Quantitative analyses and modelling of the microstructures associated with the (hydro)thermally activated aragonite-calcite transformation in single crystals, bivalve shells, and corals

点击翻译按钮获取中文摘要

This proposal addresses the need to identify (i) the controlling micromechanisms involved in carbonate archive recrystallization leading to diagenetically altered skeletal hardparts or carbonate cements and to (ii) quantitatively constrain their kinetics as a basis for assessing the possible effect of recrystallization on the distribution of major and minor elements and associated isotope fractionation. We aim at deriving substantial guidelines for the interpretation of microstructural records preserved in naturally altered carbonate archives and at significantly enhancing the qualitative and quantitative understanding of the role of dissolution-precipitation processes in the recrystallization accompanying the aragonite-aragonite and aragonite-calcite-transformation during diagenesis. The project specifically intends to evaluate transformation scenarios on the basis of extensive characterization of the microstructures associated with the experimentally induced aragonite-aragonite and aragonite-calcite-transformation in aragonitic corals (highly porous), aragonitic bivalve shells (porous), and aragonite single crystals (non-porous) by a range of microscopic methods, including CT-scanning, and exploratory micro-hydraulic investigations. The characterization step will initially exploit the unprecedented observational data set from Phase I of FOR 1644. This extensive data set will be complemented by tailored experimental work in the context of Phase II. The outcome of the characterization of the pore space will provide the basis for significant modelling of grain(phase)-boundary migration in carbonates in the presence of pores, solid inclusions (organic compounds etc.), and compositional gradients. The objective of the modelling is to develop a qualitative understanding as well as to quantitatively constrain kinetics of the processes dominating the evolution of experimentally altered samples. The results of the modelling will be applied to microstructural records preserved in naturally altered carbonate archives to deduce their diagenetic pathways.