Collaborative Research: Record of Mafic Inputs to an Arc Magma System: Analysis of Enclaves and Their Host Lavas Cored During Phase I, Unzen Scientific Drilling Program

VogelEAR-0106596本建议寻求支持私人投资机构参与对目前在日本温泉科学钻探项目(USDP)第一阶段期间获得的样品进行国际合作的地球化学调查。USDP是国际大陆钻探计划(ICDP)的一个正在开发的项目，该计划寻求将钻探作为一种工具来促进对大陆地壳基本过程的了解。通过国家科学基金会，美国是ICDP的主要合作伙伴和资金来源。USDP的目标是了解作为一类重要的安山岩弧火山代表的温岑火山的喷发行为。这将通过钻探、钻孔观察和岩心分析计划来完成，以补充正在进行的地表地质和地球物理研究，以及在最近的喷发期间进行的一系列引人注目的地球物理和地球化学观察。这一毁灭性的事件发生在1991至1994年间，夺走了44人的生命，造成了约20亿美元的损失。在该项目的第一阶段，正在向大楼底部钻750米和1500米的侧孔，以获得火山活动的完整物理和化学记录。同时，还将根据这一要求，为第二阶段进行规划，在该阶段，将通过管道获得多个岩心区段，以解决岩浆运输和脱气问题。这些观察将有助于理解富水岩浆喷发的悖论。这项工作的总体科学理由和计划载于提交人发会议的提案中，并将在此以简明的形式重复，以提供背景。ICDP本身只支持钻探，而不支持相关的科学，因此需要这一要求。最近Unzen、Pinatubo和SouFriere Hills火山的喷发以图形方式证明了将镁铁质岩浆注入地壳泥浆是一个重要的岩石学过程和火山触发因素的概念。这些事件的高能见度加强了火山岩和深成岩研究人员之间的对话，并重新活跃了对镁铁质包体和不平衡斑晶组合的研究。一个基本的问题已经变成：我们如何将这些由镁铁质补给或补给产生的岩浆系统开放系统行为的产物与地壳深成作用和火山作用的更广泛图景相适应？这个提议试图回答的问题的一个子集是：反复向地壳岩浆系统输入镁铁质会产生什么长期岩石学后果？到目前为止，研究已经阐明了喷发产物采样的单个事件或以镁铁质和硅质层状侵入体(MASLI)的形式观察到的许多此类事件的最终产物。我们希望观察500,000年的温泉喷发所提供的时间序列，以表征该系统的输入，并了解它们对其化学演化的影响。这项工作将与日本在测年和记录火山的地质和化学演化方面的补充工作相协调。

VogelEAR-0106596This proposal seeks support for the PIs to participate in internationally collaborative geochemical investigations of samples now being obtained during the first phase of the Unzen Scientific Drilling Project (USDP), Japan. USDP is a developing project of the International Continental Drilling Program (ICDP), which seeks to use drilling as a tool to advance understanding of fundamental processes of continental crust. The United States is a major partner and funding source for ICDP, through the National Science Foundation. The goal of USDP is to understand the eruptive behavior of Unzen as representative of an important class of andesitic arc volcanoes. This is to be done through a program of drilling, borehole observation, and core analysis in complement with ongoing surface geological and geophysical studies as well as the remarkable suite of geophysical and geochemical observations made during the recent eruption. That devastating episode occurred during 1991 to 1994, claimed 44 lives, and did some $2 billion in damage.In the first phase of the project, for which support is requested through this proposal, flank holes of 750 m and 1500 m are being drilled to the base of the edifice in order to obtain a complete physical and chemical record of the volcano's activity. Simultaneously, and also to be supported under this request, planning will be undertaken for the second phase in which multiple core sections through the conduit will be obtained in order to address problems of magma transport and degassing. These observations will aid in understanding the paradox of effusive eruption of water-rich magma. The overall scientific rationale and plan for this undertaking are presented in the proposals to ICDP and will be repeated in condensed form here to provide context. ICDP itself supports drilling only, not the associated science, hence the need for this request.Recent eruptions of Unzen, Pinatubo, and Soufriere Hills volcanoes have graphically demonstrated the concept that injection of mafic magma into a crustal slush is an important petrologic process and a volcanic trigger. The high visibility of these events has served to strengthen a dialog between workers on volcanic and plutonic rocks, and reinvigorated the investigation of mafic enclaves and disequilibrium phenocryst assemblages. A basic question has become: how do we fit these products of open system behavior of magma systems, produced by mafic recharge or replenishment, into the broader picture of crustal plutonism and volcanism? A subset of that question, which this proposal seeks to answer, is: What are the long term-petrologic consequences of repeated mafic inputs to the crustal magma system? Studies to date have elucidated single events as sampled by eruption products or viewed the end product of many such events in the form of mafic and silicic layered intrusions (MASLI). We wish to look at the time series provided by 500,000 years of Unzen eruptions, to characterize the inputs to the system and understand their influence on its chemical evolution. The work will be coordinated with complementary efforts in Japan on dating the sequence and documenting the geologic and chemical evolution of the volcano.