华南显生宙时期岩石圈地幔的性质与形成时代     

刘传周 《岩石矿物学杂志》2013,32(5):637-651

火山岩携带的橄榄岩捕虏体是研究深部岩石圈地幔成分特征与热结构状态的最直接样品。湖北大洪山早奥陶世钾镁煌斑岩携带的石榴二辉橄榄岩具有富集的地球化学特征,指示当时的岩石圈厚度可达110 km。华南内陆地区宁远和道县早侏罗世玄武岩所携带的地幔包体具有饱满的成分特征,代表遭受了较低程度部分熔融的地幔残留。宁远地幔包体的全岩Re-Os同位素特征显示该地区中生代大陆岩石圈地幔为从软流圈新增生而形成的新生地幔。这表明内陆地区古生代存在的富集地幔被完全拆沉,并被新生地幔所取代;中生代内陆地区的岩石圈拆沉作用可能与该地区自225 Ma以来大规模的岩石圈伸展作用有关。华南新生代地幔包体主要分布在沿海地区。通过地幔包体矿物成分估算获得的温度与压力资料揭示新生代沿海地区岩石圈厚度约为80～90 km,并具有热的地温梯度。无论是全岩还是硫化物的Re-Os同位素特征都表明沿海地区在新生代仍残留有古元古代岩石圈地幔,表明新生代沿海地区的拉张作用仅导致了岩石圈地幔的部分拆沉和减薄。  相似文献   

Multi-stage metamorphism by progressive accretion of continental blocks,example from the Western Hindu Kush     

Hezbullah Moiny  Shah Wali Faryad  Renata Čopjaková  Radim Jedlicka 《Journal of Metamorphic Geology》2020,38(7):693-717

Basement rocks from the Western Hindu Kush preserve evidence of multiple metamorphic and magmatic events that occurred along the boundary between the Archean–Proterozoic Afghan Central and Afghan–Tajik Blocks. To verify the different metamorphic stages or events, mineral textures and phase equilibria in metamorphic basement rocks and their age relations to magmatic episodes have been investigated. Quartzofeldspathic gneiss and migmatite with lenses of amphibolite (with assumed Proterozoic age for their metamorphism) are intruded by the Triassic Hindu Kush granitoid batholith and small Cretaceous and Oligocene granite intrusions. The age of thermal overprint (210–170 Ma) by the Triassic batholith is confirmed by new monazite data. Both Triassic and Cretaceous granitoids and surrounding basement rocks underwent subsequent metamorphism up to epidote–amphibolite facies. The degree of this metamorphism increases southward at the contact to the Kabul Block, which under-plates the Western Hindu Kush from the south. An early Miocene age was obtained by Pb–Th analyses in thorite and huttonite, which are close or slightly younger than the Oligocene granite in this area. The Cretaceous meta-granodiorite near the border with the Kabul Block contains xenoliths of granulite facies rocks that could come from the Neoarchean granulite facies basement of the Kabul Block. The multi-stage metamorphic and magmatic evolution classifies the Hindu Kush mountain belt as a long-lived suture zone that was active since the early Palaeozoic. The results of this study support the interpretation about possible relations of the Afghan Central Blocks to the southern margin of Eurasia during the evolution of Para- and Neotethys.  相似文献   

福建牛头山新近纪碱性玄武岩中地幔岩包体内硫化物研究   总被引：3，自引：0，他引：3  

岳可芬  赫英  刘文峰 《地质科学》2005,40(1):114-i004

福建牛头山一带新近纪碱性玄武岩中含有尖晶石二辉橄榄岩包体。这些地幔岩包体内普遍存在有硫化物。硫化物按产状和成因分为两类:1)分布于寄主矿物内部,未与裂隙相连,是地幔岩浆作用的产物;2)分布于颗粒内或颗粒边部,在裂隙上或与裂隙相连,是地幔流体交代作用的产物。电子探针分析表明,15个硫化物测点中,除2个黄铜矿、1个硫铜铁矿外,其余为不同Ni/Fe(mol比)比值的铁镍硫化物:6个测点为富镍镍黄铁矿,其Ni/Fe=0.98～2.79,(Fe+Ni)/S=1.03～1.08;2个为针镍矿,其Ni/Fe=5.5,(Fe+Ni)/S=1.01;4个测点为富镍磁黄铁矿,其Ni/Fe=0.29～0.49,(Fe+Ni)/S=0.79～0.94。4粒单一硫化物矿物的成份是不均一的,多数表现为自中心到边部Ni含量和Ni/Fe值呈增加趋势,而Fe和Cu含量呈减少趋势。本研究还发现单一硫化物中由中心到边部金与镍大致有相同的变化趋势。  相似文献   

Parameters controlling the density of welded ignimbrites—A case study on the Incesu Ignimbrite, Cappadocia, Central Anatolia     

P. Lepetit  L. Viereck-Goette  R. Schumacher  U. Mues-Schumacher  M. Abratis 《Chemie der Erde / Geochemistry》2009,69(4):341-357

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Interaction between protokimberlite melts and mantle lithosphere: Evidence from mantle xenoliths from the Dalnyaya kimberlite pipe,Yakutia (Russia)   总被引：2，自引：2，他引：0  

I.V. Ashchepkov  T. Ntaflos  Z.V. Spetsius  R.F. Salikhov  H. Downes 《地学前缘(英文版)》2017,8(4):693-710

The Dalnyaya kimberlite pipe(Yakutia,Russia) contains mantle peridotite xenoliths(mostly Iherzolites and harzburgites) that show both sheared porphyroclastic(deformed) and coarse granular textures,together with ilmenite and clinopyroxene megacrysts.Deformed peridotites contain high-temperature Fe-rich clinopyroxenes,sometimes associated with picroilmenites,which are products of interaction of the lithospheric mantle with protokimberlite related melts.The orthopyroxene-derived geotherm for the lithospheric mantle beneath Dalnyaya is stepped similar to that beneath the Udachnaya pipe.Coarse granular xenoliths fall on a geotherm of 35 mWm-2 whereas deformed varieties yield a 45 mWm-2)geotherm in the 2-7.5 GPa pressure interval.The chemistry of the constituent minerals including garnet,olivine and clinopyroxene shows trends of increasing Fe~#(=Fe/(Fe+Mg))with decreasing pressure.This may suggest that the interaction with fractionating protokimberlite melts occurred at different levels.Two major mantle lithologies are distinguished by the trace element patterns of their constituent minerals,determined by LA-ICP-MS.Orthopyroxenes,some clinopyroxenes and rare garnets are depleted in Ba,Sr,HFSE and MREE and represent relic lithospheric mantle.Re-fertilized garnet and clinopyroxene are more enriched.The distribution of trace elements between garnet and clinopyroxene shows that the garnets dissolved primary orthopyroxene and clinopyroxene.Later high temperature clinopyroxenes related to the protokimberlite melts partially dissolved these garnets.Olivines show decreases in Ni and increases in Al,Ca and Ti from Mg-rich varieties to the more Fe-rich,deformed and refertilized ones.Minerals showing higher Fe~#(0.11-0.15) are found within intergrowths of low-Cr ilmenite-clinopyroxene-garnet related to the crystallization of protokimberlite melts in feeder channels.In P-f(O_2) diagrams,garnets and Cr-rich clinopyroxenes indicate reduced conditions at the base of the lithosphere at-5 log units below a FMQ buffer.However,Cr-poor clinopyroxenes,together with ilmenite and some Fe-Ca-rich garnets,demonstrate a more oxidized trend in the lower part of lithosphere at-2 to 0 log units relative to FMQ.Clinopyroxenes from xenoliths in most cases show conditions transitional between those determined for garnets and megacrystalline Cr-poor suite.The relatively low diamond grade of Dalnyaya kimberlites is explained by a high degree of interaction with the oxidized protokimberlite melts,which is greater at the base of the lithosphere.  相似文献   

海南岛陆缘扩张带形成及新生代岩石圈动力学机制:来自幔源包体的地球化学证据     

蒋英  梁细荣  梁新权  付建刚  王策  周云  温淑女 《大地构造与成矿学》2017,41(1):157-182

海南岛陆缘扩张带蓬莱地区新生代玄武岩中捕获大量尖晶石二辉橄榄岩和方辉橄榄岩幔源包体。激光剥蚀等离子体质谱(LA-ICP-MS)分析结果表明,蓬莱地幔橄榄岩含有三种不同地球化学特征的单斜辉石(Cpx):(1)a类单斜辉石Mg~#=92.3~93.4,来自富集Cpx的二辉橄榄岩,具有极低的LREE和不相容元素含量,HREE平坦,Th、U、La、Sr正异常,经历了7%~10%的尖晶石相部分熔融,仅受到极低程度强不相容元素(Th、U、La、Sr)初期富集交代作用;(2)b类单斜辉石Mg~#=89.9~90.3,来自较富集Cpx的二辉橄榄岩,具有中等的LREE和LILE含量,HREE平坦,微量元素蛛网图上显示Th、U正异常,Rb、Ba、Nb、Ta、Sr、Ti负异常,经历4%~5%的尖晶石相部分熔融,可能受到了含LREE和Th、U等不相容元素的硅酸盐熔体交代;(3)c类单斜辉石Mg~#=91.4~92.8,来自贫Cpx的二辉橄榄岩和方辉橄榄岩,具有富集的LREE和LILE含量,HREE弱分异,微量元素蛛网图上显示Th、U正异常及强烈的Nb、Ta、Ti负异常,经历了8%~20%的尖晶石相部分熔融,其交代熔体可能是来自源区有石榴子石残留的碳酸盐熔体。全岩主、微量元素及模拟计算结果表明,这些幔源包体的主量元素主要受部分熔融程度影响,并且方辉橄榄岩经历的部分熔融程度大于二辉橄榄岩。地幔橄榄岩的Sr-Nd同位素组成表明该区具有MORB-OIB型亏损地幔特征。此外,蓬莱部分地幔橄榄岩包体显示正斜率的HREE分异特征((Gd/Yb)_N=0.4~0.7),暗示该区地幔经历了源自石榴子石稳定区的变压熔融,总体熔融程度为18%以上,指示了较高的地幔潜能温度。综合前人对海南岛新生代玄武岩最新研究成果,我们认为海南地幔柱可能为该区软流圈地幔置换古老岩石圈地幔提供了热源,导致了区域岩石圈地幔的破坏,从而引起包括地幔柱本身、软流圈和富集岩石圈的熔融。岩石圈地幔性质的改变和不均一性可能是海南岛陆缘扩张带新生代岩石圈减薄的主要动力学机制。  相似文献   

湖南省宁远──道县中生代玄武岩中辉长岩包体的岩石学初步研究   总被引：8，自引：1，他引：8  

郭锋  吴有林 《大地构造与成矿学》1996,20(1):38-45

宁远－道县中生代玄武岩中辉长岩包体的岩石学、矿物学等特征表明辉长岩与寄主玄武岩分属不同系列岩石。辉长岩为偏碱性拉斑质玄武岩的分异结晶产物，类似于似层状基性侵入体。它代表了本区较早的基性岩浆熔融和侵位事件，可能是地洼活动阶段早期的一种深部岩石圈活动表现。  相似文献   

岚皋金云角闪辉石岩类捕虏体特征   总被引：6，自引：0，他引：6  

徐学义  黄月华  夏林圻  夏祖春 《岩石矿物学杂志》1996,15(3):193-202

陕西岚皋地区碱质基性超基性潜火山杂岩中的金云角闪辉石岩类捕虏体，主要由透辉石、富钛韭闪石、高Ｔｉ金云母、磷灰石及钛铁矿组成。捕虏体发育三联晶、碎裂边、扭折变形等固相线下变形变质结构，与正常地幔尖晶石二辉橄榄岩成分相比，捕虏体富ＴｉＯ２、Ｆｅ２Ｏ３、ＣａＯ、Ｎａ２Ｏ、Ｋ２Ｏ，贫ＭｇＯ；其稀土元素具富集特征，尤其富集ＬＲＥＥ；微量元素配分型式显示富亲石不相容元素的特征。岩相学、矿物学及岩石化学特征表明，该类捕虏体为交代地幔捕虏体，它代表了北大巴山早古生代裂谷作用时期的异常地幔。交代营力可能源于地幔热柱的上升，在地幔深处可能以熔体交代作用为主，往上逐渐以流体交代作用为主  相似文献   

吉林伊通幔源包体的微量元素组成及其成因岩石学意义   总被引：7，自引：0，他引：7  

徐义刚 Menz.  MA 《岩石学报》1997,13(1):14-26

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下地壳麻粒岩包体研究进展及其意义     

张海祖  张宏飞 《华北地质》2001,24(4):247-256

产于火山岩中的下地壳麻粒岩包体是人们窥视深部地壳的一个窗口 ,现已成为人们探索大陆下地壳物质组成和演化最直接的研究对象。下地壳岩石包体一般具有麻粒岩相矿物组合 ,主体由镁铁质麻粒岩组成 ,以出现紫苏辉石矿物为标志 ,下地壳包体的平衡温度为 70 0～10 4 0℃ ,平衡压力在 0 .8～ 1.4GPa之间。在绝大多数地区 ,基性下地壳包体占优势 ,其共同特征是低SiO2 、高CaO和Mg# ,过渡族元素和不相容元素含量变化很大 ,不同构造背景和不同岩石类型的包体同位素成分也有差异 ,全球各大陆下地壳包体Nd、Pb同位素组成分布具有“块体效应”特征。利用出露于地表的下地壳麻粒岩包体可以探讨下地壳物质组成和成分 ,建立下地壳物性剖面和岩石圈模型 ,并可作为幔源岩浆底侵作用的重要判据之一。世界范围内下地壳麻粒岩包体研究表明 ,在探讨下地壳的组成特点上 ,由火山岩中麻粒岩包体和出露的麻粒岩地体两类岩石样品所获得的下地壳组成特点存在比较大的差异 ,前者较后者反映的下地壳组成更偏基性。下地壳包体的类型与成因对揭示大陆地壳的增生、演化方式以及壳—幔交换作用具有重要的指示意义  相似文献