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广西东平锰矿是一个大型红土型锰矿床,分为原生锰矿含矿层和次生锰矿含矿层。由于历史原因,绝大部分学者将原生锰矿含矿层的地层归属浅水台地相的北泗组。区调中,根据矿区实测剖面的岩石组合、沉积相特征及古生物特征与标准剖面的对比,将赋矿地层归属于石炮组,并新建东平层,代表含锰地层。在赋矿地层下部的泥岩层中采获Claraiasp.等早三叠世双壳类及菊石化石,LA-ICP-MS法测得赋矿地层顶部火山碎屑岩中锆石U-Pb年龄为251.5±2.5Ma,在火山碎屑岩层之上采获中三叠世双壳类和菊石,确定锰矿赋矿地层的时代为早三叠世中晚期。
The Dongping manganese deposit in Guangxi is a large-sized lateritic manganese deposit, which is divided into primary manganese ore-bearing layers and secondary manganese ore-bearing layers. Due to historical reasons, the vast majority of scholars belonged to the North Sisha Formation of Shallow Water Platform in the strata of the primary manganese ore-bearing formation. According to the adjustment of the lithofacies, sedimentary facies and palaeontological features of the measured sections in the mining area, the ore-bearing strata are assigned to the Shek’ai Formation and a new east-level formation is formed, representing the manganese-bearing strata. The Early Triassic bivalves and ammoniated fossils of Claraiasp. Were collected from the mudstone layers in the lower part of the ore-hosting strata. The zircon U-Pb ages of pyroclastic rocks at the top of the ore-bearing strata were measured by LA-ICP-MS 251.5 ± 2.5Ma. Middle Triassic bivalves and ammonites were collected above volcaniclastic rocks, and the age of the ore-bearing strata was determined to be mid-early Triassic.