I work with different microstructures of marbles which probably reflect different PT conditions. I want to know approximate temperature and pressure degree.
There are calcite-dolomite-, calcite-quartz and graphite-calcite thermometers using the oxygen isotopes (see also RG). Moreover, fluid inclusion studies in combination with textural investigations of the calcite´s crystallographic and grain morphological orientation can help you shed some light on the regional metamorphic, contact metamorphic and/or dynamo-metamorphic overprinting of almost pure calcitic or dolomitic limestone using the Leigthon and Pendexter triplot classification scheme for the parent material. These should work from the unmetamorphosed calcareous sediments to the high-grade metamorphic marble and the more so for calcsilicate rocks. I used them for the low T carbonates under near ambient conditions and those limestones affected by hydrothermal alteration
HGD
Deformation microstructures can help you too. In calcite, you typically get mechanical twinning as a result of deformation. The morphology of the twins can tell you the approximate temperature the rock has been through under low T, low differential stress conditions. Type I thin twins in Calcite form at < 200C. Type II tabular thick twins form around 150-300C. Type III twins are curved, tapered, and lensoid thick twins and form at temperatures >200C. Thick patchy twins modified by dynamic recrystallization indicate temperatures >250C. If the Marble has undergone deformation at high temperatures and differential stress, if you can make ultra thin sections that basically knock off the twins. In these sections you can see microstructures related to dislocation creep (e.g. undulose extinction, deformation bands, subgrains, recrystalliztion etc.). Recystallization in calcite typically occurs above 300C.
Hi Tomáš Potočný
As suggested by other members. The best way is to use Oxygen and Carbon isotopes for this study. It can help you to understand the post depositional changes, including the diagenesis.
Here is a good reading for you.
https://www.sciencedirect.com/science/article/abs/pii/S0040195100002250
Best Regards,
SHA
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