Relationships between melt-induced rheological transitions and finite strain: observations from host rock pendants of the Tuolumne Intrusive Suite, Sierra Nevada, California

摘要

Albertz (2006) presented a study of strain and host rock rheology around the Tuolumne batholith, an area in which my colleagues and I have worked for a number of years. I am concerned about the following points raised by Albertz (2006). There are repeated statements in the paper (e.g., page 1431) that strain "drastically" or "abruptly" increases towards the margin of the Tuolumne batholith and more specifically that on average "strain intensities increase from ca. 43% to ca. 70-85%" (Fig. 7A). I have seen little to no evidence for such a strain increase anywhere around the southern, eastern, and northern margins of this batholith. Furthermore, I do not think the data presented by Albertz support such statements. Albertz (2006) acknowledges that strain is a function of rock type, as is well shown by his data in Figs. 3, 6, and 7. In fact, Fig. 7a and b nicely show that regional strain well outside the aureole of the Tuolumne batholith ranges from almost 0% shortening to 70% shortening along the z-axis, with most results falling between 30% and 60% shortening.