Characterization of Quartz Coarse Silt Using Laser Micro- probe and Objective Cathodoluminesence

不同源岩提供的石英沉积物可根据其物理化学性质进行表征。两者都被用来评价石英砂的来源，尽管强调了石英砂的物理性质。化学性质已被用来表征整个沉积物样品(沉积物粒度和矿物组成的混合物)或单一矿物成分的多个颗粒，但一般不是单个颗粒，特别是细粒石英。用主观阴极发光(CL)岩相学观察到的间接化学性质适用于单个砂粒，但通常不适用于较细的石英颗粒。石英粗粉砂岩是泥岩的重要组成部分。这项初步研究的目的是表征这些细颗粒上以前没有确定的石英的属性。LAMA激光显微探头和客观CL岩相学将用于记录单一排水系统中从不同源岩中释放出来的石英粗粉砂的特征。将从詹姆斯河流域的几条一级溪流中收集石英粗粉砂，每条溪流排干一块已知的源岩。每个来源的石英沉积物以及源岩中的石英将使用这两种技术进行表征。因此，这种石英的指纹可以归因于特定的源岩。这项初步研究有两个直接和主要的应用。首先，证明这些技术能够识别石英沉积物的源岩，这将使进一步的研究能够确定造成现代泥质环境的主要岩性，这是一个目前正在辩论的问题，但可能无法用目前常用的工具解决。其次，由于这些技术分析的特征不会受到成岩过程的影响，如果能够证明源岩类型具有独特的和可预测的特征，它们就有可能评价泥岩中的粉砂来源。

The quartz sediment provided by various source rocks can be characterized on the basis of physical and chemical properties. Both have been used to evaluate the sources of quartz sand although the physical properties have been emphasized. Chemical properties have been used to characterize whole sediment samples (a mixture of sediment size and mineral composition) or multiple grains of a single mineral component but generally not for individual grains and specifically not for fine-grained quartz. Indirect chemical properties observed using subjective cathodoluminescence (CL) petrography is applied to individual sand grains, but generally not for the finer quartz grains. Quartz coarse silt is an important component of mudrocks. The purpose of this pilot study is to characterize attributes of quartz not previously determined on these fine particles. LAMMA laser microprobe and objective CL petrography will be used to document characteristics of quartz coarse silt liberated from various source rocks in a single drainage system. Quartz coarse silt will be collected from several first order streams each draining a single known source rock in the James River drainage basin. This quartz sediment from each source as well as the quartz in the source rock will be characterized using the two techniques. This quartz, thus fingerprinted, can then be attributed to specific source rocks. There are two immediate and major applications of this pilot study. First, demonstration of the ability of these techniques to identify source rock of quartz sediment will allow further studies to determine the dominant lithologies contributing silt to modern muddy environments, a topic presently debated but possibly not solvable with the commonly used tools at present. Second, because the characteristics analyzed by these techniques are not expected to be affected by diagenetic processes, they have the potential to evaluate the sources of silt in mudrocks if it can be shown that source rock types have unique and predictable characteristics.