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Science China Earth Sciences 2004年第10期47卷 920-930页

作者： Deltlef Günther Institute of Inorganic Chemistry ETHZürichUniversitatsstrasse6CH-092ZürichSwitzerland

In-situ excimer laser ICP-MS analysis of minerals of eclogites and garnet pyrox- enites from type localities (Shuanghe, Maowu, Bixiling, and Yangkou) in the Dabie-Sulu ultra- high-pressure metamorphic belt reveals highly variable Ce anomalies from negative to positive in garnet. Similar Ce anomalies are also present in omphacite or clinopyroxene but to a much lesser extent. Such mixed negative and positive Ce anomalies mimic those found in severe weathering profiles developed under oxidizing conditions. They suggest the presence of sub- ducted sediment components in the eclogites and garnet pyroxenites, which in turn points to the potential importance of the recycled sediments in modification of the mantle composition during the deep subduction of the continental crust.

关键词： Dabie-Sulu, eclogite, garnet pyroxenite, LA-ICP-MS, subducted sediment, Ce anomaly.

Origin of the LLSVPs at the base of the mantle is a consequence of plate tectonics-A petrological and geochemical perspective

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Geoscience Frontiers 2018年第5期9卷 1265-1278页

作者： Yaoling Niu China University of Geosciences Beijing 100083China Department of Earth Sciences Durham UniversityDurhamDH1 3LEUK Laboratory for Marine Geology Qingdao National Laboratory for Marine Science and TechnologyQingdao 266061China Institute of Oceanology Chinese Academy of SciencesQingdao 266071China

In studying the petrogenesis of intra-plate ocean island basalts(OIB) associated with hotspots or mantle plumes, we hypothesized that the two large-low-shear-wave-velocity provinces(LLSVPs) at the base of the mantle beneath the Pacific(Jason) and Africa(Tuzo) are piles of subducted ocean crust(SOC)accumulated over Earth's history. This hypothesis was formulated using petrology, geochemistry and mineral physics in the context of plate tectonics and mantle circulation. Because the current debate on the origin of the LLSVPs is limited to the geophysical community and modelling discipline and because it is apparent that such debate cannot be resolved without considering relevant petrological and geochemical information, it is my motivation here to objectively discuss such information in a readily accessible manner with new perspectives in light of most recent discoveries. The hypothesis has the following elements:(1) subduction of the ocean crust of basaltic composition to the lower mantle is irreversible because(2) SOC is denser than the ambience of peridotitic composition under lower mantle conditions in both solid state and liquid form;(3) this understanding differs from the widespread view that OIB come from ancient SOC that returns from the lower mantle by mantle plumes, but is fully consistent with the understanding that OIB is not derived from SOC because SOC is chemically and isotopically too depleted to meet the requirement for any known OIB suite on Earth;(4) SOC is thus the best candidate for the LLSVPs, which are, in turn, the permanent graveyard of SOC;(5) the LLSVPs act as thermal insulators, making core-heating induced mantle diapirs or plumes initiated at their edges, which explains why the large igneous provinces(LIPs) are associated with the edges of the LLSVPs;(6) the antipodal positioning of Jason and Tuzo represents the optimal momentum of inertia, which explains why the LLSVPs are stable in the spinning Earth.

关键词： LLSVPs subducted ocean crust subducted mantle lithosphere No superplumes Mantle chemical differentiation Optimal momentum of inertia

Geochemical characteristics of Cretaceous basaltic rocks in South China and constraints on Pacific plate subduction

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Science China Earth Sciences 2005年第12期48卷 2104-2117页

作者： CHEN Weifeng CHEN Peirong XU Xisheng ZHANG Min The State Key Laboratory of Mineral Deposit Research Department of Earth Sciences Nanjing University Nanjing 210093 China The State Key Laboratory of Mineral Deposit Research Department of Earth Sciences Nanjing University Nanjing 210093 China The State Key Laboratory of Mineral Deposit Research Department of Earth Sciences Nanjing University Nanjing 210093 China The State Key Laboratory of Mineral Deposit Research Department of Earth Sciences Nanjing University Nanjing 210093 China

Middle-Late Cretaceous Basaltic rocks (85―110 Ma) are distributed in the contemporaneous downfaulted red basins and volcanic-sedimentary basins in South China (including Hunan, Jiangxi, Guangdong, Fujian, Zhejiang provinces). They are geographically divided into two groups delimited by Wuyishan Range, namely the west area basaltic rocks (WABs) distributing over the west of Wuyishan Range and the east area basaltic rocks (EABs) distributing over the east of Wuyishan Range, and observed having distinct geochemical and isotopic characters. WABs are characterized by relatively low in K2O (0.44%―3.17%), alkalis (K2O+Na2O= 3.27%―6.80%) and Al2O3 (13.08%―16.75%) contents, but high in MgO (5.13%―8.78%) and TiO2 (1.12%―3.35%) contents. WABs are similar to ocean-island basalts (OIB) or intraplate basalts on trace elements and isotopes: no negative Nb and Ta anomalies, relatively low ∑REE (74.66 μg/g―287.72 μg/g) and LaN/YbN (4.49―22.10), low (87Sr/86Sr)i (average ratio is 0.704679), high εNd(t) (?1.81―8.00). In contrast, EABs display relatively high in K2O (0.55%―4.86%), alkalis (K2O+Na2O=2.95%―7.55%) and Al2O3 (15.80%―21.10%) contents, but low in MgO (2.63%―6.28%) and TiO2 (1.19%―1.86%) contents, strong negative Nb and Ta anomalies, enrichment in LILE (K, Rb, Ba and Th), relatively high ΣREE (79.68 μg/g―327.61 μg/g) and LaN/YbN (5.25―26.37), high (87Sr/86Sr)i (average ratio is 0.707658) and negative εNd(t) (?8.50― ?1.22), similar to that of IAB (island arc basalts) or CAB (continental arc basalts). Accordingly, WABs were probably generated under continental rifting tectonic setting related to asthenosphere upwelling, and hence their source was characterized by mixing between EMⅡ with DM. Source of EABs may be enriched lithoshperic mantle which had ever undergone the metasomatism of fluid/melt derived from the subducted Pacific *** indicates that subduction of a paleo-Pacific plate (Kula) beneath the Eurasian continent had ever occurred during the late Mesozoic period,

关键词： basalt, imprint of subducted plate, rifting, Cretaceous basins, South China.

Eclogites from the Northern Dabie Mountains, eastern China: Geochemical characteristics, Sr-Nd isotopic compositions and tectonic implications

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Science China Earth Sciences 2000年第S1期43卷 178-188页

作者：刘贻灿徐树桐李曙光江来利吴维平陈冠宝苏文 Department of Earth and Space Sciences University of Science and Technology of China Hefei 230026 China Anhui Institute of Geology Hefei 230001 China

The petrologic geochemical and Sr-Nd isotopic compositions of the eclogites from the mafic-ultramafic rock belt (MUMRB) in the Northern Dabie Mountains indicate that: (1) the protoliths of most of eclogites are tholeiitic basalt and a few may be gabbro, and most of them produced from the Yangtze subducted continental crust (lower crust and formed during the deep subduction) and a part may be from paleo-oceanic relics between the Yangtze and North China continental plates; (2) their positive Nb anomalies and related trace element characteristics show that they did not form in the island-arc setting; (3) the metamorphosed MUMRB with eclogite and meta-peridotite blocks along the southern part of the Mozitan-Xiaotian fault zone may represent the suture zone produced during the collision between the Yangtze and North China continental plates, which included the Yangtze subducted continental crust and paleo-oceanic relics.

关键词： eclogite Sr-Nd isotopic composition Yangtze subducted continental crust paleo-oceanic relics Northern Dabie Mountains.