云南省元阳大坪金矿床成矿机制及找矿方向

发布时间：2018-01-11 07:34

本文关键词：云南省元阳大坪金矿床成矿机制及找矿方向　出处：《中国地质大学(北京)》2017年硕士论文　论文类型：学位论文

【摘要】：大坪金矿床是哀牢山金矿带典型矿床之一,被视为产于碰撞造山环境下的金多金属矿床。为了进一步查明矿床成因类型,结合区域成矿背景,以云南元阳县大坪金矿床地质勘查成果为依据,通过深入分析典型矿体地质特征,矿物组合特征,围岩蚀变特征,划分了成矿期次,并对成矿物质基础研究和控矿构造特征进行了总结,结果表明:(1)矿床主要受左行走滑剪切作用控制,矿体主要赋存于张扭性-压扭性空间过渡部位;(2)矿床为多期次构造-成矿作用、成矿物质来源多样、多成因热流体综合作用叠加改造,属于中温热液脉型金多金属矿床。利用显微测温和岩相学分析了大坪金矿床与金矿化关系密切的石英流体包裹体特征,结果表明;流体包裹体基本由富液相CO_2包裹体和不同CO_2/H_2O比例的CO_2-H_2O型包裹体以及含液相CO_2的三相包裹体组成。白钨矿石英脉中同时富含富气相CO_2包裹体,主成矿阶段(石英-黄铁矿阶段与多金属硫化物阶段)金矿石中富液相CO_2包裹体及三相包裹体占明显优势,少量富气相包裹体,南矿区石英-菱铁矿阶段大体上属于多金属硫化物阶段,三相包裹体占明显优势,少量富气相CO_2包裹体。包裹体测温结果显示,石英白钨矿阶段均一温度为209.4~380.1℃,峰值309~359℃,主成矿阶段石英-黄铁矿组合均一温度163.8~312.3℃之间,峰值196~266℃,石英-多金属硫化物阶段均一温度为222.3~388.7℃,峰值270~320℃;石英-菱铁矿阶段均一温度为194~357℃,峰值274~324℃。主成矿阶段包裹体测温显示两个成矿阶段均一温度变化双峰式区间特征,说明后期可能有新的流体加入。大坪金矿成矿流体特征符合造山型金矿床富CO_2(流体成分H_2O-CO_2+CH_4,N_2,H_2S),低盐度(5~8NaCleqv),中温(250~400℃),压力(1~4Kb)成矿流体特征。深源流体沿左行走滑剪切带上升过程中,在脆韧性转换带压力骤降,同时流体分异作用形成煌斑岩浆和富挥发分矿浆以及含水溶液,并发生了强烈的相分离作用,是本区关键的成矿机制。另外还存在后期流体加入,早期主要为下地壳麻粒岩相脱水形成的富CO_2流体体系,后期主要为上地幔流体体系,二者同时受控于强烈的壳幔混合作用。与矿体关系密切的煌斑岩,矿物学上金云母含量比较高,主要为幔源成因,在岩石化学组成上,SiO_2含量为47.98%~53.21%、K_2O/Na_2O在1.31~5.31之间,属钙碱性系列,表明煌斑岩具有幔源特征。煌斑岩的微量元素与稀土元素地球化学特征表明,岩石富集大离子亲石元素(Sr、U、Rb和Ba)和轻稀土元素(LREE)、相对亏损高场强元素(Ta、Nb和Ti),且Ta、Nb和Ti具“TNT”负异常;δEu值为0.26~0.304,Eu异常不明显;表明煌斑岩源区可能来自早期俯冲洋壳或造山带根部拆沉组分脱水形成富集流体在地幔源区发生交代作用形成的富集地幔,形成于碰撞后的板内构造环境。该区煌斑岩与金矿化源区特征相似,均为深部流体分异演化不同阶段的产物。大坪金矿床构造控矿明显,矿体明显受小新街断裂和次一级断裂控制,与矿体关系密切的煌斑岩脉可能是深部幔源流体在成矿作用中的表现形式。“构造-流体(脉岩)-矿化”三位一体找矿思路为本区深部及外围找矿指明了方向。找矿工作应在富碱斑岩发育和活动构造叠加的地区进行,重点找矿部位为煌斑岩和花岗斑岩出露地带,另外应注意多金属硫化物富集部位。
[Abstract]:Daping gold deposit is a typical deposit in Ailaoshan gold belt, is regarded as the gold polymetallic deposit lies in the collision orogenic environment. In order to further identify the type of ore genesis with regional metallogenic background, taking Yunnan County of Yuanyang Daping gold deposit geological exploration results as the basis, through in-depth analysis of the geological characteristics of typical ore, mineral assemblages. And the characteristics of wall rock alteration, the mineralization stages are divided, and the research on the material basis of mineralization and ore controlling structures are summarized. The results show that: (1) deposits are mainly controlled by the sinistral strike slip shear control, the main orebody occurs in the extensional - compressoshear space transition region; (2) deposit many times of tectonic mineralization, metallogenic material source diversity, comprehensive effect causes thermal fluid superimposed belongs to mesothermal vein type gold polymetallic deposit. Analysis of the Daping gold deposit and gold mineralization by microthermometry and petrography Quartz fluid inclusions, close results; type CO_2-H_2O inclusions and fluid inclusions by rich liquid inclusions of CO_2 and CO_2/H_2O in different proportions and three-phase inclusions in liquid phase CO_2. Scheelite quartz veins and rich in gas phase CO_2 inclusions, the main mineralization stage (quartz pyrite stage and polymetallic sulfide stage) stone rich fluid gold CO_2 inclusions and three phase inclusions is dominant, a small amount of gas rich inclusions in quartz and siderite, South stage generally belongs to the polymetallic sulfide stage, three-phase inclusions is dominant, a small amount of vapor rich inclusions. Inclusions CO_2 the results showed that quartz scheelite phase homogenization temperature of 209.4~380.1, peak 309~359 C, between the main metallogenic stage quartz and pyrite assemblage of homogenization temperature of 163.8~312.3 DEG C, the peak temperature of 196~266 DEG C, quartz polymetallic sulfide Stage homogenization temperature of 222.3~388.7, the peak temperature of 270~320 DEG C; quartz and siderite stage homogenization temperature of 194~357, the peak temperature of 274~324 DEG C. The main mineralization stage of inclusions shows two mineralization stages homogenization temperature changes in Shuangfeng interval feature, the later stage may have a new fluid added. Metallogenic fluid characteristics of Daping gold deposit with orogenic gold deposits rich CO_2 (H_2O-CO_2+CH_4 N_2, H_2S fluid composition,), low salinity (5~8NaCleqv), temperature (250~400 DEG C), pressure (1~4Kb) characteristics of ore-forming fluids. The deep fluid along the left lateral strike slip shear zone in the process of rising, the brittle ductile transition zone pressure drop, and fluid differentiation and formation of lamprophyre magma volatile rich mineral and aqueous solution, and the phase separation occurred strongly, is the key metallogenic mechanism. There is also another late fluid join, mainly for the early crust under granulite facies formed by dehydration of C rich O_2 fluid system, mainly for the late upper mantle fluid system, two controlled by the crust mantle mixing strongly. Close relationship with ore mineralogy lamprophyre, gold mica content is relatively high, mainly for mantle origin, in the rock chemical composition, the content of SiO_2 is 53.21% 47.98%~, K_2O/Na_2O between 1.31~5.31, is the calc alkaline series show lamprophyre characteristics of mantle source. With that of lamprophyre trace elements and REE geochemical characteristics of rocks are enriched in large ion lithophile elements (Sr, U, Rb and Ba) and light rare earth elements (LREE), depleted in high field strength elements (Ta, Nb and Ti), and Ta, Nb and Ti with "TNT" negative anomaly; Eu values of 0.26~0.304, Eu anomaly is not obvious; that the lamprophyre source area from the early subducted oceanic crust or orogenic root delamination component formed by dehydration of enriched fluid enriched mantle metasomatism formation occurred in the mantle source region, formed in the After the collision of intraplate tectonic environment. The characteristics of lamprophyre and gold mineralization in source region of the area are similar to deep fluid differentiation and evolution of different stages of the product. The Daping gold deposit, ore controlling structure, orebody is obviously controlled by street small fracture and secondary fracture, lamprophyre dikes and ore bodies may close relationship is a form of deep mantle fluid in mineralization. The tectonic fluid mineralization (Mai Yan) - "three-in-one prospecting for ore prospecting in the depth and periphery area of the direction. The prospecting work should be carried out in the alkali rich porphyry development and active tectonic superposition area, key prospecting site the lamprophyre and granite porphyry outcropping area, also should pay attention to multi metal sulfide enrichment site.

【学位授予单位】：中国地质大学(北京)
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：P618.51

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