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: 1060986
• 负责人: Julie Bowles
• 金额: $ 4.21万
• 依托单位: University of Minnesota-Twin Cities
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2011
• 资助国家: 美国
• 起止时间: 2011-03-01 至 2013-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1060986&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.

自从海底观察出现以来，关于山脊形态，火山和岩浆过程已经了解了很多知识，但基本的较细节的地壳积聚过程和速率在很大程度上还不为人所知。该提案利用了最新的技术和方法论发展来量化中间体宣传的南部胡安·德·富卡山脊（JDFR）的三个片段的新型阶段内的空间，形态和地球化学差异1：中间山脊上的地壳积聚在数十年到数百年的时间尺度上是偶然的。假设2：地壳积聚分布在JDFR新旋转区的8公里宽度上。假设3：中间山脊上的地壳积聚主要是在不经常的大批量，大效率率的喷发中完成的，而不是更常见的小体积小效率率爆发。假设4：岩浆储层补充物发生在正常山脊段处的二十年时间尺度上，但是〜千禧一代的时间尺度在膨胀的细分市场上。我们为每个段的时间约束的地质和火山数据数据评估了数千年来它们的结构和岩浆进化如何波动。我们提出了高精度的痕量元素和放射异位素分析，以将地球化学和形态学变异性与地震学可​​观察物相结合，以评估地壳水平的岩浆补充速率和分化。我们提出了铀系列分析，以增加补充喷发年龄限制的双重目的，并评估地幔融化过程如何比较相邻的膨胀？和？正常？山脊段。我们还建议使用靶向磁性的测量值来测量当放射性碳和U系列无法正常工作时测量年龄。该提议在两位高级科学家克拉格（Clague）和吉尔（Gill）的指导下，将两名早期职业研究人员布莱恩·德雷尔（Brian Dreyer）和朱莉·鲍尔斯（Julie Bowles）进一步进入了中源山脊科学。本科生将参与实验室培训，数据分析和解释以及结果的呈现。结果和公共外展项目将发布在http://www.mbari.org/volcanism的潜艇火山项目网页上。我们的结果对于轴向海山尤为重要，因为它是海洋天文台倡议（OOI）的末端，旨在解决未来25 - 30年中海洋和海底火山进化的基本问题的关键。我们的提议补充了这一目标，因为它对岩浆系统如何达到了过去几十年来到达千年来达到目前的配置的火山学和地质理解。该建议支持海洋地质和地球物理学和Ridge2000计划的主要目标。传播高分辨率（1-M）测深图和地质图，火山学历史以及同轴段，轴向接缝和北部裂口段的地球化学和地球磁数据将提供无与伦比的视图，提供背景并在岭科学界之间发展协同互动。