【作者】 李兵；

【导师】 石学法； 杨耀民；

【作者基本信息】 中国科学院研究生院（海洋研究所） ， 海洋地质， 2014， 博士

【摘要】 南大西洋中脊14.0°S热液区是由中国科学家发现的、位于南大西洋中脊-转换断层内角高地的热液区。本文对14.0°S热液区表层所采集到的岩石及热液产物进行了详细的矿物学和地球化学分析，同时结合海底观测及地球物理资料，深入研究了14.0°S热液区的热液成矿作用，目的在于进一步了解慢速洋中脊内角构造环境下热液活动及相应的多金属硫化物成矿规律。本文创新性成果及结论如下：1、南大西洋14.0°S离轴内角高地包括近轴岩浆型高地和远轴OCC高地，热液区发育在近轴火山型高地上，岩浆作用对其发育具有决定性作用，这是14.0°S热液区有别于北大西洋内角高地热液区最显著的特征。2、14.0°S热液区产出的多金属硫化物主要由铁硫化物（黄铁矿/白铁矿）和非晶质硅组成，部分富含黄铜矿，但闪锌矿/纤锌矿等锌硫化物较少。本区海底至少存在三期次的热液活动，其中第一期和第三期为非晶质硅沉淀阶段，第二期为硫化物沉淀阶段，多期性的热液活动可能与深部岩体热破裂事件有关。3、14.0°S热液区洋壳遭受构造破裂程度强烈，导致热液释放区三维空间范围大，热液上升流主要以弥散流形式上涌，所形成的堆积矿-网脉矿复合矿体垂向分带性弱。而顶部热液点相对于斜坡热液点，其释放区海底渗透性相对较好。4、14.0°S热液区的主要热源为洋壳深部岩浆侵入体结晶形成的高温岩体，成矿流体来源为下渗的海水，成矿物质来源为铁镁质围岩，火山高地下部掩埋的拆离断层和高地内高角度正断层是两类可能的控矿构造。更多还原

【Abstract】 The14.0°S hydrothermal field at South Mid-Atlantic Ridge (SMAR) is anhydrothermal field firstly found by Chinese scientists locating at the inside-cornerhigh of ridge-transform fault intersection SMAR. To understand the hydrothermalactivities further and the associated ore-forming regularities of polymetallic sulfidesunder the inside-corner high environment from a slow-spreading ridge, detailed studyof mineralogy and geochemistry on both rocks and hydrothermal products from thesurface of the14.0°S hydrothermal field have been carried out. Meanwhile, acomprehensive study on the hydrothermal mineralization was made with thecombination of seafloor observation and geophysical data. Innovative results andconclusions in this research are as follows:1. The SMAR14.0°S off-axis inside-corner high contains the near-axis volcanichigh and the abaxis oceanic core complex (OCC) high. While14.0°S hydrothermalvent field was located at the near-axis high, rather than the OCC structure, indicatingthat magmatic activities have conclusive effect on its development. This is the mostdistinctive feature from other hydrothermal vent fields at inside-corner high fromNorth mid-Atlantic ridge.2. The sulfide ores in14.0°S field are dominated by Pyrite-Marcasite-Amorphoussilica assemblages, several ores are enriched in chalcopyrite, but lack of zinc sulfideslike sphalerite/wurtzite etc. At least three stages of seafloor hydrothermal activitieswere identified in this field. The first and third stages were associated with amorphoussilica precipitations, while the second stage was associated with high temperaturesulfide precipitation. Multi-stages of hydrothermal activities are believed to becorrelated with the thermal cracking events of the deep rock bodies.3. The oceanic crust at14.0°S hydrothermal vent field suffered from strongtectonic cracking events, leading to the large3-dimensional spatial range ofhydrothermal release area. Hydrothermal upwellings are mainly diffusive flows andthe formed mound-stockwork complex thus shows weak vertical zonation. Comparingthe hydrothermal site1with that on the slop (site2), the former release area has a better seafloor permeability.4. The high temperature rock bodies due to the crystallization of the magmaticintrusions deep in the oceanic crust supplies the main heat source for the14.0°Shydrothermal field. While the ore-forming fluids and material is originated fromseawater and mafic wall-rock, respectively. We suggested that the overlaiddetachment fault under the volcanic highs and the high-angle normal faults in thehighs are probably two controlling-ore structures.更多还原