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Acta Geologica Sinica(English Edition) 2019年第2期93卷 496-498页

作者： ZHI Qian LI Yongjun YANG Gaoxue DUAN Fenghao TONG Lili School of Earth Science and Resources Chang'an University Key Laboratory for the Study of Focused Magmatism and Giant Ore Deposits MNR

Objective Mafic magmas can form in different tectonic settings with various geochemical characteristics depending on their mantle sources. Basalts generated in back-arc basins provide valuable perspectives on mantle s... 详细信息

关键词： Ma back-arc West Junggar Xinjiang Geological Significance

Intra-continental back-arc basin inversion and Late Carboniferous magmatism in Eastern Tianshan,NW China:Constraints from the Shaquanzi magmatic suite

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Geoscience Frontiers 2017年第6期8卷 1447-1467页

作者： Hongjun Jiang Jinsheng Han Huayong Chen Yi Zheng Wanjian Lu Gang Deng Zhixiong Tan Key Laboratory of Mineralogy and Metallogeny Guangzhou Institute of GeochemistryChinese Academy of SciencesGuangzhou 510640China Graduate University of Chinese Academy of Sciences Beijing 100049China Guangdong Provincial Key Laboratory of Mineral Physics and Materials Guangzhou 510640China Department of Earth Sciences Sun Yat-sen UniversityGuangzhou 510472China No.6 Geological Party Xinjiang Bureau of Geology and Mineral ExplorationHami 839000China

The Yamansu belt,an important tectonic component of Eastern Tianshan Mountains,of the Central Asian Orogenic Belt,NW China hosts many Fe-(Cu)deposit.In this study,we present new zircon U-Pb geochronology and geochemical data of the volcanic rocks of Shaquanzi Formation and diorite intrusions in the Yamansu belt.The Shaquanzi Formation comprises mainly basalt,andesite/andesitic tuff,rhyolite and sub-volcanic diabase with local diorite intrusions.The volcanic rocks and diorites contain ca.315-305 Ma and ca.298 Ma zircons respectively.These rocks show calc-alkaline affinity with enrichment in large-ion lithophile elements(LILEs),light rare-earth elements(LREEs),and depletion in high field strength elements(HFSEs)in primitive mantle normalized multi-element diagrams,which resemble typical back-arc basin rocks.They show depleted mantle signature with ε_(Nd)(t)ranging from+3.1 to +5.6 for basalt;+2.1 to+4.7 for andesite;-0.2 to+1.5 for rhyolite and the ε_(Hf)(t)ranges from-0.1 to +13.0 for andesites;+5.8 to +10.7 for andesitic tuffs.We suggest that the Shaquanzi Formation basalt might have originated from a depleted,metasomatized lithospheric mantle source mixed with minor(3-5%)subduction-derived materials,whereas the andesite and rhyolite could be fractional crystallization products of the basaltic magma.The Shaquanzi Formation volcanic rocks could have formed in an intracontinental back-arc basin setting,probably via the southward subduction of the Kangguer Ocean beneath the Middle Tianshan Massif.The Yamansu mineralization belt might have undergone a continental arc to back-arc basin transition during the Late Carboniferous and the intra-continental back-arc basin might have closed in the Early Permian,marked by the emplacement of dioritic magma in the Shaquanzi belt.

关键词： Shaquanzi igneous rocks Geochronology Geochemistry Intra-continental back-arc basin Yamansu belt Eastern Tianshan Mountains

Origin of Cu in the PACMANUS hydrothermal field from the eastern Manus back-arc basin: evidence from mass balance modeling

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Acta Oceanologica Sinica 2019年第9期38卷 59-70页

作者： Yao Ma Xiaoyuan Wang Shuai Chen Xuebo Yin Bowen Zhu Kun Guo Zhigang Zeng Key Laboratory of Marine Geology and Environment Institute of Oceanology Chinese Academy of Sciences Qingdao 266071 China Laboratory for Marine Mineral Resources Pilot National Laboratory for Marine Science and Technology (Qingdao) Qingdao 266071 China University of Chinese Academy of Sciences Beijing 100049 China Ocean Science Isotope and Geochronology Center Pilot National Laboratory for Marine Science and Technology (Qingdao) Qingdao 266071 China

Hydrothermal precipitates associated with active vents in the eastern Manus Basin, an actively opening back-arc basin in the Bismarck Sea, Papua New Guinea, are among the most Cu-rich on the modern seafloor. The volcanic rocks associated with this mineralization may be insufficiently enriched in Cu to account for the Cu content of the sulfides by simple leaching. The PACMANUS hydrothermal field lies in the eastern portion of the eastern Manus Basin. Mass balance modeling of the PACMANUS hydrothermal system indicates that simple leaching of a stationary reaction zone (0.144 km^3) by hydrothermal fluids cannot yield the Cu found in associated sulfide deposits because unacceptably high leaching, transportation and precipitation efficiencies are required to derive the Cu in sulfides by leaching processes. With 100% leaching, transport and precipitating efficiency, 0.166 km^3 of volcanic rocks would need to be leached to account for the Cu budget of hydrothermal sulfide deposits. The key requirement for forming metal-rich magmatic fluids is a large amount of metals available to enter the exsolved vapor phase. Magmas generated in the eastern Manus Basin inherently have high fO2 because of metasomatism of the mantle source by oxidized materials from the subducted slab, leading to copper enrichment in the magma chamber. Moreover, the presence of Cu in gas-rich melt inclusi on bubbles in Pual Ridge andesite is evidence that degassing and partitioning of Cu into the magmatic volatile phase has occurred in the eastern Manus Basin. Numerical mass balance modeling indicates that approximately 0.236 Mt Cu was potentially transferred to the hydrothermal system per cubic kilometer magma. Magmatic degassing seems to play a more significant role than leaching.

关键词： back-arc basin mass balance model PACMANUS hydrothermal field source of Cu

Mantle-derived Xenoliths and the Token of a Modern back-arc Geotherm Beneath Eastern China

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Science China Chemistry 1994年第4期37卷 472-480页

作者：金振民 H.W.GreenII R.S.Borch 金淑燕 T.N.Tingle T.E.Young Department of Geology university of CaliforniaDavisCA95616USA Department of Geology University of California Daves CA95616USA. Division of Geomechanics China University of Geosciences Wuhan 430074 PRC

Xenoliths of garnet and spinel-garnet 1herzolite from Mingxi, Eastern China have been studied in terms of comprehensive methods of mineralogy, petrology, fabrics, mierostructures and infrared spectrum. The temperature and pressure equilibration of the xenolith have been calculated using the TEMPEST program with the two-pyroxene geothermometer of Bertrand and Mercier (1985) combined with the geobarometer of Nickel and Green (1985). The temperature and pressure of xenoliths range from^1300 K at 1. 9 GPa (60 km) to ~1500 K at 2. 6 GPa (80 km). The geotherm inferred from xenolith is excellently consistent with the measured surface heat flow (70 mW/m2) in Mingxi. A character of geothermal curve and conductive type suggest that these xenoliths are from the lithosphere, not from the asthenosphere. The geotherm and mierostructures and preferred orientations of minerals in the xenolith are consistent with tecon-ic thinning of the lithosphere in the present-day extensional back-arc environment.

关键词： mantle xenolith spinel-garnet Iherzolite geotherm thermal structure of the lithosphere extensional back-arc environment.

Genesis and Geodynamic Significance of Chromitites from the Fuchuan Ophiolite,Southern China,as Evidenced by Trace Element Fingerprints of Chromite,Olivine and Pyroxene

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Acta Geologica Sinica(English Edition) 2023年第1期97卷 134-148页

作者： WU Jun LIU Ting WANG Fangyue Anhui Technical College of Industry and Economy Hefei 230051China Hefei University of Technology Hefei 230009China

The Fuchuan ophiolite is located in the northeasternmost segment of the Neoproterozoic Jiangnan orogen and consists mainly of harzburgites,with minor dunites,pyroxenite and gabbro veins and dykes.In order to investigate the genesis and tectonic setting of the Fuchuan ophiolite and chromitites,in situ analyses of unaltered chromites and silicates were carried out.Trace element analyses of unaltered chromites from the Fuchuan chromitites indicate the parental magma is of mid-ocean ridge basalt(MORB)-like origin,with the Ti/Fe^(3+#)–Ga/Fe^(3+#)diagram of chromites showing that the chromitites are a result of melt/rock interaction of MORB melts with mantle peridotites,and that the Fuchuan harzburgites present the dual features of MORB and supra-subduction zone peridotites(SSZP).Trace and rare earth element(REE)analyses of olivines and orthopyroxenes from the Fuchuan harzburgites hint at the possibility of mantle metasomatism influenced by SSZ-subducted fluids.Finally,integrating with previous study,the Fuchuan ophiolite and chromitites might have been formed in a back-arc spreading ridge between the Yangtze and Cathaysia blocks during the Neoproterozoic.

关键词： igneous petrology trace elements metasomatism back-arc ophiolite Precambrian

Generation of back-arc Basins as Side Effect of Shortening Processes: Examples from the Central Mediterranean

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International Journal of Geosciences 2014年第10期5卷 1062-1079页

作者： Enzo Mantovani Marcello Viti Daniele Babbucci Caterina Tamburelli Nicola Cenni Massimo Baglione Vittorio D’Intinosante Dipartimento di Scienze Fisiche della Terra e dell’Ambiente Università degli Studi di Siena Siena Italy Dipartimento di Scienze Biologiche Geologiche e Ambientali Università degli Studi di Bologna Bologna Italy Ufficio Prevenzione Sismica Regione Toscana Firenze Italy

The evolution of the Mediterranean area since the Oligocene-Lower Miocene has been driven by the convergence of the surrounding plates. This implies that the observed deformation pattern in that region must be the most convenient shortening pattern, i.e. the one controlled by the minimum action principle. To understand why the fulfilment of such condition has required a complex spatio-temporal distribution of major tectonic events, such as uplift, lateral displacement and bending of orogenic belts, consumption of large lithospheric domains and formation of back arc basins, it may be very useful to take into account a basic tectonic concept, which helps to identify the process that can minimize the resistance of tectonic forces. Such concept starts from the fact that the most convenient consumption process is the one that involves low buoyancy oceanic lithosphere (Tethyan domains). However, such process is highly favoured where the oceanic lithosphere is stressed by vertical forces, a situation that develops when orogenic wedges are forced to over thrust and load the oceanic domain to be consumed. This interpretation can provide plausible and coherent explanations for the complex pattern of the observed deformations. In this view, the generation of back arc basins is taken as a side effect of an extrusion process, as suggested by numerical and mechanical experiments.

关键词： Central Mediterranean Extrusion Tectonics back-arc Basins

Sm-Nd dating and Nd-Sr isotopic characteristics of the Shimian ophiolite suiten,Sichuan Province

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Chinese Science Bulletin 2002年第22期47卷 1897-1901页

作者： SHEN Weizhou XU Shijin GAO Jianfeng YANG Zhusheng YANG Qiwen Department of Earth Sciences and State Key Laboratory of Mineral Deposit Research Nanjing UniversityNanjing 210093China Geological Survey Institute Panxi Geological TeamSichuan Bureau of Geology and Mineral Exploration and DevelopmentXichang 615000China

By mcasuring the Sm-Nd and Rb-Sr isotopiccompositions of harzburgite and gabbro from Shimianophiolite suite, we got the whole rock Sm-Nd isochron age of(938 ± 30) Ma (2σ), and the e Nd of 7.6 ± 0.8 (2σ), which showsthat the ophiolite was formed at the Early Neoproterozoic.The obvious change (0.70209-0.70708) of Isr values of theophiolite is caused by the meteoric hydrothermal alteration.The high εNd values indicate that the primitive magma wasderived from the intense depleted mantle rescrvoir. It is sug-gested that this area was in a back-arc basin environmentduring the Early Neoproterozic.

关键词： Sm-Nd dating Nd-Sr isotopes ophiolite suite back-arc basin Shimian County Sichuan Province.

An alternative tectonic model for the Yarlung Zangbo suture zone

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Science China Earth Sciences 2010年第1期53卷 27-41页

作者： LIU XiaoHan JU YiTai WEI LiJie LI GuangWei Institute of Tibetan Plateau Research Chinese Academy of SciencesBeijing 100085China Mineral Resource Institute of China Metallurgical Geology Bureau Beijing 100025China

The new field investigations along the Yarlung Zangbo ophiolites zone show that these series underwent low green-schist metamorphism and were then fractured and occurred as slabs in tectonic melanges,without regional tectonic polarity.No large shear zone in north-south direction has been identified between ophiolite bodies and flysch layers on both side and a conformable contact relationship can be observed locally between them.A great mass of tectonic mélange has been substantiated as submarine olistolith bodies.The Mesozoic sedimentary facies and its evolution in both north and south of the ophiolite zone are corresponding in time.The ophiolite zone has often been divided into parallel branches,separated by narrow flysch slats.There is also a similarity of the Paleozoic and the basement of the High Himalaya,Lhasa and Qiangtang Terranes,and they are distinctly different from those of the Indian continent.The geologic information does not warrant a postulate that the Himalaya and Tibet were once separated by a great ocean;it is therefore consistent with an alternative tectonic model by back-arc basin collapse with its juvenile narrow oceanic crust.The real plate tectonic suture,the Neotethys might be covered under the Miocene Siwalik molasse in the southern slope of the High Himalaya range.Based on the new model,the Neotethyan ocean floor was subducted beneath the Asia since the Late Triassic.The outer continental margin of Eurasia was split from the Lhasa Terrane so that a back-arc basin came into existence.Hemi-pelagic and deep sea sediments were deposited before the Late Cretaceous flysch sedimentation,with the linear juvenile oceanic crust when back-arc volcanism occurred in the Gandese region.The Yarlung Zangbo back-arc basin was eventually eliminated when the High Himalayas were sutured onto Eurasia.The ocean floor lightly underthrusted to north and south sides,sediments of the basin were deformed as fold-thrusting.The Neotethys was eliminated during the Tertiary when India collided with Himalaya arc from t

关键词： Yarlung Zangbo Ophiolite Zone plate boundary continental marginal arc relic back-arc basin alternative tectonic model

Isotopic Characteristics and Age Dating of the Pumice in Okinawa Trough

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Science China Chemistry 1994年第7期37卷 870-878页

作者：陈丽蓉翟世奎申顺喜 Institute of Oceanology Academia Sinica

The data on the isotope compositions of rubidium,strontium and oxygen in the pumice ofOkinawa Trough are reported for the first time.The ages of the pumice were successfully dated with themethod of U-series disequilibrium.Then,the material source,crystallization evolution of magma and activi-ty cycles of volcanos are explored.Isotopic data show that pumice magma was originally from the mantle,but had undergone a full crystal-lization differentiation and had been contaminated to a fair extent by crust-derived materials before the mag-ma was erupted out of the sea floor.According to the dating results available so far,the earliest volcaniceruption in Okinawa Trough occurred about 70,000 a ago and the latest eruption was about 10,000 a B.P.During this period,there were three volcanic eruption cycles which were respectively corresponding to themiddle Late Pleistocene,the late Late Pleistocene and the Early Holocene.

关键词： back-arc magmatism isotope age Okinawa Trough

Geochronology, geochemistry and tectonic implications of Xiongshan diabasic dike swarm, northern Fujian

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Science China Earth Sciences 1997年第4期40卷 411-417页

作者：任胜利李继亮周新华孙敏 Department of Earth Science China University of Geosciences Beijing 100083 China Institute of Geology Chinese Academy of Sciences Beijing 100029 China Department of Earth Sciences University of Hong Kong Hong Kong

Sm/Nd isotopic age determination showed that Xiongshan dike swarm was at 585.7 Ma±30 Ma. The trace element geochemistry and Sr/Nd/Pb isotope geochemistry studies indicate that the dike swarm was products of back-arc basin spreading ridge and the magma originated from the depleted mantle region which was metasomatized by LTLE-rich liquids/melts derived from subduction slab.

关键词： dike swarm petrochemistry Sinian-early Paleozoic back-arc basin northern Fijian