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Arindam,

If your pesudo has been replaced by secondary minerals, when you observe your pseudo veins in thin section, you may see a rippling extinction with low birefringence. This normally indicates replacement of the melt glass/products by secondary minerals such as chlorite and serpentine.

Cheers,

Natalie Deseta

On Fri, Oct 10, 2014 at 12:42 PM, arindam sarkar <[log in to unmask]> wrote:
Respected Dr. Ernest Rutter,

                                              At first, I would like to thank you for your valuable reply and suggestion. which is very important for my doctoral study. 

                                              I hope so. Because Melt generated pseudotachylite veins are carrying evidence of one generation of shearing. Actually these veins are Pt-M. Right up this moment I can only see secondary minerals, I can not say about it's mineralogy which was at the time of it's formation. Sperulites are deformed by shearing in these pseudotachylites.
                                              
                                              Again i would like to thank you for your valuable reply.

Thank you
Regards
                              

On Fri, Oct 10, 2014 at 2:34 PM, Ernest Rutter <[log in to unmask]> wrote:
Glassy pseudotachylites often do not survive more than about 25 M yr without devitrification. Are you looking at fine-grained devitrification products?
Ernie Rutter

-----Original Message-----
From: Tectonics & structural geology discussion list [mailto:[log in to unmask]] On Behalf Of Urai, Janos
Sent: 10 October 2014 08:06
To: [log in to unmask]
Subject: Re: Problem related to Pseudotachylite

Arindam,

perhaps your samples are cataclasites or ultracataclasites, and not true pseudotachylites.

Janos Urai


On 10 Oct 2014, at 08:30, arindam sarkar <[log in to unmask]> wrote:

Respected Teachers and Dear Friends,

                                                             I am working on "Pseudotachylites" of India. I have collected lots of samples of it, appearing as dark in hand specimen. But after the preparation of the thin section, these samples are showing light color under microscope and with out microscope which are completely uncorrelatable with the hand specimen. Actually, I did not get any possible reasons of this problem.

                                          If you (group members) kindly intimate me the possible reasons or suggest me solution of this problem, I will be highly obliged.

Thank you,
Regards,
--
Arindam Sarkar
Doctoral Fellow (Ph.D.)
Centre for Advanced Studies in Geology,
University of Delhi, Delhi-7
Mob: +91 9717118391



--
Arindam Sarkar
Doctoral Fellow (Ph.D.)
Centre for Advanced Studies in Geology,
University of Delhi, Delhi-7
Mob: +91 9717118391