Metasomatic origin of garnet xenocrysts from the V. Grib kimberlite pipe,Arkhangelsk region,NW Russia     

E.V. Shchukina  A.M. Agashev  N.P. Pokhilenko 《地学前缘(英文版)》2017,8(4):641-651

This paper presents new major and trace element data from 150 garnet xenocrysts from the V. Grib kimberlite pipe located in the central part of the Arkhangelsk diamondiferous province (ADP). Based on the concentrations of Cr₂O₃, CaO, TiO₂ and rare earth elements (REE) the garnets were divided into seven groups: (1) lherzolitic “depleted” garnets (“Lz 1”), (2) lherzolitic garnets with normal REE patterns (“Lz 2”), (3) lherzolitic garnets with weakly sinusoidal REE patterns (“Lz 3”), (4) lherzolitic garnets with strongly sinusoidal REE patterns (“Lz 4”), (5) harzburgitic garnets with sinusoidal REE patterns (“Hz”), (6) wehrlitic garnets with weakly sinusoidal REE patterns (“W”), (7) garnets of megacryst paragenesis with normal REE patterns (“Meg”). Detailed mineralogical and geochemical garnet studies and modeling results suggest several stages of mantle metasomatism influenced by carbonatite and silicate melts. Carbonatitic metasomatism at the first stage resulted in refertilization of the lithospheric mantle, which is evidenced by a nearly vertical CaO-Cr₂O₃ trend from harzburgitic (“Hz”) to lherzolitic (“Lz 4”) garnet composition. Harzburgitic garnets (“Hz”) have probably been formed by interactions between carbonatite melts and exsolved garnets in high-degree melt extraction residues. At the second stage of metasomatism, garnets with weakly sinusoidal REE patterns (“Lz 3”, “W”) were affected by a silicate melt possessing a REE composition similar to that of ADP alkaline mica-poor picrites. At the last stage, the garnets interacted with basaltic melts, which resulted in the decrease CaO-Cr₂O₃ trend of “Lz 2” garnet composition. Cr-poor garnets of megacryst paragenesis (“Meg”) could crystallize directly from the silicate melt which has a REE composition close to that of ADP alkaline mica-poor picrites. P-T estimates of the garnet xenocrysts indicate that the interval of ～60–110 km of the lithospheric mantle beneath the V. Grib pipe was predominantly affected by the silicate melts, whereas the lithospheric mantle deeper than 150 km was influenced by the carbonatite melts.  相似文献   

华北克拉通岩石圈地幔的锂同位素特征与熔体改造作用     

汤艳杰  张宏福 《矿物岩石地球化学通报》2019,(2):217-223,444-445

华北克拉通是显生宙以来全球古老克拉通破坏最为剧烈的地区。华北克拉通破坏及其相关的科学问题引起了国内外地质学家的广泛关注。有关华北克拉通破坏的研究已取得了许多重要进展,使我们认识到其破坏不仅表现为岩石圈厚度的剧烈减薄,更重要的是岩石圈地幔的物质组成与性质发生了巨大转变,即从古生代克拉通型转变为新生代大洋型。本文在综述华北地幔捕虏体锂同位素地球化学特征的基础上,进一步揭示了华北岩石圈地幔高度不均一的组成特征,以及不同来源的熔体对岩石圈地幔的改造作用,为深入认识华北岩石圈地幔的转变过程提供进一步的制约。  相似文献   

安徽铜陵中生代侵入岩及其岩石包体中的硫化物-氧化物包裹体研究   总被引：4，自引：0，他引：4  

杜杨松  秦新龙  曹毅 《矿床地质》2010,29(1):71-84

安徽铜陵地区中生代岩浆活动频繁,形成了一系列与铜、金多金属成矿作用关系密切的中酸性侵入岩。在这些侵入岩中分布有大量的镁铁质团块、堆积晶和微粒闪长质包体。在这些侵入岩及其岩石包体中观察到了一定数量的硫化物-氧化物包裹体。文章对老庙基、小铜官山和小陶家岩体及其岩石包体中的硫化物-氧化物包裹体进行了详细的岩相学观察和电子探针分析。观察和分析结果显示,镁铁质团块中硫化物包裹体内的矿物主要有磁黄铁矿、黄铜矿、单硫化物固溶体和镍黄铁矿,这些硫化物相(黄铜矿除外)中的Ni、Cu平均含量(wB,下同)分别为6.91%和0.44%;微粒闪长质包体和寄主岩中硫化物包裹体内的矿物主要为磁黄铁矿和黄铜矿,这些硫化物相(黄铜矿除外)中的Ni、Cu平均含量分别为0.44%、0.07%(微粒闪长质包体)和0.09%、0.42%(寄主岩)。镁铁质团块、微粒闪长质包体和寄主岩中氧化物包裹体内的矿物分别为铬磁铁矿(Cr2O3平均含量为4.44%)、磁铁矿(Cr2O3平均含量为0.44%)和磁铁矿(Cr2O3平均含量为0.07%);散布的氧化物颗粒分别为铬磁铁矿(Cr2O3平均含量为6.58%)、磁铁矿+铬磁铁矿(Cr2O3平均含量为0.86%)...  相似文献   

吉林省伊通地区橄榄岩包体的同位素特征与岩石圈地幔时代   总被引：6，自引：2，他引：4  

周琴  吴福元  储著银  葛文春 《岩石学报》2010,26(4):1241-1264

吉林省伊通新生代火山群中大孤山所伴生的东小山火山含有丰富的地幔橄榄岩包体,详细的岩石学和矿物学工作显示,这些包体的主要岩石类型为尖晶石二辉橄榄岩,含有少量的方辉橄榄岩和异剥橄榄岩。包体的结构类型多样,包括粒状变晶结构、碎斑状结构、糜棱结构和筛状变晶结构。主量元素及矿物化学资料表明,这些地幔橄榄岩包体大都比较饱满,说明其所经历的部分熔融程度较低。微量元素显示,包体在形成以后经受过不同程度地幔交代作用的影响。矿物平衡温度计算结果表明包体的平衡温度为989～1142℃,来源深度约为40～70km。Sr-Nd-Hf同位素资料反映二辉橄榄岩包体具有亏损地幔的特征。Re-Os同位素资料显示上述岩石圈地幔的主体形成于显生宙期间,少量具有中元古代Re亏损年龄的样品所代表的古老地幔与本区上覆地壳成因无关,可能是软流圈中固有的较古老的大陆岩石圈地幔。  相似文献   

蓬莱新生代玄武岩中的单斜辉石巨晶及深源包体的矿物化学     

韩宗珠  盛兴土  赵广涛 《中国海洋大学学报(自然科学版)》1991,(1)

利用电子探针分析蓬莱新生代玄武岩中的单斜辉石巨晶及尖晶石二辉橄榄岩包体中的主要造岩矿物(单斜辉石、斜方辉石、橄榄石和尖晶石)的化学组成。利用单斜辉石地质温压计和二辉石地质温度计计算了尖晶石二辉橄榄岩包体的平衡温度和压力,计算表明它们来自于上地幔的不同深度,同时推测本区上地幔内存在化学组成的分带性。  相似文献   

广西北海涠洲岛第四纪晚期火山碎屑流中橄榄岩包体碎块的发现及其地质意义   总被引：1，自引：0，他引：1  

黄林培  李昌年 《岩石矿物学杂志》2007,26(4):321-328

广西北海涠洲岛是我国面积最大的第四纪火山岩海岛,岛内出露的最新一次火山喷发产物为碧玄质岩石,它覆盖于晚更新世湖光岩组(Q3h)层状凝灰岩地层之上。在该火山岩中发现有橄榄岩包体,罕见的是,包体是以火山角砾的形式见于碧玄质火山碎屑流之中,故应是被炸碎的包体碎块,而非原始态包体。这是迄今为止较为特殊的一种橄榄岩包体产状类型,其原始态包体的岩石类型可能为方辉橄榄岩和纯橄岩。岩石结构及探针数据均表明该橄榄岩包体来自岩石圈地幔。包体的温压估算结果为960～1040℃和1.3GPa,对应的稳定深度约40km。此外,由于包体来源深度远小于其寄主碧玄质火山岩浆的来源深度(大于99km),表明涠洲岛地区第四纪火山碎屑流中的橄榄岩包体是地幔柱来源的碧玄质岩浆在上升经过岩石圈地幔约40km深度时捕获的偶然包体,并在就位前经历过炸碎。  相似文献   

江西安远路迳金伯利质煌斑岩筒辉石巨晶和包体中辉石的氢氧同位素     

张保民  张晓黎  叶德隆 《地质科技情报》2007,26(1):19-22

利用离子探针和质谱技术分别分析测试了江西安远路迳金伯利质煌斑岩筒辉石巨晶和包体中辉石的氢氧同位素组成.结果显示,辉石的氢同位素δ(D)值从-83‰变化到-101‰,平均值为-91.6‰;氧同位素δ(18O)值由5.46‰变化到5.70‰,平均值为5.60‰.路迳辉石巨晶和包体中辉石的氢氧同位素组成均一,表明其来源于地幔,且其形成和演化过程中物理化学环境稳定,继承并保持了原始地幔的氢氧同位素组成.  相似文献   

Zircon geochronology and geochemistry of mafic xenoliths from Liaoning kimberlites:Track the early evolution of the lower crust,North China Craton   总被引：1，自引：0，他引：1  

ZHENG Jianping  YU Chunmei  LU Fengxiang & LI Huimin .Faculty of Earth Sciences  China University of Geosciences  Wuhan  China  .Tianjin Institute of Geology  Mineral Resources  Tianjin  China 《中国科学D辑(英文版)》2004,47(11):961-972

Since the formation of the primal nucleus at 3.8Ga[1], the North China had underwent the multi-cycle geologic processes such as arc accretion[2—4] andrift[5—7], and finally accomplished the craton[8] aroundat 1.8 Ga[2,3,9]. Paleozoic Fuxian kimberlites (LiaoningProvince) contain not only abundant peridotitic butalso mafic xenoliths. The investigation on peridotiticxenoliths indicted that the North China Craton hadcold and thick lithospheric root in the middle Ordovi-cian. The deep part o…  相似文献   

中国东部地幔岩中的钨含量及其意义   总被引：6，自引：1，他引：6  

赫英  岳可芬  董振信  张战军  刘民武 《地球化学》2003,32(6):561-565

分析了56件中国东部地幔岩包体及其寄主岩石中的钨含量。结果表明，地幔岩包体和寄主玄武岩中的钨含量分别在0．1～1．0μg／g和0．1～2．5μg／g之间。后者一般高于前者且明显不均一，反映钨是不相容元素，在部分熔融过程中倾向于富集在熔体中，而主要源于软流圈地幔低程度熔融的熔体在上升过程中发生了不同程度的岩石圈．软流圈或地壳．地幔相互作用。地幔岩包体钨平均含量接近或仅略高于上地幔钨的丰度，而寄主玄武岩钨平均含量与世界基性岩钨的丰度非常一致，说明我国地幔中钨的丰度与世界其他地区相比并无明显不同，反映钨矿集中区的形成和分布与地幔中钨的原始分布关系不大，我国钨矿集中区的形成可能主要与地壳演化有关。  相似文献   

A Re–Os isotope and PGE study of kimberlite-derived peridotite xenoliths from Somerset Island and a comparison to the Slave and Kaapvaal cratons     

Gordon J. Irvine  D. Graham Pearson  B. A. Kjarsgaard  R. W. Carlson  M. G. Kopylova  G. Dreibus 《Lithos》2003,71(2-4):461-488

The concentrations of platinum-group elements (PGE; Os, Ir, Ru, Pd and Pt) and Re, and the Os isotopic compositions were determined for 33 lithospheric mantle peridotite xenoliths from the Somerset Island kimberlite field. The Os isotopic compositions are exclusively less radiogenic than estimates of bulk-earth (¹⁸⁷Os/¹⁸⁸Os as low as 0.1084) and require a long-term evolution in a low Re–Os environment. Re depletion model ages (T_RD) indicate that the cratonic lithosphere of Somerset Island stabilised by at least 2.8 Ga, i.e. in the Neoarchean and survived into the Mesozoic to be sampled by Cretaceous kimberlite magmatism. An Archean origin also is supported by thermobarometry (Archean lithospheric keels are characterised by >150 km thick lithosphere), modal mineralogy and mineral chemistry observations. The oldest ages recorded in the lithospheric mantle beneath Somerset Island are younger than the Mesoarchean (>3 Ga) ages recorded in the Slave craton lithospheric mantle to the southwest [Irvine, G.J., et al., 1999. Age of the lithospheric mantle beneath and around the Slave craton: a Rhenium–Osmium isotopic study of peridotite xenoliths from the Jericho and Somerset Island kimberlites. Ninth Annual V.M. Goldschmidt Conf., LPI Cont., 971: 134–135; Irvine, G.J., et al., 2001. The age of two cratons: a PGE and Os-Isotopic study of peridotite xenoliths from the Jericho kimberlite (Slave craton) and the Somerset Island kimberlite field (Churchill Province). The Slave–Kaapvaal Workshop, Merrickville, Ontario, Canada]. Younger, Paleoproterozoic, T_RD model ages for Somerset Island samples are generally interpreted as the result of open system behaviour during metasomatic and/or magmatic processes, with possibly the addition of new lithospheric material during tectono-thermal events related to the Taltson–Thelon orogen. PGE patterns highly depleted in Pt and Pd generally correspond to older Archean T_RD model ages indicating closed system behaviour since the time of initial melt extraction. Younger Proterozoic T_RD model ages generally correspond to more complex PGE patterns, indicating open system behaviour with possible sulfide or melt addition. There is no correlation between the age of the lithosphere and depth, at Somerset Island.  相似文献