增生型造山带结构解析与时空制约

增生型造山带记录复杂的板块汇聚过程,增生造山作用演化历史漫长,发育多期次造山作用.就增生型造山带的特征与复杂性进行简要总结与评述,并讨论增生造山作用时空分析思路.增生造山作用是多种性质(汇聚、转换和离散)的板块边缘,沿一个核心大陆边缘最终发生复杂相互作用动力学过程的总和.弧前发育增生杂岩和各种混杂岩或者构造岩片,上叠有以弧前盆地为代表的各类沉积盆地,共同制约增生过程的时空演化特征.增生型造山带多发育多岛海复杂古地理格局,增生造山作用具有多组分、多岛海、多盆地类型、多种性质的岩浆活动、宽阔的增生杂岩、多俯冲极性、多地体拼贴、长期演化与面状增生等特性.以古地磁、古地理、古生物与古气候等资料为基本依据,划分一级大地构造单元界线.以构造地质解析和关键地区详细的地质填图,结合物质成分和年代学分析,进行二级大地构造单元及其相互关系的详细解剖.卷入增生造山事件中最年轻的地质体或者组分,提供了该期增生事件时限的下限;卷入增生造山事件中最年轻的角度不整合,以及最年轻的高压-低温变质事件,可能提供了最晚增生事件时限的下限;而未卷入增生造山事件中最老的区域性角度不整合,则可能提供了最晚增生事件时限的上限.

Structural Analyses and Spatio-Temporal Constraints of Accretionary Orogens

Accretionary orogens record complicated geological processes during plate convergence, and are characterized by long evolutionary history with multi-stage orogenesis. This paper presents a brief summary and review on the characteristics and complexity of accretionary orogens, and also discusses the methods of analyzing the spatio-temporal evolution of accretionary orogeny. Accretionary orogeny is here defined as a collection of interactions between various types (convergent, transform and divergent) of plate boundaries along a host continental margin with multiple orogenic phases. The forearc region of an accretionary orogen includes accretionary complexes with overlying sedimentary basins such as forearc basin and wedge-top basin, which together constrain the spatio-temporal evolution of accretionary processes. Accretionary orogens are characterized by complicated archipelagic paleogeographic patterns with the development of different types of basins, diverse magmatism, wide accretionary complexes, multiple subduction polarity, multiple terrane accretion, secular evolution and planar accretion. By using the paleomagnetic, paleogeographic, paleontological and paleoclimate data, first-order tectonic units can be deciphered. Based on structural analysis and detailed geological mapping, in combination with material and geochronological analysis, second-order tectonic units can be divided. The lower time limit of accretionary events can be discriminated by defining the youngest components, unconformities, and high-pressure metamorphic events involved in the accretion; while the upper time limit relies on the oldest unconformities which are not involved in the accretion.