Collaborative Research: The four-dimensional distribution of magmatism during the growth of lower oceanic crust: High precision U-Pb dating of IODP Hole U1473A, Atlantis Bank, SWIR

合作研究：下洋地壳生长过程中岩浆活动的四维分布：IODP孔U1473A的高精度U-Pb测年，亚特兰蒂斯浅滩，SWIR

• 批准号: 1636703
• 负责人: Michael Cheadle
• 金额: $ 10.78万
• 依托单位: University of Wyoming
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2016
• 资助国家: 美国
• 起止时间: 2016-08-01 至 2019-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1636703&HistoricalAwards=false
• 关键词: Collaborative; Research; four; dimensional; distribution

Although ocean basins make up over 70% of the Earth's surface, our knowledge of how the lower portions of the underlying ocean crust evolves over time, thickening and cooling after originating as erupting lavas in mid-ocean ridges or via thrust faulting and roll over in oceanic core complexes is poorly known. Because this material makes up the bulk of the down-going portion of the crust consumed into the mantle in subduction zones, which are the loci of the vast majority of the world's earthquakes and volcanoes, understanding the structure, composition, and evolution of this part of the crustal lithosphere is important for both scientific knowledge and disaster risk analysis. To learn more about this part of the ocean crust, a major community-driven effort to drill deep bore holes into magmatic rocks on the seafloor by the International Ocean Discovery Program, an effort involving more than 30 scientists from around the world, was carried out in 2015-2016 on the Southwest Indian Ridge at a location called the Atlantis Bank. Goals of this research are to determine the size and shape and timing of the intrusive bodies that make up the lower ocean crust, their spatial sequence, and their dimensions. Samples come from the core drilled on the recent ocean drilling leg. Samples from a previously drilled core in the general vicinity will also be analyzed and compared to those from the new hole to get an idea of the spatial continuity of the igneous intrusive bodies. To accomplish research goals, high-precision Uranium-Lead (U-Pb) dating of zircons, a mineral resistant to alteration once it is formed, will be used to provide insights into the time and space distribution of magmatism during lower crustal accretion in the ocean basins. As shown by other recent studies, these data permit the recognition of individual intrusive events that can provide constraints on the constructional dimensions and history of the lower oceanic crust and indicate the cooling rates of the intrusive bodies. Over 90 samples from the 789 meter-long core drilled into the Atlantis Bank will be analyzed using isotope-dilution thermal ionization mass spectrometry. Additional isotopic work on Hafnium in the zircons will be carried out at a sister institution in Idaho (Boise State University). Broader impacts of the work are multi-faceted and include support of two faculty and one researcher at institutions (University of Wyoming and Boise State University) in two EPSCoR states (Wyoming and Idaho, respectively) where EPSCoR indicates a state in which there is no significant federal spending compared to other states. Additional impacts include graduate student training, one of whom is an exchange student from China and involved at no cost to this award, middle and high school outreach in both Wyoming and California, and the development of new software for the integration of U-PB and trace element data. The study is also part of the large, multi-national Ocean Drilling Program and involves significant international collaboration.

虽然海洋盆地占地球表面的70%以上，但我们对下面的海洋地壳的下部如何随着时间的推移而演变，在洋中脊喷发熔岩或通过逆冲断层和海洋核心复合体的滚动后增厚和冷却的知识知之甚少。由于这种物质构成了俯冲带中消耗到地幔的地壳下行部分的大部分，这是世界上绝大多数地震和火山的所在地，因此了解这部分地壳岩石圈的结构，组成和演化对于科学知识和灾害风险分析都很重要。为了更多地了解这部分海洋地壳，国际海洋发现计划（International Ocean Discovery Program）在海底的岩浆岩中进行了一项重大的社区驱动的钻探工作，这项工作涉及来自世界各地的30多名科学家，于2015-2016年在西南印度洋脊的一个名为亚特兰蒂斯银行的地方进行。这项研究的目标是确定构成下大洋地壳的侵入体的大小、形状和时间，它们的空间序列和尺寸。 样本来自最近海洋钻探腿上钻取的岩心。还将分析附近以前钻取的岩心样品，并与新孔的样品进行比较，以了解火成岩侵入体的空间连续性。 为了实现研究目标，将利用锆石的高精度铀铅（U-Pb）定年法（锆石是一种一旦形成就不易蚀变的矿物）来深入了解海洋盆地下地壳增生期间岩浆活动的时间和空间分布。最近的其他研究表明，这些数据允许识别个别侵入事件，可以提供对下洋壳的构造尺寸和历史的限制，并表明侵入体的冷却速率。将使用同位素稀释热电离质谱法分析从亚特兰蒂斯银行钻取的789米长的岩心中采集的90多个样品。关于锆石中哈夫里的其他同位素工作将在爱达荷州的一个姐妹机构（博伊西州立大学）进行。 更广泛的影响的工作是多方面的，包括支持两个教师和一个研究人员在机构（怀俄明州和博伊西州立大学）在两个EPSCoR状态（怀俄明州和爱达荷州，分别），其中EPSCoR表明，在没有显着的联邦支出相比，其他国家。其他影响包括研究生培训，其中一名是来自中国的交换生，并参与了该奖项的免费费用，在怀俄明州和加州的初中和高中推广，以及开发新的软件，用于整合U-PB和微量元素数据。 这项研究也是大型多国海洋钻探计划的一部分，涉及重要的国际合作。