【作者】 连玉；

【导师】 徐文艺；

【作者基本信息】 中国地质科学院 ， 地球化学， 2008， 硕士

【摘要】 本论文对冈底斯成矿带主碰撞期形成的雄村似斑岩—浅成低温热液复合型铜金矿床和后碰撞伸展期形成的甲马矽卡岩型铜多金属矿床、南木斑岩型铜钼矿床三个典型矿床开展了系统的流体包裹体岩相学、显微测温、Raman和SR-XRF原位分析研究。通过包裹体研究,结合各矿床矿物学和蚀变矿化特征、以及氢、氧、氦、硫、铅同位素示踪,得出以下认识:（1）三个矿床成矿流体演化过程中均出现了沸腾或相分离现象,这一现象与成矿体系持续压力释放有关;三矿床的矿体定位均受构造破碎带控制,这为成矿体系的压力释放创造了条件。（2）三矿床的成矿深度均较浅,甲马约1.5km,南木约1km,雄村最浅;这与三矿床均有岩浆水参与,但甲马最靠近岩浆水,而雄村岩浆水比例最小相一致。（3）三矿床中,流体包裹体中的Cu含量南木最高,而南木的成矿规模却最小,这与南木成矿体系降温速率最小有关。（4）三矿床成矿流体体系中均含有大量气体,与雄村和甲马不同,南木气体组成主要是CO₂,而且包裹体中存在赤铁矿、磁铁矿和针铁矿子矿物,表明南木成矿流体f_o2最高。（5）三矿床的形成均与酸性蚀变密切相关,如绢英岩化和绿泥石化;酸性蚀变消耗H⁺,使流体呈近中性或偏碱性,对于维系成矿流体中高HS^-浓度,进而保障硫化物沉淀成矿非常关键。（6）根据冈底斯成矿带中的三个典型矿床的研究,对于其中的Cu成矿地质地球化学机制可以归纳为:深源流体为铜矿的形成提供了充足的物质来源;构造破碎带导致压力释放,进而导致相分离,使Cu进一步在高盐度流体中浓集,同时破碎带也铜矿体的定位准备了空间;相对快的降温速率是导致Cu淀积成矿的一个重要机制,低的f_o2以及近中性或偏碱性的流体环境,有利于Cu以硫化物形式大量淀积。成矿过程是上述诸多因素协同控制的过程,同时也是一个熵减的耗散过程,因此还需要持续稳定的热驱动和体系相对开放的成矿环境。（7）南木和甲马矿床在物质来源上均与相关幔壳混源岩体存在亲缘性,成矿流体与成矿斑岩岩浆可能共同起源于深部,二者平行演化,不排除演化过程中流体—岩浆间存在相互作用。雄村、甲马和南木三矿床,均有幔源和壳源物质参与成矿,南木矿床壳源比例最高,三者均属于以流体为介质的壳幔相互作用的产物。（8）雄村形成于青藏高原造山带主碰撞（65～41Ma）晚期的间歇性松弛（52～42Ma）向晚碰撞地壳挤压抬升（40～38Ma）转换阶段,而甲马和南木形成于青藏高原造山带后碰撞阶段（25～0Ma）,与中新世（20～14Ma）冈底斯地区东西向伸展相关。造山带主碰撞期较强的挤压应力可能导致深源成矿流体快速高位上侵,而后碰撞伸展期,深源流体可以在地壳长时间滞留,应力差异导致了冈底斯地区两期流体成矿作用在成矿元素上的差异,伸展期有更多的壳源物质参与。（9）雄村矿床形成于40～35Ma间的高原强烈隆升期,隆升剥蚀导致了早期似斑岩型矿化的形成和晚期脉型矿化的套生。甲马和南木矿床形成于20～14Ma间的高原强烈隆升期的晚阶段,南木矿区普遍存在的绢英岩化叠加在钠、更长石化之上可能与隆升有关?需要进一步研究。更多还原

【Abstract】 The systematic petrographical study,microthermometry,Raman probe,and SR-XRF analysis were performed for fluid inclusions from 3 typical deposits.These deposits are Xiongcun copper-gold deposit which is porphyrylike-epithermai low-temperature multiplex deposit formed in main collisional phase of Gangdese ore-forming belt,Jiama skarn copper-polymetallic deposit and Nanmu porphyry Cu-Mo deposit both formed in post-collisional phase.Then get some understandings:（1） The phenomenon of boil or phase separation occur with ore-forming fluids evolvement in 3 deposits.This phenomenon relate to ore-forming system’s pressure continually release.Settling of 3 deposits’ ore-boy is controlled by tectonic cracked belt.And this make the condition for ore-forming system’s pressure release.（2） Ore-forming deepness of the 3 deposits is shallow,and about 1.5km in Jiama,about 1km in Nanmu,and Xiongcun is most shallowest.This accord with magma fluid’s participation of the 3 deposits,Jiama has magma fluid in most proportion,and Xiongcun has magma fluid in least proportion.（3） Nanmu’s content of Cu in fluid inclusions is highest,but the ore-forming scale is least. This relate to the lowest cool speed of ore-forming system in Nanmu.（4） There is a great deal of gas in ore-forming fluid system in the 3 deposits.Nanmu differ from Xiongcun and Jiama.The component of the gas in Nanmu is CO₂,and there are hematite, magnetite and goethite daughtermineral in inclusions.These indicate ore-forming fluid’s f_o2 is highest.（5） Forming of the 3 deposits relate to acidic alteration,as sericitization and chloritization. Acidic alteration consume H⁺,and make the fluid close to litmusless or alkalescence.This is very important to keep high content of HS^- in ore-forming fluid,and ensure sulfid’s deposition and ore-forming.（6） By the research to 3 typical deposits in Gangdese ore-forming belt,ore-forming geochemical process of Cu can be concluded:deep-seated origin fluid supply enough matter for copper deposit’s forming;tectonic cracked belt make for pressure release,phase separation and Cu enrich in high salinity fluid,and cracked belt prepare the room for the setting of copper deposit; relative fast cool speed is a important reason to make Cu’s deposition and ore-forming,and fluid with lower f_o2,close to litmusless or alkalescence is propitious to Cu’s largely deposition as sulfide.Ore-forming process is a process with many factor’s action above,and is a dissipative process with entropy decrease.So there need continual steady heat driving and relative open ore-forming condition.（7） The matter’s origin of Nanmu and Jiama deposit are associated with related crust-mantle mix origin stocks.Ore-forming fluid and ore-forming porphyry magma possibly have same deep-seated origin,both parallel evolvements.And there is possibly action each other between fluid and magma in the evolvement.There are both mantle-origin and crust-origin matter to take part in ore-forming process in Xiongcun,Jiama and Nanmu deposit.And the proportion of crust-origin in of Nanmu is highest.And the 3 deposits both are produce of crust-mantle action which medium is fluid.（8） Xiongcun form in the transformation phases of intermittence flab（52～42Ma） in Himalayan-Tibetan orogenic belt terminal phases of main-collision（65～41Ma） to late-collision crust extrusion-up（40～38Ma）.Jiama and Nanmu form in Himalayan-Tibetan orogenic belt post-collision phases（25～0Ma）,relating to east-west extension of Gangdese in Miocene epoch （20～14Ma）.Orogenic belt main-collision phase’s higher extrusive stress may result deep-seated ore-forming fluid fast up-intrude.In post-collision extended phases,deep-seated ore-forming fluid can keep in crust with longer time.Difference of stress result the difference at ore-forming element in ore-forming effect of two periods fluid,and extended phases have more crust-origin matter.（9） Xiongcun deposit form in Tibetan intensive uplifting phases,40～35Ma.Uplifting and erosion result the form of porphyry-like mineralization and vein mineralization.Jiama and Nanmu deposit form in terminal phases of Tibetan intensive uplifting phases,20～14Ma.There are widely sericitization alter albite and bytown in Nanmu deposit,and do this related to uplifting? The research needs to be performed farther.更多还原