I'm currently trying to determine the formational thermal gradient around a latest-Cretaceous thrust fault by using illite crystallinity measurements. This normally wouldn't be a problem, except the rocks in the field area are lower-greenschist facies shales and slates; the rocks are very hard. I was wondering if anyone knew how to prepare a sample for XRD analysis from the well-consolidated rocks that would (ideally) leave only illite and remove all the quartz, chlorite, and other minerals. Any ideas, suggestions, or comments are welcome. Thanks.
GeologyRocks