Petrogenesis and W-Mo fertility indicators of the Gaojiabang “satellite” granodiorite porphyry in southern Anhui Province, South China

Accepted Manuscript Petrogenesis and W-Mo fertility indicators of the Gaojiabang “satellite” granodiorite porphyry in southern Anhui Province, South China Dayu Zhang, Taofa Zhou, Feng Yuan, Yu Fan, Xuefeng Chen, Noel C. White, Ning Ding, Qisheng Jiang PII: DOI: Reference:

S0169-1368(17)30182-8 http://dx.doi.org/10.1016/j.oregeorev.2017.03.006 OREGEO 2144

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Ore Geology Reviews

Received Date: Revised Date: Accepted Date:

2 December 2016 2 March 2017 7 March 2017

Please cite this article as: D. Zhang, T. Zhou, F. Yuan, Y. Fan, X. Chen, N.C. White, N. Ding, Q. Jiang, Petrogenesis and W-Mo fertility indicators of the Gaojiabang “satellite” granodiorite porphyry in southern Anhui Province, South China, Ore Geology Reviews (2017), doi: http://dx.doi.org/10.1016/j.oregeorev.2017.03.006

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1

Petrogenesis and W-Mo fertility indicators of the Gaojiabang

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"satellite" granodiorite porphyry in southern Anhui Province,

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South China

4

Dayu Zhang1, Taofa Zhou1* , Feng Yuan1, Yu Fan1, Xuefeng Chen1, Noel C. White1, Ning

5

Ding2, Qisheng Jiang3

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1. School of Resources and Environmental Engineering, Hefei University of Technology, Hefei 230009,

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China

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2. Geological Survey of Anhui Province, Hefei 230001, China

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3 No. 812 Geological Party, East China Metallurgical Prospecting Bureau of Anhui Province, Tongling

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244002, China

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*Corresponding Author: [email protected]

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Abstract: The Gaojiabang W-Mo mineralized granodiorite porphyry occurs as a “satellite”

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intrusion on the northern margin of the Qingyang-Jiuhua pluton in southern Anhui

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Province, South China. The geology, mineral and whole-rock geochemistry of the

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granodiorite porphyry is I-type and formed from a reduced melt. The Gaojiabang

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mineralized granodiorite porphyry was derived from the transition zone between the lower

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crust and upper mantle, and underwent high-degree fractional crystallization during

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emplacement. There is no obvious genetic relationship between the granodiorite porphyry

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and the granodiorite pluton of the Qingyang-Jiuhua plutonic complex. The key

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characteristics of the W-Mo mineralized Gaojiabang granodiorite porphyry include: 1)

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small volume (<0.5 km 3), 2) an abundance of hornblende (>5 vol. %), 3) low ∑REE

24

concentrations (145.50~159.46 ppm) accompanying weak negative Eu anomalies

25

(0.85~0.94), 4) high differentiation-indices degree and water contents, and 5) low oxygen

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fugacity. These criteria can be used to identify potential W-Mo mineralized intrusions in

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southern Anhui Province, South China.

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Key word: Petrogenesis; W-Mo metallogenesis; "Satellite" granodiorite porphyry; 1 / 30

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Southern Anhui Province, South China

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1 Introduction

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Tungsten-molybdenum metal resources have been widely explored in southern Anhui

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Province (SAP) in recent decades; with more than fifty deposits or occurrences

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containing >300,000 tons of WO3 having been discovered (Ding, 2012; Geological Survey

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of Anhui Province, 2011). W-Mo deposits in the SAP include Gaojiabang (Jiang et al.,

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2009; Fan et al., 2015), Baizhangyan (Ding, 2012), Jitoushan (Song, 2010) and

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Guilingzheng (Fan, 2015) all around the Qingyang-Jiuhua plutonic complex, and

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Lanhualing (Chen et al., 2014) and Xiwukou (Ding, 2012) around the Jinde plutonic

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complex. The identified W-Mo deposits are genetically related to porphyritic intrusions that

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occur as “satellites” around large plutonic complexes (Ding, 2012). A number of possible

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genetic relationships between the large plutons and the “satellite” porphyries have been

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proposed, including: (1) the porphyries were derived from the pluton (“mother-child type”

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Burnham,1979; Shinohara et al.,1995,1997; Richards, 2003, 2005); (2) both porphyries

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and plutons were sourced from the same deep plutons (“brothers type” Zhu et al., 2005;

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Wang et al. 2012; Zhang et al., 2016), and (3) both intruded in the same temporal and

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spatial setting, but had distinct sources and evolutionary processes (Zhang et al., 2015,

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2017; Guo, 2010; Ren et al., 2015).

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Previous researches have studied the geological characteristics (Jiang et al., 2009;

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Geological Survey of Anhui Province, 2011), geochronology (Zhou et al., 2012; Fan et al.,

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2016), and mineralization (Song, 2010, Zhou et al., 2005) of these SAP W-Mo deposits.

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However, the petrogenesis of the “satellite” porphyritic granitoids and the relationship

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between the mineralized porphyries and the plutonic complexes remain unclear. Moreover,

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there is little publication on the SAP W-Mo enriched indicators of those mineralized

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granitoid porphyries. The Gaojiabang granodiorite porphyry is located on the north to the

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Qingyang-Jiuhua plutonic complex, northern part of the SAP (Jiang et al., 2009), which

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provides us a rare example to investigate the possible relationship between the “satellite”

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W-Mo mineralized granodiorite porphyry and the barren granodiorite pluton. 2 / 30

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In this study, we focused on the Gaojiabang “satellite” W-Mo mineralized granodiorite

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porphyry. Combined with data from previous studies (Jiang et al., 2009; Fan, 2015), we

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investigated the petrogenesis and W-Mo enriched indicators of the Gaojiabang “satellite”

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porphyry through an integrated analysis of the geology, mineralogy and whole-rock

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geochemistry. These results not only contribute to our understanding of the genesis of the

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Gaojiabang granodiorite porphyry and associated W-Mo mineralization, but also provide

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evidence of the relationships between the “satellite” granitoid porphyry intrusions and the

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large plutonic complexes in southern Anhui Province.

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2 Geologic Characteristics

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2.1 Regional geology

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The southern Anhui Province (SAP) of South China is defined as the Anhui provincial

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administrative region south of the Yangtze River. Geologically, the SAP is located in the

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north part of the lower Yangtze continental terrene, and is characterized by

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Mesoproterozoic-early Paleozoic strata intruded by Mesozoic (150-120 Ma, Wu et al.,

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2012) granitoid plutons (Fig. 1a). The SAP divided into the into two parts by the

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ENE-trending Jiangnan deep fault (Fig. 1a), with the Jiangnan uplift belt on the southeast

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and, Jiangnan transition belt (JTB, Chang et al., 1991) in the northwest. The Jiangnan

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uplift belt consists of a Mesoproterozoic metamorphic basement intruded by both

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Neoproterozoic (~900-760 Ma) and Mesozoic (150-120 Ma) granitoids. The Jiangnan

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transition belt (JTB) is characterized by Early Paleozoic sedimentary strata intruded by

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Mesozoic (150-120 Ma) granitoids.

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There are numerous granitoid intrusions in the JTB, including the Qingyang-Jiuhua

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plutonic complex (145-120 Ma, Wu et al., 2012, Fan et al., 2016), and the Tanshan (127.3

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±2.1 Ma, Song et al., 2014), Huayuangong (125.3±1.2 Ma, Li et al., 2011), Maotan

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(127.7±1.8 Ma, Peng et al., 2012), Yinkeng (140.1±2.1 Ma, Wu et al., 2012), Yunling

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(128.7±1.5 Ma, Wu et al., 2012) plutons. The JTB plutons are 10-1000 km 2 in area, and

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mainly comprise granodiorite and granite (Fig. 1b). As the largest pluton in the JTB, the 3 / 30

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Qingyang-Jiuhua plutonic complex is ellipsoid in shape, and has an area of about 860 km 2.

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Around the Qingyang-Jiuhua plutonic complex, many W-Mo prospects have been

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explored, including Gaojiabang, Yangmeiqiao, Longtoushan, Baizhangyan, Shitan,

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Dilingjiao, Qianjia, Laoshan, Xinling, Jinjijian, Jitoushan, Guilingzheng, Fanjiaqiao,

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Sanxingshan, Tongkuangli and Shibanqiao (Fig. 1b).

92 93

2.2 Geology of the Gaojiabang W-Mo deposit

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The Gaojiabang W-Mo deposit is located at the northern margin of the

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Qingyang-Jiuhua plutonic complex; it contains a WO3 resource of 62,000 tons (0.367 %)

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and a Mo resource of 5,400 tons (0.106% Jiang et al., 2009). In the Gaojiabang mining

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district, Cambrian to Permian marine sedimentary strata are exposed (Fig. 1c). The

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granodiorite pluton has an emplacement contact with the Huangboling Formation as

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circular-arc shape (Fig. 1c). The granodiorite porphyry at the margin of the granodiorite

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pluton intruded into the Huangboling Formation and has an area of less than 0.5 km 3 (Fig

101

1d).

102

Based on the No. 36 line exploration profile, the orebodies occur in a zone of skarn

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mineralization between the Cambrian Huangboling Formation carbonates and mineralized

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granodiorite porphyry (Fig. 1d). The orebodies are subdivided into upper and lower parts,

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which are dominantly enriched with W and Mo respectively. The upper (No. 1) ore body is

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lensoid, with a length of 1800 m and a width of 1.6-48.0 m (avg. 13.87 m). It occurs in the

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middle-upper Huangboling Formation. The lower (No. 2) occurs in the lower Huangboling

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Formation.

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3 Sampling and Analytical methods

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3.1 Sampling and Petrography

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Ninety-three representative drill cores samples (including igneous rocks and ores)

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were selected for geological investigation from drilling holes ZK202 (29 samples), ZK366

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(41 samples) and ZK506 (23 samples) in the Gaojiabang W-Mo deposit. Besides ore or 4 / 30

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alteration rocks (54 samples), the rest ones include both mineralized granodiorite

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porphyry (9 samples) and barren granodiorite (30 samples). The magmatic rocks are

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described as follows.

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The granodiorite porphyry is grey and medium-coarse grained with a porphyritic

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texture (Fig. 2a, b). The porphyritic minerals are K-feldspar, plagioclase and quartz, with

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minor hornblende, biotite and clinopyroxene. Potassium-feldspar and plagioclase grains

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are the dominant phenocrysts, comprising about 60 vol. %; they are euhedral to subhedral

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in shape and 0.1~1.5 mm in size. A small quantity of mafic phenocrysts disseminated in

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the rock, include hornblende (~6 vol. %), biotite (~3 vol. %) and clinopyroxene (~1 vol. %),

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ranging from 0.1-0.5 mm. Zircon, pyrite, pyrrhotite and monazite grains occur as

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accessory minerals. The matrix consists of fine-grained feldspar and quartz, comprising

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about 25 vol. %. Sericitization and weak potassic alteration occurred in the granodiorite

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porphyry, where pyrite, pyrrhotite, scheelite and molybdenite are sparsely distributed.

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The granodiorite is grey and medium-coarse grained (Fig. 2c). The main phenocrysts

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are K-feldspar, plagioclase and quartz, with minor biotite. Both K-feldspar and plagioclase

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phenocrysts are euhedral to subhedral in shape and 0.2-1 mm in size (Fig. 2d),

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comprising about 85 vol. %. Quartz occurs as anhedral grains, filling the gaps between

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the K-feldspar and plagioclase grains, and occupies ~6 vol. %. Biotite occurs as anhedral

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sheets, and comprises about 3 vol. %. Hornblende, clinopyroxene and magnetite crystals

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are sparsely distributed in the rock. The granodiorite contains hydrothermal K-feldspar

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and epidote, but lacks sulfide minerals.

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3.2 Analytical methods

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After geological and petrographic investigations, five granodiorite porphyry samples

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were chosen for EPMA analysis, and seven representative samples from both the

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granodiorite porphyry (3 samples) and the granodiorite pluton (4 samples) were selected

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for whole-rock geochemical analysis to enable us to better understand the genetic

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relationship between the granodiorite porphyry and granodiorite pluton.

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(1) EPMA analysis

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Minerals were analyzed using a JAX-8230 electron microprobe in the Department of 5 / 30

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Geology, School of Resource and Environmental Engineering, Hefei University of

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Technology, China. The operating conditions were 15 kV accelerating voltage and 12 nA

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beam current. Mineral formulae of feldspar, biotite, hornblende and clinopyroxene have

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been calculated on the basis of 8, 12, 23 and 6 oxygens respectively. The detailed EPMA

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analytical method is from Shi (2016b). The EPMA results of the representative mineral

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compositions are listed in Table 1.

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(2) Whole-rock geochemical analysis

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The selected representative, least-altered samples were crushed to <200 mesh using

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an agate mill in the geological laboratory of the Hefei University of Technology. The whole

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rock major and trace element analyses were carried out at the ALS Global Analytical

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Company, Guangzhou, China. Major elements were analyzed using X-ray fluorescence

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spectroscopy (Norrish and Chappell, 1977). Ferric and ferrous iron ratios were determined

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by wet chemical methods. Trace element abundances, including the rare earth elements

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(REE), were determined by ICP-MS with a Finnegan MAT Element II mass spectrometer.

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The samples were digested with a mixture of HF and HNO3 acids in screw-top PTFE-lined

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stainless steel bombs at 185°C for 48 h, and any residues were dissolved in HNO3 at

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145°C for 3 hours to ensure complete digestion. Details of the analytical method used are

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described by Li et al. (2008) and Dulski (1994). Analysis of the Chinese basalt standard

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GSR-3 (Xie et al., 1989) indicates that the precision and accuracy of the major-element

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data are better than 3% and ca. 5% (2 sigma), respectively. The analytical precision of

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ICP-MS analysis was better than ±5% based on analysis of the USGS BHVO-1 standard.

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4 Results

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4.1 Mineral chemistry

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The EPMA research focused on the main silicate minerals in the granodiorite

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porphyry, including feldspar, biotite, hornblende and clinopyroxene. The results are as

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follows.

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(1) Feldspar 6 / 30

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The EPMA chemistry data of the feldspar minerals (both plagioclase and K-feldspar,

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Fig. 2e, f) are listed in Table 1. The plagioclase exhibit clear zonation (Fig. 2e) and are

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characterized by contents of SiO2 (59.56~72.45 wt. %), CaO (0.12~7.58wt. %), Al 2O3

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(18.54~25.55 wt. %) and Na2O (7.10~11.47 wt. %). The An and Ab values of the

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plagioclase are 0.57~36.86 and 62.40~98.69 respectively, which are mainly plotted into

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the oligoclase to albite fields (Fig. 3a). The K-feldspar are characterized by contents of

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SiO2 (64.51~66.09 wt. %), Al2O3 (17.58~18.10 wt. %), Na2O (0.35~1.47 wt. %) and K2O

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(11.93~15.01 wt. %). The Or and Ab values are 83.89~96.34 and 3.66~15.68 respectively,

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and thus lie in the orthoclase series field (Fig. 3a).

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(2) Biotite

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The EPMA data for biotite in the Gaojiabang granodiorite porphyry are shown in Table

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1. Their SiO2 and FeO contents range from 39.77 to 40.89 wt. % and 11.04 to 15.19 wt. %,

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respectively. Biotite geochemical indicators (e.g. MF, Fe3+, Fe2+, Mg) were calculated

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through the method reported by Lin et al. (1994), which are plotted into the ferrous biotite

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field (Fig. 3b).

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(3) Hornblende

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The EPMA data for hornblende in the Gaojiabang granodiorite porphyry are shown in

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Table 1. Their SiO2 and CaO contents are 10.91-11.79 wt. % and 44.77~47.21 wt. %

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respectively. On the Si-Mg/ (Mg+Fe) discrimination diagram, all the tested samples plot in

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the magnesium-hornblende field (Fig. 3c).

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(4) Clinoyroxene

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The EPMA data for clinopyroxene in the Gaojiabang granodiorite porphyry are shown

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in Table 1. On the Wo-En-Fs discrimination diagram, all the tested samples plot in the

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augite-diopside-salite field (Fig. 3d).

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4.2 Whole-rock geochemical compositions (1) Major elements 7 / 30

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The whole-rock geochemical compositions of the Gaojiabang granodiorite porphyry (mineralized) and granodiorite (barren) are listed in Table 2.

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The granodiorite porphyry samples have higher SiO2 and alkalinity (Na2O+K2O) than

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the granodiorite ones, which are respectively plotted into the quartz monzonite and

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monzonite fields respectively on the TAS diagram (Fig. 4a), and the granodiorite and

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(quartz) monzonite fields on the QAP diagram (Fig. 4b). On the Fig. 4c and d, the

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mineralized granodiorite porphyry samples plot in the high potassium, meta-aluminous

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zone. Furthermore, the granodiorite porphyry samples plot in the high potassium

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calc-alkaline field, whereas the barren granodiorite samples lie in the high

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potassium-shoshonitic series on the SiO2 vs. K2O diagram (Fig. 4c).

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On the Harker diagrams (Fig. 5), the granodiorite porphyry and granodiorite exhibit

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decreasing TiO2, Al 2O3, FeO, CaO, and P2O5 but increasing SiO2 with decreasing MgO

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trend. Furthermore, the barren granodiorite samples display trends similar to those of the

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Qingyang-Jiuhua plutonic complex, whereas the mineralized granodiorite porphyry

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samples have lower MgO, TiO2, Al2O3, FeOt, CaO, P2O5 contents than barren granodiorite

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ones (Fig. 5).

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(2) Trace elements

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The total Rare Earth Element (∑REE) concentrations of the mineralized granodiorite

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porphyry range from145.50 ppm to 159.46 ppm, with an average of 151.57 ppm, whereas

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the ∑REE concentrations of the barren granodiorite range from 189.69 ppm to 230.29

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ppm, with an average of 205.51 ppm. The δEu values [defined as Eu/(Sm*Gd)0.5

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normalized to chondrite values] and LREE/HREE ratios [defined as the ratio of light rare

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earth elements (La to Eu) and heavy rare earth elements (Gd to Lu)] of the mineralized

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granodiorite porphyry are 0.85-0.94 (average 0.90) and 14.37-18.10 (average 15.66)

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respectively. In contrast, the δEu values and LREE/HREE ratios of the granodiorite are

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0.79-0.90 (average 0.83) and 9.29-9.90 (average 9.53) respectively. Both the mineralized

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granodiorite porphyry and barren granodiorite exhibit enriched LREE, but the mineralized

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granodiorite porphyry has lower ∑REE concentrations, higher δEu values and

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LREE/HREE ratios than the granodiorite (Fig. 6a). 8 / 30

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On primitive mantle (PM) normalized spider diagrams (Fig. 6b), the barren

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granodiorite displays higher large-ion lithophile element concentrations (LILE, e.g. Rb, Ba,

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U, K, Pb and Sr) than the high-field strength (HFSE, e.g. Th, Ta, Nb, Zr, Hf, Sm, Eu, Ti and

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Y) and rare earth elements. The barren granodiorite samples show distinctly positive Rb,

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Ba, K, Sr, Pb and negative Th anomalies, and positive La, Nd, Sm and negative Ta, Nb, Ti,

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Zr, Hf, P anomalies (Fig. 6b). The mineralized granodiorite porphyry exhibits higher K, Zr

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and Hf concentrations and lower V, Sc and HREE concentrations than the barren

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granodiorite.

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5 Discussion

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5.1 Petrogenesis of the mineralized granodiorite porphyry

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(1) Petrological classification

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Both the mineralized granodiorite porphyry and barren granodiorite are sub-alkaline,

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high potassium, meta-aluminous granites (Fig. 4c, d), and consistently plot in the I-type

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granite fields on discrimination diagrams (Fig. 7a, b, c, d).

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Biotite mineral EPMA data can be used to determine the granodiorite type (Whalen,

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1988; Liu et al., 2013). The Al and Mg# values (Wones and Eugster, 1965) of the biotite

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grains in the Gaojiabang granodiorite porphyry are 0.06-0.07 and 0.52-0.64 respectively

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(Table 2), consistent with those of I-type granite biotite (Al <0.22, Mg#>0.38). The

247

samples plot in the I-type granite biotite field (Fig. 8a, Rahman, 1994), and are similar to

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syntexis-type granitoids in South China (Fig. 8b; Xu et al., 1982).

Ⅵ

Ⅵ

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(2) Magmatic evolution

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During

magmatic

evolution

rock-forming

minerals

(feldspar,

clinopyroxene,

251

hornblende and biotite) are products of fractional crystallization, and provide important

252

information on the conditions under which their parent magma evolved (Selby and Nesbitt,

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2000; Xiong et al., 2001; Jiang et al., 2005; Zhou, 2013). Rare earth elements increase

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during magmatic evolution (Klein et al., 2000) and the whole-rock HFSE and REE 9 / 30

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elements can be used to constrain magmatic evolution, as they are typically unaffected by

256

post-emplacement alteration (Barley et al., 2000; Hanski et al., 2001; Shimizu et al., 2004;

257

Arndt, 2008). In this section, the whole-rock geochemistry and EPMA data were used to

258

constrain the magmatic evolution of the mineralized granodiorite porphyry.

259

①

Nb/Ta ratio: Rutile, ilmenite, biotite and low-Mg amphibole are the main carrier

260

minerals of Nb and Ta (Dmineral/melt>1), and typically crystallized early in the

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granitoid fractional crystallization process. As rutile and ilmenite have Nb

262

concentrations less than Ta (DNb/Ta<<1), therefore the residual magma will trend

263

to have lower Nb and Ta concentrations, but higher Nb/Ta ratios (Linnen and

264

Keppler, 1997). By contrast, biotite and low Mg amphibole generally have more

265

Nb than Ta (DNb/Ta>>1), which results in the residual magma trending to low Nb

266

and Ta concentrations, and low Nb/Ta ratios (Stepanov and Hermann,2013;

267

Stepanov et al., 2014; Pfander et al., 2007). The Nb and Ta concentrations and

268

Nb/Ta ratios of the Gaojiabang mineralized granodiorite porphyry decrease along

269

the magma evolved (Fig. 9a~c), suggesting that the magma experienced marked

270

fractional crystallization of biotite and low-Mg amphibole, consistent with the

271

observed mineralogy.

272

①

Zr/Hf ratios: During magmatic evolution, the main rock-forming minerals (e.g.

273

feldspar, amphibole, and clinopyroxene etc.) are generally depleted in Zr and Hf

274

(Dmineral/melt<<1.0), resulting in the residual magma having higher Zr and Hf

275

concentrations with stable Zr/Hf ratios (Münker et al., 2004). However, zircon is

276

the main carrier of Zr and Hf (D mineral/melt >>1) and is enriched in Zr more than Hf

277

(DZr>>DHf), so the residual magma trends to lower Zr and Hf and Zr/Hf ratios

278

(Wang et al., 1996, 1997). The Gaojiabang granodiorite porphyry samples exhibit

279

higher Zr and Hf concentrations with increasing Zr/Hf ratios along the magma

280

evolution (Fig. 9d~f), which indicates there was little fractionation of zircon during

281

magma emplacement.

282

①

δEu values: Europium is strongly enriched in plagioclase (Dmineral/melt >>1),

283

consequently residual magma will be distinctly depleted in Eu after plagioclase

284

fractional crystallization (Taylor et al., 1981; Landenberger and Collins, 1996). 10 / 30

285

The δEu values of Gaojiabang granodiorite porphyry are 0.85-0.94 with an

286

average of 0.90, which indicates there was some fractionation of plagioclase.

287

① Y/Ho ratios：Bau (1996) showed that Y/Ho ratios generally remain stable (24-34)

288

during fractional crystallization, as the main rock-forming minerals have similar

289

DY/Ho values. However, when the magma is enriched in F, the Y/Ho ratios will be

290

distinctly different because F-rich fluid can extract Y (Bau and Dulski, 1995;

291

Veksler et al., 2005). Y/Ho ratios of the Gaojiabang granodiorite porphyry are

292

consistently in the range 22.73-26.76, which indicates that there is probably no

293

enrichment of F in fluids formed during the magma evolution.

294

In summary, the observed mineral chemistry indicate that the parent magma of the

295

Gaojiabang granodiorite porphyry was Zr-unsaturated, and experienced distinct fractional

296

crystallization with low-Mg amphibole, biotite and plagioclase. Furthermore, the

297

granodiorite porphyry also has high Nb/U ratios (5.00-9.21, >4.0), which indicates little or

298

no contamination during emplacement (Hofmann, 1997; Pearce, 1995; Taylor and Hayes,

299

1983).

300

(3) Magma source

301

The Gaojiabang granodiorite porphyry samples exhibit LREE enriched and HREE

302

depleted in the chondrite normalized diagram (Fig. 6a), indicating that the magma shared

303

similar geochemical characteristics with the continental crust (Taylor and McLennan,

304

1985). They also exhibit distinctly high (La/Yb)N ratios (26.27-37.76) and (Ga/Yb)N ratios

305

(3.62-4.10), suggesting that the magmas was derived from a depth where garnet was a

306

residual phase. Other mineral chemical compositions (e.g. hornblende, biotite, etc.) can

307

be used to determine magma source (Selby and Nesbitt, 2000; Xiong et al., 2001; Jiang et

308

al., 2005). In hornblende MgO-FeO vs. (FeO+MgO) and biotite Al2O3 vs.TiO2

309

discrimination diagrams (Fig. 10a, b), the Gaojiabang granodiorite porphyry samples

310

plotted in the crust-mantle transition zones.

311 312

5.2 Genetic relationship between granodiorite porphyry and granodiorite

313

in the Gaojiabang W-Mo deposit 11 / 30

314

The Gaojiabang mineralized granodiorite porphyry is located adjacent to the barren

315

granodiorite pluton (part of Qingyang-Jiuhua plutonic complex). LA-ICPMS zircon U-Pb

316

dating ages of the two intrusions yielded ages of 145.0±2.0 Ma for the mineralized

317

granodiorite porphyry and 144.9±1.2 Ma for the barren granodiorite pluton, which are

318

consistent range within analytical error (Fan et al., 2016). The geology, geochemistry and

319

physicochemical characteristics of both intrusions are listed in Table 3.

320

The granodiorite porphyry has higher SiO2 and alkali (K2O+Na2O) contents than the

321

granodiorite (Figs. 4 and Fig. 5), suggesting that the former is more evolved. However, the

322

∑REE contents of the granodiorite porphyry (145.31-159.21 ppm) are lower than for the

323

granodiorite (190.59-231.57ppm), indicating the more evolved granodiorite porphyry was

324

not sourced directly from the granodiorite (Ballard et al., 2001; 2002).

325

The granodiorite porphyry and granodiorite likely formed from two separate magma

326

systems, based on the following reasons: (1) the granodiorite porphyry contains more

327

(~vol. 9%) hydrous minerals (hornblende+ biotite, and hornblende> biotite) associated

328

with minor pyrite, pyrrhotite and molybdenite, whereas the granodiorite contains less

329

hydrous minerals (~vol. 3% hornblende+ biotite, and hornblende<< biotite) and no sulfide

330

minerals; (2) The Fe3+/Fe2+ ratio of the granodiorite porphyry (0.03-0.06 with average 0.04,

331

Table 2) is much lower than that of the granodiorite (0.15-0.81 with average 0.58),

332

indicating the oxygen fugacities of the two intrusions were distinctly different; (3)The

333

physicochemical properties (such as density, H2O contents, viscosity, and temperature) of

334

the two intrusions based on CIPW norm calculations are distinctly different (Table 3).

335

Compared to the granodiorite plutons, the granodiorite porphyry has higher viscosity,

336

temperature, H2O content and lower cooling rates, indicating that the latter was derived

337

from a separate magma system.

338

Although the mineralized granodiorite porphyry (145.0± 2.0Ma) and the barren

339

granodiorite pluton (144.9±1.2Ma) are broadly coeval in emplacement, they exhibit

340

distinct geological (size, lithology and mineral comparisons) and physicochemical

341

properties (e.g. density, H2O contents, viscosity, and temperature). Therefore it is

342

suggested that the mineralized granodiorite porphyry was likely derived from the lower

343

crust-upper mantle transition zone, whereas the barren granodiorite pluton formed from a 12 / 30

344

deeper oxidized mantle source (lower LREE/HREE values). In the SAP, there are dozens

345

of late Mesozoic porphyry intrusions (145-128 Ma) with W-Mo mineralization around the

346

large plutons. It is possible that these satellite porphyries also have no direct relationship

347

with those large plutons. This is consistent with the fact that the Xiaoyao W-Mo

348

mineralized porphyry intrusion has older zircon U-Pb age of ca. 140 Ma than the adjacent

349

Fuchuan pluton in SAP (ca. 133 Ma) (Shi, 2016a).

350

5.3 Indicators of W-Mo fertility and implications for mineral exploration

351

In the felsic melt, both of W6+ and Mo6+ are enriched in residual melt (Ma,

352

2009). In a shallow magma chamber, the partition coefficient of the Fluid/Melt

353

of both W and Mo (Df/mw and Df/m

354

indicators, which can be qualitatively identified by the geological and

355

geochemical characteristics. The granodiorite porphyry is genetically related to W-Mo

356

mineralization in the Gaojiabang area, and its geological and geochemical features are

357

summarized as follows:

Mo)

are controlled by the physicochemical

358

(1) Geology and mineralogy: the Gaojiabang granodiorite porphyry intruded as a

359

stock, and mainly contains plagioclase, K-feldspar and quartz, with minor hornblende,

360

biotite and clinopyroxene. EPMA data show that the plagioclase is oligoclase and albite;

361

and the K-feldspar has Or values of 83.89~96.34%. The biotite belongs to the Fe-Mg

362

biotite series (Fig. 3). These geological and mineralogical characters are similar to those

363

of other W-Mo mineralized granitoid porphyries in SAP (Zhou, 2013).

364

(2) Geochemistry: The granodiorite porphyry has higher K2O, and lower Al2O3,

365

TFeO, MnO, MgO, CaO, Na2O and P2O5 contents than the nearby barren granodiorite

366

(Fig. 5), and also has lower ∑REE (145.31 ~159.21 ppm) with negative Eu anomaly,

367

similar to those of other W-rich granitoid porphyries in SAP (Zhou, 2013) .

368

(3) Temperature: Based on CIPW calculation, the melt temperatures of the

369

granodiorite porphyry range from 843℃ to 852℃ with average 848℃ (Table 2), which is

370

lower than that of the barren granodiorite pluton (968-1091℃). The Zr concentration can

371

also be used for calculating magma temperature (Watson and Harrison, 1983), using the

372

formula Tzr=12900/[2.95+0.85M+ln(496000/Zrmelt)] where M=(Na+K+2Ca)/(Al×Si). Zrmelt is 13 / 30

373

the Zr concentration in the magma, which is generally taken as the whole-rock Zr content.

374

The calculated zircon crystallization temperature of the Gaojiabang granodiorite porphyry

375

ranges from 673-704℃ with average of 685℃, which is also lower than that of the

376

granodiorite pluton (727-780℃).

377

(4) Oxygen fugacity: In the Fe2O3/FeO vs. SiO2 and FeO vs. Lg(Fe2O3/FeO)

378

discrimination diagrams, the granodiorite porphyry plots in the ilmenite-series (Fig. 11a)

379

and reduced fugacity fields (Fig. 11b). However, the biotite Mg-Fe3+-Fe2+ discrimination

380

diagram (Foster, 1960) shows that the biotite grains from the granodiorite porphyry plot

381

between NNO (Ni-NiO) and HM (Hematite-Magnetite) buffer lines, which indicates the

382

biotite crystallized in oxidized magma. Hence, the oxygen fugacity of the W-Mo rich

383

granodiorite porphyry is probably in the transition zone between NNO and HM lines.

384

(5) Water content: The whole-rock loss on ignition (LOI) of the granodiorite porphyry

385

range from 0.76-2.70 wt. %, indicating that the tested samples were fresh with little

386

alteration. After CIPW calculation, their water contents range from 3.25 wt. % to 3.34

387

wt. %, with average 3.29 wt. %, higher than that of the granodiorite (1.03-2.05 wt. %). This

388

is consistent with the granodiorite porphyry having more hydrous minerals (hornblende+

389

biotite) and lower temperatures than the granodiorite.

390

In summary, the Gaojiabang granodiorite porphyry has the following characteristics:

391

(1) occurring as a small volume (stock); (2) having low ∑REE (145.31~159.21 ppm); (3)

392

showing weak negative Eu anomaly; (4) crystallized at low temperature; (5) having low

393

oxygen fugacity; and (6) enriched in water. Zhou (2013) suggested that the W-bearing

394

intrusions in SAP have higher K, W and Mo concentrations, whereas lower temperature

395

and fO2 values than the barren ones, which also support that the mineralized granodiorite

396

porphyry in Gaojiabang deposit belong to the W-bearing intrusions.

397

There are dozens of large granodiorite plutonic complexes in SAP (Fig. 1a), which

398

are surrounded by numerous small porphyritic intrusions as “satellites”. More than fifty

399

W-Mo deposits were found in SAP in recent years, which were genetically related to these

400

“satellites” porphyritic intrusions (Ding, 2012). However, the W-Mo enriched indicators of

401

those “satellites” porphyritic intrusions is still poorly understood, which limit us to identify

402

the W-Mo mineralization potential of those unexplored “satellites” porphyritic intrusions in 14 / 30

403

SAP mineral exploration . As the Gaojiabang granodiorite porphyry is a representative

404

mineralized porphyritic intrusions, its geological, geochemical and physicochemical

405

characteristics are probably valuable indicators for refining the W-Mo mineralized

406

porphyritic intrusion in the SAP mineral exploration.

407

408

6 Conclusions

409

(1) The Gaojiabang granodiorite porphyry is highly evolved I-type granite, sourced

410

from the transition zone between lower crust and upper mantle; it underwent strong

411

fractional crystallization involving hornblende, plagioclase, clinopyroxene, and biotite.

412 413

(2) The mineralized Gaojiabang granodiorite porphyry and the nearby barren granodiorite pluton are probably derived from separate magmatic systems.

414

(3) The favorable indicators of W-Mo mineralization in Gaojiabang granodiorite

415

porphyry is characterized as small volume and with hornblende phenocrysts, low ∑REE

416

concentrations, weak negative Eu anomalies, and high differentiation-index degree and

417

water contents with low oxygen fugacity.

418 419

Conflict of interest statement

420 421 422 423 424 425

We declare that we have no financial and personal relationships with other people or organizations that can inappropriately influence our work, there is no professional or other personal interest of any nature or kind in any product, service and/or company that could be construed as influencing the position presented in, or the review of, the manuscript entitled ” Petrogenesis and W-Mo enriched indicators of the Gaojiabang “satellite” granodiorite porphyry in Jiangnan transition Belt, South Anhui province, China”.

426 427

428

Acknowledgements

429

The authors thank Weiping Huang, Jianman Huang Hong Yi and other geologists

430

from No. 812 Geological Party, East China Metallurgical Prospecting Bureau of Anhui

431

Province. Prof. Yonghong Shi, Ph.D Juan Wang from Hefei University of Technology are 15 / 30

432

thanked for their enthusiastic help during EPMA analysis. Prof. Deru Xu and Dr. Rongqing

433

Zhang from spaGuangzhou Institute of Geochemistry，Chinese Academy of Sciences

434

(CAS) are specially thanked for their fruitful discussion. Prof. Peter Hollings from

435

Lakehead University, Canada is thanked for his suggestion and English editing. This

436

research was sponsored by the National key research and development program

437

(2016YFC0600206), Natural Science Foundation of China (41320104003 41172086;

438

41172084;

439

1212011220369; SinoProbe-03-02 -05), and Public Welfare Project of Anhui Province

440

(grant no. 2009-g-22) and the Fundamental Research Funds for the Central Universities

441

(JZ2016HGTB0730).

40830426),

China

Geological

Survey

(Grant

No.

1212011121115;

442

443

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granites of Lachlan fold belt, southeast Australia. American Mineralogist 73(3) : 281-296.

621

Wones, D.R., Eugster, H.P., 1965. Stability of biotite-experiment theory and application.

622

American Mineralogist 50(9): 1228-1228.

623

Wu, F.Y., Ji, W.Q., Sun, D.H., Yang, Y.H., Li, X.H. 2012. Zircon U–Pb geochronology and

624

Hf isotopic compositions of the Mesozoic granites in southern Anhui Province,

625

China. Lithos, 150, 6-25.

626

Xiong, X.L., Shi, M.Q., Chen, F.R., 2001. Biotite as A Tracer of Cu and Au Mineralization in

627

Hypergene-Subvolcanic Plutons. Mineral Deposits 21(2): 107-111 (in Chinese with

628

English abstract).

629

Xu, K.Q., Sun, N., Wang, D.Z. et al., 1982. Two Genetic Series of Granitic Rocks in

630

Southeastern China. Acta Petrologica Mineralogica et Analytica 1(2):1-12 (in Chinese with

631

English abstract).

632

Yuan, F., Zhou, T.F., Fan, Y. et al., 2006. Characteristics of Nd-Sr ISO topes of The

633

Yanshanian Magmatic Rocks in The Jiangnan Rise Bordering Anhui and Jiangxi

634

Provinces. Chinese Journal of Geology 41(1): 133-142 (in Chinese with English abstract).

635

Zhang, R.Q., Lu, J.J., Wang, R.C., Yang, P., Zhu, J.C., Yao, Y., Gao, J.F., Li, C., Lei, Z.H.,

636

Zhang, W.L., Guo, W.M., 2015. Constraints of in situ zircon and cassiterite U-Pb,

637

molybdenite Re–Os and muscovite 40Ar– 39Ar ages on multiple generations of granitic

638

magmatism and related W–Sn mineralization in the Wangxianling area, Nanling Range,

639

South China. Ore Geol. Rev. 65, 1021–1042.

640

Zhang, R.Q., Lu, J.J., Lehmann, B., Li, C.Y., Li, G.L., Zhang, L.P., Guo, J., Sun, W.D.,

641

2017. Combined zircon and cassiterite U–Pb dating of the Piaotang granite-related

642

tungsten–tin deposit, southern Jiangxi tungsten district, China. Ore Geol. Rev. 82, 21 / 30

643

268-284.

644

Zhang, W., Lentz, D.R., Thorne, K.G., Mc-Farlane, C., 2016. Geochemical characteristics

645

of biotite from felsic intrusive rocks around the Sisson Brook W–Mo–Cu deposit,

646

west-central New Brunswick: An indicator of halogen and oxygen fugacity of magmatic

647

systems. Ore Geology Reviews, 2016, 77: 82-96.

648

Zhao, L.Z., Liu, C.S., Sun, N., 1983. The Petrological Characteristics of Taiping-

649

huangshan Polygenetic Composite Batholith in Southern Anhui. Journal of Nanjing

650

University (Natural Science Edition) 2: 329-339 (in Chinese with English abstract).

651

Zhou, J., 2013. Origin of tungsten-bearing granites in the eastern Jiangnan Orogen belt.

652

Ph. D. Dissertation of Nanjing University. pp 1-95 (in Chinese with English abstract).

653

Zhou, T.F., Yuan, F., Hou, M.J., et al., 2004. Genesis and Geodynamic Background of

654

Yanshanian Granitoids in the Eastern Jiangnan Uplift in The Adjecent Area of Anhui and

655

Jiangxi Provinces, China. Jmineral Petrol. 24(3): 65-71 (in Chinese with English abstract).

656

Zhou, X., Yu, X.Q., Yang, H.M., et al., 2012. Petrogenesis and geochronology of the high

657

Ba-Sr Kaobeijian granodiorite porphyry,Jixi County,South Anhui Province.Acta Petrologica

658

Sinica 28(10): 3403-3417 (in Chinese with English abstract).

659

Zhu, J.C., Zhang, H., Xie, C.F., 2005. Zircon SHRMP U-Pb Geochronology, Petrology and

660

Geochem istry of the Zhujianshui Granite, Qitianling Plution, Southern Human Province.

661

Geological Journal of China Universities 11(3): 335-342 (in Chinese with English

662

abstract).

22 / 30

663

Figures

664 665 666 667 668 669 670 671 672 673 674 675 676 677 678 679 680 681 682 683 684 685 686 687 688 689 690 691 692 693

Fig. 1 Geology maps of the study area, a- Geological sketch map of southern Anhui Province (modified

694 695 696 697

Fig.6 Chondrite-normalized REE patterns (a) and primitive mantle-normalized trace element patterns (b)

698 699

Fig. 7 Discrimination diagrams for granitoid types (Collins et al, 1982): a- Ce-SiO2 diagram; b- Y-SiO2

after Zhou et al., 2004); b- geological sketch map of the Jiangnan transition zone (modified after Yuan et al., 2006); c- geological map of the Gaojiabang W-Mo deposit (modified after No. 812 Geological Party, 2009); d- cross section of No. 36 exploration line in Gaojiabang mining district (modified after No. 812 Geological Party, 2009) Fig. 2 Petrographic characteristics of two types of granitoid intrusions in the Gaojiabang mining district a- photograph of the granodiorite porphyry; b-microphotograph of the granodiorite porphyry; cphotomicrograph of the granodiorite; d-photomicrograph of the granodiorite; e- photomicrograph of the zoning-texture plagioclase from the granodiorite porphyry; f- BSE photograph of EPMA minerals from the granodiorite porphyry Bi-biotite; Di- Diopside; Kfs-K-feldspar; Plg-plagioclase; Qtz-quartz; Hbl-hornblende Fig. 3 Classification diagrams of EPMA minerals in Gaojiabang deposit a- feldspar (Or-Ab-An) discrimination diagram, b-biotite ternary diagram, c-amphiboles and dclinopyroxenes of magmatic rocks Fig. 4 Discrimination diagrams for the granite intrusions in Gaojiabang W-Mo deposit. a) TAS diagrams (after Middlemost, 1994): Ir - Irvine demarcation line, above - alkaline rocks, below - sub-alkaline plutonic intrusions: 1 - olivine gabbro; 2a - essexite; 2b - sub-essexite; 3 - gabbro - diorite; 4 - diorite; 5 granodiorite; 6 - granite; 7 - quartzolite; 8 -monzogabbro; 9 - monzodiorite; 10 - monzonite; 11 - quartz monzonite; 12 - syenite; 13 - foid gabbro; 14 - foid monzodiorite; 15 - foid monzosyenite; 16 - foid syenite; 17 -foidolite; 18 - tawite/urtite/italite. b) QAP diagrams: 1 - quartz-rich granite and quartzite; 2 alkali-feldspar granite; 3a - syenogranite; 3b - monzogranite; 4 - granodiorite; 5 -tonalite; 6 alkali-feldspar syenite; 7 - syenite; 8 - monzonite; 9 - monzodiorite; 10 - diorite; 6* - alkali-feldspar quartz; 7* - quartz syenite; 8* - quartz monzonite; 9* - quartz monzodiorite; 10* - quartz diorite; Q-quartz; A-alkali feldspar (orthoclase feldspar, perthite, anorthoclase, sodium feldspar); P - plagioclase; Q + A + P = 100; c) K2O–SiO2 diagram (after Ewart et al., 1998); d) A/NK–A/CNK diagram (after Maniar and Piccoli, 1989). Fig. 5 Harker diagrams for the granite intrusions in the Gaojiabang W-Mo deposit

of the two granitoid intrusions in the Gaojiabang W-Mo deposit. Chondrite data from Taylor and McLennan, 1985; primitive mantle standard values from Sun and McDonough (1989); publised data from Fan et al. (2016)

diagram; c- Zr-SiO2 diagram; d- Nb-SiO2 diagram

700 701 702 703 704

Fig. 8 Discrimination diagrams for magmatic biotite a- FeO*-AI2O3-MgO diagram (after Rahman, 1994), A- Non orogenic alkaline complex (A-type granite); C- orogenic calcium alkaline complex (I-type granite); 3+

2+

P- Peraluminous granite complex (S-type granite); b- Si-Mg/(Mg+Fe +Fe +Mn) diagram (after Zhao et al., 1983) 23 / 30

705 706 707 708 709 710 711

Fig.9 REE vs. Nb (a), Ta (b), Nb/Ta (c), Zr (d), Hf (e) and Zr/Hf (f) diagrams for the magmatic evolution of Gaojiabang mineralized granodiorite porphyry Fig. 10 EPMA mineral discrimination diagrams for magmatic source (a)MgO-FeO/ (FeO+MgO) diagram of biotite and (b) Al2O3-TiO 2 diagram of amphibole

712

Fig.11 Oxygen fugacity discrimination diagrams for the Gaojiabang granodiorite porphyry

713

(a)-Fe2O3/FeO-SiO2 diagram (from Ishihara, 2000); (b)-Lg(Fe2O3/FeO)-FeO diagram (from

714

Blevin, 2004) (c)-Biotite Mg-Fe -Fe discrimination diagram (from Foster，1960). HM-

715

Hematite-Magnetite (4Fe3O4+O2〓6Fe2O3); NNO- Nickel-NiO (2Ni+O2〓2NiO); FMQ-

716

Fayalite-Magnetite-Quartz (3Fe2SiO4+O2〓2Fe3O4+3SiO2)

717

Tables

718

Table1 EMPA results of the tested silicate minerals (plagioclase, K-feldspar, amphibole and

719

clinopyroxene) in the Gaojiabang W-Mo deposit

3+

2+

720 721

Table 2 Whole-rock geochemical data for granitoid intrusions in the Gaojiabang W-Mo deposit,

722

southern Anhui Province (major elements: wt. %; trace elements: ppm)

723 724

Table 3 Geology, geochemistry and physicochemical characteristics of the two granitoids in

725

Gaojiabang W-Mo deposit

726 727 728

24 / 30

729 730

Pyroxene

Hornblende

Biotite

Feldspar (including both plagioclase and K-feldspar)

Min eral

Table1 EMPA results of the tested silicate minerals (plagioclase, K-feldspar, amphibole and clinopyroxene) in the Gaojiabang W-Mo deposit Samle No. 362-299-1 362-299-2 202-162-1 202-162-2 202-162-3 202-162-4 202-162-5 366-570-1 362-306-1 362-306-2 362-306-3 362-306-4 362-306-5 362-306-6 362-306-7 362-306-8 362-306-9 362-306-10 362-306-11 362-306-12 506-602-1 506-602-2 506-602-3 506-602-4 506-602-5 506-602-6 506-602-7 506-602-8 506-602-9 506-602-10 506-602-11 506-602-12 506-602Bi4-1 506-602Bi2-1 506-602Bi1 506-602Bi6 362-299 3Amp-1 362-299 4Amp-1 362-299 5Amp-1 366-570 1Di-1 366-570 2Di-1 366-570 1Di-1 362-306 Di5-1 362-306 Di4-1

SiO2 Al2 O3 CaO Na2 O K2 O MgO FeO MnO TiO2 Cr2 O3 Total 70.47 70.34 64.88 65.55 62.59 72.45 66.09 64.51 66.99 67.81 68.51 67.38 66.46 63.82 64.88 65.02 61.75 64.26 63.12 62.80 62.80 59.56 62.46 60.85 62.11 61.70 62.50 62.49 65.19 62.84 64.49 65.31 41.16 40.10 40.89 39.77

18.65 18.54 18.09 17.58 23.07 19.21 18.07 18.10 20.45 19.87 19.66 19.85 21.69 23.02 22.43 22.05 24.31 22.48 23.19 23.61 23.46 25.55 23.57 24.32 23.88 23.62 23.72 23.77 22.14 23.18 22.16 17.96 12.31 12.58 12.90 12.62

0.24 11.19 0.04 0.24 11.01 0.04 0.07 1.47 11.93 0.35 13.90 5.35 8.29 0.22 0.12 11.47 0.13 0.01 0.52 13.99 0.80 13.02 1.76 10.68 0.18 1.19 10.69 0.03 0.79 11.16 0.04 1.11 10.75 0.07 3.02 9.96 0.08 4.66 8.80 0.23 3.83 9.16 0.12 3.68 9.31 0.13 6.07 7.97 0.22 4.23 8.93 0.47 5.12 8.32 0.42 5.41 8.15 0.25 5.18 8.43 0.10 7.58 7.10 0.13 5.24 8.34 0.35 6.30 7.67 0.35 5.56 8.16 0.38 5.67 7.90 0.39 5.35 8.30 0.29 5.39 8.31 0.22 3.52 9.16 0.44 5.00 8.42 0.22 3.63 9.18 0.21 0.87 15.01 0.02 0.10 9.99 0.03 0.16 9.80 0.03 0.18 9.97 0.04 9.74

0.01 0.03 0.01 0.03 0.01 0.04 0.01 0.05 0.01 0.02 0.02 0.05

0.03 0.01

0.01

0.01

0.01

0.01

0.01

19.62 16.73 19.05 16.33

0.02 0.02 0.03 0.01 0.01 0.03 0.01 0.02 0.03 0.04 0.01 0.05 0.03 0.03 0.01 0.02 0.04 0.01 0.07 0.10 0.03 0.05 0.02 0.05 0.03 0.04 0.07 0.08 0.07 0.11 0.07 0.01 11.04 0.15 14.33 0.17 11.98 0.14 15.19 0.18

0.01

0.01 0.01

1.00 1.59 1.26 1.57

100.61 0.02 100.19 96.49 0.02 97.40 99.55 0.02 103.40 98.74 96.49 100.13 99.60 100.17 99.20 101.25 0.02 100.55 100.48 100.21 0.01 100.37 0.01 100.44 100.23 0.03 100.28 0.04 100.04 99.98 0.04 100.08 0.01 99.63 100.16 99.36 0.01 100.20 100.26 100.51 99.72 0.01 99.79 99.23 95.38 95.48 96.40 95.45

Si

Al

3.05 3.05 3.04 3.06 2.78 3.05 3.05 3.03 2.94 2.97 2.99 2.97 2.89 2.81 2.84 2.86 2.73 2.83 2.79 2.77 2.78 2.66 2.77 2.72 2.75 2.76 2.76 2.76 2.86 2.79 2.85 3.02

0.95 0.95 1.00 0.97 1.21 0.95 0.98 1.00 1.06 1.03 1.01 1.03 1.11 1.19 1.16 1.14 1.27 1.17 1.21 1.23 1.22 1.34 1.23 1.28 1.25 1.24 1.24 1.24 1.14 1.21 1.15 0.98

Ca

Na

0.01 0.94 0.01 0.93 0.13 0.03 0.26 0.71 0.01 0.94 0.05 0.07 0.08 0.91 0.06 0.91 0.04 0.94 0.05 0.92 0.14 0.84 0.22 0.75 0.18 0.78 0.17 0.79 0.29 0.68 0.20 0.76 0.24 0.71 0.26 0.70 0.25 0.72 0.36 0.61 0.25 0.72 0.30 0.67 0.26 0.70 0.27 0.68 0.25 0.71 0.26 0.71 0.17 0.78 0.24 0.72 0.17 0.79 0.08

K

An

Ab

Or

MF

Fe3+

Fe2+

Mg

0.76 0.67 0.74 0.65

0.12 0.14 0.11 0.14

0.56 0.75 0.61 0.81

2.13 1.85 2.06 1.81

1.17 98.58 0.25 1.16 98.58 0.26 0.71 0.43 15.68 83.89 0.83 3.66 96.34 0.01 25.99 72.77 1.24 0.01 0.57 98.69 0.74 0.82 0.07 5.38 94.55 0.78 8.56 91.44 0.01 8.27 90.72 1.01 5.80 94.05 0.15 3.77 95.98 0.25 5.37 94.24 0.39 14.28 85.27 0.44 0.01 22.33 76.36 1.31 0.01 18.65 80.64 0.71 0.01 17.79 81.44 0.77 0.01 29.26 69.48 1.26 0.03 20.19 77.15 2.66 0.02 24.75 72.86 2.39 0.01 26.44 72.08 1.48 0.01 25.22 74.22 0.57 0.01 36.86 62.40 0.74 0.02 25.26 72.74 1.99 0.02 30.59 67.40 2.01 0.02 26.76 71.09 2.15 0.02 27.75 69.98 2.27 0.02 25.83 72.52 1.66 0.01 26.07 72.66 1.27 0.02 17.06 80.41 2.53 0.01 24.38 74.34 1.28 0.01 17.69 81.08 1.23 0.89 0.02 8.05 91.93

45.18 2.99 11.26 0.65

0.36 12.17 18.12 0.25 0.32

91.30 7.29

1.95 0.20 0.07

0.47

1.97

2.93

44.78 4.83 11.07 0.75

0.46 11.06 19.19 0.26 0.63

93.03 7.12

1.88 0.23 0.09

0.48

2.07

2.62

42.97 5.53 10.91 1.00

0.54 10.50 19.06 0.29 0.90

91.75 6.96

1.89 0.31 0.11

0.39

2.20

2.54

50.92 51.64 47.80 53.55 53.33

16.31 18.24 0.20 12.42 0.04 1 9.79

0.15 0.14 1.95 0.24 0.46

24.34 24.81 11.25 23.49 23.17

0.11 0.08 0.52 0.26 0.26

3.61 0.88 17.57 12.65 13.37

0.48 0.40 0.21 0.24 0.56 0.41 0.10

731 732 733 734

25 / 30

0.02

0.01 0.01

1.96 1.96 1.97 2.02 2.01

0.13 0.13

0.61 0.40 0.42

735 736

Table 2 Whole-rock geochemical data for granitoid intrusions in the Gaojiabang W-Mo deposit, southern Anhui Province (major elements: wt. %; trace elements: ppm) Sam. No Lithology Major elements (wt. %) SiO2 TiO2 Al2O3 Fe2O3 FeOt FeO MnO MgO CaO Na2 O K2 O P2 O5 LOI Total Na2 O/K2 O Fe3+/Fe2+ Differentiation index (DI) Density, g/cc Density (liquid) Viscosity (dry) Viscosity (wet) Temperature (melt,℃) H2 O content A (Alkaline feldspar) P (Plagioclase) A/CNK A/NK Trace elements (ppm) La Ce Pr Nd Sm Eu Gd Tb Dy Ho Er Tm Yb Lu Rb Ba Sr U Pb Cs Ga Th Nb Zr Y Ta Hf Li Bi Ge Be Sc Ni Cr Co V W Sn Cu Ag Zn Mo Se Sb

202-359

202-356

202-296

202-365

506-799 366-543 202-133 Granodiorite Granodiorite Granodiorite Granodiorite Granodiorite Granodiorite Granodiorite porphyry porphyry porphyry 61.98 0.75 15.63 2.47 5.88 3.06 0.11 2.30 4.04 3.73 3.46 0.24 1.53 99.82 1.08 0.81 68.41 2.77 2.49 5.79 4.97

58.36 0.94 16.28 2.71 6.83 3.70 0.12 2.73 4.60 3.88 3.45 0.30 2.70 100.38 1.12 0.73 63.91 2.79 2.52 4.79 4.27

54.67 1.08 16.75 0.89 7.63 6.07 0.11 4.12 3.93 4.26 4.19 0.37 2.18 99.63 1.02 0.15 63.06 2.81 2.54 3.72 3.42

61.71 0.85 15.95 2.21 6.06 3.46 0.10 2.42 4.99 3.82 2.58 0.27 0.76 99.64 1.48 0.64 64.10 2.78 2.51 5.63 4.87

68.80 0.40 15.17 0.13 2.65 2.27 0.04 0.75 2.63 4.58 3.74 0.14 1.06 100.15 1.22 0.06 82.39 2.69 2.42 8.17 6.38

69.06 0.40 15.20 0.07 2.68 2.35 0.03 0.72 2.79 4.18 3.91 0.14 0.88 100.16 1.07 0.03 81.25 2.69 2.42 8.29 6.46

69.21 0.37 14.68 0.09 2.39 2.07 0.02 0.63 1.57 2.75 7.09 0.12 0.87 99.88 0.39 0.04 87.12 2.66 2.40 8.43 6.48

968.00 2.05 39.19 30.07 0.91 1.59

1028.00 1.51 39.53 32.61 0.88 1.61

1091.00 1.03 49.43 28.36 0.90 1.46

980.00 1.93 30.23 37.20 0.88 1.76

852.00 3.25 49.64 21.98 0.93 1.31

849.00 3.27 47.51 22.94 0.94 1.37

843.00 3.34 62.82 10.15 0.98 1.21

39.20 79.00 9.46 35.20 7.18 1.72 5.86 0.85 4.73 0.92 2.62 0.35 2.26 0.34 105.50 790.00 629.00 3.60 15.60 2.05 23.50 13.60 19.30 11.90 24.80 1.24 0.80 22.10 0.10 0.26 2.53 12.10 11.00 30.00 13.80 103.00 0.90 2.00 7.40 <0.01 77.00 1.29 2.00 0.17

46.20 94.90 11.50 44.40 8.83 2.08 7.28 1.05 5.78 1.15 3.36 0.45 2.85 0.46 109.50 1160.00 641.00 2.10 14.20 2.38 24.90 9.20 23.10 13.40 31.00 1.47 0.90 29.00 0.17 0.31 2.30 15.30 12.70 30.00 16.70 129.00 1.70 2.50 13.20 0.05 94.00 1.27 2.00 0.20

41.50 85.70 10.45 39.50 8.07 2.11 6.43 0.93 5.41 1.04 2.95 0.40 2.51 0.39 113.00 2530.00 876.00 2.40 10.20 5.38 27.20 8.60 20.50 18.30 28.80 1.13 1.20 18.40 0.27 0.33 2.28 15.90 14.50 30.00 21.20 151.00 1.80 2.30 47.70 0.03 103.00 0.86 3.00 0.17

43.00 79.70 9.51 35.80 7.02 1.76 5.94 0.83 4.60 0.95 2.60 0.32 2.27 0.35 93.20 630.00 617.00 4.60 14.40 4.43 25.80 18.40 20.10 12.90 24.80 1.20 0.90 25.10 0.21 0.29 2.65 12.40 11.70 30.00 15.20 115.00 0.50 2.10 47.40 0.03 80.00 1.42 2.00 0.10

34.20 64.40 7.45 27.30 5.32 1.34 3.82 0.53 2.52 0.44 1.27 0.14 0.87 0.15 77.10 1030.00 684.00 2.40 8.30 1.21 25.50 8.20 22.10 24.40 10.00 1.45 1.10 11.80 3.15 0.22 3.18 2.70 2.90 10.00 5.70 40.00 0.70 2.20 89.30 0.02 37.00 2.30 2.00 0.09

32.60 62.70 7.23 27.20 5.05 1.33 3.72 0.50 2.44 0.40 1.14 0.15 0.89 0.15 91.90 950.00 745.00 2.40 9.00 2.76 25.80 8.00 22.60 27.60 10.50 1.46 1.20 13.90 0.49 0.24 2.94 2.80 3.50 20.00 5.10 37.00 2.50 1.80 104.00 <0.01 32.00 17.50 2.00 0.17

37.90 70.90 8.07 27.70 5.32 1.22 3.58 0.43 2.04 0.37 0.97 0.12 0.72 0.12 139.00 1210.00 548.00 3.30 7.70 1.35 27.20 11.90 16.50 46.80 9.90 1.19 1.70 9.90 5.51 0.21 2.32 2.50 2.60 20.00 5.70 36.00 18.80 2.10 260.00 0.07 74.00 1.88 2.00 0.10

26 / 30

Tl As ΣREE LREE HREE LREE/HREE LaN/YbN δEu

0.54 0.70 189.69 171.76 17.93 9.58 12.44 0.81

0.54 0.50 230.29 207.91 22.38 9.29 11.63 0.79

0.67 0.30 207.39 187.33 20.06 9.34 11.86 0.90

0.45 <0.2 194.65 176.79 17.86 9.90 13.59 0.83

737 738 739

27 / 30

0.21 0.30 149.75 140.01 9.74 14.37 28.20 0.91

0.25 0.70 145.50 136.11 9.39 14.50 26.27 0.94

0.56 0.70 159.46 151.11 8.35 18.10 37.76 0.85

740 741

Table 3 Geology, geochemistry and physicochemical characteristics of the two granitoids in Gaojiabang W-Mo deposit Characteristic

Granodiorite porphyry

Volume

Stock (<0.5km )

pluton (>50 km )

Geochronology

145.0±2.0Ma (LA-ICPMS zircon U-Pb)

144.9±1.2Ma (LA-ICPMS zircon U-Pb)

Petrography

Contains hornblende and biotite, with sparsely distributed pyrite and scheelite

Contains minor biotite with no sulfide minerals

ΣREE

145.50~159.46 ppm (avg.=151.57 ppm)

189.69~230.29 ppm (avg.= 205.5 ppm)

LREE/HREE

14.37~18.10 (avg.=15.66)

9.29-9.50 (avg.=9.53)

δEu

0.85~0.94 (avg.=0.90)

0.79~0.90 (avg.=0.83)

0.03-0.06 (avg.=0.04)

0.15-0.81 (avg.=0.58)

Zr/Hf

22.18-27.53 (avg.=22.24)

14.33-15.25 (avg.=14.84)

Rock type

I-type granite

I-type granite

Magmatic evolution

Evolving to low Nb､Ta contents, and high Nb/Ta ratios

Evolving to high Nb､Ta contents, and stable Nb/Ta ratios

H2 O content (CIPW)

3.25-3.34 wt. % (avg. = 3.29 wt. %)

1.03-2.05 wt. % (avg. = 1.63 wt. %)

Temperature (CIPW)

843-852℃ (avg.= 848℃)

968-1091℃ (avg.= 1016℃)

3+

2+

Fe /Fe

Zr saturation temperature Magma density (CIPW) Differentiation index (DI) Viscosity (CIPW) Reference

Granodiorite pluton

3

3

673-704℃ (avg.= 685℃) 3

727-780℃ (avg.= 748℃) 3

3

3

2.66-2.69 g/cm (avg.= 2.68 g/cm )

2.77-2.81 g/cm (avg.= 2.79 g/cm )

81.25-87.12 (avg.= 83.59)

63.06-68.41 (avg.= 64.87)

6.38-6.48 (avg.= 6.44)

3.42-4.97 (avg.= 4.38)

Fan et al., 2016; Jiang et al., 2009 and this study

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746

747 748 749 750 751 752

Graphical abstract

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753 754 755 756 757 758 759

Research Highlights (1) The Gaojiabang granodiorite porphyry is I-type granite, sourced from the mixed zone of the lower crust and upper mantle. (2) The Gaojiabang granodiorite porphyry has the favorable geological and geochemical characteristics to the W-Mo mineralization (3) The Gaojiabang granodiorite porphyry and the barren granodiorite pluton nearby are probably derived from separate magmatic systems.

760 761 762 763

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