A Petrophysical Predictor for Degree of Serpentinzation

蛇纹石化程度的岩石物理预测

• 批准号: NE/N01684X/1
• 负责人: Sarah Davies
• 金额: $ 2.46万
• 依托单位: University of Leicester
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2016
• 资助国家: 英国
• 起止时间: 2016 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=NE%2FN01684X%2F1
• 关键词: Petrophysical; Predictor; Degree; Serpentinzation

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.

亚特兰蒂斯地块包括异质的镁铁质和超镁铁质岩石，这些岩石是慢速扩散山脊的特征。现在，沿着大西洋中部山脊形成地幔深处的岩石，因此与通常在海底发现的熔岩具有截然不同的化学反应。这些地幔岩与海水的反应称为蛇纹石化，产生甲烷，氢并产生热量，这些是可以为没有光和光合作用的生命引发生命的关键反应。国际海洋发现计划将在今年10月至12月的特定于任务的平台探险期间进行这些岩石的核心。在拟议的项目中，使用作为此探险的一部分生成的数据，我们试图调查和表征蛇形后岩石物理属性的变化。先前在同行评审的文献中的研究已经确定，在蛇纹石化期间，随着新矿物质的产生，磁化率会增加。岩石体积也增加了30％，因此岩石密度将减小。我们的项目将检验公开的假设，即磁敏感性与密度成反比，并确定是否可以将其应用于在Expedition 357期间要采样的岩石应用。我们将使用主要数据源，包括使用多传感器核心对探险的一部分，包括使用磁敏感性和从整个环内核心测量的磁敏感性和密度数据。来自核心的密度数据将通过在探险期间根据离散样本测量的水分和密度（MAD）数据补充。这些物理特性（岩石物理）数据将与薄层的岩石学分析一起评估，以鉴定有助于磁敏感信号及其模态比例的矿物质。岩石学分析将首先使用船上薄部分检查矿物学。用于引导采样的子集，用于生成抛光的，未透明的薄片，用于使用电子微探针进行分析。微型探针将是记录更改Fe-Ni氧化物相位关系的关键，而谷物尺寸较小的蛇形化度变化。通过将物理特性测量与岩性和矿物学信息相结合，我们旨在开发“蛇形化程度”的预测工具基于物理特性的预测工具，仅在物理特性数据中才能使用，该工具可以应用于物理性能数据。

项目成果

Atlantis Massif Serpentinization and Life

亚特兰蒂斯地块蛇纹石化与生命

• 发表时间: 2017
• 期刊: College Station, TX (International Ocean Discovery Program).
• 作者: Fru¨h-Green GL