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Fractionation of platinum group elements in upper mantle: evidence from peridotite xenoliths from Wangqing

Science China Earth Sciences 1998年第4期41卷 354-361页

作者：徐义刚 B.Orberger S.J.Reeves 1. Guangzhou Institute of Geochemistry Chinese Academy of Sciences 510640 Wushan China 2. Laboratoire de geochronologie Universite F-75251 Paris 7 Paris France 3. School of Earth Sciences University of Melbourne 3052 Parkville Victoria Australia

The peridotite xenoliths from Wangqing display a downward\|concave PGE pattern with Pt at maximum due to Pt-Pd fractionation, which is different from the flat or negatively sloped patterns commonly observed for worldwide peridotite xenoliths and massifs. Taking into account the difference in partition coefficients of Pt and Pd between alloy and sulfide melt, it is suggested that some of the Wangqing peridotites must have been equilibrated with a melt in which alloy and sulfide coexisted. Segregation of Pt-rich alloy from Pd-sulfide melts due to density contrast and extraction of residual melts without sulfide saturation resulted in the fractionation of Pt from Pd.

关键词： PGE geochemistry peridotite xenolith upper mantle Wangqing Jilin.

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Petrography and Geochemistry of Precambrian Basement Straddling the Cameroon-Chad Border:The Touboro Baibokoum Area

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International Journal of Geosciences 2014年第4期5卷 418-431页

作者： Naimou Seguem Ganwa Alembert Alexandre Urs Klotzli Amadou Diguim Kepnamou Ekodeck Georges Emmanuel Department of Geology Faculty of Sciences and TechniquesUniversity Adam Barka of AbecheAbecheChad Department of Earth Sciences Faculty of SciencesUniversity of NgaoundereNgaoundereCameroon Labor für geochronologie Department für LithospharenforschungUniversitat WienWienAustria Department of Earth Sciences Faculty of SciencesUniversity of Yaounde IYaoundeCameroon

The border of Cameroon and Chad is characterized by a Precambrian basement straddling the Touboro-Ba?bokoum area;this basement is made up of gneiss, amphibolite and granitoids (granite, syenite, granodiorite). The studied rocks display high-K calk-alcalcaline to shoshonitic characteristic. Granitoids are metaluminous. Rocks under study derived from partial melts from metabasaltic to metatonalitic sources, and partial melts from metagreywackes. They shear the same origin as many granitoids describe westward in the Meiganga area and west Cameroon. This shows that the basement straddling the Touboro-Ba?bokoum area belongs to the Adamawa-Yadé Domain of the Central African Fold Belt.

关键词： Precambrian Basement Touboro-Baibokoum Cameroon Chad Adamawa-Yade Domain Central African Fold Beld

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大别山的构造变形期次和超高压岩石折返的动力学

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地质学报 2003年第1期77卷 44-54,T003页

作者：林伟王清晨 Michel Faure 孙岩舒良树 Urs Scharer 中国科学院地质与地球物理研究所 Dept des Science de la Terre University d'Orleans UMR 6530 Orleans France 南京大学地球科学系 Laboratoire de geochronologie Universite Paris 7 and IPG-Paris Paris75251France

从构造关系上看,大别山可分为南部,中部和北部3个构造系统。大别山南部构造系统为一套(原地)构造堆叠系统(相对的),从上到下依次为:①未变质的震旦纪—早三叠世沉积盖层,它被造山后的侏罗—白垩纪砂-砾岩不整合覆盖;②弱变质的新元古代... 详细信息

从构造关系上看,大别山可分为南部,中部和北部3个构造系统。大别山南部构造系统为一套(原地)构造堆叠系统(相对的),从上到下依次为:①未变质的震旦纪—早三叠世沉积盖层,它被造山后的侏罗—白垩纪砂-砾岩不整合覆盖;②弱变质的新元古代板岩;③高压变质岩系(宿松群),这些变质岩系大多退变质为绿片岩相;④含柯石英榴辉岩超高压变质单元的异地系统;⑤未经历超高压变质作用的原地(相对的)片麻岩系。北西-南东向的拉伸线理在各个地质单元均有表现。从动力学上看,上盘指向NW的剪切运动被后期的褶皱所改变。大别山中部为(混合岩)热穹窿改造系统,系经历了超高压变质作用的地体叠加了混合岩化作用的产物,它与超高压变质地体的界限为一拆离断层,而正是这个拆离断层使超高压变质地体向地表折返并经历了角闪岩相的退变质作用。大别山北部为构造堆叠系统,早期的面理和南北向的挤压线理被轴面北倾的褶皱所改造,这种褶皱对应于大别山中部同折返期的韧性变形的隆升构造。同时建立了地球动力学模型并讨论了逆冲作用和正断层的作用。

关键词：大别山伸展构造变形折返过程运动学动力逆冲作用正断层变质岩

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Experimental and petrological constraints on local-scale interaction of biotite-amphibole gneiss with H_2O-CO_2-(K,Na) Cl fluids at middle-crustal conditions:Example from the Limpopo Complex,South Africa

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Geoscience Frontiers 2012年第6期3卷 829-841页

作者： Oleg G.Safonov Elizaveta I.Kovaleva Svetlana A.Kosova H.M.Rajesh Georgy A.Belyanin Maria A.Golunova Dirk D.Van Reenen Institute of Experimental Mineralogy RAS ChernogolovkaMoscow Region 142432.Russia Department of Petrology.Moscow State University Moscow 119899Russia Department of Geology University of JohannesburgP.O.Box 524Auckland Park 2006JohannesburgSouth Africa Labor fur geochronologie Department fur LithospharenforschungUniversitat WienAlthanstrasse 14A-1090 ViennaAustria Institute of Experimental Mineralogy RAS ChernogolovkaMoscow Region 142432Russia Department of Geology University of JohannesburgP.O.Box 524Auckland Park 2006Johannesburg.South Africa

Reaction textures and fluid inclusions in the -2.0 Ga pyroxene-bearing dehydration zones within the Sand River biotite-hornblende orthogneisses （Central Zone of the Limpopo Complex） suggest that the formation of these zones is a result of close interplay between dehydration process along ductile shear zones triggered by H2O-CO2-salt fluids at 750--800 ℃ and 5.5--6.2 kbar, partial melting, and later exsolution of residual brine and H2O-CO2 fluids during melt crystallization at 650--700 ℃. These processes caused local variations of water and alkali activity in the fluids, resulting in various mineral assemblages within the dehydration zone. The petrological observations are substantiated by experiments on the interaction of the Sand River gneiss with the H2O-CO2-（K, Na）Cl fluids at 750 and 800 ℃ and 5.5 kbar. It follows that the interaction of biotite-amphibole gneiss with H2O-CO2-（K, Na）CI fluids is accompanied by partial melting at 750--800 ℃. Orthopyroxene-bearing assemblages are characteristic for temperature 800 ℃ and are stable in equilibrium with fluids with low salt concentrations, while salt-rich fluids produce clinopyroxene-bearing assemblages. These observations are in good agreement with the petrological data on the dehydration zones within the Sand River olthogneisses.

关键词： Charnockite Fluid-rock interaction CO2-rich fluids NaCl-KCl brines Partial melting Experimental petrology

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Mesozoic Extensional Tectonics in Eastern Asia:The South Liaodong Peninsula Metamorphic Core Complex(NE China)

Mesozoic Extensional Tectonics in Eastern Asia:The South Lia...

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中国科学院地质与地球物理研究所2008学术年会

作者： Michel Faure Patrick Monie Urs Scharer Dominique Panis Institut des Sciences de la Terre d'Orleans Centre National de la Recherche Scientifique(CNRS) Unite Mixte de Recherche(UMR) 6113Batiment GeosciencesUniversite d'OrleansF45067 Orleans Cedex 2France. geochronologie Geosciences Azur CNRS UMR 6526Universite Nice-Sophia Antipolisparc ValroseF-06108 NiceFrance.

In the North China block,the south Liaodong Peninsula massif is an elliptical metamorphic core complex(MCC) with a long axis trending *** cross-section view,it is asymmetric,with a steeply dipping northwestern flank and a gently dipping southeastern *** consists of three lithotectonic units:a gneissic migmatite unit,a Paleo-to Meso-Proterozoic micaschist-slate unit,and a Neoproterozoic to Mesozoic sedimentary *** deformation events related to extensional tectonics are distinguished in the study area:D is a ductile deformation related to the exhumation of the MCC;the following event,D,corresponds to the development of recumbent folds formed during the early exhumation of the MCC;and the youngest event,D,corresponds to brittle normal faulting that controlled the opening of a Cretaceous continental half-graben basin.A pre-D event characterized as northward verging is interpreted as the result of N-S shortening that occurred in the Late Triassic during the final stages of the collision between the North and South China *** ductile and brittle structures were developed coevally,with synkinematic plutonism and formation of *** Ar/Ar and U/Pb Cretaceous ages obtained from the mylonitic granodiorite,gneissic migmatite,orthogneiss,and granite indicate that the south Liaodong Peninsula MCC is contemporaneous with other Cretaceous extensional structures,such as numerous syntectonic plutons bounded by ductile normal faults,MCC,and half-graben basins,described in eastern *** the several hypotheses proposed to account for the Mesozoic extension along the eastern margin of Eurasia,lithosphere convective removal appears to be the most likely.

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