四川盆地西南缘汉源地区铅锌成矿与油气成藏的成因关系

The intimate coexistence of the lead-zinc deposits with oil-gas reservoir suggests a genetic linkage between mineralization and hydrocarbon accumulation. This research focuses on lead-zinc deposits and ancient oil-gas reservoir in Dengying Formation around the Hanyuan district in southwest margin of Sichuan Basin, the research ideas of petroleum geology such as migration and accumulation of organic fluids will be introduced in the lead-zinc mineralization research; the nature and sources of ore-forming fluids, fluid migration pathways and possible mineralization processes will be revealed. Through the study of bitumen and source bed biomarkers, the source of organic fluid in the ancient oil-gas reservoir is determined, the migration of organic fluid and the process of hydrocarbon accumulation and destruction are reconstructed. The mineralization time, hydrocarbon accumulation and destruction time can be determined for the sulfide, bitumen and other key hydrothermal minerals dating by isotopic geochronology; based on the study of the spatial superposition relation between the lead-zinc deposits and the ancient oil-gas reservoirs, the temporal and spatial distribution relationship between the lead-zinc deposits and the ancient oil- gas reservoirs are established. This research will reveal the role of organic hydrocarbons during the migration and accumulation of ore-forming fluids and built genetic relationship between ancient oil-gas reservoirs formation-destruction and lead-zinc deposit mineralization, and determine the key factors of controlling the spatial location of the ancient oil-gas reservoirs and lead-zinc deposits. This research will provide a scientific support to comprehensive forecast and coordinative exploration for both lead-zinc deposit and oil-gas reservoir.

铅锌矿与油气藏在空间上的密切共生关系，说明成矿与成藏具有密切的成因联系。该研究以四川盆地西南缘汉源地区灯影组中铅锌矿和古油气藏作为重点解剖对象，将石油地质学中有机流体的运移、聚集、成藏研究思路引入到铅锌成矿的研究中，揭示成矿流体的性质、来源、运移路径和可能的成矿过程。通过沥青和烃源岩生物标志化合物对比研究，确定古油气藏中有机流体的来源，重建有机流体的运移、聚集成藏-破坏过程。通过对硫化物、沥青和其它关键热液矿物的同位素年代学定年，确定成矿时间和古油气藏的成藏-破坏时间；结合铅锌矿与古油气藏空间叠置关系研究，建立铅锌矿与古油气藏的时空配置关系。该项研究将揭示古油藏和古气藏中有机烃类在成矿流体的运移、聚集成矿中所起的作用，建立油气成藏-破坏与铅锌成矿间的成生关系，确定控制古油气藏和铅锌矿空间定位的关键因素。该项研究将为铅锌矿和油气藏的有效综合预测和协同勘探提供科学依据。

MVT铅锌矿与古油气藏在空间上的密切共生、伴生关系，说明成矿与成藏间具有密切的成因联系。本项研究通过对铅锌矿与古油气藏的时空关系、成矿流体性质、成矿物质来源和成矿成藏过程解剖，揭示了MVT铅锌矿的成矿与油气成藏间的耦合关系。. 研究表明，汉源地区MVT铅锌矿和沥青主要赋存于灯二段和麦地坪组古岩溶带内，二者在空间上相互叠置共生。形成古油气藏的油源和形成铅锌矿的矿源均来自于寒武系筇竹寺组烃源岩。石油不仅是研究区成矿金属元素的搬运介质，同时也是初始的成矿流体。在古油藏向古气藏转换过程中，成矿流体由初始的富含金属元素的有机流体向油田卤水演变。从闪锌矿和石英的流体包裹体揭示成矿流体为具有油田卤水性质的低温、中等盐度、富含有机物的超压流体；在成矿作用过程中成矿流体曾发生过减压降温。Zn同位素揭示成矿流体具有从团宝山向唐家山和雪区运移的特征。由同位素年代学揭示成矿作用发生于202 Ma时期，古气藏形成于205 Ma时期。. 首次提出MVT铅锌矿的成矿与古油藏向古气藏的转换、超压古气藏的减压调整成藏具有密切的成因联系。研究表明，随着富含金属元素的烃源岩的深埋，有机质开始成熟形成石油。烃源岩中的金属元素与石油中的有机物结合形成金属-有机络合物，并随同石油一同运移、聚集和成藏。随着古油藏的深埋，古油藏向古气藏转换形成超压气藏和沥青，金属-有机络合物间的结合键断裂造成金属元素与有机物的脱耦分离；与此同时，石油热裂解和TSR反应形成了大量的H2S，金属元素与H2S溶解于古气藏下伏的油田卤水中，形成富含金属元素和H2S的超压成矿流体。当超压古气藏发生减压调整成藏时，富含H2S和金属元素的成矿流体向上运移到古气藏中，由于减压降温导致金属硫化物的结晶沉淀形成MVT铅锌矿，从而造成铅锌矿与古气藏和沥青在空间上密切共生和伴生。. 本项研究成果将为MVT铅锌矿和油气藏的综合预测和协同勘探提供科学依据。.