汉南金水—青泥坑镁铁层状杂岩体与含铂性研究

汉南金水-青泥坑镁铁层状杂岩体位于扬子板块北缘汉南地体东北部,岩体侵位于中元古代西乡群。岩体出露面积大于500km~2。杂岩体主要由镁铁质辉长岩和部分超镁铁质辉石岩和橄榄岩组成。按层状岩序和岩石类型可以划分为上、下两个岩带,即由辉长岩类组成的上部带和由辉石岩-橄榄岩-粗粒蚀变辉长岩组成的下部岩带。研究表明,岩体的岩石化学、矿物化学和微量元素地球化学与层状岩序的演变相一致。韵律层发育部位,矿物组分多次重复出现,反映了形成杂岩体的岩浆有过多次侵位活动。还表明,层状岩序稀土总量和(La/Yb)_N值随层序增高而增加分馏趋势的一般规律。系统阐述了杂岩体各类岩石铂族元素分配特征。初步确定了铂矿化与铜镍矿化产出部位,讨论了铂族元素成矿作用问题。报告在分析了杂岩体产出的地质构造环境的基础上,探讨了杂岩体原始岩浆源的性质,同时估算了部分熔融程度。

MAFIC LAYERED COMPLEX BODY AND ITS PLATINUM-BEARING NATURE IN JINSHUI-QINGNIKENG HANLAN

Jinshui-Qingnikeng mafic layered complex body is located north rim of Yangtse plate, east-north position of Hanlan terrain. It intrudes into Xixiang Group, outcropping more than five hundred square kilometres and is mainly composed of gabbroites, partly ultramafic pyroxenite and peridotite. According to layered rock-sequence and types, the body is divided into two zones; the upper gabbroites and the lower zone composed of pyroxenite, peridotite and coarse altered gabbroite. It is studied that evolution of petrochemistry, mineral chemistry and trace element geochemistry is consistent with that of layered rock sequence. The position of developing rhythemtic units shows there had been many time emplacement activity of magma forming complex body. Besides, this paper has shown that the total value of REE and ratio of(La/Yb)_N increase with rise of layered rock sequence yet, those coincidence with general low of REE fractionation tendency. In this paper, a systematic explanation for PGE distribution charcteristics of various rocks in the complex body has been made, and the occurrence places of mineralization of Pt and Cu-Ni has preliminarily been determined and minerogenesis of PGE has also been discussed. After analysing geological tectonic environment in which the complex body forms, it is discussed character of parental magma, and estimated partly melting degree.