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Dusk in the North Pole area, Pilbara craton, Western Australia.
I have joined field mappings of Pilbara craton by the Titech group since 1996. My field research has focused on the North Pole area at the central part of Pilbara Granite-Greenstone Terrane. The area is well-known as a locality of the oldest (~3.5 Ga) microfossils (Awramik et al., 1983). Our intensive field mapping has demonstrated the fossil-bearing chert/barite beds are closely associated with synsedimentary hydrothermal veins (silica dikes), which penetrated into >1000m-thick pillowed basaltic greenstones below the chert/barite bed (e.g., Isozaki et al., 1997; Kitajima et al., 2001). This greenstone/chert sequence occurs as a tectonic slice bounded by layer-parallel thrust. The stacking pattern of the tectonic slices shows duplex structure produced by horizontal shortening. This suggests that the greenstone/chert sequences represent fragments of the Archean oceanic crust accreted into the arc or continent at subduction zone (e.g., Maruyama et al., 1991).
Horizontal-shortening structure observed in the North Pole area (Ueno 2002 Doctor Thesis). Thrust-bounded tectonic slices composed of pillowed basalt and overlying chert bed are repeated nine times and form imbricated thrust piles (duplex structure).
The ~2.7 Ga Tumbiana Formation of the Fortescue Group is a succession developed in response to Late Archean crustal extension in the Pilbara Craton, northwestern Australia.
Ancient crustal rocks provide the only direct evidence for surface tectonics, and the processes and products of differentiation in early Earth. However, the oldest recognized terrestrial rocks (≧3600 Ma) are rare, and only nine terrains are preserved. The Acasta Gneiss Complex contains the 4.03 Ga orthogneisses (Bowring & Williams, 1999), which are the
oldest rocks in the world so far.
The formation is characterized by the wide occurrence of oxygenic stromatolites (Buick 1992), and provides a perspective of the evolution of photosynthetic organisms, which are interpreted to have been responsible for the oxygenation of ocean and atmosphere in early Earth. 
In collaboration with Prof. Makoto Ito at Chiba University, we have performed detailed field mapping and sequence-stratigraphic analyses of the Tumbiana Formation in the Redmont area, a central part of the Pilbara Craton (Sakurai et al., 2005).
Also, the sedimentary rocks of the Fortescue Group host anomalously 13C-depleted kerogen (up to -60‰. It has been hypothesized that the onset of oxygen release resulted in the appearance of O2-dependent methanotrophy, which would have produced the extremely 13C-depleted organic matter (Hayes 1994). For the better understanding of the biological activity and at that time and evaluating the effect of photosynthesis on surrounding environment, we have investigated geological, stratigraphical, and petrographical distributions of the 13C-depleted kerogen (Sakurai, 2003).
A model of spatial and temporal variations in depositional systems of the Tumbiana Formation in the Redmont area (Sakurai et al., 2005).
3. The ~4.0 Ga Acasta Gneiss Complex, Slave craton, Canada
We have reinvestigated geology and geochronology of the Acasta Gneiss Complex in Slave Province, Northwest Territories of Canada. Based on detailed 1:5000 scale geological mapping and petrographic investigation of about 1000 specimen, we have documented six distinct lithofacies, and at least eight tectonothermal events (Komiya et al., 2003). My research has focused on searching for information of the earliest surface environment through the study of multiple sulfur isotopes.
Acasta River.
About 4.0-billion-years-old orthogneisses and older enclaves of mafic rock.
Midnight rainbow from camp site.