In contrast to typical American Laboratory articles, this article presents no new material and shows little understanding on the part of the author of fundamentals of the problem addressed. The title is misleading. The fading of radiation halos from biotite at elevated temperatures has nothing to do with stress, thermal or otherwise, but rather is an atomic-scale annealing process.
Most figures also show cracks in other orientations.
His samples, therefore, contain numerous microcracks. The author is wrong stating that granites crystallize at 1200 to 2000 degrees Centigrade. Most granites and similar rocks become solid at temperatures of 650 to 850 degrees Centigrade or so, depending on pressure and chemical composition. Some form at lower temperatures. Such batholiths are composite masses of igneous rock that typically formed over tens of millions of years of emplacement of hundreds or thousands of smaller bodies of magma.