The Areal distribution of 35 elements(As, Au, Ba, Ca, Ce, Co, Cr, Cs, Cu, Eu, Hf, K, Fe, La, Lu, Mg, Mn, Na, Nd, Ni, P, Rb, Sb, Sc, Sm, Sr, Ta, Th, Th, Ti, U, V, Yb, Zn and Zr) was investigated by AAS, ICP-AES and INAA for 178 stream sediments over an approximately 300km
2 in the Tsugu area in the northeastern part of Aichi Prefecture where a gold mine had once operated.
The distribution patterns of some elements in the stream sediment reflect the surface geology of the drainage basin, especially the distributions of igneous rocks. The concentrations of Ca, Ce, Hf, Lu, Na, Nd, Sm, Sr, Ta, Th, Th, U and Yb are high in stream sediments of the granitic rocks basin, while those of Co, Cr, Fe, Mg, Ti and V are high in stream sediments of the mafic rocks basin. It seems that there are some groups of elements which correlate with each other. The factor analysis indicates the presence of the following six latent minerals controlling the distributions of elements: (1) monazite (2) mafic minerals (3) zircon (4) hydrothermal mineralization (5) plagioclase (6)K-feldspar, biotite, muscovite and/or clay minerals.
Chemical compositions of plagioclase, K-feldspar, amphibole, biotite, zircon, garnet, monazite and ferromagnetic minerals in the stream sediments and a country rock are also analyzed. The mineral compositions of stream sediments were deduced from the statistical analysis of their bulk compositions in terms of the mixing of the eight minerals analyzed here. They were compared with the distribution of minerals estimated by the factor analysis. Although the factor analysis could not distinguish between distribution patterns of amphibole and biotite and those of zircon and garnet, the method is capable of discriminating the minerals with similar chemical characteristics from each other.
The first and third factors that are regarded as monazite and zircon show high values in the sediments of granitic rocks. However, they are inversely correlated to each other in the sediments of the Inagawa granite area. The factor attributable to the hydrothermal mineralization is high value around Mt. Otoge where no mine has been reported, suggesting a new gold prospective area.
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