Gulf Coast Basinal Mudstones: Sources or Sinks for Diagenetic Components?

泥岩构成了沉积盆地的大部分填充物，但它们是所有沉积岩中最不为人所知的。根据对其他岩石的研究，几乎所有不能轻易解释的反应都是由它们引起的。例如，它们已被认为是铅锌矿化、砂岩胶结物中SiO2、Fe++和Mg+的来源，以及砂岩地下浸出的H+的来源。墨西哥湾沿岸新生代剖面的现有资料对所有这些推论提出了质疑。利用现有的钻屑，我们提出了以下方面的变化特征：1)全岩主、次元素（如Sr、Ba、B和Li）元素和同位素（如O、Sr、B和Li）化学特征；2)碳酸盐矿物和地球化学特征；3)长石矿物和地球化学特征；4)石英形态和地球化学特征。我们将定量记录德克萨斯州南部泥岩随深度的变化，那里已经有大量砂岩岩石学、地球化学和地层水地球化学的数据。通过研究生长断裂沉积中心的倾斜剖面，我们可以最大限度地减少局部和暂时限制沉积的变幻性。该地区定量物质平衡将使我们能够评估泥岩成岩作用对沉积盆地成岩演化的重要性，并评估从下伏地层输入和向上覆地层输出的程度。

Mudstones constitute most of the fill of sedimentary basins, yet they are the least understood of all sedimentary rocks. They are "blamed" for virtually all reactions that cannot be easily explained, based on the examination of other rocks. For example, they have been advanced as sources for Pb-Zn mineralization, for SiO2, Fe++, and Mg+ in sandstone cements, and for H+ for subsurface leaching of sandstones. Currently available data in Gulf Coast Cenozoic sections dispute all these inferences. Using available drill cuttings, we propose to characterize changes in: 1) whole-rock major and minor (esp. Sr, Ba, B, and Li) elemental and isotopic (esp. O, Sr, B, and Li) chemistry, 2) carbonate mineralogy and geochemistry, 3) feldspar mineralogy and geochemistry, and 4) quartz morphology and geochemistry. We will quantitatively document changes in mudstones with depth in South Texas where extensive data on sandstone petrography and geochemistry, and formation water geochemistry, already exist. By studying a dip section through the growth-faulted depocenters, we can minimize the vagaries of local and temporally restricted sedimentation. Quantitative material balances in this area will enable us to assess the importance of mudstone diagenesis to the diagenetic evolution of sedimentary basins and assess the magnitude of import form underlying and export to overlying strata.