滇东北地区中泥盆统缩头山组石英砂岩特征及其沉积环境

Characteristics and sedimentary environments of the quartz sandstones in the Middle Devonian Suotoushan Formation in northeastern Yunnan

滇东北地区具有丰富的石英砂岩矿产资源,主要赋存于中泥盆统缩头山组,矿体厚度大,矿石质量好。本文在大关-彝良地区1∶5万矿产地质调查的基础上,对区内缩头山组石英砂岩的岩石特征、粒度分布、沉积环境进行了详细研究。岩性统计表明,缩头山组含矿层几乎全由石英砂岩(95%)组成,仅含少量的粉砂岩(3%)和泥岩(2%)。粒度分析结果显示,石英砂岩样品分选系数(S0)介于0. 65~0. 87之间,粒度集中分布于1~4"之间,为0. 0625~0. 5mm,缺少拖移总体和悬移总体,跃移总体含量占97%,为典型的前滨带沉积粒度分布特征。

Abundant mineral resources of quartz sandstones occur in the Middle Devonian Suotoushan Formation in northeastern Yunnan.The ore bodies have tremendous thickness and good quality,and may serve as the high-quality raw materials of the high-purity quartz sandstones.The present paper deals in detail,on the basis of 1∶50 000 mineral resources and geological surveys in the Daguan-Yiliang region,northeastern Yunnan,with petrological characteristics,grain size distribution and sedimentary environments of the quartz sandstones in the Suotoushan Formation.The lithological statistics indicate that the host rocks almost consist of quartz sandstones(95%),with minor amount of siltstones(3%)and mudstones(2%).Grain size analysis shows that the sorting coefficients(S 0)of quartz sandstones range between 0.65 and 0.87,and the grain sizes are concentrated between 1 and 40x0E?SymbolFA@0x0F(0.0625-0.5mm).The traction and suspension populations are lacking,and the saltation populations reach up to 97%.The above-mentioned results of research suggest a typical foreshore sedimentary environment of the quartz sandstones in the Suotoushan Formation in northeastern Yunnan.