Sedimentary talc in Neoproterozoic carbonate successions
Mineralogical, petrographic and sedimentological observations document early diagenetic talc in carbonate-dominated successions deposited on two early Neoproterozoic (~800-700million years old) platform margins. In the Akademikerbreen Group, Svalbard, talc occurs as nodules that pre-date microspar c...
Published in: | Earth and Planetary Science Letters |
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ftucambridgeesc:oai:eprints.esc.cam.ac.uk:2348 2023-05-15T17:52:26+02:00 Sedimentary talc in Neoproterozoic carbonate successions Tosca, Nicholas J. Macdonald, Francis A. Strauss, Justin V. Johnston, David T. Knoll, Andrew H. 2011-06 application/pdf http://eprints.esc.cam.ac.uk/2348/ http://eprints.esc.cam.ac.uk/2348/1/toscaespl.pdf http://linkinghub.elsevier.com/retrieve/pii/S0012821X1100207X https://doi.org/10.1016/j.epsl.2011.03.041 en eng http://eprints.esc.cam.ac.uk/2348/1/toscaespl.pdf Tosca, Nicholas J. and Macdonald, Francis A. and Strauss, Justin V. and Johnston, David T. and Knoll, Andrew H. (2011) Sedimentary talc in Neoproterozoic carbonate successions. Earth and Planetary Science Letters, 306 (1-2). pp. 11-22. ISSN 0012-821X DOI https://doi.org/10.1016/j.epsl.2011.03.041 <https://doi.org/10.1016/j.epsl.2011.03.041> 01 - Climate Change and Earth-Ocean Atmosphere Systems Article PeerReviewed 2011 ftucambridgeesc https://doi.org/10.1016/j.epsl.2011.03.041 2020-08-27T18:09:13Z Mineralogical, petrographic and sedimentological observations document early diagenetic talc in carbonate-dominated successions deposited on two early Neoproterozoic (~800-700million years old) platform margins. In the Akademikerbreen Group, Svalbard, talc occurs as nodules that pre-date microspar cements that fill molar tooth structures and primary porosity in stromatolitic carbonates. In the upper Fifteenmile Group of the Ogilvie Mountains, NW Canada, the talc is present as nodules, coated grains, rip-up clasts and massive beds that are several meters thick. To gain insight into the chemistry required to form early diagenetic talc, we conducted precipitation experiments at 25°C with low-SO4 synthetic seawater solutions at varying pH, Mg2+ and SiO2(aq). Our experiments reveal a sharp and reproducible pH boundary (at ~8.7) only above which does poorly crystalline Mg-silicate precipitate; increasing Mg2+ and/or SiO2(aq) alone is insufficient to produce the material. The strong pH control can be explained by Mg-silica complexing activated by the deprotonation of silicic acid above ~8.6-8.7. FT-IR, TEM and XRD of the synthetic precipitates reveal a talc-like 2:1 trioctahedral structure with short-range stacking order. Hydrothermal experiments simulating burial diagenesis show that dehydration of the precipitate drives a transition to kerolite (hydrated talc) and eventually to talc. This formation pathway imparts extensive layer stacking disorder to the synthetic talc end-product that is identical to Neoproterozoic occurrences. Early diagenetic talc in Neoproterozoic carbonate platform successions appears to reflect a unique combination of low Al concentrations (and, by inference, low siliciclastic input), near modern marine salinity and Mg2+, elevated SiO2(aq), and pH>~8.7. Because the talc occurs in close association with microbially influenced sediments, we suggest that soluble species requirements were most easily met through microbial influences on pore water chemistry, specifically pH and alkalinity increases driven by anaerobic Fe respiration. Article in Journal/Newspaper Ogilvie Mountains Svalbard University of Cambridge, Department of Earth Sciences: ESC Publications Svalbard Canada Ogilvie ENVELOPE(-139.746,-139.746,63.563,63.563) Ogilvie Mountains ENVELOPE(-138.254,-138.254,64.583,64.583) Akademikerbreen ENVELOPE(18.391,18.391,78.718,78.718) Rip ENVELOPE(-19.509,-19.509,65.690,65.690) Earth and Planetary Science Letters 306 1-2 11 22 |
institution |
Open Polar |
collection |
University of Cambridge, Department of Earth Sciences: ESC Publications |
op_collection_id |
ftucambridgeesc |
language |
English |
topic |
01 - Climate Change and Earth-Ocean Atmosphere Systems |
spellingShingle |
01 - Climate Change and Earth-Ocean Atmosphere Systems Tosca, Nicholas J. Macdonald, Francis A. Strauss, Justin V. Johnston, David T. Knoll, Andrew H. Sedimentary talc in Neoproterozoic carbonate successions |
topic_facet |
01 - Climate Change and Earth-Ocean Atmosphere Systems |
description |
Mineralogical, petrographic and sedimentological observations document early diagenetic talc in carbonate-dominated successions deposited on two early Neoproterozoic (~800-700million years old) platform margins. In the Akademikerbreen Group, Svalbard, talc occurs as nodules that pre-date microspar cements that fill molar tooth structures and primary porosity in stromatolitic carbonates. In the upper Fifteenmile Group of the Ogilvie Mountains, NW Canada, the talc is present as nodules, coated grains, rip-up clasts and massive beds that are several meters thick. To gain insight into the chemistry required to form early diagenetic talc, we conducted precipitation experiments at 25°C with low-SO4 synthetic seawater solutions at varying pH, Mg2+ and SiO2(aq). Our experiments reveal a sharp and reproducible pH boundary (at ~8.7) only above which does poorly crystalline Mg-silicate precipitate; increasing Mg2+ and/or SiO2(aq) alone is insufficient to produce the material. The strong pH control can be explained by Mg-silica complexing activated by the deprotonation of silicic acid above ~8.6-8.7. FT-IR, TEM and XRD of the synthetic precipitates reveal a talc-like 2:1 trioctahedral structure with short-range stacking order. Hydrothermal experiments simulating burial diagenesis show that dehydration of the precipitate drives a transition to kerolite (hydrated talc) and eventually to talc. This formation pathway imparts extensive layer stacking disorder to the synthetic talc end-product that is identical to Neoproterozoic occurrences. Early diagenetic talc in Neoproterozoic carbonate platform successions appears to reflect a unique combination of low Al concentrations (and, by inference, low siliciclastic input), near modern marine salinity and Mg2+, elevated SiO2(aq), and pH>~8.7. Because the talc occurs in close association with microbially influenced sediments, we suggest that soluble species requirements were most easily met through microbial influences on pore water chemistry, specifically pH and alkalinity increases driven by anaerobic Fe respiration. |
format |
Article in Journal/Newspaper |
author |
Tosca, Nicholas J. Macdonald, Francis A. Strauss, Justin V. Johnston, David T. Knoll, Andrew H. |
author_facet |
Tosca, Nicholas J. Macdonald, Francis A. Strauss, Justin V. Johnston, David T. Knoll, Andrew H. |
author_sort |
Tosca, Nicholas J. |
title |
Sedimentary talc in Neoproterozoic carbonate successions |
title_short |
Sedimentary talc in Neoproterozoic carbonate successions |
title_full |
Sedimentary talc in Neoproterozoic carbonate successions |
title_fullStr |
Sedimentary talc in Neoproterozoic carbonate successions |
title_full_unstemmed |
Sedimentary talc in Neoproterozoic carbonate successions |
title_sort |
sedimentary talc in neoproterozoic carbonate successions |
publishDate |
2011 |
url |
http://eprints.esc.cam.ac.uk/2348/ http://eprints.esc.cam.ac.uk/2348/1/toscaespl.pdf http://linkinghub.elsevier.com/retrieve/pii/S0012821X1100207X https://doi.org/10.1016/j.epsl.2011.03.041 |
long_lat |
ENVELOPE(-139.746,-139.746,63.563,63.563) ENVELOPE(-138.254,-138.254,64.583,64.583) ENVELOPE(18.391,18.391,78.718,78.718) ENVELOPE(-19.509,-19.509,65.690,65.690) |
geographic |
Svalbard Canada Ogilvie Ogilvie Mountains Akademikerbreen Rip |
geographic_facet |
Svalbard Canada Ogilvie Ogilvie Mountains Akademikerbreen Rip |
genre |
Ogilvie Mountains Svalbard |
genre_facet |
Ogilvie Mountains Svalbard |
op_relation |
http://eprints.esc.cam.ac.uk/2348/1/toscaespl.pdf Tosca, Nicholas J. and Macdonald, Francis A. and Strauss, Justin V. and Johnston, David T. and Knoll, Andrew H. (2011) Sedimentary talc in Neoproterozoic carbonate successions. Earth and Planetary Science Letters, 306 (1-2). pp. 11-22. ISSN 0012-821X DOI https://doi.org/10.1016/j.epsl.2011.03.041 <https://doi.org/10.1016/j.epsl.2011.03.041> |
op_doi |
https://doi.org/10.1016/j.epsl.2011.03.041 |
container_title |
Earth and Planetary Science Letters |
container_volume |
306 |
container_issue |
1-2 |
container_start_page |
11 |
op_container_end_page |
22 |
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1766159868124725248 |