Hi Janos,
We compared the Mode I fracture response for three shales, one of which was carbonate-rich, the other two more clay-rich, and observed what you describe in the carbonate-rich shale. We did not quantify the ratio--it may not only depend on the rock mineral composition but also on cement distribution and pore geometry.
Chen, X., Eichhubl, P., Olson, J. E., Dewers, T., 2020, Salinity, pH, and temperature controls on fracture mechanical properties of three shales and their implications for fracture growth in chemically reactive fluid environments, Geomechanics for Energy and the Environment, vol. 21, article 100140. https://doi.org/10.1016/j.gete.2019.100140
Chen, X., Eichhubl, P., Olson, J. E., Dewers, T., 2019, Effect of Water on Fracture Mechanical Properties of Shales, Journal of Geophysical Research-Solid Earth. v. 124, p. 2428-2444. https://doi.org/10.1029/2018JB016479
Peter
Dr. Peter Eichhubl
Senior Research Scientist
Bureau of Economic Geology
The University of Texas at Austin
University Station Box X
Austin, TX 78713-8924
Phone: 512 475 8829
http://www.beg.utexas.edu/eichhubl
http://www.jsg.utexas.edu/peter_eichhubl
-----Original Message-----
From: Tectonics & structural geology discussion list <[log in to unmask]> On Behalf Of Janos Urai RWTH
Sent: Thursday, March 26, 2020 5:24 AM
To: [log in to unmask]
Subject: intragranular versus intergranular microfracturing in rocks
Dear colleagues,
we are studying Mode I fractures in limestone using BIB-SEM and see that the fracture is partly intracrystalline (nice flat and stepped calcite cleavage) and partly intercrystalline (broken grain boundaries and pores).
I tried to find papers about intragranular versus intergranular fracture surfaces and the ratio between intra- and intercrystalline microcracking in different rocks but was not very successful - may I ask your help in finding the relevant literature?
Thanks in advance
kind regards, Janos
Prof. Dr. Janos L. Urai
RWTH Aachen University
e-mail: [log in to unmask]
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