澜沧江断裂带的新生代走滑运动学特点

The Cenozoic Strike-slip Kinematics of the Lancang Jiang Fault Zone

通过对澜沧江断裂带北、中、南段新生代构造形迹的运动学解析,结合前人工作,论证了澜沧江断裂在新生代早期(古新世—中始新世末)、中期(晚始新世—渐新世末)、晚期(中新世—第四纪)的走滑运动序列为:中、南段,右行→左行→右行;北段,左行→左行→右行。研究表明,澜沧江断裂带早期主要表现为中、南段的右行逆冲和北段的左行逆冲,与同期发生的昌都—思茅地体颈缩事件相对应,其地球动力学背景与太平洋板块向西推挤作用以及扬子—华南板块与印度板块发生的强烈东西向碰撞挤压有关;中期,整个断裂发生左行逆冲,其地球动力学背景与南海盆地的扩张作用及其扬子—华南板块相对于印度板块北移所致的左行扭动相适应;晚期,整个断裂右行走滑,与太平洋构造域的南海盆地扩张终止,昌都—思茅地体整体向南东逃逸相适应。

Based on kinematic analysis of the Cenozoic Lanchangjiang structure features, we proved that the Lancangjiang fault zone has the following Cenozoic strike-slipmovement sequence. During the period from the early Cenozoic (Paleocene to late Meso-Eocene) → middle Cenozoic (late-Eocene to late Oligocene) → late Cenozoic (Miocene to Quaternary) , the movement was from right lateral slip→left lateral slip→right lateral slip in the middle and southern parts; and from left lateral slip→left lateral slip→right lateral slip in the northern part. It is further pointed out that in the early period the right slip-thrust movement of the middle and southern parts and the left slip-thrust movement of the northern part answered to the necking event of the Qamdo-Simao terrane caused by the collision between the Yangtze-Huanan (Southern China) and the Indian plates and the westward push and squeeze of the Pacific plate; in the middle period, the left slip-thrust movement of the whole fault was in accord with the left shearing of the Yangtze-Huanan plate opposite to the Indian plate caused by the extension of the South China Sea basin; and in the late period, the right lateral strike-slip movement of the whole fault responded to the escape event of the whole Changdu-Simao terrane with the cease of the extension of the South China Sea basin in the Pacific structure domain.