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

该提案寻求支持pi参与国际合作的样品地球化学调查，目前在日本Unzen科学钻探项目（USDP）的第一阶段获得。USDP是国际大陆钻探计划（ICDP）的一个发展项目，该计划旨在利用钻探作为一种工具来促进对大陆地壳基本过程的理解。美国通过国家科学基金会（National Science Foundation）是ICDP的主要合作伙伴和资金来源。USDP的目标是了解云仙火山的喷发行为，作为一类重要的安山岩弧火山的代表。这项工作将通过钻井、钻孔观察和岩心分析等项目来完成，并辅以正在进行的地表地质和地球物理研究，以及最近火山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测。这一灾难性事件发生在1991年至1994年，夺去了44人的生命，造成了大约20亿美元的损失。在该项目的第一阶段，通过本提案要求提供支持，为了获得火山活动的完整物理和化学记录，正在向大厦的底部钻750米和1500米的侧面孔。同时，为了得到这项要求的支持，将对第二阶段进行规划，其中将获得通过该管道的多个岩心段，以解决岩浆输送和脱气问题。这些观察结果将有助于理解富水岩浆喷涌喷发的悖论。这项工作的总体科学依据和计划已在提交给国际开发署的提案中提出，并将在这里以简明的形式重复以提供背景。ICDP本身只支持钻井，不支持相关的科学，因此需要这个请求。最近的Unzen火山、Pinatubo火山和Soufriere火山的喷发生动地证明了将基性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。这些事件的高可见度有助于加强火山和深部岩石工作者之间的对话，并重振对基性飞地和不平衡斑晶组合的研究。一个基本的问题已经变成：我们如何将这些岩浆系统开放系统行为的产物，由镁质补给或补充产生，与地壳深部作用和火山作用的更广泛图景相结合？这个提议试图回答的这个问题的一个子集是：地壳岩浆系统中重复的基性输入的长期岩石学后果是什么？迄今为止的研究已经阐明了单个事件的喷发产物样本，或者以基性和硅质层状侵入体（MASLI）的形式观察了许多此类事件的最终产物。我们希望研究云仙火山爆发50万年的时间序列，以描述对该系统的输入，并了解它们对其化学演化的影响。这项工作将与日本在确定序列年代和记录火山地质和化学演化方面的补充工作相协调。

EichelbergerEAR-0106834This 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.