Abstract Details
(2020) Depositional Environments of Neoarchean Carbonates from the Dharwar Craton, India: Constraints from Geochemical and Isotopic Studies
Govind A V, Behera K, Balakrishnan S, Dash JK, Bhutani R, Managave S & Srinivasan R
https://doi.org/10.46427/gold2020.869
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14b: Plenary Hall, Monday 22nd June 22:42 - 22:45
Vipin Govind A
View abstracts at 2 conferences in series
Kamalesh Behera View abstracts at 2 conferences in series
Srinivasan Balakrishnan View all 2 abstracts at Goldschmidt2020 View abstracts at 11 conferences in series
Jitendra Kumar Dash View abstracts at 3 conferences in series
Rajneesh Bhutani View all 4 abstracts at Goldschmidt2020 View abstracts at 10 conferences in series
Shreyas Managave View all 2 abstracts at Goldschmidt2020 View abstracts at 4 conferences in series
Ramaswamiah Srinivasan View all 2 abstracts at Goldschmidt2020 View abstracts at 2 conferences in series
Kamalesh Behera View abstracts at 2 conferences in series
Srinivasan Balakrishnan View all 2 abstracts at Goldschmidt2020 View abstracts at 11 conferences in series
Jitendra Kumar Dash View abstracts at 3 conferences in series
Rajneesh Bhutani View all 4 abstracts at Goldschmidt2020 View abstracts at 10 conferences in series
Shreyas Managave View all 2 abstracts at Goldschmidt2020 View abstracts at 4 conferences in series
Ramaswamiah Srinivasan View all 2 abstracts at Goldschmidt2020 View abstracts at 2 conferences in series
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Submitted by Kimberly Lau on Monday 22nd June 19:34
The results show extremely high Mn/Sr ratios. Do these represent carbonate-only fractions, or influence from the Mn deposits? I also wanted to ask about the interpretation for the source of the Fe-Mn deposits? Thank you!
Thanks for the question, Kim. I could not attend the Q&A because of the poor internet connectivity. Mn/Sr ratios are crucial for the determination of extent of diagenetic changes, but in case of Archean sediments Mn/Sr ratios are always pretty high and it works better in case of younger sediments. Many workers have described Archean oceans as mantle buffered as opposed to the continent buffered oceans of the present, which implies that the seawater was in close interaction with volcano-sedimentary deposits which would have a considerable effect on trace element abundances of carbonates. These fluids from the volcanic rocks and sediments must have brought Mn to the carbonates making it Mn-rich, which is a very common attribute for older carbonates, the higher Mn and Fe concentrations in Archean oceans is also considered as one of the reasons for them to be incorporated into the carbonate structures (Bekker et al., 2013) such is the case in our samples too. Another reason could be later stage dolomitization (Veizer et al., 1978), wherein Ca and possibly, Sr were replaced by Mg. This was followed by the passage of Mn-rich pore fluids which replaced Mg, thus resulting in increased Mn and low Sr abundances. We have used weak acetic acid (1M) with less reaction time for the leaching of carbonate phases. The Fe-Mn deposits are considered to have a Fe-Mn rich hydrothermal sources.
The results show extremely high Mn/Sr ratios. Do these represent carbonate-only fractions, or influence from the Mn deposits? I also wanted to ask about the interpretation for the source of the Fe-Mn deposits? Thank you!
Thanks for the question, Kim. I could not attend the Q&A because of the poor internet connectivity. Mn/Sr ratios are crucial for the determination of extent of diagenetic changes, but in case of Archean sediments Mn/Sr ratios are always pretty high and it works better in case of younger sediments. Many workers have described Archean oceans as mantle buffered as opposed to the continent buffered oceans of the present, which implies that the seawater was in close interaction with volcano-sedimentary deposits which would have a considerable effect on trace element abundances of carbonates. These fluids from the volcanic rocks and sediments must have brought Mn to the carbonates making it Mn-rich, which is a very common attribute for older carbonates, the higher Mn and Fe concentrations in Archean oceans is also considered as one of the reasons for them to be incorporated into the carbonate structures (Bekker et al., 2013) such is the case in our samples too. Another reason could be later stage dolomitization (Veizer et al., 1978), wherein Ca and possibly, Sr were replaced by Mg. This was followed by the passage of Mn-rich pore fluids which replaced Mg, thus resulting in increased Mn and low Sr abundances. We have used weak acetic acid (1M) with less reaction time for the leaching of carbonate phases. The Fe-Mn deposits are considered to have a Fe-Mn rich hydrothermal sources.
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