Geological Society of America

T254 Mineralogy, Geochemistry, Petrology, and Volcanology Student Session (Posters)

Wednesday, 25 September 2024
8:00 AM - 5:30 PM
Hall D

STRONTIUM ISOTOPES OF BARITE IN NEOPROTEROZOIC CAP CARBONATES RECORD MIXING BETWEEN SNOWBALL DEEPWATER AND GLACIAL MELTWATER

Paper number: T254-5
Program: Technical Sessions
Time: 8:00 AM – 5:30 PM

Authors

Ellery Renger Presenting Author
University of California Santa Barbara, Santa Barbara, CA
Ellery Renger Presenting Author
University of California, Berkeley, Berkeley, CA
Francis Macdonald
University of California Santa Barbara, Santa Barbara, CA
Francis Macdonald
University of California, Berkeley, Berkeley, CA
Adrian Tasistro-Hart
University of California Santa Barbara, Santa Barbara, CA
Benjamin Byerly
University of California Santa Barbara, Santa Barbara, CA
Matthew G. Jackson
University of California Santa Barbara, Santa Barbara, CA

Abstract

The Snowball Earth hypothesis predicts that the hydrological cycle was effectively shut down for millions of years, inhibiting silicate weathering of the continental crust. In this scenario the deep ocean should have equilibrated with the geochemistry of the mantle through hydrothermal exchange at mid-ocean ridges. During deglaciation, barium from Snowball deepwater mixed with sulfate-rich meltwater to form barite (barium sulfate) fans within cap carbonates. Barite’s mineral structure results in significantly higher Sr concentrations compared to carbonates, which goes along with barite’s resistance to dissolution and diagenesis.

Here we report TIMS Sr isotope data from barite in Marinoan cap carbonates from Mongolia, Mauritania, NW Canada and a Sturtian cap carbonate in Oman. The ⁸⁷Sr/⁸⁶Sr ratio of the cap carbonates is used as a geochemical tracer of mixing between the radiogenic glacial meltwater and the unradiogenic Snowball deepwater. Marinoan cap carbonate deposits exhibit a spread of more radiogenic values due to the shorter Snowball duration and position of barite at the top of the cap. Basal Sturtian deposits exhibit mantle-like values, which is consistent with the longer duration of the Sturtian glaciation.

Geological Society of America Abstracts with Programs. Vol. 56, No. 5

doi: 10.1130/abs/2024AM-403737

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