Crustal Evolution and Recycling in a Long-Lived Transcrustal Magma System

在碰撞构造板块边界形成的火山是大规模热量和岩浆从地球内部转移到表面的重要记录。这些构造板块过程的长期变化被岩浆成分和行为随时间的演化所记录。在火山下面的岩浆系统被抬升并暴露在地球表面进行研究的地区，可以更好地了解这些过程。这项研究将通过比较加州横贯山脉暴露的岩浆时期的岩石产品，重点研究长期的岩浆演化关系和与构造过程的联系。这一地区之所以引人注目，是因为随后的构造倾斜和侵蚀暴露在地球表面的岩浆岩上，这些岩浆岩形成于一个非常长期的岩浆系统内的一系列深度上。对不同样品中的岩石和矿物化学进行比较，将使研究人员能够创建这一板块边界岩浆系统内一系列深度的岩浆演化的详细时间线。作为该项目的重要组成部分，地学本科生将从事野外和实验室数据的定性和定量分析，这将补充他们的课程工作并提供真实的研究经验。这个项目的影响将通过让一批地球科学学生参与到定量研究经验的分级序列中来扩大。这项与学生群体合作的工作的目标是使用一套影响较大的做法来提高地球科学学生的年复一年的保留率。一整套真实的研究经验将有助于建立一种支持环境，鼓励坚持不懈，并将有助于扩大STEM中代表性不足的群体。了解长期跨壳岩浆系统的演化和地壳再循环的作用是了解大陆弧动态演化的基本组成部分。在这个项目中，研究人员和学生将记录加州大陆弧倾斜和出土的横向山脉段不同风格的岩浆侵位和岩体组装，作为年龄和古深度的函数。这项研究的目的是扩大现有的原型大陆弧建筑模型，以反映在年代更久远的分层大陆地壳内建立的长寿命和脉冲弧内观察到的地壳演化和再循环过程。整个岩石和锆石颗粒将提供长期弧演化的证据，这将补充现有的基于单脉冲、高通量弧长的大陆弧模型。全岩和锆石微量元素数据作为古深度、年龄和岩体组装速率的函数将被用来描述这个大陆弧岩浆系统中地壳岩浆来源的多样性和地壳再循环的动力学。尤其是岩浆前锆石将补充全岩数据，因为不同种群的铅/铀和微量元素分析提供了地壳岩浆起源和在该大陆弧生命周期中演化的耦合年龄和矿物学记录。这一奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的智力价值和更广泛的影响审查标准进行评估，被认为值得支持。

Volcanoes formed at boundaries between colliding tectonic plates are important recorders of large-scale heat and magma transfer from Earth’s interior to it’s surface. Long-term changes in these tectonic plate processes are recorded by the evolution in composition and behavior of magmas through time. A better understanding of these processes can be achieved in areas where magma systems beneath the volcanoes have been uplifted and exposed to study on the Earth’s surface. This study will focus on long-term magma evolutionary relationships and links to tectonic processes by comparing rock products of magmatic episodes exposed in the Transverse Ranges of California. This area is remarkable because subsequent tectonic tilting and erosion have exposed on Earth’s surface magmatic rocks that formed over a range of depths within a very long-lived magma system. Comparison of rock and mineral chemistry in a variety of samples will allow researchers to create a detailed timeline of magma evolution over a range of depths within this plate boundary magma system. As an important part of the project, undergraduate geoscience students will engage in qualitative and quantitative analysis of field and laboratory data that will supplement their course work and provide authentic research experiences. The impact of this project will be broadened by engaging cohorts of geoscience students in a tiered sequence of quantitative research experiences. The goal of this work with student cohorts is to use a set of high impact practices to improve the year over year retention rate of geoscience students. The tiered set of authentic research experiences will help to build a supportive environment that will encourage persistence and will contribute to broadening of underrepresented groups in STEM.Understanding the evolution of long-lived transcrustal magma systems and the role of crust recycling is a fundamental component of understanding the dynamic evolution of continental arcs. In this project researchers and students will document diverse styles of magma emplacement and pluton assembly as a function of age and paleodepth in the tilted and exhumed Transverse Ranges segment of the California continental arc. The goal of the study is to expand upon the existing model for the architecture of the prototypical continental arc, to reflect observed processes of crustal evolution and recycling in a long-lived and pulsed arc built within much older, stratified continental crust. Whole rocks and zircon grains will yield evidence of long-term arc evolution that will complement the existing continental arc model based on single pulse, high flux arc growth. Whole rock and zircon trace element data collected as a function of paleodepth, age and pluton assembly rate will be used to describe the diversity of crustal magma sources and the dynamics of crust recycling in this continental arc magma system. Premagmatic zircons in particular will supplement whole rock data because Pb/U and trace element analyses of diverse populations provide coupled age and mineralogic records of crustal magma provenance and evolution over the life cycle of this continental arc.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.