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Dating the Paleoproterozoic snowball Earth glaciations using contemporaneous subglacial hydrothermal systems
The presence of Paleoproterozoic glacial diamictites deposited at low latitudes on different continents indicates that three or four worldwide glaciations occurred between 2.45 and 2.22 Ga. During that time period, the first atmospheric oxygen rise, known as the Great Oxidation Event (GOE), occurred...
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Published in: | Geology (Boulder) 2017-07, Vol.45 (7), p.667-670 |
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Main Authors: | , , , , , , |
Format: | Article |
Language: | English |
Subjects: | |
Citations: | Items that this one cites Items that cite this one |
Online Access: | Get full text |
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Summary: | The presence of Paleoproterozoic glacial diamictites deposited at low latitudes on different continents indicates that three or four worldwide glaciations occurred between 2.45 and 2.22 Ga. During that time period, the first atmospheric oxygen rise, known as the Great Oxidation Event (GOE), occurred, implying a potential connection between these events. Herein we combine triple oxygen isotope systematics and in situ and high-precision U-Pb zircon ages of mafic intrusions to date two episodes of snowball Earth glaciations. Subglacial hydrothermal alteration was induced by intrusions of high-Mg and high-Fe gabbros during the early Paleoproterozoic rifting on the Baltic Shield, which at the time was located at low latitudes. The low δ18O values of hydrothermally altered rocks associated with these intrusions are attributed to high-temperature isotopic exchange between hot rock and glacial meltwater, indicating the presence of glacial ice globally. The triple oxygen isotope approach is used here to show that the δ18O of glacial meltwaters during the dated episodes of snowball Earth glaciation was approximately -40 ppm VSMOW (Vienna standard mean ocean water). High-Mg gabbro intrusions and associated low-δ18O hydrothermally altered rocks formed during the earliest episode of snowball Earth glaciation between 2.43 and 2.41 Ga. High-Fe gabbro from the Khitoostrov locality (Karelia, Russia) hosts a δ18O value of -27.3 ppm and is dated here at 2291 ± 8 Ma. This age is interpreted to reflect the interaction between the intrusion and glacial meltwaters during the third Paleoproterozoic glaciation, which occurred after the GOE. |
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ISSN: | 0091-7613 1943-2682 |
DOI: | 10.1130/G38759.1 |