金川铜镍型铂族元素矿床地质地球化学特征

GEOLOGICAL AND GEOCHEMICAL CHARACTERISTICS OF THE JINCHUAN PLATINUM GROUP ELEMENT DEPOSIT OF THE COPPER NICKEL TYPE, GANSU

金川铜镍型铂族元素矿床产于超基性岩体内。全矿区产有６０多个Ｐｔ（Ｐｄ＞１．０×１０－６的铂（钯）富集体，还有Ｏｓ、Ｉｒ、Ｒｕ、Ｒｈ含量相对高的富集地段及Ｏｓ（Ｒｕ）＞０．４０×１０－６的高含量贯入型特富矿体。总体上，Ｐｔ、Ｐｄ与Ｃｕ密切相关，Ｏｓ、Ｉｒ、Ｒｕ、Ｒｈ与Ｎｉ相关性强，表明ＰＧＥ富集作用与Ｃｕ、Ｎｉ成矿作用具有不可分割的联系。ＰＧＥ球粒陨石标准化型式属Ｐｔ－Ｐｄ配分型，显示富Ｐｔ、Ｐｄ而贫Ｏｓ、Ｉｒ、Ｒｕ、Ｒｈ的地球化学特征。根据赋矿岩石性质、ＰＧＥ品位和成矿作用的差别，将本区ＰＧＥ矿石成因类型划分为四大类型和七个亚类，其中Ｃｕ－Ｎｉ－ＰＧＥ矿石是主要ＰＧＥ矿石类型。通过本区ＰＧＥ演化和富集特征的研究，表明占主导地位是岩浆熔离作用形成的ＰＧＥ，而热液作用的ＰＧＥ占极次要地拉。提出在岩矿浆演化过程中形成高浓度与中低浓度熔融区的岩矿浆分层原理，在重力作用和扩散作用双重效应下产生含ＰＧＥ岩浆分层体系和成矿富集机理的观点。成矿物质来源于上地幔。矿床具有多期成矿和岩浆熔离作用特征。

The Jinchuan Platinun group element (PGE) deposit of the copper nickel type occurres in ultrabasic intrusions. In the whole mining area, there are more than 60 Pt(Pd) enrichment bodies rich in Pt(Pd)>1.0×10 -6 , enrichment regions with relatively high contents of Os, Ir, Ru, Rh, and penetraction type ore bodies with very high contents of Os(Ru) more than 0.4×10 -6 .As a whole, Pt and Pd are closely related to Cu, and Os,Ir,Ru,Rh are closely correlated with Ni, which indicate that PGE enrichment has indivisible correlation with Cu Ni mineralization. The chondrite nomalized patterns of the PGE belong to the Pt Pd partition type, and show geochemical characters rich in Pt, Pd and poor in Os,Ir,Ru,Rh. Based upon the host rock natures, PGE grade and differences in mineralization, PGE ores in this area can be genetically classified into four types and seven sub types, in which the Cu Ni PGE ore is a main type of PGE ores. It is indicated from studies of PGE evolution and enrichment charaters, that the PGE formed by magma liquation are predominant, while the PGE formed by hydrothermalism are extremely secondary. A principle and a mechanism are proposed, which are stratigraphic principle about magma and ore pulp of forming high content and middle low content areas during the evolution of magma, and stratigraphic system of PGE bearing magma and mineralization enrichment machanism produced by double effects of gravity differentiation and diffusion mineralization materials are from upper mantle. The Cu Ni PGE deposit is charactered by magma liquation and multistage mineralization.