Sedimentary rock-hosted ore-forming systems: structural setting and paleohydrology

沉积在陆内和被动边缘盆地中的沉积岩拥有各种各样的热液矿床，这些矿床包含全球金属资源的相当大比例，特别是铅、锌、铜和金。这些矿床形成于不同的成矿系统中，随着盆地经历裂谷、沉积、碰撞、变形、侵蚀和折返的顺序阶段，这些成矿系统在不同的时期运行。成矿系统在任何阶段产生矿床的潜力在很大程度上取决于盆地的总体水文地质框架，而盆地的整体水文地质框架在很大程度上受盆地几何形状、沉积层的渗透率以及横切构造的密度、几何形状和渗透率的控制。我提出的研究计划的长期目标是评估沉积盆地及其组成沉积物的物理和化学演化如何影响产生不同类型沉积岩赋存矿藏的潜力。这将通过比较在生命周期中从沉积到折返的三个不同阶段的成矿系统来实现：(1)沉积喷流(Sedex)铅锌成矿系统，在广泛的岩化作用之前，在盆地沉积期间活动；(2)造山Au系统，在变形期间活动和伴随着被动边缘沉积物并入前陆褶皱和逆冲带而发生的低级别变质作用；(3)卡林型Au系统，在宿主被动边缘沉积物并入褶皱冲断带后近3亿年活动。我提出的研究计划将为理解被动边缘沉积盆地的演化如何影响即将形成的沉积岩容矿类型提供新的约束。该计划包括育空地区和西北地区下古生界塞尔文盆地以及横向相当的内华达州中部和东部盆地的现场。将综合广泛的地质实地观察、仔细的构造制图、地质年代学和地球化学，利用微观分析技术和地球化学成像方面的最新进展，提供关于矿床形成的水文地质框架的第一级约束。还将评估主岩的原始沉积学特征以及随后的成岩和构造演化受热液流动的控制程度，以及随后的碰撞和盆地变形阶段对早期形成的矿床的改造程度。研究结果将被用于推进沉积岩矿床的形成及其与沉积盆地生命周期的联系的概念模型，并对对社会至关重要的金属的勘探和发现产生影响。

Sedimentary rocks deposited in intracontinental and passive margin basins host a wide variety of hydrothermal ore-deposits that contain a significant percentage of global metal resources, especially lead, zinc, copper, and gold. These deposits form in a variety of ore-forming systems that operate at different periods of time as the basins progress through sequential stages of rifting, sedimentation, collision, deformation, erosion, and exhumation. The potential for ore-forming systems to generate deposits at any stage is strongly dependent on the overall hydrogeological framework of the basin, which is largely controlled by basin geometry, the permeability of sedimentary layers, and the density, geometry and permeability of cross-cutting structures. The long-term goal of my proposed research program is to evaluate how the physical and chemical evolution of sedimentary basins and their constituent sediments affects the potential for generating different types of sedimentary rock-hosted ore-deposits. This will be accomplished by comparing ore-forming systems operating at three different stages in the life cycle, from deposition to exhumation, of passive margin sediments: (1) sedimentary exhalative (SEDEX) Pb-Zn ore systems active during basin sedimentation prior to extensive lithification; (2) orogenic Au-systems active during deformation and low-grade metamorphism accompanying the incorporation of passive margin sediments into a foreland fold and thrust belt; and (3) Carlin-type Au-systems active nearly 300 million years after the host passive margin sediments were incorporated into a fold and thrust belt. My proposed research program will provide new constraints in understanding how the evolution of passive margin sedimentary basins influences the type of sedimentary rock-hosted ore-deposit that will form. The program encompasses field sites in the lower Paleozoic Selwyn Basin of the Yukon and Northwest Territories, and the laterally equivalent basin of central and eastern Nevada. First-order constraints on the hydrogeological framework under which the deposits formed will be provided by integrating extensive geological field observations, careful structural mapping, geochronology and geochemistry, taking advantage of recent advances in micro-analytical techniques and geochemical imaging. The extent to which the primary sedimentological character and subsequent diagenetic and structural evolution of host rocks is controlled by hydrothermal fluid flow and how early formed ore-deposits are modified by subsequent stages of collision and basin deformation will also be evaluated. The results will be used to advance conceptual models for the formation of sedimentary rock-hosted ore-deposits and their link to the life cycle of sedimentary basins, with implications for the exploration and discovery of metals vital to society.