OCE-RIG: Crustal and Mantle Processes at Gorda Ridge Based on Olivine-Hosted Melt Inclusion Compositions

该项目的目的是确定洋中脊洋壳内岩浆结晶的深度和分布。在形成海洋地壳的岩浆结晶过程中，潜热的释放是热量从地球内部传递到海洋和大气的主要机制，它驱动了维持海底化学合成生命的热液循环。因此，确定岩浆系统中结晶发生的位置以及岩浆如何分布到海洋地壳对于我们理解全球地球化学循环和整个洋中脊系统至关重要。该项目将为博伊西州立大学（BSU）的一名研究生和本科生提供资金和研究经验，研究结果将纳入BSU的一门新的海洋地球科学课程。该项目的主要目标是确定扩展速率、脊轴形态和岩石圈厚度的变化如何影响戈尔达脊的结晶深度和岩浆成分。研究人员将利用含橄榄石的熔体包裹体的主要成分、痕量成分和挥发性成分来解决有关熔融和结晶的三个问题：(1)戈尔达岭的结晶深度如何变化，这对岩石圈厚度有何影响？(2)在岩浆组成和熔融系统上是否存在与脊形态相关的变化？(3)北戈尔达的熔融系统和结晶深度与胡安德富卡山脊的裂谷段相比如何？为了解决这些问题，研究者将使用挥发性成分的蒸汽饱和压力来确定每个熔体包裹体的结晶压力/深度。接下来，主要元素和微量元素的浓度将被用来确定岩浆成分如何沿着山脊轴变化。这些结果将结合到数值计算中，以确定地幔源成分和总熔融程度如何沿轴变化。最后，将结晶深度和熔融模型与先前对各种洋中脊的熔融包裹体的研究进行比较，以确定扩张速率、岩浆供应和岩石圈厚度的变化如何影响洋中脊下的熔融和结晶。

The goal of this project is to determine the depths and distribution of crystallization of magmas within the oceanic crust at mid-ocean ridges. The release of latent heat during crystallization of magmas that forms the oceanic crust is a primary mechanism by which heat is transferred from the Earth's interior to the oceans and atmosphere, and it drives the hydrothermal circulation that sustains chemosynthetic life on the seafloor. Thus, determining where crystallization occurs within the magmatic system and how magmas are distributed to the oceanic crust is critical for our understanding of global geochemical cycles and mid-ocean ridge systems as a whole. This project will provide funding and research experience for a graduate and undergraduate student at Boise State University (BSU) and results will be incorporated into a new marine geosciences course at BSU.The primary goal of this project is to determine how variations in spreading rate, ridge axis morphology, and lithospheric thicknesses influence crystallization depths and magma compositions along Gorda Ridge. The investigator will use major, trace and volatile compositions of olivine-hosted melt inclusions to address three questions regarding melting and crystallization: (1) How do crystallization depths vary along Gorda Ridge and what does this indicate about lithospheric thickness? (2) Are there variations in magma compositions and melting systematics that correlate with ridge morphology? (3) How do melting systematics and crystallization depths beneath North Gorda compare to the Cleft segment on the Juan de Fuca Ridge? To address these questions, the investigator will determine the pressures/depths of crystallization of each melt inclusion using vapor-saturation pressures derived from volatile contents. Next, major and trace element concentrations will be used to determine how magma compositions vary along the ridge axis. These results will be incorporated into numerical calculations to determine how mantle source compositions and total extents of melting vary along axis. Finally, crystallization depths and melting models will be compared to previous studies of melt inclusions from a variety of ridges to determine how variations in spreading rate, magma supply and lithospheric thickness influence melting and crystallization beneath mid-ocean ridges.