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的碳酸盐骨骼的原始生物体特异性微结构的再结晶是成岩作用叠加的明确指示。反映重结晶作用的显微构造数据对于评价从碳酸盐岩化石中获得的地球化学代用指标以重建环境条件具有重要价值。通过电子背散射衍射（EBSD）可以测量微观结构及其变化的定量数据。EBSD允许矿物相和晶粒的晶体取向、晶粒形态、晶界取向和晶体的内部镶嵌结构的亚微米分辨率映射。因此，该方法提供了必要的原始和再结晶的微观结构的定量评估。在CHARON的第一个资助期内，提案人小组为化石微观结构的定量分析奠定了基础。在第二个资助期内，将采取两种方法：（1）从地质实验室分析化石：具有良好成岩历史特征的盆地，以及（2）基于实验室的热液蚀变的动力学时间-温度系列。我们的目标是获得一个定量的相关性的成岩地热流的矿物学和地球化学成分和碳酸盐岩化石的微观/中观结构状态的研究选定的盆地。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.