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黔西南出露大范围的碱性超基性脉岩,其成因研究对了解该地区大规模的金矿形成具有重要意义。采用卡洛斯管同位素稀释法结合ICP-MS分析了黔西南4个岩区碱性超基性脉岩中的Ni、Ir、Ru、Rh、Pt、Pd和Cu的含量。结果显示:研究区脉岩铂族元素(PGE)的含量普遍较低,原始地幔标准化PGE分布模式呈正斜率型;并具有较高的Cu/Pd比值(11903~60210)。综合对比研究表明,研究区脉岩为地幔低程度部分熔融作用的产物,原始岩浆具有硫不饱和的特征,岩浆在上升过程中没有发生明显的硫化物分异,但发生了一定程度的岩浆分离结晶。此外,陇要脉岩可能经历了岩浆上升时铬铁矿的分离结晶作用。
A large range of alkaline ultrabasic veins are exposed in southwest Guizhou. The study on its genesis is of great significance for understanding the formation of large-scale gold deposits in the area. The contents of Ni, Ir, Ru, Rh, Pt, Pd and Cu in alkaline ultrabasic dikes in four areas of southwestern Guizhou were analyzed by means of Carlos tube isotope dilution coupled with ICP-MS. The results show that the content of PGE in the veins of the study area is generally low, and the normalized PGE distribution pattern in the original mantle shows a positive slope type with a high Cu / Pd ratio (11903-60210). The comprehensive comparative study shows that the mafic rocks in the study area are the products of low-degree partial melting of the mantle, the original magma has the characteristic of sulfur unsaturation, and no obvious sulphide differentiation occurs in the magma ascending, but a certain degree of magmatic separation has occurred crystallization. In addition, the Longyao veins may have experienced the crystallization of chromite at the time of magma ascent.