A Comparative Study of Fe-P Mineralization

该项目建议研究大盆地北部中生代Fe-P矿化的两个对比区域，并将它们与正在进行的密苏里州东南部元古界Fe-P矿床合作研究的结果进行比较。选定的研究区域是：(1)洪堡洛波利斯(内华达州西部)；(2)科尔特斯山脉(内华达州中部)；(3)圣弗朗索瓦山脉的花岗岩-流纹岩地体。它计划：(1)表征选定的矿床、伴生蚀变和相关的岩浆作用；(2)评价形成条件和组分来源；(3)调查相似和不同的原因。在选择性测绘和样品采集之后，将进行岩石学和地球化学工作。该项目的密苏里州部分扩展了与密苏里州DLGS和USGS的联合努力，以了解中大陆的“奥林匹克大坝”系统。放射性同位素分析(锶、钕、铅)将用于：(1)改进成矿地质年代学；(2)有助于解决成矿组分的来源和成矿机制。区域稳定同位素研究(O、H、S)和选定的放射性同位素分析将调查热液系统的时间、分布和强度及其与成矿的关系。密苏里州和内华达州的调查结合了两个正在进行的互补努力，长期目标是定量解释铁-磷矿床的成因。

This project proposes to examine two areas of contrasting Fe-P mineralization in the mid-Mesozoic of the northern Great Basin and compare them with results from ongoing cooperative studies of the Proterozoic Fe-P deposits in southeastern Missouri. Areas for selected study are: (1) the Humboldt Lopolith (western Nevada); (2) the Cortez Mountains (central Nevada); and (3) the granite- rhyolite terrane of the St. Francois Mountains. It is planned to: (1) characterize selected deposits, associated alteration, and related magmatism, (2) evaluate the conditions of formation and the sources of components, and (3) investigate reasons for similarities and differences. Selective mapping and sample collection will be followed by petrographic and geochemical work. The Missouri portion of this project extends a joint effort with the Missouri DLGS and USGS to understand mid-continent "Olympic Dam" systems. Radiogenic isotopic analyses (Sr, Nd, Pb) from well- characterized samples will be used to: (1) improve geochronometry of mineralization, and (2) help resolve sources of components and mechanisms of ore formation. Regional stable-isotope studies (O, H, S) and selected radiogenic isotopic analyses will investigate the timing, distribution, and intensity of hydrothermal systems and their relationship to mineralization. The Missouri and Nevada investigations combine two complementary ongoing efforts with the long-term aim of quantitatively interpreting the genesis of Fe-P deposits.