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中国矿物岩石地球化学学会第11届学术年会

作者： Jochen Hoefs Klaus Simon Albrecht W．Hofmann Geowissenschaftliches Zentrum der Universitt Gttingen Goldschmittstrasse 1D-37077 GttingenGermany Geowissenschaftliches Zentrum der Universitt Gttingen Goldschmittstrasse 1D-37077 GttingenGermany Max-Planck Institute fuer Chemie Postfach 3060D-55020 MainzGermany

＜正＞Compared with the oceanic crust, knowledge about the formation of the continental crust （CC） is relatively poor. Although melting of subducted slabs in the early history of the Earth has been considered as the major way that shaped the chemical characteristics of the CC by most geologists, as the CC shares many characteristics with modern adakites, some geologists argued that Archean TTG was formed in the same way as modern arcs rather than slab melting, whereas others proposed that melting at the bottom of the thickened oceanic crust was more important. Recently, the debate is mainly focused on the unique subchondritic Nb/Ta value of the CC, and particularly, how Nb and Ta fractionated from each other and consequently how, in detail, the CC was built.

关键词： niobium-tantalum fractionation slab subduction formation of continental crust

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Late Mesozoic rifting and its deep dynamic mechanisms in the central Sulu orogenic belt: Records from Lingshan Island

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Science China Earth Sciences 2022年第9期65卷 1751-1771页

作者： Tengfei ZHOU Yaoqi ZHOU Nina SФAGER Paul Martin HOLM Zhenkai ZHANG Jun WANG Zhao LIANG Hongyu MU Yanjun CHENG Feifei LIU Miao WANG Yue ZHANG Hui ZHANG Yangjian GU Shihui DONG Hanjie ZHAO Manjie LI Yang CHEN Yanzi LIU School of Geosciences China University of Petroleum(East China)Qingdao 266580China Department of Geosciences and Natural Resource Management University of CopenhagenCopenhagen-K 1350Denmark Shandong Provincial Key Laboratory of Deep Oil&Gas China University of Petroleum(East China)Qingdao 266580China Shaanxi Center of Mineral Geological Survey Shaanxi Institute of Geological SurveyXi'an 710068China School of Earth Sciences Yunnan UniversityKunming 650500China Department of Science and Technology Hebei GEO UniversityShijiazhuang 050031China College of Earth Science and Engineering Shandong University of Science and TechnologyQingdao 266590China School of Architectural Engineering Binzhou UniversityBinzhou 256500China Research Institute of Petroleum Exploration and Development Shengli Oilfield CompanySINOPECDongying 257015China Key Laboratory of Geological Safety of Coastal Urban Underground Space Ministry of Natural ResourcesQingdao Geo-Engineering Surveying InstituteQingdao 266101China

The Lingshan Island scientific drill confirms that two episodes(Laiyang period and Qingshan period) of rifting developed in the central Sulu orogenic belt(SOB) in Late Mesozoic. With a set of methods including fieldwork, drilling, core logging, zircon U-Pb dating and whole rock geochemistry applied, the age, the depositional sequence and the deep dynamic mechanisms of rift evolution were unraveled. The stratigraphic sequence of the Laiyang-Qingshan Groups on Lingshan Island was composed of two different rifting sequences:(1) Laiyang Group(147–125 Ma), which consists of deep-water gravity flow deposits with interlayers of intermediate volcanic rocks;and(2) Lower Qingshan Group(125–119 Ma), which unconformably overlies the former sequence and contains subaerial volcanic deposits and terrestrial deposits. The tectonic environment changed during the evolution of these two episodes of rifting: the rift was in a NNW-SSE extensional environment in the Laiyang period and showed the typical passive rifting character that “lithospheric extension and rifting preceded volcanism”. The passive rifting period was ended by a short WNW-ESE compression at about 125 Ma. After that, the tectonic environment transferred to a strong NW-SE extensional environment and the rifting evolved into a volcanic arc basin in the Qingshan period. The igneous rocks are shoshonitic to high-K calc-alkaline trachyandesites to trachytes with a few intercalated lamprophyres and a rhyolite.The geochemical characteristics of the igneous rocks indicate that they are mantle-derived melts with a metasomatized mantle source and/or crustal contamination. In addition, an increased thinning of the lithosphere happened during the rifting episodes.The low-angle subduction of the Paleo-Pacific plate in the Jurassic weakened the thickened SOB lithospheric mantle. The rollback of the subducting plate started in late Jurassic to early Cretaceous, and the SOB lithospheric mantle was delaminated synchronously because of the gravity collapse. Thus, this caused passive r

关键词： Sulu orogenic belt Lingshan Island Late Mesozoic Rifting slab subduction Basin dynamics

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Origin of ULVZs near the African LLSVP: Implications from their distribution and characteristics

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Earthquake Science 2021年第4期34卷 299-309页

作者： An Fan Xinlei Sun Guangzhou Institute of Geochemistry Chinese Academy of SciencesGuangzhou 610630China University of Chinese Academy of Sciences Beijing 101400China International Center for Planetary Science College of GeosciencesChengdu University of TechnologyChengdu 610059China

Ultra-low velocity zones(ULVZs)provide important information on the composition and dynamics of the core-mantle boundary(CMB).However,their global distribution and characteristics are not well constrained,especially near African large low-shear velocity provinces(LLSVPs).Here,we used ScS precursor(SdS)and postcursor(ScscS)phases recorded by various seismic networks in Africa and South America to investigate the ULVZ characteristics underlying the South Atlantic Ocean.We found no evidence of ULVZs near the SE boundary of South America,but an ULVZ was found within the SW boundary of the African LLSVP,with thicknesses ranging from 11–18 km and reductions in S-wave velocities of 18%–34%.Our results,combined with the global distribution of ULVZs,suggest that thermal activity may be essential to ULVZ formation.Moreover,subducted slab and mantle flow may also play a key role,depending on the location of the ULVZs.

关键词： ultra-low velocity zone slab subduction mantle flow thermal effect African large low-shear velocity province.

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Relations between Adakitic Diorite and Eclogite from the UHP Belt on the Northern Margin of Qaidam Basin: Evidence from Geochemistry and Zircon U-Pb Age

Relations between Adakitic Diorite and Eclogite from the UHP...

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2004年全国岩石学与地球动力学研讨会

作者： SHI Rendeng, YANG Jingsui, WU Cailai Key Laboratory of Continental Dynamics of the Ministry of Land and Sources, Institute of Geology, Chinese Academy of Geological Sciences 26 Baiwanzhuang Road, Beijing, 100037, China

The diorite cropping out at Jilusu on the northern margin of Qaidam basin has lots of adakite feature: SiO = 61.96～64.88 wt% (63.47 wt% on average of 8 samples, ≥56 wt%), AlO = 13.95～15.86 wt% (15.23 wt% on average of 8 samples, ≥15 wt%), MgO = 2.23～4.47 ( 3.56 wt% on average of 8 samples, >3 and slab partial melting at the depth of about 75～85 km, and the melting residues are considered to be garnet eclogites and garnet amphibolite. Generally, the presence of adakite is considered to be a sign of the initiation of slab subduction. The age of adakitic diorite is about 508 Ma dated by LA-ICP-MS, and the age of eclogite from the northern margin of Qaidam basin is 494 Ma dated by TIMS. This age evidence suggests that the slab subduction began in the later Cambrian, and the adakitic magma came into being while at the depth of about 75～85 km, and residues of partial melting with garnet face persisted in subducting and the garnet eclogite may have been formed in the early Ordovician period.

关键词： Adakite eclogite LA-ICP-MS slab subduction North of Qaidam

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