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Early Cretaceous adakitic Rocks in the Northern Great Xing’an Range, NE China: Implications for the Final Closure of Mongol-Okhotsk Ocean and Regional Extensional Setting

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Acta Geologica Sinica(English Edition) 2019年第5期93卷 1544-1558页

作者： ZHANG Lingyu LI Shichao CHU Xiaolei SHANG Yinmin College of Earth Sciences Jilin UniversityChangchun 130061China Key Laboratory of Mineral Resources Evaluation in Northeast Asia Ministry of Land and ResourcesChangchun130061China

A large amount of igneous rocks in NE China formed in an extensional setting during Late Mesozoic. However, there is still controversy about how the Mongol-Okhotsk Ocean and the Paleo-Pacific Ocean effected the lithosphere in NE China. In this paper, we carried out a comprehensive study for andesites from the Keyihe area using LA-ICP-MS zircon UPb dating and geochemical and Hf isotopic analysis to investigate the petrogenesis and tectonic setting of these andesites. The U-Pb dating yields an Early Cretaceous crystallization age of 128.3±0.4 Ma. Geochemically, the andesites contain high Sr(686-930 ppm) and HREE contents, low Y(11.9-19.8 ppm) and Yb(1.08-1.52 ppm) contents, and they therefore have high Sr/Y(42-63) and La/Yb(24-36) ratios, showing the characteristics of adakitic rocks. Moreover, they exhibit high K2O/Na2O ratios(0.57-0.81), low Mg O contents(0.77-3.06 wt%), low Mg# value(17-49) and negative εHf(t) values(-1.7 to-8.5) with no negative Eu anomalies, indicating that they are not related to the oceanic plate subduction. Based on the geochemical and isotopic data provided in this paper and regional geological data, it can be concluded that the Keyihe adakitic rocks were affected by the Mongol-Okhotsk tectonic regime, forming in a transition setting from crustal thickening to regional extension thinning. They were derived from the partial melting of the thickened lower crust. The closure of the Mongol-Okhotsk Ocean may finish in early Early Cretaceous, followed by the collisional orogenic process. The southern part region of its suture belt was in a post-orogenic extensional setting in the late Early Cretaceous.

关键词： Mongol-Okhotsk Ocean northern Great Xing’an Range Early Cretaceous adakitic rocks lower crust

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Source of the Ore-forming adakitic Porphyry at the Beiya Super-large Au Deposit, Western Yangtze Craton: New Evidence from Zircon U-Pb Ages of the Amphibolite Xenoliths

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Acta Geologica Sinica(English Edition) 2020年第1期94卷 208-209页

作者： LIU Siqi ZHENG Yuanchuan SHEN Yang HOU Zengqian WANG Lu WANG Zixuan State Key Laboratory of Geological Processes and Mineral Resources and School of Earth Science and ResourcesChina University of GeosciencesBeijing 100083China Institute of Geology Chinese Academy of Geological SciencesBeijing 100037China

Objective The Beiya super-large Au-rich porphyry deposit(304 t Au,2.4 g/t Au)is located within the western Yangtze craton,to the southeast of the Sanjiang Tethyan Orogen(Fig.1).The ore-forming porphyry is adakitic,characterized by high Sr/Y and La/Yb ratios coupled with low Y and Yb contents,and is generally thought to be derived from partial melting of thickened mafic lower crust.The lower crust underneath the western Yangtze craton is mainly composed of ancient crust with Archean ages,juvenile crust resulting from the Neoproterozoic subduction(740–1000 Ma),and late Permian juvenile crust related to the Emeishan mantle plume.Which lower crustal end-member has played a critical role in genesis of the Beiya ore-forming porphyry can be constrained by zircon U-Pb ages of amphibolite xenoliths hosted in the ore-forming porphyry,because these xenoliths represent direct samples of the source.In this study,we present new zircon U-Pb ages of these amphibolite xenoliths to have insight into the nature of the Beiya adakitic porphyry source.

关键词： Western Yangtze Craton New Evidence from Zircon U-Pb Ages of the Amphibolite Xenoliths Source of the Ore-forming adakitic Porphyry at the Beiya Super-large Au Deposit

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New insights into petrogenesis of Miocene magmatism associated with porphyry copper deposits of the Andean Pampean flat slab,Argentina

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Geoscience Frontiers 2018年第5期9卷 1565-1576页

作者： Silvia I.Carrasquero Nora A.Rubinstein Anabel L.R.Gómez Massimo Chiaradia Dénis Fontignie Victor A.Valencia Facultad de Ciencias Naturales y Museo Universidad Nacional de La Plata Instituto de Geociencias básicas aplicadas y ambientales de Buenos Aires (IgeBA) Departamento de Ciencias Geológicas Facultad de Ciencias Exactas y NaturalesUniversidad de Buenos-CONICET Department of Earth Sciences University of Geneva School of Earth and Environmental Sciences Faculty Washington State University

The Paramillos de Uspallata mining district located in the backarc region of the Pampean flat-slab segment(28°-33°S) features porphyry-type deposits genetically associated with Middle Miocene volcanics. This mineralizing magmatism comprising hydrothermally altered(sodic-calcic, potassic and phyllic alteration) subvolcanic and pyroclastic rocks of andesite-basaltic andesite and dacite-rhyolite composition with a typical arc signature, represents the eastward broadening of the Farellones arc by ~17 Ma. Its geochemistry also reveals a residual mineralogy of amphibole ± garnet with limited plagioclase fractionation resulting in an adakitic signal; however, according to the isotopic data collected in our study, the contributions of MASH(melting-assimilation-storage-homogenization) processes in the acquisition of this signal cannot be disregarded.Both the broadening of the Farellones arc and its residual mineralogy e typical of relatively deep magmatic chambers e are consistent with a slab shallowing and outcoming crustal thickening setting.This tectonic scenario could be interpreted as a result of an early effect of the Juan Fernandez Ridge collision that was further to the north by ~17 Ma. Our findings suggest that magmas were fertile for porphyry type deposits during the early stages of the slab shallowing.

关键词： Porphyry copper deposits Petrogenesis adakitic signal Backarc Central Andes

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Geochronology and geochemistry of Late Carboniferous dykes in the Aqishan-Yamansu belt,eastern Tianshan:Evidence for a post-collisional slab breakoff

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Geoscience Frontiers 2020年第1期11卷 347-362页

作者： Xiaoping Long Bin Wu Min Sun Chao Yuan Wenjiao Xiao Rui Zuo State Key Laboratory of Continental Dynamics Department of GeologyNorthwest UniversityXi’an710069China Department of Earth Sciences The University of Hong KongPokfulam RoadHong KongChina State Key Laboratory of Isotope Geochemistry Guangzhou Institute of GeochemistryChinese Academy of SciencesGuangzhou510640China State Key Laboratory of Lithospheric Evolution Institute of Geology and GeophysicsChinese Academy of SciencesBeijing100029China

With aim of providing constraints on the Late Paleozoic tectonic evolution of the southern Central Asian Orogenic Belt(CAOB),an integrated study was conducted on the geochronological and geochemical data for dioritic,granitic and diabase dykes from the Aqishan-Yamansu belt in the eastern Tianshan,NW China.Zircon U-Pb dating indicates that the dioritic and granitic dykes were both emplaced in the Late Carboniferous(~311 Ma and^315 Ma).The dioritic dykes show adakitic characteristics and have high Na2 O and positiveεHf(t)values(+12 to+17),which suggest an origin from partial melts of a subducted oceanic slab.The granitic dykes have high SiO2 and K2 O contents and are characterized by en riched light rare earth elements(LREE)and slightly flat heavy rare earth elements(HREE),with negative Eu and Nb-Ta-Ti anomalies.These dykes are alkali-calcic and show geochemical features of highly fractionated Itype granites.Their positiveεHf(t)values(+16 to+17)suggest that they were derived from a juvenile accreted oceanic crustal sou rce.The coeval diabase dykes have low SiO2 and K2 O contents but high TiO2,MgO and Mg#(54-59).They are enriched in LREE and show characteristics of enriched mid-ocean ridge basalts(E-MORB).The relatively high Ba/Th,slightly low Th/Ta ratios,and negative Nb-Ta anomalies imply a mantle source metasomatised by slab-derived fluids.Thus,these basic dykes were generated likely by partial melting of the upwelling asthenosphere mantle with a slight influence of slab-derived fluids.Therefore,we suggest that the formation of these Late Carboniferous dykes were triggered by a post-collisional slab breakoff and the Aqishan-Yamansu belt was a continental arc formed by southdipping subduction of the Kangguer oceanic plate.

关键词： Central Asian orogenic belt Eastern Tianshan adakitic Highly fractionated I-Type granite Slab breakoff

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Post-collisional ore-bearing adakitic porphyries from Gangdese porphyry copper belt,southern Tibet:Melting of thickened juvenile arc lower crust

Post-collisional ore-bearing adakitic porphyries from Gangde...

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中国科学院地质与地球物理研究所第11届（2011年度）...

作者： Jin-Xiang Li~*,Ke-Zhang Qin~*,Guang-Ming Li~*,Bo Xiao,Lei Chen,Jun-Xing Zhao Key Laboratory of Mineral Resources,Institute of Geology and Geophysics,Chinese Academy of Sciences,P.O.Box 9825,Beijing 100029,China

Porphyry Cu-Mo deposits,related to the Miocene adakitic porphyries from the Gangdese porphyry copper belt in the southern Tibet,formed in a post-collisional setting.Here,we present the new zircon U-Pb ages,whole-rock chemical,and Sr-Nd and zircon Hf isotopic data for the ore-bearing adakitic porphyries from Gangdese porphyry copper belt.LA-ICP-MS zircon dating for six samples yielded ages ranging from 19 Ma to 14 Ma,indicating they formed in the Miocene.The ore-bearing adalatic porphyries show SiO of 61.47-71.67%,KO of 3.29-4.74%,and high Sr content(394-1106 ppm),high Sr/Y ratios(63-158),and low Y(6.12-10.3 ppm) and heavy rare earth element contents(e.g.Yb=0.52-0.91 ppm).They show steep fractionated REE and flat HREE patterns,and strong enrichment in large ion lithophile elements(Cs,Rb,Ba,Th,and U) and depletion of high field strength elements(Nb),with positive Sr and negative Ti anomalies.There are no linear variations of Ba,La,Sr/Y,Dy/Yb, (Sr/Sr),andεNd(t) with increasing SiO content.Combined with the zircon positiveεHf(t) values,and wide range of(Sr/Sr)(0.70559 to 0.70908) and ofεNd(t)(-6.8 to 0) values for all the adakitic samples,they were likely derived from the melting of garnet-bearing amphibolite in the juvenile arc mafic lower crust.Additionally, the adalatic porphyries with low Th/Nb ratios have lower initial Sr/Sr,and higherεNd(t) andεHf(t) values, and those with high Th/Nb show higher initial Sr/Sr,and lowerεNd(t) andεHf(t) values.This indicates that the juvenile arc lower crust is derived from the melting of the mantle wedge that was metasomatized by slab fluid or sediment melt during the Neotethyan ocean subduction.Significantly,the juvenile arc lower crust possibly inherited the arc magma characteristics of abundant in F,CI,and Cu and high oxidation state,which contributed to the porphyry Cu-Mo deposits in the Gangdese porphyry copper belt.

关键词： adakitic Juvenile arc lower crust Hf isotope Porphyry copper deposit Gangdese

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西藏碰撞后adakitic斑岩:洋壳部分熔融和壳幔作用的地球化学和同位素限制

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地质学报 2003年第2期77卷 202-202页

作者：高永丰侯增谦魏瑞华赵荣升 100037 中国地质科学院矿产资源研究所北京河北省国土资源厅 050031 石家庄经济学院

侵位于早期花岗岩基中的冈底斯中新世酸性斑岩主要受SN走向的裂谷带和正断层控制。斑岩的主要岩石类型为花岗间长斑岩、二长花岗斑岩和石英二长斑岩。斑岩高SiO;、Al;O;和低Y和HREE（Yb）含量,富集轻稀土元素（LREE）和大离子亲石元素（... 详细信息

侵位于早期花岗岩基中的冈底斯中新世酸性斑岩主要受SN走向的裂谷带和正断层控制。斑岩的主要岩石类型为花岗间长斑岩、二长花岗斑岩和石英二长斑岩。斑岩高SiO;、Al;O;和低Y和HREE（Yb）含量,富集轻稀土元素（LREE）和大离子亲石元素（LILE）,尤其富集Sr和K。斑岩显示出

关键词：部分熔融斑岩侵入岩碰撞后 adakitic

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