Petrologic, Geochemical, and Isotopic Investigation of Gulf Coast Salt Dome Cap Rocks

墨西哥湾沿岸盐丘盖岩的岩石学、地球化学和同位素研究

• 批准号: 8709319
• 负责人: J. Richard Kyle
• 金额: $ 10.57万
• 依托单位: University of Texas at Austin
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 1987
• 资助国家: 美国
• 起止时间: 1987-06-15 至 1990-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=8709319&HistoricalAwards=false
• 关键词: Petrologic; Geochemical; Isotopic; Investigation; Gulf

Salt dome hosted Zn-Pb-Ba-Ag deposits in the Gulf Coast Region of the United States offer unique information about the origin and evolution of metal-bearing brines and ore deposits in sedimentary terranes. The salt dome mineral deposits have genetic affinities with Mississippi Valley Type Zn-Pb-Ba deposits and sedimentary exhalative Zn-Pb-Ag-Ba deposits. Our previous studies, most of which have focused on the petrology and geochemistry of ore minerals, indicate that these deposits were apparently emplaced during and after the formation of cap rocks from relatively hot fluids leaking upward along the salt stock margins. We propose to continue our study, concentrating more on the processes of cap rock formation than ore mineral formation (1) to better establish the links between basin brines, cap rocks, and sulfide/sulfate mineral deposits, and (2) to determine what constituents in the sedimentary section or beneath the salt stock provided metals and sulfur. Detailed petrographic studies will be integrated with C, O, Sr, Pb, and S isotope, REE, and fluid inclusion studies cap rocks and associated minerals. We propose to determine the relative sequence of events that must take place in a sedimentary basin to produce salt dome mineral deposits, to characterize the nature of sulfur- and metal-bearing fluids, to investigate the isotopic relationships between anhydrite cap rocks and salt- hosted anhydrite to see what reactions involving anhydrite take place during cap rock formation, and to investigate how fluids in different salt basins may give rise to distinct isotopic signatures of salt dome cap rocks within that basin.

盐丘赋存于美国墨西哥湾沿岸地区，为沉积地体中含金属卤水和矿床的起源和演化提供了独特的信息。盐丘矿床与密西西比谷型锌铅钡矿床和沉积喷流锌铅银巴矿床具有成因联系。我们以前的研究大多集中在矿石矿物的岩石学和地球化学上，表明这些矿床显然是在盖层形成期间和之后由相对较热的流体沿盐矿边缘向上泄漏而侵位的。我们建议继续我们的研究，将重点放在盖层形成的过程上，而不是矿石的形成上：(1)更好地建立盆地卤水、盖层和硫化物/硫酸盐矿床之间的联系；(2)确定沉积段或盐岩下的哪些成分提供了金属和硫。详细的岩石学研究将结合碳、氧、锶、铅和S同位素、稀土元素以及流体包裹体研究盖层和伴生矿物。我们建议确定沉积盆地中产生盐穹顶矿床所必须发生的事件的相对序列，描述含硫和金属流体的性质，研究硬石膏盖层和含盐硬石膏之间的同位素关系，以了解在盖层形成过程中与硬石膏有关的反应。并研究不同盐盆中的流体如何产生该盆地内盐丘盖层的不同同位素特征。