岩石矿物学杂志2025，Vol.44Issue(3)：522-534,13.DOI:10.20086/j.cnki.yskw.2025.3118
滇西三台山橄榄岩风化壳中的硅质岩和铁锰氧化物成因及其意义
The genesis of cherts and ferri-manganese oxides in the weathering crust on the top of the Santaishan peridotites,western Yunnan and their implications
摘要
Abstract
Many red chert blocks and some irregular stripped manganese-oxide aggregates and crusts are developed in the laterite on the top of the Santaishan peridotites,western Yunnan.Those cherts and manganese nodulars are unlike the marine facies ones in shape,chemical compositions and mineral assemblage.Those dark manganese-oxide aggregates and crusts can be classified as ferri-manganese and cobalt-manganese oxides.The energy spectrum analytical results show the ferri-manganese oxides are complicated and nonuniform in their chemical compositions,with main Mn and Fe and minor Al,Co,Ni,K and Ba elements.The separation degree between Mn and Fe ele-ments is low with Mn/Fe ratios of 0.1～12.6.The cobalt-manganese oxides consist of main Mn,Co,Al,Ni and minor K,Ca and Si,showing high separation degree between Mn and Fe.X-ray powder diffraction analyses show that the ferri-manganese oxides occur as hollandite in crystal structure,and coexist with cryptocrystalline hematite,goethite and clay minerals,having capability of enrichment in Al,K,Ba,Co and Ni elements.The cobalt-manga-nese oxides is with lithiophorite crystal structure,and is associated with cryptocrystalline hematites and cherts,having capability of enrichment strongly in Co,Al and middle in Ni elements.Based on the methods of energy spectrum,microprobe,X-ray powder diffraction,and whole rock chemical analyses,we conclude that those manga-nese-oxide aggregates and crusts are generated in the supergene conditions of long-lasting leaching by atmospheric precipitation,acidification and redox on the peridotites,where Ca and Mg in the silicate minerals are lost and Si,Fe and Al are residual.Silicic acid was retained and altered to cherts due to poor drainage condition.Iron-and manganese-oxide gels were precipitated as aggregates and crusts under the alternation of wetting and drying cli-mates.The supergenesis has transformed the peridotites to Fe,Al,Ni,Co,Cr,Mn,Sc and Y enriched laterite with potential economic values.关键词
硅质岩/铁锰氧化物/地幔橄榄岩/表生作用/三台山/滇西Key words
chert/ferri-manganese oxide/peridotite/supergenesis/Santaishan/western Yunnan分类
地质学引用本文复制引用
任玉峰,戚学祥,王涛,吉风宝,韦诚,刘旭峰..滇西三台山橄榄岩风化壳中的硅质岩和铁锰氧化物成因及其意义[J].岩石矿物学杂志,2025,44(3):522-534,13.基金项目
中国地质调查局地质调查项目(DD20240204901,DD20221630) （DD20240204901,DD20221630）
国家自然科学基金项目(91755101) Geological Survey Project of China Geological Survey(DD20221630,DD20230340) （91755101）
National Nat-ural Science Foundation of China(91755101) （91755101）
