【作者】 叶俊；

【导师】 李乃胜； 石学法；

【作者基本信息】 中国科学院研究生院（海洋研究所） ， 海洋地质学， 2012， 博士

【摘要】 本文选择西南印度洋脊49.6oE热液区为研究区域，对该热液区产出的矿石样品开展了矿物学、地球化学等方面研究，以了解超慢速扩张脊热液多金属硫化物成矿过程及成矿机制。研究显示，区内矿石存在硫化物和氧化物两种矿石自然类型。根据矿物组合，硫化物矿石可进一步划分出两种类型：其一为富Zn硫化物矿石，其二为富Fe硫化物矿石。富Zn硫化物矿石矿物组合主要为闪锌矿-黄铁矿-黄铜矿，闪锌矿集合体内普遍发育溶蚀孔洞构造及同质增生边结构；富Fe硫化物矿石矿物组合主要为黄铁矿-白铁矿-等轴古巴矿，具典型的等轴古巴矿固溶体分解结构，指示高温沉淀特征。两种硫化物矿石的矿物组合与结构构造特征指示该热液区硫化物成矿至少经历了两个阶段。第一阶段为中-低温富Zn硫化物沉积成矿阶段，第二阶段为高温富Fe硫化物沉积成矿阶段，成矿温度由低到高的转化说明热液体系存在幕式排泄特征。富Zn硫化物中可见自然金矿物产出。根据自然金主要赋存于闪锌矿中相对高Fe区域的特点，推测Au在热液流体中主要以Au(HS)0形式迁移。Au-As、Au-Pb的关系进一步指示该区至少存在两幕热液活动叠加改造过程。硫化物矿石的铂族元素总量较其他典型热液区低，且其球粒陨石配分模式与玄武岩相似，均无明显Rh异常，可能指示铂族元素主要来自流体对基底岩石的淋滤，无明显岩浆热液物源的加入。S、Pb、Sr同位素研究显示，硫化物成矿物质主要来自热液流体对基底玄武岩的淋滤。结合区域地质背景资料，认为西南印度洋脊49.6oE热液区的热液活动可能受底部岩浆热源控制。更多还原

【Abstract】 To understand the hydrothermal mineralization along ultra-slow spreadingridges, the first discovered acitive hydrothermal field, Southwest Indian Ridge (SWIR)49.6oE field, was selected to be investigated. Mineralogical, geochemical, and isotopicmethods were carried out to identify the characteristic and precipitate mechanism ofsulfides and oxides from this field. The results show that the sulfides in this field canbe classified into two distinct types according to the mineral assemblages, which areZn-rich ore and Fe-rich ore. The Zn-rich type ore is dominated bysphalerite-pyrite-chalcopyrie assemblages and the Fe-rich type is bypyrite-marcasite-isocubanite. Two mineralization stages were identified by thetextures and chemistry of the sulfide ores. Stage I is associated with relatively lowtemperature Zn-rich sulfide assemblages and stage II is to higher ore-formingtemperature Fe-rich sulfides. The transform of temperature from lower to higherreflects that episode emissions of hydrothermal fluids are there in this field. The firstoccurrence of native gold in sulfide from ultra-slow spreading ridge was reported inthis study. Based on the association of gold and sphalerite iron content, transportmechanism of gold in the fluid was qualified as Au(HS)0. The reworking process inSWIR49.6oE hydrothermal field was documented by the relationship between Au andAs, Pb. The low content of PGE and no Rh anomaly indicate that the magmatic fluidinput into the hydrothermal system was negligible. The sulfur isotope and Pb-Srisotope reveal that the metals in sulfide were derived mainly from substrate rock.Combined with the geological setting of Southwest Indian Ridge, it is can be inferredthat the hydrothermal activity in SWIR49.6oE field is controlled by magma supply asother fast spreading East Pacific Rise and slow spreading Mid-Atlantic Ridges.更多还原