Petrogenesis of the Xihuashan Granite in Southern Jiangxi Province,South China:Constraints from Zircon U-Pb Geochronology,Geochemistry and Nd Isotopes

Mesozoic granitic intrusions are widely distributed in the Nanling region, South China. Yanshanian granites are closely connected with the formation of tungsten deposits. The Xihuashan granite is a typical representative of tungsten-bearing granite. The Xihuashan granite consists mainly of medium-grained porphyritic biotite granite, medium-grained biotite granite and fine-grained twomica granite, which correspond to LA-ICP-MS zircon U-Pb ages of 555.5±0.4 Ma, 553.0±0.6 Ma and 552.8±0.9 Ma, respectively. Rocks from the Xihuashan mining area displays high SlOe （73.85% to 76.49%） and NaeO＋K20 contents （8.09% to 9.43%）, belonging to high-K calc-alkaline series. They are metaluminous to weakly peraluminous with A/CNK values ranging from 0.96 to 5.06. All granites in this study area are rich in Rb, Th, U and Pb, and depleted in Ba, Sr, P, Ti, Nb and Eu, especially depleted in medium-grained biotite granite and fine-grained two-mica granite. The medium-grained porphyritic biotite granites usually have high LREE concentrations, whereas medium-grained biotite granite and fine-grained two-mica granite displays high HREE contents. Our geochemical data reveal that the studied rocks are highly fractionated I-type granite. The magma underwent strong magma differentiation with decreasing temperature and increasing oxygen fugacity, which may explain the formation of three types of distinct granites. Variations of Rb, Sr and Ba concentrations in different type granites were controlled by fractional crystallization of biotite and feldspar. Fractional crystallization of monazite, allanite and apatite resulted in LREE changes in granite, and formation of garnet mainly caused HREE changes. Granites from the Xihuashan mining area have relatively high εd（t） values （-9.77 to -55.46）, indicating that they were probably generated by partial melting of underlying Proterozoic metasedimentary rocks with minor addition of juvenile crust or mantlederived magmas.

Genesis of the Weiquan Ag-Polymetallic Deposit in East Tianshan, China： Evidence from Zircon U-Pb Geochronology and C-H-O-S-Pb Isotope Systematics

The Weiquan Ag-polymetallic deposit is located on the southern margin of the Central Asian Orogenic Belt and in the western segment of the Aqishan-Yamansu arc belt in East Tianshan,northwestern China. Its orebodies, controlled by faults, occur in the lower Carboniferous volcanosedimentary rocks of the Yamansu Formation as irregular veins and lenses. Four stages of mineralization have been recognized on the basis of mineral assemblages, ore fabrics, and crosscutting relationships among the ore veins. Stage I is the skarn stage(garnet + pyroxene), Stage Ⅱ is the retrograde alteration stage(epidote + chlorite + magnetite ± hematite 士 actinolite ± quartz),Stage Ⅲ is the sulfide stage(Ag and Bi minerals + pyrite + chalcopyrite + galena + sphalerite + quartz ± calcite ± tetrahedrite),and Stage IV is the carbonate stage(quartz + calcite ± pyrite). Skarnization,silicification, carbonatization,epidotization,chloritization, sericitization, and actinolitization are the principal types of hydrothermal alteration. LAICP-MS U-Pb dating yielded ages of 326.5±4.5 and 298.5±1.5 Ma for zircons from the tuff and diorite porphyry, respectively. Given that the tuff is wall rock and that the orebodies are cut by a late diorite porphyry dike, the ages of the tuff and the diorite porphyry provide lower and upper time limits on the age of ore formation. The δ13C values of the calcite samples range from-2.5‰ to 2.3‰, the δ18OH2 Oand δDVSMOWvalues of the sulfide stage(Stage Ⅲ) vary from 1.1‰ to 5.2‰ and-111.7‰ to-66.1‰, respectively,and the δ13C, δ18OH2 Oand δDV-SMOWvalues of calcite in one Stage IV sample are 1.5‰,-0.3‰, and-115.6‰, respectively. Carbon, hydrogen, and oxygen isotopic compositions indicate that the ore-forming fluids evolved gradually from magmatic to meteoric sources. The δ34SV-CDTvalues of the sulfides have a large range from-6.9‰ to 1.4‰, with an average of-2.2‰, indicating a magmatic source, possibly with sedimentary contributions. The206Pb/204Pb,207Pb/204Pb, and208Pb/204Pb ratios of the sulfides are 17.9848-18.2785,15.5188-15.6536, and 37.8125-38.4650, respectively, and one whole-rock sample at Weiquan yields206Pb/204Pb,207Pb/204Pb, and208Pb/204Pb ratios of 18.2060, 15.5674, and 38.0511,respectively. Lead isotopic systems suggest that the ore-forming materials of the Weiquan deposit were derived from a mixed source involving mantle and crustal components. Based on geological features, zircon U-Pb dating, and C-H-OS-Pb isotopic data, it can be concluded that the Weiquan polymetallic deposit is a skarn type that formed in a tectonic setting spanning a period from subduction to post-collision. The ore materials were sourced from magmatic ore-forming fluids that mixed with components derived from host rocks during their ascent, and a gradual mixing with meteoric water took place in the later stages.

Petrogenesis of Kejie Granite in the Northern Changning-Menglian Zone, Western Yunnan: Constraints from Zircon U-Pb Geochronology, Geochemistry and Hf Isotope

The Kejie pluton is located in the north of the Changning-Menglian suture zone. The rock types are mainly biotite-granite. Zircon LA-ICP-MS U-Pb dating indicates that the Kejie pluton emplaced at about 80-77 Ma, Late Cretaceous. The Kejie pluton samples are characterized by high SiO2 （71.68%-72.47%）, K2O （4.73%-5.54%）, total alkali （K2O ＋ Na2O = 8.21%-8.53%）, K2O/Na2O ratios （1.36-1.94） and low P2O5 （0.13%-0.17%）, with A/CNK of 1.025-1.055; enriched in U, Th, and K, depleted in Ba, Nb, St, Ti, P and Eu. They are highly fractionated, slightly peraluminous 1-type granite. The two samples of the Kejie pluton give a large variation of εHf（t） values （-5.04 to 1.96） and Hf isotope crustal model ages of 1.16-1.5 Ga. Zircon Hf isotopes and zircon saturation temperatures of whole-rock （801℃-823℃） show that the mantle-derived materials maybe have played a vital role in the generation of the Kejie pluton. The Kejie pluton was most likely generated in a setting associated with the eastward subduction of the neo-Tethys ocean, where intrusion of mantle wedge basaltic magmas in the crust caused the anatexis of the latter, forming hybrid melts, which subsequently experienced high-degree fractional crystallization.

Chronology and Genesis of S-type Granites in Hetai District, Guangdong Province: Constraints from LA-ICP-MS Zircon U-Pb Dating and Tourmaline Boron Isotope In-situ Analyses

1 Introduction Hetai district,which is a mountainous area,situated on Guangning and Zhaoqing city,west Guangdong Province.Hetai district is generally located on southwest of South China Caledonian fold belt,east margin of Yunkai post-Caledonian uplift.Multiple type granites are widely distributed in Hetai district,including Caledonian,Indosinian and Yanshanian granites.Based on different

Oligocene subduction-related plutonism in the Nodoushan area,Urumieh-Dokhtar magmatic belt: Petrogenetic constraints from U-Pb zircon geochronology and isotope geochemistry

Geochemical data and Sr-Nd isotopes of the host rocks and magmatic microgranular enclaves(MMEs)collected from the Oligocene Nodoushan Plutonic Complex(NPC) in the central part of the Urumieh-Dokhtar Magmatic Belt(UDMB) were studied in order to better understand the magmatic and geodynamic evolution of the UDMB. New U-Pb zircon ages reveal that the NPC was assembled incrementally over ca. 5 m.y., during two main episodes at 30.52 ± 0.11 Ma and 30.06 ± 0.10 Ma in the early Oligocene(middle Rupelian) for dioritic and granite intrusives, and at 24.994 ± 0.037 Ma and 24.13 ± 0.19 Ma in the late Oligocene(latest Chattian) for granodioritic and diorite porphyry units,respectively. The spherical to ellipsoidal enclaves are composed of diorite to monzodiorite and minor gabbroic diorite(SiO_2 = 47.73-57.36 wt.%; Mg# = 42.15-53.04); the host intrusions are mainly granite,granodiorite and diorite porphyry(SiO_2 = 56.51-72.35 wt.%; Mg# = 26.29-50.86). All the samples used in this study have similar geochemical features, including enrichment in large ion lithophile elements(LILEs, e.g. Rb, Ba, Sr) and light rare earth elements(LREEs) relative to high field strength elements(HFSEs) and heavy rare earth elements(HREEs). These features, combined with a relative depletion in Nb,Ta, Ti and P, are characteristic of subduction-related magmas. Isotopic data for the host rocks display ISr = 0.705045-0.707959, εNd(t) =-3.23 to +3.80, and the Nd model ages(TDM) vary from 0.58 Ga to 1.37 Ga. Compared with the host rocks, the MMEs are relatively homogeneous in isotopic composition,with Isr ranging from 0.705513 to 0.707275 and εNd(t) from -1.46 to 4.62. The MMEs have TDM ranging from 0.49 Ga to 1.39 Ga. Geochemical and isotopic similarities between the MMEs and their host rocks demonstrate that the enclaves have mixed origins and were most probably formed by interactions between the lower crust-and mantle-derived magmas. Geochemical data, in combination with geodynamic evidence, suggest that a basic magma was derived from an enriched subcontinental lithospheric mantle(SCLM), presumably triggered by the influx of the hot asthenosphere. This magma then interacted with a crustal melt that originated from the dehydration melting of the mafic lower crust at deep crustal levels. Modeling based on Sr-Nd isotope data indicate that ～50% to 90% of the lower crust-derived melt and ～10% to 50% of the mantle-derived mafic magma were involved in the genesis of the early Oligocene magmas. In contrast,～45%-65% of the mantle-derived mafic magma were incorporated into the lower crust-derived magma(～35%-55%) that generated the late Oligocene hybrid granitoid rocks. Early Oligocene granitoid rocks contain a higher proportion of crustal material compared to those that formed in the late Oligocene. It is reasonable to assume that lower crust and mantle interaction processes played a significant role in the genesis of these hybridgranitoid bodies, where melts undergoing fractional crystallization along with minor amounts of crustal assimilation could ascend to shallower crustal levels and generate a variety of rock types ranging from diorite to granite.

First Report of Zircon U-Pb Chronology and Hf Isotope Evidence of the Heluositan Group Granulite in West Kunlun, Xinjiang

Objective As the uplift belt on the southem margin of the Tarim block, the Tiekelike block consists mainly of a set of Precambrian metamorphic rocks with granulite and gneisses. The Heluositan group-complex is the most ancient rock series in the area, and is a key area for studying the formation and evolution of the Precambrian basement of the Tarim craton. LA-ICP-MS zircon U-Pb dating and Hf isotopic analysis of granulite in this area provide new evidence for revealing the formation and evolution of the Precambrian basement in the Tarim Basin.

Zircon U-Pb Chronology and Whole-rock Sr-Nd Isotope Compositions of Granite Porphyry in the Kaladaban Area of the Northern Altyn

Objective The Altyn Tagh marks the northern margin of the Qinghai-Tibet Plateau and lies between the Tarim block to the north and the Qaidam block,Qilian Orogen,and Kunlun orogenic belt to the south.The Altyn Tagh region contains ophiolite,high-to ultrahigh-pressure metamorphic rocks,and igneous rocks.Previous research has virified the occurrence of continental rifting,subduction,slab roll-back,and collision between the Tarim block and Proto-Tethys oceanic plate.Moreover,Kaladaban volcanic rocks are mainly distributed in the north Altyn region.Studies of the magmatic evolution of this region have proposed that Altyn oceanic plate was subducted during the Ordovician(Han et al.,2012;Wang et al.,2017).However,the specific timing and other aspects of the subduction are debated,and an investigation of granite porphyry in the Kaladaban area would improve our understanding of this subduction event.In this study,we present new U-Pb zircon dating result and Sr-Nd isotope composition data for granite porphyry from the North Altyn region.The objective is to constrain the timing of subduction of the North Altyn oceanic plate and establish the petrogenesis and magma source of the granite porphyry.

Late Mesozoic Ore-forming Events in the Ningwu Ore District, Middle-Lower Yangtze River Polymetallic Ore Belt, East China: Evidence from Zircon U-Pb Geochronology and Hf Isotopic Compositions of the Granodioritic Stocks

Late Mesozoic volcanic-subvolcanic rocks and related iron deposits, known as porphyry iron deposits in China, are widespread in the Ningwu ore district （Cretaceous basin） of the middle-lower Yangtze River polymetallic ore belt, East China. Two types of Late Mesozoic magmatic rocks are exposed： one is dioritic rocks closely related to iron mineralization as the hosted rock, and the other one is granodioritic （-granitic） rocks that cut the ore bodies. To understand the age of the iron mineralization and the ore-forming event, detailed zircon U-Pb dating and Hf isotope measurement were performed on granodioritic stocks in the Washan, Gaocun-Nanshan, Dongshan and Heshangqiao iron deposits in the basin. Four emplacement and crystallization （typically for zircons） ages of granodioritic rocks were measured as 126.1±0.5 Ma, 126.8±0.5 Ma, 127.3±0.5 Ma and 126.3±0.4 Ma, respectively in these four deposits, with the LA-MC-ICP-MS zircon U-Pb method. Based on the above results combined with previous dating, it is inferred that the iron deposits in the Ningwu Cretaceous basin occurred in a very short period of 131-127 Ma. In situ zircon Hf compositions of εHf（t） of the granodiorite are mainly from -3 to -8 and their corresponding 176Hf/177Hf ratio are from 0.28245 to 0.28265, indicating similar characteristics of dioritic rocks in the basin. We infer that granodioritic rocks occurring in the Ningwu ore district have an original relationship with dioritic rocks. These new results provide significant evidence for further study of this ore district so as to understand the ore-forming event in the study area.

Geochronology, Geochemistry, Whole Rock Sr-Nd and Zircon Hf-O Isotopes of the Early Neoproterozoic Volcanic Rocks in Jiangshan, Eastern Part of the Jiangnan Orogen: Constraints on Petrogenesis and Tectonic Implications

This paper presents the results of combined studies of geochronology, geochemistry, whole rock Sr-Nd and zircon Hf-O isotopes carried out upon the rhyodacite and ignimbrite of Shangshu village, Shangyu town and Shanghupeng village of Jiangshan City in Zhejiang Province, along the northwestern side of the Jiangshan–Shaoxing suture. SHRIMP zircon U-Pb dating of samples in the three areas yielded weighted mean 206 Pb/238 U ages of 842.8 ± 6.9 Ma and 850.0 ± 7.3 Ma, 839 ± 9 Ma and 832.2 ± 8.1 Ma, 828.3 ± 8.5 Ma and 836.9 ± 9.9 Ma, respectively. These ages are older than the volcanic rocks of the Shangshu Formation dated at around 780 Ma distributed in Fuyang City, Hangzhou City, Kaihua County, etc. The volcanic rocks generally have high SiO2(54.08–76.80 wt%) and Al2 O3(12.40–21.31 wt%), low Fe2 O3(0.68–8.92 wt%), MgO(0.29–2.49 wt%), CaO(0.12–2.86 wt%), TiO2(0.10–1.59 wt%) and P2 O5(0.01–0.39 wt%), with variable total alkalis(K2 O + Na2 O =5.42–8.29 wt%). There exists a clear negative correlation between SiO2 and P2 O5. The volcanic rocks have A/CNK ratios of 1.03–2.77 and thus are peraluminous. They are characterized by enrichment in LREE, Rb, Ba, Zr, Hf, K, Th, La, U and depletion in Nb, Sr, P, Ti, with distinct LREE and HREE fractionation of(La/Yb)N values of 5.68–11.67, and with a moderate negative Eu anomaly(&Eu=0.58–0.89). Whole-rock geochemical data shows that the Jiangshan volcanic rocks are possibly I-type granitic rocks, even though they have some characteristics of A&S-type granites due to the magma fractional crystallization and water-rock interaction. Zircon δ18 O values are 3.97‰–5.49‰(average 4.50‰), 2.90‰–5.21‰(average 4.32‰) for ignimbrite from Shangshu village section, and Shanghupeng village section, respectively. They are slightly lower than the average δ18 O values of igneous zircons in equilibrium with mantle magmas(5.3 ± 0.6‰(2σ)), the lower δ18 O value also demonstrating the presence of high temperature water-rock interactions. The ignimbrite rocks have positive εNd(t)(4.02, 3.37, 3.91, 4.74, 2.85, 4.39, totals from the three areas) and εNd(t)(in-situ zircon)(4.3–14.6, a weighted mean of 8.4;6.6–12.7, a weighted mean of 9.0;8.1–12.0, a weighted mean of 9.5, respectively, from the three areas). In conjunction with the trace element studies, they indicate that the source region of the Jiangshan volcanic rocks was mainly composed of juvenile lower crustal material, mixed with some mantle-sourced magma. Detailed elemental and isotopic data suggest that the Jiangshan volcanic rocks were formed in a continental arc setting. There is a series of ca. 860–830 Ma volcanic rocks formed in a back-arc extensional setting in the southern margin of the eastern Jiangnan Orogen, along the northwest side of the Jiangshan–Shaoxing suture. The first stage rift-related anorogenic magmatism may have occurred as early as ca. 860 Ma in the eastern Jiangnan Orogen.

Zircon U-Pb Geochronology and Hf Isotopic Constraints on Petrogenesis of Plagiogranite from the Cuomuqu Ophiolite,Bangong Lake Area,North Tibet

Field observation, geochemical signatures and zircon Hf isotope data indicate that Cuomuqu ophiolite in the Bangonghu area was formed in a back-arc basin （BAB） above a supra- subduction zone （SSZ）. Zircon U-Pb dating of the diabase from the Cuomuqu massif yielded an age of 164.3±1.9 Ma, thus indicating that the ophiolite complex was formed in the Middle Jurassic during back-arc extension of the mature Bangonghu-Nujiang Ocean. The zircon εHf（t） and TDMC values of the plagiogranite are similar to the εHf（t） and TDM of the diabase, respectively. The mode of occurrence of plagiogranites and their bulk-rock and Hf isotope characteristics indicate that they were derived from the mantle, associated with the surrounding gabbro and diabase, and were formed by partial melting of altered and hydrated mafic rocks under shear conditions during lateral drifting of the oceanic crust. The zircon U-Pb age of the plagiogranite is 156.4±1.4 Ma, and it is 7.9 Ma younger than the hosting diabase. In this study, zircon chronological and Hf isotopic data were tentatively analyzed to determine the genesis of plagiogranites in the Cuomuqu ophiolite complex.

Petrogenesis and Tectonic Significance of the Xiuwacu Two-Period Magmatism in Geza Arc of Yunnan Province： Constraints from Lithogeochemistry, Zircon U-Pb Geochronology and Hf isotopic Compositions

Objective The Late Cretaceous Xiuwacu ore-bearing porphyry is located in the Geza area of southern Yidun arc, SW China. In this area, the rock mass is mainly composed of three lithofacies： biotite granite porphyry, monzonitic granite and light alkali feldspar granite. As a part of the Yidun arc, the Geza arc has common structure and temporal- spatial evolution with the ~idun arc, which has experienced three stages of oceanic crust subduction, collision orogeny and intracontinent convergence stages. The molybdenite ores in the area are mainly hosted in monzonitic granite-porphyry and structural fracture zone, and the ore bodies are strictly controlled by faults. In recent years, great geological prospecting results have been achieved in Xiuwacu, and the deposit has reached a medium scale. However, there are few researches on the metallogenic porphyry. Based on the previous research, we determined the rock-forming and ore-forming age of the porphyry, and found that there were two stages of magmatism intrusion in Xiuwacu： Indosinian and Yanshanian. We also discussed the geochemical characteristics and source area of the rocks in the area.

Metallogenesis and ore-forming time of the Changtuxili Mn-Ag-Pb-Zn deposit in Inner Mongolia:Evidence from C-O-S isotopes and U-Pb geochronology

This paper reports new geochronological(U-Pb) and isotope(C,O,and S) data to investigate the timing of mineralization and mode of ore genesis for the recently discovered Changtuxili Mn-Ag-Pb-Zn deposit,located on the western slopes of the southern Great Hinggan Range in NE China.The mineralization is hosted by intermediate-acidic lavas and pyroclastic rocks of the Baiyingaolao Formation.Three stages of mineralization are identified:quartz-pyrite(Stage I),galena-sphalerite-tetrahedrite-rhodochrosite(Stage II),and quartz-pyrite(Stage Ⅲ).δ13C and δ18O values for carbonate from the ore vary from-8.51‰ to-4.96‰ and 3.97‰ to 15.90‰,respectively,which are indicative of a low-temperature alteration environment.δ34SV-CDT values of sulfides range from-1.77‰ to 4.16‰ and show a trend of equilibrium fractionation(δ34SPy>δ34SSp>δ34SGn).These features indicate that pyrite,sphalerite,and galena precipitated during the period of mineralization.The alteration mineral assemblage and isotope data indicate that the weakly acidic to weakly alkaline ore-forming fluid was derived largely from meteoric water and the ore-forming elements C and S originated from magma.During the mineralization,a geochemical barrier was formed by changes in the pH of the ore-forming fluid,leading to the precipitation of rhodochrosite.On the basis of the mineralization characteristics,new isotope data,and comparison with adjacent deposits,we propose that the Changtuxili Mn-Ag-Pb-Zn deposit is an intermediate-to lowsulfidation epithermal deposit whose formation was controlled by fractures and variability in the pH of the oreforming fluid.The surrounding volcanic rocks yield zircon U-Pb ages of 160-146 Ma(Late Jurassic),indicating that the mineralization is younger than 146 Ma.

Mafic Dyke Records of Paleoproterozoic Mantle Plume Activity in the Karelian Craton: U-Pb Baddeleyite/Zircon Geochronology and Sr-Nd Isotopic Data

Mafic dykes preserved important information on mantle melting regimes in the early Earth history.Despite the fact that a large volume of geochronological data for mafic dykes was recently received,several important issues

Paleozoic tectonic evolution of the proto-Korean Peninsula along the East Asian continental margin from detrital zircon U-Pb geochronology and Hf isotope geochemistry

Detrital zircon geochronology and Hf isotope analysis can be used for inferring provenance characteristics,and to evaluate the tectonic evolution of sedimentary basins and their link with regional orogenesis.The Paleozoic sequences of the Okcheon Belt consist of the Lower Paleozoic Joseon and the Upper Paleozoic Pyeongan supergroups with Middle Paleozoic hiatus locally on top of the Neoproterozoic bimodal volcanic rocks,reflecting an intracontinental rift setting between the two basements(viz.Gyeonggi and Yeongnam massifs)at southern part of the Korean Peninsula.Our detrital zircon U-Pb ages and Lu-Hf isotope results show that all these Paleozoic strata commonly have Paleoproterozoic and Paleozoic zircon ages with rare Meso-to Neoproterozoic ages.The individual zircon populations display following features,allowing estimation of their sedimentary provenances:(i)The Paleoproterozoic zircons(ca.1.85 Ga and 2.50 Ga)with similar ranges ofεHf(t)values are most common in the basement rocks of the Korean Peninsula,and were sourced from both the Gyeonggi and Yeongnam massifs.(ii)The Meso-to Neoproterozoic zircons,preserved only in the Middle to Late Cambrian clastic sedimentary rocks within the carbonate sequences probably reflect proximal provenance.(iii)The youngest Paleozoic zircons of each formation,almost coincident with their deposition ages,suggest presence of syndepositional magmatism,indicating proximal magmatic sources during their deposition.(iv)The Cambrian-Ordovician zircons,from the Lower Paleozoic sequences,but rare in the successive Upper Paleozoic sequences,suggest a provenance change after the hiatus between the two sedimentary successions.(v)The Permian zircons showing differentεHf(t)values indicate that detrital sources were varied at that time.The integrated results in our study suggest provenance variability linked to diverse tectonic environments,reflecting prolonged subduction-related crustal evolution of the proto-Korean Peninsula during the Paleozoic.

Zircon U-Pb geochronology and Hf isotopic constraints on petrogenesis of Carnian Huanglonggou granodiorites in Wulonggou area of Eastern Kunlun Orogen,NW China

The Wulonggou area located in the Eastern Kunlun Orogen in NW China is characterized by extensive granitoid magmatism,ductile faulting and orogenic gold mineralization.The Huanglonggou granodiorite is cut by an orogenic gold-bearing fault.This study investigated the major and trace-element compositions,zircon U-Pb dates and zircon Hf isotopic compositions of the Huanglonggou granodiorite.One Huanglonggou granodiorite sample yielded a weighted mean U-Pb zircon age of^221 Ma(Carnian).The Carnian granodiorite is metaluminous,with high alkalis contents of 6.37%--8.86%,high Al_2O_3contents of 15.41%--16.19%,high Sr contents of(426--475)×10^(-6),relatively high Sr/Y ratios,high(La/Yb)_Nvalues and low HREE,suggesting an adakite type high-Si O_2granite.The Huanglonggou granodiorite sample has zirconε_(Hf)(t)values ranging from-4.4 to+1.1.These Hf isotopic data suggest that the Carnian granodiorite was likely derived from the partial melting of subducted Paleo-Tethys oceanic slab.It is suggested that the Late Triassic granodiorite was emplaced during the northward subduction of Paleo-Tethys oceanic slab.Orogenic gold mineralization in the Wulonggou area formed after the emplacement of the Late Triassic intrusive rocks.

Late Mesoproterozoic to Early Neoproterozoic Tectonic Evolution of the SW Yangtze Block, South China: Evidence from U-Pb Geochronology and Lu-Hf Isotopes of Detrital Zircons from Sedimentary Rocks

In situ zircon U-Pb geochronological and Lu-Hf isotope studies of detrital zircons from Late Mesoproterozoic to Early Neoproterozoic sedimentary units on the southwestern margin of the Yangtze Block have important implications for the tectonic evolution of the Yangtze Block.The Huili Group contains zircons whose ages are mainly Late Archean to Mesoproterozoic(2650-2450,2100-1800,and 1350-1150 Ma).The Dengxiangying Group has one major age population of 1900-1600 Ma,and two subordinate age populations of 1350-1100 and 2300-2000 Ma.Yanbian Group sedimentary rocks have a zircon age population mainly in the range of 970-850 Ma,contemporaneous with the ages of widespread arc-related magmatism in the western Yangtze Block.Combining these results with previous work,the Huili and Dengxiangying groups were most likely deposited during ca.1160 to 1000 Ma in an intra-continental rift basin setting,while the Yanbian Group accumulated during>920 to 782 Ma in a back-arc basin setting at the southwestern margin of the Yangtze Block.In addition,all these results further suggest a tectonic transition from a continental rift basin to a convergent environment at the southwestern margin of the Yangtze Block at 1000-970 Ma.

SHRIMP Zircon U-Pb Chronology and Geochemistry of the Henglingguan and Beiyu Granitoids in the Zhongtiao Mountains,Shanxi Province

Henglingguan and Beiyu metamorphic granitoids, distributed in the northwest of the Zhongtiaoshan Precambrian complex, comprise trondhjemites and calc-alkaline monzogranites, displaying intrusive contacts with the Archean Zhaizi TTG gneisses. And the Beiyu metamorphic granitoids consist mainly of trondhjemites, distributed at the core of the Hujiayu anticline fold. New SHRIMP zircon U-Pb dating data show that the weighted mean ^207pb/^206pb ages are 2435.9 Ma and 2477 Ma for the Henglingguan metamorphic calc-alkaline monzogranites and Beiyu metamorphic trondhjemites, respectively, and reveal -2600 Ma inherited core in magmatic zircons. Whole-rock geochemical data indicate that all the Henglingguan and Beiyu metamorphic trondhjemites and calc- alkaline monzogranites belong to the metaluminous medium- and high-potassium calc-alkaline series. These rocks are characterized by relatively high total alkali contents (Na2O+K2O, up to 9.08%), depleted Nb, Ta, P and Ti, and right-declined REE patterns with moderate to high LREEs/HREEs fractionation (the mean ratio of (La/Yb)n = 25). The Henglingguan and Beiyu metamorphic trondhjemites display negative Rb, Th and K anomalies in the multi-dement spider diagrams normalized by primitive mantle. Sm-Nd isotopic data reveal that these granitoids have initial εNd(t) =-1.2 to +2.4 and Nd depleted mantle model ages of TMD = 2622 Ma-2939 Ma. All these geochemical features indicate that these granitoids were formed in an continent-marginal arc, and the trondhjemites mainly originated from partial melting of juvenile basaltic materials and, howbeit, the Henglingguan metamorphic calc-alkaline monzogranites derived from recycling of materials in the ancient crust under a continent-marginal arc. The granitic magma underwent contamination and fractional crystallization during their formation.

LA-ICP-MS Zircon U-Pb Geochronology of Quartz Porphyry from the Niutougou Gold Deposit in Songxian County,Henan Province

The Niutougou gold deposit, located in the center of the Xiong＇ershan gold district, western Henan Province, is a large gold deposit with many quartz porphyries found in the area. Based on the field geological investigation of quartz porphyry of Niutougou gold deposit and by using the cathodoluminescence （CL） images analysis and in situ LA-ICP-MS U-Pb isotope dating method of zircons, the inner structure, trace element compositions and U-Pb age of the zircons separated from quartz porphyry were analyzed and determined. Cathodoluminescence （CL） images of zircons show clear magmatic zonations. Trace element analyses of zircons reveal that all zircons show high concentrations of Th, U, and HREE, and the REE patterns of depletion in LREE, with a positive Ce anomaly. Zircon LA-ICP-MS U-Pb dating results show that the quartz porphyry in the Niutougou gold deposit was formed at 159.714-0.99 Ma （about 160 Ma）, belonging to the product of magmatic activity in late Middle Jurassic. Combined with the geological characteristics of the Niutougou gold deposit, the formation age of the quartz porphyry and the analysis of the formation age of the granite body exposed in the Niutougou gold deposit, the study suggests that the metallogenic epoch of the Niutougou gold deposit may be Yanshanian in age.

U-Pb Age and Hf Isotope Study of Detrital Zircons from the Wanzi Supracrustals:Constraints on the Tectonic Setting and Evolution of the Fuping Complex,Trans-North China Orogen

Located in the middle segment of the Trans-North China Orogen, the Fuping Complex is considered as a critical area in understanding the evolution history of the North China Craton （NCC）. The complex is composed of various high-grade and multiply deformed rocks, including gray gneiss, basic granulite, amphibolite, fine-grained gneiss and marble, metamorphosed to upper amphibolite or granulite facies. It can be divided into four rock units： the Fuping TTG gneisses, Longquanguan augen gneisses, Wanzi supracrustals, and Nanying granitic gneisses. U-Pb age and Hf isotope compositions of about 200 detrital zircons from the Wanzi supracrustals of the Fuping Complex have been analyzed. The data on metamorphic zircon rims give ages of 1.82-1.84 Ga, corresponding to the final amalgamation event of the NCC, whereas the data for igneous zircon cores yield two age populations at -2.10 and -2.51 Ga, with some inherited ages scattering between 2.5 and 2.9 Ga. These results suggest that the Wanzi supracrustals were derived from the Fuping TTG gneisses （-2.5 Ga） and the Nanying granitic gneisses （2.0-2.1 Ga） and deposited between 2.10 and 1.84 Ga. All zircons with -2.51 Ga age have positive initial εHf values from ＋1.4 to ＋10.9, suggesting an important crustal growth event at -2.5 Ga through the addition of juvenile materials from the mantle. The Hf isotope data for the detrital zircons further imply that the 2.8 Ga rocks are important components in the lower crust, which is consistent with a suggestion from Nd isotope data for the Eastern Block. The zircons of 2.10 Ga population have initial εHf values of-4.9 to ＋6.1, interpreted as mixing of crustal re-melt with minor juvenile material contribution at 2.1 Ga. These results are distinct from that for the Western Block, supporting that the Fuping Complex was emplaced in a tectonic active environment at the western margin of the Eastern Block.

Zircon U-Pb age,trace element and Hf isotope composition of Sepon Au-Cu deposit, Laos:tectonic and metallogenic implications

The Truong Son Fold Belt,located at the northeastern margin of the Indochina Block,is considered to be tectonically linked to the subduction of the Paleotethys Ocean and subsequent collision.Sepon is one of the most important super large deposits of the Truong Son Fold Belt.Our LA-ICP-MS zircon U-Pb dating results show that granodiorite porphyry samples from the Sepon deposit have ages of 302.1-4-2.9 Ma, which is a crucial phase for magmatic-tectonical activities from the Late Carboniferous to Early Permian and has avital influence on the mineralization of copper and gold.Zircon from granodiorite porphyry yields εHf (t)values of 4.32 to 9.64,and TDM2 has an average age of 914 Ma,suggesting that the source of the granodiorite porphyry in the region were mainly mantle components but underwent mixing and contamination of crust materials.The Ce^4+/Ce^3+ value of zircon in the granodiorite porphyry varys greatly from 2.4 to 1438.29,which shows magma mixing might occur.Considering the characteristics of trace elements in the zircon and the whole rock geochemical characteristics of intrusion rocks as well as the characteristics of regional volcanic-sedimentary association,it is indicated that the tectonic setting may be the continental arc environment.The Sepon Au-Cu deposit is derived from emplacement of calc-alkaline intermediate-acid magma with coming from deep sources in the subduction process of the Paleotethys Ocean,forming porphyry Mo-Cu,skam Cu-Au mineralization and a hydrothermal sedimentary-hosted Au mineralization in the wall rocks.