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

Garven 9418011 这一建议旨在增加我们对大规模地下水流在地质过程中的作用的基本认识，例如碳酸盐岩中的层控成矿作用。 北美的古代石灰岩-白云岩含水层含有大量的铅、锌、重晶石和萤石矿床，这些矿床似乎与10到100公里的深层地下水迁移有关。 在过去的二十年里，一个大型矿区一直是勘探和深入地质研究的焦点：密苏里州东南部的奥扎克圆顶。 尽管对该背景下成矿地质特征和成矿条件的研究已取得了很大进展，但在成矿的地球化学反应、卤水运移的实际途径（含水层或断层）、成矿流体运移的机制等问题上仍存在很大争议。 地质和地球化学数据现在丰富的碳酸盐岩容矿区。 最近旨在了解盆地尺度水文地质过程的工作表明，密苏里州的矿石可能是由深层地下水通过前陆盆地和邻近奥扎克穹丘的裂谷向上倾斜形成的（Garven等人，1993年），但实际的流动模式还没有在较小的尺度（L10公里）映射。 许多地球化学模型已被证明是在东南部密苏里州地区的矿床沉积，但没有机制已被测试的框架，包括流体流动和热传输的影响。 本建议的主要目的是利用最近开发的水文地质地球化学建模工具，探索和比较在东南部密苏里州的成矿古水文地质。 美国国家科学基金会先前对约翰霍普金斯大学水文地质学项目的支持导致了一个新的三维有限元代码的开发，用于模拟沉积系统中耦合的地下水和热传输。 JHU的其他研究导致了一种新的二维反应流计算机代码的开发，该代码可用于模拟地质时期的地下水化学，岩石蚀变模式和矿化。 该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.