贵州西部红岩地区水系沉积物中Pt、Pd地球化学异常的识别及推断解释

Recognization and Interpretation of Pt and Pd Geochemical Anomaly in Stream Sediment in Hongyan Area,Western Guizhou Province,China

与基性-超基性岩相比,我国的峨眉山玄武岩具有高含量的Pt、Pd地球化学背景。从峨眉山玄武岩分布区分辨出与基性、超基性侵入岩有关的Pt、Pd地球化学异常,是我国Pt、Pd找矿获得重大突破的关键技术。在贵州西部开展的1∶5万水系沉积物测量显示,采用岩石背景衬值法可有效区分岩性和矿致Pt、Pd异常。在红岩村附近茅口组灰岩与玄武岩接触带及北东向断层的复合部位圈出了浓度分度清晰的As、Sb、Hg、Pb、Cr、Ni、Pt、Pd组合异常,推测在该组合异常下方可能存在一个赋存有Pt、Pd矿的隐伏基性-超基性含矿岩体(脉)。

Compared with the abundance of Pt and Pd in mafic and ultramafic rocks in China,the Emeishan flood basalts have higher geochemical backgrounds. These results suggest that the recognization of the Pt-Pd geochemical anomalies related mafic intrusive bodies with Pt-Pd minerlization is key technology from the Permian Emeishan flood basalt for exploration. Results from a stream sediment geochemical survey at a sampling density of 4- 6 samples per square kilometer show that contrast values,computed Pt and Pd concentrations in stream sediment to those in different rocks,can effectively delineate Pt and Pd geochemical anomalies related mafic intrusive bodies from high geochemical background area. An extensive local geochemical anomalous belt of Pt,Pd,As,Sb,Hg,Cr,Ni and Pb was delineated over the contact area among limestone,basalt and fault of NE direction around Hongyan village using the stream sediment survey at a scale of 1 ∶ 50,000. A new concealed mafic-ultramafic intrusive body containing PGE mineralization was predicted.