构造应力场研究及其在区域地质调查工作中的意义

不少人认为,区域地质调查的主要目的是进行区域成矿预测。为了搞好区域成矿预测工作,必须弄清其地质构造背景,即首先必须弄清该地区的地质构造发展历史。只有确切地弄清区域地质构造的发展历史,才可能深入地探讨在不同时间和不同空间中各类矿产的形成规律,进行矿产予测,指出找矿方向,然而,应该说这方面的研究在区域地质调查中,至今还存在不少问题。

TECTONIC STRESS FIELD AND ITS SIGNIFICANCE IN REGIONAL GEOLOGICAL SURVEY

As a general rule,the main purpose of regional geological survey is to research into the regional minerogenetic prediction. For this aim,the regional geological background i. e. the history of regional geological structure,must be studied,thus the regularity of the formation and distribution of various mineral deposits can be discussed,and the prospect target of mineral deposits can be predicted. However,it is rather difficult to study the history of geological structure,i. e. the geological structural mechanism and deformation history,just using the data of macro- and meso-structures in the regional geological survey. For solving this problem,the research into the tectonic stress field is a selective method,which is combined by the data of macro-,meso-and microstructure. The main content of tectonic stress field is based on the determination of point stress states,i. e. the orientation of principal stress axes and stress magnitude,and the studg of the distribution of tectonic stress of different tectonic stages in a certain region. It is the most important to determine the time,orientation and quantity of the tectonic stress. The collection method of geological data of tectonic stress field,at first,is to combine the data of macro-and meso- structure,and the concerned stratigraphy,magmatism,metamorphism,hydrothermal activity,mineralization and approximately to determine the number and order of tectonic active stage,to divide the tectonic formations,to study their characteristics,and then to make a primary analysis of regional tectonic stress. Depending on the above,certain observation points of small—scale and microscope structures will be arranged,so as to study the structural mechanism and deformation historyin detael. Usually these observation points are well-distributed,their density is one point per 5-9 cm~2 on the map. If the condition of outcrops is rather bad,the observation point density can be decreased to one point per 15 cm~2 on the map,but in any case,it can not be decreased lower than this density. From the data of observation points and regional geology,the map or section of principal stress axes and contours of shear stress can be compiled. Tectonic stress fields,which are resumed by the geological data,can also be simulated by finite element method on the digital computer. The quantitative research into tectonic stress field can improve the research level of geological structural history and of the prediction of structure— mineralization.