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Abstract Details

(2020) Early Formation of Tochilinite in CM Chondrites

Enokido Y, Nakamura T, Matsumoto M & Bonal L


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01c: Room 1, Tuesday 23rd June 01:00 - 01:03

Listed below are questions that have been submitted by the community that the author will try and cover in their presentation. To submit a question, ensure you are signed in to the website. Authors or session conveners approve questions before they are displayed here.

Submitted by Aki Takigawa on Monday 22nd June 06:09
How are you convincing with that fluids forming TCIs also contacted with unaltered amorphous silicates? Can local existence of fluid explain formation of TCIs coexisting with amorphous silicates?
In our observation, only matrix amorphous silicate near the tochilinite was altered indicating the fluid migration was very limited. Therefore, we are thinking this is one of the evidence that fluid forming TCIs contacted with amorphous silicate.

Submitted by My Riebe on Monday 22nd June 12:51
How are grains with different degrees of alteration distributed in Paris? Are there clasts with different alteration degree or is it grain to grain? What is the typical size of domains with on alteration degree?
In the Paris CM chondrites, mm size clasts with different alteration degree exists. However, even in the single clast, especially in the least altered clast, alteration degree is also different in grain to grain. In this case, the grain size is 200 ?m at most.

Submitted by Sheryl Singerling on Monday 22nd June 22:47
What would have been the source for the Fe,S-rich fluid required for formation of tochilinite by precipitation? There are primary sulfides (pyrrhotite and pentlandite) present in minimally-altered CM2s that contain abundant tochilinite, so those sulfides can't really be the source. Any other possible phases that could be the source?
In the limited migration of fluids, it is hard to provide Fe and S for tochilinite formation.  From Our observation, in the partly altered matrix, the number of nano-scale Fe-sulfide (pyrrhotite and pentlandite) is relatively small compared with the non-altered matrix.  Therefore, one of the source of Fe and S for the initial alteration should be this kind of Fe-sulfide. However, the amount of nano-scale Fe-sulfide is not sufficient to form tochilinite. Therefore, we have to think other candidates as Fe, S source not only Fe-sulfide.

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