|The new manuscript incorporates significant changes that respond the the previous reviewer’s comments as also detailed in the author’s responses. I find that this new version much improved compared with the original submission. The manuscript is a neat, well-written and represents a novel/well documented contribution for the understanding the role of coseismic fluid infiltration in lower crustal dry rocks. This process determine a radical change in rock rheology determining an abrupt transition of dry, strong, brittle rocks to hydrous counterparts capable of ductile flow. |
I believe that the manuscript is now suitable for acceptance for publication in SE.
I have just some very minor points that I hope the authors may want to consider before the submission of the final version.
Line 14-15 – “Dislocation-free plagioclase and Kfeldspar aggregates fill the microfractures”
Comment: It is a very minor point, but for sake of clarity, considering that the authors discuss the fluid infiltration along the coseismic microfractures associated with eartquake propagation, the term “filling” may be misleading. The authors interpret the fracture “filling” as the result of the modification and repolymerization of the pseudoamorphous cataclastic material formed along the cracks derived from the host-rock feldspars. I suggest to use the term “occur” (“Dislocation-free plagioclase and Kfeldspar aggregates occur along the microfractures). In fact, across the manuscript the authors never use any more the term “filling” for the feldspar within the microfractures.
Lines 39-41 – “Furthermore, for ambient lower crustal temperatures in the range 600-700°C, the transient temperature following an earthquake may exceed 1000°C within 1 cm of the slip surface (Bestmann et al., 2012; Clerc et al., 2018). Such conditions, although short-lived, are expected to drive irreversible processes within the rock record.”
A) This part is a little “out of order”. The authors first discuss the dynamic stress field, then the thermally induced stress and finally go back to the dynamic stress. I suggest to re-order this part
B) In addition, the authors refer to the “irreversible processes” caused by the the thermal pulse associated with the frictional heating. These include thermal fracturing in addition with the annealing processes dealt with in this paper and in Bestmann et al. (2012). The authors can provide specific references to thermal shock fracturing.
C) “°C” is a unit measurement symbol. Here, and across the whole text, the authors should put a space between in front of this symbol, e.g. change 1000°C to 1000 °C.
Line 50 – “…. to a lower crustal pseudotachylyte”
Suggested editing: “ …. from a pseudotachylyte vein formed under lower crustal conditions”
Lines 72-74 – “University of Oslo’s Department of Geoscience.”
Suggested editing: “Department of Geoscience at the University of Oslo” (consistently to how the other Institutions are reported in the manuscript)
Line 111 – “At distances less than the half thickness of the pseudotachylyte (x), …”
Comment: The parameter “a” in the formula (the pseudotachylyte half vein thickness) is not defined. Please add this information.
Lines 121-22, 123-124 “…. with a mean grain size of 1.73 µm2” and “) with a mean grain size of 2.14 µm2”
Comment: as written it is not clear if the grainsize refers to the grains in the microfractures ofr to the pseudotachylyte grainseize. Please clarify.
Congratulations to the authors for such a nice piece of work