Refinement of Measurement of Crystal-Mush Compaction in the Palisades Sill, New Jersey

Philpotts/Gray-0106538 这项研究的目的是直接确定的压实量，发生在凝固的帕利塞德斯西尔，新泽西，最简单的和最好的研究侵入火成岩体之一。 先前的研究表明，通过这个岩床的化学变化的一个可能的解释涉及压缩的晶体糊状物与向上排出的残留液体。 然而，证据完全是化学的，可以有其他解释。 最近对厚的洪水玄武岩流的研究表明，斜长石晶体在岩浆结晶的早期就连接在一起，形成了一个三维的链状网络。 如果在凝固过程中发生晶体泥的压实，斜长石晶体的网络会变形，其各向异性程度是压实量的直接量度。 在厚熔岩流的情况下，压实量独立确定的各向异性的斜长石网络和通过流的化学变化同意非常好。 对Palisades Sill岩石结构的初步测量表明，它们确实是各向异性的，并且从化学证据中推断的压实确实发生过。 三个新的，独立的方法已经开发用于测量岩石的各向异性的组构。 该方法涉及在定向薄片中测量斜长石网络的各个方面。 一个是基于平均截距之间的斜长石链沿着相互垂直的遍历长度;另一个考虑链中的链接作为矢量，其分布可以分析各向异性;和第三个确定的平均力矩椭圆，可以拟合到链之间的间隙补丁。 每种方法都适用于压实度和方向估计的标准误差的全面统计分析。 这些技术将用于从一系列定向样品中通过基台切割的三个相互垂直的薄切片。这些测量将使我们能够确定，对于每个样品，3-D椭球体的各向异性的岩石1 s组构，从它将被计算的数量和方向的压实。 这三种独立的压实测量方法之间的差异可以用来阐明压实过程的机理及其与岩床分层的关系。 磁化率的各向异性，这通常被用来作为一个岩石的各向异性织物的间接措施，将在每个样品中进行测量，以确定它如何涉及到斜长石链网络的各向异性。 直接测量晶体泥中的压实作用是很重要的，因为它将提供有关岩浆体分异和从部分熔融的地幔源中提取岩浆的化学和物理过程的见解。

Philpotts/Gray EAR-0106538 The goal of this research is to determine directly the amount of compaction that occurred during the solidification of the Palisades Sill, New Jersey, one of the simplest and best studied intrusive igneous bodies. Previous studies revealed that a possible explanation for the chemical variation through this sill involved compaction of crystal mush with upward expulsion of the residual liquid. The evidence, however, is entirely chemical and open to other interpretations. Recent studies of a thick flood-basalt flow have shown that plagioclase crystals link together to form a three-dimensional network of chains early in the crystallization of the magma. If compaction of crystal mush occurs during solidification, the network of plagioclase crystals is deformed, and its degree of anisotropy is a direct measure of the amount of compaction. In the case of the thick lava flow, the compaction amounts independently determined from the anisotropy of the plagioclase network and from the chemical variation through the flow agree remarkably well. Initial measurements of the fabric of rocks in the Palisades Sill document that they are indeed anisotropic and that the compaction inferred from the chemical evidence did occur. Three new, independent methods have been developed for measuring the anisotropy of a rock's fabric. The methods involve measuring various aspects of the plagioclase network in oriented thin sections. One is based on the average intercept length between plagioclase chains along mutually perpendicular traverses; another considers links in the chains as vectors whose distribution can be analyzed for anisotropy; and the third determines the average moment ellipse that can be fitted to the interstitial patches between the chains. Each of the methods is amenable to a thorough statistical analysis of the standard errors for the degree of compaction and orientation estimates. These techniques will be used on sets of three mutually perpendicular thin sections cut from a series of oriented samples through the sill. These measurements will allow us to determine, for each sample, the 3-D ellipsoid of the anisotropy of the rock1s fabric, from which will be calculated the amount and direction of compaction. Differences between the three independent methods of measuring compaction can be used to shed light on the mechanism of the compaction process and its relation to layering in the sill. The anisotropism of magnetic susceptibility, which has commonly been used as an indirect measure of the anisotropy of a rock1s fabric, will be measured in each sample to determine how it relates to the anisotropy of the plagioclase-chain network. The direct measurement of compaction in a crystal mush is of importance, because of the insight it will provide into the chemical and physical processes involved in the differentiation of magma bodies and in the extraction of magma from partly melted mantle sources.