上扬子周缘新元古界古油藏与铅锌矿共生聚集成藏成矿耦合作用的年代学约束

The accurate dating of petroleum reservoir and Pb-Zn deposits is a key scientific issue for the process and mechanism studies of hydrocarbon accumulation and metal mineralization. The intimate coexistence of Pb-Zn deposits with oil-gas reservoir indicates their genetic cause linkage and similar process and mechanism. In this study, three representative Neoproterozoic paleo-reservoirs with coexisting Pb-Zn deposits and their associated vein minerals are chosen as the research objects in the periphery of the upper Yangtze block. The key technologies mainly are the fluid inclusion Ar-Ar dating, the pyrite and bitumen Re-Os isotope geochronology, the sphalerite Rb-Sr dating and so on. This study will carry out the chronological framework construction of petroleum accumulation and Pb-Zn mineralization, and also establish their coupling relationship through multiple geochronology methods, using the dating of vein minerals and fluid activities as the bridge. This study attempts to establishment the isotopic direct dating methods and technologies for the multiple hydrocarbon accumulation and metal mineralization, which will contribute to the study on the process and mechanism of hydrocarbon accumulation and Pb-Zn mineralization. Combining the theory and methods of reservoir formation and metal mineralization and learn from each other will help to further reveal the spatial-time and origin relationship. It will provide the help for the petroleum and metal mineral cooperative exploration and comprehensive forecast.

油气藏和铅锌矿床的精确定年是成藏成矿作用过程和机理研究最为关注的核心科学问题。油气藏与铅锌矿在空间上密切共生或伴生，指示了两者成因上的有机联系以及成矿成藏过程和机理的相似性。研究以上扬子周缘三个典型新元古界古油藏和共生的铅锌矿及伴生的脉体矿物作为研究对象，采用高精度同位素定年技术，开展沥青Re-Os、闪锌矿Rb-Sr、闪锌矿流体包裹体Ar-Ar以及伴生矿物黄铁矿Re-Os和石英流体包裹体Ar-Ar等定年分析。通过多种地质定年方法的相互结合、相互验证，并以脉体的定年和流体活动作为纽带，从年代学的角度构建成藏与成矿的耦合关系，定量重建油气成藏和铅锌成矿的年代学格架。研究试图建立成藏-成矿的同位素直接定年方法和技术组合，促进成藏成矿过程机理的研究。研究将成藏与成矿的理论和方法有机结合并互为借鉴，有助于深入揭示油气藏与铅锌矿在时空上和成因上的联系，也将为油气和金属矿产的协同勘同和综合预测提供帮助。

油气藏和铅锌矿床的精确定年是成藏成矿作用过程和机理研究最为关注的核心科学问题。油气藏与铅锌矿在空间上密切共生或伴生，指示了两者成因上的有机联系以及成矿成藏过程和机理的相似性。研究以上扬子周缘楠木树、乌斯河、凹子岗三个典型新元古界古油藏和共生的铅锌矿及伴生的脉体矿物作为研究对象，通过详实的野外地质特征、同位素示踪和沥青Re-Os定年、闪锌矿Rb-Sr定年、方解石激光原位U-Pb定年等方面的系统分析，结合流体包裹体、沥青地球化学特征、裂变径迹热年代学等研究，揭示了沥青的形成时间和铅锌矿的成矿年代格架，并基于年代学的时序和相互关系分析了成藏和成矿作用的相互关系。研究表明：古油藏沥青均为高演化的焦沥青，三个铅锌矿床均为MVT型矿床；石英流体包裹体Ar-Ar定年获得了471.4±4.5Ma的年龄，沥青Re-Os同位素定年获得了（414±44Ma）和(ca.205-173Ma)两组年龄，定量揭示了四川盆地及其周缘震旦-寒武系存在奥陶-志留纪间和晚三叠世-侏罗纪间的两次油气成藏作用。闪锌矿Rb-Sr定年和方解石激光原位U-Pb定年揭示了上扬子板块周缘MVT型矿床存在中生代 (ca.200Ma）和古生代（ca.450-411Ma）两期成矿作用。油气成藏与铅锌成矿在时序上具有很好的一致性，表明了有机流体在成矿中的重要作用，这也得到了流体包裹体及其激光拉曼光谱研究的证实，揭示了油气成藏和铅锌成矿可能具有相同动力学机制，并提出了新的MVT型矿床形成的“两期流体混合模式”。研究建立了三个典型古油藏及其伴生铅锌矿成藏成矿的年代学格架，构建了油气成藏和铅锌成矿的相互作用和耦合关系及机理。建立的定年技术方法对于确定油气成藏和金属成矿的精确年龄方面具有广泛的应用前景。