川西稻城地区竹鸡顶铜矿床花岗细晶岩的特征及其成矿意义

竹鸡顶铜矿是中国西南＂三江＂多金属成矿带的典型铜矿床,矿体主要产于花岗细晶岩体内,目前已圈定3个规模较大的含铜矿花岗细晶岩体,铜矿最高品位达11.42%。花岗细晶岩体微量元素表现为Rb、Th、U等低场强元素含量相对富集,而Ba、Nb、Sr、P、Ti则明显亏损,为轻稀土元素富集型,呈现中等负Eu异常的特点。认为该区岩浆可能起源于中下地壳,形成于滞后型火山弧环境。围岩蚀变特征及次生氧化带的垂直分带特征均显示出类斑岩型铜矿床的特征,Cu-Mo综合异常明显较弱,而Pb-Zn综合异常相对较强,推断竹鸡顶铜矿为热液-斑岩型铜矿床,地表处于含矿斑岩体的顶部,主矿体可能还有一定的埋藏深度。矿床除铜富集外,可能还有锌、铋、钴、砷等的富集。

Characteristics of fine grain granitic rock and its metallogenic significance for Zhujiding copper deposit in western Sichuan, China

Zhujiding copper deposit is a typical copper deposit of the ＂Three Parallel Rivers＂ polymetallic metallogenic belt. The ore body is formed within the fine grain granitic rock. So far, three large-scale copper-bearing fine-grained granitic rocks have been delineated. The highest copper grade reaches around 11.42%. The results show that the fine grain granitic rock belongs to LREE enrichment and negative Eu anomalies with relative enrichment of Rb, Th and U and distinct negative anomalies of Ba, Nb, Sr, P and Ti. According to the similarity of the REE and trace element patterns, we deduce maybe the magma originated from the mid-lower crust and formed from the lagging-type volcanic arc environment. Wall-rock alteration and vertical zoning of secondary oxidation show the characteristics of porphyry-type copper deposit. Cu-Mo anomalies are significantly weaker and Pb-Zn anomalies are relatively stronger. So we infer that Zhujiding copper deposit belongs to hydrothermal-porphyry copper deposit. The surface is at the top of ore-bearing porphyry and the main ore body may be buried at some depth. in addition to Cu , there is maybe also Zn, Bi, Co and As concentrated.