Dear Dr. Agarwal,

it is certainly difficult to come to grips with the glassy material. Therefore I would like to direct your thoughts to the minerals in the parent or host rock amenable to Ar/Ar, K/Ar, Rb/Sr etc. dating methods and to the fault gauge abundant in phyllosilicates such as mica, using the same sort of dating techniques to obtain age data. It is not a direct dating but an indirect way to constrain the period of time during which this dynamo-metamorphic process took place.

I wish you much success.

H.G.Dill

Dear Amar,

40Ar/39Ar on carefully handpicked particles of fresh, clast-free, glassy or crypto-/microcrystalline PT groundmass should work well with modern Ar mass spectrometers. Make sure there is no wall rock material in the aliquots, which would likely produce age disturbances (older "ages") because of inherited argon.

Cheers,

Martin

If there is a suitable 'zeroing event' one could attempt OSL dating . There are number of  publications where the same has been undertaken in impact produced glasses.

Thanks a lot for all the suggestions.

Dear Amar,

Are you sure that you show us really pseudotachylyte on these 3 pictures… I see three times some kinds of mylonites at all. Micro-photo from thin section is needed for proving real “pseudos” as says my experience with pseudotachylytes. Pseudotachylyte represents dark aphanitic fault-related rock composed of friction-derived melt material interspersed with refractory clasts and crystals from the host rock. Albeit contain lithoclasts from host rocks their contacts with host rocks are sharp often.

Naturally, these mylonites you can date by Ar/Ar or Rb/Sr methods as well, but don’t mix various generations of micas = it needs good skills as everything in geology .

Best wishes,

     Milan

***************