【作者】 罗茂澄；

【导师】 毛景文； 唐菊兴；

【作者基本信息】 中国地质大学(北京) ， 矿物学、岩石学、矿床学， 2012， 硕士

【摘要】 邦铺斑岩钼（铜）矿床位于冈底斯斑岩铜矿带东段，产于冈底斯-念青唐古拉复合火山岩浆弧南缘。本文通过流体包裹体、熔融包裹体、Hf同位素和He-Ar同位素研究，确定了矿床主要蚀变及矿化类型，约束了岩浆出溶流体的物理化学条件，查明了成矿流体演化过程以及成矿物质迁移沉淀机制。研究表明，邦铺钼（铜）矿床岩浆源区主要来源于年轻地幔的组分，但在岩浆侵位过程遭受了古老地壳物质的混染。岩浆演化温度区间为850℃¹223℃，岩浆房和浅成侵位的斑岩均发生了流体出溶，石英斑晶中B20H包裹体与结晶质熔融包裹体共存，是斑岩体出溶流体的地质记录。斑岩出溶流体的压力为150²00Mpa，深度为5.6⁷.4km。根据蚀变矿物特征，矿床的围岩蚀变有4种类型：钾硅酸盐化、绢云母化、青磐岩化和粘土化。根据矿石的物质成分、矿物组合、脉体之间穿切关系的不同，整个矿床的形成可划分为3个阶段：成矿前阶段（Ⅰ）、主成矿阶段（Ⅱ）以及成矿后阶段（Ⅲ），主成矿阶段又可进一步细分为钼矿化（Ⅱ₁）、铜矿化（Ⅱ₂）两个亚阶段。在此基础上详细识别了10种不同脉体。根据气液充填度的不同，矿床流体包裹体可分为5类：B15、B20H、B35、B60和B80（“B”代表气泡，数字表示平均气相充填度，“H”指盐类子晶）。流体包裹体研究表明，邦铺矿床成矿温度为240℃⁴19℃，成矿压力为38¹16MPa，成矿深度为3.1⁴.3km。钼沉淀主要在Ⅱ₁阶段，与钾硅酸盐化、绢云母化关系密切，相关脉体为辉钼矿脉和石英-辉钼矿脉，脉体中包裹体以B20H、B35为主，形成温度240℃⁴05℃，压力38⁸5Mpa；铜沉淀主要在Ⅱ₂阶段，与硅化、青磐岩化关系紧密，相关脉体为石英-黄铜矿±黄铁矿脉和黄铜矿脉，脉体中包裹体以B60、B80为主，形成温度293℃⁴19℃，压力32⁸4Mpa。邦铺矿床成矿流体为主要为NaCl-H₂O体系，主要来源于地壳，但同时有地幔流体的参与，缺乏大气水的影响。矿床钼、铜都来源于岩浆，压力波动和pH值降低是钼沉淀的主导因素，压力波动和还原硫含量增加共同导致了铜的沉淀。邦铺斑岩钼（铜）矿床是印-亚大陆碰撞过程中伸展背景下成矿大爆发的产物，许多地质特征与典型斑岩铜矿相似，但是金属沉淀与岩浆的关系更为密切。更多还原

【Abstract】 The porphyry Mo （Cu） deposit at Bangpu, locating in the east section of Gangdese,Tibet, belongs to Gangdese-Nyainqentanglha compound volcanic magmatic arc. Withstudies on fluid and melt inclusions, Hf and He-Ar isotope compositions, this paperreports types of alteration and mineralization, the physical and chemical environmentfor magmatic exsolution, the fluid evolution history as well as the mechanism ofmetal transportation and precipitation.Lu-Hf isotope analysis of zircon grains from monzogranite porphyry and biotitemonzonitic granite suggests that their parental magmas were mainly derived from ayoung mantle and partly mixed with old continental crust rock during evolution. Byusing melt inclusions microthermometry we unravel the evolution of magmaticsystem happened from850℃to1223℃and fluid exsolution occurred at bothmagmatic chamber and hypergene emplacement porphyry. Coexistence of B20Hinclusions and silicate melt inclusions provides robust evidence of this process atpressure between150and200Mpa, corresponding to depths between5.6and7.4km.Bangpu deposit displays a consistent alteration-mineralization pattern that comprises,centrally from the bottom upward, of potassic-silicic, sericitic, propylitic andadvanced argillic. According to the veins types and crosscutting relationships, themineralization at Bangpu can be divided into three stages: Pre-stage （Ⅰ）, main-stage（Ⅱ） and post-stage （Ⅲ）. Main-stage needs further subdivision as Mo mineralizationstage （Ⅱ₁） and Cu mineralization stage （Ⅱ₂）. Fluid inclusions at Bangpu can bedistinguished as types B15, B20H, B35, B60and B80based on the phases present atroom temperature （The letter “B” denotes “bubble”, and the number indicates theaverage volume percent occupied by the bubble in inclusions of that type. The letter“H” refers to the presence of halite as a daughter mineral）. Fluid inclusionsmicrothermometry analysis gave the entire temperatures of mineralization rangingfrom240℃to419℃and pressure from38to116MPa, corresponding to depths from3.1and4.3km. B20H and B35inclusions dominate in Ⅱ₁stage with wide range ofhomogenization temperatures （240℃⁴05℃） and pressure from38to85Mpa. They formed molybdenum veins and quartz-molybdenum veins with potassic-silicic andsericitic alteration. In Ⅱ₂stage, fluid inclusions are mainly B60and B80types withhomogenization temperatures from293℃to419℃and pressure from32to84Mpa.They formed quartz-chalcopyrite±pyrite veins and chalcopyrite veins with silicic andpropylitic alteration.We conclude that the CO₂-bearing, aqueous fluids at Bangpu are consist of crust andmantle fluids with the former dominant, and lack of meteoric water involvementduring the whole mineralization. Isotope studies indicate metals at Bangpu theirmagmatic source. Pressure fluctuations, low pH and high S-content were probably themain driving force for Mo （Cu） sulfide deposition.The porphyry Mo （Cu） deposit at Bangpu, consequence of mineralization explosionduring the extension environment after India-Asia continental collision, shares manycommons with porphyry Cu deposit but has a closer relationship between magma andmetals precipitation.更多还原