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Hi Arindam,

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                             I have evidences of melting as previous literature (reported from different places of the world). In my study area, cataclastic generated pseudotachylite and melt generated pseudotachylite both are present. So there is not confusion to distinguish these pseudotachylites as cataclastic pseudotachylite and melt generated pseudotachylite.

-->in order to identify if melting took place you HAVE to do SEM analysis. Even when there is no glass (you have to check e.g. by EBSD or TEM) you have to check if there are some indirect evidence of melting, for example corona structures, droplets, embayed clasts ec.

only light microscope analysis is not sufficient: without SEM analyis you never can conclude if melting took place in your rocks.

Cheers

Michel

On 10.10.2014 14:28, arindam sarkar wrote:
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Respeced Dr. Kate Brodie,

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

Exactly Madam, it is true. I found Pt-M that means it can be assumed as mylonite. In case of this type of pseudotachylites, after making thin section, it becomes light (after reduction of it's thickness). I just want to find out this reason. But in case cataclastic pseudotachylite dark color remains same after preparing thin section. Please kindly intimate me this reason.

Again I would like to thank you for your valuable reply.

Thank you
Regards

On Fri, Oct 10, 2014 at 4:34 PM, Kate Brodie <[log in to unmask]> wrote:
Dear Arindam,
Note that ultra fine grained rock (e.g quartz cataclasites or mylonites) often appear black in hand specimen regardless of mineralogy so this is no guideline. 
Regards
Kate

From: arindam sarkar <[log in to unmask]>
Reply-To: GEO-TECTONICS <[log in to unmask]>
Date: Friday, 10 October 2014 11:07
To: GEO-TECTONICS <[log in to unmask]>
Subject: Re: Problem related to Pseudotachylite

Respected Dr. Janos Urai,

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

                             I have evidences of melting as previous literature (reported from different places of the world). In my study area, cataclastic generated pseudotachylite and melt generated pseudotachylite both are present. So there is not confusion to distinguish these pseudotachylites as cataclastic pseudotachylite and melt generated pseudotachylite.
          
                              Actually sir, I wanted to say that there is color difference between hand specimen and thin section. Hand specimens are appearing black where as thin sections are appearing light color under plane polarized light. I wanted to know if these samples appear black in hand specimen, It should also appear black under  microscope- using plane polarized light. ( I am not talking about thin section study under microscope-using crossed polars.)
                               
                             Again I would like to thank you so much for your valuable reply. 

Thank You,
Regards 


On Fri, Oct 10, 2014 at 12:35 PM, Urai, Janos <[log in to unmask]> wrote:
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



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


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