沉积盆地中金属成矿与油气成藏的耦合关系

沉积盆地中与油气密切相关的金属矿床主要包括密西西比河谷型(MVT)铅锌矿床、砂页岩型铜-铀矿床、黑色页岩中的金属硫化物矿床、沉积岩容矿的金-锑-砷-汞-铊矿床等。金属矿床与(古)油气藏在空间上的密切共生/伴生关系,暗示了二者成因上的有机联系。在许多MVT铅锌矿床和砂页岩型铜矿床中,与成矿关系密切的原油及其衍生物形成于矿化前,它们为随后的金属成矿直接提供还原硫或充当硫酸盐还原反应的还原剂。在另一些情况下,某些低温热液金属矿床,特别是Au、As、Hg、Sb、Tl矿床与油气表现出同源、同运、同聚的耦合关系,金属成矿与油气成藏同时或近同时进行。与油气具不同耦合关系的金属矿床常表现出不同的特点。与成藏和/或成矿有关的盆地流体大致可分为以碳氢化合物为主的有机流体、以含金属盐水溶液为主的无机流体以及同时富含烃类和金属组分的有机成矿流体3类,盆地中的成矿、成藏作用及其耦合关系受控于这三类流体的演化过程。沉积盆地中金属矿床与油气藏空间上密切的共生/伴生关系以及成矿、成藏过程和机理的相似性,使金属与油气矿产资源的协同勘探和综合预测成为可能。

The coupling relationship between metallization and hydrocarbon accumulation in sedimentary basins

The metallic ore deposits closely associated with hydrocarbon reservoirs in sedimentary basins mainly include the Mississippi Valley-type (MVT) Pb-Zn deposits, the sandstone-and shale-hosted Cu-U deposits, the sulfide deposits in black shales, and the sedimentary rock-hosted Au-Sb-As-Hg-Tl deposits. The intimate association suggests a genetic linkage between metallization and hydrocarbon accumulation. In many MVT Pb-Zn deposits and sandstone/shale-hosted Cu deposits, crude oil and its derivatives predate metallization and may have provided reduced sulfur directly to the ore system or acted as reductant facilitating the reduction of sulfate. Under other circumstances, metals in some low-temperature hydrothermal ore deposits, especially in sedimentary rock-hosted Au, As, Hg, Sb and Tl deposits, may originate, transport and precipitate along with hydrocarbons, suggesting simultaneous metallization and hydrocarbon accumulation. The metallic ore deposits having different coupling relationships with hydrocarbons show different characteristics. The basinal fluids associated with metallization and/or reservoir formation include hydrocarbon-rich organic fluids, metal-rich aqueous fluids, and both hydrocarbon- and metal-rich organic ore-forming fluids. Metallization, hydrocarbon accumulation and their coupling relationship in a sedimentary basin may be governed by the evolution of these fluids. The intimate association between ore deposits and hydrocarbon reservoirs and the similarity in process and mechanism for metallization and reservoir formation make it possible to carry out the coordinative exploration and comprehensive forecast of both metal and oil-gas resources in sedimentary basins.