攀西地区红格层状岩体的地球化学特征  

Geochemistry of the Hongge layered intrusion in the Panxi area

作　　者：胡素芳[1] 钟宏[1] 刘秉光[1] 周新华[1] 

机构地区：[1]中国科学院地质与地球物理研究所岩石圈实验室,北京100029

出　　处：《地球化学》2001年第2期131-139,共9页Geochimica

基　　金："九五"攀登计划! A- 25项目 01- 04专题

摘　　要：红格岩体赋存有大型钒钛磁铁矿床，在橄辉岩相带和辉石岩相带底部有铂族元素 (PGE)的矿化，是攀西层状岩体中重要的岩体之一。系统分析了红格层状岩体不同岩相带的微量元素和稀土元素特征，探讨了岩浆的结晶分异演化过程，提出岩体主体上是由一个岩浆房经正常的结晶分异形成的，底层的硫化物富集带和中上层位的钒钛磁铁矿是岩浆结晶分异产生的堆积相，并非是岩浆多次脉动式补给的结果。The Hongge intrusion, which hosts super- large V- Ti magnetite deposits and shows PGE mineralization at the bottom of the peridotite- pyroxenite zone, is one of the most important mafic- ultramafic layered intrusions in the Panxi area. In this paper, major, trace and rare earth element contents in each zone of the intrusion are systematically analyzed. The results indicate that the contents of Fe, Ti are higher and those of Si and Mg are lower than other mafic- ultramafic rocks. There is an evolution trend of from Mg- rich to Fe- rich and Na- rich from peridotite- pyroxenite zone to pyroxenite zone and to gabbro zone. Generally the Hongge layered intrusion shows REE- enrichment pattern with a characteristic of the ratio of La/Yb from 3.66 to 80.47 and averaging 18.24. But the degree of REE- enrichment varies in different zones. The differentiation extent of REE, LREE and HREE increases from the peridotite- pyroxenite zone at the bottom to the pyroxenite zone in the middle and to gabbro zone in the upper of the intrusion with the ratio of La/Yb varying from 9.64 to 13.4 and to 42.61, La/Sm from 1.70 to 3.14 to 5.34,Gd/Yb from 5.32 to 4.86 to 8.34. Large ion lithophile elements shows enrichment pattern relative to prime mantle. The intrusion evidently shows Ti positive abnormality. The contents of Cr are 315μ g/g, 253μ g/g and 148μ g/g in the peridotite- pyroxenite zone, pyroxenite zone and gabbro zone, respectively, with a decrease from the bottom to the top of the intrusion. The contents of Ni and Cu are high in peridotite- pyroxenite and pyroxenite zones and are evidently low in the gabbro zone, and the contents of Cr and Ni are directly in proportion to MgO. All the characteristics listed above are consistent with crystallization differentiation evolution and indicate that the Hongge intrusion is mainly formed by crystallization differentiation from one magma chamber. The PGE- enrichment layers and V- Ti magnetite layers are similar to other cumulus minerals, such as olivine， pyroxene and plagioclase forme

关 键 词：地球化学 结晶分异 岩石成因 红格层状岩体 四川省 微量元素 稀土元素 侵入岩 

分 类 号：P588.12[天文地球—岩石学] P595[天文地球—地质学]