砾岩沉积与构造环境  

Conglomeratic sedimentation and tectonic settings

作　　者：孟庆任[1,2] MENG Qingren(State Key Laboratory of Lithos pheric Evolution,Institute of Geology and Geophysics,Chinese Academy of Sciences,Beijing 100029,China;College of Earth and Planetary Sciences,University of Chinese Academy of Sciences,Beijing 100049,China)

机构地区：[1]岩石圈演化国家重点实验室,中国科学院地质与地球物理研究所,北京100029 [2]中国科学院大学地球与行星科学学院,北京100049

出　　处：《地质学报》2022年第10期3559-3572,共14页Acta Geologica Sinica

基　　金：国家自然科学基金项目(编号41872239,91955311,9111420404)联合资助的成果。

摘　　要：砾岩是沉积大地构造和盆地研究的重点内容,它不仅记录了物源区的岩石组成,而且在一定程度上反映区域构造演化过程。砾岩形成于不同沉积和构造环境,主要发育在冲积扇、辫状河、扇三角洲和水下扇等沉积体系内。地层中的砾岩层被认为是强烈构造活动的沉积响应,因此常用来限定构造带挤压逆冲和构造抬升的时间和剥蚀过程。然而,这种简单的线性因果思维方式在盆-山体系研究中可能导致错误的构造解释。砾岩沉积过程和空间分布受多种因素制约,包括盆地沉降速率、盆缘构造活动性质、物源区岩石组成、沉积物搬运途径以及气候条件和变化等。合理恢复和解释盆缘构造历史应对砾岩沉积体的时空变化进行详细分析,不应简单地将砾岩沉积与构造活动在成因上直接对应。本文对砾岩沉积环境进行了简要总结,讨论了大陆伸展、挤压和走滑构造环境下砾岩沉积过程以及如何根据砾岩沉积的时空变化来恢复区域构造活动。笔者对“磨拉石”术语的使用进行了讨论,建议避免用该术语来概括不同构造环境下形成的砾岩或粗粒碎屑沉积。Rudite has been the main focus of sedimentary tectonics in that it not only records the detailed constituents of provenances but also reflects tectonic activity in adjacent structural/orogenic belts.Conglomeratic sedimentation occurs in a variety of depositional and tectonic environments,and conglomerates are mostly preserved in diverse alluvial fans,fan-deltas and deep-water fans.Occurrence of conglomeratic facies in stratigraphic successions is commonly taken as a hallmark of tectonic activity,and therefore utilized to constrain both the ages of thrusting/folding and the phases of uplifting and erosion.However,the simple,linear and cause-and-effect rationale of relationships between tectonic activity and conglomerate sedimentation is not often justified,and could lead to misinterpretations of tectonic processes.Sedimentation of conglomerate facies are governed by a number of controlling factors,with subsidence rates probably exerting a primary control on depositional processes and spatial distribution.Subsidence rates are governed by the intensity of tectonic activities at basin edges and conglomerate deposition will also vary in time and space in response to tectonic alternation.Accordingly,the spatiotemporal variations of conglomeratic facies characteristics can provide important clues for restoring tectonic processes at basin margins.This paper offers a brief review of both sedimentary and tectonic environments of rudites,and discusses how the time-space variations of conglomeratic facies are utilized to infer tectonic evolution of basin margins in extensional,contractional and pull-apart settings.The term“molasse”is defined differently in the Chinese literature,and often taken as conglomeratic facies.Based on brief evaluation and discussion of vague usage of“molasse”,it is suggested that the term molasse with tectonic connotation should not be used to cover all types of rudites.

关 键 词：砾岩 沉积环境 盆地构造 沉积大地构造 磨拉石 

分 类 号：P588.212.5[天文地球—岩石学]