塔里木盆地巴楚小海子二叠纪超基性脉岩的地球化学特征及其成因探讨     

杨树锋 余星陈汉林  厉子龙王清华 罗俊成 《岩石学报》2007,23(5):1087-1096

巴楚小海子水库南闸附近出露的橄榄二辉岩岩墙SiO_2含量平均为42%,Na_2O K_2O<1%,Mg~#=0.67～0.69,Fe_2O_3为16.29%～19.37%,具高镁富铁型原生玄武质岩浆的地球化学特征。橄榄二辉岩稀土元素标准化值呈LREE富集的右倾平滑曲线,轻重稀土元素分馏明显,微量元素配分曲线呈大隆起型,指示板内拉斑玄武岩系列的地球化学特征。Eu异常很不明显,可能由于斜长石的弱分离结晶作用所致,Sr、K等大离子亲石元素的相对亏损缘于热液蚀变和流体交代。该超基性脉岩与其附近发现的基性脉岩具有相同的产状,相似的地球化学特征,指示它们来源于同一岩浆源区,并在相同的构造环境下产出。其Th/Ta、Nb/U、Nb/La和Zr/Ba等微量元素比值均显示岩浆源区可能为亏损的软流圈地幔,岩浆的侵位根源于深部地幔物质上涌,以及二叠纪板内区域拉张环境的有利配合。  相似文献   

华北龙岗第四纪玄武岩：岩石成因和源区性质   总被引：1，自引：1，他引：1  

闫峻赵建新  刘海泉 《岩石学报》2007,23(6):1413-1422

华北克拉通东北缘龙岗第四纪玄武岩的地球化学研究为大陆碱性玄武岩的成因以及源区的性质提供了重要的依据。龙岗第四纪玄武岩为碱性玄武岩,具有类似 OIB 的 REE 和微量元素分配特征。岩石的 Sr-Nd 同位素轻度亏损(~(87)Sr/~(86)Sr=0.7044～0.7048,ε_(Nd)=0.6～2.1),具有 Dupal 异常的高放射性成因 Pb 同位素组成(~(206)Pb/~(204)Pb:17.734～18.194,~(207)Pb/~(204)Pb=15.553～15.594,~(208)Pb/~(204)Pb=38.322～38.707)。这种地球化学特征指示了原始岩浆起源于<70km 深度的地幔,并经历了一定程度的橄榄岩、单斜辉石和钛-铁氧化物的结晶分异。岩浆源区中以来类似 MORB 软流圈物质的熔体为主,另外有少量来自 EM Ⅰ性质的富集岩石圈地幔以及俯冲流体/熔体的物质贡献,显示了深部岩石圈-软流圈一定程度的相互作用以及太平洋板块俯冲的影响。岩浆源区多种端元组分的存在表明该地区岩石圈的减薄/置换受到多种因素的影响。  相似文献   

Crust–primitive magma interaction beneath neovolcanic rift zone of Iceland recorded in gabbro xenoliths from Midfell, SW Iceland     

Andrey A. Gurenko  Alexander V. Sobolev 《Contributions to Mineralogy and Petrology》2006,151(5):495-520

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龙岗金垅顶子近代活动火山的岩石学与地球化学   总被引：13，自引：4，他引：9  

樊祺诚  刘若新 《岩石学报》1999,15(4):584-589

距今１６００ 年前喷发的金龙顶子火山是龙岗火山群中一座最年轻的近代活动火山, 它的喷发物包括金龙顶子火山锥体 （海拔９９９．４ｍ ）、熔岩流及其广布的火山碎屑席 （四海火山渣层）。金龙顶子火山岩为单一的粗面玄武岩, 有着极为相似的ＲＥＥ和不相容元素分布模式, ８７Ｓｒ／８６Ｓｒ和１４３Ｎｄ／１４４Ｎｄ 分别变化于０．７０４８４６～０．７０４９２１ 和０．５１２６１９～０．０．５１２６４６, 这反映了它们直接来自地幔源区, 岩浆上升过程极少演化和壳源混染, 具有较为原始的岩浆特点。年轻火山岩中的幔源捕虏体提供了该区存在相对低温 （～９００℃） 含水的地幔。  相似文献   

分形结构因子及其在地质学上的应用   总被引：8，自引：0，他引：8  

沈步明 《岩石学报》1993,9(3):267-276

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Partial melting and decompression of the Thor-Odin dome, Shuswap metamorphic core complex, Canadian Cordillera   总被引：5，自引：0，他引：5  

Britt H. Norlander  Donna L. Whitney  Christian Teyssier  Olivier Vanderhaeghe 《Lithos》2002,61(3-4):103-125

The Thor-Odin dome region of the Shuswap metamorphic core complex, British Columbia, contains migmatitic rocks exhumed from the deep mid-crust of the Cordilleran orogen. Extensive partial melting occurred during decompression of the structurally deepest rocks, and this decompression path is particularly well recorded by mafic boudins of silica-undersaturated, aluminous rocks. These mafic boudins contain the high-temperature assemblages gedrite+cordierite+spinel+corundum+kyanite/sillimanite±sapphirine±högbomite and gedrite+cordierite+spinel+corundum+kyanite/sillimanite+garnet±staurolite (relict)±anorthite. The boudins are interlayered with migmatitic metapelitic gneiss and orthogneiss in this region.

The mineral assemblages and reaction textures in these rocks record decompression from the kyanite zone (P>8–10 kbar) to the sillimanite–cordierite zone (P<5 kbar) at T750 °C, with maximum recorded temperatures of 800 °C. Evidence for high-temperature decompression includes the partial replacement of garnet by cordierite, the partial to complete replacement of kyanite by corundum+cordierite+spinel (hercynite)±sapphirine±högbomite symplectite, and the replacement of some kyanite grains by sillimanite. Kyanite partially replaced by sillimanite, and sillimanite with coronas of cordierite±spinel are also observed in the associated metapelitic rocks.

Partial melt from the surrounding migmatitic gneisses has invaded the mafic boudins. Cordierite reaction rims occur where minerals in the boudins interacted with leucocratic melt. When combined with existing structural and geochronologic data from migmatites and leucogranites in the region, these petrologic constraints suggest that high-temperature decompression was coeval with partial melting in the Thor-Odin dome. These data are used to evaluate the relationship between partial melting of the mid-crust and localized exhumation of deep, hot rocks by extensional and diapiric processes.  相似文献   

《矿物岩石》载文被引情况分析研究     

蔡濂  王洪峰 《矿物岩石》2002,22(3):101-102

依据《中国科技论文统计与引文分析数据库》（CSTPC），采用文献计量的方法对《矿物岩石》载文被CSTPC来源期刊的引用情况进行统计分析及评价；其所载文献质量较高，作者群的地域分布较广，已形成具有自己风格和特色且相对稳定的研究体系；在中国地质学界有一定影响，不仅是我国地质科学研究领域最重要的信息源之一。也是我国主要的地质学核心期刊。  相似文献   

扬子地台西缘钾质煌斑岩类的岩石学研究   总被引：3，自引：0，他引：3  

舒小辛 《岩石学报》1994,10(3):248-260

扬子地台西缘钾质煌麻岩的矿物组合中缺少钾碱镁门石、柱红石等富钾贫铝矿物，其辉石和白榴石富Ａｌ２Ｏ３，金云母贫ＴｉＯ２，透长石的Ｎａ２Ｏ含量高。全岩Ａｌ２Ｏ３高，Ｋ２Ｏ／Ａｌ２Ｏ３（＜０．７）低，（Ｇｄ／Ｙｂ）Ｎ低。岩体中含有二辉橄榄岩包体、镁铝榴石捕虏体晶。这些特点表明其岩浆源区的亏损程度低。此外，钾质煌斑岩明显亏损Ｎｂ、Ｔｉ，可能是与其源区经受过板块边缘活动影响有关。  相似文献   

Crystal retention,fractionation and crustal assimilation in a convecting magma chamber,Nisyros Volcano,Greece   总被引：2，自引：0，他引：2  

L. Francalanci  J. C. Varekamp  G. Vougioukalakis  M. J. Delant  F. Innocenti  P. Manetti 《Bulletin of Volcanology》1995,56(8):601-620

Nisyros island is a calc-alkaline volcano, built up during the last 100 ka. The first cycle of its subaerial history includes the cone-building activity with three phases, each characterized by a similar sequence: (1) effusive and explosive activity fed by basaltic andesitic and andesitic magmas; and (2) effusive andextrusive activity fed by dacitic and rhyolitic magmas. The second eruptive cycle includes the caldera-forming explosive activity with two phases, each consisting of the sequence: (1) rhyolitic phreatomagmatic eruptions triggering a central caldera collapse; and (2) extrusion of dacitic-rhyolitic domes and lava flows. The rocks of this cycle are characteized by the presence of mafic enclaves with different petrographic and chemical features which testify to mixing-mingling processes between variously evolved magmas. Jumps in the degree of evolution are present in the stratigraphic series, accompanied by changes in the porphyritic index. This index ranges from 60% to about 5% and correlates with several teochemical parameters, including a negative correlation with Sr isotope ratios (0.703384–0.705120). The latter increase from basaltic andesites to intermediate rocks, but then slightly decrease in the most evolved volcanic rocks. The petrographic, geochemical and isotopic characteristics can be largely explained by processes occurring in a convecting, crystallizing and assimilating magma chamber, where crystal sorting, retention, resorption and accumulation take place. A group of crystal-rich basaltic andesites with high Sr and compatible element contents and low incompatible elements and Sr isotope ratios probably resulted from the accumulation of plagioclase and pyroxene in an andesitic liquid. Re-entrainment of plagioclase crystals in the crystallizing magma may have been responsible for the lower ⁸⁷Sr/⁸⁶Sr in the most evolved rocks. The gaps in the degree of evolution with time are interpreted as due to liquid segregation from a crystal mush once critical crystallinity was reached. At that stage convection halted, and a less dense, less porphyritic, more evolved magma separated from a denser crystal-rich magma portion. The differences in incompatible element enrichment of pre-and post-caldera dacites and the chemical variation in the post-caldera dome sequence are the result of hybridization of post-caldera dome magmas with more mafic magmas, as represented by the enclave compositions. The occurrence of the quenched, more mafic magmas in the two post-caldera units suggests that renewed intrusion of mafic magma took place after each collapse event.  相似文献   

新疆阿拉套山花岗岩带的主要特征及形成构造环境   总被引：2，自引：0，他引：2  

周泰禧  陈江峰 《岩石学报》1995,11(4):386-396

阿拉套山花岗岩带产出于巩乃斯板块东北缘，岩带的岩石组合、化学成分、同位素组成表现出由东北向西南的系统变化，随离俯冲带距离的增大，古老地壳物质的贡献愈显著。构造环境判别表明早期花岗闪长岩－二长花岗岩组合产出于岩浆弧环境，与消减作用直接有关，晚期二长花岗岩－碱长花岗岩组合为造山后花岗岩，产出于张性环境，其形成标志着造山作用的结束。  相似文献