秦岭造山带泥盆纪古海洋研究

DEVONIAN PALEO-OCEAN OF QINLING OROGENIC BELT

泥盆纪是秦岭古海洋演化的重要转折时期。泥盆纪秦岭古海洋位于华北、扬子两板块之间、北纬８°～１５°的低纬地区。继承加里东晚期北秦岭造山带的隆升，北秦岭和中秦岭大部分地区未接受早泥盆世沉积。持续的海侵使秦岭古海域逐渐向北扩展。秦岭微板块的北移产北秦岭造山带南缘形成了同造山的前陆拗陷盆地，盆内充填了复理石和磨拉石沉积，南秦岭沿勉略带的继续开裂形成深水裂陷槽，槽内充填了深水盆地钙泥质和拉斑玄武岩、碱性玄武岩沉积，位于前陆盆地和裂陷槽之间的秦岭微板块为稳定克拉通型的古岛屿和台地－生物建隆沉积，这种南张北压的构造机制控制了秦岭造山带泥盆纪的古海洋格局和演化历程。

Devonian is an important transitional period in Qinling paleo-oceanic evolution from Caledonian to Hercy-Indosinian stages.Qinling paleo-ocean lay between north China and Yangtze plates in low paleolatitude area of N8°-15°during Devonian. The collision of North China plate and Qinling microplate formed the North Qinling orogen in Late Caledonian stage. Continuing the uplift of North Qinling orogen, most areas of Middle Qinling and North Qinling were hilly or paleoland in early stage of Eariy Devonian. There was a successive transgression during Devonian. Northward movement of Qinling microplate resulted in the forming of synorogenic foreland basin in southern edge of North Qinling belt, filled with flysch and molasse deposits. Opening along Mian-Lue belt in South Qinling formed a rift trough, filled with deep-water mudstone, limestone and tholeiites, alkali-basalts. Qinling microplate was a stable craton in which paleoisland's terrigenous clasties and platform-reef's carbonates was deposited.The structural mechanism of extension in South Qinling and compression in North Qinling controlled Devonian paleo-ocean frameword and evolution of Qinling orogenic belt.