基性-超基性岩铜镍矿与铬铁矿含矿性判别研究

岩石与矿物地球化学数据常用于判别岩石成因、构造环境等,事实上它们也可以用于判别岩石成矿专属性,从而更好地指导找矿工作。通过对含铜镍矿的基性-超基性岩与含铬铁矿的基性-超基性岩全岩主量、铂族元素和铬铁矿尖晶石地球化学特征进行综合对比研究结果显示:1)铜镍矿的m/f值主要集中在1.5～8.5,铬铁矿主要集中在6.5～12.5,有一定重叠,因此通过m/f值确定是否成矿具有不确定因素;利用全岩主量元素的二元图解进行判别也存在重叠区域,不利于成矿专属性的判别。2)铜镍矿基性-超基性岩全岩具有高的w(PPGE)/w(IPGE)值(0.06～343.75,平均16),w(Pd)/w(Ir)1;铂族元素具有左倾的原始地幔配分模式;铬铁矿尖晶石高w(TiO_2)、Fe~#值,Cr~#、Mg~#值变化范围较大。3)铬铁矿基性-超基性岩全岩具有低的w(PPGE)/w(IPGE)值(0.000 4～20.34,平均0.55),w(Pd)/w(Ir)1,铂族元素具有右倾的原始地幔配分模式;铬铁矿尖晶石低w(TiO2),Fe~#、Mg~#值,高Cr~#值。因此,利用基性-超基性岩的铂族元素与铬铁矿地球化学特征值能有效指示成矿专属性,可成为基性-超基性岩铬铁矿与铜镍矿的勘查工具。

Discriminatoin of specific attributive of Cu-Ni ore or Cr ore to basic-ultrabasic rocks

The geochemical data of whole rock and minerals are often used to discriminate genesis and geotectonic setting of rocks. In fact, they can also be used to discriminate specific attributive of ores to the rocks so as to guide the prospecting work. The geochemical characteristics of major elements and PGE of the whole rock and those of chromium spinel from the copper-nickel ore or Cr ore hosted basic-ultrabasic rocks are comparatively studied. The results show that:1) the ratio of m/f of the copper-nickel ore hosted basic-ultrabasic rocks is mainly concentrated in range of 1.5 to 8.5, and chromite ore-hosted basic-ultrabasic rocks in range of 6.5 to 12.5. A certain overlap occur so there is some uncertainty to determine which ore will occur by using the ratio. The binary diagram of the major elements of whole rock also show some overlap and can not effectively discriminate the specific attributive. 2) The Cu-Ni ore-hosted basic-ultramafic rocks exhibit high w(PPGE)/w(IPGE) values (0.06 to 343.75, average 16), w(Pd)/w(Ir)>1, left inclined primitive mantle normalized pattern of PGE of the whole rock, and their chromium spinels high w(TiO₂), Fe^# values, and wide range of Fe^#, Cr^# and Mg^# value; 3) the chromium ore-hosted basic-ultrabasic rocks show low w(PPGE)/w(IPGE) values (0.000 4 to 20.34, average 0.55), w(Pd)/w(Ir)<1, right inclined primitive mantle normalized pattern of PGE, and their Cr spinel low w(TiO₂), Fe^#, Mg^# values and high Cr^# Values. Therefore, the geochemical characteristics of PGE and chromite of the basic-ultramafic rocks can effectively indicate their ore-forming specific attributive and become a tool for exploration of chromite and copper-nickel deposits in basic-ultrabasic rocks.