A multiple isotope and trace element approach to constrain the oxygenation and metal cycling of 3.5 to 3.2 Ga paleo-oceans
Mineralogy, Petrology and Geochemistry
Final Report Abstract
The aim of the project was to obtain information on a possible localized role of free oxygen in weathering and sedimentary processes before the great oxidation event about 2.5 Ga ago. The study objects were sedimentary successions from drill cores of the Barberton Greenstone Belt. Two approaches were taken: One was the in-situ measurement of the iron isotope ratios by (Femto-)LA-ICP-MS) of the constituent minerals hematite, magnetite, siderite and ankerite from fine-grained sediment cycles of the Manzimnyama Iron Formation and the other the determination of Re-Os and U isotope ratios and of the PGE and other trace element abundances in bulk carbonaceous shales and leachates of the Mapepe Group. The quint essence is that the Paleoarchean sedimentary successions of the Barberton Greenstone Belt lack any indication of transient basin-scale oxygenation. The evidence comes mainly from the δ56Fe ratios of the siderites in the sediments of the Manzimnyama Iron Formation and from the Re-Os isotope systematics and PGE+Re patterns of the carbonaceous shales from the Mapepe Group. Quantitative oxidation of ferrous iron occurred in surface layers of Paleoarchean seawater occurred during the onset and termination of hydrothermal FeIIaq delivery into shallow waters.
Publications
- PGE-Re in Carbonaceous Siltstone from Barberton Drill Core: Sources and Paleo-Environment Goldschmidt Abstracts 2014, 2028
Rammensee P, Montinaro A, Strauss H & Aulbach S
- Re-Os study of Paleoarchean Carbonaceous Siltstones Goldschmidt Abstracts 2015, 2585
Rammensee P, Creaser RA, Montinaro A, Strauss H, & Aulbach S
- (2016) A multiple isotope and trace element approach to constrain the oxygenation and metal cycling of 3.5 to 3.2 Ga paleo-oceans Dissertation, Frankfurt, 252 Seiten
Rammensee Philipp
