Structure and petrophysics of oceanic Crust and Lithosphere, Atlantis Massif. Study of cores from IODP Expedition 357 (CLAM)

亚特兰蒂斯地块洋壳和岩石圈的结构和岩石物理学。

• 批准号: 319238429
• 负责人: Professor Dr. Jan-Hinrich Behrmann
• 金额: --
• 依托单位: Forschungseinheit Marine Geodynamik
• 依托单位国家: 德国
• 项目类别: Infrastructure Priority Programmes
• 财政年份: 2016
• 资助国家: 德国
• 起止时间: 2015-12-31 至 2019-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/319238429?language=en
• 关键词: Structure; petrophysics; oceanic; Crust; Lithosphere

Seismic anisotropy of the Earth´s oceanic crust and lithosphere is globally observed, and usually explained by crystallographic preferred orientations (CPO) in peridotites and/or deformed gabbros. While this model may be adequate for fast-spreading at mid oceanic ridges, deformation in slow-spreading environments brings about hydration and fundamental changes in mineralogy that alters elastic properties. Here it is proposed to conduct a neutron and synchrotron diffraction study of CPO in a suite of samples from the mafic-ultramafic rocks of Atlantis Massif, to gain fundamental insight in petrophysical properties of oceanic basement in a slow-spreading environment. Atlantis Massif was drilled and cored during IODP Expedition 357, and the rocks recovered are considered an ideal test case because of its excellent exposure and structural control through the network of drillsites. Elastic constants of the protolith minerals and those of the alteration products predict an increase of elastic and, thus, seismic anisotropy with deformation and hydration. This prediction is in contrast to observations made by seismological studies pointing to lower anisotropies of slow-spreading crust than those observed in normal or fast spreading environments. To analyze and explain this important disconnect between tectonic models and seismological observations is the main motive of the planned study.

地球S洋壳和岩石圈的地震各向异性是全球观测到的，通常用橄榄岩和/或变形的辉长岩中的晶体择优取向来解释。虽然这一模型可能适用于大洋中脊的快速扩散，但缓慢扩张环境中的变形会导致水化作用和矿物学的根本变化，从而改变弹性性质。本文拟对亚特兰蒂斯地块镁铁质-超镁铁质岩石样品进行CPO的中子和同步辐射研究，以期对缓慢扩张环境下大洋基底的岩石物理性质有一个基本的认识。亚特兰蒂斯地块是在IODP 357探险期间钻探和取芯的，发现的岩石被认为是理想的测试案例，因为它通过钻探场地网络进行了良好的裸露和构造控制。原岩矿物的弹性常数和蚀变产物的弹性常数预示着随着变形和水化作用弹性各向异性的增加，从而导致地震各向异性的增加。这一预测与地震学研究的观测结果相反，地震学研究表明，慢速扩张地壳的各向异性低于在正常或快速扩张环境中观察到的各向异性。分析和解释构造模型和地震观测之间的这种重要脱节是计划中的研究的主要动机。