Collaborative Research: Fine-scale crustal accretion processes and rates of magma supply and replenishment at the southern Juan de Fuca Ridge neovolcanic zone

合作研究：胡安德富卡海岭新火山带南部的精细地壳增生过程以及岩浆供应和补充速率

• 批准号: 1313862
• 负责人: Julie Bowles
• 金额: $ 2.29万
• 依托单位: University of Wisconsin-Milwaukee
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2012
• 资助国家: 美国
• 起止时间: 2012-09-01 至 2015-03-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1313862&HistoricalAwards=false
• 关键词: Collaborative; Research; Fine; scale; crustal

A great deal has been learned about ridge morphology, volcanism, and magmatic processes since the advent of seafloor observation, yet fundamental finer-scale crustal accretion processes and their rates remain largely unknown. This proposal leverages recent technological and methodological developments to quantify the spatial, morphological, and geochemical variance within the neovolcanic zone of three segments of the intermediate-spreading southern Juan de Fuca Ridge (JdFR) to evaluate five hypotheses about crustal accretion and melt supply: Hypothesis 1: Crustal accretion at intermediate-spreading ridges is episodic on timescales of decades to hundreds of years. Hypothesis 2: Crustal accretion is distributed across the 8km width of the JdFR neovolcanic zone. Hypothesis 3: Crustal accretion at intermediate-spreading ridges is mainly accomplished during infrequent large-volume, large-effusion-rate eruptions rather than the more common small-volume small-effusion-rate eruptions. Hypothesis 4: Magma reservoir replenishment occurs on ~decadal time scales at normal ridge segments, but ~millennial timescales at inflated segments.Hypothesis 5: Source compositions are more variable than melting processes at intermediate rate ridges.To evaluate these hypotheses, we propose a synthesis of our time-constrained geologic and volcanologic data for each segment to assess how their structural and magmatic evolution has fluctuated over thousands of years. We propose high-precision trace element and radiogenic isotope analyses to integrate geochemical and morphological variability with seismological observables to assess crustal-level magma replenishment rates and differentiation. We propose uranium-series analyses for the dual purpose of supplementing eruption age constraints and evaluating how mantle-melting processes compare between adjacent ?inflated? and ?normal? ridge segments. We also propose to use targeted magnetic paleointensity measurements to measure ages when neither radiocarbon nor U-series will work. This proposal brings two early career researchers Brian Dreyer and Julie Bowles further into mid- ocean ridge science with the guidance of two senior scientists, Clague and Gill. Undergraduate student will be involved in laboratory training, data analysis and interpretation, and presentation of results. Results and public outreach items will be posted on the Submarine Volcanism Project webpage at http://www.mbari.org/volcanism. Our results are particularly significant for Axial Seamount as it is a terminus for the regional cabled ocean observatory of the Ocean Observatories Initiative (OOI) designed to address fundamental questions key to understanding the evolution of oceans and submarine volcanoes over the next 25-30 years. Our proposal complements that objective because it develops the volcanological and geological understanding of how the magmatic system arrived at its present configuration over the last several decades to millennia. This proposal supports the major objectives of both the Marine Geology and Geophysics and Ridge2000 Programs. Dissemination of high-resolution (1-m) bathymetric and geologic maps, volcanologic histories, and geochemical and geomagnetic data for CoAxial segment, Axial Seamount, and northern Cleft segments will offer an unparalleled view of the processes that shape the mid-ocean ridge system, providing context and developing synergic interaction among the ridge science community.

自海底观测出现以来，人们对海脊形态、火山活动和岩浆过程有了很多了解，但基本的更精细尺度的地壳增生过程及其速率仍然很大程度上未知。该提案利用最新技术和方法的发展来量化中间扩张南部胡安德富卡海岭 (JdFR) 三个部分的新火山带内的空间、形态和地球化学变化，以评估关于地壳增生和熔体供应的五种假设： 假设 1：中间扩张山脊的地壳增生是间歇性的 时间尺度为数十年至数百年。假设 2：地壳增生分布在 JdFR 新火山带 8 公里宽的范围内。假设3：中扩张脊的地壳增生主要是在罕见的大体积、大渗流率喷发过程中完成的，而不是更常见的小体积、小渗流率喷发过程。假设 4：正常山脊部分的岩浆库补给发生在约十年的时间尺度上，而在膨胀的部分则发生在约千年的时间尺度上。假设 5：源成分比中等速率山脊的融化过程变化更大。为了评估这些假设，我们建议对每个部分的时间受限的地质和火山数据进行综合，以评估其结构和火山学数据。 岩浆演化经历了数千年的波动。我们提出高精度微量元素和放射性同位素分析，将地球化学和形态变异性与地震观测值相结合，以评估地壳水平岩浆补给率和分化。我们提出铀系分析的双重目的是补充喷发年龄限制并评估相邻“膨胀”之间的地幔熔化过程如何比较。和？正常？山脊段。我们还建议使用有针对性的磁古强度测量来测量放射性碳和 U 系列都不起作用的年龄。该提案使两位早期职业研究人员布莱恩·德雷尔和朱莉·鲍尔斯在两位资深科学家克莱格和吉尔的指导下进一步进入大洋中脊科学。本科生将参与实验室培训、数据分析和解释以及结果展示。结果和公共宣传项目将发布在海底火山项目网页上：http://www.mbari.org/volcanism。我们的研究结果对于轴向海山特别重要，因为它是海洋观测计划 (OOI) 区域有线海洋观测站的终点站，旨在解决了解未来 25-30 年海洋和海底火山演化的关键基本问题。我们的建议补充了这一目标，因为它发展了对岩浆系统在过去几十年到几千年如何达到目前配置的火山学和地质学理解。该提案支持海洋地质学和地球物理学以及 Ridge2000 计划的主要目标。传播同轴段、轴海山和北裂段的高分辨率（1米）测深和地质图、火山学历史以及地球化学和地磁数据，将为塑造洋中脊系统的过程提供无与伦比的视角，为洋中脊科学界提供背景并发展协同互动。