RESTORATION OF DEVONIAN-TRIASSIC SEDIMENTARY ENVIRONMENT AND BASIN TECTONIC EVOLUTION IN LINTAN AREA, WEST QINLING

Based on the characteristics of major, trace and rare earth elements of the fine clastic rocks in the Devonian-Triassic sedimentary basin in Lintan area, West Qinling Mountains, the sedimentary environment and tectonic evolution model are established through tracing the background of source region and inversion of the parent rock properties. It is believed that the provenance of the sedimentary basin generally comes from the northern part which underwent continental-lacustrine deposition in the Late Devonian, the shore beach facies-warm and humid coastal bay(lagoon or tidal flat) facies-shallow marine shelf facies deposition in the Carboniferous, and the shallow marine shelf-barrier reef formation within shallow marine shelf in the Permian; while the southern sedimentary basin is a stable carbonate platform facies. In the Triassic, the basin experienced complex sedimentary environmental changes, that is, turbidity deposition on continental slope-turbidity deposition on continental slope (semi-deep sea)-littoral neritic sea. The formation and evolution of sedimentary basin can be divided into three stages, including the stable development of passive continental margin intraplatformal basin and platform, formation and evolution of back-arc basin, and superposition of back-arc foreland basin.