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.