Quantification of diagenetic overprint processes of fossil carbonate skeletons derived from geological laboratories and from hydrothermal alteration experiments

海洋无脊椎动物化石碳酸盐骨架的原始生物特异性微观结构的再结晶是成岩叠印的明确指示。反映重结晶作用的微结构资料，对于评价碳酸盐岩化石地球化学指标、重建环境条件具有重要价值。电子后向散射衍射（EBSD）技术可以测量材料的微观结构及其变化。EBSD允许亚微米分辨率的矿物相和晶粒的结晶取向、晶粒形态、晶界取向和晶体内部镶嵌结构的测绘。因此，该方法提供了必要的定量评估原始和再结晶的显微组织。在CHARON的第一个资助期，提案人的小组为化石微观结构的定量分析奠定了基础。在第二个资助期，将采取两种方法：(1)分析地质实验室的化石：具有良好成岩历史特征的盆地；(2)基于实验室的热液蚀变动力学时间-温度序列。我们的目标是获得经过充分研究的盆地的成岩地热热流与碳酸盐化石的矿物学和地球化学组成以及微/中构造状态的定量相关性。选定的自然实验室分别覆盖50°C、100-120°C、150-200°C和高达350°C的区域温度场。

Recrystallization of the original organism-specific microstructure of carbonate skeletons of fossil marine invertebrates is a clear indicator for diagenetic overprint. Microstructural data, which mirror recrystallization, are of great value for the assessment of geochemical proxies that are obtained from carbonate fossils for the reconstruction of environmental conditions. Quantitative data on microstructures and their changes can be measured by Electron-Backscatter-Diffraction (EBSD). EBSD allows submicrometer-resolution mapping of mineral phase and crystallo¬graphic orientation of grains, grain morphologies, grain boundary orientations, and internal mosaic structure of crystals. The method thus provides the necessary quantitative assessment of pristine and recrystallized microstructures. In the first funding period of CHARON the group of the proposer has laid foundations for the quantitative analysis of fossil microstructures. In this second funding period a twofold approach will be pursued: (1) analysis of fossils from geological laboratories: basins with a well-characterized diagenetic history, and (2) kinetic time-temperature series of laboratory-based hydrothermal alteration. We aim to obtain a quantitative correlation of the diagenetic geothermal heat flow of the selected well-studied basins with the mineralogical and geochemical composition and the micro/meso-structural state of the carbonate fossils. The selected natural laboratories cover regional temperature fields of 50°C, 100-120°C, 150-200°C, and up to 350 °C, respectively.