克鲁-冲木达成矿带斑岩型与矽卡岩型矿床的成因联系研究

发布时间：2018-08-28 09:24

【摘要】：目前在冈底斯成矿带上已发现大型、超大型甚至巨型斑岩型铜矿床,这些斑岩型矿床多形成于青藏高原陆-陆碰撞之后,受高原东缘的NW向大规模走滑断裂系统控制。冈底斯成矿带东段位于冈底斯-念青唐古拉山板片次级构造单元冈底斯-岩浆弧的东段南缘,属冈底斯铜多金属成矿带的重要组成部分,主要以产出斑岩型铜矿床和矽卡岩型铜多金属矿床为特征。目前的工作主要集中在以斑岩型铜钼矿化为主的中亚带和以铅锌钼矿化为主的北亚带,而对南亚带的矿床研究尚且十分薄弱。克鲁-冲木达成矿带隶属于冈底斯成矿带东段南亚带,位于西藏南部扎囊-桑日县之间,分布有努日、程巴、克鲁、冲木达和帕南等中到大型Cu-Mo-W(±Au)矿床,其中努日矿床和程巴矿床是该带新发现的大型矽卡岩-斑岩型的矿床和斑岩型矿床,两矿床矿化元素组合分别为Cu-Mo-W和Mo-Cu。该带斑岩型铜矿床和矽卡岩型铜多金属矿床的发现对整个冈底斯成矿带的矿床勘查和研究具有极重要的意义。论文依托于中国地质调查局“西藏山南地区铜多金属矿成矿地质背景与成矿条件及找矿方法技术研究”项目(12120113095700),在充分收集整理前人研究成果基础上,通过典型矿床的剖析研究,从岩体的地质特征、地球化学特征、成矿物质来源、成矿流体来源和矿床的时空分布特征等方面,探讨了了斑岩型铜矿床和矽卡岩型铜多金属矿床的成因联系。综合研究,取得了如下成果和认识:(1)矿床的地质特征和地球化学特征研究表明,克鲁-冲木达成矿带的斑岩型矿床和矽卡岩型矿床的岩浆岩形成于岛弧环境或同碰撞环境,具有埃达克岩或类埃达克岩的地球化学性质。(2)矿床黄铁矿、黄铜矿等硫化物的S、Pb同位素研究显示,克鲁-冲木达成矿带的斑岩型矿床和矽卡岩型矿床具有相似的成矿物质来源,与北亚带、中亚带相比,北亚带的成矿物质主要以壳源为主,中亚带和南亚带主要以壳幔混合源为主,只是南亚带中壳源物质占的比例相对中亚带较大。(3)流体包裹体的岩相学、氢氧同位素及成分组成研究表明,矽卡岩型矿床成矿流体中岩浆水是占据主导地位的,与大气降水发生混合作用是次要的,而斑岩型矿床在主要成矿阶段成矿流体以岩浆水为主,但在成矿作用后期阶段成矿流体已有相当数量的大气降水的混入。(4)克鲁-冲木达成矿带斑岩型铜矿床和矽卡岩型铜多金属矿床的成矿作用时间大致相当(30~23Ma),矽卡岩型矿床一般分布于斑岩铜矿床的外围或是呈独立矿床产出,顶部和浅部矽卡岩型矿化也可以作为寻找斑岩型矿床的标志之一。综合分析认为,克鲁-冲木达成矿带的斑岩型铜矿床与矽卡岩型铜多金属矿床受控于统一的地球动力学背景,在成因上与统一的斑岩-矽卡岩型成矿系统中的岩浆-热液成矿作用有关,是在晚碰撞阶段印-亚大陆的持续会聚和挤压背景下,由下地壳或上地幔局部熔融的中酸性岩浆沿构造断裂通道上侵,在花岗质岩浆岩顶部及其内外接触带形成斑岩矿床的同时,自岩浆活动中心向外迁移的含矿气液,在岩体外接触带或远离岩体的钙质围岩地层中与围岩发生交代形成矽卡岩铜多金属矿床。
[Abstract]:Large, super-large and even giant porphyry copper deposits have been found in the Gangdise metallogenic belt. Most of these porphyry copper deposits were formed after the continental-continental collision of the Qinghai-Tibet plateau and controlled by the NW-trending strike-slip fault system in the eastern margin of the plateau. The southern margin of the eastern segment of the magmatic arc is an important part of the Gangdise copper polymetallic metallogenic belt, characterized by the occurrence of porphyry copper deposits and skarn copper polymetallic deposits. The Klu-Chongmuda ore belt is located between Zaburg-Sangri County, southern Tibet, and belongs to the South Asian belt in the eastern part of the Gangdise metallogenic belt. There are medium-to-large Cu-Mo-W(+Au) deposits in Nuri, Chengba, Klu, Chongmuda and Panan, among which the Nuri and Chengba deposits are the newly discovered large-scale skarn-porphyry deposits. The discovery of porphyry type copper deposits and skarn type copper polymetallic deposits in this belt is of great significance to the exploration and study of the deposits in the whole Gangdise metallogenic belt. On the basis of fully collecting predecessors'research results and through the analysis and study of typical deposits, porphyry types are discussed from the aspects of geological characteristics, geochemical characteristics, source of metallogenic materials, source of metallogenic fluids and spatial and temporal distribution characteristics of deposits. The genetic relationship between copper deposits and skarn type copper polymetallic deposits has been studied comprehensively and the following achievements and understandings have been obtained: (1) The geological and geochemical characteristics of the deposits show that the porphyry type deposits and the magmatic rocks of skarn type deposits in the Kelu-Chongmuda ore belt were formed in island arc environment or in collision environment with adakite or adakite. Geochemical properties of adakite-like rocks. (2) S and Pb isotope studies of sulfides such as pyrite and chalcopyrite show that porphyry deposits and skarn deposits in the Kelu-Chongmuda ore belt have similar sources of ore-forming materials. Compared with the northern and central sub-belts, the ore-forming materials in the northern sub-belt are mainly crustal, and the central and southern sub-belts are mainly crustal. The crust-mantle mixed source is the main source in the belt, but the proportion of crust-derived material in South Asia is larger than that in Central Asia. (3) The study of petrography, hydrogen-oxygen isotope and composition of fluid inclusions shows that magmatic water is dominant in the ore-forming fluid of SKARN-TYPE deposits, and mixing with atmospheric precipitation is secondary, while porphyry-type deposits are secondary. The ore-forming fluid of the deposit is mainly magmatic water in the main metallogenic stage, but a considerable amount of atmospheric precipitation has been mixed into the ore-forming fluid in the late stage of the mineralization. (4) The metallogenic time of porphyry copper deposit and skarn copper polymetallic deposit in the Kelu-Chongmuda ore belt is approximately the same (30-23 Ma), and skarn type deposit is generally distributed in the late stage of the mineralization. Porphyry copper deposits occur in the periphery or as independent deposits, and SKARN-TYPE mineralization in the top and shallow parts can also be used as one of the indicators for prospecting porphyry-type deposits. The magma-hydrothermal mineralization in the PORPHYRY-SKARN type metallogenic system is related to the continuous convergence and compression of the Indo-Asian continent during the late collision stage. The intermediate-acid magma partially melted from the lower crust or the upper mantle intruded along the structural fracture pathway and formed porphyry deposits at the top of the granitic magma and its inner and outer contact zones. Skarn copper polymetallic deposits are formed by the outward migration of ore-bearing gas from the magmatic activity center in the calcareous wall rock strata of the outer contact zone or far away from the rock mass.
【学位授予单位】：成都理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P618.41;P618.2

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