Emplacement of the 1991 Ignimbrite at Mount Pinatubo, Philippines: Evaluation of Present Ideas on Deposition from Pyroclastic Flows

本研究是对菲律宾Pinatubo山1991年火成岩的各种相进行粒度测定和碎屑形态学的制图、取样和分析。利用磁化率各向异性（AMS）对火成岩主体进行结构研究。主要目的是为了更好地了解该矿床的岩相和相组合、侵位机制以及火山碎屑流的性质。这些信息将被放入3.5小时高潮的严格限制的时间框架中，将为目前火山学中关于火山碎屑流的性质和沉积机制的频谱的争论提供急需的线索。这项研究还将提供有关1991年火山喷发期间产生的共烟灰数量的信息。如果没有对烟灰的详细研究，火山碎屑流侵位模型将继续超过已经详细探索的实际例子所提供的信息量，在这方面，新的大型皮纳图博矿床的结果的价值不应丧失。

9419111 Self This study is to map, sample, and analyze by both granulometry and clast morphology the various facies of the 1991 ignimbrite at Mount Pinatubo, Philippines. Fabric studies of the main body of the ignimbrite by anisotropy of magnetic susceptibility (AMS) will also be undertaken. The main aim is to better understand the lithofacies and facies association of the deposit, its emplacement mechanisms, and the nature of the pyroclastic flows. The information, which will be put into the well-constrained temporal framework of the 3.5-hour-long climax, will shed much-needed light on the current debate in volcanology concerning the nature of, and the spectrum of deposition mechanisms from, pyroclastic flows. The study will also provide information on the amount od co-ignimbrite ash generated during the 1991 eruption. Without detailed studies of ignimbrites, models of pyroclastic flow emplacement will continue to outstrip the amount of information available from actual examples that have been explored in detail, and in this regard the value of results from the new, large Pinatubo deposit should not be lost.