Can Scanned Cathodoluminescence (SEM-CL) of Quartz Silt be Applied to Provenance Studies of Mudstones? A Feasibility Study

0073995希伯有记录的地球历史大部分都包含在泥岩和页岩中，它们是大陆陆块风化和侵蚀产生的细粒沉积物。 然而，泥岩是人们最不了解的沉积岩类型，从它们中提取信息很困难。 沉积物研究的一项基本任务是确定物源，即岩石的成分是如何产生并到达沉积地点的。 虽然我们有相当复杂的方法来处理砂岩，但泥岩的细粒度长期以来一直无法详细解读其历史。粘土矿物是泥岩的主要成分，不幸的是，它们的化学性质不稳定，在埋藏和成岩作用期间会发生重大变化。 因此，很难在事后确定原始粘土矿物是什么以及它们来自哪里。碎屑石英颗粒是第二丰富的，并且具有很强的化学和机械抗性。 在原则上，他们将是一个保存完好的种源记录检查的理想组成部分，但在过去，他们只显示有限的承诺的种源studies.The扫描阴极发光（SEM-CL）的最新发展，使我们能够观察到以前未被识别的纹理特征的石英颗粒。 其应用于沉积物的主要烃源岩（深成岩、火山岩、变质岩）强烈表明，可以通过SEMCL下可见的纹理特征区分不同条件下产生的石英颗粒。 这为深入研究沉积颗粒创造了新的机会。 由于它允许检查小颗粒，如石英粉砂颗粒，它具有潜力的泥岩的物源研究。 对晚泥盆世泥岩中石英粉砂的扫描电镜-化学发光（SEM-CL）研究表明，与变质石英、深成石英和火山石英有关的结构仍然清晰可辨，SEM-CL很可能成为研究泥岩的重要工具，这是系统研究与烃源岩有关的SEM-CL特征的第一步。 我们希望开发标准，区分变质，深成，火山石英颗粒的SEM-CL功能的基础上，然后检查如何可靠地保留这些功能槽土壤形成和沉积过程。 一旦这一技术的应用有了坚实的基础，它将成为研究各种含石英沉积岩的重要工具。 由于沉积记录是如此强烈的泥岩为主，了解其石英成分的起源将大大有助于合理解释的地质记录。 我们的SEM-CL在变质，深成和火山石英的功能目录也应该刺激研究火成岩和变质岩石学家的过程和原因背后的这些功能，并导致新的见解火成岩和变质岩的起源。 由于观察到的SEM-CL特征反映了火成岩和变质岩形成过程中发生的基本过程，因此这项研究的结果也适用于其他世界岩石的研究。 具体来说，它们可能提供解释石英颗粒的新方法，这些石英颗粒很有可能在不久的将来从火星上取回。

0073995SchieberMost of recorded earth history is contained in mudstones and shales, fine-grained sediments derived from weathering and erosion of continental landmasses. Yet, mudstones are the least understood sedimentary rock type, and extracting information from them is difficult. A basic task in the study of sediments is the determination of provenance, meaning how the constituents of a rock originated and got to their site of deposition. Whereas we have quite sophisticated ways of doing this for sandstones, the fine grain size of mudstones has long defied efforts to decipher their history in detail.Clay minerals, the dominant constituent of mudstones, are unfortunately chemically labile and altered substantially during burial and diagenesis. As a consequence, it is very difficult to determine after the fact what the original clay minerals were and where they came from. Detrital quartz grains are second in abundance, and are chemically and mechanically very resistant. In principle they would be the ideal component to examine for a well-preserved provenance record, but in the past they only showed limited promise for provenance studies.The recent development of scanning cathodoluminescence (SEM-CL) allows us to observe previously unrecognized textural features in quartz grains. Its application to principal source rocks (plutonic, volcanic, metamorphic) of sediments strongly suggests that quartz grains that originate under different conditions can be differentiated through textural features visible under SEMCL. This has created new opportunities for the in depth examination of sedimentary particles. Because it allows the examination of small particles, such as quartz silt grains, it has potential for the provenance study of mudstones. Examination of quartz silt in Late Devonian mudstones by SEM-CL shows that textures related to metamorphic, plutonic, and volcanic quartz are still recognizable, and that it is very likely that SEM-CL could become an important tool in the study of mudstones.This study is the first step in a systematic study of source rock related SEM-CL features. We want to developing criteria by which to differentiate metamorphic, plutonic, and volcanic quartz grains on the basis of SEM-CL features, and then examine how reliably these features are retained trough soil forming and sedimentary processes. There is very good potential that once there is a solid foundation for the application of this technique, SEM-CL will become a very important tool in the study of all kinds of quartz bearing sedimentary rocks. Because the sedimentary record is so strongly dominated by mudstones, understanding where its quartz component originates will contribute greatly to a sensible interpretation of the geologic record. Our catalog of SEM-CL features in metamorphic, plutonic, and volcanic quartz should also stimulate research by igneous and metamorphic petrologists into processes and causes behind these features, and lead to new insights into the origin of igneous and metamorphic rocks. Because the observed SEM-CL features reflect fundamental processes that occur during the formation of igneous and metamorphic rocks, the results from this study should also be applicable to the study of rocks from other worlds. Specifically, they may provide new ways of interpreting quartz grains that will in all likelihood be retrieved from Mars in the near future.