韧性构造地质事件时限的确定——一种构造物理定年方法探索

Determination of the Time Duration of Ductile Structural Event: a New Tectonophysics Dating Method

韧性剪切带活动时限 (持续的时间 )的研究 ,可以为相关地质事件提供重要的制约条件。由于直接测定韧性构造事件的时限尚没有一种成熟的方法 ,本文试图依据韧性剪切带中构造岩及其应力矿物所反映的物理化学信息 ,以求得时限。现主要讨论构造应变速率法 ,具体的方法和步骤 :首先 ,通过计算差异应力求得流变速率 ;其次 ,通过计算体积因子来求算有限应变 ;第三 ,应用有限应变量与流变速率来求得地质事件的过程时间。并以宿松韧性剪切带型磷矿为例 ,获得韧性剪切带形成的时限为 10 0± 10万年。

The study of active time limit (duration) of ductile shear belt can reveal the important restraining condition of geological event. However, there was no matured method to determine the time duration of ductile structural event directly. In this paper we will present some preliminary results of a study aimed to solve this problem based on the chemical and physical information of structural rocks and stress minerals in the ductile shear belt. A specific dating method, i.e. the structural strain rate method, has been developed and used in our project. The application of this dating method includes following steps: 1. to obtain the strain rate by calculating the paleo stress; 2. to attain the restrained strain by calculating the volume factor; 3. to achieve the time duration of geological event on the base of restrained strain and strain rate. The structural strain rate method has been applied to date the Sushong phosphorous deposits of ductile shear belt type and a duration time of 1±0 1Ma was obtained for the ductile shear belt.