柴达木地块与喜马拉雅地体间早白垩世以来南北向缩短量的估算

Longitudinal Shortening Amount between the Himalayan Terrain and the Qaidam Block Since the Early Cretaceous

根据古地磁数据,笔者计算了柴达木地块和喜马拉雅地体早白垩世以来的南北向运移量和其间的南北向距离缩短量,结果表明:①早白垩世后喜马拉雅地体快速向北运移,其运移速率大于柴达木地块同时期的运移速率,早自垩世以来,两者间南北向距离总计缩短了约5522km②印度地块与欧亚大陆自50 Ma碰撞以来,柴达木地块与喜马拉雅地体间南北向上陆壳缩短了约1364 km,这一缩短量支持青藏高原隆升的“挤压、缩短、增厚”模式;③中生代以来柴达木地块的缓慢北移表明了其受特提斯演化的影响。在柴达木地块与其以南喜马拉雅地体向北运移的同时,它们运移速率的明显差异还显示了柴达木地块对其以南块体向北运移的阻挡作用。

A contrast of the longitudinal movement of the Himalayan terrain and the Qaidam block and the shortening amount between them since the Early Cretaceous shows that (T) The Himalayan terrain began to shift northward rapidly after the Early Cretaceous, and the shifting rate was greater than that of the Qaidam block. The total shortening amount between them since the Early Cretaceous reaches ca. 5522 km. (2) The longitudinal crust shortening amount between them is ca. 1364 km in total since the collision of the Indian with Asian continents at 50 Ma. The shortening amount supports the compression-shortening-thickening pattern of the Qinghai - Tibet Plateau uplift. (3) The slower northward shift of the Qaidam block since the Mesozoic shows that it has been subjected to the evolution of the Tethys. The evident difference in the shift rate between the Himalayan terrain and the Qaidam block indicates that the latter not only shifted northward synchronously with the former but also obstructed the northward shift of blocks to its south.