会理-会东及邻区中元古代东川群层序地层分析

广泛出露于四川会理－会东及云南东川等地的中元古代东川群地层，由于其中赋存有丰富的矿产资源，包括铜 矿、铁矿等而倍受重视。前人对其地层划分、岩石学及其含矿性等进行了系统的研究，取得了一系列的成果和认识，但尚未对其进行系统的层序地层研究。本文在野外地质考察的基础上，通过室内的详细分析，建立了东川群的沉积层序，即１个Ｉ级层序（时限约２．３亿年），１２个Ⅱ级层序。

THE STUDY OF THE SEQUENCE STRATIGRAPHY OF THE DONGCHUAN GROUP DURING MESO-PROTEROZOIC IN HUILI-HUIDONG AND DONGCHUAN AREAS

The Meso-Proterozoic sedimentary basin in Huili-Huidong and its adjacent areas is an inheritied rift basin, where the Dongchuan Group was deposited. The Dongchuan Group can be divided from bottom to top,into the Yinming, Louxue, Heishan and Qinglongshan Formations.Ten sedimentary facies in the Dongchuan Group have been distinguished in terms of palimpsest sedimentary structures, lithologic features and depositional cycles. They are the allu-ial fan facies, littoral-shallow sea facies, shallow shelf facies, tidal flat-estuary facies, carbonate platform facies, shoal facies, biohermal facies, slope facies, shallow-sea basin facies and abyssal asin facies. According to the features of sequence boundary characterized by the paleo-weathering crust and paleo-karst as well as condensed section consisted of the carbonaceous shale, carbonaceous siliceous rocks and siliceous rocks, 12 depositional sequences have been eastablished, 2 depotional sequences in Yinming Formation, 2 depotional sequences in Louxue Formation, 4 depotional se-quences in Heishan Formation and 4 depotional sequences in Qinglongshan Formation. The features of depositional sequences showed that 1)the study area has experienced two periods of sedimentary evolution characterized by the variation from the terrigenous to carbonate sedimentation; 2 ) the copper bearing strata is at the bottom of the Louxue Formation in Dongchuan, Tongtan and at the top in Yimen area, reflecting the transgression from north to south;3) the extensional activity in study area during the Late Meso-Proterozoic took place inten-sively toward south and in north direction;4) the Dongchuan tectonic movement and Sanfengkou movement of Manyingou movement are problematical. In fact, these structural boundaries named by former geologists were formed by the paleo-exposure and paleo-solution during the sea-level falling, characterzied by the paleo-weathering crust and paleo-karst.