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 300km² 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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One of the trace elements, chromium, which is incorporated most effectively into the crystallizing minerals with octahedral sites from a magma and therefore most sensitive to magmatic fractionation, best indicates the degree of fractionation from the Earth's mantle, and can be used to trace the evolution of the continental crust.
The early crystallized Cr-rich spinels react with the magma to form pyroxenes. Pyroxenes like spinels remove most of the Cr from the magma. In some high-Mg andesites, however, the early formed pyroxenes that coexist with spinels are rather low in Cr, and the Cr contents in the pyroxenes increase with decreasing Mg/Fe in the pyroxenes at the expense of spinels. In primary mafic magmas Cr is reduced relative to mantle rocks by a factor of three to ten through partial melting (1000-300 ppm). However, effects on Cr content of the melting degree are small relative to those of crystal fractionation. Crystal fractionation reduces Cr in the latest felsic differentiates to less than 10 ppm.
Chromium abundances of peridotite constituting the upper mantle are around 3000 ppm, which are slightly lower than those of chondrite. Spinel with Cr as a major constituent, chromite, crystallizes first from most basaltic magmas, and chromite is the only Cr-mineral of economic interest. Chromite orebodies can be divided into layered and podiform types. Chromitite layers in large ultramafic-mafic intrusions, which occupy more than 90 % of world chromite resources, originate from contamination of the mafic magma with silicic liquid, because the increase of SiO₂ decreases the Cr solubility in basaltic melt. Podiform chromitites, which provide more than half of chromite produced, also form by interaction between basaltic melt and depleted peridotite. Spinels with the highest Cr in terrestrial rocks are found in podiform chromitites, low-Ca boninites and inclusions in diamond. The chromites from low-Ca boninites are higher in Cr/Al than chromites from komatiites with high Cr/Al relative to boninites. The Cr contents of spinels in volcanic rocks tend to increase with increasing SiO₂ in primary magmas. They also increase with increasing degrees of depletion of basaltic components in the source peridotites.
Chromium contents in clastic sediments are controlled dominantly by the Cr abundances in the source areas, and can be used to estimate the ratio of ultramafic and mafic to felsic rocks in provenance. The Cr abundances of the weathered crust estimated from clastic sediments are 50 to 100 ppm, which are higher than the Cr abundance, 35 ppm, of the exposed Canadian Precambrian shield. Many Archean sediments show elevated Cr concentrations relative to post-Archean sediments, and immature, mafic oceanic terranes have higher Cr abundances than mature, felsic continental crust. The Cr abundances of the Earth's surface have decreased with the evolution of the continental crust.

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The world-wide Dachang ore field, 30km long (NS) by 20km wide (EW) and characterized by tin-bearing polymetallic mineralization related to the Yenshanian granitic magmatism, Guangxi, China, is one of four ore fields in the Danchi fold belt, adjoining to the western margin of the Precambrian Jiangnan old-land and forming part of the eastern margin of the Late Paleozoic Youjian fold belt.
A large quantity of metals of various kinds, including Sn, Sb, Zn, Pb, Cu, Ag, Cd and In, has so far been recovered from the Dachang ore field. For instance, more than 10⁶ tons of tin (as metal), equivalent to several times as much as the current world metal production, were fixed in this ore field.
Currently working mines throughout the Dachang ore field are: Changpo-Tongken and Longtaoshan (western part); Lamo and Chashan (central part); Dafulao and Kengma (eastern part). The former two are the major mines in the ore field. The Changpo-Tongken deposits are the largest known tin deposits with ore reserves of about 80×10⁶ tons averaging about 1% Sn and 3.5% Zn and occur as stratiform, veins and networks hosted by upper Devonian limestone and siliceous rocks. The Longtaoshan deposits occur as veins and are hosted by middle Devonian reef limestone, with ore reserves of about 10⁷ tons averaging about 1.5%Sn, 10%Zn, 6%Pb, 5%Sb and 150ppm Ag. The Lamo Cu-Zn skarns, averaging about 2%Cu, 5%Zn and 0.1%Sn, occur at the boundary between the Longxianggai granite and upper Devonian limestone and black shale. Small-scaled and low-grade stratiform deposits and veins at the Dafulao and Kengma mines occur in lower Devonian argillaceous limestone and shale.
From regional viewpoints, it is suggested that the southern part of China, especially areas underlain by the Yenshanian granitoids, still has high exploration potentialities for tin and other rare-metals.

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