Measurement of Crystal Mush Compaction in the Palisades Sill, NJ, Using Serial Sections and X-Ray CT Scans of Partly Melted Oriented Samples

9902890 Philpotts本研究的目标是量化的岩浆分异的数量，发生在一个缓慢冷却的侵入玄武岩浆片作为结晶泥压实的结果。这种差异以前只假设通过表的化学变化的基础上。然而，最近的发现，斜长石晶体集群在一起，形成一个连续的三维网络早期结晶缓慢冷却的玄武岩浆提供了一种手段，直接测量的压实量已经发生。这种网络在最初形成时具有随机结构，但在压实过程中，它可能会变形。变形网络的形状最容易在已经首先部分熔化的样品中测量，以便将后期结晶矿物转化为液体，然后可以将其淬火成玻璃。网络的形状在连续切片或CT X射线扫描中测量。在康涅狄格州厚的霍利奥克泛滥玄武岩中进行的这种测量揭示了一种压实和膨胀的模式，这种模式与通过这种流动的化学变化所指示的模式完全匹配。在目前的研究中，这些相同的技术将被应用到一个典型的分化侵入火成岩体，帕利塞兹Sill的新泽西。大量的化学研究表明，压实作用是该岩床的一个重要分异过程。在通过岩床的垂直剖面上测量斜长石网络的变形程度，将直接表明在其凝固过程中发生了多少压实。如果这些技术能成功地应用于Palisades Sill，它们可能在大型侵入岩体分异作用的研究中有广泛的应用。

9902890PhilpottsThe goal of this research is to quantify the amount of magmatic differentiation that takes place in a slowly cooled sheet of intrusive basaltic magma as a result of crystal mush compaction. Such differentiation has previously been hypothesized only on the basis of chemical variations through sheets. However, the recent discovery that plagioclase crystals cluster together to form a continuous 3-D network early in the crystallization of slowly cooled basaltic magma provides a means of measuring directly the amount of compaction that has occurred. This network, when initially formed, has a random fabric, but during compaction it can become deformed. The shape of the deformed network is most easily measured in samples that have first been partly melted so as to convert late crystallizing minerals to liquid, which can then be quenched to glass. The shape of the network is measured in serial sections or in CT X-ray scans. Such measurements in the thick Holyoke flood basalt of Connecticut have revealed a pattern of compaction and dilation that matches exactly the pattern indicated by the chemical variation through this flow. In the present research, these same techniques will be applied to a classic differentiated intrusive igneous body, the Palisades Sill of New Jersey. Numerous chemical studies have pointed to compaction having been an important differentiation process in this sill. Measurements of the degree of deformation of the plagioclase network in a vertical section through this sill will indicate directly how much compaction took place during its solidification. If these techniques can be applied successfully to the Palisades Sill, they may have wide application in the study of the differentiation of larger intrusive igneous bodies.