Systematic collection and basic discription of the rock samples

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The sampling Group has mapped the following areas to collect samples systematically over the world. Those are the orogenic belts from (1) 3.9-3.6Ga Isua, SW Greenland, (2) 3.5-3.3 Ga Pilbara, 2.7-1.9Ga Hamersley and adjacent regions, W. Australia, and 3.5 Ga Barberton region of S. Africa and 2.7 Ga Zimbabwe, (3) 1.0-0.6 Ga Russian Altai-Sayan region, and (4) Permo-Triassic cherts in Inuyama, Japan.These field researches are planned to decode the first-class geologic events of the evolving Earth, namely, at boundaries of (1) Hadean/Archean, (2) Archean/Proterozoic, (3) Proterozoic/Phanerozoic, and (4) Permian/Triassic. All samples collected were preliminary described in terms of petrography, rock-forming mineralogy and major-trace element geochemistry.The followings are the brief summary of our results. (1) Origin of life goes back to 3.9Ga and born at hydrothermal system of mid-oceanic ridge. (2) Depth of seawater was 1600m above ridge crest at 3.5 Ga. XCO2 was ca. 100 times higher than that of modern mid-oceanic ridge. (3) Plate tectonics goes back to 3.9Ga, when modern-stype consuming plate boundary process has already operated by the presence of rigid plate. (4) Potential mantle temperature was 150 C higher than that of modern mid-oceanic ridge. The source mantle was richer in FeO (10wt%) than that of modern MORB (8wt%). (5) Superanoxic event was identified in both deep-sea and off-shore of oceanic islands at Permo-Triassic boundary. Moreover, it was proposed that the Proterozoic-Phanerozoic boundary has been a fate of initiation of return flow of seawater into mantle at 750Ma, based on the extensive compilation of regional metamorphic belts over the world, and a new phase diagram of (MORB+Water) established by new multi-anvil experiments. The mass extinction at Permo-Triassic boundary was speculated to be caused by kimberlitic explosive magmatism and related temporary stop of photo-synthesis. This may be associated with superplume activity.