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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マグマから晶出する八面体席をもつ鉱物に最も効果的に取り込まれ,マグマの分化作用に最も敏感に反応する微量元素クロムは,マントルからの分化の程度を最もよく表し,それを使って大陸地殻の進化を辿ることができる.
上部マントルをつくるかんらん岩のCr存在度はコンドライトよりやや低い約3000ppmと見積られる.苦鉄質マグマから最初に晶出するCrを主要構成成分の一つとするスピネル,クロマイトは唯一の経済価値をもつCr鉱物である.Cr鉱床は層状とポディフォーム型に分けられる.世界のCr資源の90%以上を占める層状分化岩体のクロミタイト層は,苦鉄質マグマが珪酸分を混成した結果つくられた.珪酸分の増加はマグマのCr溶解度を減少させるからである.現在のCr生産量の半ば以上を供給するポディフォーム型鉱床もまた,苦鉄質マグマとかんらん岩の反応により生じた.ポディフォーム型鉱床・低Caボニナイト・ダイアモンドの包有物中のスピネルは地球上のスピネルのなかで最もCrが高い.特にボニナイトはコマチアイトより全岩Cr/Alが低いにもかかわらず,そのスピネルのCr/Alはコマチアイトのスピネルより高い,火山岩中のスピネルのCrは初生マグマのSiO₂の増加とともに増加する傾向がある.これはまた起源マントルにおける玄武岩成分の枯渇程度の反映でもある.
早期に晶出したCrに富むスピネルはマグマと反応して輝石をつくる.輝石もスピネル同様マグマからCrの大部分を取り去る.しかし,いくつかの高Mg安山岩においては,スピネルと共存する早期晶出輝石がむしろCrに乏しく,輝石中のCrがスピネルの減少とともに増加することもある.初生苦鉄質マグマのCr含有量は部分溶融によってマントルより1/3～1/10に減少する(1000～300ppm).しかし部分溶融の効果は結晶分化作用より小さい.結晶分化作用により最終分化物である珪長質岩のCr含有量は10ppm以下となる.
砕屑性堆積岩のCr含有量はおもに供給源地のCr量,即ち超苦鉄質～苦鉄質岩と珪長質岩の比によって決定され,堆積岩のCr含有量から供給源地のCr存在度を求めることができる.堆積岩から求めた地殻上部のCr存在度は50～100ppmとなり,カナダ楯状地の35ppmより高い.始生代の堆積岩は後の時代のものより一般にCrに富む.海洋地殻上に生じた若い島弧は苦鉄質岩が多く,珪長質岩の多い成熟した大陸地殻よりCr存在度が高い.地球表層部のCr存在度は大陸の成長・進化とともに減少してきた.

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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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