滇西保山核桃坪铅锌矿区F₁断裂构造变形及成矿关系解析

【作者】 黄琴辉；

【导师】 薛传东；

【作者基本信息】 昆明理工大学 ， 构造地质学， 2010， 硕士

【摘要】 滇西保山核桃坪铅锌矿区位于保山—镇康地块北部保山—施甸复背斜与北西向澜沧江深大构造—变质带交汇处的核桃坪复式背斜北东倾伏端,处于保山、兰坪—思茅、昌宁—孟连三个微板块的汇聚地带而偏向保山地块一侧。F1断裂带是区内铅锌矿床的主要控矿构造,V1主矿体沿断裂走向分布,各种构造变形现象较为丰富。本论文主要立足现今Fl断裂展布的基本面貌及其构造地质特征,从构造岩及蚀变矿物晶内变形显微构造、流体包裹体迹面(FIP)特征分析入手,借助矿物微区分析和显微构造分析技术,从不同角度精细剖析构造成生发展中流体活动留下的显微构造特征,系统地研究矿床各成矿期(阶段)构造流体特征及其相互作用,确定F1断裂的时空演化序次,分析其发生、发展及演化过程,探讨断裂构造的控矿作用及构造对流体运移的影响。论文主要取得以下研究成果与认识：(1)本文首先从F1断裂宏观结构面力学性质入手,分析其构造型式、规模、力学性质,结果表明,F1断裂为一逆冲断层,先后至少发生了三期构造活动,经历了右行压扭性→左行扭压性→扭性的力学性质转变。(2)宏观构造变形,以围岩的透入性面理,非透入性的张、剪性节理以及受构造挤压形成的小褶皱等为主。(3)显微构造变形,包括显微裂隙、波状消光、机械双晶、动态重结晶、应力影及旋转残斑等,其中石英中发育大量的流体包裹体面(FIP),是矿液运移过程中应力及组成变化细节的原始记录器。显微构造变形特征反映,断裂构造是在韧性—脆性变形条件下发生的。共轭节理、微裂隙及脉体和FIP产状对主压应力方向的指示与宏观构造基本一致,为近南北向和近东西向两个方向。经石英动态重结晶法估算,成矿期的应力差为38.1-56.5 Mpa,构造变形强度属中等。利用石英动态重结晶颗粒分形温度计计算,确定变形温度为低绿片岩相(300℃～500℃)。石英贯穿整个成矿作用过程,石英中包裹体多为纯液相和气液两相类型。V,矿体中石英、方解石中的包裹体测温结果显示,热液成矿大致经历了中高温(250～300℃)和中低温(100～230℃)两个热液成矿阶段,前者可能对应热液矽卡岩化-硫化物矿化阶段,后者对应热液脉状硫化物-碳酸盐矿化阶段。(4)在宏观及显微构造分析的基础上,对核桃坪铅锌矿区成矿机理做了初步分析,铅锌成矿与F1断裂关系密切,整个断裂带体系控制着成矿流体的产生、演化、运移直至矿化。早期的构造变形为成矿流体运移提供了主要通道；中期的构造变形控制了整个矿化过程,创造了矿化所必需的物理化学条件和关键的应力机制,为矿质的沉淀富集提供了理想场所；晚期的剪切变形导致了中低温矿化作用的叠加。流体作为矿化的诱因,起着促进变形、裂隙扩容、富集和输送矿质的重要作用。(5)对矿区构造—流体—成矿作用系统中控矿断裂带构造变形特征的解析,一方面利于全面认识断裂带的力学性质与构造演化,也可为精细识别和重塑难识别热液脉型金属矿床成矿作用过程及其动力学机制提供有效的约束。更多还原

【Abstract】 Hetaoping Pb-Zn deposit, Baoshan western Yunnan is located northeast pitching side of hetaoping double plunging anticline, which is intersection baoshan-shidian double plunging anticline of north baoshan-zhenkang massif and lancang river deeply structural-metamorphic belt, in convergence zone of baoshan, Lanping-Simao, Changning-Menglian three micro-plate, tend to baoshan massif. F1 fault is major controlling structures, and No. V1 ore body and some other ore bodies distributes along the fault strike, and which is rich in varieties of structural deformation phenomena. In this thesis, based on the current basic structural geology features of F1 fault, Start to analyze microstructure deformation of tectonic and alteration minerals, fluid inclusions plane features, with minerals microscopic region and micro-structure analysis technology, analyze microstructure characteristics of fluid flow leaving in construction formation and development process, study systematic structural fluid characteristics and their interaction of each metallogenic, define time-space evolution sequence of F1 fault, Analyze occurrence, development and evolution process of F1 fault, investigate impact ore-controlling of fault structures on fluid migration. The results are asfollows:(1) Starting from the macro-structure on mechanical properties, Analyze structure type, size, mechanical properties,the results shows that F1 fault is a thrust fault and has had three phases of structure activities. It has experienced the right-lateral compresso-shear→left-lateral shear-compressive→shear.(2) Macro-structural deformation, to the main penetrative foliation of wall rock、Non-penetrative sexual tension、shear joints and small folds formed by tectonic compression etc.(3)Microstructure deformation, including microscopic cracks, wavy extinction, mechanical twins, dynamic recrystallization, the stress shadow and rotation spots and other residue etc. A large number of fluid Inclusion plans in quartz are original record device of the migration of ore fluid composition changes during the stress and details. Microscopic structure features reflect that faults occurred under the conditions of the ductile-brittle deformation. The principal compressive stress direction of Conjugate joints, micro cracks and veins, and the FIP occurrence is consistent with the macro-structure, Nearly north-south and east-west direction. The stress difference is 38.1-56.5 Mpa by estimation method of dynamic recrystallization quartz, this value reflect medium intensity of tectonic deformation. Calculate by thermometer fractal of dynamic recrystallization quartz, deformation temperature is lower greenschist facies (300℃-500℃).Quartz throughout the mineralization process, inclusions in quartz are mostly pure liquid and gas-liquid two-phase. inclusion temperature results in quartz、calcite of V1 ore body showed that hydrothermal mineralization has gone through Middle-high temperature(250-300℃) and middle-low temperature(100-230℃) hydrothermal mineralization. the former may correspond to hydrothermal skarn-sulphide mineralization stage, the latter corresponds to hydrothermal vein sulfide-carbonate mineralization stage.(4)At the macro and micro structural analysis based on, analyze pb-zn ore-forming mechanism of Hetaoping preliminarily, there have a close link F1 fault and the ore between.The fault system control that ore fluid generation, evolution, migration until mineralization. The early construction provided the main channel for fluid; Medium-term structural control the mineralization process, created physical and chemical conditions and critical stress mechanism for mineralization necessarily, provided the ideal place for the precipitation of mineral enrichment; Late shearing led to the superposition of mineralization. Fluid as the incentive of mineralization, played the important role for deformation, expansion cracks, mineral concentration and transportion.(5) Resolve to tectonic deformation of F1 ore-controlling fault in the mining structure-fluid mineralization system, on the one hand, understand the mechanical nature of the F1 fault zone and tectonic evolution helply fully, provide an important constraint for precise identification and remodeling process of mineralization and difficult to recognize hydrothermal vein-type metal deposits and region dynamic mechanism.更多还原