Lau Basin Vent Deposit Morphology and Composition: Links to Geologic Setting and Vent Fluid Chemistry

劳盆地喷口沉积物形态和成分：与地质环境和喷口流体化学的联系

• 批准号: 1038135
• 负责人: Margaret Tivey
• 金额: $ 23.49万
• 依托单位: Woods Hole Oceanographic Institution
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2010
• 资助国家: 美国
• 起止时间: 2010-09-01 至 2015-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1038135&HistoricalAwards=false
• 关键词: Lau; Basin; Vent; Deposit; Morphology

Intellectual merit - Vent deposits are intimately linked within paths of energy and mass transport from the mantle and crust to the oceans and provide habitats for biota. Deposit composition and morphology are linked to the composition and temperature of vent fluids, and to structural aspects of the geologic setting that control the delivery of fluids to the seafloor. In some deposits, incorporation of organisms and/or their products affects deposit evolution. Through their mineral compositions and textures the deposits, which range in age from days to hundreds of years, serve as recorders of past geologic, hydrothermal and biological activity. The goal of this proposal is to use detailed mineralogical data and textural observations combined with geochemical data (from both deposits and fluids) and geochemical modeling of transport and reaction, to determine the formation and evolution of deposits at 6 vent fields along the East Lau Spreading Center/Valu Fa Ridge. It builds on recent published work for the Lau Integrated Study Site (ISS), including information about along-axis trends in composition of the igneous substrate, vent fluid chemistry, and relationships between tectonics, volcanism and hydrothermal activity (Ferrini et al., 2008; Bezos et al., 2009; Escrig et al., 2009; Mottl et al., accepted). Initial characterization of deposits recovered in 2005 has been done, with deposit descriptions and locations relative to geologic features in Ferrini et al. (2008), and with geochemical and XRD analyses released and available through the Marine Geosciences Data System (MGDS). In 2009, additional samples were recovered (including from the recently discovered Tahi Moana vent field), filling gaps in the sample set collected in 2005, resulting in an excellent full suite of representative vent deposit samples from each vent field. Study of this sample set, and integration and synthesis of resultant data with information on geologic settings and vent fluid chemistry, will allow testing of a number of hypotheses that have been developed over the years about seafloor vent deposit formation. The gradient in the composition of the volcanic substrate and vent fluid chemistry from north to south, combined with the pronounced differences in vent fluid chemistry at the southernmost Mariner vent field, allows testing of hypotheses about extents to which deposit composition, morphology, and evolution are affected by 1) volcanic substrate composition, and 2) input of magmatic volatiles (which can result in very low pH vent fluids). Resulting models of vent deposit formation at Lau vent fields will be compared to models developed for other well-described seafloor vent deposits. Of particular interest is that the study of the vent deposits along the Lau ISS, given the range in geologic settings and vent fluid chemistry, will allow comparisons to be made globally between vent fields that exhibit many similarities, and that differ mainly with respect to a single parameter (e.g., depth or volcanic substrate composition or fluid pH or fauna). In addition to testing specific hypotheses, results of this proposal will provide important information on conditions within and on surfaces of deposits, relative fluxes of low temperature vs high temperature flow, extents to which biological activity affects deposit growth, and extents to which biological activity is recorded in the deposits. Broader Impact -This project will provide training and support for a graduate student, and opportunities for undergraduate students through the WHOI summer student fellow program. The PI will continue the types of outreach she has done in the past, including writing papers for and giving lectures to general audiences. The results of the project will be made available to the community through conferences, workshops and publications, and by submitting data and model results to the MGDS/Ridge2000 Data Portal.

智力价值——喷口沉积物与从地幔和地壳到海洋的能量和质量传输路径密切相关，并为生物群提供栖息地。沉积物成分和形态与喷口流体的成分和温度以及控制流体输送到海底的地质环境的结构方面有关。在一些矿床中，生物体和/或其产物的掺入会影响矿床的演化。这些沉积物的矿物成分和结构，其年龄从几天到数百年不等，可以作为过去地质、热液和生物活动的记录器。该提案的目标是利用详细的矿物学数据和结构观察，结合地球化学数据（来自沉积物和流体）以及输运和反应的地球化学模型，以确定东刘扩散沿线 6 个喷口区沉积物的形成和演化中心/瓦鲁法山脊。它建立在最近发表的 Lau 综合研究站点 (ISS) 工作的基础上，包括有关火成岩基质成分的沿轴趋势、喷口流体化学以及构造、火山活动和热液活动之间关系的信息（Ferrini 等，2008） ；Bezos 等人，2009 年；Escrig 等人，2009 年；Mottl 等人，接受）。 2005 年发现的矿床的初步特征已经完成，其中包括与 Ferrini 等人的地质特征相关的矿床描述和位置。 (2008)，并通过海洋地球科学数据系统 (MGDS) 发布并提供地球化学和 XRD 分析。 2009 年，回收了更多样品（包括最近发现的 Tahi Moana 喷口区），填补了 2005 年收集的样品组中的空白，从而从每个喷口区获得了全套具有代表性的喷口沉积物样品。对这个样本集的研究，以及将所得数据与地质环境和喷口流体化学信息进行整合和综合，将能够检验多年来提出的有关海底喷口沉积物形成的许多假设。从北到南火山基质成分和喷口流体化学成分的梯度，加上最南端 Mariner 喷口场喷口流体化学成分的显着差异，可以检验有关沉积物成分、形态和演化程度的假设。受 1) 火山基质成分和 2) 岩浆挥发物输入（这可能导致喷口液 pH 值极低）的影响。 Lau 喷口区喷口沉积物形成的最终模型将与为其他详细描述的海底喷口沉积物开发的模型进行比较。特别令人感兴趣的是，考虑到地质环境和喷口流体化学的范围，对刘国际空间站沿线喷口沉积物的研究将允许在全球范围内对表现出许多相似之处的喷口场进行比较，这些喷口场的不同之处主要在于单一参数（例如，深度或火山基质成分或流体 pH 值或动物群）。除了测试具体假设之外，该提案的结果还将提供有关沉积物内部和表面条件、低温与高温流的相对通量、生物活性影响沉积物生长的程度以及生物活性对沉积物生长的影响程度的重要信息。记录在存款中。更广泛的影响 - 该项目将为研究生提供培训和支持，并通过 WHOI 暑期学生研究员计划为本科生提供机会。 PI 将继续她过去所做的外展活动，包括为普通观众撰写论文和演讲。该项目的结果将通过会议、研讨会和出版物以及向 MGDS/Ridge2000 数据门户提交数据和模型结果的方式向社区公布。