秦岭早古生代沉积作用与构造演化

根据对秦岭及其两侧地台区沉积体系与旋回沉积的分析，认为该区在早古生代总体上处于板块的扩张阶段，其中巨厚的台地碳酸盐岩的广布的远洋沉积是其典型岩相。早奥陶世阿伦尼克中期华北地台南的一度隆升与剥蚀，标志着俯冲作用开始，但未发现加里东期碰撞造山作用的证据。该区晚奥陶世一志留纪大规模的海退主要是全球海平面下降的结果，与碰撞造山人关系不大。

EARLY PALAEOZOIC SEDIMENTATION AND TECTONIC EVOLUTION IN QINLING

The Qinling orogenic belt has a complex evolutionary history. During early Palaeozioic time, the Southern Qinling was a passive continental margin of the Yangtze Plate,whereas the Northern Qinling became an active continental margin with the northward subduction of oceanic crust to the south. The belt underwent two great transgressive-regressive events. The first event occurred in the Cambrian and up to the Early Arenig, and the second one took place in the Late Arenig up to the Silurian. Thick platform carbonates in Zhenan-Xichuan of the Southern Qinling and the North China Craton, and widespread pelagic and hemipelagic sediments composed of radiolarian chens, siliceous and carbonaceous slates in oceanic or rift basins, suggesting that the Qinling area was in general in a spreading stage during the Early Palaeozoic Era. The uplift and denudation in the southern margin of the North China Craton during the Middle Arening and the appearance of a deep-water rift basin in the southwestern margin of the North China Craton in the Caradoc might be related to plate subduction. From the Late Ordovician to the Silurian, a large-scale regression occurred in this area. In the wide area,south of the Shangdan suture zone, the tectonic deformation and foreland basin deposits related to Caledonia movement have not been found and the Silurian sediments are still characterized by quartz sandstone with high maturity. Thus, we consider that the collision orogenesis did not occurred in this time, and this regression was probably related to the global sea--level descending.