Petrogenesis of High-K, Calc-Alkaline and Shoshonitic Intrusive Rocks in the Tongling Area, Anhui Province (Eastern China), and Their Tectonic Implications

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Petrogenesis of high-K, calc-alkaline and shoshonitic intrusive rocks in the Tongling area, Anhui Province (eastern China), and their tectonic implications

Cailai Wu1,†, Shuwen Dong2, Paul T. Robinson1, B. Ronald Frost3, Yuanhong Gao1, Min Lei1, Qilong Chen1, and Haipeng Qin1 1State Key Laboratory of Continental Tectonics and Dynamics, Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100037, China 2Chinese Academy of Geological Sciences (CAGS), Beijing 100037, China 3Department of Geology and Geophysics, University of Wyoming, Laramie, Wyoming 82072, USA

ABSTRACT ing of differentiated mantle and crustal melts, ing the petrogenesis of the two series. Several followed by assimilation–fraction crystalliza- processes have been proposed for the origin The Mesozoic intermediate-silicic intru- tion (AFC) processes. The magmatic activity of these rocks: (1) assimilation of country sive rocks in the Tongling area, Anhui Prov- may have been related to reactivation of the rock by alkaline basaltic magma (Mao, 1990), ince, eastern China, include a high-K, calc- Tongling-Deijiahui structural zone in re- (2) fractional crystallization of lower-crustal alkaline series and a shoshonitic series. Rocks sponse to rapid, highly oblique subduction of melts (Wu, 1986), (3) assimilation of lower- of the calc- alkaline series comprise more the paleo–Pacifi c plate beneath South China. crustal material by alkaline basaltic magma than 90% of the total and consist chiefl y of followed by fractional crystallization (Xing gabbro-diorite , granodiorite, quartz monzo- INTRODUCTION and Xu, 1995), (4) partial melting of basaltic diorite, and porphyritic quartz monzodiorite. lower crust to form tonalitic intrusive rocks These rocks are associated with important The Tongling district, which is situated in the (Zhang et al., 2001), and (5) mixing of mantle- skarn-type copper-iron deposits. They con- eastern part of the Yangtze River basin in derived magmas with those formed by partial tain three types of enclaves: mica-rich vari- Anhui Province, is an ancient copper capital melting of basaltic lower crust (Wang et al., eties that appear to be residues of partially of China and one of the most important metal- 2003). In this paper, we reexamine the origin melted pelitic rock, mafi c quartz monzo- bearing districts in the country (Fig. 1A). The of these granitoids using new sensitive high- diorite, and microdiorite. The shoshonitic polymetallic district is ~40 km long in an E-W reso lution ion microprobe (SHRIMP) U-Pb series consists of pyrox ene monzodiorite, direction and 20 km wide, with a total area of ages, whole-rock geochemistry, and the com- monzonite, and quartz monzonite, which are ~800 km2 (Fig. 1B). Within the district, there positions of the various enclaves hosted in the commonly associated with skarn-type gold are 76 intermediate-silicic intrusive bodies and gran itoids. We review all of the recent data on deposits. Enclaves in these rocks are typi- 54 known ore deposits (Wu et al., 2010a). The the ages of the rocks and their enclaves (X.S. cally pyroxene-rich or amphibole-rich vari- intrusive rocks are mostly intermediate dio- Xu et al., 2004; Du et al., 2004, 2007; Yang eties or amphibole gabbros. Zircon sensitive rites, monzonites, and quartz monzonites that et al., 2007; Zhang et al., 2006; Wu et al., high-resolution ion microprobe (SHRIMP) form an early high-K, calc-alkaline series and a 2001; Wang et al., 2004a, 2004b, 2004c; X.C. U-Pb age data suggest that the granodiorites, slightly later shoshonitic series. The ore depos- Xu et al., 2008), but the validity of some ages is quartz monzo diorites, and gabbro-diorites its are predominantly skarn type with copper, uncertain, because different dating techniques of the calc-alkaline series were generated at iron, and gold mineralization, accompanied by have yielded different ages for the same intru- ca. 146–142, 143, and 140 Ma, respectively. minor strata-bound types in the host carbon- sive body (Zhou et al., 1987;Wu et al., 1996). The shoshonitic rocks range in age from 143 ates (Zhao et al., 1999; Zhai et al., 1992). Some For example, 40Ar-39Ar dating of biotite from to 136 Ma. Although there is some overlap in porphyry-type mineralization is also present, some of the Tongling rocks has yielded ages of reported ages of the two series, contact rela- but it generally occurs only in the deeper parts 140–137 Ma for granodiorite, 137–136 Ma for tions indicate that the shoshonitic rocks post- of the intrusions (Pan and Dong, 1999). The quartz monzodiorite, 138–137 Ma for pyroxene date the calc-alkaline varieties. On the basis total reserves in this district have been esti- monzodiorite, and 134 Ma for gabbro-diorite of the geochemistry of the two series and the mated to be 500 Mt copper and 150 t gold (Wu (Wu et al., 1996, 2001), but these ages only character of their enclaves, the shoshonitic et al., 2010a). record the time at which the intrusive bod- series is thought to have formed primarily by Because of their associated copper and ies cooled through ~300 °C, the Ar-Ar clo- differentiation of a mantle-derived, weakly gold deposits, the intrusive rocks have been sure temperature of biotite (Cliff, 1985). A contaminated, alkali basalt magma, whereas studied for many years (e.g., Chang and Liu, few zircon SHRIMP U-Pb ages have recently the high-K, calc-alkaline series refl ects mix- 1983; Tang et al., 1998; Xing and Xu, 1995, become available (Yang et al., 2008; X.C. Xu 1996; Zhou et al., 1993; Wu et al., 1996, et al., 2008), but these studies all focused on †E-mail: [email protected] 2000, 2003), but there is no agreement regard- individual bodies . Here, we report new zircon

GSA Bulletin; January/February 2014; v. 126; no. 1/2; p. 78–102; doi: 10.1130/B30613.1; 12 ﬁ gures; 10 tables.

78 For permission to copy, contact [email protected] © 2013 Geological Society of America Petrogenesis of intermediate-acid intrusive rocks and zircon SHRIMP U-Pb dating in the Tongling area, Anhui Province (eastern China)

Figure 1. Geological sketch map of Tongling area, Anhui, China. R—Tertiary system; K2, K1—Upper and Lower Cretaceous 2 3 1 system; J3—Upper Jurassic system; J1–2—Middle and Lower Jurassic system; T2 -T2 —Middle Triassic system; D3-T2 —Upper Devonian system–Middle and Lower Triassic system; S—Silurian system; «—dating sample locations.

Geological Society of America Bulletin, January/February 2014 79 Wu et al.

SHRIMP ages for four plutons and discuss the Paleozoic and Triassic sedimentary rocks form LITHOLOGY OF THE INTRUSIVE petrogenesis of the intrusive rocks and their a series of complex, NE-trending folds with ROCKS AND THEIR ENCLAVES enclaves, as well as the tectonic environment thrust faults along their limbs (Zhai et al., in which they formed. 1996), many of which are cut by NW-trending The high-K, calc-alkaline series rocks range brittle faults (Fig. 1B). Several possible base- in composition from gabbro-diorite through GEOLOGICAL SETTING ment faults, including the major Tongling- quartz monzodiorite and granodiorite to aplitic Deijiahui structural zone, have been identifi ed granite. Most of these rocks have hypidiomor- The continental core of China is composed from geophysical data, and their intersections phic granular textures, except for the gabbro- of the South China block and the North China are thought to partially control the location diorites, which have gabbroic-diabasic textures, craton, which were welded together along the of the Mesozoic intrusions (Ren et al., 1992; and some granodiorites with porphyritic tex- Dabie-Sulu orogenic belt between ca. 250 and Zhai et al., 1996; Chang et al., 1996; Tang tures. The rock-forming minerals are plagio- 220 Ma. The South China block was formed et al., 2004). clase, quartz, amphibole, biotite, and potassium by collision and amalgamation of the Yangtze Seventy-six individual intrusions have been feldspar, most of which range from 1.2 mm to and Cathaysian blocks at ca. 880 Ma. The identifi ed in the Tongling area (Fig. 1B). Most 2.2 mm in size. Some porphyritic granodiorites Tongling area lies in the Yangtze polymetal- of these are small stocks and dikes, gener- have plagioclase phenocrysts up to ~6 mm. lic belt located in the northeastern part of ally with outcrop areas of 0.05–3 km2, locally Many of the plagioclase grains have diffuse the Yangtze block (Chang et al., 1991; S. Xu accompanied by small sills, apophyses, and cores crowded with opaque inclusions; others et al., 1992; Pan and Dong, 1999) (Fig. 1A). veins. They are hosted mostly in Silurian to contain inclusions of apatite. Some alkali feld- It is nearly perpendicular to the Tan-Lu fault, a Triassic carbonates and quartz sandstones, and spar phenocrysts are rimmed by plagioclase, major left-lateral, strike-slip fault that offsets less commonly in siliceous rocks. The intrusive suggesting magma mixing (cf. Hibbard, 1991). the Dabie ultrahigh-pressure (UHP) metamor- rocks are divided into a high-K, calc-alkaline These rocks contain three types of enclaves, phic belt several hundred kilometers to the series and a shoshonitic series on the basis of which are different from those in the shoshonitic northeast (Fig. 1A). The exact age of initiation their petrochemistry. series. Their main features are: of the Tan-Lu fault is uncertain, but 40Ar-39Ar The high-K, calc-alkaline rocks occur as (1) Mica-rich enclaves: These enclaves occur dating of amphibole in ductile shear zones in NE-trending stocks in Carboniferous dolomitic mainly in the granodiorites. They are black, the southern part of the fault suggests it was limestone and Permian to Triassic carbon- elliptical bodies that range from 4 to 8 cm in activated no later than 143 Ma, in response to ate rocks. Mineralized skarns hosting copper their long direction, and they consist chiefl y of rapid, highly oblique subduction of the paleo– deposits are well developed in the carbonates biotite (>80 modal%) and plagioclase (15%), Pacifi c plate beneath southeast China (Zhu (Chang and Liu, 1983), and these may represent with minor cordierite and almandine garnet. et al., 2005). Gravity and aeromagnetic data remobilization of stratiform sulfi de deposits (Xu Accessory minerals include magnetite, pyrite, suggest that the Tongling district is underlain and Zhou, 2001). Many of the stocks lie along, chalcopyrite, and sphalerite. Texturally, the by a regional, deep-seated, structural feature, or near, the axes of anticlines, but some irregu- enclaves consist of plagioclase phenocrysts the Tongling-Deijiahui structural zone (E-W lar bodies appear to have been emplaced at fault imbedded in a granular mosaic of biotite. These dashed line in Fig. 1B; Chang et al., 1991, intersections. The calc-alkaline bodies contain enclaves are interpreted as partially melted resi- 1996; Lu et al., 2003). This feature is consid- abundant enclaves, chiefl y composed of micro- dues of metamorphic country rock. ered by Wang and Cong (1998) to be an east- diorite, mafi c quartz monzodiorite, and mica- (2) Mafic quartz monzodiorite enclaves: ward extension of the Xiaotian-Mozitan deep ceous material. Based on fi eld relationships, These enclaves occur in granodiorites and fault, which separates the Huaiyang arc fl ysch these rocks predate the shoshonitic bodies and quartz monzodiorites. They are light gray in belt from the Dabie arc complex west of the have 40Ar-39Ar cooling ages ranging from 140 to color, angular in shape, and 8–30 cm across. Tan-Lu fault. We suggest that the magmatism 137 Ma for granodiorite, 137–136 Ma for quartz They have sharp contacts with the host rocks and mineralization in the Tongling district monzodiorite, and 134 Ma for gabbro-diorite and are generally concentrated along intrusive may have been initiated during reactivation (Wu et al., 2000). contacts, suggesting that they represent a chilled of this feature by transtensional movement on The shoshonitic intrusive bodies are pyrox- border phase. The mineralogy of these enclaves the Tan-Lu fault. Such reactivation may have ene monzodiorites that occur as NW- to NE- is similar to that of the host rocks, i.e., plagio- caused crustal thinning and mantle upwelling, trending dikes or stocks. They typically have clase + amphibole + alkali feldspar + quartz leading to partial melting of the upper mantle sharp contacts with the host Triassic carbonates + biotite, but they contain a higher percentage and lower crust, ultimately producing exten- and exhibit a preferred orientation of tabular of dark minerals, such as amphibole and bio- sive intermediate-silicic magmatism in the plagioclase grains aligned parallel to the intru- tite. Typical specimens have hypidiomorphic- region. Subduction of the paleo–Pacifi c plate sive contacts. The host carbonates have locally granular textures and consist of 50–60 modal% also triggered extensive Jurassic and Creta- been converted to marble, scapolite, and skarn. plagioclase, 15%–20% euhedral amphibole, and ceous magmatic activity elsewhere in south- All of these intrusive bodies contain abundant 5%–10% quartz, accompanied by minor potas- east China and reactivated many preexisting enclaves, including spinel pyroxenite, horn- sium feldspar and biotite. faults and fracture zones (Wong et al., 2009). blendite, hornfels, marble, and skarn. Some (3) Microdiorite enclaves: These enclaves Very few basement outcrops occur in the of the shoshonitic bodies were intruded along occur chiefl y in granodiorites but are also pres- Yangtze block, and the Tongling area is domi- contacts between the high-K, calc-alkaline ent in some quartz monzodiorites and porphy- nated by a sequence of Paleozoic and Trias- bodies and the host country rocks. The shosho- ritic granodiorites. They are dark gray in color sic marine carbonate, clastic, and siliceous nitic rocks are commonly associated with gold, and vary in shape from ellipsoidal or spherical sedimentary rocks, locally overlain by Cre- silver, lead, and zinc deposits. Their 40Ar/39Ar to irregular, fl ame-like forms. These enclaves taceous to Middle Tertiary continental clastic cooling ages range from 137 to 136 Ma (Wu generally range from 20 to 50 cm in diameter, and volcanic rocks (Xu and Zhou, 2001). The et al., 2000). with the largest up to 140 cm. They are typically

80 Geological Society of America Bulletin, January/February 2014 Petrogenesis of intermediate-acid intrusive rocks and zircon SHRIMP U-Pb dating in the Tongling area, Anhui Province (eastern China) distributed in the middle of the intrusive bodies, composition. All have sharp contacts with the Whole-Rock Chemical Analysis locally occurring in swarms or belts, and they host rock. We interpret these to be accumula- have gradational contacts with the host rocks. tions of early-formed pyroxene crystals that Thirty-six relatively fresh whole-rock and These enclaves mostly contain the same miner- solidifi ed before they were dispersed by a new six enclave samples were selected for complete als as the host rocks, and some of the crystals pulse of similar magma. whole-rock chemical analysis at the Chinese have reaction rims, suggesting possible min- (2) Amphibole-rich enclaves: These occur in Geological Experiment and Testing Center, gling of magmas. Some enclaves are compos- the monzonites and pyroxene monzodiorites. Academy of Geological Sciences, Beijing. ite features with dark central zones and lighter They are black, spherical or ellipsoidal, and Major oxides and Sr, Ba, Zn, Rb, Nb, Zr, and Ga rims, probably also refl ecting magma mix- 20–30 cm across. They consist chiefl y of amphi- were determined by X-ray fl uorescence spec- ing events. The minerals in these enclaves are bole (90–95 modal%) accompanied by minor trometry (XRF) on glass discs using National plagio clase (40–50 modal%), amphibole (20%– clinopyroxene, biotite, and pyrite. Most of these Standard GB/T 14506-1919. Total iron as Fe2O3 30%), biotite (5%–8%), potassium feldspar enclaves have textures and grain sizes similar to was determined by XRF, and FeO contents (3%–7%), and quartz (3%–5%), with accessory those of pyroxene-rich varieties. Likewise, they were determined by titration. Rare earth ele- apatite, titanite, zircon, magnetite, pyrite, and all have sharp contacts with the host rocks, and ments (REE) and other trace elements, includ- chalcopyrite. They have typical microgranular they are typically marked by thin reaction rims ing Cu, Pb, Th, U, Hf, Ta, Sc, Cs, V, Co, Cr, and textures and locally contain plagioclase pheno- of very fi ne-grained diopside. In some samples, Ni, were determined by inductively coupled crysts with compositions similar to those of the tabular plagioclase in the host rock is oriented plasma–mass spectrometry (ICP-MS) with an groundmass grains. Some of the phenocrysts parallel to the enclave boundary. These enclaves Agilent 7500a system using National Standard straddle the boundary between the enclave and are also interpreted as accumulations of amphi- LY/T 1253-1999. The analytical precision for host rock, and some have distinct, ellipsoidal bole dispersed by intrusion of a more mafi c the major oxides is better than 1%, whereas that cores with more calcic compositions than the magma as indicated by the pyroxene rims. for most trace elements is 5%. rims. Plagioclase in the groundmass is typically (3) Amphibole gabbro enclaves: These mainly Mineral Analysis reversely zoned and contains many inclusions occur in the monzonites and quartz monzonites. of apatite. Some quartz contains abundant inclu- They are black, spherical clots ranging from 5 The compositions of plagioclase, potassium sions of fi brous amphibole. Such textures sug- to 15 cm in diameter, composed of amphibole feldspar, amphibole, biotite, and pyroxene were gest that the enclave magma cooled rapidly in (60–70 modal%) with subordinate plagioclase determined on a Superprobe 733 at the Mineral- the host magma (Di et al., 2003). (15%–27%), minor biotite (1%–3%), and traces ogy Laboratory of the China University of Geo- The shoshonitic series includes pyroxene of pyroxene and apatite. These enclaves have sciences, Beijing, with an acceleration voltage monzodiorite, monzonite, and quartz monzo- allotriomorphic to hypidiomorphic textures. of 15 kV and a beam current of 0.02 mA using nite, all of which have idiomorphic-hypidiomor- On the basis of their textures and mineralogies, natural and synthetic minerals for standards phic granular textures. The main rock-forming these enclaves most likely formed by mixing of (Tables 3–7). The accuracy of the reported val- minerals (which range from 1.5 to 2.2 mm in mafi c and felsic magmas. ues is 1%–5%, depending on the absolute ele- size) are clinopyroxene, plagioclase, potassium ment concentrations. Oxygen abundances in the feldspar, and quartz, accompanied by subor- ANALYTICAL METHODS silicate minerals are based upon stoichiometry dinate biotite and amphibole. In addition, the (Deer et al., 1992). rocks contain abundant, fi ne-grained (0.01– Zircon SHRIMP U-Pb Dating 0.5 mm) accessory minerals such as magnetite, ANALYTICAL RESULTS zircon, titanite, and apatite. Sulfi de minerals, Four samples, HCJZK1, SYSZK3, FHS2, Zircon SHRIMP U-Pb Dating including chalcopyrite, pyrite, sphalerite, and and YSZ3, each ~2 kg, were collected for zircon bornite, are also common. separation. The samples were crushed to 60–100 Each dated sample is described in this sec- Three types of enclaves also occur in these mesh, rinsed, and air-dried. Magnetic minerals tion, and the analytical results are presented rocks: pyroxene-rich, amphibole-rich, and were removed with a hand magnet, and the dense in Table 1. amphibole gabbro enclaves. The pyroxene- and minerals were separated with heavy liquids. Zir- amphibole-rich enclaves are coarser grained con grains were then handpicked under a binoc- Sample HCJZK1 than the host rocks, but the minerals in the ular microscope, mounted in epoxy along with Sample HCJZK1 is from a drill core (hole enclaves and host rock have the same compo- zircon standard R33 (Black et al., 2004), and ZK1) of the Huchengjian gabbro-diorite of the sitions. The amphibole gabbro enclaves are ground to about half their thickness. The zircon high-K, calc-alkaline series. The rock is dark medium grained and have typical allotriomor- grains were photographed in refl ected light and gray in color and is characterized by abundant phic and hypidiomorphic textures, suggesting imaged in cathodoluminescence mode (CL) to pyroxene and plagioclase phenocrysts of simi- that they may have formed by mixing of mafi c determine their internal structures and to select lar size. The matrix has a diabasic texture and and felsic magmas. points for analysis. All of the analyses were consists of tabular plagioclase with fi ne-grained (1) Pyroxene-rich enclaves: These mainly carried out using the Stanford/U.S. Geological interstitial pyroxene and magnetite (see Table 2 occur in the pyroxene monzodiorites. They form Survey (USGS) SHRIMP-RG (sensitive high- for a chemical analysis of this rock). black, irregular clots, 4–7 cm across, composed resolution ion microprobe, reverse geometry) Zircon grains from this sample are prismatic, chiefl y of clinopyroxene (90–95 modal%), with facility. Age uncertainties are cited at the 95% with length:width ratios generally between 1:1 subordinate spinel (2%–3%), amphibole (1%– confi dence level for the selected populations, and 2:1. CL images are uniformly gray with no 2%), and accessory biotite, apatite, magnetite, and the internal precision for single analyses in evidence of zoning (Fig. 2A). Their U contents and pyrite. Most of the enclaves have abundant, tables and fi gures is 1σ. The age calculations range from 524 to 1545 ppm, and Th ranges relatively large (3–5 mm), euhedral to rounded were performed using the software Isoplot and from 661 to 2752 ppm, yielding Th/U ratios of crystals of pyroxene in a matrix of the same Squid (Ludwig, 2001, 2003). 1.3–2.7, indicating an igneous origin (Table 1).

Geological Society of America Bulletin, January/February 2014 81 Wu et al. err σ U age 238 (Ma) 1 Pb/ 206 VINCE, CHINA U% err U% 206 Pb/ 207 U % err 238 Pb/ 206 Pb % err 206 Pb/ 207 Pb % err Total 206 U/ 238 (%) Total Disc. R Pb (ppm) 206 U 238 Th/ 232 Th (ppm) U (ppm) are common and radiogenic portions, respectively. R C Pb Pb (%) 206 TABLE 1. ZIRCON SENSITIVE HIGH-RESOLUTION ION MICROPROBE (SHRIMP) U-Pb ISOTOPIC DATA FOR INTRUSIVE ROCKS OF TONGLING, ANHUI PRO TONGLING, FOR INTRUSIVE ROCKS OF DATA 1. ZIRCON SENSITIVE HIGH-RESOLUTION ION MICROPROBE (SHRIMP) U-Pb ISOTOPIC TABLE 206 and C Pb age. Pb 207 206 Pb/ 206 * Note: HCJZK1-4 0.10HCJZK1-8 1046 0.07 1716SYSZK03-1 533 1.69 0.27SYSZK03-5 725 20.4 213 0.24 −20 1.41SYSZK03-9 163 955 10.1 44.11 0.53 0.79 1705 20 189 0.4 4.1 1.84 45.19 133 6 0.0497 18.3 0.6 −30 0.73 44.98 1.5 3.6 0.0494 0.0226 44.76 1.0 70 0.4 3.1 0.5 0.0510 0.0483 0.0221 45.24 2.0 0.0508 3.4 0.6 1.0 144 0.0222 0.0494 1.7 3.1 1.0 0.0531 0.0223 1 0.0490 0.5 141 3.5 4.4 0.0480 0.0220 1 2.8 141 1.0 142 0.0510 1 4.6 1 140 1 FHS2-2 0.07FHS2-6 518 0.22FHS2-10 429 540 0.58 0.85YSZ3-3 361 231 10.0 0.11 −151 0.69YSZ3-7 115 10.6 250 44.48 0.52 3.38YSZ3-11 −91 26 4.4 182 0.6 0.29 43.98 −27 0.11 0.0495 93 386 0.6 5.0 44.70 0.53 2.4 −50 45 0.0507 62.9 1.0 0.0224 0.12 43.11 13 0.7 2.1 0.0535 7.6 0.0226 0.0447 1.1 2.48 72 3.3 4.6 0.6 0.0499 0.0222 0.0463 143 0.6 43.33 1.0 4.3 3.2 0.1614 1 0.7 0.0481 0.0231 145 6.8 1.1 0.7 0.0513 1 142 0.4028 0.0475 2.6 4.2 0.6 1 0.0231 0.1612 148 0.7 0.7 0.0513 2 2104 2.6 13* 147 1 HCJZK1-3HCJZK1-5 0.01HCJZK1-7 0.01 1052HCJZK1-9 0.03 1545 2705HCJZK1-11 0.22 1092 2752SYSZK03-2 2.66 0.03 524 1673SYSZK03-4 1.84 0.13 20.2 851SYSZK03-6 1.58 0.47 661 −69 1086 30.5 1288SYSZK03-8 0.38 −17 21.1 503 1.30 1118 44.77 1.56 0.01 −34 419 43.53 1.06 9.9 529 16.6 659 0.5 44.47 −14 740 20.9 −26 1.09 0.4 661 0.0488 1.82 0 45.38 0.4 9.4 43.95 0.0491 1.04 −13 7.8 1.6 44.68 0.0492 0.6 12.3 0.5 1.4 0.0223 17 45.77 1.5 0.0506 0.4 0.0230 4 0.5 0.0492 46.00 0.0225 0.4 0.6 0.0469 2.2 0.0499 46.02 1.8 0.4 2.4 0.0484 0.7 0.0220 0.0525 0.0227 1.5 1.6 0.0479 0.6 142 0.7 0.0518 0.5 0.0224 2.0 2.2 146 0.0484 0.0489 0.0482 1 0.4 0.0217 2.5 143 3.2 2.1 1 0.0489 0.7 2.0 0.0217 140 1 1.8 145 0.0484 0.0217 0.7 4.2 143 0.6 0.0493 1 1 3.7 0.0489 139 1 2.0 138 1 139 1 1 Spot name SYSZK03-10 0.24FHS2-1FHS2-3 367 0.83FHS2-5 461 0.64FHS2-7 304 0.66FHS2-9 1.30 220 0.07 79FHS2-11 225 7.2 201 0.39YSZ3-2 573 0.27 −58 1.52 204 0.94YSZ3-4 346 22.6 481 0.79 233 0.94YSZ3-6 43.62 21.5 42 255 0.39 0.87YSZ3-8 242 19 4.3 110 0.8 1.21 0.76YSZ3-10 11.54 10.9 294 −20 0.49 0.18 24 −75 8.78 331 0.0508 6.6 0.24 0.5 18 45.24 7.5 336 0.10 11 45.05 0.6 2.9 36 357 134 0.06 0.0648 4.8 1.0 23 0.0228 44.81 0.11 0.0677 0.6 −91 5.8 37 26.55 1.3 0.9 0.0541 0.07 −48 7.0 0.8 1.3 0.0483 0.11 0.0866 43.42 0.0472 0.8 6.7 49 3.3 0.1137 43.68 0.5 5.0 0.0519 7.0 2.1 0.9 0.0219 8 0.0630 0.6 0.0645 −74 40.85 146 0.0222 0.8 1.0 2.7 1.4 0.0665 0.0552 42.78 2.4 0.6 43.82 0.8 0.0483 0.0222 1 1.6 0.0521 531 0.0375 0.0467 3.1 7.0 0.8 0.8 691 0.0508 0.8 0.8 2.7 2.9 0.0228 0.0492 3 140 0.0505 0.0587 0.0228 142 1.0 2.9 0.0509 4.8 4 4.5 1 0.9 0.0463 0.0245 2.8 142 2.7 1 235 8.3 0.0475 0.8 0.0233 0.0227 4.9 1 0.0508 146 0.8 2 0.8 2.9 145 0.0493 0.0468 1 3.3 156 4.9 1 149 145 1 1 1 HCJZK1-1HCJZK1-2 0.23 0.03HCJZK1-6 783 812 0.15 1401HCJZK1-10 1055 1207 1.85 0.01 1.34 2151SYSZK03-3 14.7 887 15.5 −25 1.84 0.11 −50 1471SYSZK03-7 23.2 959 45.65 45.00 1.71 0.43 −7 767 0.5 17.2 284 0.5 44.64 −24 0.83 0.0500 279 0.0486 18.8 0.5 44.21 1.02 1.9 27 1.8 0.0501 0.0219 0.5 5.4 0.0222 43.90 0.5 −92 1.5 0.5 0.0490 0.0481 0.5 0.0224 0.0474 44.71 2.6 1.8 0.5 2.2 0.0498 0.0226 0.9 140 0.0487 142 0.5 1.7 2.0 0.0523 1 0.0482 0.0228 1 143 2.0 2.9 0.5 0.0222 1 144 0.0498 0.9 1.7 1 0.0463 145 7.4 1 142 1 SYSZK03-11 0.09FHS2-4 839 1416 0.25FHS2-8 1.74 473 0.05YSZ3-1 16.2 422 −83 515 0.30 0.92YSZ3-5 44.38 452 357 9.0 1.38 0.91YSZ3-9 0.5 65 29 260 9.9 0.42 0.0482 45.14 0.08 −98 77 308 1.8 6.9 0.7 44.51 0.31 −134 0.0225 28 0.0508 99.0 0.6 0.5 44.25 0.09 4 0.0465 2.3 0.0493 6.1 0.7 2.5 0.0222 −65 2.25 2.2 144 0.7 0.0513 0.0224 43.24 0.5 0.0508 2.6 1 0.7 2.3 0.1617 0.8 0.0224 0.0461 141 0.8 5.1 0.4 0.0524 0.0451 1 143 0.4434 2.9 6.0 0.5 0.0230 1 144 0.1615 0.9 0.4 1 0.0470 2330 6.5 12* 147 1

82 Geological Society of America Bulletin, January/February 2014 Petrogenesis of intermediate-acid intrusive rocks and zircon SHRIMP U-Pb dating in the Tongling area, Anhui Province (eastern China) ) continued ( High-K, calc-alkaline series TABLE 2. WHOLE-ROCK GEOCHEMICAL ANALYSES OF INTRUSIVE ROCKS AND ENCLAVES OF THE TONGLING DISTRICT TONGLING THE OF AND ENCLAVES OF INTRUSIVE ROCKS ANALYSES 2. WHOLE-ROCK GEOCHEMICAL TABLE 3.59 2.72 3.810.41 1.50 0.39 2.32 0.37 1.82 0.24 2.54 0.24 2.16 0.23 3.13 0.45 2.74 0.33 2.23 0.25 0.72 0.31 2.07 0.28 1.32 0.29 0.30 0.27 1.15 0.90 0.82 0.580.22 0.55 0.38 0.57 4.99 0.72 2.29 0.77 1.02 0.64 0.55 0.75 0.56 0.75 0.34 0.65 1.08 0.67 0.50 0.56 0.90 0.56 0.20 0.14 17.32 17.70 15.53 16.11 16.28 15.69 16.49 15.75 16.15 16.26 16.50 16.44 16.52 16.82 52.64 54.53 54.39 60.21 61.88 63.66 59.01 60.86 60.10 59.95 59.15 60.29 61.72 62.62 O 1.7 1.7 1.2 1.2 1.3 1.3 1.4 1.6 1.4 1.9 2.8 1.2 1.5 1.7 2 3 3 5 2 O/K O 3.67 3.77 3.28 4.07 4.25 4.03 4.18 4.38 4.24 5.00 5.48 3.96 4.13 4.97 2 O 2 2 2 O 2 O 2.17 2.18 2.80 3.39 3.23 3.01 3.01 2.82 2.99 2.70 1.96 3.38 2.79 2.94 O 2 2 2 Fe#ASIAn 0.61Ni 0.77 0.65 43.9Sr 0.87 12.6 0.54 43.9Ba 0.77 10.4 703 0.66 41.1 0.8 11.7 0.66 723 639 31.3 0.87 11.3 0.74 566 30.5 651 0.92 10.3 0.57 893 31.7 608 0.83 10.9 0.62 33 902 914 0.77 13.2 0.68 763 1131 28.8 0.86 10.3 0.51 1036 1198 31.1 0.72 0.46 8.8 928 981 24.8 0.74 0.67 13.9 923 757 24 0.69 0.68 11.0 881 780 33.8 0.88 0.57 10.9 1045 752 34.4 0.78 10.9 788 836 26.2 13.4 901 778 914 1099 1045 Samples HCJZK1 SML3 MJ1 JGS2 JGS9 DTS2 QSJ1 DGS1 JT4 DBZ3 DBZ1 TEBD1 TEBD2 TGS1 Na P Fe*MALIAI 0.71Cr –2.26V 0.72 –0.79 19116012470686658868211290737859 Rb 0.14 48.6Y 0.74 –0.72 0.14Nb 38.3 0.74 66 1.97Hf 0.14 26.4 20 0.77 2.93 67 19.2 0.13 18.4 0.79 64.1 5.21 3.02 13.3 0.13 95 18.3 0.69 62.1 3.5 1.54 17.7 0.12 87 12.5 0.71 98 1.42 4.12 15.9 0.13 86 12.9 0.81 2.39 4.12 61.2 16.3 0.12 14.5 87 0.66 1.28 5.17 67.4 16.9 0.13 17.8 0.62 1.11 78 5.03 53.8 15.9 0.11 19.8 −0.32 0.69 5.28 86.7 15.5 62 0.1 20.5 1.79 0.76 4.84 45.7 15.8 0.13 95 16.9 2.07 0.68 129.1 3.78 14.7 0.13 41 17.8 71.2 4.82 15.5 0.12 19.7 31 36.9 4.16 17.1 19 92 5.6 16.9 13.8 16 70 6.1 5.6 74 TiO Fe MnOCaO 0.18S 8.09 0.18 0.120.090.010.100.020.210.670.160.520.270.270.020.070.01 6.72 0.12 6.75 0.07 5.58 0.07 4.63 0.12 4.06 0.11 5.69 0.12 5.81 0.06 4.92 0.06 6.42 0.06 6.36 0.13 7.66 0.13 5.15 0.07 5.86 CoZr 23.8Ta 21 212 15.9 156 0.92 9.9 73 0.36 9.5 192 0.68 12.3 132 0.71 11.4 0.79 245 15.3 1.05 262 10.2 0.97 171 10 0.86 178 0.67 9.4 226 0.91 9.3 256 0.85 13 186 0.77 181 7.8 0.97 184 0.72 Rocks GBD GBD QMDP QMD QMD QMD QMD QMD QMD QMD QMD QMD QMD QMD FeOMgONa 5.36LOI 3.45 5.73CO 3.06 2.48 0.57 2.09 2.50 1.06 1.29 2.62 3.23 1.36 4.07 1.54 1.43 3.12 0.98 2.40 3.44 0.76 2.12 2.84 1.84 1.34 2.75 0.69 2.69 2.19 1.29 2.53 3.46 0.85 1.73 3.83 1.13 1.77 1.95 0.84 1.47 0.68 0.48 K SiO Al TotalALK 98.94 6.0 99.41 100.67 6.1 99.47 6.6 99.45 100.21 7.8 100.79 7.7 99.75 7.1 99.55 101.25 7.4 99.79 7.3 100.13 100.03 7.5 99.48 7.7 7.6 7.4 7.0 8.0

Geological Society of America Bulletin, January/February 2014 83 Wu et al. ) continued ( ) continued High-K, calc-alkaline series TABLE 2. WHOLE-ROCK GEOCHEMICAL ANALYSES OF INTRUSIVE ROCKS AND ENCLAVES OF THE TONGLING DISTRICT ( DISTRICT TONGLING THE OF AND ENCLAVES OF INTRUSIVE ROCKS ANALYSES 2. WHOLE-ROCK GEOCHEMICAL TABLE REE 185 136 197 150 150 150 187 183 173 154 175 184 178 175 PrGd 9.8Er 6.6 5.93 3.97 9.6 3.14 4.50 7.3 1.83 3.33 1.81 7.4 3.41 1.10 7.3 3.42 1.11 9.3 8.24 1.33 8.6 5.25 2.45 8.9 4.48 1.95 7.5 3.93 2.31 4.31 8.9 1.71 4.61 9.1 1.79 4.38 1.84 8.7 4.04 2.05 8.8 1.15 Rb/Sr 0.09 0.09 0.17 0.10 0.09 0.11 0.06 0.06 0.13 0.05 0.04 0.11 0.09 0.07 CeNdEu 73.0Tb 34.70Ho 55.7Tm 1.86 25.20Lu 1.15 85.3Σ 33.60 1.44 1.07 0.63 65.0 0.48 25.70 1.58 0.67 0.35 0.66 65.5 25.90 0.29 1.25 0.69 0.28 26.40 0.53 64.7 0.37 1.27 0.44 0.41 31.40 0.61 79.2 0.26 1.32 0.47 33.40 0.32 0.63 78.3 0.21 2.11 0.53 30.70 0.30 0.99 72.2 0.29 1.69 27.20 0.94 0.25 0.69 65.4 0.31 1.43 31.90 0.70 0.27 0.84 75.1 0.27 31.90 1.45 0.80 0.28 0.61 80.2 31.10 0.39 1.58 0.61 0.12 31.40 0.74 76.8 0.36 1.62 0.68 0.27 0.72 76.2 0.39 1.53 0.75 0.27 0.76 0.34 1.54 0.68 0.19 0.67 0.23 0.51 0.11 0.27 0.27 Eu*/EuBa/Rb 0.80 9.8 0.94 9.7 0.86 6.4 0.91 10.5 0.90 13.2 0.93 12.0 0.91 11.9 0.88 14.8 0.78 0.92 9.3 0.89 25.5 0.88 25.4 0.87 9.8 0.91 13.1 14.2 PbBi 52.2Be 53.5 1.6 24 0.3 1.9 21.1 0.2 1.94 14.8 2.51 0.3 19 2.15 0.2 34.3 2.18 0.8 21.8 2.13 0.4 41.5 2.26 0.9 11.6 2.18 16.6 1.7 1.9 27.1 0.8 1.88 25.3 0.7 1.96 10.8 0.9 2.39 2.19 0.3 2.28 0.2 SmDy 7.93Yb 5.25 5.33 6.48 3.71 2.30 4.86 3.68 1.80 5.00 2.61 2.67 5.02 2.64 2.10 6.24 2.96 1.86 6.33 4.56 1.50 6.45 3.80 2.09 5.44 3.99 1.91 6.21 3.41 0.81 6.34 3.65 1.75 6.06 3.95 1.69 6.05 3.83 1.16 2.92 0.72 1.71 Sr/Y26.639.330.971.469.952.667.349.536.946.242.242.440.979.6 RocksThUZn GBDSc 6.60 GBDAs 1.32 131Sb QMDP 7.56 2.26Li 0.28 115 QMD 12.06 33.2Mo 2.10 12.23 QMD 0.20 9.73 86 10.3 31.7 2.30 9 QMD 10.17 0.71 2.4 44 2.8 20.8 2.70 QMD 11.14 5.23 0.24 1.6 3.6 55 25.4 2.02 QMD 9.44 5.14 0.30 1.0 QMD 2 2.83 9.5 95 8.72 5.89 0.30 QMD 1.4 2.48 10.7 8.50 68 4.3 5.36 0.52 QMD 2.40 1.2 16.8 9.41 8.34 0.38 5.6 76 QMD 2.35 10.22 2.5 9.1 6.12 0.84 7.8 QMD 62 11.66 2.87 13.6 1.6 9.63 0.21 QMD 27.8 33 9.82 2.60 8.7 9.2 0.80 1.2 2.7 8.93 2.60 40 0.74 9.7 7.35 2.2 2.9 1.35 87 0.74 7.66 9.2 0.8 4.6 0.42 94 5.56 13.8 1.0 3.3 0.20 57 16.6 2.5 2.5 13 1.0 1.5 CuAg 75Ga 41 0.2La 28 28.4 0.29 17 0.1 73 37.9 0.1 18.6 28.6 63 19 45.3 0.1 36 35.1 19.6 0.1 90 34.7 22.6 0.2 122 34.4 18.2 0.2 221 38.4 16.7 0.3 4 39.4 20.5 0.2 39.7 17 3 0.1 34.5 15.7 15 0.3 37.8 19.2 12 41.0 0.1 18.4 240 40.7 0.3 22.2 39.1 Samples HCJZK1 SML3 MJ1 JGS2 JGS9 DTS2 QSJ1 DGS1 JT4 DBZ3 DBZ1 TEBD1 TEBD2 TGS1

84 Geological Society of America Bulletin, January/February 2014 Petrogenesis of intermediate-acid intrusive rocks and zircon SHRIMP U-Pb dating in the Tongling area, Anhui Province (eastern China) ) continued ( Enclaves (HAC) ) continued High-K, calc-alkaline series (HAC) TABLE 2. WHOLE-ROCK GEOCHEMICAL ANALYSES OF INTRUSIVE ROCKS AND ENCLAVES OF THE TONGLING DISTRICT ( DISTRICT TONGLING THE OF AND ENCLAVES OF INTRUSIVE ROCKS ANALYSES 2. WHOLE-ROCK GEOCHEMICAL TABLE 2.52 2.12 2.120.28 1.72 0.25 1.87 0.25 1.53 0.23 1.25 0.21 0.55 0.21 2.23 0.23 1.05 0.18 2.11 0.22 0.51 0.17 4.13 0.22 3.19 0.03 0.43 0.24 0.55 0.56 0.57 0.600.27 0.50 1.81 0.48 0.36 0.52 0.26 0.42 0.95 0.49 0.95 0.32 2.20 0.47 3.08 0.11 0.82 0.93 4.27 0.90 5.69 0.16 0.10 0.57 16.73 15.48 16.26 16.13 16.38 16.40 16.34 16.08 15.53 14.49 15.14 12.69 16.35 15.09 62.74 63.12 63.58 62.85 64.23 64.33 61.16 61.72 63.77 63.59 58.19 75.37 59.58 54.50 O 1.8 1.2 1.6 1.4 2.0 1.9 1.6 1.5 1.3 0.4 0.5 1.0 1.5 1.6 2 3 3 5 2 O/K O 4.81 3.93 4.75 4.68 5.06 5.09 4.56 5.12 4.11 1.41 1.46 3.87 3.85 3.82 2 O 2 2 2 O 2 O 2.72 3.23 3.01 3.33 2.53 2.70 2.78 3.41 3.10 3.88 2.71 3.96 2.51 2.33 O 2 2 2 Samples TGS2 FHS2 FHS1 NHC1 STJ3 STJ5 QTY1 QTY2 SJDLC1 XQT4 YSZ3 TGS3 FHSB4 TEBDB6 P Fe#ASIAn 0.63Ni 0.88 0.71 28.3Sr 0.92 11.1 0.67 31.2Ba 0.88 1040 0.52 9.9 26.1 0.8 699 0.68 10.0 1098 25 0.94 809 0.69 12.6 819 25.33 0.9 0.72 13.0 961 898 24.45 0.94 0.74 1188 12.0 29.21 941 0.8 1019 0.69 14.8 20 1056 705 0.71 0.89 12.1 29.83 951 0.67 1.02 10.1 703 63.26 681 67.52 0.86 0.9 697 5.8 803 17.4 0.55 0.93 204 6.9 898 21.67 0.52 1.11 448 9.1 726 47.92 0.69 292 6.2 489 690 17.9 695 593 797 829 SiO TiO Na Fe MnOCaO 0.11S 4.72 0.08 3.94 0.09 0.01 4.18 0.07 0.16 5.03 0.08 0.02 3.60 0.07 0.34 3.94 0.03 0.09 3.96 0.05 0.36 4.48 0.07 0.65 4.14 0.10 0.21 4.36 0.11 0.33 6.46 0.04 0.33 1.64 0.09 0.03 3.44 0.20 0.04 7.42 0.96 0.82 Fe*MALIAI 0.77Cr 2.84V 0.8Rb 616672575954655463355417132207 0.12 3.32 57.3Y 0.76 0.13 3.61Nb 122.2 72Hf 0.68 0.12 3.05 58 15.5 134 0.77 16.9 0.12 4.06 16.1 79.3 5.9 0.76 114 17.5 0.11 3.9 17.4 129.4 0.78 6.13 17.7 75 0.11 3.57 104.1 13.2 0.77 6.78 13 0.12 72 4.27 74.5 11.9 0.79 3.98 0.12 18.8 3.13 51.6 70 11.8 0.77 5 0.12 17.9 1.01 74.3 78 8.2 0.77 0.17 16.1 −2.52 4.5 23.1 8.6 85 0.9 0.17 15.3 6.23 4.21 19.2 14.7 112 0.73 0.1 16.8 3 5.27 25.2 13 167 0.62 18.2 0.13 4.7 −1.3 16.2 16.5 105 13.5 0.11 83.9 5.1 7.2 12.6 65 5.4 27.6 14 115 3.9 13.7 76 5 n.d. n.d. Rocks QMD GD GD GD GD GD GDP GDP GDP GDP GDP GV MDE MQME FeOMgONa 2.42LOI 1.44 3.06CO 1.22 2.90 0.58 1.46 1.55 1.31 1.44 2.58 0.62 1.22 2.74 2.20 1.23 2.68 0.75 1.06 2.09 0.66 0.73 2.94 2.86 1.33 2.18 2.16 0.89 2.76 0.92 1.38 0.97 3.10 0.16 3.29 3.52 2.65 5.14 0.24 4.69 1.77 0.76 K CoZr 11Ta 189 9.4 187 8.4 0.85 187 11.3 0.88 196 9.8 1.26 175 10.7 0.82 172 10.4 0.67 122 13 0.56 0.75 118 10.6 0.81 162 6.3 0.76 161 8.7 0.82 43 6.6 0.61 121 15.1 0.67 136 24 n.d. 184 n.d. Al TotalALK 99.90 100.27 7.6 100.17 7.4 100.43 100.05 7.8 100.69 8.2 100.28 100.28 7.7 100.00 7.9 100.14 100.25 7.8 99.79 9.0 100.08 7.4 99.67 5.7 4.6 7.9 6.5 6.3

Geological Society of America Bulletin, January/February 2014 85 Wu et al. ) continued ( Enclaves (HAC) ) continued High-K, calc-alkaline series (HAC) TABLE 2. WHOLE-ROCK GEOCHEMICAL ANALYSES OF INTRUSIVE ROCKS AND ENCLAVES OF THE TONGLING DISTRICT ( DISTRICT TONGLING THE OF AND ENCLAVES OF INTRUSIVE ROCKS ANALYSES 2. WHOLE-ROCK GEOCHEMICAL TABLE 0.90 0.88 0.85 0.98 0.86 0.87 0.88 0.86 0.86 0.86 0.95 0.98 0.61 0.80 0.2 7.3 0.4 0.4 0.31.371.21 0.4 1.54 1.40 1.40.07 1.67 1.61 0.19 1.1 1.35 1.15 0.14 1.06 0.4 1.45 0.08 0.99 0.3 1.00 0.06 0.62 0.1 1.16 0.07 0.69 3.1 1.30 0.11 1.38 0.3 1.30 0.12 1.35 1.74 0.1 0.16 1.65 1.95 0.82 0.67 1.34 0.23 2.90 2.70 0.22 1.40 1.20 0.17 0.13 0.10.24 0.52.39 0.46 0.3 2.39 0.40 0.1 2.46 1.384.31 0.09 2.233.28 1.30 3.65 0.10.21 2.43 3.22 0.30 3.870.20 0.4 0.31 2.27 3.50 1.20 4.20 0.22 0.19 0.33 2.14 2.53 0.47 3.51 0.26 0.12 0.19 1.98 2.57 0.53 3.55 0.14 0.12 0.13 2.2 2.53 0.43 2.78 0.23 0.13 0.11 1.81 0.54 2.58 2.71 0.16 0.23 10.50 0.15 1.86 1.84 3.34 0.25 0.63 0.40 0.11 2.93 3.07 2.43 0.21 0.56 0.61 0.19 2.37 1.5 3.36 0.21 0.32 3.22 0.96 1.41 0.27 0.29 1.21 7.60 0.30 0.11 6.00 4.90 0.22 0.48 3.50 0.40 0.26 0.20 1.12 2.671.4 2.25 3.3 2.570.9 2.15 3.69.1 3.3 2.19 2.56.37 8.2 2.1 2.600.68 5.44 2.90.59 8.6 2.80 1.2 0.55 5.84 12.7 0.58 7.4 2.56 0.63 1.4 4.44 51 0.63 1.38 9.3 0.49 5.90 2.2 6.2 0.49 1.50 0.49 5.98 9.6 3.1 0.41 4.4 2.42 0.49 4.50 7.0 1.3 0.40 n.d. 2.8 0.47 4.32 6.6 1.6 0.30 11.7 n.d. 0.47 4.94 7.4 0.31 1.8 47.8 0.60 3.75 6.6 0.53 0.6 1.8 0.40 4.53 0.47 6.2 1.2 0.52 5.2 1.90 0.58 3.0 0.21 2.1 8.20 0.24 12.8 1.20 4.30 3.6 1.20 5.2 0.60 0.60 5.4 6.13 6.4 4.21 4.71.62 1.34 4.58 1.39 5.65 1.39 4.86 1.38 6.12 1.41 2.21 1.09 6.41 1.02 1.51 1.20 n.d. 0.90 n.d. 1.25 0.54 1.60 1.20 15.3 6.1 7.9 12.5 14.7 13.7 8.8 9.5 8.0 4.3 4.7 10.7 6.9 10.9 91 42 58 67 71 43 177 64 38 59 73 98 71 148 24.910.98.415.216.714.818.515.810.19.82610.920.537.2 78.8 71.3 75.7 68.2 80.9 84.5 62.2 58.2 64.2 62.6 51.7 27.8 113.9 47.2 132751403825689344857127604202 24.4 20.9 20.9 21.1 23.2 22 20.867.1 22.5 43.4 19.7 46.5 18.5 72.8 17 99.8 25.2 86.4 19.7 86.0 15.9 81.7 47.4 15.7 27.2 40.6 25.0 43.3 20.8 19.7 18.1 31.240.5 177.3 38.2 16.3 39.9 31.1 37.3 24.1 41.4 15.7 43.3 19.4 32.4 60.8 29.5 109 33.8 12.5 36.4 12.7 26.3 17.0 57.0 26.3 32.70 28.90 30.70 25.90 32.70 33.60 24.60 23.20 25.90 21.10 23.00 9.50 46.40 20.70 181 165 175 155 181 188 139 130 148 141 125 65 262 118 REE Σ Ga Bi La Er Be Eu*/Eu Sr/Y Ag Gd ThPb 9.37 11.35 9.95 7.81 11.69 11.42 9.59 10.26 11.69 16.44 8.41 16.08 15.00 9.00 Li Mo Sb Tm Lu Ba/Rb Pr U Zn Sm As Tb Ho Yb Rb/Sr SamplesRocks TGS2 QMD FHS2 GD FHS1 NHC1 GD STJ3 GD STJ5 GD QTY1 GD QTY2 SJDLC1 GDP XQT4 GDP YSZ3 GDP TGS3 GDP FHSB4 TEBDB6 GDP GV MDE MQME Sc Ce Cu Nd Eu Dy

86 Geological Society of America Bulletin, January/February 2014 Petrogenesis of intermediate-acid intrusive rocks and zircon SHRIMP U-Pb dating in the Tongling area, Anhui Province (eastern China) ) continued ( ) O H S ( s e v a l c n E ) continued ) O H S ( s e i r e s c i t i n o h s o h S TABLE 2. WHOLE-ROCK GEOCHEMICAL ANALYSES OF INTRUSIVE ROCKS AND ENCLAVES OF THE TONGLING DISTRICT ( DISTRICT TONGLING THE OF AND ENCLAVES OF INTRUSIVE ROCKS ANALYSES 2. WHOLE-ROCK GEOCHEMICAL TABLE ) A C H ( s 5.91 2.71 3.840.16 0.97 0.56 2.96 0.45 0.82 0.35 1.97 0.34 1.36 0.21 2.25 0.31 3.42 0.22 1.00 0.31 2.79 0.29 7.15 0.19 9.20 1.85 1.72 1.90 1.88 1.21 0.87 1.050.14 0.99 0.34 0.65 1.51 0.71 2.55 0.68 0.05 0.79 0.23 0.70 0.20 0.48 0.50 0.40 0.38 2.45 2.62 2.45 0.80 0.49 2.55 0.84 e 20.44 17.16 16.60 16.67 16.41 15.59 16.16 15.83 15.68 15.99 16.02 12.13 13.14 11.98 42.07 50.81 55.52 57.32 56.32 61.69 58.85 61.58 59.35 57.46 62.30 41.96 34.82 40.94 v a l c n E O 0.5 1.2 1.4 1.4 1.5 0.8 0.9 0.8 1.1 1.4 0.1 0.7 2.0 1.2 2 3 3 5 2 O 2.59 3.73 4.49 4.70 4.41 3.90 4.35 3.76 4.27 4.46 0.97 1.88 1.91 2.51 O/K 2 O 2 2 2 O 2 O 5.06 3.10 3.11 3.36 2.93 5.10 4.75 4.72 3.77 3.19 10.12 1.16 0.95 2.05 O 2 2 2 Fe#ASIAnNi 0.61 1.23Sr 0.63 40.83 0.65 79.5 0.63 39.9Ba 0.73 669 14.4 0.72 29.6 0.75 0.67 1684 1116 9.9 26.7 0.8 1109 0.66 12.5 30.5 752 0.83 0.57 952 13.4 23.2 944 0.68 0.57 720 14.3 22.3 788 0.81 0.61 11.4 28 665 789 0.75 0.74 12.4 940 25.7 966 0.75 0.74 13.2 719 27.3 944 0.98 0.26 11.9 1031 53.6 972 0.36 0.52 7.1 903 72 916 0.49 0.55 638 9.0 68.3 943 0.5 300 9.2 49.03 1055 773 8.5 280 682 322 373 P Fe*MALIAICr 0.7V 3.84Rb 0.7 0.22 −2.86Y 180.7Nb 0.78 0.73 307 0.14 24.5Hf 321 0.75 1.84 0.13 178 25.9 31.8 93 23 0.75 1.53 0.13 128 18.4 24.9 n.d. 107 0.68 5.2 0.12 21.1 128 93.8 23.3 0.69 6.23 0.15 60 2.68 18.6 209.6 143 20.9 0.64 5.7 0.14 3.91 115.1 15.7 87 18.5 73 0.7 163.2 5.19 0.15 2.41 17.9 162 13.8 85 46.6 0.85 4.71 0.13 1.72 17.1 104 17.6 82 55.1 0.78 5.74 0.12 9.14 18.9 130 15.1 −17.3 47.5 100 0.36 5.2 0.26 17 21 87 −11.4 24.4 0.64 0.12 106 5.6 17.5 −6.49 102 20 22.2 0.71 0.12 52 4.2 18 16.9 18.2 2.79 0.1 4.9 62 16.9 50 7.6 5.5 57 6 20.6 62 n.d. 535 28.5 8 77 n.d. 6 n.d. Fe TiO CoZr 37.5Ta 29.4 202 13.6 269 n.d. 9.8 194 0.94 21.2 201 0.72 14.7 159 0.88 11.2 159 0.95 14.5 190 1.21 16.6 172 0.75 10.1 178 0.83 8.8 0.54 201 8.2 0.86 182 12.6 0.86 24 46.7 n.d. 69 n.d. 77 n.d. CaOS 3.90 9.63 0.03 6.89 1.30 6.27 0.04 5.84 0.84 3.90 0.83 6.47 1.02 4.65 0.86 5.66 0.45 6.00 0.20 2.21 18.41 0.21 13.48 1.08 10.88 0.37 0.52 1.09 SamplesRocksSiO FHSB7 MRE JG6 PMD XQT3 PMD CS1 Mz DS8 DS4 QM XS1 QM XS5 QM SJC1 QMD SA1 QM SML QM MBS6 QM BMS2 PCE CSB1 HCE HGE K FeOMgONa 9.47LOI 6.04CO 5.55 3.26 3.32 1.31 1.91 4.54 0.76 1.73 5.07 1.10 2.55 3.98 0.50 2.09 2.47 1.01 1.89 2.93 1.06 2.24 3.91 0.70 2.49 3.02 1.13 1.05 2.80 0.99 0.99 3.97 1.32 11.47 9.16 1.69 8.57 8.34 2.68 6.86 2.87 0.84 Al TotalALKNa 99.24 7.8 100.26 99.83 7.0 100.93 7.8 99.87 100.32 8.3 99.79 7.5 100.14 100.16 9.2 99.85 9.3 100.75 8.7 99.84 99.47 8.2 100.08 8.0 11.4 1.7 3.1 4.7 MnO 0.24 0.14 0.18 0.08 0.16 0.08 0.10 0.09 0.11 0.12 0.10 0.28 0.18 0.20

Geological Society of America Bulletin, January/February 2014 87 Wu et al. . d . n ) O H S . ( d . s n e v a l c n E . d . n ) continued 8 7 . 5 5 O-CaO; ASI—molecular Al/(Ca – 1.67P + K + Na); AI—molecular + K Na); Al/(Ca – 1.67P ASI—molecular O-CaO; 2 3 e; HCB—amphibole-rich enclave; HGB—amphibole gabbro . rite; QMDP—porphyritic quartz monzodiorite; GD—granodiorite; GDP— 0 1 O + K 2 8 5 . 7 ) O 3 H 0 . S ( 7 s e i r e s c i t i n 5 o 3 . h 6 s o h S + MgO); Fe#—FeO/(FeO MALI—Na T 5 7 . 9 /(FeO T 8 2 . 8 3 3 . 7 9 9 . 0 1 TABLE 2. WHOLE-ROCK GEOCHEMICAL ANALYSES OF INTRUSIVE ROCKS AND ENCLAVES OF THE TONGLING DISTRICT ( DISTRICT TONGLING THE OF AND ENCLAVES OF INTRUSIVE ROCKS ANALYSES 2. WHOLE-ROCK GEOCHEMICAL TABLE ) A C . H ( d . s n e v 430 237 216 191 172 155 166 156 176 208 162 67 159 199 a l c n E n.d.—not determined; LOI—loss on ignition; ALK—total alkalis; Fe*—FeO n.d.—not determined; LOI—loss on ignition; Note: c REE Rb/Sr 0.48 0.08 0.10 0.06 0.12 0.24 0.11 0.18 0.08 0.11 0.44 0.17 0.00 0.11 PrGd 18.7Er 11.9 10.10 10.9 6.32 2.70 11.4 5.28 2.25 8.3 4.76 2.32 4.35 7.6 2.18 3.46 8.3 1.79 4.06 7.8 1.36 3.81 8.7 1.65 4.52 11.0 1.38 4.73 1.99 8.1 3.69 2.08 3.3 1.90 1.61 8.9 6.70 0.80 10.50 9.7 2.20 2.90 Eu*/EuBa/Rb 0.38 5.2 0.89 8.1 0.90 8.8 0.89 13.2 0.94 0.85 9.1 0.89 6.0 0.90 9.1 0.86 7.5 0.79 10.5 0.92 9.2 0.82 3.8 0.98 5.6 0.70 5.2 4.8 CeNdEuTb 194.0Ho 75.30 100.9Tm 1.50 43.70Lu 92.0Σ 1.30 39.70 2.26 1.10 72.5 1.12 0.31 40.20 1.95 0.93 72.8 0.40 0.82 30.80 0.25 1.76 0.84 67.2 0.35 27.30 0.75 0.36 1.62 1.14 71.9 29.90 0.30 0.63 0.31 1.22 0.65 28.20 67.5 0.31 0.56 0.27 1.48 31.40 0.50 74.0 0.37 0.62 0.22 1.41 36.10 0.64 88.8 0.23 0.61 0.32 28.70 1.55 0.55 70.5 0.28 0.70 14.00 0.16 1.60 0.77 28.6 0.11 0.78 37.60 0.31 1.39 0.78 58.4 41.10 0.28 0.63 0.36 0.60 0.63 74.5 0.25 0.30 0.25 2.40 0.30 0.19 1.10 0.12 2.20 0.90 0.10 1.20 0.35 1.20 0.30 0.41 0.30 BiBe 0.1 3.37 0.6 2.5 0.4 2.61 0.5 2.21 1.6Sr/Y 2.26 1.0 2.2 4.2 25.8 2.21 4.5 44.8 2.19 0.3 47.6 2.08 9.0 45.6 2.3 38.9 0.8 1.6 48.2 0.2 1.42 53.4 0.2 1.22 47.6 0.3 3.65 49.1 45.2 37.8 39.5 37.5 23.9 SmDy 13.30Yb 8.80 6.40 7.59 5.17 2.10 6.96 4.66 2.30 5.99 4.18 1.86 5.10 3.87 1.93 5.80 2.90 2.35 5.54 3.57 1.45 6.27 3.16 1.71 7.29 4.19 0.66 5.34 3.94 1.76 2.50 3.35 1.79 8.00 1.50 1.20 8.80 4.70 0.70 7.00 1.70 2.30 Al-(Na + K) > 0; An—whole-rock normative anorthite; REE—rare earth element. Rock names: GBD—gabbro-diorite; QMD—quartz monzodio Al-(Na + K) > 0; porphyritic granodiorite; GV—granite; PMD—pyroxene monzodiorite; Mz—monzonite; QM—quartz PCB—pyroxene-rich enclav MDE—microdiorite enclave; MQME—maﬁc quartz monzodiorite enclave; MRE—mica-enriched enclave. S AsSbLiMo 0.5 0.05 76.3 4.9 0.84 3.5 34 2.5 0.30 1.6 4.4 18.6 0.72 2.6 22.5 9.8 1.20 2.1 16.3 0.90 7.7 1.9 12.7 1.50 7.3 13.9 2.8 2.60 7.2 15.2 0.85 2.7 20 14.8 2.00 15.9 42.7 11.3 1.30 3.2 18.5 21.8 0.78 6.5 3.9 160 0.62 1.0 3.2 132 0.78 3.9 19.9 55.2 3.2 3.8 AgGa 0.11La 27.9 0.42 0.15 18.9 102.6 0.7 22.6 51.0 19.6 0.3 47.8 18.4 0.4 42.4 23.8 38.8 0.7 21.3 35.8 1 23.5 36.1 0.2 18.2 35.2 0.3 24.7 39.7 0.5 28.3 48.8 10.4 0.16 36.1 12.2 0.32 12.6 15.1 0.27 25.8 36.4 Pb 12.2 26.5 36.6 32.8 23 29.9 22.3 23.3 47.3 61.5 93.6 13.4 11.2 12.8 RocksThUZn MRE 35.00 PMD n.d. 335 11.01 PMD 3.36 11.14 74 Mz 2.18 9.20 151 QM 11.63 2.62 87 QM 11.54 2.54 10.74 QM 96 2.96 10.50 QMD 2.32 53 11.22 QM 2.16 58 9.40 QM 2.42 57 9.66 QM 2.05 6.00 101 PCE 2.21 7.00 98 HCE n.d. 11.00 109 HGE n.d. 303 n.d. 212 121 Cu 83 356 14 126 97 192 73 141 95 137 28 91 133 289 Samples FHSB7 JG6 XQT3 CS1 DS8 DS4 XS1 XS5 SJC1 SA1 SML MBS6 BMS2 CSB1

88 Geological Society of America Bulletin, January/February 2014 Petrogenesis of intermediate-acid intrusive rocks and zircon SHRIMP U-Pb dating in the Tongling area, Anhui Province (eastern China)

Eleven grains have ages ranging from 140 ± 1 Ma to 146 ± 1 Ma. After excluding grain 5, which has very high Th and U, the remaining 10 analyses yield a weighted average age of 143 ± 1 Ma (n = 10, mean square of weighted deviates [MSWD] = 2.9; Fig. 3A).

Sample SYSZK03 Sample SYSZK03 is a core sample of the Shujiadian pyroxene monzodiorite of the shoshonitic series taken from hole ZK03. The rock body occurs as a NE-trending stock with A an irregular shape. It is hosted in Silurian silt- stone with veinlet and disseminated gold mineralization. A large garnet skarn with an area of 2500 m2 occurs in the middle of the stock. The monzodiorite is dark gray, has a hypidiomorphic-granular texture, and consists mainly of plagioclase (An45–55) (60–70 modal%) and diopside (10%–15%), with subordinate biotite, potassium feldspar, and quartz (for a chemical analysis of this rock, see Wu et al., 1996). Zircon grains from this sample are prismatic, with length:width ratios between 1:1 and 2:1, similar to those of the Huchengjian gabbro- diorite. Most of the grains are uniformly gray in B their CL images, although a few display oscillatory zoning (such as grain 6) or a banded structure (such as grains 7 and 11; Fig. 2B), which is typical of magmatic zircon (Pidgeon et al., 1998). The grains have U contents ranging from 189 to 1086 ppm and Th ranging from 133 to 1705 ppm, giving Th/U ratios of 0.73–1.84, consistent with an igneous origin (Table 1). Eleven analyzed spots from this sample yielded a cluster of U-Pb ages ranging from 138 ± 1 Ma to 146 ± 1 Ma, with a weighted average age of 142 ± 2 Ma (n = 11, MSWD = 4.1) that is C regarded as the crystallization age (Fig. 3B).

Sample FHS2 Sample FHS2 is from the Fenghuangshan granodiorite of the high-K, calc-alkaline series, the largest intrusive body in the area. This body forms a stock with an irregular circular outcrop area of ~10 km2. The rock is light colored and consists chieﬂ y of plagioclase (45–55 modal%), quartz (15%–20%), and alkali feldspar (10%– 15%), accompanied by minor amphibole and biotite. An analysis of this rock is given in Table 2. Zircon grains in this sample are prismatic, with length:width ratios of 2:1–3:1, and they show good oscillatory zoning in CL images (Fig. 2C). The analyzed grains have U contents ranging from 225 to 573 ppm and Th ranging from 79 to 481 ppm, giving Th/U ratios ranging D from 0.59 to 1.13, except for grain 1, which has a ratio of 0.27, still within the range of igne- Figure 2. Cathodoluminescence (CL) images of zircon from the intrusive rocks in the ous zircon (>0.2). Eleven analyzed grains yield Tongling district.

Geological Society of America Bulletin, January/February 2014 89 Wu et al.

A B

C D

Figure 3. Zircon 238U/206Pb-207Pb/206Pb concordia diagrams for the intrusive rocks in Tongling. MSWD—mean square of weighted deviates.

206Pb/208U ages ranging from 140 ± 1 Ma to grains have relatively low contents of U and Th very low Th (18–45 ppm), except for two grains 691 ± 4 Ma. If grains 1, 3, and 11, which con- (242–386 ppm and 18–93 ppm, respectively), with 93 and 77 ppm Th that are clearly xeno- tain inherited cores (531 ± 3 Ma, 691 ± 4 Ma, yielding Th/U ratios of 0.06–0.53, which are crysts. Except for these obviously xenocrystic and 235 ± 2 Ma, respectively; Fig. 2C), are considerable lower than zircons from the other grains, the zircons all appear to be magmatic in rejected, the remaining grains yield a weighted samples (Table 1). These low ratios are due pri- origin and are believed to date the time of crys- average age of 142 ± 1 Ma (n = 8, MSWD = marily to very low Th contents (18–93 ppm). tallization of the various Tongling bodies. 1.1; Fig. 3C). Grains 5 and 7, which have inherited cores, have the highest Th values and highest Th/U Geochemistry Sample YSZ3 ratios. The inherited cores in these two grains Sample YSZ3 is from the Yaoshan porphy- (with three analyses) yielded 207Pb/206Pb ages of Intrusive Rocks ritic granodiorite of the high-K, calc-alkaline 2330 ± 12 Ma and 2104 ± 13 Ma, respectively, Most of the analyzed intrusive rocks from the series, which crops out west of the Fenghuang- and were discarded. The remaining eight ana- Tongling district are fresh, with loss on ignition shan intrusion (Fig. 1B). It forms a sill with an lyzed spots on seven grains yielded 206Pb/238U (LOI) < 2 wt% (Table 2). Two samples from the outcrop area of 3 km2 that is connected to the ages ranging from 144 ± 1 Ma to 149 ± 1 Ma, calc- alkaline series (XQT4 and YSZ2) have

Xingqiao porphyritic granodiorite in the north- with a weighted average age of 146 ± 1 Ma (n = LOI >3 wt% and are depleted in Na2O, indi- east. The rock is characterized by phenocrysts 8, MSWD = 0.8), which is considered the age of cating moderate alteration. All but these two of plagioclase and quartz, ranging up to 2 cm zircon crystallization (Fig. 3D). samples have relatively high total alkalis, with across, which are set in a fi ne-grained, felsic The wide range in Th/U ratios for the zircons enrichment in K2O, placing them in the shosho- matrix. A chemical analysis of this sample is both within and between individual samples is nitic fi eld and upper parts of the calc-alkaline given in Table 2. puzzling. For example, the analyzed zircons fi eld in the SiO2 versus (Na2O + K2O) diagram Zircon grains from this sample are elongate, from sample SYSZK have Th/U ratios ranging (Fig. 4) (Middlemost, 1994; Irvine and Baragar, euhedral prisms with length:width ratios of 2:1– from 0.73 to 1.84, but they all have very simi- 1971). On the SiO2 versus K2O diagram (Pec- 4:1. CL images show that the grains have excel- lar ages and all appear to be magmatic in form cerillo and Taylor, 1976) (Fig. 5), they plot in lent oscillatory zoning, indicating an igneous and internal texture. In contrast, all zircons from the high-K, calc-alkaline and shoshonite fi elds, origin (Fig. 2D). Eleven analyzed points on nine sample YSZ3 have low U (182–386 ppm) and respectively. Most of the intrusive rocks (>90%)

90 Geological Society of America Bulletin, January/February 2014 Petrogenesis of intermediate-acid intrusive rocks and zircon SHRIMP U-Pb dating in the Tongling area, Anhui Province (eastern China)

Ba, results in a rapid decrease in the Ba/Rb ratio for these rocks. Zirconium shows a broad scatter of values in the calc-alkaline rocks but decreases regularly in the shoshonitic series (Fig. 8), whereas Y decreases systematically

as SiO2 increases, resulting in generally posi-

tive correlations between Sr/Y ratios and SiO2 contents, particularly in the calc-alkaline series. One anomalous geochemical feature of these rocks is their relatively high Cr contents (up to 129 ppm in the calc-alkaline series and 210 ppm in the shoshonitic series; Table 2). Not only do the rocks have high Cr contents, but there is a crude positive correlation between Cr and

SiO2 (Fig. 8). This trend is particularly puzzling because the other transition metals (Ni, Co, V,

Figure 4. Diagram of SiO2-(Na2O + K2O) for the rocks in Tongling and Sc) all decrease systematically with increas-

(after Middlemost, 1994; Irvine and Baragar, 1971); the dashed line ing SiO2. It may refl ect injection of more mafi c represents that the plot fi eld of more than 400 collected analyses of melts into the magma chamber. the intrusive rocks in Tongling. Circles—intrusive rocks of the high-K, Rocks of the high-K, calc-alkaline series calc-alkaline series. Squares—intrusive rocks of shoshonitic series. have ΣREE of 65–197 ppm, with most samples in the range of 140–180 ppm, and they show no

systematic change with SiO2 (Table 2). Chon- belong to the high-K, calc-alkaline series and (Table 2), indicating they are metaluminous drite-normalized REE patterns of these rocks range in composition from maﬁ c to intermedi- (Frost et al., 2001). are quite uniform, with nearly ﬂ at heavy (H)

ate, with SiO2 contents between 52.6 and 64.3 In the Harker diagrams, TiO2, Al2O3, Fe2O3, REE segments and signiﬁ cant light (L) REE

wt%, and K2O contents between 2 and 4 wt%; FeO, MgO, CaO, and P2O5 all show relatively enrichment (LREE/HREE = 8.4–19.3; aver- one sample of granite has 75.4 wt% SiO2 and 4 systematic decreases in concentration with age = 12.5). They have negligible to very weak

wt% K2O (Table 2). Although rocks of the sho- increasing SiO2, as expected for granitoid mag- negative Eu anomalies (Eu*/Eu = 0.78–0.98; shonitic series have similar SiO2 contents (50.8– mas undergoing fractionation (Fig. 7). However, Figs. 9A–9B). These patterns are similar to

65.2 wt%), they have much higher total alkalis the granite sample (TGS3) with 75.4 wt% SiO2 those of average upper-crustal rocks (Taylor and

(7.4–11.4 wt%), with K2O contents generally is completely separated from the other calc- McClennan, 1985). between 3 and 5 wt%. One sample (SML2) has alkaline rocks (Fig. 7), and its origin is unclear. The ΣREE values in the shoshonitic series

10 wt% K2O with very low Na2O and slightly Except for three samples, Na2O contents range range from 155 to 237 ppm, i.e., slightly higher elevated LOI (Table 2), suggesting some altera- between 3.3 and 5.5 wt% and show no system- on average than in the high-K, calc-alkaline

tion. Rocks from both series are mostly mag- atic variation with SiO2; in contrast, K2O shows

nesian, with only a few ferroan samples (Frost a positive correlation with SiO2 in both the calc- et al., 2001; Frost and Frost, 2008). Both series alkaline and shoshonitic series (Table 2; Fig. 7). are alkali-calcic to calc-alkaline on the basis of The large ion lithophile elements show con- the modiﬁ ed alkali lime index (MALI) (Frost siderable scatter on the Harker diagrams but

et al., 2001) (Fig. 6). All of the rocks have generally increase with increasing SiO2 (Fig. 8).

ASI values (= Al/[Ca – 1.67P + Na + K]) <1 An increase in Rb with increasing SiO2 in the and AI values (= molecular Al – [Na + K]) >0 shoshonitic series, coupled with nearly constant

Figure 5. Diagram of SiO2-K2O for the Tongling rocks (after Peccerillo and Taylor, 1976).

Symbols are the same as those Figure 6. Diagram of SiO2 vs. modified in Figure 4. K—potassium. alkali lime index (MALI) for the Tongling rocks (after Frost et al., 2001; Frost and Frost, 2008). Symbols are the same as those in Figure 4. A—alkaline series, AC—alkali- calcic series, CA—calc-alkaline series, C— calcic series.

Geological Society of America Bulletin, January/February 2014 91 Wu et al.

Figure 7. Harker diagrams for the major elements (wt%). Data are from Table 2. Symbols are the same as those in Figure 4. series, and they show a systematic decrease with HREE = 11.1–13.9; average = 12.3; Fig. 9C). increasing SiO2, although the range of SiO2 is Likewise, they also have very weak negative Eu quite narrow (50.8–62.3 wt%; Table 2). We inter- anomalies (Eu*/Eu = 0.79–0.92; Table 2). pret this trend as possibly refl ecting early crystal- In the primitive mantle–normalized trace- lization of titanite, one of the major carriers of element diagram, rocks of the high-K, calc- REEs in these rocks. Experiments by Prowatke alkaline series show strong enrichment in large and Klemme (2006) and measured mineral/glass ion lithophile elements (LILEs; Rb, Ba, Th, data (Bachmann et al., 2005; Colombini et al., K), marked negative anomalies in Nb and Ti, 2011) demonstrate that distribution coeffi cients and weak negative anomalies in P and Nd. The Figure 8. Harker diagrams for selected trace for the middle REEs in titanite are very high negative Nb suggests a subduction component elements (ppm). Data are from Table 2. and hence should lead to noticeable depletion in in the source area, as does the enrichment in Symbols are the same as those in Figure 4. these elements. We calculated middle (M) REE LILEs. Most samples also show weak enrich- depletion factors (2Gdn/[Lan × Lun]) for the sho- ment in Sr and Zr (Figs. 10A–10B). Rocks of shonitic rocks, which range from 0.64 to 0.23, the shoshonitic series generally have trace- character. Despite the higher K2O contents of compatible with some titanite fractionation. element compositions comparable to the calc- these rocks, their Rb concentrations overlap Chondrite-normalized REE patterns for the sho- alkaline rocks, except for somewhat higher those of the calc-alkaline series (Table 2). The shonitic rocks are indistinguishable from those values for some of the transition elements, par- primitive mantle–normalized trace-element of the calc-alkaline series, showing the same fl at ticularly Cr, V, and Co, and somewhat lower patterns of the two series are very similar HREE portion and LREE enrichment (LREE/ values of Sr and Ba, refl ecting their more mafi c (Fig. 10C).

92 Geological Society of America Bulletin, January/February 2014 Petrogenesis of intermediate-acid intrusive rocks and zircon SHRIMP U-Pb dating in the Tongling area, Anhui Province (eastern China)

FeOt, MgO, and K2O than the others. The ΣREEs are quite variable in the calc-alkaline enclaves, being highest in the mica-rich variety; however, all of the enclaves in the calc-alkaline series, except for the mica-rich samples, have similar chondrite-normalized patterns with strong LREE enrichment and very weak negative Eu anomalies (Fig. 9D). These enclaves have rather variable mantle-normalized trace- A element patterns but generally show strong enrichment in LILEs and marked negative Nb anomalies, but they lack the positive P anomalies of the enclaves in the shoshonitic series (Fig. 10D). The maﬁ c quartz monzodiorite enclave is similar in composition to its host rock but with higher FeOt and MgO and correspond- ing decreases in most other oxides. On the other hand, the mica-rich enclave contains relatively high contents of transition metals, particularly Cr, Ni, V, and Co, suggesting that it is refractory B crustal material that is a relict of crustal partial melting. No metasedimentary rocks of this composition are currently known in the sedimentary sequence overlying the basement; however, the presence of cordierite and garnet suggests that these may be contact metamorphic rocks. The pyroxene-rich and amphibole-rich enclaves in the shoshonitic series are charac-

terized by having lower SiO2, K2O, Na2O, and

Al2O3 but signiﬁ cantly higher MgO and CaO than their host rocks, consistent with their high contents of clinopyroxene and amphibole C (Table 2). Both the Fe# (= FeO/[FeO + MgO]) and ΣREE values increase regularly from the pyroxene-rich through the amphibole-rich to the amphibole gabbro enclave (Table 2). The chondrite-normalized REE patterns of these enclaves are similar to those of the host rocks, with LREE enrichment and very weak negative Eu anomalies (Fig. 9D). Their primitive mantle– normalized trace-element patterns are similar, showing marked negative anomalies in Nb, Zr, and Ba and positive anomalies in Th, La, P, and Sm (Fig. 10D). On the basis of their textures and D geochemistry, these enclaves are considered to be magmatic in origin.

Mineral Chemistry Figure 9. Chondrite-normalized rare earth element (REE) distribution patterns for the intrusive rocks and enclaves from Tongling. Plagioclase (A, B) High-K, calc-alkaline series intrusive rocks. (C) Shoshonitic Plagioclase is the principal mineral in all series intrusive rocks. (D) Enclaves from rocks of both series. Nor- the rocks. In the high-K, calc-alkaline series, it malizing values are from Taylor and McLennan (1985). mostly ranges from An25 to An35, but a few grains in the gabbro-diorite and porphyritic quartz

monzodiorite have compositions of An42–82 Enclaves similar major-oxide compositions, generally (Table 3). Because the rocks of the shoshonitic The various enclaves range widely in chemi- close to those of their host rocks, but somewhat series are more mafi c, they contain more calcic cal composition because of their different ori- enriched in FeOt and MgO (Table 2). The mica- plagioclase (An42–53). Plagioclase in the micro- gins. The microdiorite and quartz monzodiorite rich enclave is characterized by signifi cantly diorite and mafi c quartz monzodiorite enclaves enclaves in the high-K, calc-alkaline series have lower SiO2 and Na2O but higher TiO2, Al2O3, (An43–32) generally has compositions similar to

Geological Society of America Bulletin, January/February 2014 93 Wu et al.

Fe3+) in the amphibole-rich and amphibole gabbro enclaves (Table 5).

Biotite Biotite is present in most of the rocks, either as a primary mineral or replacing amphibole A and pyroxene. Some of the biotite has been altered to chlorite and calcite along cleavage planes, and in one case, biotite phenocrysts in granodiorite porphyry are corroded and rimmed by amphibole, possibly the result of magma mixing. The biotite in the mica-rich enclaves

is rich in Al2O3 and FeO, whereas that in the pyroxene- and amphibole-rich enclaves is rich Figure 10. Primitive mantle– in MgO (Table 6). normalized trace-element spider B diagrams. (A, B) Intrusive rocks Clinopyroxene of the high-K, calc-alkaline Clinopyroxene mainly occurs in the pyroxene series . (C) Intrusive rocks of the monzodiorites and monzonites of the shosho- shoshonitic series. (D) Enclaves nitic series, with some in the gabbro-diorites. from rocks of both series. Nor- It occurs both as relatively large, idiomorphic malizing values are from Sun prisms and as fine, granular material com- and McDonough (1989). monly replacing amphibole. The replacement of C amphibole by clinopyroxene may reﬂ ect injection of basic melts into silicic magma. Com- monly, large pseudomorphs of actinolite after clinopyroxene coexist with small, fresh crystals of clinopyroxene. This implies either that the large phenocrysts were greatly out of equilib- rium with the coexisting melt after mixing, and were replaced by amphibole, or that the small clinopyroxene grains grew after replacement of the phenocrysts by the actinolite. All of the D clinopyroxene, both in the granitoid rocks and in the enclaves, is diopside (Poldervaart and Hess, 1951; Morimoto et al., 1988) (Table 7).

DISCUSSION those in the host rocks (Table 3). However, some Amphibole plagioclase phenocrysts in the microdiorite Amphibole is the most abundant mafi c Sequence of Magmatic Activity enclaves are more sodic (An20) than the ground- mineral in all the intrusive rocks, in which it mass grains (An35), suggesting that the pheno- commonly occurs as elongate prisms. Some Our SHRIMP U-Pb zircon ages for the intru- crysts crystallized from an early, more felsic amphiboles have been partially replaced by sive rocks of the high-K, calc-alkaline series magma and were added to the enclaves during fi ne-grained (0.05 mm) aggregates of granular include 143 ± 1 Ma for the Huchengjian body, later magma mixing. diopside and magnetite. Small, acicular amphi- 142 ± 1 Ma for the Fenghuangshan body, and bole grains occur as inclusions in quartz in some 146 ± 1 Ma for the Yaoshan body. Other zir- Potassium Feldspar quartz monzodiorites and granodiorites of the con SHRIMP U-Pb ages for the high-K, calc- Potassium feldspar has several different high-K, calc-alkaline series, perhaps refl ecting alkaline series include: 140 ± 2 Ma for the Jitou modes of occurrence in the different rocks. In quick cooling during magma mixing. On the body (Wang et al., 2004c); 137 ± 1 Ma (X.S. Xu the quartz monzonite and monzonite, it forms basis of the classifi cation scheme of Leake et al. et al., 2004), 139 ± 3 Ma (Wang et al., 2004b), large crystals with many small plagioclase inclu- (1997) (Table 5), the amphiboles belong to the 139 ± 3 Ma (Du et al., 2004), 143 ± 2 Ma (Di ≥ ≥ sions, whereas in some of the granodiorites, calcic subfamily (CaB 1.50, [Na + K] 0.5, Ti et al., 2005), and 142 ± 1 Ma (Wu et al., 2010b) large potassium feldspar grains contain inclu- < 0.5) and to edenite (Si > 6.5) in the intrusive for the Tongguanshan quartz monzodiorite; sions of both plagioclase and amphibole. Fine- rocks of both series and in the microdiorite and 152 ± 3 Ma for the Shatanjiao body (Di et al., grained, interstitial, granular potassium feldspar mafi c quartz monzodiorite enclaves. All of the 2005); and 144 ± 2 Ma for the Fenghuangshan generally occurs in all the intrusive rocks and amphibole in the pyroxene- and amphibole-rich body (Zhang et al., 2006). These dates imply enclaves. Most of the potassium feldspar in the enclaves is also calcic in character, but it is clas- that the high-K, calc-alkaline series magma- intrusive rocks is orthoclase, but some grains in sifi ed as pargasite (5.5 < Si < 6.5; AlVI ≥ Fe3+) tism may have begun as early as 152 Ma and the pyroxene monzodiorite of the shoshonitic in the pyroxene-rich varieties and as pargasite lasted until ca. 138 Ma, with most of the activity VI ≤ series have more Na2O than K2O (Table 4). and magnesiohastingsite (5.5 < Si <6.5; Al occurring between 146 and 139 Ma.

94 Geological Society of America Bulletin, January/February 2014 Petrogenesis of intermediate-acid intrusive rocks and zircon SHRIMP U-Pb dating in the Tongling area, Anhui Province (eastern China) E R M E M D Q G M z monzodiorite; GD—granodiorite; GDP—porphyritic granodiorite; ave; HGB—amphibole gabbro enclave; MDE—microdiorite E D M D E G M H Q M Q TABLE 3. MICROPROBE ANALYSES OF PLAGIOCLASE IN INTRUSIVE ROCKS OF TONGLING OF PLAGIOCLASE IN INTRUSIVE ROCKS ANALYSES 3. MICROPROBE TABLE z M P D M Q D M P D B G D G 0.023 0.012 0.015 0.019 0.004 0.006 0.012 0.009 0.010 0.005 0.005 0.013 0.006 0.009 0.006 0.005 0.59 0.33 0.4 0.5 0.1 0.16 0.32 0.22 0.270.08 0.130.15 0.00 0.12 0.41 0.04 0.35 0.07 0.01 0.15 0.42 0.06 0.24 0.29 0.08 0.17 0.35 0.06 0.14 0.62 0.11 0.21 0.28 0 0.00 0.04 0.13 0.00 0 0.05 0.18 0.08 0.14 0.00 0.28 0.00 0.05 0.31 0.03 0.04 0.08 0.08 0.00 0.00 0.07 0.02 0.00 0.03 0.00 0.10 0.00 0.00 0.00 0.12 0.00 0.04 0.00 0.00 0.10 0.00 0.00 0.06 0.00 0.000.00 0.12 0.00 0.160.006 0.00 0.016 0.00 0.05 0.003 0.00 0.09 0.016 0.00 0.00 0.011 0.00 0.013 0.00 0.023 0.00 0.008 0.00 0.000 0.00 0.005 0.25 0.000 0.00 0.007 0.005 0.00 0.011 0.00 0.002 0.00 0.012 0.00 32.65 28.31 27.41 27.46 25.2 23.55 25.27 24.1 25.97 24.1563.1 24.7123.83 24.17 55.8 28.42 25.23 55.93 27.6 24.68 54.4 27.74 25.66 57.3 26.13 24.4 55.08 28.25 56.23 26.86 62.21 24.13 57.77 26.44 58.35 24.6 59.66 24.66 63.33 22.14 59.67 25.25 61.02 24.31 47.45 33.79 45.94 35.3 47.07 56.09 57.76 57.26 60.35 61.48 58.03 58.93 58.98 60.78 60.7 59.62 60.77 59.73 62.22 An—anorthite; Ab—albite; Or—potassium feldspar. Rock names: GBD—gabbro-diorite; QMD—quartz monzodiorite; QMDP—porphyritic quart Ab—albite; Or—potassium feldspar. An—anorthite; s s 3 3 T T 5 5 k k 2 2 O 7.78 4.87 5.65 4.98 6.38 5.52 5.49 6.66 6.39 7.38 6.76 8.39 7.73 6.52 2.02 1.15 O 2.01 5.63 4.96 5.95 6.65 7.64 6.58 7.35 6.9 7.7 7.34 7.53 6.73 6.87 6.6 7.64 2 2 2 c 2 c O O T T O 0.03 0.28 0.5 0.32 0.52 0.21 0.41 0.58O 0.50 0.700.250.300.510.290.450.470.270.130.300.340.270.220.430.090.00 0.21 0.42 0.51 0.53 0.26 0.46 0.54 O O Note: 2 2 o o 2 2 2 2 SiO Total 4.944 4.946 4.996 4.999 4.997 5.019 4.996 4.912 4.983 5.001 4.852 4.952 5.018 4.915 5.018 4.992 P TotalOrAbAn 5.015Samples 0.2 17.7 4.997 82.1 QTY1 4.909 49.5 1.6 48.9 JG6 4.968 52.5 3.5 SJD1 44.0 4.936 56.3 CS1 2.0 41.8 4.960 64.5 XS5 32.2 4.991 3.3 69.8 5.003 JC1 29.0 1.2 58.8 5.010 38.8 2.4 4.984 CSB1 64.7 32.0 4.999 3.4 59.9 37.2 4.999 67.9 2.9 TGS2-B 30.9 4.989 63.4 1.2 4.956 34.2 64.7 4.958 FHSB4 32.4 2.4 4.949 59.8 37.1 2.9 62.7 35.8 TEBDB6 3.1 61.3 35.8 1.6 72.9 23.7 FHSB7 2.8 3.4 CaO 4.04 9.47 10.08 10.72 8.55 9.87 9.93 6.08 8.75 7.12 6.88 3.9 6.99 5.72 17 17.85 Fe Total 99.95Mn 99.25 99.79 0.000 98.99 0.000 99.24 0.000 100.38 0.006 99.82 0.000 100.01 0.008 100.06 0.000 98.01 0.000 98.99 0.003 98.19 100.41 0.000 98.63 0.005 100.72 0.002 100.55 0.014 0.000 0.002 0.000 POrAb 0.000 4.4 74.3 0.000 47.4 1.6 0.000 0.002 49. 1.7 0.003 44.3 3.0 0.000 56.5 0.000 1.7 49.0 0.000 2.6 0.000 48.6 2.7 0.000 65.3 0.010 1.7 56.5 0.000 0.8 64.0 0.000 62.7 1.7 0.000 78.3 0.000 2.1 0.000 65.9 1.7 65.4 1.2 17.6 2.9 10.6 0.5 0.0 P R K 0.002 0.016 0.029 0.018 0.030 0.012 0.024 0.034 0.028 0.012 0.024 0.029 0.030 0.015 0.026 0.030 CaO 16.88 10.06 7.51 7.99 6 5.75 7.87 6.58 7.75Na 6.35 7.15 6.83 7.56 7.09 6.98 4.5 Samples HCJZK1 MJ1 SJC1 TEBD1 TGS1 JT4 QSJ1 BC1 ZC WGQ HC1 DTS2 FHS1 XQT4 STJ3 R TotalSi 99.34 100.83 2.183 99.25 2.505 99.67 2.590 99.18 2.570 98.85 2.697 98.86 2.755 98.03 2.631 100.38 2.685 99.47 2.630 99.82 2.717 100.57 2.670 99.11 2.669 100.13 2.648 99.81 2.699 99.85 2.664 2.752 SiTiMg 2.785 0.003 2.518 0.000 0.014 2.522 0.001 0.002 2.485 0.000 0.000 2.588 0.002 0.000 2.483 0.003 0.010 2.541 0.002 0.011 2.748 0.004 0.010 2.582 0.009 0.017 2.653 0.000 0.015 2.676 0.001 0.008 2.836 0.000 0.019 2.658 0.002 0.008 2.735 0.003 0.000 2.157 0.000 0.015 2.100 0.000 0.017 0.000 An 21.3 51.0 48.8 52.7 41.8 48.4 48.6 33.0 42.7 34.1 35.3 20.1 32.9 31.7 81.9 89.4 GV—granite; PMD—pyroxene monzodiorite; Mz—monzonite; QM—quartz PCB—pyroxene-rich enclave; HCB—amphibole-rich encl MQME—maﬁc quartz monzodiorite enclave; MRE—mica-enriched enclave. SiO TiO P 0.000 0.002 0.000 0.000 0.004 0.000 0.000 0.002 0.000 0.000 0.004 0.006 0.000 0.000 0.000 0.000 K FeO TiO Al MnO 0.00 0.00 0.00 0.16 0.00 0.21 0.00 0.01 0.08 0.01 0.12 0.04 0.36 0.00 0.04 0.00 Na TiAl 0.001 1.784 0.001 1.490 0.003 1.448 0.003 1.452 0.000 1.330 0.000 1.244 0.003 1.350 0.001 1.294 0.000 1.365 0.001 1.273 0.000 1.304 0.003 1.303 0.000 1.342 0.000 1.293 0.000 1.349 0.004 1.272 AlCaNa 1.239 1.512 0.191 0.666 1.467 0.458 0.426 1.494 0.487 0.494 1.391 0.525 0.441 1.501 0.414 0.558 1.430 0.477 0.483 1.257 0.481 0.481 1.393 0.288 0.571 1.319 0.419 0.554 1.304 0.347 0.651 1.168 0.331 0.588 1.325 0.187 0.729 1.284 0.334 0.668 1.810 0.275 0.567 1.900 0.828 0.178 0.876 0.104 K MnMgCaNa 0.001 0.000 0.839 0.002 0.181 0.000 0.481 0.004 0.487 0.022 0.361 0.000 0.431 0.000 0.384 0.006 0.518 0.003 0.287 0.000 0.576 0.000 0.276 0.000 0.664 0.000 0.382 0.000 0.579 0.004 0.321 0.000 0.649 0.000 0.370 0.000 0.596 0.000 0.304 0.000 0.667 0.000 0.343 0.000 0.637 0.010 0.322 0.001 0.642 0.000 0.366 0.001 0.589 0.009 0.337 0.002 0.592 0.000 0.334 0.000 0.571 0.015 0.213 0.655 MnOMgO 0.03 0.00 0.04 0.00 0.09 0.33 0.00 0.00 0.15 0.05 0.00 0.00 0.00 0.00 0.00 0.06 0.01MgO 0.00 0.00 0.00 0.21 0.00 0.00 0.03 0.00 0.15 0.00 0.02 0.00 0.00 0.03 0.14 0.14 0.06 0.00 0.16 0.00 0.22 0.15 0.26 0.22 0.12 0.28 0.12 0.00 0.22 0.25 0.00 Fe K 0.039 0.015 0.017 0.030 0.017 0.026 0.027 0.015 0.008 0.018 0.019 0.016 0.012 0.025 0.006 0.000 Al FeO

Geological Society of America Bulletin, January/February 2014 95 Wu et al.

TABLE 4. MICROPROBE ANALYSES OF ALKALI FELDSPAR IN INTRUSIVE ROCKS OF TONGLING Samples XS5 JGS2 TGS1 JT4 FHS1 XQT4 JG6 CSB1 FHSB4 TEBDB6 Rock QM QMD GD GDP PMD HGE MDE MQME

SiO2 64.67 64.58 65.30 66.15 62.73 64.83 62.56 64.99 69.17 65.53 64.75 65.63 TiO2 0.02 0.33 0.00 0.04 0.38 0.26 0.84 0.28 0.00 0.15 0.21 0.00 Al2O3 17.45 19.04 17.52 17.90 18.42 17.97 18.85 19.19 18.75 18.41 17.95 17.85 FeOT 0.00 0.14 0.30 0.33 0.20 0.16 0.06 0.52 0.09 0.32 0.22 0.15 MnO 0.00 0.02 0.00 0.06 0.07 0.12 0.24 0.00 0.00 0.00 0.00 0.00 MgO 0.00 0.00 0.00 0.00 0.00 0.00 0.08 0.08 0.00 0.24 0.06 0.00 CaO 0.00 0.00 0.27 0.00 0.00 0.01 0.00 0.15 0.21 0.02 0.03 0.00

Na2O 0.98 1.12 0.87 0.92 2.38 1.42 0.84 1.32 4.65 0.84 1.12 1.05 K2O 15.05 15.64 15.11 15.19 11.92 14.58 14.96 14.46 6.89 14.04 15.03 15.28 P2O5 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.03 Total 98.17 100.87 99.57 99.78 96.10 99.38 98.43 100.99 99.79 99.61 99.37 99.99 Si 3.030 2.961 3.023 3.033 2.974 3.002 2.936 2.962 3.062 3.007 2.998 3.020 Ti 0.001 0.011 0.000 0.001 0.014 0.009 0.030 0.010 0.000 0.005 0.007 0.000 Al 0.963 1.029 0.956 0.967 1.030 0.980 1.043 1.031 0.978 0.996 0.979 0.968 FeT 0.000 0.005 0.012 0.013 0.008 0.006 0.002 0.020 0.004 0.012 0.009 0.006 Mn 0.000 0.001 0.000 0.002 0.003 0.005 0.010 0.000 0.000 0.000 0.000 0.000 Mg 0.000 0.000 0.000 0.000 0.000 0.000 0.006 0.006 0.000 0.017 0.004 0.000 Ca 0.000 0.000 0.013 0.000 0.000 0.001 0.000 0.007 0.010 0.001 0.001 0.000 Na 0.089 0.099 0.078 0.082 0.219 0.127 0.077 0.117 0.399 0.075 0.101 0.093 K 0.899 0.915 0.892 0.830 0.721 0.861 0.896 0.841 0.389 0.822 0.888 0.897 P 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.001 Total 4.982 5.021 4.981 4.934 4.967 4.993 4.998 4.992 4.843 4.938 4.988 4.985 Or 91.0 90.2 90.7 91.1 76.7 87.1 92.1 87.1 48.8 91.5 89.7 90.6 Ab 9.0 9.8 7.9 9.0 23.3 12.9 7.9 12.1 50.0 8.4 10.2 9.4 An 0.0 0.0 1.4 0.0 0.0 0.1 0.0 0.8 1.2 0.1 0.1 0.0 Note: An—anorthite; Ab—albite; Or—potassium feldspar. Rock names: GBD—gabbro-diorite; QMD—quartz monzodiorite; QMDP—porphyritic quartz monzodiorite; GD— granodiorite; GDP—porphyritic granodiorite; GV—granite; PMD—pyroxene monzodiorite; Mz—monzonite; QM—quartz monzodiorite; PCB—pyroxene-rich enclave; HCB— amphibole-rich enclave; HGB—amphibole gabbro enclave; MDE—microdiorite enclave; MQME—maﬁc quartz monzodiorite enclave; MRE—mica-enriched enclave.

Zircon SHRIMP U-Pb ages for the shosho- shonitic magmatic activity may have begun Magma Sources nitic intrusive rocks include our date of 142 ± around 143 Ma and lasted until ca. 136 Ma. 2 Ma for the Shujiadian pyroxene monzodio- However, where available, the intrusive rela- Zircon SHRIMP U-Pb dating can yield rite and a date of 136 Ma (Wu et al., 2013) for tionships indicate that the shoshonitic bodies not only the crystallization ages of intrusive the Jiaochong pyroxene monzodiorite, a date postdate the high-K, calc-alkaline bodies. rocks, but it can also provide some constraints of 138 ± 1 Ma for the Baimangshan pyroxene The intrusive activity began with the grano- on the ages of their source rocks. In addition, monzodiorite (Wu et al., 2008), and a date of diorite porphyry and granodiorite, was followed the CL images of the zircons can provide 143 ± 1 Ma for the Caoshan monzonite (Wang by the gabbro-diorite, and culminated with the information on their metamorphic and mag- et al., 2004a). These ages suggest that the sho- quartz monzodiorite and pyroxene monzodiorite. matic history.

TABLE 5. MICROPROBE ANALYSES OF AMPHIBOLE IN INTRUSIVE ROCKS OF TONGLING Location TGS1 TEBD1 FHS1 JG6 CS1 BMS6 BMS2 Rocks QMD GD PMD Mz PCE HCE Mineral Edenite Pargasite MH

SiO2 46.75 50.36 47.15 50.08 47.74 49.29 47.46 49.72 42.19 42.32 40.52 40.07 40.52 40.39 TiO2 1.52 0.90 1.07 1.04 1.25 1.44 1.66 0.96 0.56 0.50 2.40 3.09 3.66 2.76 Al2O3 7.82 5.16 5.58 5.73 6.74 5.80 7.17 5.40 14.24 14.51 13.11 13.08 13.43 13.55 FeOT 14.17 13.25 14.15 12.91 14.91 12.73 14.53 12.52 6.07 6.17 11.39 13.11 12.79 11.90

Fe2O3 7.22 7.32 9.09 7.61 4.92 5.89 7.12 5.24 1.60 2.41 0.63 1.41 2.87 4.89 FeO 7.67 6.67 5.97 6.06 10.49 7.43 8.12 7.81 4.63 4.01 10.83 11.84 10.21 7.50 MnO 0.69 0.83 0.71 0.63 0.60 0.71 0.58 0.72 0.14 0.05 0.18 0.29 0.18 0.10 MgO 12.90 14.97 14.05 15.01 12.99 14.17 13.14 14.40 15.96 16.16 13.97 11.38 11.89 12.59 CaO 10.17 10.71 10.38 10.25 10.89 10.32 10.54 10.74 13.23 13.26 11.81 11.14 10.67 10.88

Na2O 1.73 1.60 1.53 1.75 1.86 1.48 1.47 1.29 2.28 2.03 2.47 3.03 3.26 2.57 K2O 0.77 0.48 0.59 0.78 0.73 0.68 0.68 0.60 1.39 1.53 1.11 1.01 0.99 1.08 Total 96.52 98.26 95.21 98.18 97.71 96.71 97.23 96.35 96.06 96.53 97.07 96.20 97.39 95.91 Si 6.846 7.177 6.966 7.120 6.976 7.147 6.902 7.233 6.164 6.141 6.017 6.058 5.996 6.014 AlIV 1.154 0.823 1.034 0.880 1.024 0.853 1.098 0.767 1.836 1.859 1.983 1.942 2.004 1.986 AlVI 0.196 0.044 –0.063 0.080 0.137 0.139 0.131 0.160 0.617 0.623 0.312 0.389 0.338 0.392 Ti 0.167 0.097 0.119 0.111 0.137 0.157 0.182 0.105 0.062 0.055 0.268 0.352 0.407 0.309 AlT 1.350 0.867 0.971 0.960 1.161 0.992 1.229 0.927 2.453 2.482 2.295 2.331 2.342 2.378 FeT 1.735 1.579 1.748 1.535 1.822 1.544 1.767 1.524 0.742 0.749 1.414 1.658 1.582 1.482 Fe3+ 0.796 0.785 1.010 0.815 0.541 0.642 0.779 0.573 0.175 0.263 0.070 0.160 0.319 0.548 Fe2+ 0.940 0.794 0.738 0.720 1.281 0.901 0.988 0.950 0.566 0.486 1.344 1.497 1.263 0.934 Mn 0.085 0.100 0.089 0.076 0.075 0.087 0.072 0.088 0.018 0.006 0.022 0.037 0.022 0.013 Mg 2.816 3.180 3.095 3.181 2.830 3.063 2.849 3.123 3.476 3.497 3.093 2.565 2.623 2.795 Ca 1.596 1.636 1.643 1.561 1.705 1.603 1.642 1.674 2.071 2.062 1.879 1.804 1.692 1.736 Na 0.491 0.442 0.439 0.482 0.527 0.416 0.414 0.364 0.646 0.572 0.712 0.888 0.935 0.743 K 0.144 0.087 0.112 0.142 0.135 0.125 0.126 0.112 0.260 0.283 0.211 0.194 0.187 0.206 Total 15.23 15.17 15.19 15.17 15.37 15.13 15.18 15.15 15.89 15.85 15.91 15.89 15.79 15.68 Mg* 0.75 0.80 0.81 0.82 0.69 0.77 0.74 0.77 0.86 0.88 0.70 0.63 0.67 0.75 Note: Mg* = Mg/(Mg + Fe2+), MH—magnesiohastingsite; other symbols are same as in Table 2.

96 Geological Society of America Bulletin, January/February 2014 Petrogenesis of intermediate-acid intrusive rocks and zircon SHRIMP U-Pb dating in the Tongling area, Anhui Province (eastern China)

Several of the intrusive rocks of the high-K, calc-alkaline series contain zircon grains with old inherited cores, e.g., 2025 ± 9–2598 ± 13 Ma zircon in the Tongguanshan quartz monzodiorite (Wang et al., 2004b); 2515 ± 13 Ma zircon in the Fenghuangshan granodiorite (Zhang et al., 2006); and 2104 ± 13 Ma and 2330 ± 12 Ma zircon in the Yaoshan granodiorite (this paper). Another group of inherited zircon cores in the Fenghuangshan granodiorite have ages ranging from 531 to 764 Ma (this paper; Zhang et al., 2006). These old grains indicate contributions to the magmas from Precambrian crust either during emplacement of the magmas or during partial melting of source materials from which the magmas were derived. About 80% of the inherited zircon cores have good oscillatory zoning and Th/U ratios >0.3, indicating that the original source rocks were probably igneous in origin. It is not clear where the old zircons resided at the time the Tongling magmas were generated, although they were probably derived from Precambrian continental crust in the Yangtze block. These old zircon grains suggest either a direct or indirect contribution of crustal material to the calc-alkaline rocks of the Tongling area. In contrast, no inherited zircon cores have been found in the rocks of the shoshonitic series, indicating either a different magma source or that any inherited zircons grains were dissolved in the more alkaline shoshonitic magmas because of higher magmatic temperatures and the chemistry of the magma (Watson, 1982). In the rocks of the high-K, calc-alkaline series, initial 87Sr/86Sr = 0.70678–0.70996, ε Nd(t) = –8.2 to –16.2, and TDM (model age) = 1.44–2.41 Ga (Wang et al., 2003; Gao et al., 2006; Yang et al., 2007) (Table 8). The rocks of the shoshonitic series have initial 87Sr/86Sr ε = 0.70617–0.70756, Nd(t) = –6.5 to –9.8, and

TDM = 1.32–1.64 Ga, similar to the pyroxene- and amphibole-rich enclaves that have 87Sr/86Sr = 0.70642–0.70738, ε (t) = –4.9 to

TABLE 6. MICROPROBE ANALYSES OF BIOTITE IN INTRUSIVE ROCKS AND ENCLAVES OF TONGLING OF AND ENCLAVES OF BIOTITE IN INTRUSIVE ROCKS ANALYSES 6. MICROPROBE TABLE Nd

–9.9, and TDM = 1.39–1.97 Ga (Wang et al., 2003; Du et al., 2004) (Table 8). All of the isotopic compositions lie on, or very close to, the mantle array and trend toward values for the lower crust of the South China block (Fig. 11). These results suggest that the primary magmas for both series were derived from a mantle source enriched in crustal material and/or that the primary magmas mixed with lower-crustal melts. It appears that the calc-

4.73 5.59 2.78 4.920.00 5.30 0.00 4.57 0.00 3.870.4090.739 0.00 3.57 0.311 0.864 0.417 0.00 4.72 0.600 0.353 0.00 1.47 0.834 0.403 0.678 0.00 1.42 0.368 0.751 0.01 0.460 1.49 0.674 0.255 0.00 5.43 1.138 0.430 0.14 0.599 3.39 0.141 0.498 0.00 0.056 5.54 0.816 0.358 0.00 4.17 0.191 0.222 0.00 0.767alkaline 4.23 0.250 0.913 0.00 3.62 0.288 0.726 0.366 0.00magma 3.07 0.797 0.498 0.00 4.06 0.652 0.343 source 5.04 0.851 0.00 0.748 0.304 0.00 0.522 0.540had 0.467 0.00 0.856 a higher 0.00 0.00 propor- 37.13 36.44 39.14 37.03 37.54 37.31 38.12 35.51 37.54 40.25 37.99 42.04 38.18 34.06 37.09 37.01 36.63 36.17 36.43 36.55 36.01 13.4017.74 13.51 17.87 12.12 15.72 13.62 18.26 13.69 16.98 12.76 16.96 13.52 17.78 15.15 20.58 12.77 15.83 13.19 12.41 12.68 15.16 11.45 9.39 13.06 15.66 14.2215.3027.64 18.76 13.76 12.08 33.56 15.90 12.81 14.86 21.39 18.14 13.27 13.31 31.45 17.98 13.91 15.24 25.63 18.59 16.65 14.20 28.97 16.60 16.16 16.98 24.90 13.60 17.07 9.58 20.49 42.77 16.39 22.83 5.23 18.47 28.22 1.94 12.46 6.65 29.22 8.46 31.76 8.70 28.29 11.22 29.38 13.49 24.23 18.51 29.43 11.86 12.08 29.72 21.24 20.54 32.08 17.50 tion of crustal material or contained crustal

Symbols as in Table 2. Table Symbols as in material from a different source that was 3 T

5 somewhat more radiogenic than the source of 2 O 0.13 0.23 0.24 0.30 0.33 0.17 0.36 0.18 0.38 0.43 0.40 0.52 0.51 0.10 0.76 0.50 0.62 0.62 0.37 0.74 0.73 2 2 O 3+ 2+ 3+ 2+ OO 9.09 9.00 8.63 8.78 9.10 9.30 8.89 8.11 9.28 9.57 8.06 9.06 9.44 8.60 9.43 9.30 9.48 7.24 9.73 10.02 8.67 Note: 2 2 2 shoshonitic magmas. SamplesRock TGS1SiO TEBD1 JT4 JC1 QMD HC1 FHS1 STJ3 QM YS1 JG6 MBS6 GD BMS2 GDP CSB1 PMD PCE FHSB4 HCE TEBDB6 HGE FHSB7 MDE MQME MRE FeO MnOMgOCaONa 0.35 13.23 0.53 0.08 11.94 15.50 0.15 0.00 12.64 0.22 0.00 13.79 0.30 0.02 12.53 13.85 0.50 0.03 11.54 0.46 0.00 13.77 0.44 0.00 18.77 18.30 0.45 0.21 21.27 0.00 0.00 14.54 0.25 0.00 14.56 0.13 0.41 13.66 13.57 0.22 0.18 13.51 1.15 0.18 14.83 0.28 0.16 12.96 13.35 0.15 0.00 11.69 0.21 0.17 0.47 0.15 0.55 0.22 0.42 0.00 0.44 0.00 0.00 Al TotalSiTiAl 95.88Fe 95.11Mn 2.872 94.28Mg 0.275 2.867Ca 1.222 95.79 0.331Na 3.030 1.253 97.06 0.162 0.023 2.879 1.106 94.10 1.526 0.288 0.036 2.856 0.007 1.248 96.85 1.400 0.303 0.020 0.010 2.942 0.000 1.228 95.30 1.788 0.271 0.035 0.015 2.905 0.000 1.185 94.92 1.465 0.222 0.036 0.019 2.856 0.002 1.214 96.23 1.564 0.218 0.045 0.033 2.916 0.002 1.346 94.67 1.473 0.276 0.049 0.030 2.958 0.000 1.169 95.60 1.573 0.081 0.027 0.030 2.980 0.000 1.143 97.38 1.268 0.084 0.053 0.029 3.082 0.018 1.122 94.80 1.595 0.082 0.028 0.000 2.882 0.000 0.989 96.50 2.057 0.308 0.057 0.017 2.742 0.000 1.162 96.42 2.020 0.205 0.061 0.008 2.828 0.024 1.250 96.94 2.324 0.318 0.061 0.014 2.882 0.014 1.236 95.82 1.636 0.240 0.074 0.078 2.803 0.015 1.157 96.36 1.712 0.243 0.075 0.018 2.779 0.014 1.197 98.57 1.552 0.209 0.016 0.010 2.761 96.67 0.000 1.259 1.550 0.175 0.112 0.014 2.719 0.014 1.487 1.541 0.227 2.780 0.074 0.031 0.012 1.417 0.293 1.698 0.092 0.036 1.238 0.018 1.465 0.092 0.026 0.000 1.480 0.029 0.055 0.000 1.345 0.107 0.000 0.109 TiO K P Fe Mg 57.06 54.36 63.74 55.24 59.13 56.83 58.12 47.65 60.78 76.30 69.85 80.89 62.32 59.54 60.49 57.13 57.26 58.71 58.20 58.22 50.41 Fe KPTotalFe 0.897 7.999 0.000 0.903 8.000 0.000 0.852 7.999 0.000 0.871 8.000 0.000 0.883 8.0001 0.000 0.935 7.999 0.000 0.865 8.001 0.000 0.838 7.996 0.001 0.919 7.999 0.000 0.987 7.935 0.009 0.811 7.991 0.000 0.847 7.996 0.000 0.909 7.990 0.000 0.821 8.001 0.000 0.917 7.995 0.000 0.909 7.999 0.000 0.925 7.978 0.000 0.710 7.990 0.000 0.941 7.972 0.000 0.951 7.989 0.000 0.853 7.941 0.000

Geological Society of America Bulletin, January/February 2014 97 Wu et al.

TABLE 7. MICROPROBE ANALYSES OF PYROXENE IN INTRUSIVE ROCKS AND ENCLAVES IN TONGLING Samples JG6 CS1 BMS6 BMS2 CSB1 Rocks PMD Mz PCE HCE HGE

SiO2 52.04 52.66 52.96 52.91 52.04 48.29 50.14 49.74 49.5 48.91 49.06 TiO2 0.79 0.59 0.70 0.30 0.79 1.59 0.53 0.86 1.12 0.84 0.76 Al2O3 1.48 1.56 1.39 1.59 1.68 5.83 5.51 5.11 5.30 5.55 5.20 FeOT 6.70 8.34 8.00 10.69 6.70 8.67 8.80 7.41 7.29 7.45 8.25

Fe2O3 1.26 0.12 0.88 0.00 0.28 2.53 0.00 1.89 1.60 2.88 1.12 FeO 5.56 8.23 7.21 10.69 6.45 6.39 8.80 5.71 5.85 4.86 7.24 MnO 0.29 0.85 0.83 0.90 0.29 0.22 0.25 0.22 0.29 0.21 0.29 MgO 13.91 12.94 12.63 12.08 13.91 12.06 11.13 13.23 12.26 12.53 10.78 CaO 22.70 22.25 22.61 19.78 22.01 20.95 21.25 22.26 22.16 23.21 24.06

Na2O 0.67 0.56 0.87 0.68 0.67 0.91 0.27 0.43 0.80 0.42 0.36 K2O 0.00 0.04 0.13 0.00 0.00 0.00 0.00 0.00 0.02 0.00 0.00 P2O5 0.00 0.00 0.00 0.00 0.00 0.00 0.14 0.02 0.00 0.00 0.00 Cr2O3 0.16 0.00 0.00 0.16 0.16 0.06 0.09 0.00 0.01 0.01 0.06 NiO 0.08 0.11 0.00 0.00 0.08 0.00 0.06 0.27 0.02 0.12 0.10 Total 99.02 99.9 100.12 99.09 98.33 98.83 98.17 99.74 98.93 99.54 99.03 Si 1.945 1.966 1.972 1.999 1.935 1.822 1.942 1.873 1.893 1.870 1.880 Ti 0.022 0.017 0.020 0.009 0.022 0.045 0.015 0.024 0.031 0.024 0.022 Al 0.074 0.069 0.061 0.071 0.074 0.259 0.160 0.182 0.144 0.160 0.190 FeT 0.210 0.260 0.249 0.338 0.210 0.274 0.285 0.233 0.255 0.238 0.264 Fe3+ 0.036 0.003 0.025 0.000 0.008 0.072 0.000 0.053 0.045 0.081 0.032 Fe2+ 0.174 0.258 0.224 0.338 0.203 0.202 0.279 0.178 0.184 0.152 0.229 Mn 0.009 0.027 0.026 0.029 0.009 0.007 0.008 0.007 0.009 0.007 0.010 Mg 0.775 0.720 0.702 0.680 0.775 0.678 0.643 0.743 0.728 0.714 0.616 Ca 0.909 0.890 0.902 0.800 0.909 0.847 0.882 0.898 0.875 0.951 0.988 Na 0.049 0.040 0.063 0.050 0.049 0.067 0.021 0.031 0.057 0.031 0.027 K 0.000 0.020 0.006 0.000 0.000 0.000 0.000 0.000 0.001 0.000 0.000 P 0.000 0.000 0.000 0.000 0.000 0.000 0.005 0.001 0.000 0.000 0.000 Cr 0.005 0.000 0.000 0.005 0.005 0.002 0.003 0.000 0.004 0.001 0.002 Ni 0.003 0.003 0.000 0.000 0.003 0.000 0.002 0.008 0.004 0.004 0.003 Total 3.995 4.004 4.001 3.980 4.001 4.001 3.966 4.000 4.001 4.000 4.002 Wo 48 48 49 44 48 47 49 48 47 50 53 En 41 39 38 37 41 38 36 40 39 38 33 Fs 11 14 13 19 11 15 16 12 14 13 14 Note: Symbols as in Table 2. Wo—wollastonite; En—enstatite; Fs—ferrosilite.

Magma Evolution pyroxene- and amphibole-rich enclaves in these crustal source. On the basis of the composition rocks, their chemical compositions, and textural and age of the two suites, we suggest that the The magma evolution is similar in both characteristic, we suggest that the shoshonitic parental magma for the high-K, calc-alkaline the high-K, calc-alkaline and shoshonitic series was produced primarily by differentia- suite was derived from a similar, highly enriched series. With increasing SiO2, there is a gen- tion of an alkali basaltic magma derived from mantle source and that the magma assimilated eral decrease in concentrations of Al2O3, TiO2, a highly enriched mantle source. To model this, more lower-crustal material than the shoshonitic FeOt, MgO, CaO, V, Ni, Co, and Y, compat- we selected the gabbro-diorite of the sho sho- magma. The mica-rich enclaves may be partly ible with the crystallization of clinopyroxene, nitic series as the initial magma composition melted residues of the metamorphic rocks in the amphibole, biotite, calcic plagioclase, and and the minerals of the pyroxene-rich enclaves lower crust, but they could not have contributed minor iron oxides (Table 2; Fig. 7). In contrast, as the crystallizing phases. The equation for signiﬁ cantly to the melt composition because of

K2O increases as fractionation takes place, and Rayleigh fractional crystallization (Neumann their very high Al2O3 and K2O and low SiO2. most of the other elements show considerable et al., 1954) is used: scatter, probably refl ecting mixing of mafi c and Modeling of Magma Mixing C = C F(D – 1), intermediate magmas and contamination by L 0 Although the geochemical trends in the calc- crustal rocks. Such processes could also possi- in which CL is the concentration of an element in alkaline series are compatible with some crystal bly explain the wide scatter in Zr and the rela- the residual liquid, C0 is the concentration of an fractionation, the microdiorite enclaves in these tively high Cr contents of these rocks. The Cr element in the initial liquid, F is the fraction of rocks provide good evidence for injection of contents may also refl ect minor Cr mineraliza- melt left, and D is the bulk distribution co effi ci- mafi c melts into granitic magma (Didier and tion. Taken together, the geochemical features ent for the minerals settling out of the melt. The Barbarin, 1991), suggesting that magma mixing of these rocks suggest that they owe their com- results are presented in Table 9. From the calcu- played an important role in the evolution of this positions to a combination of magma mixing lation, we see that a gabbro-diorite melt could series. The many microdiorite enclaves in the and assimilation–fraction crystallization (AFC) have evolved into the shoshonitic magma by granodiorites are interpreted as blobs of incom- processes. 53%–78% fractional crystallization. pletely assimilated mafi c magma, suggesting The most mafi c rock in the high-K, calc- that the granodiorite was produced by a combi- Parental Magmas alkaline series is a gabbro-diorite with 53 wt% nation of crustal partial melting and mixing of

The most maﬁ c rock in the shoshonitic series SiO2 and 3.4 wt% MgO. The major oxides for crustal and mantle melts. We selected the pyrox- has 51 wt% SiO2 and 3.3 wt% MgO, indicat- this series also show relatively linear trends on ene monzodiorite as the maﬁ c end member, the ing a rather evolved melt. Initial 87Sr/86Sr the Harker diagrams over a range of ~11 wt% granodiorite as the silicic end member, and the 87 86 ratios range between 0.7064 and 0.7070, with SiO2. These rocks have higher Sr/ Sr(t) (up to quartz monzodiorite as the resulting product to ε ε Nd(t) = –4.9 to –9.9. On the basis of abundant 0.7010) and Nd(t) as low as –16.2, suggesting a test the effects of magma mixing. We tested this

98 Geological Society of America Bulletin, January/February 2014 Petrogenesis of intermediate-acid intrusive rocks and zircon SHRIMP U-Pb dating in the Tongling area, Anhui Province (eastern China)

TABLE 8. Nd AND Sr ISOTOPE DATA FOR ROCKS OF THE TONGLING AREA of continental crust. Experimental studies and 143 144 ε 87 86 Series Sample ( Nd/ Nd)i Nd(t) ( Sr/ Sr)i calculations show that crystallization and cool- SHO Cpx enclave0.512001 –8.9 0.70689 ing of 1 g of basalt from 1200 °C to 775 °C SHO Cpx enclave0.512203 –4.9 0.70642 SHO Hb enclave0.511948 –9.9 0.70678 would provide enough heat to generate 3.5 g SHO Hb enclave 0.512033 –8.2 0.70685 of granitic magma at 775 °C with 80% melt SHO Hb-enclave 0.511957 –9.7 0.70728 SHO CS 0.512057 –7.8 0.70663 (Wiebe et al., 2004). Thus, we propose that SHO CS 0.512073 –7.5 0.70646 reactivation of the Tongling-Deijiahui struc- SHO BMS 0.512102 –6.9 0.70756 tural zone by subduction of the paleo–Pacifi c SHO BMS 0.512124 –6.5 0.70617 SHO BMS 0.511952 –9.8 0.70703 plate beneath eastern China caused partial SHO BMS 0.51203 –8.3 0.70689 melting in the upper mantle to produce an H-K CA SZS 0.511842 –12 0.70811 alkali basalt magma from an enriched mantle H-K CA SZS 0.511928 –10.3 0.70824 H-K CA SZS 0.511837 –12.1 0.70797 source. The mantle-derived alkali basalt H-K CA SZS 0.511948 –9.9 0.70741 magma accumulated at a depth of perhaps H-K CA SZS 0.51199 –9.1 0.70792 H-K CA SZS 0.511977 –9.3 0.70791 40–50 km (Lei et al., 2010; Wu et al., 2012), H-K CA SZS 0.511982 –9.2 0.70792 forming a large magma chamber in which H-K CA SZS 0.511969 –9.5 0.70791 pyroxene crystallized fi rst, followed by amphi- H-K CA SZS 0.511928 –10.3 0.70824 H-K CA SZS 0.511837 –12.1 0.70797 bole as the magma evolved. This magma then H-K CA SZS 0.511948 –9.9 0.70741 underplated and intruded the continental crust, H-K CA SZS 0.51192 –10.4 0.70771 where the original heat from the magma and H-K CA SZS 0.51203 –8.3 0.70689 H-K CA SZS 0.511948 –9.9 0.70678 the latent heat of crystallization caused partial H-K CA SZS 0.512033 –8.2 0.70685 melting of the lower-middle crust, forming a H-K CA SZS 0.511957 –9.7 0.70728 H-K CA SZS 0.511847 –11.9 0.70718 shallower granodioritic magma chamber in H-K CA SZS 0.511623 –16.2 0.70996 which both assimilation and fractional crystal- H-K CA SZS 0.511952 –9.8 0.70703 lization took place, creating a range of inter- H-K CA SZS 0.511861 –11.6 0.70739 H-K CA SZS 0.511851 –11.8 0.70754 mediate magmas that produced the high-K, H-K CA TGS 0.511847 –11.9 0.70718 calc-alkaline rocks. The granodiorite magma H-K CA TGS 0.511851 –11.8 0.70755 intruded the upper crust at ca. 146 Ma, forming H-K CA TGS 0.511847 –11.9 0.70721 H-K CA JGS 0.511752 –13.7 0.70733 the porphyritic granodiorite. The shoshonitic H-K CA JGS 0.511751 –13.7 0.70731 pyroxene monzodiorite magma, with its pyrox- H-K CA JGS 0.511752 –13.7 0.70729 H-K CA JGS 0.511737 –14 0.70732 ene-rich enclaves, was then emplaced into the H-K CA JGS 0.511787 –13 0.70731 upper crust at ca. 143 Ma, where it underwent H-K CA JGS 0.511778 –13.2 0.70731 extensive fractional crystallization and perhaps Note: Data sources: Wang et al. (2003); Yang et al. (2007); Tang et al. (1998); and Du et al. (2004). mixed with the granodiorite magma to form SHO—shoshonitic; H-K CA—high-K, calc-alkaline; Cpx—clinopyroxene; Hb—hornblende; CS—Caoshan pluton; BMS—Baimanshan pluton; SZS—Shizishan pluton; TGS—Tongguangshan pluton; JGS—Jiguangshan pluton. the quartz monzodiorite magma, which was emplaced at around 140 Ma. Thus, shoshonitic intrusions were formed by differentiation of interpretation with a simple mass balance calcu- Petrogenetic Model magma weakly contaminated by crustal mate- lation (Ugidos and Recio, 1993): The mineralogy of the shoshonitic rocks, rial, whereas the high-K, calc-alkaline bodies particularly the pyroxene-rich enclaves, sug- were formed by mixing of pyroxene monzo- ax + b(1 – x) = c, gests relatively high magma temperatures, dio ritic magma (~60%) and granodioritic in which a, b, and c are the elemental contents certainly high enough to cause partial melting magma (~40%) (Fig. 12). of the pyroxene monzodiorite, granodiorite, and quartz monzodiorite, respectively. The mixing fraction of the mafi c magma is given by x. The results indicate that the quartz monzodiorite could have been produced by mixing of ~60% mafi c magma of mantle origin with 40% of a crustal melt (Table 10). We tested this result isotopically using the equations of DePaolo et al. (1991) and Huang et al. (2001), and the crust-mantle isotopic data for the Tongling area from Chen and Jahn (1998) and Jahn et al. (1999). These calculations suggest that rocks of the high-K, calc-alkaline have 18%–50% mantle material, whereas those from the shoshonitic series have 42%–57%. The pyroxene- and amphibole-rich enclaves of the shoshonitic series have 42%–63% mantle material. Thus, the model is in good agreement with 87 86 the isotopic compositions of the three rock types Figure 11. Plot of εNd(t) vs. Sr/ Sr for the intrusive rocks of (Xing and Xu, 1996). Tongling. Symbols are the same as those in Figure 4.

Geological Society of America Bulletin, January/February 2014 99 Wu et al.

The active Tengchong volcanic fi eld in southern China (Zhou et al., 2012) may provide a TABLE 9. MODELING CALCULATIONS FOR ROCKS OF THE SHOSHONITIC SERIES modern analogue for the Tongling magmatism. Minerals Sp Bi Hb Cpx Mineral content (wt %) 0.01 0.02 0.05 0.92 In Tengchong, melting of an enriched upper Elements Ce Nd Sm Eu Yb Lu mantle along a fault produced potassium-rich, Partition coeffi cients 0.08 0.13 0.19 0.20 0.17 0.14 alkali basalt magmas that underplated and Initial concentration* (ppm) 55.7 25.2 5.25 1.44 1.86 0.3 F = 50 105.78 46.12 9.19 2.51 3.30 0.54 intruded the overlying continental crust. Crustal F = 80 68.48 30.61 6.29 1.72 2.24 0.36 assimilation and fractional crystallization of F = 53 100.23 43.84 8.76 2.40 3.14 0.52 trachybasaltic magmas produced a range of inter- F = 78 70.10 31.30 6.42 1.76 2.28 0.37 Actual measured range† 101–72.46 44–40 8.8–7 2.3–1.76 2.4–1.8 0.35–0.25 mediate rocks, including trachybasaltic ande- Note: Mineral partition coeffi cients for biotite (Bi), hornblende (Hb), and clinopyroxene (Cpx) are from Arth sites and trachy andesites containing xenoliths of (1976), and those for spinel (Sp) are from Irving (1974). crustal material. Partial melting of the crust then *The initial concentration from the measured content of the Samuling gabbro-diorite. †Actual range of element concentration from the measured result of the Baimaishan pyroxene monzodiorite. produced a felsic magma, which mixed with the trachybasalt to form a potassium-rich, calc-alkaline dacite, which was also erupted. Geophysical and heat fl ow studies at Tengchong indicate the presence of crustal magma chambers at depths TABLE 10. A SIMPLE MIXING MODEL FOR MAFIC AND SILICIC MAGMAS Mixing magma Mafi c magma Silicic magma of 6–10 km, which will eventually cool to form Magma members (SJC1) (JG6) (STJ5) Modeled values shallow plutons like those in Tongling. CaO (wt%) 5.66 9.63 3.94 6.89 Although the magmatism in the Tongling MgO (wt%) 2.49 3.26 1.23 2.45 area is linked to the stress fi eld produced by TiO2 (wt%) 0.89 1.21 0.48 0.92 Cr (ppm) 46.6 24.5 104.1 56.3 oblique subduction of the paleo–Pacifi c plate, it Ni (ppm) 13.2 14.4 12.0 13.4 is not the direct result of suprasubduction-zone Sc (ppm) 10.35 10.99 4.58 8.43 Y (ppm) 21.0 24.9 11.8 19.7 magmatic processes. The Tongling area lies Fraction of mixing 0.60 nearly 500 km NW of the paleo-Pacifi c subduction zone, i.e., too far inland to have been formed above the subduction zone itself. The enriched upper mantle beneath Tongling must

Figure 12. Model for the intermediate-silicic intrusive magmatism in the Tongling area.

100 Geological Society of America Bulletin, January/February 2014 Petrogenesis of intermediate-acid intrusive rocks and zircon SHRIMP U-Pb dating in the Tongling area, Anhui Province (eastern China) have resulted from a much older subduction magmas in the shallow chamber to form mixed Colombini, L.L., Miller, C.F., Gualda, G.A.R., Wooden, J.L., and Miller, J.S., 2011, Sphene and zircon in the event, perhaps related to collision of the Cathay- melts with microdiorite enclaves. Finally, the Highland Range volcanic sequence (Miocene, southern sian and Yangtze blocks in the Neoproterozoic. mixed magma was intruded to form the quartz Nevada, USA): Elemental partitioning, phase relations, monzodiorite bodies. and infl uence on evolution of silicic magma: Miner- alogy and Petrology, v. 102, p. 29–50, doi:10.1007 / CONCLUSIONS (5) Copper, sulfur, iron, and gold mineraliza- s00710 -011 -0177-3. tion in the Tongling district is mostly located Deer, W.A., Howie, R.A., and Zussman, J., 1992, An Intro- (1) Zircon SHRIMP U-Pb ages for the in skarns associated with the intrusive bodies. duction to the Rock-Forming Minerals (2nd ed.): UK, Longman House, 696 p. Tongling intrusive rocks range from 146 ± 1 Ma These skarns are hosted in late Paleozoic–early DePaolo, D.J., Linn, A.M., and Schubert, G., 1991, The con- for the Yaoshan granodiorite porphyry to 143 ± Mesozoic carbonates, and the mineralization tinental crustal age distribution: Methods of determin- ing mantle separation age from Sm-Nd isotope data 1 Ma for the Huchengjian gabbro-diorite, 142 ± probably refl ects synorogenic remobilization and application to southwestern United States: Journal 2 Ma for the Shujiadian pyroxene monzodiorite, of stratiform sulfi de deposits by the intrud- of Geophysical Research, v. 96, p. 2071–2088, doi: and 142 ± 1 Ma for the Fenghuangshan grano- ing magmas. 10.1029 /90JB02219. Di, Y.J., Zhao, H.L., Zhang, Y.Q., Zhao, J.H., and Yang, L., diorite. These ages, combined with previously (6) The Tongling intrusive rocks provide an 2003, Petrographic evidences for magma mixing in the reported dates from the area, indicate that the excellent example of magmatic activity trig- granitoids from the Tongling area, Anhui Province: sequence of magmatic activity, from oldest to gered by subduction of oceanic lithosphere but Beijing Geology, v. 15, p. 12–17. Di, Y.J., Wu, G.G., Zhang, D., Song, B., Zang, W.S., Zhang, youngest, was granodiorite porphyry, granodio- not directly related to the suprasubduction-zone Z.Y., and Li, J.W., 2005, Zircon SHRIMP U-Pb geo- rite, pyroxene monzodiorite/gabbro-diorite, and processes. Activation of the Tan-Lu fault by this chronology of Xiaotongguanshan and Shatanjiao intrusive rocks from Tongling and their petrological quartz monzodiorite. process was nearly coeval with the Tongling signifi cance: Acta Geologica Sinica, v. 79, p. 796–804. (2) The intrusive rocks form an early high- magmatism. Reactivation of old basement faults Didier, J., and Barbarin, B., 1991, Enclaves and Granite K, calc-alkaline series and a later shoshonitic and fracture zones by such subduction may trig- Petrol ogy: Amsterdam, Elsevier, 625 p. Du, Y.S., Qin, X.L., and Lee, H.K., 2004, Mesozoic mantle- series. The relatively voluminous rocks of the ger mantle melting hundreds of kilometers from derived magma underplating in Tongling, Anhui Prov- calc-alkaline series include gabbro-diorite, an active subduction zone. ince: Evidence from megacrysts and xenoliths: Acta quartz monzodiorite, and granodiorite with Petrologica et Mineralogica, v. 23, p. 109–116 (in Chi- ACKNOWLEDGMENTS nese with English abstract). mica-rich enclaves, mafi c quartz monzodiorite Du, Y.S., Li, S.T., Cao, Y., Qin, X.L., and Lou, Y., 2007, enclaves, and microdiorite enclaves. The rocks This work was supported by the Chinese gov- UAFC-related origin of the Late Jurassic to Early of the shoshonitic series consist of pyroxene ernment’s Executive Program for Exploring the Cretaceous intrusions in the Tongguanshan ore fi eld, Deep Interior beneath the Chinese Continent (Sino- Tongling, Anhui Province: East China: Geoscience, monzodiorite, monzonite, and quartz monzonite v. 21, p. 71–77. Probe-05-05); Chinese Natural Science Founda- with pyroxene-rich, amphibole-rich, and amphi- Frost, B.R., and Frost, C.D., 2008, A geochemical classifi cation of China (grant numbers 40921001, 49772106, tion for feldspathic igneous rocks: Journal of Petrol- bole gabbro enclaves. 40472034, and 40672049); the Special Science Proj- ogy, v. 49, p. 1955–1969. (3) The mineral chemistry, zircon SHRIMP ect from the Ministry of Finance, China (grant num- Frost, B.R., Barnes, C.G., Collins, W.J., Arculus, R.J., Ellis , dates, and isotopic compositions of the enclaves ber 140102); and China Geological Survey Projects D.J., and Frost, C.D., 2001, A geochemical classifi - (grant numbers 1212010918007, 1212010818090, cation for granitic rocks: Journal of Petrology, v. 42, and host rocks show that the parental magma 1212010611803, and 1212010711816). p. 2033–2048, doi: 10.1093 /petrology /42.11 .2033. was most likely an alkali basalt melt derived Gao, G., Xu, Z.W., Yang, X.N., Wang, Y.J., Zhang, J., REFERENCES CITED Jiang , S.Y., and Ling, H.F., 2006, Petrogenesis of the from an enriched mantle source. 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