『Abstract
　Alluvial and braided fluvial deposits of the 3.2 Ga Moodies Group in the Barberton greenstone belt, South Africa, are analyzed petrographically and geochemically to identify their source rocks (provenance) and assess the degree and type(s) of weathering required to produce the observed Moodies sediment compositions. conglomerate, sandstone, and shale data give somewhat differing pictures of provenance an weathering due to derivation from different components within the source terrane and size and compositional fractionation during transport. The results suggest that shale geochemistry provides the most accurate estimate provenance, although both rare-earth element and trace element (Th, Sc, Zr, Cr, and Ti) data must be used in combination to give the best results. The source area for Moodies Group sediments was dominated by tonalite, felsic volcanic rock, komatiite-basalt, and granite. Based on mineralogical and major-element divergence from estimated source area composition, the Moodies Group sediments are remnants of an aggressive weathering environment. Labile materials, such as komatiite, basalt, and coarse plagioclase grains, decomposed almost entirely to clays and solutes, and the chemical index of alteration for Moodies shale is well above the global average. An aggressive weathering environment in the Archean may have been achieved by increased rainfall, higher temperatures, and/or higher atmospheric PCO2. More likely, a combination of these conditions worked to offset the inhibitory weathering effects of a planet-free environment.

Keywords: Archean sedimentary rocks; Paleoweathering; Paleoclimate; Provenance; Barberton Greenstone Belt』

1. Introduction
2. Geologic setting
3. Weathering overview: From parent rock to siliciclastic sediment
4. Methodology
5. Composition and provenance of Moodies Group sedimentary rocks
　5.1. Conglomerate
　　5.1.1. Conglomerate composition
　　5.1.2. Conglomerate provenance
　5.2. Sandstone
　　5.2.1. Sandstone petrography
　　5.2.2. Sandstone geochemistry
　　5.2.3. Sandstone provenance
　5.3. Shale
　　5.3.1. Major- and trace-element shale geochemistry
　　5.3.2. REE shale geochemistry
　　5.3.3. Shale provenance
　　　5.3.3.1. REE
　　　5.3.3.2. REE least-squares mix
　　　5.3.3.3. REE principal component analysis (PCA)
　　　5.3.3.4. Trace elements
　　　5.3.3.5. REE and trace elements combined
6. Implications of the Moodies Group for weathering at 3.2 Ga
　6.1. Weathering implications of Moodies conglomerate and sandstone
　6.2. Quartz-plagioclase-potassiun feldspar (QPK) changes
　6.3. Geochemical changes
7. Factors contributing to aggressive Moodies weathering environment
　7.1. Rainfall
　7.2. Temperature and atmospheric CO2
8. Conclusions
Acknowledgements
Appendix A. Supplementary data
References