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

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.

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.

Geochemistry,geochronology,and zircon Hf isotopic compositions of felsite porphyry in Xiangshan uranium orefield and its geological implication

Recently,a new kind of volcanic rock,felsite porphyry,has been revealed by drilling in Xiangshan area,Jiangxi Province,China.To better understand petrogenesis and magmatic evolution sequence of the Xiangshan volcanic-intrusive complex,we studied systematic petrology,geochemistry,LA-ICP-MS zircon U–Pb dating,and Hf isotope results of the felsite porphyry.Results show that the felsite porphyry has similar geochemical characteristics to the porphyroclastic rhyolite,which is the predominant lithology of Xiangshan uranium orefield.Felsite porphyry and porphyroclastic rhyolite have high SiO2,Al2O3,and K2O contents,low Na2O,and MgO contents,and slightly negative Eu anomalies.Moreover,these rocks are relatively depleted in large ion lithophile elements(K,Ba,and Sr)and are enriched in high field strength elements(Th,Zr,and Hf).LA-ICP-MS zircon U–Pb dating of the felsite porphyry yielded a crystallization age of 132.2±0.9 Ma,which is coeval to that of the porphyroclastic rhyolite.These ages signified that Xiangshan volcanic-intrusive complex formed in the Early Cretaceous,during which the entire South China was in the back-arc extension tectonic setting related to the subduction of the Pacific Plate under the Euroasian Plate.In-situ zircon Hf isotope data on a felsite porphyry sample show eHf(t)values from-8.82 to-5.11,while the Hf isotope two-stage model age(TDM2-Hf)ranges from 1513 to 1747 Ma.Combined with petrological,mineralogical,geochemistry,and geochronology results of the felsite porphyry,it is concluded that the felsite porphyry in Xiangshan might be originated from the partial melting of the Mesoproterozoic ancient metamorphic rocks,with possible input of small amounts of mantle materials.

Zircon U-Pb age, Lu-Hf Isotopic Characteristics and Origin of the Banshanping Granitoid Rocks in East Qinling Orogenic Belt

The Banshanping granitoid rocks distribute in the east of the North Qinling orogenic belt.It is a diorite-quartz diorite-granodiorite-granite series,spreading in a NW-SE direction,and intrudes into the Erlangping Group.The SiO2 content ranges from 57.04% to 76.56%,Na2O from 2.05% to 4.65%,K2O from 0.84% to 3.40%.Major element characteristics indicate that Banshanping granitoid rocks have properties of I type granotoids.SREE ranges from 36.51 ppm to 473.25 ppm,and LREE/ HREE ratios lie between 3.95 and 22.18.Negative Eu anomalies are not obvious in most samples,though there are obvious Nb,P and Ti positive anomalies.The zircon LA-ICP-MS ages of Banshangping granitoid rocks are 496.0±8.1 Ma-486.9±9.3 Ma.Hf isotope shows that 176Hf/177Hf ratios range from 0.282721 to 0.282876,εHf（t） values from 8.5 to 14,all positive,and corresponding modal ages （TDM2） range from 559 Ma to 908 Ma.Based on Hf isotope characteristics and existing SmNd and Rb-Sr isotope data,we consider that the Banshanping granitoid rocks originate from mantlederived material,i.e.the igneous rocks that formed in Neoproterozoic,and there may be a certain amount of crust-derived material during the formation of Banshanping granitoid rocks.

Geochronology and Petrogeochemistry of Metallogenic Intrusions in the Shanmen Large-scale Silver Deposit in the Siping Area of Jilin Province, NE China

The Shanmen deposit, located in the Siping area of Jilin Province, is one of large-scale silver deposits in Northeast(NE) China. Due to its high Ag grade, associated gold resources and special tectonic location, this deposit has important theoretical and ore-prospecting significance. To present new data on the ore genesis, mineralization time and tectonic settings, the relationship between silver mineralization and intrusions in this deposit has been studied and some analyses have been carried out, including LA-ICP-MS zircon U-Pb dating, whole-rock major and trace element analysis and Sr-Nd-Pb isotope analysis of the granitoids associated with silver mineralization. Studies on deposit geology indicate that the ore-hosting granodiorite and monzogranite have intimate genetic relationships with silver mineralization. LA-ICP-MS zircon U-Pb dating results of the both intrusions are 167.6 ± 1.9 Ma and 167.0 ± 1.5 Ma, respectively, implying that the two intrusions and associated silver mineralization in the Shanmen deposit formed during the Middle Jurassic. Major element analytical data suggest that the two intrusions are high-K calc–alkaline series I-type granites and belong to metaluminous and peraluminous rocks. Both intrusions have similar REE characteristics with regard to the relative enrichment of LREEs, depletion of HREEs, obvious fractionation of LREEs and HREEs(ΣLREE/ΣHREE = 8.68–14.09,(La/Yb)_N = 12.51–21.96), moderately negative Eu anomalies as well as weakly negative Ce anomalies(δEu = 0.56–0.71, δCe = 0.93–1.09). Moreover, the samples are generally enriched in LILEs and depleted in HFSEs. The rock assemblages and geochemical characteristics of granitoids in the Shanmen deposit suggest that they formed in an active continental margin associated with the Paleo-Pacific plate subduction. The Sr-Nd-Pb isotope compositions show that both the granodiorite and monzogranite have low Sr initial ratios and high Sm/Nd initial ratios. The ε_(Nd)(t) values and young Nd-model ages are-3.2 to-1.7 and 990 Ma to 1110 Ma, respectively. Considering the Sr-Nd isotope compositions, in conjunction with the relatively high ~(206)Pb, ~(207)Pb and ~(208)Pb, alongside the relatively low ~(204)Pb, it can be concluded that the Middle Jurassic intermediate-acidic magma represented by the studied monzogranite and granodiorite in the Shanmen deposit, was derived from the partial melting of juvenile lower crust enriched in mantle-derived materials and affected by the mixing of ancient crustal materials during the ascension and intrusion processes.

Geochemistry and Geochronology of Intermediate Rocks in the Jiangshan Au Deposit in the Bengbu Uplift, North Anhui Province: Clues to Regional Au Mineralization

The Jiangshan gold deposit is the largest,most recently-discovered gold deposit in the Bengbu Uplift.The ore bodies are located in the structural fracture zone of the Zhuangzili Formation(Ar3),with major Pb-Zn and Au reserves.In this study,LA-ICP-MS zircon U-Pb analyses yielded a crystallization age of 111.5±1.8 Ma for the quartz diorite porphyry in Jiangshan.The quartz diorite porphyry has high Ba and Sr content,with low Y and Yb content,which is similar to the characteristics of adakitic rocks.They are enriched in large ion lithophile elements(LILEs,e.g.,Ba,U)and light rare ear th elements(LREEs),while depleted in high field strength elements(HFSEs,e.g.,Nb,Ti)and heavy rare earth element(HREEs).They have zirconεHf(t)values of-23.52 to-21.14(mean=-22.32).and Hf model ages of 2419.76 to 2569.39 Ma.The magma source area is the lower crust.Magma primarily came from the partial melting of the lower crust,with the addition of some mantle material.The quartz diorite porphyries are characterized by high zircon TTi-in-zircon values(608-757°C),Ce^4+/Ce^3+ratios(71.97-1387.10)and Eu/Eu*ratios(0.46-1.08),indicating high temperature and magmatic oxygen fugacities.High temperatures can provide heat to fluids and highly oxidized magmas can control the behavior and speciation of sulfides,thus controlling the behavior of Au.Finally,the ore-forming fluid is enriched and precipitated in a favorable structural space to form the Jiangshan Au deposit.

Origin and Geodynamic Implications of Concealed Granite in Shadong Tungsten Deposit, Xinjiang, China： Zircon U-Pb Chronology, Geochemistry, and Sr-Nd-Hf Isotope Constraint

Shadong deposit is the first large-scale tungsten deposit found in the East Tianshan orogenic belt, and the geologic characteristics of the deposit indicate that the deeply concealed granite body is ge- netically related with the mineralization. The LA-ICPMS U-Pb age of zircons from the Shadong concealed granite obtained in this research is 239±2.0 Ma, belonging to the Middle Triassic. The whole rock samples are metaiuminous to slightly peraluminous （A/CNK=0.95-1.02） with low contents of SiO2 （64.0 wt.%-68.5 wt.%） and low K2O/Na2O ratios （0.73-0.96）. The samples reveal enrichment of K, Rb, Th and depletion of Nb, Ta, P, Ti and have a negative slope from La to Lu （LaN/YbN=16.29-36.8） with weak negative Eu anom- aly （Eu/Eu＊= 0.71-0.82）. Initial ^87Sr/^86Sr ratios of whole rock range of 0.706 59-0.707 75, eNd（t） values range from -1.77 to -2.53 and εnf（t） values of zircon are between 2.54 and 4.90. The lithogeochemistry and Sr-Nd-Hf isotopic characteristics revealed that the concealed granite in Shadong tungsten deposit is I-type granite, and occurs in an intraplate tectonic setting. The magma mixing during intraplating of mantle de- rived magma intruding into the crust in Indosinian Period is the major formation mechanism of the granite. Of which, the proportion of mantle derived magma ranges from 58% to 60%, and the crustal materials are mainly the metamorphic basement of Xingxingxia Group of Mesoproterozoic Changcheng System, which may orovide the main source of ore forming metals of Shadong tungsten deposit.

德兴矿集区花岗闪长斑岩锆石U-Pb年龄、Hf同位素特征及其意义

德兴矿集区位于赣东北地区,是中国东部中生代钦杭成矿带中的大型铜金铅锌矿集区之一,集中了铜厂、富家坞和朱砂红斑岩铜钼(金)矿、银山银铜铅锌多金属矿和金山金矿等大型、超大型矿床。本文在系统的野外地质调查与样品采集的基础上,对铜厂、富家坞、朱砂红及银山花岗闪长斑岩进行了LA-MC-ICP-MS锆石U-Pb定年和原位Hf同位素分析。德兴矿集区花岗闪长斑岩的LA-MC-ICP-MS锆石U-Pb的4组年龄分别为:(171±1.2)Ma(铜厂)、(172±0.68)Ma(富家坞)、(173±1.3)Ma(朱砂红)、(176±1.5)Ma(银山),表明这些岩体均为中侏罗世的产物。样品Hf两阶段模式年龄平均值分别为861 Ma、876 Ma、904 Ma和941 Ma,正的εHf(t)平均值在4.34-5.54,Zr/Hf比值接近于上地幔的Zr/Hf比值。锆石Hf同位素组成显示,岩浆源区主要来源于亏损地幔组分,但在岩浆演化中遭受了古老地壳物质的混染,幔源物质在德兴矿集区花岗闪长斑岩的形成过程中发挥了重要作用。德兴矿集区4个矿床成岩成矿的最重要时期在170-175 Ma,该矿集区岩浆热液系统持续活动可能是该大型矿集区形成的重要原因。

Geochemistry, Sr-Nd-Pb Isotopic Compositions and Zircon U-Pb Geochronology of Neoproterozoic Mafic Dyke in the Douling Complex, South Qinling Belt, China

Mafic dyke swarm is widely developed in Proterozoic continental lithosphere.The Gangou diabase dyke from the Xixia area,intruded into the Douling complex of the South Qinling belt,yields zircon UPb age of 731 Ma.It has low SiO2 content(49.02 wt.%-49.37 wt.%)and Mg^#(34.0–37.7)and shows characteristics of subalkaline tholeiite series.They show highΣREE(155.5×10^-6–184.7×10^-6),weak negative Eu anomaly(δEu=0.88-0.93),slight depletion of Nb and Ta,and enrichment of LILE.Their major and trace element,Sr-Nd-Pb isotope and clinopyroxene compositions indicate that it originated from the partial melting of the asthenospheric mantle within-plate extension setting and was slightly contaminated by crust compositions.The similarities of formation age,petrogenesis,source characteristic and tectonic setting for Gangou diabase with mafic dykes in Wudang Block and mafic volcanic rocks in Yaolinghe Group indicate that the South Qinling belt underwent strong continental extension in Neoproterozoic during 796–685 Ma most likely correspondence to the breaking-up of the Rodinia supercontinent.

The LA-ICP-MS zircons U-Pb ages and geochemistry of the Baihua basic igneous complexes in Tianshui area of West Qinling

Baihua meta-igneous complex consists mainly of pyroxenite-gabbro(diorite)-diorite-quartz diorite. They form a complete comagmatic evolutionary series. The geochemical characteristics of basic-interme- diate basic igneous rocks indicate that they belong to a tholeiite suite. The REE distribution pattern is nearly flat type and LREE is slightly enriched type, and their primitive mantle-normalized and MORB-normalized trace element spider diagrams are generally similar; the LIL elements (LILE) Cs, Ba, Sr, Th and U are enriched, but Rb, K and the HFSEs Nb, P, Zr, Sm, Ti and Y are relatively depleted. All these show comagmatic evolution and origin characteristics. The tectonics environment discrimination of trace element reveals that these igneous complexes formed in an island-arc setting. The LA-ICP-MS single-zircons U-Pb age of Baihua basic igneous complex is 434.6±1.5 Ma (MSWD = 1.3), which proves that the formation time of the island-arc type magmatite in the northern zone of West Qinling is Late Ordovician or Early Silurian, also reveals that the timing of subduction of paleo-ocean basin represented by the Guanzizhen ophiolite and resulting island-arc-type magmatic activities is probably Middle-Late Ordovician to Early Silurian.

Early Permian–Late Triassic Magmatism in the Tuotuohe Region of the Qinghai–Tibet Plateau: Constraints on the Tectonic evolution of the Western Segment of the Jinshajiang Suture

In this paper we present new zircon U-Pb ages,whole-rock major and trace element analyses,and zircon Hf isotopic data for magmatic rocks in the Tuotuohe region of the western segment of the Jinshajiang suture.Our aim is to constrain the Early Permian-Late Triassic tectonic evolution of the region.Zircons from the magmatic rocks of the Tuotuohe region are euhedralsubhedral in shape and display fine-scale oscillatory zoning as well as high Th/U ratios （0.4-4.6）,indicating a magmatic origin.The zircon U-Pb ages obtained using LA-ICP-MS are 281 ± 1 Ma,258 ± 1 Ma,244 ± 1 Ma,and 216 ± 1 Ma,which indicate magmatism in the Early Permian-Late Triassic.A diorite from Bashihubei （BSHN） has SiO2 =57.18-59.97 wt％,Al2O3=15.70-16.53 wt％,and total alkalis （Na2O ＋ K2O） =4.46-6.34 wt％,typical of calc-alkaline and metaluminous series.A gabbro from Bashibadaoban （BSBDB） belongs to the alkaline series,and is poor in SiO2 （45.46-54.03 wt％） but rich in Al2O3 （16.19-17.39 wt％） and total alkalis （Na2O ＋ K2O =5.48-6.26 wt％）.The BSHN diorite and the BSBDB gabbro both display an enrichment of LREEs and LILEs and depletion of HFSEs,and they have no obvious Eu anomaly; they have relatively low MgO contents （2.54-4.93 wt％）,Mg# values of 43 to 52,and low Cr and Ni contents （8.07-33.6 ppm and 4.41-14.2 ppm,respectively）,indicating they differentiated from primitive mantle magmas.They have low Nb/U,Ta/ U,and Ce/Pb ratios （1.3-9.6,0.2-0.8,and 0.1-18.1,respectively）,and their initial Hf isotopic ratios range from ＋9.6 to ＋16.9 （BSHN diorite） and ＋6.5 to ＋12.6 （BSBDB gabbro）,suggesting their primary magmas were derived mainly from the partial melting of a mantle wedge that had been metasomatized by subduction fluids.Taking all the new data together,we conclude that the western and eastern segment of the Jinshajiang suture regions underwent identical processes of evolution in the Early Permian-Late Triassic：oceanic crust subduction before the Early Permian,continental collision during the Early-Middle Triassic,and post-collisional extension from the Late Triassic.

U-Pb Zircon Age,Geochemical and Sr-Nd-Hf Isotopic Compositions of Neoproterozoic Granitoids in Northwestern Margin of Yangtze Block (South China):Implications for Neoproterozoic Tectonic Evolution

ABSTRACT： The widespread Neoproterozoic magmatism along the Yangtze block carries critical in- formation for understanding the Neoproterozoic evolution of the Yangtze block. In the northwestern margin of the Yangtze block, the Hannan （汉南） intrusive complex includes the Wudumen （五堵门）, Erliba （二里坝） and Zushidian （祖师殿） granitoids. Using LA-ICP-MS U-Pb zircon dating method, the Wudumen and Erliba granitoids yielded magma crystallization ages of 785±4 and 778±3 Ma, respectively. Samples from these three granitoids show variable SiO2 contents ranging from 58.8% to 72.6%. They are characterized by enrichment of Al2O3（14.97%-17.87%）, Na2O（3.80%-5.33%） and Sr （504ppm-741 ppm）, and depletion of Y （〈19 ppm） and HREE （e.g., Yb〈1.6 ppm）, resulting in high Sr/Y （29-161） and （La/Yb）N （7.3-27.8） ratios. The geochemical features of the granitoids are comparable with those of adakite. The granitoids have zircon εHdt） values of ＋3.65 to ＋10.05, whole-rock εNd（t） values of -0.09 to ＋2.98 and whole-rock initial ^87Sr/^86Sr ratios of 0.7034-0.7039, indicating that their magma was derived from a juvenile crustal source. Together with geochemical and Hf-Sr-Nd isotopic compositions, it is suggested that the granitoids formed in island-arc setting and originated from partial melting of a subducted oceanic slab. The results support a model that the Yangtze block was surrounded by ocean and arc magmatism in its northern and northwestern margins in Neoproterozoic.

Zircon U–Pb age and geochemical constraints on the origin and tectonic implication of the Tuotuohe Cenozoic alkaline magmatism in Qinghai–Tibet Plateau

A large number of Eocene-Oligocene alkaline/alkali-rich igneous rocks were developed in the Tuotuohe region of the Qinghai-Tibetan Plateau.In this study,we present zircon U-Pb ages,Hf isotope data,and major and trace element compositions of the Cenozoic alkaline rocks from the Tuotuohe region in order to constraint the petrogenesis and tectonic evolution history of Qiangtang Block.Zircon U-Pb ages were measured via LA-ICP-MS to be39.6,37.6 and 32.0 Ma.The 39.6 Ma trachyte was characterized by low SiO2 and high K2O and MgO contents.The 37.6 and 32.0 Ma orthophyres show enrichment in SiO2 and K2O,but deficient in MgO.All of the samples belong to the alkaline rocks.These rocks display enrichment in REE,LREE,and LILE,depletion in HFSE,and no obvious Eu anomalies.Geological and geochemical features suggest that there were two possible mechanisms for the origin of the alkaline rocks in the Tuotuohe region:(1)the removed mafic lower crust dropped into the asthenosphere,forming the mix magma(Nariniya trachyte);(2)the upwelling asthenosphere triggered the crustal melting(Nariniya and Zamaqu orthophyre).The Eocene-Oligocene alkaline rocks in the study and adjacent areas are likely to be the result of the same tectonic-magmatic event of deep lithospheric evolution that is the crustal material melting triggered by lithospheric delamination.This conclusion extends the influence scope of lithospheric delamination eastward to the Tuotuohe region(*92°E)from Banda Co(*82°E).

A new analytical mode and application of the laser ablation inductively coupled plasma mass spectrometer in the earth sciences

We proposed a new laser analytical mode,which used the high-frequency laser ablation to deliberately obtain the peak-shape signal profile,combined with the linear regression calibration(LRC)method to calculate elemental or isotopic ratios.In order to assess the performance of the new laser analytical mode for the application in the field of earth science,we systematically investigated the elemental quantitative analysis with high spatial resolution(10μm),rapid U-Pb dating in zircons and accurate Sr-Hf isotope analysis in geological samples.The new high-frequency laser analysis technology(20 Hz,100 pulses)reduced the limit of detection(LOD)of 25 elements to 0.005-0.16μg g^(-1) with crater diameters of 10μm,which are significantly lower(decrease to 2-20%)than previous researches.The quantitative analysis of five silicate glass reference materials showed that the precision and accuracy of the 25 trace elements(with the concentration ranging from 0.17 to 683μg g^(-1))were better than 16% and 15%,respectively.The new methods raised the analytical throughput of zircon U-Pb dating,Sr isotope ratios and Hf isotope ratios to 250 analyses per hour,144 analyses per hour and 120 analyses per hour in theory,while the analytical accuracy and precision were not affected.The detailed investigations showed that the proposed new laser analytical mode has good application effects in the field of earth sciences.