THE EFFECT OF MICROFRACTURING IN GABBRO-DOLERITES ON THEIR PHYSICAL PROPERTIES

Abstract

Simple and cheap methods for the study of building stone deposits for the production of blocks of commercial size can be used to make geological work more efficient. However, physical processes in a massif are hard to understand when doing geophysical research, and the effect of microstructural parameters, mainly the microfracturing of rocks, on geophysical field indices is poorly understood. The authors have studied the impact of microfracturing on the physico-mechanical properties on coarse- to giant-grained rapakivi granites from the Salmi massif, Fennoscandian Shield. The goal of the present study is to assess the physical and physico-mechanical parameters in fine- and medium-grained quartz-free rocks. The authors have studied the various physical and physico-mechanical indices of gabbro-dolerites from the Ropruchei sill (Fennoscandian Shield, within the deposit prospected and revealed the effect of microfracturing indices on them. The study of these properties have shown that microfracturing in gabbro-dolerites is an essential factor which forms the physical parameters of a rock. The testing of this rock type has shown the rate of travel of an elastic wave is clearly related to the microfracturing of samples. The magnetic properties of gabbro-dolerite are due to high concentrations of titanomagnetite, the mineral grains of which formed upon the crystallization of magma during its interstratal intrusion. The distribution of titanomagnetite, based on size and concentration in the rock, depends on liquation conditions in the active stress field. The dependence of the microfracturing of gabbro-dolerites on their iron concentration (FeO+Fe2O3) shows that these «damages» appeared at a ‘brittle” stage in the evolution of the massif in the form of microfractures, the structural parameters of which have inherited the parameters of the stress and deformation field which existed in the massif at that time and which accumulated iron. As a result, microfracturing has a considerable effect on the parameters of the electromagnetic indices of the massif by accumulating iron oxides in the pores, and the higher the index, the higher the geophysical medium indices. Understanding of the physical problem, which accompanies the formation of a gabbro-dolerite complex, helps conduct the geophysical study of a massif, interpret data more objectively and more accurately delineate massive zones in the medium that could be used as high-quality building materials.