Pontide Suture Zone (IPSZ), the Sakarya Continent (SC), the Izmir–Ankara Suture Zone (IASZ), and the Anatolide–Tauride Platform (ATP) (Fig. 1a; Şengör and Yılmaz, 1981; Okay and Satır, 2000). Tectonically, NW Anatolia has been influenced mainly by (1) closure of the Neo-Tethys during the Cretaceous and pre-middle Eocene along the IASZ and (2) subduction along the Aegean– Cyprian Arc since the late Oligocene–early Miocene (Okay et al., 1996; Okay and Tüysüz, 1999; Bozkurt and Mittwede, 2001; Bozkurt and Oberhansli, 2001; Van Hinsbergen et al., 2005; Altunkaynak and Dilek, 2013). These tectonic events have been generally considered to have caused three magmatic pulses in the Cenozoic during the (1) early to late Eocene, (2) late

Oligocene to middle Miocene, and (3) late Miocene to Quaternary (e.g., Genç and Yılmaz, 1997; Yılmaz and Polat, 1998; Altunkaynak and Yılmaz, 1998; Yılmaz et al., 2000; Aldanmaz et al., 2000, 2006; Boztuğ et al., 2007; Altunkaynak, 2007, 2012a,b; Keskin et al., 2008; Karacık et al., 2008; Erkül, 2010; Shin et al., 2013; Unal and Altunkaynak, 2018; Kamacı and Altunkaynak, 2019; and references therein). Eocene magmatism has produced plutonic, hypabyssal, and volcanic associations that are limited to NW Turkey; Eocene adakite-like porphyries are rarely exposed among them (Fig. 1a, b). In the Orhaneli area (Bursa, NW Turkey), adakite-like porphyries are well exposed. They are considered to be spatially and temporally associated with the Orhaneli pluton, which was emplaced into the collision zone of the IASZ between the SC and ATP (Altunkaynak et al., 2012; Şengör and Yılmaz, 1981). The main stratigraphic units in the investigated area are represented by basement rocks, plutonic rocks, rocks of hypabyssal association, and volcanic rocks (Figs. 1b, 2a). The basement rocks are represented by a Cretaceous ophiolite sequence consisting of peridotite, diabase, gabbro, and pyroxenite as well as blueschist rocks of the Tavşanlı Zone including phyllite, schist, marble, and metabasalt. The ophiolitic rocks are tectonically situated above these blueschist rocks (Harris et al., 1994; Okay et al., 1998). The basement rocks are cut by plutonic and hypabyssal rocks, resulting in contact metamorphism, and are covered unconformably by early Miocene volcanic rocks (Altunkaynak, 2007). The Orhaneli pluton (Vachette et al, 1968; Özkoçak, 1969; Ataman, 1972; Bingöl et al., 1982; Harris et al., 1994), with an area of nearly ~220 km2, is composed of granodiorite, syenite, border zone rocks such as aplogranite and microgranite, and vein rocks such as aplite and pegmatite (Altunkaynak, 2007). Zircon SHRIMP U-Pb emplacement and 40Ar/39Ar cooling ages obtained from the Orhaneli pluton are 52.8 and 51.8-50.5 Ma, respectively (Harris et al., 1994; Altunkaynak et al., 2012b). Hypabyssal association, which is the focus of this study, is represented by a suite of felsic dikes and stocks accompanied by minor amounts of mafic syn-

plutonic dikes. These felsic syn-plutonic dikes and stocks (adakitic porphyries) are randomly distributed throughout the pluton and the surrounding basement rocks but are widespread in the southwestern part of the Orhaneli pluton (Figs. 1b, 2a, 3a-c). The distribution of these dikes and stocks is given in a detailed geological map of the study area in Fig. 2a. Ranging from 100 cm to 25 m in width, the studied dikes generally have an overall NW–southeast (SE) strike with variable dips to the south (Fig. 2a, b). The presence of felsic and mafic dikes, which cut each other with sharp contacts with no metamorphic effects, suggests the coexistence of mafic and felsic melts in the magmatic system. The dikes contain randomly distributed blob-like mafic microgranular enclaves of 3 cm–5 m (Fig. 3d) and metamorphic rock xenoliths toward the host rocks, which indicate magma mingling/mixing processes and wall-rock assimilation during the magma evolution, respectively. The hypabyssal association cross-cuts both plutonic and basement rocks and is unconformably covered by volcanic rocks (Figs. 1b, 2a, b) (Altunkaynak, 2007). The youngest rock group of the studied area contains volcanic rocks with K/Ar ages of 17–19.4 Ma (Altunkaynak, 2007). These volcanic rocks generally form pyroclastic units and felsic to mafic lavas (rhyolite–rhyodacite and basaltic–trachyandesite) covering the basement rocks, plutonic rocks, and hypabyssal rocks.

3. Materials and methods In total, 107 samples were collected from the outcrops of the hypabyssal association (Figs. 1a, 2a) and were examined under a polarizing microscope. According to a detailed petrographic study, the representative samples were selected for whole-rock geochemical analysis (Table 1). Whole-rock major, trace and rare earth element (REE) contents of selected samples were performed by ACME Analytical Laboratories, Ltd. (Canada). Major oxides and trace elements were analyzed by using Inductively coupled plasma atomic emission spectrometry (ICP-AES) from the pulp after 0.2 g of rock powder was fused with 1.5 g LiBO2 and then dissolved in 100 ml of 5% HNO3. REE contents were determined by inductively coupled plasma-mass spectrometry (ICP-MS) after 0.25 g rock powder was dissolved during multiple acid digestion steps. The detection limits (d.l.) are given in Table 1 (see d.l. column). Pb- isotope ratio measurements of 10 samples were determined by MC-ICP-MS (NEPTUNE, ThermoScientific, Bremen) at ALS (Sweden) by using a combination of internal standardization (Tl added to all solutions at fixed concentration) and external calibration with matrix-matched standards to correct for instrumental mass-bias. Samples were dissolved in a mixture of HF and HNO3 (0.5 g sample, 5 ml HNO3+HF). Matrix separation was performed by Sr-Specific resin (disposable 2 ml columns). Isotope measurements were performed at least in duplicate. All Sr-Nd isotope data used in this study were published previously and presented in Table 2 (See Altunkaynak et al., 2012b for detailed explanation). 40Ar/39Ar

age measurements were performed on biotite separates from adakite-like

porphyries (samples MG-6 and MG-4) and hornblende separates from mafic syn-plutonic dikes (samples MG-100b and MG-57) (Table 3). The analyses were carried out in the Argon Geochronology Laboratory at the University of Michigan, using the laser step heating method. Samples were wrapped in pure Al foil and irradiated for 80 MWh hr at the medium neutron flux location 5C in the McMaster Nuclear Reactor at McMaster University in Hamilton, Ontario

in irradiation package mc36. Samples were incrementally heated with a Coherent Innova 5 W continuous argon-ion laser until complete fusion was achieved. Ar isotopes were measured using a VG1200S mass spectrometer with a source operating at 150 A total emission and equipped with a Daly detector operating in analog mode. Mass discrimination was monitored daily using ~4x10-9 ccSTP of atmospheric Ar. Fusion system blanks were run every five fusion steps and blank levels from argon masses 36 through 40 (~6 x 10-14, ~8 x 10-14, ~2 x 10-14, ~4 x 10-14, and 5 x 10-12 ccSTP) were subtracted from sample gas fractions. Corrections were also made for the decay of 37Ar and 39Ar, as well as interfering nucleogenic reactions from K, Ca and Cl, and the production of 36Ar from the decay of 36Cl. 3. Results 3.1. Petrography The felsic dikes and stocks (adakitic porphyries; Fig. 4a) were classified as porphyritic microgranite, micro-granodiorite, and micro-quartz monzonite, whereas the mafic syn-plutonic rocks were classified as microquartz–diorite and diorite (Fig. 4b). The mafic magmatic enclaves (MMEs) are represented by diorite and quartz diorite (Fig. 4c). All of the felsic dikes exhibit microgranular porphyric and microgranular textures (Fig. 4a); cumuliform texture was also observed in some thin sections (Fig. 4d). These dikes are composed mainly of plagioclase, Kfeldspar, quartz, hornblende, and biotite (Fig. 4e). The K-feldspar and plagioclase phenocrysts commonly occur in a microgranular groundmass at up to 40 vol%. Alkali–feldspar phenocrysts are generally subhedral or euhedral and they display Carlsbad twinning (Fig. 4e). Plagioclase phenocrysts show polysynthetic or albite–Carlsbad twinning. Anhedral, zoned plagioclase crystals and euhedral, unzoned crystals are also present (Fig. 4f). Plagioclase is found as schiller inclusions along the zone line of the host plagioclase; corroded plagioclase is also common (Fig. 4g). The quartz crystals commonly have rounded shapes. The mafic syn-plutonic dikes are represented by dioritic composition (Fig. 4b) and exhibit holocrystalline microgranular or

porphyritic texture. Their minerals include plagioclase, hornblende, biotite, and rarely quartz and sanidine. The most abundant mineral is plagioclase, occurring as phenocrysts. Some altered mafic syn-plutonic dikes contain biotite crystals that have been altered to chlorite, particularly along cleavages and grain boundaries. Their groundmass consists commonly of plagioclase microcrysts. In addition, the studied felsic and mafic dikes contain abundant ellipsoidal to rounded MMEs that show hypocrystalline to holocrystalline texture (Fig. 3d, 4c).

3.2. Major and trace element geochemistry The chemical analyses of the representative rock samples containing porphyry dikes and stocks (adakite-like porphyries), mafic syn-plutonic dikes, and MMEs (mafic magmatic enclaves) are presented in Table 1. The SiO2 content of the studied rocks ranged from 53.71 to 69.43 wt% (Fig. 5a). In the SiO2 versus K2O + Na2O diagram, the porphyries plotted mainly in the fields of granite and granodiorite, whereas the MMEs and mafic syn-plutonic dikes plotted in the fields of diorite, syenodiorite, and gabbro–diorite (Fig. 5a). The porphyries show medium-K calc-alkaline to shoshonite characteristics with high SiO2 and Al2O3, at 63.80–69.43 wt% and 15.44–16.64 wt%, respectively. They have relatively low contents of MgO, at 0.19– 1.9 wt%, FeO, at 1.68 to 3.34 wt%, and Co, at 0.80–8.50 ppm. The mafic syn-plutonic dikes and MMEs have medium- to high-K calc-alkaline affinity and relatively low SiO2, at 53.71– 57.95, and high contents of Al2O3, MgO, FeO, and Co at 15.66–16.19 wt%, 3.48–5.50 wt%, 5.40–7.23 wt%, and 17.69–21.10 ppm, respectively (Table 1 and Fig. 5b). Using the A/CNK versus A/NK diagram of Maniar and Piccoli (1989), the mafic syn-plutonic dikes and the MMEs are metaluminous, although the studied porphyries plotted mainly in the field of metaluminous to slightly peraluminous (Fig. 5c). Further, the chemical compositions of all studied rocks, including MMEs, mafic syn-plutonic dike, and porphyries, confirm I-type affinity (Fig. 4a; Harris et al., 1986), and most of these rock samples are sub-alkaline in character (Fig. 4c; Irvine and Baragar, 1971). The Mg# of the MMEs (68.5-69.2) and mafic syn-plutonic dikes (64.3-67.5) are high, whereas those of the porphyries are variable (14.6– 54.5) (Fig. 5d). As shown in the Harker variation diagrams in Fig. 6, the contents of MgO, TiO2, Fe2O3, CaO, and P2O5 show positive trends, although K2O shows a negative trend with increasing SiO2. The porphyry dike and stock samples are further characterized by high Sr/Y ratios (20-215), high LREEs and Sr (427-1719 ppm), low heavy rare earth elements (HREEs) and Y (6–12 ppm), a lack of obvious Eu anomalies (Eu/Eu* ≈ 0.9–1.11), a wide range of Mg#

(14.6–54.5), low Cr2O3 (predominantly <0.002 wt%) and Ni (mostly <20 ppm) (Fig. 6a–d). These geochemical characteristics indicate similarity with rocks defined as adakites (Fig. 7a– d; Defant and Drummond, 1990). 3.3. Sr-Nd-Pb isotope geochemistry New Pb isotope data for the adakitic porphyries, mafic syn-plutonic dikes, and MMEs together with previously published Sr-Nd isotope data (Altunkaynak et al., 2012b) obtained from the same samples are given in Table 2. We calculated the initial Sr-Nd-Pb isotope ratios and εNd values of samples using an average 40Ar/39Ar age of 54 Ma (Fig. 8a-d; Table 3). The

87Sr/86Sr

(i)

and

143Nd/144Nd

(i)

values range between 0.70625-0.70657 and 0.51260-

0.51242 (εNd(i): -2.94-0.59), respectively for the adakitic porphyries; 0.70541-0.70634 and 0.51260-0.51256 (εNd(i): -1.05-0.69), respectively for the MMEs; and are 0.70653 and 0.51246 (εNd(i): -2.21), respectively for mafic syn-plutonic dike sample (Fig. 9). The initial 206Pb/204Pb, 207Pb/204Pb,

and

208Pb/204Pb

values are 18.454-19.120, 15.671-15.70 and 37.480-39.345,

respectively for the adakitic porphyries; 18.40, 15.669 and 38.109 for mafic syn-plutonic dikes and 18.811, 15.693 and 38.989 for MMEs, respectively (Fig. 10). 3.4. Geochronology The 40Ar/39Ar radiometric ages of the adakitic porphyries (samples MG4 and MG6) and the mafic dikes (samples MG100b and MG57) are listed in Table 3, and the age spectrum plots are shown in Fig. 8. The biotite separates from the adakitic porphyry samples yielded plateau age of 53.84±0.16 and 53.70±0.19 Ma (Fig. 8a,b) whereas the hornblende separates from the mafic dike samples display plateau ages of 54.39 ±0.74 and 53.43 ±0.58 Ma (Fig. 8 c,d). The 40Ar/39Ar

ages of the mafic dikes and adakitic porphyries are in close agreement with the

40Ar/39Ar

plateau age of the Orhaneli pluton reported by Altunkaynak et al. (2012b). This

evidence indicates that the mafic dikes, adakitic porphyries, and the Orhaneli pluton are coeval; thus, the studied mafic dikes are suggested to be syn-plutonic mafic dikes.

4. Discussion 4.1 Petrogenesis The studied porphyry dikes and stocks are mainly characterized by high SiO2 (63.8– 69.4 wt%), high Al2O3 (>15 wt%), high Sr (1129–1719 ppm), high LREEs, low Y (6–12 ppm), low HREEs and a lack of significant Eu anomalies (Eu/Eu* ≈ 0.9–1.11) (Figs. 5a-c, 6, 7a). These geochemical features are consistent with those of adakites, which are defined as melts developed by the partial melting of the subducted basaltic oceanic crust (Defant and Drummond, 1990; Martin et al., 2005). Accordingly, on the Sr/Y versus Y discrimination diagram, porphyry samples plot in the adakite field rather than the classical arc magmatic suites (Fig. 7a). In addition, all porphyries plot in the high-silica adakites (HSAs) field, which corresponds to slab-derived adakites (Fig. 7b) in the SiO2 versus MgO diagram of Martin et al. (2005). However, the studied rocks have relatively high K2O contents at 3.17–4.91 wt% and high K2O/Na2O ratios at 0.62–1.03 compared to those of adakites (Zhang et al., 2001; Moyen, 2007; Xiao and Clemens, 2007; Castillo, 2012). Moreover, our samples have remarkably higher ratios of Rb/Sr (0.08-0.14), (0.70625-0.70657),

207Pb/204Pb

i

87Sr/86Sr

i

(15.671-15.70) and lower Nd isotopic values (εNd(i): -2.94-

0.59) than those in the slab-derived adakites (Figs. 5b–d, 9a,b, 10). Overall, all of these geochemical and isotopic characteristics reveal that the studied porphyries can be considered as K-rich continental (C-type) adakites, which have been reported in continental settings around the world (e.g., Drummond et al., 1996; Huang et al., 2009; Karslı et al., 2010; Dokuz et al., 2013; Alirezaei et al., 2017; Azizi et al., 2019), rather than slabderived adakites. The N-MORB- and chondrite-normalized trace element abundances and the resultant high MREE/HREE, high LaN/YbN (35–81) and Sr/Y (20-215) ratios of our samples suggest derivation of their melt from a garnet-bearing source. Further, the absence of obvious

Eu anomalies and the enrichment of Sr demonstrate that the source was plagioclase-free and/or that plagioclase was not an important fractionating phase in the evolution of the adakitic porphyries (e.g., Rudnick and Fountain, 1995; Martin et al., 2005). Partial melting in the presence of garnet and the absence of plagioclase implies two possibilities: (1) partial melting of garnet amphibolite or eclogite facies rocks at the base of thickened continental crust or (2) partial melting of subducting oceanic crust, which would have been metamorphosed to eclogite or amphibolite facies in the zone of arc magma generation (e.g., Defant and Drummond, 1990; Thirlwall et al., 1994; Martin, 1999; Pearce et al., 2005; Casstillo, 2006, 2012; Ma et al., 2015). The K-rich C-type nature of our adakitic rocks, as discussed above, reveals that their melts were not formed by oceanic slab melting, which produces widespread “true” adakites. Therefore, origin from the mafic lower continental crustal seems more likely to produce this melt. However, although high-pressure melting of crustal garnet-bearing amphibolites or eclogites could explain the origin of the adakitic signatures (e.g., Atherton and Petford, 1993; Castillo et al., 2006; Garrison and Davidson, 2003; Macpherson et al., 2006; Chiaradia et al., 2009), experimental studies have shown that the resultant pure crustal melts are generally characterized by sodic and strongly peraluminous compositions and low Mg numbers (<40) (Patino Douce and McCarthy, 1998; Rapp and Watson, 1995), which are not the case for our porphyries. In contrast, the studied porphyries are metaluminous to slightly peraluminous and high-K-calc-alkaline rocks with variable Mg# of 14.6–54.5 (Fig 5d). These geochemical features and the high Sr-Pb and low Nd isotopic compositions of the studied rocks favour a formation from mixed melts derived from mantle and lower-crust (Figs. 9 and 10; e.g., Atherton and Petford, 1993; Petford and Gallagher, 2001; Castillo, 2006, 2012; Deng et al., 2018; and references therein), as discussed below. Eocene basaltic rocks (52–38 Ma) have been reported in both NE and NW Turkey (Gülmez et al., 2012; Altunkaynak and Dilek, 2013; Yücel et al., 2017). The genesis of these volcanic rocks

is attributed to mantle–crust interaction according to their geochemical and isotopic characteristics. In the study area, the adakitic porphyries host numerous MMEs (Figs. 3d and 4c) and coexist with contemporaneous mafic dikes. Thus, such a coeval felsic (adakitic porphyries) to mafic (MMEs and mafic dikes) association may support the input of mafic magmas in the felsic magma chambers (e.g., Barbarin, 2005; Clemens, 2003; He et al., 2016; Xiao et al., 2017). The influence of the magma mixing/mingling process of felsic and mafic magmas in the petrogenesis of our samples is petrographically evidenced by the complex zoning in the plagioclase phenocrysts and schiller inclusions along the zone line of plagioclase in the investigated porphyries (Fig. 4f, g). MMEs and mafic dikes are medium-to-high K calc-alkaline and metaluminous in nature and do not show an adakitic geochemical affinity. They have higher Mg#, CaO, Fe2O3, and TiO2, and lower SiO2 and K2O contents and Sr/Y ratios than adakitic porphyries (Figs. 5a, d, 6), indicating that they represent the more primitive compositions compared to porphyries. MMEs and mafic dikes have relatively high

87Sr/86Sr

i

(0.70541–0.70653) and

207Pb/204Pb

i

(15,6697-15,6934) ratios, and low ɛNdi values (-2.21– 0.69) with respect to the MORB, implying an enriched mantle source. On the other hand, their Sr-Nd-Pb isotopic compositions are similar to those of adakitic porphyries (Table 2, Figs. 9 and 10). This similarity in isotopic compositions indicates either a common mantle source or limited isotopic contrast between the mantle and crustal melts. At first glance, the association of the adakitic rocks and MMEs/mafic dikes may suggest that the fractional crystallization of the parental basaltic magma of MMEs and mafic dikes, which is represented by enriched mantle-derived melts, in this case, could be responsible for the generation of the studied porphyries. However, the geochemical patterns of MMEs/mafic dikes and porphyries, such as their discrete distribution defined by a compositional gap between 57 wt.% and 63 wt.% and different evolutionary trends on the Harker diagrams (Fig. 6) are unlikely to be explained by their generation from a single source.

Therefore, such a coeval felsic (adakitic porphyries) and mafic (MMEs and mafic dikes) association can be produced by variable degrees of heterogeneous mixing/mingling of the mantle- and crust-derived melts. Porphyries together with the associated microgranular enclaves/mafic dikes exhibit systematic co-variations nearly parallel to the crust vector line, which lies between fields of MORB, enriched mantle-derived Eocene mafic lavas and the lower crust (Fig. 9c). Similarly, it can be inferred from Fig. 10 that all samples have Pb isotopic compositions transitional between those of enriched mantle (EMII) and lower continental crust, which are significantly higher than those of the MORB values. These features suggest that the most probable mechanism for the generation of porphyries is mixing/mingling of the enriched mantle (EMII)- and lower crustderived magmas (Kemp et al., 2007; Deng et al., 2018) In the same area of NW Turkey, coeval acidic plutonic rocks are represented by medium- to high-K calc-alkaline, I-type granitoids accompanied by minor amounts of shoshonitic rocks with syenite compositions and MMEs (Altunkaynak et al., 2012b and references therein). This contribution of the lower crust to the mantle melts is consistently reported in the numeric models conducted on Topuk Pluton and Orhaneli Pluton (Altunkaynak et al., 2012b; Güraslan and Altunkaynak, 2019), which are spatially and temporally related to the studied adakitic porphyries. 4.2. Timing and causes of continental adakitic magmatism in NW Turkey The new

40Ar/39Ar

age data imply that the adakitic occurrences and mafic dikes were

emplaced coevally in the early Eocene (53.84 ± 0.16 to 53.70 ± 0.19 Ma and 54.39 ± 0.74 to 53.43 ± 0.58 Ma, respectively; Table 3; Fig. 8). These data demonstrate that the adakitic magmatic activity is spatially and temporally associated with Eocene granitic magmatism in NW Anatolia. Moreover, adakitic rocks in the eastern part of the Sakarya Zone have Eocene ages of 51–54 Ma (Karslı et al., 2011; Dokuz et al., 2013), which is comparable with our new

age data for the adakitic porphyries in the western part of the Sakarya Zone. The occurrence of coeval adakitic porphyries in both the eastern and western parts of the Sakarya Zone indicates that Eocene adakitic magmatism cannot be considered as a local feature, although they are rare with respect to the non-adakitic plutonic rocks. Eocene plutonic rocks (54–35 Ma) display a wide range of compositions, from diorite to granite, and minor shoshonitic and adakitic rocks. Generation of the Eocene magmatic suites has been attributed to the arc-related setting (e.g., Delaloye and Bingol, 2000; Okay and Satır, 2006; Ustaomer et al., 2009; Eyuboğlu et al., 2011). However, several geological and geochemical evidences strongly favour the post-collisional setting for the generation of Eocene magmatic successions. These evidences include: (1) Eocene granitoids intruded into the blueschists and ophiolitic rocks of the suture zone, marking the closure of the northern branch of Neo-Tethys and the SC crystalline basement, (2) both the IASZ and the Sakarya Zone are unconformably overline by Lower Eocene continental to shallow marine sedimentary rocks (Akdeniz, 1980; Akyurek and Soysal, 1983; Yılmaz, 1997), (3) several geochemical lines of evidence imply mantle upwelling beneath NW Anatolia. Our isotopic and geochemical findings together with radiometric age data point to the existence of continental (C-type) adakites in NW Anatolia and also provide significant proof of a post-collisional setting rather than an arc setting in the early Eocene. Recent studies on Cenozoic magmatic rocks in northern Turkey have questioned the heat source triggering the post-collisional magmatism. Many of them explain this post-collisional magma generation with decompressional melting driven either by partial removal/delamination of the subcontinental lithospheric mantle or by slab break-off and subsequent hot asthenospheric upwelling (Aldanmaz et al., 2000; Altunkaynak and Dilek, 2006; Altunkaynak 2007; Karslı et al., 2010; Altunkaynak et al., 2012a,b; Temizel et al., 2012; Arslan et al., 2013; Marchev et al., 2013; Aslan et al., 2014; Güraslan and Altunkaynak, 2019). The geochemical and isotopic

characteristics of studied continental adakites and mafic syn-plutonic dikes, and those of coeval plutonic and volcanic rocks in NW Anatolia indicate that Eocene magmatic rocks were formed from heterogeneously mixed melts derived from

enriched mantle and lower crust, and

increased mantle input in the late stages of Eocene magmatism (Altunkaynak and Dilek, 2013). These data support the asthenospheric upwelling beneath western Anatolia which led to partial melting in lower crust and mantle during the Eocene. Mantle upwelling caused by either slab break-off or partial delamination of the mantle lithosphere could generate magmatic rocks with similar geochemical features, reflecting mantle–crust melt interaction and also coeval felsic and mafic magmatic rocks (Bird, 1979; England and Houseman, 1989; Davies and Von Blanckenburg, 1995; Houseman and Molnar, 1997). Therefore, we infer that the partial melting in the mantle and the lower crust, which led to the generation of continental adakites, was caused by the upwelling asthenosphere as a result of breaking of the subducted Tethyan oceanic slab or partial removal of the base of the lithosphere during the early Eocene. Asthenospheric upwelling would raise the geothermal gradient beneath the suture zone and supplied heat flow to trigger the post-collisional magmatism in NW Turkey. Acknowledgments This research was supported by grants from TUBITAK (CAYDAG-110Y351) and Istanbul Technical University (BAP Project no. 40647) awarded to S.A. Special thanks are extended to Gülbin Kibaroğlu for providing help during the fieldwork and petrographical analyses. Alp Ünal, Ömer Kamacı, and people from Büyükorhan are appreciated for their contributions. Appreciation is extended to Dr. İbrahim Uysal in addition to Dr. Orhan Karslı and other reviewers for their efforts in improving this manuscript. Paul Sotiriou is also thanked for his contributions during the proofreading of the manuscript.

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Figure Captions Figure 1. (a) Major tectonic units of the East Mediterranean Region (Okay and Tüysüz, 1999) and the distribution of both Eocene magmatic associations along the northern Neo-Tethys suture zone (simplified from MTA 1:500000 scale geology map; Altunkaynak et al., 2012b) and the main production of the Cenozoic adakitic magmatism (modified from Gençoglu Korkmaz et al., 2017, and references therein); (b) simplified geological map of the Orhaneli pluton and its surrounding areas showing the distribution of adakite-like porphyries (modified from Altunkaynak, 2007). Figure 2. (a) Detailed geological map of the study area; (b) lines A–A′, B–B′ and D–D′ are the profile lines for the cross-sections. Figure 3. Field photographs from the adakite-like porphyry, mafic syn-plutonic dike, and mafic magmatic enclave (MME). (a) Intrusive contact between the adakite-like porphyry and basement rocks; (b) contact of adakite-like porphyry with granite and a xenolith represented by clasts of metamorphic basement rock included in the host rock; (c) adakite-like porphyry; (d) mafic magmatic enclave (MME) in an adakite-like porphyry; (e) mafic syn-plutonic dike; (f) mingled microdiorite and microgranodiorite. Figure 4. Micrographs illustrating the main petrographical features of the adakite-like porphyry, mafic syn-plutonic dike, and mafic magmatic enclave (MME). (a) Porphyritic texture of the adakite-like porphyry; (b) porphyritic texture of the mafic syn-plutonic dike; (c) holocrystalline microgranular–porphyritic texture of the MME; (d) cumulate texture; (e) serizitation on K-feldspar phenocrysts; (f) zoned plagioclase phenocrysts; (g) schiller inclusions along the zone line of host plagioclase; (h) corroded plagioclase phenocrysts. Q: quartz; Kf: Kfeldspar; Bio: biotite; Plg: plagioclase; Amp: amphibole; Ser: sericitization; Inc: inclusion; Cum: cumulate texture. Figure 5. Plot of adakite-like porphyry, mafic syn-plutonic dike, and mafic magmatic enclave (MME) on the (a) total alkali versus SiO2 classification diagram; (b) K2O versus SiO2 (Peccerillo and Taylor, 1976); (c) A/CNK versus A/NK diagram (Shand, 1949); (d) Mg# versus SiO2 diagram. Alkaline/subalkaline classification line from Irvine and Baragar (1971). Crustal assimilation and fractional crystallization (AFC) line taken from Stern and Kilian (1996). The data fields for subduction-related adakites and continental adakites (C-adakites) are from published data (Sen and Dunn, 1994; Rapp and Watson, 1995; Springer and Seck, 1997; Rapp et al., 1999; Skjerlie and Patiño Douce, 2002; Defant and Drummond, 1990; Kay et al., 1993; Drummond et al., 1996; Sajona et al., 2000; Aguillon-Robles et al., 2001; Stern and Kilian, 1996; Martin et al., 2005; Xu et al., 2002; Gao et al., 2004; Wang et al., 2006; Karsli et al., 2010; Guan et al., 2012; Hu et al., 2017, and references therein). Figure 6. Major elements versus SiO2 Harker variation diagrams for the adakite-like porphyry, mafic syn-plutonic dike, and mafic magmatic enclave (MME). Figure 7. Adakite discrimination diagrams (a and b) and trace element distribution diagrams (c and d) for the adakite-like porphyry, mafic syn-plutonic dike, and mafic magmatic enclave (MME). (a) Sr/Y versus Y diagram following Defant and Drummond (1990); (b) SiO2 versus MgO diagram showing high silica adakite (HSA) and low silica adakite (LSA) fields (Martin et al., 2005); (c) Chondrite-normalized rare earth element diagram; (d) normal mid-ocean ridge basalt (N-MORB)-normalized trace element diagram. The N-MORB and Chondrite

normalizing values are from Boynton (1984) and Sun and McDonough (1989), respectively. The pure slab melt data are from Kepezhinskas et al. (1995) and Sorensen and Grossman (1989). The data fields for subduction-related adakites and continental adakites (C-adakites) are from published data listed in Fig. 5. Figure 8. 40Ar/39Ar plateau age spectra of adakite-like porphyry and mafic syn-plutonic dike. Plateau steps are shown in white and the rejected steps are shown in black. Figure 9. Process-identification diagrams for adakite-like porphyry, mafic syn-plutonic dike, and mafic magmatic enclave (MME). (a) Th/Yb versus Th/Sm diagram (Zhu et al., 2009). The data fields for subduction-related adakites and continental adakites (C-adakites) are from published data listed in Fig. 5. (b) ƐNd(54) versus 87Sr/86Sr(54) diagram. Data of the Late Mesozoic adakitic magmatism are from Genc and Kayacı (2012), Delibaş et al. (2016); and Yılmaz Şahin et al. (2012). Cenozoic adakitic magmatism is from Varol et al. (2007), Şen and Şen (2013), Kadioglu and Dilek (2010), Topuz et al. (2005, 2011), Karsli et al. (2010, 2011), Dokuz et al. (2013). Data for Eocene Granitoid and Eocene mafic lavas are from Altunkaynak et al. (2012b) and from Altunkaynak and Dilek (2013), respectively. Other data is from Altunkaynak et al. (2012a) and references therein. Figure 10. 207Pb/204Pb versus 206Pb/204Pb diagram for adakite-like porphyry, mafic syn-plutonic dike, and mafic magmatic enclave (MME). The Slab derived adakites and Adak island adakites are from Stern and Kilian, (1996); Kay et al. (1993) and Aguillón-Robles et al. (2001). The Northern Hemisphere Reference Line (NHRL) is from Hart (1984). The fields for the midocean ridge basalt (MORB), EMI and EMII are taken from Zindler and Hart (1986), Lu et al. (2013), Oh et al. (2016) and references therein. The data fields for lower and upper continental crusts are from published data listed in Fig. 5. Data for potassic adakite-like rocks (W Yunnan) is from Lu et al. (2013). EMI: enriched mantle I; EMII: enriched mantle II. Table captions Table 1. Representative chemical analyses of adakite-like porphyry, mafic syn-plutonic dike, and mafic magmatic enclave (MME). Marked samples (i.e. 6*) obtained from our previously published study (Altunkaynak et al., 2012b). Fe2O3(t): total iron as Fe2O3; LOI: loss on ignition; Eu/Eu*= EuN / (SmN * GdN)0.5; bdl: below detection limit; dl: detection limit. Table 2. Representative isotopic analyses (87Sr/86Sr, 143Nd/144Nd, 206Pb/204Pb, 207Pb/ 204Pb, 208Pb/204Pb) of adakite-like porphyry, mafic syn-plutonic dike, and mafic magmatic enclave (MME). The 87Sr/86Sr and 143Nd/144Nd isotopic compositions are from our previous study (Altunkaynak et al., 2012b). Table 3. 40Ar/39Ar plateau age data of the adakite-like porphyry and mafic syn-plutonic dike.

Graphical abstract

Highlights 40Ar/39Ar ages of Adakitic porphyries range from 53.84±0.16 and 53.70±0.19 Ma. Adakitic porphyries can be considered as K-rich continental (C-type) adakites. Generation of adakitic porphyries is likely related to intraplate tectonic settings. Adakitic magma generation was caused by upwelling asthenosphere.

Table 1. Sample No

SiO2 Al2O3 Fe2O3(t) MgO CaO Na2O K2O TiO2 P2O5 MnO Cr2O3 Sc LOI Sum Ba Be Co Cs Ga Hf Nb Rb Sn Sr Ta Th U V W Zr Y La Ce Pr Nd Sm Eu Gd Tb Dy Ho Er Tm Yb Lu Cu Pb Ni Eu/Eu* LaN/YbN Sr/Y

66

84

73

103

88

106

10

dl

Porphyry

Porphyry

Porphyry

Porphyry

Porphyry

MME

MME

0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.00 0.10 0.01

67.99 16.64 2.03 0.81 2.63 5.03 3.17 0.27 0.09 0.02 bdl 3.00 1.00 99.68 1217.0 3.0 3.7 2.0 19.5 4.4 7.9 110.2 1.0 1313.0 0.5 16.6 4.3 32.0 bdl 149.8 6.2 31.3 60.6 5.8 19.5 3.1 0.9 2.2 0.3 1.3 0.2 0.7 0.1 0.5 0.1 1.3 13.3 5.3 1.05 39.82

67.59 15.99 1.86 0.60 1.64 4.89 4.52 0.26 0.12 0.01 bdl 2.00 2.10 99.54 1831.0 5.0 2.5 5.1 19.3 5.6 14.6 176.3 1.0 1719.4 0.8 36.1 6.1 24.0 bdl 227.1 8.0 77.3 133.9 12.9 41.5 6.0 1.4 3.6 0.5 1.6 0.3 0.7 0.1 0.7 0.1 0.9 14.9 6.4 0.94 80.18

67.08 16.24 2.23 0.40 1.37 5.17 4.74 0.27 0.15 0.02 bdl 3.00 1.70 99.39 2935.0 5.0 2.3 3.3 21.7 7.2 14.6 148.9 2.0 1693.1 0.7 38.6 8.4 27.0 bdl 285.3 12.8 112.3 177.8 17.3 56.6 8.6 2.2 5.3 0.7 2.9 0.4 1.3 0.2 0.9 0.1 1.9 17.6 5.5 0.98 81.41

64.72 16.93 3.75 1.61 4.55 3.77 2.20 0.40 0.17 0.07 0.00 7.00 1.60 99.76 866.0 bdl 6.3 2.5 17.6 4.4 9.5 70.9 1.0 664.8 0.7 10.4 2.7 59.0 bdl 160.3 18.2 31.9 61.7 7.0 24.7 4.3 1.1 3.6 0.6 3.0 0.7 1.8 0.3 1.7 0.3 0.6 1.7 3.8 0.83 12.73

69.41 15.86 1.97 0.19 0.96 4.79 4.91 0.22 0.07 0.03 bdl 2.00 1.20 99.57 1713.0 7.0 2.9 6.7 21.7 7.7 28.0 184.6 2.0 1306.8 1.2 42.2 5.8 21.0 0.9 253.8 9.9 84.4 148.3 17.8 56.5 8.2 1.8 4.9 0.6 2.4 0.3 0.9 0.1 0.9 0.1 5.6 5.9 3.1 0.87 65.40

54.11 17.18 7.23 3.69 6.86 6.27 1.27 0.78 0.54 0.15 0.00 13.00 1.10 99.17 1485.0 12.0 20.0 2.3 21.6 7.3 24.0 24.8 2.0 3702.7 0.9 28.4 8.7 147.0 bdl 314.8 26.1 140.6 277.5 32.0 116.7 17.9 4.3 11.3 1.3 5.9 1.0 2.2 0.3 2.0 0.3 8.2 18.8 8.0 0.93 46.70

53.71 18.56 7.14 3.48 7.65 4.24 1.52 0.62 0.15 0.30 0.00 21.18 2.25 99.62 284.9 1.2 17.7 2.3 18.8 2.1 4.7 74.9 2.1 289.9 0.3 2.6 1.3 167.8 bdl 83.0 22.5 9.8 24.5 3.3 13.2 3.4 1.1 3.8 0.6 3.5 0.8 2.3 0.4 2.3 0.4

211.77

214.92

132.27

36.52

132.00

141.86

12.86

1.00 1.00 0.20 0.10 0.50 0.10 0.10 0.10 1.00 0.50 0.10 0.20 0.10 8.00 0.10 0.10 0.10 0.10 0.10 0.02 0.30 0.05 0.02 0.05 0.01 0.05 0.02 0.03 0.01 0.05 0.01 0.50 0.10 0.10

8.6 0.95 2.89

Sample No

SiO2 Al2O3 Fe2O3 MgO CaO Na2O K2O TiO2 P2O5 MnO Cr2O3 Sc LOI Sum Ba Be Co Cs Ga Hf Nb Rb Sn Sr Ta Th U V W Zr Y La Ce Pr Nd Sm Eu Gd Tb Dy Ho Er Tm Yb Lu Cu Pb Ni Eu/Eu* LaN/YbN

6*

14*

20*

59*

63*

4-ORH*

6-ORH*

32-ORH*

Porphyry

Porphyry

Porphyry

Porphyry

Porphyry

Porphyry

Porphyry

Porphyry

68.19 16.39 1.87 0.58 1.81 4.79 4.35 0.25 0.10 0.01 bdl 2.00 1.20 99.55 1873.0 4.0 3.0 4.3 20.5 6.1 14.7 157.5 1.0 1607.9 0.8 31.4 5.0 28.0 0.8 223.0 9.5 74.1 130.2 12.9 45.3 6.3 1.6 3.6 0.5 1.9 0.3 0.8 0.1 0.8 0.1 1.3 2.8 3.1 1.0 63.2

67.25 16.12 2.17 0.74 2.43 4.83 3.54 0.29 0.12 0.02 bdl 3.00 2.10 99.60 1526.0 4.0 3.2 3.3 18.9 5.2 13.4 161.9 1.0 1529.2 0.7 29.3 3.7 37.0 1.8 207.5 8.7 67.7 124.0 11.9 40.8 5.7 1.4 3.5 0.4 1.7 0.3 0.8 0.1 0.7 0.1 1.3 2.3 3.0 0.9 66.2

68.04 16.31 2.15 0.70 2.06 4.61 3.62 0.26 0.11 0.02 bdl 2.00 1.80 99.64 1485.0 4.0 2.4 4.1 19.3 4.9 11.1 129.9 1.0 1300.1 0.6 25.1 4.8 28.0 bdl 183.0 8.6 43.5 78.6 8.3 28.4 4.3 1.2 2.8 0.4 1.6 0.3 0.8 0.1 0.8 0.1 1.2 7.6 3.3 1.1 35.3

68.34 16.45 1.68 0.64 1.44 5.56 3.47 0.26 0.09 <0.01 bdl 3.00 1.80 99.70 1262.0 4.0 0.8 3.3 18.6 4.1 7.5 149.9 1.0 1205.8 0.4 15.4 3.4 25.0 bdl 144.9 6.3 31.4 51.6 5.7 18.6 2.9 0.8 2.0 0.3 1.3 0.2 0.6 0.1 0.5 0.1 1.6 18.5 3.0 1.0 39.2

67.07 16.45 2.16 0.83 2.23 4.83 4.06 0.28 0.13 0.03 bdl 3.00 1.50 99.59 1582.0 4.0 3.4 5.5 19.4 4.7 10.8 153.3 1.0 1500.6 0.6 29.5 4.9 31.0 bdl 193.6 8.2 68.2 123.4 11.5 39.3 5.3 1.3 3.2 0.4 1.6 0.3 0.7 0.1 0.7 0.1 1.1 15.8 5.7 0.9 68.6

68.57 15.74 1.88 0.59 2.37 4.80 3.67 0.24 0.09 0.88 bdl 3.00 0.88 98.86 1583.0 4.0 3.0 3.6 19.0 4.2 8.0 124.0 5.0 1262.0 0.5 24.3 4.8 bdl bdl 165.0 9.0 46.3 81.2 9.0 32.8 5.2 1.3 3.1 0.4 1.8 0.3 0.9 0.1 0.8 0.1 40.0 19.0 bdl 1.0 39.0

69.43 15.44 2.01 0.59 2.20 4.64 3.59 0.24 0.11 0.69 bdl 3.00 0.69 98.96 1538.0 3.0 3.0 4.1 19.0 4.6 10.0 120.0 1.0 1164.0 0.6 23.8 4.0 bdl bdl 178.0 8.0 55.0 97.8 10.3 36.2 5.4 1.3 3.2 0.4 1.6 0.3 0.8 0.1 0.7 0.1 bdl 27.0 bdl 1.0 53.0

68.64 16.36 2.14 0.73 2.18 4.70 3.63 0.27 0.11 1.33 bdl 3.00 1.33 100.10 1666.0 3.0 3.0 5.3 20.0 4.5 10.0 121.0 1.0 1235.0 0.6 23.7 3.6 bdl bdl 180.0 9.0 49.8 87.2 9.7 34.6 5.3 1.4 3.1 0.4 1.7 0.3 0.8 0.1 0.7 0.1 bdl 22.0 bdl 1.0 48.0

Sr/Y

169.3

175.8

151.2

Sample No

17*

100a*

OR-76*

Porphyry SiO2 Al2O3 Fe2O3 MgO CaO Na2O K2O TiO2 P2O5 MnO Cr2O3 Sc LOI Sum Ba Be Co Cs Ga Hf Nb Rb Sn Sr Ta Th U V W Zr Y La Ce Pr Nd Sm Eu Gd Tb Dy Ho Er Tm Yb Lu Cu Pb Ni

63.80 16.46 3.34 1.90 3.85 4.39 3.55 0.42 0.21 0.04 0.00 7.00 1.70 99.62 1295.0 4.0 8.5 4.9 20.2 5.0 9.4 151.0 2.0 1304.0 0.6 22.7 5.8 62.0 bdl 183.4 11.5 63.3 114.7 11.3 39.0 5.5 1.4 3.6 0.5 2.0 0.4 1.2 0.2 1.1 0.2 2.4 4.1 12.5

Porphyry 65.57 16.16 2.94 1.51 3.47 3.94 3.60 0.34 0.16 0.05 0.00 5.00 1.90 99.66 1243.0 2.0 7.4 3.9 19.4 4.8 10.5 133.1 bdl 1129.7 0.6 20.4 3.9 46.0 0.9 192.9 9.9 49.6 88.9 9.7 32.6 5.1 1.2 3.4 0.4 1.8 0.4 1.0 0.2 0.9 0.1 1.4 4.9 10.4

Porphyry 64.76 16.81 4.54 1.79 5.40 4.02 2.01 0.44 0.14 0.10 bdl 6.12 0.49 100.50 558.0 bdl 12.0 0.9 2.9 8.5 66.0 bdl 427.0 0.6 8.9 1.8 74.0 107.0 21.0 29.5 58.8 4.5 19.2 3.4 1.0 3.2 0.5 2.9 0.6 1.9 0.3 1.9 0.3 bdl 7.9 bdl

191.4

183.0

140.2

57*

87*

100b*

Mafic synplutonic dike

Mafic synplutonic dike

Mafic synplutonic dike

57.17 16.19 5.56 4.93 6.83 3.72 2.34 0.62 0.33 0.10 0.02 19.00 1.80 99.63 868.0 2.0 19.5 2.4 17.0 4.4 10.2 82.8 1.0 1067.1 0.6 14.5 2.7 148.0 bdl 167.5 17.9 55.0 109.5 11.2 41.3 6.9 1.7 4.9 0.7 3.3 0.7 1.8 0.3 1.8 0.3 38.6 1.5 18.5

57.95 15.66 5.42 5.16 6.61 3.67 2.39 0.56 0.18 0.10 0.02 22.00 1.90 99.61 967.0 3.0 21.1 2.0 15.5 3.5 7.7 86.9 1.0 1329.2 0.5 11.3 2.9 162.0 bdl 130.4 15.6 38.3 68.8 7.3 27.2 4.6 1.2 3.6 0.6 2.7 0.6 1.8 0.3 1.7 0.3 10.3 9.9 15.5

54.73 16.15 5.40 5.50 6.36 3.55 2.65 0.61 0.34 0.10 0.03 16.00 4.20 99.61 1073.0 2.0 20.6 2.3 17.2 3.8 8.2 84.4 1.0 1042.7 0.5 15.8 3.0 119.0 1.1 154.8 14.1 54.0 106.3 12.2 43.9 7.1 1.8 4.9 0.6 2.9 0.5 1.4 0.2 1.3 0.2 1.9 2.2 49.8

145.5

137.2

Eu/Eu* LaN/YbN Sr/Y

0.9 39.9 113.4

0.9 37.6 114.1

0.9 10.3 20.3

0.9 20.8 59.6

0.9 14.9 85.2

0.9 28.0 74.0

Table 2. Sample No

87Sr/86Sr

14 Adakitic Porphyry

(m)

87Sr/86Sr

i

143Nd/143Nd 143Nd/144Nd

(m) i

EpsNdi 206Pb/204Pb 206Pb/204Pb

(i)

207Pb/204Pb 207Pb/204Pb

(i)

208Pb/204Pb 208Pb/204Pb

(i)

20 Adakitic Porphyry

59 Adakitic Porphyry

63 Adakitic Porphyry

4-ORH Adakitic Porphyry

6-ORH Adakitic Porphyry

32-ORH Adakitic Porphyry

100a 100b Adakitic Mafic synPorphyry plutonic dike

0.70648

0.7066

0.70685

0.70678

0.70656

0.70648

0.70651

0.70679

0.70671

0.70625

0.70638

0.70657

0.70656

0.70634

0.70626

0.70629

0.70653

0.70653

0.51251

0.51256

0.51263

0.51245

0.51247

0.51246

0.5125

0.51256

0.51249

0.51248

0.51253

0.5126

0.51242

0.51243

0.51243

0.51247

0.51253

0.51246

-1.8

-0.71

0.59

-2.94

-2.66

-2.73

-1.91

-0.77

-2.21

19.3404

19.0052

18.9370

18.9840

19.2583

19.0543

19.0618

19.0108

19.1453

18.4543

18.6614

18.8373

18.8153

19.1205

18.9734

18.9723

18.5774

18.4000

15.7130

15.6999

15.6959

15.6990

15.7069

15.6973

15.6988

15.6995

15.7048

15.6713

15.6837

15.6912

15.6910

15.7004

15.6935

15.6946

15.6791

15.6697

39.7862

39.2519

39.0916

39.2165

39.1082

39.3916

39.5386

39.2659

39.3995

37.4801

38.6610

38.9431

38.8827

38.8790

39.2335

39.3450

38.5208

38.1095

Table 3. Sample

MG-6

MG-4

MG-100b

MG-57

Adakite-like Adakite-like porphyry porphyry

Mafic synplutonic dike

Mafic synplutonic dike

Rock

Mineral

Biotite

Biotite

Hornblende

Hornblende

MSWD

1.45

1.03

0.83

0.96

50.86

53.71

53.78

50.50

0.19

0.17

0.87

1.38

53.70

53.84

53.43

54.39

0.29

0.16

0.58

0.74

Age Total gas ± age (Ma) 2σ Age Plateau ± age (Ma) 2σ