Collaborative Research: Crustal Overturn in Continental Margin Arcs During Magmatic Surges

俯冲带，在那里一个岩石圈板块滑到另一个板块之下，然后回到地幔，导致岩石在深处熔融，这些熔体上升，形成长长的火山和次火山深成岩链，它们一起被称为岩浆弧。由于这些弧和周围的主岩是热的，并且由于板块运动而承受着巨大的压力，它们变成了广泛变形的造山带。大陆边缘造山带及其伴生岩浆弧的演化具有非稳态性、节奏性和可塑性。俯冲、造山、岩浆作用、折返和侵蚀/再沉积。这项研究项目考察了这种节奏的细节，特别是在岩浆涌动(形成大量岩浆并添加到地壳中的时期)期间，以及容易熔融的地壳向俯冲带中发生熔融的深层地区的构造输送所起的作用。其目的是验证这一假设，即在白垩纪中期(105-85 Ma)高岩浆涌期，内华达山脉南部和萨利安地块的大部分弧被侵位在地壳尺度的对流系统中。105~85 Ma附近悬垂的初步研究表明，在岩浆作用上升过程中，变质沉积和喷流的变质火山岩主岩被对流倾覆，并经历了快速向下移动和高应变流动。这项研究将扩展和综合许多数据集(例如，野外研究、地质年代学、气压测量、垂直位移、应变场、岩浆通量)，并进行广泛的正演数值、热机械模拟，能够包括岩浆上升、粘弹塑性宿主行为、大应变、非线性流变学和现实的相变，以了解这一过程的物理学。火山喷发极大地影响人类社会，并在我们的大气形成和气候变化中发挥巨大作用。此外，造山带中的地壳变形导致了地震等短期事件和造山等长期事件，这些事件也影响着我们的社会。人们认识到，弧形地壳有时会发生倾覆，从而将地壳物质纳入上升的岩浆中，这将极大地改变对岩浆系统的理解、对这些系统的地球化学和地质年代学分析，以及地壳生长速度。这项研究将增进对这些系统的了解，并将向公众提供关于地质年代学、温压测量、垂直位移速率、应变和应变率以及岩浆流量的基于地理信息系统的数据库。来自几个机构的大量本科生将通过南加州大学团队研究计划参与研究项目

Subduction zones, where one lithospheric plate slides beneath another before returning to the mantle, results in melting of rock at depth and the rise of these melts to form long chains of volcanoes and subvolcanic plutons that together are called magmatic arcs. Because these arcs and surrounding host rocks are hot and undergoing tremendous stresses due to the plate motions they become extensively deformed forming orogenic belts. The evolution of continental margin orogenic belts and their associated magmatic arcs has a non-steady state ?tempo? of subduction, orogeny, magmatism, exhumation, and erosion/redeposition. This research project examines the details of this tempo particularly during magmatic surges (periods when large volumes of magma are formed and added to the crust) and what role was played by the tectonic transport of easily melted crust to regions at depth where melt occurs in subduction zones. The goal is to test the hypothesis that during the mid-Cretaceous (105-85 Ma) high magma surge episode much of the arc in the southern Sierra Nevada and Salinian blocks was emplaced within a crustal scale convection system. Preliminary studies of pendants around 105-85 Ma plutons indicate that, during rise of magmatism, metasedimentary and effusive metavolcanic host rocks were convectively overturned and underwent rapid downward displacement and high-strain flow. The research will expand and synthesize a number of data sets (e.g., field studies, geochronology, barometry, vertical displacement, strain fields, magma fluxes) plus perform extensive forward numerical, thermomechanical modeling capable of incorporating magma ascent, viscoelasto- plastic host behavior, large strains, nonlinear rheologies, and realistic phase transitions to understand the physics of the process.Volcanic eruptions dramatically impact human society and play a huge role in both the formation of our atmosphere and in climate change. Additionally crustal deformation in orogenic belts leads to short-term events such as earthquakes and long-term events such as mountain building that also impact our society. The recognition that arc crust, at times, undergoes overturn thus incorporating crustal materials into rising magmas will dramatically change the understanding of magmatic systems, the geochemical and geochronologic analyses of these systems, and rates of crustal growth. This research will improve understanding of these systems and the GIS based databases produced on geochronology, thermobarometry, vertical displacement rates, strain and strain rates, and magma fluxes will be made available to the public. A large number of undergraduates from several institutions will be involved in the research project through the University of Southern California Team Research program