引用本文：张英利,贾晓彤,王宗起,陈木银.2018.米仓山地区早寒武世仙女洞组沉积物源新认识：沉积学、重矿物和碎屑锆石年代学的证据[J].地质学报,92(9):1918-1935. ZHANG Yingli,JIA Xiaotong,WANG Zongqi,CHEN Muyin.2018.New Insights into Provenance of Early Cambrian Xiannüdong Formation in the Micangshan Area: Evidence from Sedimentology,Heavy Mineral and Detrital Zircon Chronology[J].Acta Geologica Sinica,92(9):1918-1935.
Abstract:It has long been regarded that the Lower Cambrian rocks were mainly from Hannan Oldland and/or Motianling Oldland in the Micangshan area, but this idea may be challenged. The Xiannüdong Formation in the Micangshan area consists of oolitic limestone, limestone breccias, and nodular limestone. According to sedimentary facies distribution, paleocurrent direction restored by cross bedding, heavy mineral assemblages and detrital zircon LA-ICP-MS U-Pb dating, we comprehensively analyzed the source areas of the Xiannüdong Formation. The temporal and spatial distribution of sedimentary facies and the direction of paleocurrents indicate that the provenance direction of the Xiannüdong Formation mainly came from the northwest and southwest, not from northwest and/or northeast judged by other predecessors. The assemblage of detrital heavy minerals, including zircon, apatite, leucoxene, chromium spinel and magnetite indicates that the sediments mainly derived from magmatic rocks, and partly from mafic magmatic rocks. LA-ICP-MS U-Pb dating for three samples of detrital zircons from the Xiannüdong Formation yielded 172 sets of effective ages. The concordia ages of detrital zircons indicate that the provenance was mainly from 744~896 Ma and 1755~2493 Ma rocks. Combined with facies distribution, paleocurrent directions, heavy mineral assemblages and detrital zircon dating, it can be concluded that the Xiannüdong Formation derived mainly from (1) the Motianling Oldland in northwest, which includes volcano-sedimentary rocks of the Bikou Group, Hengdan Group and Yudongzi Group, and Neoproterozoic intrusive rocks, and (2) the Kangdian Oldland in southwest, which consists of granite, rhyolite and diabase.