Minerals and Geochemical Characteristics of Ores from the Besshi-Type Deposits in the Sambagawa Belt, Japan
Minerals and Geochemical Characteristics of Ores from the Besshi-Type Deposits in the Sambagawa Belt, Japan
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日本三波川带别子型矿床矿石矿物及地球化学特征
DOI：
10.11456/shigenchishitsu1951.38.203
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发表时间：
1988
期刊：
影响因子：
--
通讯作者：
M. Yamamoto
中科院分区：
文献类型：
--
作者：
K. Kase;M. Yamamoto
黄铁矿、黄铜矿和闪锌矿是桑巴川带别西型矿床普通矿石的主要硫化物组成。磁黄铁矿和磁黄铁矿在某些矿床中大量存在。其他硫化物和磺基盐的量极少。在普通块状矿石中不常见的矿物，如方铅矿、四面体矿等，在富铜矿中，在主要层状矿体及其周围以分支、舌状和脉状形式出现的微量铜元素更为常见。这些矿物可能是在矿床的变质变形过程中，由常见的硫化物组成的硫化物结晶作用形成的。其显著的地球化学特征是高钴、低铅、低钡。虽然大部分硫化物的硫同位素数据仅来自Besshi存款，但Besshi型矿床的硫同位素比值分布非常窄，范围为+0.4至+3.9·K，平均值为+2.1·K。黄铁矿的Se/S值在6个矿床中也呈窄分布，平均值为1.32·~10-4。这些矿物和地球化学特征可能归因于相关的基性火山岩的化学。现代富铜海底硫化物矿床在化学性质上与别什式矿床十分相似。这两个矿床在矿物学上有些不同，但海底蚀变和丘内部的热液置换应改变海底硫化物矿床的原生矿物组合，使其向Besshi型矿床的方向发展。
Pyrite, chalcopyrite and sphalerite are the main constituent sulfides of the ordinary ores of the Besshitype deposits in the Sambagawa belt. Pyrrhotite and bornite occur in significant amounts in some deposits. The amounts of other sulfides and sulfosalts are extremely small. Minerals uncommon in ordinary massive ores, such as galena, tetrahedritess, etc., are found more frequently in trace amounts in copper-rich ores occurring as offshoots, tongues and veins in and around the main stratified orebodies. These minerals may have been formed during the metamorphic deformation of the deposits and the recrvstallization of constituent common sulfides. The notable geochemical characteristics of the Besshi-type ores are their high cobalt, low lead and low barium contents. Although most of the available sulfur isotope data of sulfides are only from the Besshi deposit, the spread of sulfur isotope ratios of the Besshi-type deposits is very narrow, ranging in ƒÂ34S from + 0.4 to +3.9•ñ with a mean of +2.1•ñ. The Se/S ratios of pyrite also display a narrow distribution around its mean of 1.32•~10-4 in six examined deposits. These mineral and geochemical characteristics of the Besshi-type ores can possibly be ascribed to the chemistry of related basic volcanics. Modern copper-rich sea-floor sulfide deposits are quite similar to the Besshitype deposits in their chemistry. These two deposits is somewhat different from each other in mineralogy, but seafloor alteration and hydrothermal replacement in the mound interiors should change the primary mineral assemblages of the sea-floor sulfide deposits toward those of the Besshi-type deposits.