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

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。

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

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 highquality 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 (S₀) of quartz sandstones range between 0.65 and 0.87,and the grain sizes are concentrated between 1 and 4 "(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.