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

OCE-RIG：基于橄榄石熔融包裹体成分的戈尔达海岭地壳和地幔过程

• 批准号: 1524247
• 负责人: Virginia Dorsey Wanless
• 金额: $ 9.9万
• 依托单位: Boise State University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-08-01 至 2018-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1524247&HistoricalAwards=false
• 关键词: OCE; RIG; Crustal; Mantle; Processes

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.

该项目的目标是确定大洋中脊洋壳内岩浆结晶的深度和分布。在形成洋壳的岩浆结晶过程中释放潜热是热量从地球内部转移到海洋和大气的主要机制，它驱动着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在哪里以及岩浆如何分布到洋壳中，对于我们作为一个整体理解全球地球化学循环和大洋中脊系统至关重要。该项目将为博伊西州立大学(BSU)的研究生和本科生提供资金和研究经验，其成果将被纳入博伊西州立大学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散速度、脊轴形态和岩石圈厚度的变化如何影响戈尔达岭沿线的结晶深度和岩浆成分。研究人员将利用橄榄石熔体包裹体的主要、微量和挥发性成分来解决与熔融和结晶有关的三个问题：(1)结晶深度如何沿着戈尔达岭变化，这表明岩石圈厚度有什么变化？(2)岩浆成分和熔融体系学是否与脊部形态有关？(3)北戈尔达之下的熔融体系和结晶深度与胡安德富卡山脊的裂隙段相比如何？为了解决这些问题，研究人员将使用从挥发分得出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，将使用常量元素和微量元素浓度来确定岩浆成分沿山脊轴线的变化。这些结果将被合并到数值计算中，以确定地幔来源成分和总熔融程度如何沿轴变化。最后，结晶深度和熔融模型将与以前对来自各种海脊的熔融包裹体的研究进行比较，以确定扩张速度、岩浆供应和岩石圈厚度的变化如何影响大洋中脊下的熔融和结晶。