A Petrophysical Predictor for Degree of Serpentinzation

亚特兰蒂斯地块由异质的镁铁质和超镁铁质岩石组成，覆盖着缓慢扩张的山脊。现在暴露在沿着这部分中大西洋海岭的岩石形成于地幔深处，因此与通常在海底发现的熔岩具有非常不同的化学性质。这些地幔岩石与海水的反应被称为蛇纹石化，产生甲烷，氢气并产生热量，这些是可以在没有光和光合作用的情况下为生命的起源提供燃料的关键反应。国际海洋发现计划将在今年12月至12月的任务专用平台Expedition 357期间对这些岩石进行取芯。在拟议的项目中，使用作为这次探险的一部分产生的数据，我们试图调查和验证岩石物理性质在蛇形化后的变化。同行评审文献中的先前研究已经确定，在蛇纹石化过程中，磁化率随着新矿物的产生而增加。岩石体积也增加了30%，因此岩石密度将降低。我们的项目将测试已发表的假设，即磁化率与密度呈负相关，并确定这是否可以应用于在远征357期间取样的岩石。我们将使用主要数据源，包括使用多传感器岩心记录仪从全圆岩心测量的磁化率和密度数据，作为远征的一部分。在考察期间，还将用离散样品上测得的水分和密度（MAD）数据来补充岩芯的密度数据。这些物理性质（岩石物理学）数据将与薄片的岩相分析一起进行评价，以确定对磁化率信号及其模态比例有贡献的矿物。岩相分析将首先使用船上的薄片检查矿物学。一个子集，用于指导采样，以产生抛光，未覆盖的薄切片，使用电子探针进行分析。微探针将是关键的记录变化的铁镍氧化物相关系的变化程度的蛇纹化的晶粒尺寸small.By整合物理性质测量与岩性和矿物学信息，我们的目标是开发一个“程度的蛇纹化”的预测工具的基础上，物理性质的输入，可应用于只有物理性质的数据是可用的情况。

The Atlantis Massif comprises heterogeneous mafic and ultramafic rocks that characterise slow spreading ridges. The rocks now exposed along this part of the Mid-Atlantic Ridge form deep in the Earth's mantle and therefore have very different chemistry to the lavas typically found at the sea floor. The reactions of these mantle rocks with seawater is known as serpentinization, produce methane, hydrogen and generate heat and these are key reactions that could fuel the initiation of life without light and photosynthesis. The International Ocean Discovery Program will core these rocks during the mission-specific platform Expedition 357 in October-December this year.In the proposed project using data generated as part of this expedition, we seek to investigate and characterise the changes in the rock physical properties following serpentization. Previous studies in the peer-reviewed literature have identified that, during serpentinization, magnetic susceptibility increases as new minerals are generated. The rock volume also increases by up to 30% and hence the rock density will decrease. Our project will test the published hypothesis that magnetic susceptibility is inversely correlated to density and determine whether this can be applied to application to rocks to be sampled during Expedition 357.We will use primary data sources, including magnetic susceptibility and density data measured from whole-round core using a multi-sensor core logger as part of the expedition. The density data from core will be supplemented by moisture and density (MAD) data measured on discrete samples also during the expedition. These physical property (petrophysical) data will be evaluated in tandem with petrographic analyses of thin sections to identify minerals contributing to the magnetic susceptibility signal and their modal proportions. The petrographic analysis will examine the mineralogy using the shipboard thin sections first. A subset used to guide sampling for generating polished, uncovered thin sections to analyse using the electron microprobe. The microprobe will be key for documenting changing Fe-Ni oxide phase relations with changing degree of serpentinization where grain size is small.By integrating physical property measurements with lithological and mineralogical information, we aim to develop a 'degree of serpentinization' predictive tool based on physical properties inputs that could be applied in situations where only physical property data is available.