抄録
Hydrothermal activity is considered to be responsible for ubiquitous silicification of Archean supracrustal rocks. Here, we show well-preserved evidence of hydrothermal silicification with in the Dixon Island Formation (3.2Ga) of Pilbara Craton, Australia. The formation is a part of immature oceanic island arc origin Cleaverville Group consists of three cycles of volcano?sedimentary sequence (Kiyokawa and Taira, in press). Each sequence consists of thick volcanics (basalt, rhyolite), black shale, ferruginous chert and BIF to the top. Especially, the Dixon Island Formation, which is the best exposed sequence, is composed of the Rhyolite Tuff, Black Chert and Varicolored Chert Members. The Rhyolite Tuff Member contains the multiple black chert veins which is feeders of the hydrothermal vent. These veins probably produced the chemogenic sediments of the upper members.
