造山带研究中有关复理石和磨拉石的几个问题

在造山带研究中,碰撞方式和时限的争议是全球造山带研究中的一个共同现状或面临的难题。利用复理石和磨拉石时代来限定碰撞时限是造山带研究的一项重要内容。本文首先综述了复理石和磨拉石从提出到广泛应用以及不同历史时期被赋予的构造含义;其次,根据其可能发育的构造环境,指出复理石和磨拉石纪录造山带的相关信息及其演变过程。被动陆缘复理石可能纪录了参与碰撞拼贴块体的亲缘性,而且被动陆缘、活动陆缘或者岛弧环境的复理石均形成于碰撞作用之前,因此最年轻的复理石时代可提供碰撞时间的下限;(周缘)前陆盆地的磨拉石形成于碰撞造山作用过程中,因此其最早的磨拉石沉积时代可用于限定碰撞时间的上限。从复理石到磨拉石地层的渐变过程(连续沉积)指示了碰撞构造事件的发生、以及之后的碰撞造山作用是均变过程,会发育不同尺度规模的不整合。因此,造山带中的不整合未必代表有重大构造事件的发生,而连续沉积并不表明没有大的构造事件。

Discussions on some basic problems in the research of orogenic belts concerning on flysch and molasse

The pattern and timing of collision are long-term controversies in orogenic research. Flysches and molasses, as one of the most important recorder, have been applied to constrain the collision timing. In this paper, we review research history and their different tectonic meaning in geosyncline-plat-form theory and plate tectonic theory, and then followed by an effort to anatomize their tectonic implications. Flysches in passive margins, active margins or arcs related tectonic settings are deposited before collision, and molasses in peripheral foreland basin after the collision. The youngest flysch could provide information on the maximum collision timing while the oldest molasses in peripheral foreland basin provide information on them-in-collision timing. The transition of sedimentary succession from flysches to molasses indicates that the sedimentation may be continuous during huge tectonic events and thus the collision orogeny is a uniformitive process after the collision event.