Effects of Reactive Flow & Faults in Carbonate-Hosted Lead- Zinc Ore Formations

GARVEN 9418011这项建议旨在增加我们对大规模地下水流动在地质过程中的作用的基本理解，例如碳酸盐岩中的层控矿石形成。北美古老的石灰岩-白云岩含水层中蕴藏着大量的铅、锌、重晶石和萤石矿床，这些矿床的成因似乎与10‘S和100’S的深层地下水迁移有关。在过去20年里，密苏里州东南部的一个大型矿区一直是勘探和密集地质研究的重点：奥扎克穹顶。尽管在这一背景下的地质特征和成矿条件已经揭示了很多，但关于导致成矿的地球化学反应、卤水迁移的实际路径(含水层或断层)以及导致成矿流体迁移的机制等问题仍然存在许多争议。现在，这一碳酸盐赋存矿区的地质和地球化学数据丰富。最近旨在了解盆地尺度的水文地质过程的工作表明，密苏里州的矿石可能是由于深层地下水通过欧扎克穹顶附近的前陆盆地和裂谷向上移动而形成的(Garven等人，1993)，但实际的流动模式尚未在较小的尺度上绘制(L10公里)。人们对密苏里州东南部地区的矿石沉积进行了许多地球化学模型的猜测，但还没有在包含流体流动和热传输影响的框架内测试过任何机制。这项提议的一个主要目标是使用最近开发的水文地质-地球化学模拟工具来探索和比较密苏里州东南部矿层的古水文地质学。之前美国国家科学基金会对约翰·霍普金斯大学水文地质计划的支持导致了一种新的三维有限元程序的开发，用于模拟沉积系统中地下水和热量的耦合运移。JHU的进一步研究导致了一种新的二维反应流计算机程序的开发，该程序可用于模拟地质时期的地下水化学、岩石蚀变模式和矿化作用。该提案项目将应用这些工具来测试密苏里州东南部成矿的概念模型。

Garven 9418011 This proposal seeks to increase our basic understanding of the role of large-scale groundwater flow in geologic processes such as stratabound ore formation in carbonate rocks. Ancient limestone-dolostone aquifers in North America contain significant ore deposits of lead, zinc, barite, and fluorite that appear to have origins related to the migration of deep groundwater over 10's and 100's of kilometers. A large ore district has been the focus of exploration and intensive geologic research over the past two decades: The Ozark Dome in southeast Missouri. Although much has been revealed about the geologic characteristics and conditions of ore formation in this setting, much controversy still surrounds issues such as the geochemical reactions causing ore mineralization, the actual pathways for brine migration (aquifers or faults), and the mechanisms causing migration of the ore-forming fluids. Geological and geochemical data are now abundant for this carbonate-hosted ore district. Recent work aimed at understanding hydrogeologic processes at the basin-scale has shown that the ores in Missouri were probably formed by deep groundwater moving updip through foreland basins and rifts adjacent to the Ozark Dome (Garven et al., 1993), but the actual flow patterns have yet to be mapped at smaller scales (L10km). Many geochemical models have been conjectured for ore deposition in the Southeast Missouri district, yet no mechanisms have been tested in a framework that includes the effects of fluid flow and heat transport. A primary objective of this proposal is to use recently developed hydrogeologic-geochemical modeling tools to explore and compare the paleohydrogeology of ore formation in the Southeast Missouri. Prior NSF support of the Hydrogeology Program at Johns Hopkins University has resulted in the development of a new three-dimensional finite element code for modeling coupled groundwater and heat transport in sedimentary systems. Additional research at JHU has resulted i n the development of a new two-dimensional, reactive flow computer code that can be used to simulate groundwater chemistry, patterns of rock alteration, and ore mineralization over geologic time. The proposal project will apply theses tools to test conceptual models of ore formation in Southeast Missouri.