铂族元素矿物共生组合(英文)

由于铂族元素能有效地降低汽车尾气的污染 ,其需求量日益增加 ,对铂族元素矿床的寻找已是当务之急。着重从矿物矿床学角度对铂族元素的矿物共生特点进行了探讨。铂族元素可呈独立矿床产出 ,主要产于基性超基性层状侵入体、蛇绿岩套及阿拉斯加式侵入体中。铂族元素也伴生于铜镍矿床中 ,该类铜镍矿床主要与苏长岩侵入体、溢流玄武岩及科马提岩有关。产于基性超基性层状侵入体中的铂族矿物有铂钯硫化物、铂铁合金、钌硫化物、铑硫化物、铂钯碲化物、钯砷化物及钯的合金。这些铂族矿物可与硫化物矿物共生 ,也可与硅酸盐矿物共生 ,还可与铬铁矿及其他氧化物矿物共生。产于蛇绿岩套中的铂族矿物主要是钌铱锇的矿物 ,而铂钯铑的矿物则较少出现 ,这些铂族矿物可呈合金、硫化物、硫砷化物以及砷化物 4种形式出现。产于阿拉斯加式侵入体中的铂族矿物主要有铂铁合金、锑铂矿、硫铂矿、砷铂矿、硫锇矿及马兰矿等少数几种 ,其中铂铁合金与铬铁矿及与其同时结晶的高温硅酸盐矿物共生 ,而其他的铂族矿物则与后来的变质作用及蛇纹岩化作用中形成的多金属硫化物及砷化物共生。产于铜镍矿床中的铂族矿物主要是铂和钯的矿物。产于基性超基性层状侵入体、蛇绿岩套及阿拉斯加式侵入体中的铂族矿物的共同特点是它们均与铬铁矿?

PARAGENESIS OF PLATINUM-GROUP MINERALS

Platinum group minerals (PGM) occur either as PGM dominant deposits or as by products of Ni Cu deposits. The PGM dominant deposits are associated with mafic ultramafic layered complexes, ophiolite complexes, and Alaskan type complexes. The Ni Cu deposits containing PGM are associated with noritic rocks, intrusive equivalent of flood basalts, and komatiitic lavas and intrusions. The PGM associated with the mafic ultramafic layered complexes are dominated by Pt Pd sulfides, Pt Fe alloys, Ru sulfides (mainly laurite, occurring as inclusions in chromite), Rh sulfides, Pt Pd tellurides, Pt arsenides (mainly sperrylite) and Pd alloys. Three principal categories of mode of occurrence of PGM are evident: (1) association with base metal sulfides; (2) association with silicates; (3) association with chromite or other oxides. The PGM associated with ophiolite complexes consist predominantly of just three of the PGE: Ru, Ir and Os. Pt, Pd and Rh enter only in minor amounts or very rarely from discrete minerals. The PGM are mainly restricted to the four groups: (1) alloys (Os Ru Ir, Os Ir, Ir Os, Pt Pd Fe, Pd Sb Pt, Pt); (2) sulfides (RuS 2, OsS 2, Ir Cu sulfides); (3) sulfarsenides (OsAsS, IrAsS, PtAsS, RhAsS); (4) arsenides (PtAs 2). The PGM in the Alaskan type complexes occur primarily as Pt Fe( Ni Cu) alloys, geversite, cooperite, sperrylite, erlichmanite, and malanite Paragenetically, the PGM in the Alaskan type complexes can be subdivided into two groups. Group 1 consists predominantly of platinum bearing alloys associated with chromite and silicates segregated from high temperature silicate melts and coprecipitated with chromite, and Group 2 includes other PGM associated with base metal sulfides and arsenides formed during later metamorphism and serpentinization. The PGM from Ni Cu deposits are dominated by Pd and Pt minerals. PGM are found associated with chromitites in the layered mafic ultramafic complexes, ophiolites and Alaskan type complexes. Laurite is the dominant PGM inclusion in chromites; Pt , Pd , and Rh bearing minerals occur, in general, as interstitial phases. Many investigations agree that laurite inclusions in unfractured chromites are magmatic in origin as opposed to an earlier view that ascribed the formation of laurite to exsolution of PGE from the host chromite during cooling. Hydrothermal PGM deposits have been recognized in a variety of environments, even in the mafic ultramafic complexes. Current models for the genesis of these deposits involve transport of PGE and associated metals by chloride complexes during late stage magmatic hydrothermal processes.