Radiogenic Isotopic Study of Diagenesis and Low-Grade Metamorphism of Pelites

泥岩成岩作用和低级变质作用的放射性同位素研究

• 批准号: 9304307
• 负责人: Donald Peacor
• 金额: $ 15.45万
• 依托单位: Regents of the University of Michigan - Ann Arbor
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 1993
• 资助国家: 美国
• 起止时间: 1993-07-15 至 1997-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9304307&HistoricalAwards=false
• 关键词: Radiogenic; Isotopic; Study; Diagenesis; Low

This research is designed to develop applications of radiogenic isotope analysis to pelitic sediments that have been affected by a wide range of fluid-mediated diagenesis through low- grade metamorphism. Although data for clay-rich sediments imply that they have a memory for fluid-rock interactions owing to their limited permeability as compared with other basin sediments, much isotope data lead to ambiguous results in part because analyzed samples are heterogeneous and contain unknown proportions of more than one generation of fine-grained clay mineral. This proposal is a renewal of our current support, in which high resolution scanning electron microscopy (STEM) is combined with isotopic analysis of equivalent pelitic rocks. The ultimate aim of these studies is to determine the timing and extent of water-pelite interactions and thus of basin- to regional-scale fluid/rock interactions. Having previously focused on Rb-Sr and development of Sm-Nk methods, we now propose to develop the 40Ar/39Ar laser technique for pelitic sediments, using well characterized samples (thin sections and separates), and other isotopic techniques to provide supporting data. We intend to determine the limitations of the methods, both with respect to spatial resolution and age. Based on our previous observations of shales and slates from a wide variety of occurrences, we have chosen to obtain data from bentonites (as standards having clays of a single origin) and shales from the Texas Gulf Coast and Welsh Sedimentary Basin, as well as other prograde sequences. The latter is representative of diagenesis in a passive marginal basin, whereas the former represents tectonically-induced dissolution and crystallization over the range of diagenesis to greenschist facies conditions. The samples from each locality represent the complete range of diagenesis through low-grade metamorphism.

这项研究旨在开发应用程序， 放射性同位素分析泥质沉积物， 受到广泛的流体介导的成岩作用的影响， 级变质作用 尽管富含粘土的沉积物的数据表明 它们对流体和岩石的相互作用有记忆， 与其他盆地沉积物相比， 同位素数据导致模棱两可结果，部分原因是分析 样本是异质的，含有未知比例的更多 比一代细粒粘土矿物。这个建议是 更新我们目前的支持，其中高分辨率扫描 电子显微镜（STEM）结合同位素分析， 相当于泥质岩石。 这些研究的最终目的是 确定水-泥质岩相互作用的时间和程度， 因此，盆地到区域尺度的流体/岩石相互作用。 以前专注于Rb-Sr和Sm-Nk的开发 方法，我们现在建议开发40 Ar/39 Ar激光技术， 泥质沉积物，使用良好表征的样品（薄切片 和分离），以及其他同位素技术来提供支持 数据 我们打算确定这些方法的局限性， 在空间分辨率和年龄方面。 基于我们之前 页岩和板岩的观察，从各种各样的 发生，我们选择了获得数据从辉长岩（作为 具有单一来源的粘土的标准）和来自 德克萨斯州墨西哥湾沿岸和威尔士沉积盆地，以及其他 重复序列。 后者是成岩作用的代表， 被动边缘盆地，而前者代表 构造诱导的溶解和结晶作用 绿片岩相条件。 的样品 每个地点都代表了完整的成岩作用范围， 低级变质作用