【作者】 陈本金；

【导师】 温春齐；

【作者基本信息】 成都理工大学 ， 矿物学岩石学矿床学， 2010， 博士

【摘要】 黔西南地区地处杨子地台与右江褶皱带的过度带,是我国最重要的卡林型金矿床集中区之一,该区卡林型金矿床可分为断裂控制型和岩层控制型两大类。断裂控制型金矿床产于高角度压扭性断裂中,赋矿层位一般为中、下三叠统地层,容矿岩石主要是泥质粉砂岩和粉砂质泥岩;而岩层控制型金矿床主要产于上二叠统地层中,容矿岩石主要为生物碎屑灰岩。该区金矿床虽然经过很多研究者的研究并取得不少研究成果,但对矿床成矿机制及动力学背景的认识还存在很大分歧。因此,作者选择水银洞金矿床进行典型解剖,对其成矿机制及大陆动力学背景进行系统研究。全文共分7章内容进行阐述。1)论文首先综述了选题依据及研究意义、国内外对大陆动力学与成矿作用及对卡林型金矿研究现状,提出了论文的研究内容和研究方案,对研究成果进行了总结并归纳出主要创新点。2)通过区域地质研究,认为水银洞金矿床不仅受构造控制,而且有利岩性组合也是重要的控制因素之一。该金矿床位于灰家堡背斜核部,矿体以层状、似层状为主,产于粘土岩→不纯灰岩→粘土岩组合的不纯灰岩中。只有少量的金矿体受低角度的断层控制。3)对岩相古地理和Au、As、Sb、Hg等中低温矿床的时空分布规律分析,认为黔西南地区特殊的岩相古地理环境及其演化,不仅为卡林型金矿床的形成奠定了丰富的成矿物质基础,而且形成了有利Au沉淀富集的地层组合。因此,岩相古地理环境及其演化对卡林型金矿床的成矿作用和在区域上的分布具有重要的控制作用。4)系统的地球化学研究表明,水银洞金矿床成矿流体和矿质是右江盆地从形成到结束长期演化的结果,均具有多来源性。成矿物质Au主要来自沉积地层,但有来自岩浆活动形成的成矿流体(幔源铅)及混入地壳淋滤物质;成矿流体主要来自大气降水形成的地下热水,但有地下热卤水和岩浆热液水的加入混合。成矿流体属中低温(96.7～220℃)、低盐度(0.635～9.861 wt%NaCl,平均值为4.282±2.260wt%NaCl)、中等密度(0.725～0.977 g/cm3,平均值为0.910±0.061成都理工大学博士学位论文?g/cm3)的流体;脉石英阶段流体水化学类型属Cl--Na+型或SO42﹣-Cl--Na+型,方解石阶段属SO42--Cl--Ca2+型。5)黔西南地区历史和现今区域地震活动性较弱,且震源深度浅,推断该区除控制右江盆地边界的断裂为深大断裂外,其余大部分断裂为伴随右江盆地形成和演化过程中形成的同生断裂;黔西南及邻区的卡林型金矿床分布面积广,成矿时间均为燕山晚期,暗示靠部分深切地壳到达地幔的深大断裂在燕山晚期将如此巨量的成矿物质带到地壳浅部形成大面积分布的金矿床可能性不大,而是在右江盆地长期演化过程中形成巨量的成矿流体,于燕山运动晚期地壳伸展造成成矿流体大面积流动到合适部位沉淀富集的结果。6)综合分析构造组合及沉积演化以及岩浆活动特点,初步厘定出D-K黔西南地区大陆动力学演化系列为:(1)海西构造阶段(D-P2),即拉伸-裂陷阶段;(2)印支阶段(P3-T3),即弧后盆地发展阶段;(3)燕山运动早中期(T3-K),即陆内造山阶段;(4)燕山运动晚期(大致150-70Ma),即造山后地壳伸展阶段,也是黔西南地区大面积中低温矿床的形成阶段。7)根据成矿流体水源、矿源、热源分析,结合区域构造、岩相古地理及成矿时代讨论,提出水银洞金矿床形成的大陆动力学背景和成矿机制为:燕山晚期,中国东部构造体制大转换,地幔上涌,黔西南及邻区由早期的挤压收缩转换为垂向伸展隆升,断裂复活,驱动成矿流体向压力较小的方位流动,当成矿流体遇盆地边缘的深大断裂时即改变方向向上运移,在上升的成矿流体压力小于地下水的压力或断裂受封堵时,流体转向沿古岩溶面或不整合界面发生测向运动进入台地内,部分成矿流体与周围岩石发生交代作用,形成构造蚀变体,局部形成卡林型金矿体(如水银洞金矿床Ⅰa矿体),而大部分成矿流体沿切穿地层的次级断裂向上运移,并向两侧有利容矿岩层渗透,形成受岩性控制的矿体。由于次级断层的贯通和有利岩性组合的重复出现,致使水银洞金矿床具有多层矿体产出,如水银洞金矿床的Ⅱf、Ⅲa、Ⅲb、Ⅲc等受岩层控制的矿体。更多还原

【Abstract】 Southwestern Guizhou is located in the transition zone between Yangzi plateform and Youjiang fold belt. It is one of the most important Carlin-type gold deposits. The Carlin-type gold deposits in the area can be divided into fault-controlled and strata-controlled. The Fault-controlled gold deposits are localized at the high-angle compressive-shear faults, hosted generally in the Middle and Lower Triassic strata and the host rocks are mainly pelitic siltstone and silty mudstone. The Strata-controlled gold deposits mainly are localized at the Upper Permian strata and the host rocks are mainly bioclastic limestones. Although plenty of researchers have made lots of researches and many results have been obtained about the gold deposits , there still is a big difference on the mineralizing mechanism and dynamics background. So the author chooses Shuiyindong to conduct a typical anatomy, especially do a system research about its mineralizing mechanism and the continental dynamics background. The paper is divided into seven chapters to elaborate.1) This paper first summarizes basis of topic selection and the significance of research, and the research status on continental dynamics and metallogenesis, and the Carlin-type gold deposits at home and abroad, then presentes research content, research programs of this thesis, summarizes research results and the principal innovations.2) From the regional geological study, the Shuiyindong gold deposit is not only controlled by the faults but by favorable lithologic associations. The gold deposit is located nearby the core of Huijiabao anticline, the orebodies are mainly stratiform or stratoid ones, hosted mainly in the impurity limestone within the sedimentary series of clayrock—> impurity limestone—> clayrock . Only a small amount of orebodies are controlled by low-angle faults.3) Researches combining the Lithofacies palaeogeography with temporal and spatial distribution of Au, As, Sb, Hg et al. low-temperature deposits in the Southwest Guizhou aera shows that the special lithofacies palaeogeography environment and evolution history of the southwestern Guizhou, not only lay the ore-forming materials foundation for formation of the gold deposits, but also form the favorable series of sedimentary rocks. Therefore, the lithofacies palaeogeography environment and evolution of the district play a controlling role on the mineralization and distribution of the Carlin-type gold deposits.4) The systematic geochemical studies indicate that,the ore-forming materials and fluids of the Shuiyindong gold deposit has multiple sources. The ore-forming minerals mainly is from orogenic belt and sedimentary rocks , originated partly from plutonian minerales brought by mantle magma intrusion and deep crust. The ore-forming fluids mainly originated from? meteoric-hydrothermal water, probably, immingled with certain parts of salt- groundwater and magmatic hydrothermal water, belongs to low-medium temperature (96.7℃～220℃), low sality (l4.282±2.260% wt%NaCl) and medium density (0.910±0.061 g/cm3) fluid. The hydrochemical type of fluid inclusions found in quartz inclusions belongs to Cl--Na+ or SO42-﹣-Cl--Na+ type, while the hydrochemical type of fluid inclusions found in calcite inclusions belongs to SO42--Cl--Ca2+ type. .5. The seismic activity of history and present in the southwesternGuizhou and its adjacent areas is weak, and the shallow focal depth, inferres except the deep faults which controlled Youjiang basin boundary, the other faults formed with Youjiang basin formation and its evolution, while the ore-forming times of?the Carlin-type gold deposits distributed widely in the southwesternGuizhou and its adjacent areas all are the late Yanshan movement ,and shows that it is unlikely that such a huge amount of ore-forming materials are brought to the shallow crust through deep- large faults to reach the mantle to formed large-scale distribution of gold deposits.But crustal extension in late Yanshan period droved large-scale ore-forming fluids formed in the long-peroid evolution of the Youjiang basin to the appropriate parts of strata ro stracture to accumulate and forme wide area gold deposites6) According to structural composition and sedimentary evolution combined with magmatic activity characteristic analysis, the preliminary determination of the evolution series of in continental dynamics in southwesternGuizhou in D-K are: (1) Abstract? ?Hercynian tectonic phase (D-P2), that is stretching - rift stage; (2) Indo-China period (P3-T2), or back-arc basin development stage; (3) early–mid period of Yanshan movement (T3-K), namely, intracontinental orogenic stage; (4) Late Yanshan Movement (roughly from 150-70Ma), which is extension phase of post-orogenic crustal, is also the stage of wide area low temperature deposits in southwestern Guizhou.7) According to study on water sources, mineral sources and heat sources of ore-forming fluids, combined with discussion of regional structure, lithofacies palaeogeography and metallogenic epoch, this thesis puts forward background of continental dynamics of Shuiyindong gold deposit: Late Yanshan Movement (roughly 150 -70Ma), with big conversion of the tectonic regime in eastern China, mantle upwelling, where have a strong mantle magmatism, the southwesternGuizhou and its adjacent areas are converted to vertical stretching uplift from the early shrinkage deformation, mafic dikes and alkaline rocks along the tensile fracture are formed and cause the crust warming. The stretching action and thermal power, drived ore- forming fluid to move to the smaller pressure areas. When the ore-forming fluid flow to deep-large faults at the edge of basin ,it changes flowing direction and upward migrate, while the ore-forming fluid pressure is less than the pressure of underground water, the vertical movement fluids moved into the platform along the ancient karst surface or unconformity interface . The ore-forming fluid acted partly with the surrounding rocks formed structural alteration dodies, or formed Carlin-type gold ore boddies (such as orebodiesⅠa in the Shuiyndong gold deposit,), while most of the remaining ore-forming fluids migrated upward through the sub-faults cutting through the strata and penetrated into favorable strata, formed ore-dodies controlled by ore-hosted strata. sub-faults and favorable strata appear repeatedly, resulted in gold deposits with a multi-floors, such as gold ore dodies in the Shuiyindong gold deposit:Ⅱf,Ⅲa,Ⅲb, etc.更多还原