Hydrothermal system on the 2.77 Ga Mt Roe basalt, Pilbara Craton, Western Australia

Abstract

The 2.77 Ga Mt. Roe basalt near Whim Creek, Pilbara, Western Australia, exhibits extensive developments of sericite and pyrophullite alteration zones. We have suggested that the alteration zones are products of submarine hydrothermal activity at shallow water depths. The ABDP drilling was carried out near the outcrop to recover fresh samples of the alteration zones of the Mt. Roe basalt. The geological and geochemical evidences observed in the drilling core the hydrothermal alteration might occur essentially concurrent with the eruption of the Mt. Roe basalt, and suggest that a large-scale submarine hydrothermal activity with different colony took place at various water depths. In the wide area methanogens were highly active in the various hydrothermal veins, and that the methanotrophs near the sea floor had exhausted methane gas using the free oxygen produced by stromatolite in the shallow depth or using the oxygen from sulfate ions decomposed by sulfate reducing bacteria in the depth.