对新疆北部蛇绿岩及相关问题的思考和认识

The consideration on ophiolite and interrelated issue in northern Xinjiang, northwestern China.

蛇绿岩是作为大陆古板块划分及洋壳存在的重要佐证,同时也是许多地质问题争论的焦点之一。关于新疆北部地区大地构造单元的划分,尽管从不同理论、不同专业角度进行了许多研究和论述,但也因对区内蛇绿岩的认识不同而仍存在诸多争议。本文针对以区内蛇绿岩形成时代来确定洋盆出现所存在的一些可变因素的阐述,提出在新疆北部地区于震旦纪-石炭纪期间可能只存在一个水域相通的统一大洋—准噶尔-天山洋的认识。并以此为基点,对新疆北部地区的构造单元进行了初步划分,划分出两个被动陆缘带和三个弧盆带,同时将其构造演化概括为陆壳拉张(Z-(?))、洋盆形成(O-S)及洋盆消减(D-(?))三个阶段。

Ophiolite is an important evidence which divides continental palaeoplate and proves existence of oceanic crust, similarly, it is one of the points at issue for more geological problems. Although quite a number of investigations and discriptions have been published based on different theories and disciplinesk there still exist a lot of controversies and different understandings about the ophiolite in northern Xinjiang region. In the region, in view of existent variable factors of oceanic basin formation age determined by ophiolite formation age, we propose that there is probably an united ocean during Proterozoic and Paleozoic (Neoproterozoic-Carboniferous) in northern Xinjiang region, we call it as Junggar-Tianshan ocean. In this paper, we take tentatively a division about the regional tectonic units in view of existing only an united ocean. We divide the region into two passive continental marginal zones and three arc-basin zones, and think that these structural units underwent three stages: continental crust stretching (Neoproterozoic-Cambrian), oceanic basin formation (Ordovician-Silurian) and oceanic basin subduction (Devonian-Carboniferous).