Collaborative Research: Origin and Significance of High Potassium Volcanism: Insights from the Ancestral Cascades, California

关于美国西部地质历史的主要科学问题之一是准确地确定内华达山脉的断层和隆起是何时开始的。这个时间是至关重要的，因为它会影响我们对特定断层应变率的理解，从而对地震危险产生影响。这个问题也很重要，因为这样的抬升与板块边界的诞生是一致的——大盆地和塞拉微板块之间的边界。人们早就知道火山活动与板块边界活动的变化有关。在这个项目中，合作小组将研究内华达山脉高钾火山活动的性质，作为这个新板块边界诞生的潜在信号。长期以来，高钾火山活动一直被视为构造活动的一个指标，但其起源仍不清楚。初步的野外和地球化学数据表明，在内华达山脉中部和加利福尼亚东部存在一个古老的喀斯喀特弧，并且在板块边界的开始和导致一系列高钾喷发的岩浆活动之间存在潜在的联系。因此，塞拉利昂中部地区提供了一个理想的地方来研究高钾岩浆岩的地球化学，以及这种不寻常的岩浆活动可能是内华达山脉分层和隆升的反映。该研究将为古喀斯喀特弧高钾岩的岩石学研究提供一个重要的、急需的地质年代学框架，并为高钾火山作用成因的三种岩石构造模式的评价提供依据。该项目在加州大学圣巴巴拉分校（UCSB）和加州州立大学弗雷斯诺分校（CSU Fresno）之间建立了研究联系，这将使来自加州州立大学弗雷斯诺分校的学生获得在研究型机构与教师和研究生密切合作的宝贵经验。科罗拉多州立大学弗雷斯诺分校是一所被指定为西班牙裔服务的RUI机构；科罗拉多州立大学弗雷斯诺地质系目前有60%的学生是女性，2006年入学的学生中有一半是女性和西班牙裔。这代表了地质学专业学生的人口结构发生了重大变化，这些学生能够参与到RUI项目中来至关重要。凯西·巴斯比博士为加州州立大学弗雷斯诺分校和加州大学圣迭戈分校的女学生提供了宝贵的导师，也是两所大学年轻女性的榜样。在这个提案中寻求学生的支持对于科罗拉多州立大学弗雷斯诺分校来说也是至关重要的，因为它是一个吸引学生进入地质学专业的招聘工具。

One of the major scientific questions regarding the geologic history of the western U.S. is to identify exactly when faulting and uplift began in the Sierra Nevada. This timing is crucial because it impacts our understanding of strain rates on particular faults, and hence has an impact on seismic hazards. The issue is also important since such uplift coincides with the birth of a plate boundary-the boundary between the Great Basin and the Sierra microplate. Volcanic activity has long been known to be associated with changes to the plate boundary activity. In this project, the collaborative team will examine the nature of high potassium volcanism in the Sierra Nevada as a potential signal of the birth of this new plate boundary.High potassium volcanism has long been looked to as an indicator of tectonic activity, but its origin remains unclear. Preliminary field and geochemical data show the existence of an ancestral Cascades arc in the central Sierra Nevada and eastern California, and a potential link between the inception of a plate boundary and the magmatism that led to a series of high K eruptions. For that reason, the central Sierra region provides an ideal place to study the geochemistry of high potassium magmatic rocks and the possibility that this unusual magmatism is a reflection of the delamination and uplift of the Sierra Nevada. The research proposed will provide an important and much-needed geologic and geochronologic framework for petrologic study of high-K rocks of the ancestral Cascades arc and enable to researchers to evaluate three petrologic-tectonic models for the origin of high potassium volcanism. This project establishes a research linkage between the University of California-Santa Barbara (UCSB) and California State University-Fresno (CSU Fresno) that will allow students from CSU Fresno to have the invaluable experience of working closely with faculty and graduate students at a research-oriented institution. CSU Fresno is an RUI institution that has been designated Hispanic serving; women currently comprise 60% of the students in the CSU Fresno Geology Department, and half of the incoming students in 2006 are female and Hispanic. This represents a significant shift in the demographics of the population of Geology majors, and it is crucial that these students are able to become involved in RUI projects. Dr. Cathy Busby provides an invaluable mentor to female students at both CSU Fresno and UCSB, and a role model for young women at both institutions. The student support sought in this proposal also is crucial to CSU Fresno as a recruitment tool to bring students into Geology.