November GEOLOGY and GSA TODAY Media ...(d shed new light on the long-term ecolog...)

Sustained sulfide oxidation by physical erosion processes in the Mackenzie River basin: Climatic perspectives
Damien Calmels et al., Department of Earth Sciences, University of Cambridge, Cambridge CB2 3EQ, UK. Pages 1003-1006.

The chemical weathering of rocks is tightly coupled to the global carbon cycle because the dissolution of atmospheric carbon dioxide (CO2) in surface water is a main weathering agent of rock minerals. Dissolved weathering products as well as dissolved atmospheric carbon are transported by rivers to the ocean, where they combine to form carbonate deposits, trapping atmospheric CO2 for long periods of time. Although research into weathering has long focused on the role of CO2, there are other weathering agents that may disturb this carbon regulation loop. In addition to dissolved CO2, acidity of the Mackenzie River (one of the largest rivers in the world), Canada, is caused by sulfuric acid from the oxidation of sulfide minerals in the rocks underlying the catchment. Calmels et al. have shown that this mechanism contributes 60% of the river acidity, making sulfuric acid the most important weathering agent. Moreover, they have shown that its role increases with the intensity of physical erosion. In contrast to reactions involving CO2, the chemical weathering of rocks by sulfuric acid affects the global carbon cycle through the transitory release of CO2 from continental carbonate rocks to the atmosphere. In the Mackenzie River basin, weathering reactions are not a sink, but rather a source of CO2 to the atmosphere. If generalized, this conclusion may have interesting climatic perspectives.

New insights into the genesis of Indian kimberlites from the Dharwar Craton via in situ Sr isotope analysis of groundmass perovskite
Chad Paton et al., University of Melbourne,
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