【作者】 梁婷；

【导师】 陈毓川；

【作者基本信息】 长安大学 ， 地质工程， 2008， 博士

【摘要】 广西大厂长坡-铜坑锡多金属矿床位于江南古陆西南缘、著名的丹池成矿带的中部,是我国重要的有色金属矿业基地和国内外著名的超大型的锡多金属矿床,已探明的锡金属量超过100万吨,并伴有Cu、Zn、Pb、Sb、Ge、In、Cd、Se等,研究意义和经济意义巨大。多年来,一直受到地学界的关注。矿床经过了近六十年的研究、开发,在区域地质、地层、构造、岩石学、同位素、成矿物化条件等方面积累了丰富的资料,但长坡铜坑矿床的成因问题,至今存在分歧,分歧焦点体现在成矿时代、矿床成矿物质来源和成矿流体来源这三个主要方面。论文是在前人的大量工作基础上,对长坡-铜坑锡多金属矿床成因研究中存在争议的问题进行了较为详细的矿物学、岩石学、矿床学、矿床地球化学、同位素地球化学和同位素年代学等方面的研究,主要取得了以下进展:（1）通过野外地质调查和室内显微镜下的观察和研究,用大量的事实说明了矿床中层状矿体的形成是成矿流体沿层交代有利地层形成的,层状与脉状矿体之间存在相互穿插的关系,为同一成矿期的产物。这为正确认识大厂矿床的成因提供了扎实的基础地质资料。（2）通过矿物学、矿石学、微量元素和稀土元素地球化学研究,探讨了不同产状矿物之间、不同类型矿体之间成矿元素的变化和运移特点,结合铅、硫同位素研究,提出矿体中成矿物质的来源是相同的,是与岩浆活动有关的,主要来自地壳,也可能有幔源物质的加入。成矿物质的运移方向是由下部到上部,由近岩体向远离岩体。不同阶段形成的矿石矿物及脉石矿物中稀土元素的含量以及变化特征是一致的,均具有早期δEu的负异常,晚期δEu的正异常,反映了矿区成矿环境可能存在一个由相对还原向相对氧化的变化过程。（3）流体包裹体的研究表明,不同类型矿体中流体包裹体的特征基本是一致的,流体成分是以CO₂-H₂O为主,反映出他们应该是同一成矿期成矿作用的产物。He、Ar同位素分析结果显示,成矿流体来源主要来自地壳,但同时有地幔流体的参与。矿物中幔源He所占的比例从成矿的早期到晚期,含量依次减少,而壳源氦则相应增加,晚期有大气降水的参与。（4）利用先进的技术手段,查明了矿区成岩、成矿作用发生的时代。针对不同的测试对象,采用了不同的同位素测年方法,结果都证实了矿床形成不是泥盆纪地层物质沉积期间富集的,而是燕山期形成的,尤其以白垩纪中期最为集中。同时提出了矿床的形成并非与单一的一次岩浆活动有关,而应该是与多期岩浆活动有关,成矿与成岩的时代应该是趋于一致的,且随着岩浆活动的结束,也许成矿作用还会延续一段时间。从而为成矿模式的建立提供了充分的年代学依据。（5）将矽卡岩型锌铜矿体和长坡-铜坑91号、92号及高峰100号矿体作为一个整体加以考虑。从不同的角度分析了成矿条件、成矿物质运移和元素富集规律等。提出了矿床的形成是与燕山期花岗岩有密切联系的。岩浆活动为成矿提供了物质来源和热源,有利的地层和构造条件为成矿提供了物质运移的通道、空间和动力。岩浆活动、地层、构造三者有机的、“非常罕见”的耦合,才促成这个超大型矿床的形成。同时由于成矿环境的变化,造成了矿床深部形成矽卡岩型硫化锌铜矿体,上部形成以锡石为主的多金属硫化物矿体的分带现象。100号矿体与91号、92号矿体相比,虽然在产状不同,但成矿物质、成矿流体的来源是一致的。差异在于其形成是以充填为主,即含矿流体充填礁灰岩中由于断裂或礁体不同部位层间滑脱（剥离）形成的“虚脱空间”形成的。以上成果,证实了大厂锡多金属矿床的形成是与燕山期岩浆热液活动有关的后生成因。这一研究是对前人研究的补充和提升,对指导大厂矿区的找矿具有重要的理论和实践意义。更多还原

【Abstract】 Changpo-Tongkeng tin-polymetallic deposit located in Dachang, Guangxi Province is in the Southwestern margin of the Jiangnan old land, and the middle of Danchi metallogenic belt. As an important nonferrous metal mining industry base of China and a famous ultra-large tin-polymetallic deposit in the world ,with the proven tin reserve over one million ton and associated with Cu, Zn, Pb, Sb, Ge, In, Cd and Se etc, it has the great significance both in academic and economic. So it has attracted the attention of geologists and has been researched and exploited for nearly 60 years and has accumulated abundant data on the regional geology, stratum, tectonics, petrology, isotope and physical-chemical conditions of mineralization etc. Nevertheless, there has been debated on the metallogenesis. The difference focused on three aspects: metallogenic epoch, the origin of ore-forming materials and the source of ore-forming fluids.Based on the previous research achievements, the thesis studied the debatable problem by detailed investigation on mineralogy, petrology, mineral deposits, deposit geochemistry, isotope geochemistry and isotopic chronology, and achieved following progresses:1.The field investigation and the indoor observation and research showed that the formation of stratiform ore bodies is the replacement of the favourable stratum by ore-forming fluid. The stratiform ore-bodies and vein-type ore-bodies interpenetrated each other, which suggesting they were formed at the same mineralization processes. These results provide solid essential geological data for correct understanding of the deposit genesis.2. Discussed the change and migration characteristics of ore-forming elements among minerals with different occurrence, ore-bodies of different types from the aspects of mineralogy, ore petrology, trace elements, rare earth elements and isotopes of lead and sulfur. The results indicated that the ore-forming material of different ore-bodies is homogenous, which related with magma activity and come from the crust and maybe combined material from mantle. The migration of ore-forming material is from the bottom to up and from near to far from rock mass. Rare earth element standard distribution pattern in ore and rocks that formed in different ore forming stages are similar. TheδEu abnormality values from negative at the early stage to positive at the late stage, suggest the changes of ore-forming environment from a relative reduction to the relative oxidation.3. Fluid inclusions in ore bodies of different types are CO₂-H₂O type and with same features, suggesting their formation in the same mineralization process. He and Ar isotope data shows that the ore-forming fluids mainly derived from crust, but partly derived from mantle. The mantle-derived helium reduced from the early to late stages, crust- derived helium changed in opposite way, in which precipitated water involved in the late stage.4. As curtained the diagenetic and mineralizatic epochs of the mine by using suitable dating methods for different object, which suggest that the Dachang tin-polymetallic deposit is not formed in Devonian, but in the Yanshan period, particularly centralized in the mid-Cretaceous. Proposing that the deposit formation is not connected with single magma activity, but with multistage of magamatism. The rock and ore formation epochs should be unanimous in which perhaps ore-forming process would last for short time after the rock formation. The results provided sufficient chronological basis for building metallogenic model.5. Integrating information of Changpo-Tongkeng No. 91, No. 92 and Gaofeng No.100 ore bodies to analysis the ore forming condition, movement and enrichment pattern of ore-forming material, the thesis suggest that the ore formation closely related with granite of Yanshan period, in which magma movements provided ore-forming materials and energy; favourable stratum and structure conditions supplied ore-forming transport channels, space and force. The rational miracle combination of magma movement, stratum and structure led to the formation of the ultra-large deposit and the alteration of mineralization environment resulted in ore zoning, in which the skarn-type copper-zinc sulfide ore formed in the lower part of the deposit, tin- polymetallic sulfide ore formed in the upper part. The No.100 ore body is formed by the ore-bearing fluid filling“collapsed space”in the reef limestone, which resulted from fault activities or detachment of different stratums. Comparing No.100 to No.91 and No.92 ore-bodies, although their occurrence is different, the genesis of ore-forming materials and sources of ore-forming fluid are consistent.In summary, all evidence confirmed that the Changpo-Tongkeng tin-polymetalltic deposit is epigenetic and related to Yanshan period magmatic hydrothermal movement. This research replenished and deepened previous achievements and has a great significance for guiding prospecting around Dachang.更多还原