秦岭造山带中—新元古代(早期)地质演化

Late Mesoproterozoic-early Neoproterozoic evolution of the Qinling orogen

秦岭造山带是位于中国大陆中部并夹持于华北与扬子陆块之间的大陆造山带,是加里东期至印支期的碰撞造山带。对前加里东期演化虽然亦积累了不少资料,但认识上存在较大分歧。本文着重介绍秦岭造山带自中元古代晚期武关裂谷的打开(1243Ma±46Ma),中元古代末期松树沟洋盆的形成(1084Ma±73Ma～1030Ma±46Ma)以及新元古代早期同造山期花岗岩的侵入(960～840Ma)等自1.25Ga至0.84Ga期间的一系列热-构造事件,反映扬子大陆边缘前加里东期曾经历过一次“威尔逊构造旋回”,表明该区存在中—新元古代造山带的地质记录。但这次造山作用不是华北与扬子大陆的汇聚,而是曾属于扬子大陆边缘的“北秦岭变质地体”与其南的扬子大陆的一次汇聚过程。

The Qinling orogen is a continental orogenic belt sandwiched between the North China block and Yangtze block in the central China continent and a Caledonian to Indosinian collisional orogen. There exist divergent views about the pre-Caledonia evolution of the orogen though quite a number of data are available. This paper mainly introduces a series of tectono-thermal event from 1.25 to 0.84 Ga, such as the opening of a continental rift in the late Mesoproterozoic (1243±46 Ma), the formation of the Songshugou ocean basin in the late Mesoproterozoic (1084±73 to 1030±46 Ma), and the intrusion of syn-orogenic granites in the early Neoproterozoic (960 to 840 Ma), which illustrates that the margin of the Yangtze continent underwent a Wilson tectonic cycle in the pre-Caledonian period. This suggests that there exist geological records of a Meso- and Neoproterozoic orogen in the study area. However, this orogeny did not take place during the convergence between the North China block and Yangtze block but during the convergence between the North Qinling metamorphic terrane that once had belonged to the northern margin of the Yangtze block and the Yangtze block to its south.