【作者】 曹红；

【导师】 曹志敏；

【作者基本信息】 中国海洋大学 ， 地球化学， 2010， 硕士

【摘要】 本文以西南印度洋中脊(SWIR)不同区域玄武岩和热液沉积样品为研究对象,通过高精度ICP-AES/MS、X射线衍射、电子显微镜等实验测试手段,对样品进行矿物学、岩石学、地球化学特征进行研究,以此探讨西南印度洋中脊热液成矿作用、物质来源等科学问题,为海底热液矿床的寻找提供理论依据。本次研究得出以下几个方面成果：研究区玄武岩微量元素比值显示出正常洋中脊玄武岩(N-MORB)的性质,但又不同于典型的N-MORB,同时包括"MORB"型岩浆和洋岛岩浆两种成分。玄武岩的蛛网图配分曲线反映了亏损地幔源区玄武岩的地球化学特性。大离子亲石元素K、Rb和Ba轻微富集,Ba有显著的正异常,Sr显示负异常,并存在Nb和部分Ti的亏损,指示本区玄武岩形成过程中可能遭受了陆源物质的混染。稀土元素表现出LREE相对富集、HREE亏损的REE配分模式,在La-La/Sm变异图上,La/Sm与La同步增加,表明SWIR玄武岩岩浆岩石主要受部分熔融作用控制。取自69.59°E附近热液喷溢区的硫化物(AIR1和AIR2)为坍塌的黑烟囱硫化物。AIR1主要由黄铁矿、白铁矿和黄铜矿组成,属中-高温矿物组合,相对富集Co和Ni,表明黄铜矿是在高温下(>300℃)沉淀形成的。AIR2主要由黄铁矿、白铁矿和石膏组成,反映了一种中-低温矿物组合。49.64°E附近的硫化物氧化物ISUl由纤铁矿、黄铜矿以及少量黄铁矿和白铁矿组成。ISU2取自50.46°E附近,为蚀变橄榄岩,由富水镁硼石、利蛇纹石、以及锰的氧化物和铁的矾类矿物组成。热液白烟囱ISU4和ISU5取自51°E附近,主要由方解石组成,其热液流体温度为中-低温。热液硫化物Cu和Fe之间显著的正相关性反映了矿物组合关系；As、Sr和Ag元素之间的相关系数均大于0.85,说明它们在热液成矿作用过程中经历了相似的地球化学过程；Pb和Zn各自决定着Au和Ag的含量；Ag、As和Pb,它们之间有较高的相关性,可能表明低温再活化作用。热液硫化物的稀土元素准化配分曲线显示出明显的正Eu异常和LREE富集,其配分模式主要继承了热液流体中稀土元素的特性。热液白烟囱稀土元素含量较高,LREE富集,明显的负Eu异常可能表明其相对还原的成矿环境。更多还原

【Abstract】 The basalts and hydrothermal deposits samples we study are recovered from the different regions of the Southwest Indian Ridge (SWIR).We get the mineralogy、Petrology and geochemistry characteristics by high performance ICP -AES/MS、X-Ray Diffraction and Electronic Microscope, to discuss hydrothermal mineralization、material sources and other scientific problems and get the theory for exploring the submarine hydrothermal deposits. We get the results as following:Trace element ratios of basalts showing the similar characteristics to the Normal Mid-Ocean Ridge Basalt (N-MORB), but different from the typical N-MORB, while including two components:"MORB"-type magma and Ocean Island magma. The spider diagram shows the depleted-mantle magma source. Slight rich in LILE(K, Rb, and Ba), poor in Nb and parts of Ti, Ba significant positive anomalies, Sr shows negative anomalies, which might indicate the contamination of terrestrial. The REE shows the relative enrichment of LREE to HREE. La/Sm and La simultaneous increase, indicating that the basalt mainly control by partial melting.AIR1 and AIR2 are the collapsed black chimneys sulfide, near the 69.59°E. AIR1 is middle-high temperature mineral assemblages, dominated with pyrite, marcasite and chalcopyrite. Relative enrichment of Co and Ni, indicating that chalcopyrite precipitate at a high temperature (> 300℃). AIR2 is medium-low temperature mineral assemblages, dominated with pyrite, marcasite and gypsum. ISU1 is the sulfide oxides, mainly consist of lepidocrocite、chalcopyrite and pyrite, sampling from the 49.64°E. ISU2 is birbirite, near 50.46°E, mainly consist of kurnakovite、lizardite、manganese oxide and iron alum minerals. Hydrothermal white chimneies ISU4 and ISU5 from 51°E around, mainly composed of calcite, the temperature of hydrothermal fluids is middle-low temperature.Cu and Fe of the sulfides showing significant positive correlation, reflects the relationship of mineral assemblages; The correlations between As、Sr and Ag were higher than 0.85, indicating that they have undergoing the similar geochemical processes in hydrothermal mineralization; Pb and Zn pespectively determines the content of Au and Ag; there are significant positive correlations between Ag、As and Pb, which might indicate remobilization under lower temperature conditions.The sulfide samples are characterized by significant positive Eu anomaliesand the enrichment of LREE relative to HREE, inheriting the characteristics of hydrothermal fluids. The REE contents are high in white chimneys rich in calcile, chondrite-normalized pattern shows LREE enrichment and negative Eu anomalies may indicate the relative reductive environment.更多还原