山东桃科铜镍矿床矿物学特征及其对矿床成因的指示

Mineralogical characteristics of Taoke Cu-Ni sulfide deposit in Shandong Province and its indications for metallogenic genesis

桃科铜镍矿床是山东目前发现的仅有的2处铜镍矿床之一,也是中国最早开采的铜镍矿床之一,同时也可能是中国形成时代最老的铜镍矿床。含矿岩体主要由橄榄辉长苏长岩、蚀变辉长苏长岩、变辉长岩、角闪岩组成,主要矿物为贵橄榄石、古铜辉石、普通辉石、角闪石和中基性斜长石（培长石、中长石、拉长石）,岩石常发生强烈的绿泥石化、钠黝帘石化、纤闪石化;矿石中黄铜矿＋镍黄铁矿＋磁黄铁矿的矿物组合,为典型的岩浆型铜镍硫化物矿床的矿物组合;岩石及矿物特征表明矿床为岩浆作用的产物。通过矿物显微结构特征以及计算得出：桃科岩体橄榄石开始结晶温度大约在1421℃左右,古铜辉石和普通辉石的结晶温度在1030～1230℃之间,两矿物相在岩石中可以共存。矿石中大量镍黄铁矿蚀变为针镍矿,黄铜矿在边部蚀变为斑铜矿,以及黄铁矿较高的Co/Ni比值（0.1～12.9,平均4.1）,都表明矿床在后期遭受了强烈的热液叠加改造作用。

The Taoke Cu-Ni sulfide deposit, one of the two recently discovered Cu-Ni deposits in Shandong Province, is also one of the earliest exploited deposits in China and probably the oldest Cu-Ni deposit in China. The oreforming intrusion is mainly composed of olivine gabbronorite, altered gabbronorite, altered gabbro and amphibolite, and the mainly minerals consist of chrysolite, bronzite, pyroxene, hornblende and plagioclase （including bytownite, andesine and labrador）, with chloritization, saussuritization and uralitization occurring in the rocks. Chalcopyrite ＋ pentlandite ＋ pyrrhotine is the typical ore mineral assemblage of the magmatic Cu-Ni sulfide deposit. The mineral microstructure features and calculated crystallization temperature of the silicate minerals （about 1421℃ for olivine and between 1030℃ to 1230℃ for pyroxenes） suggest that the two mineral phases could coexist in the magma. A large quantity of pentlandite was altered to millerite, the bornite is distributed at the edge of the chalcopyrite, and the Co/Ni ratios of the pyrite are relatively high （from 0.1 to 12.9, averagely 4.1 ）. These characteristics show that there existed strong hydrothermal alteration in the later magma process of the Taoke Cu-Ni sulfide deposit.