FRACTURED TECTONICS OF CHROMITITES OF THE MAIN SARANOVSKOYE DEPOSIT (PERM KRAI)

Abstract

The Main Saranovskoe deposit is one of the largest chrome deposits in Russia. The chrome ore bodies are localized in the ultramafites of the Northern Saranovsky massif which has been studied since 1907. The research revealed that the massif is similar to the Bushveld stratiform complex. Unlike other layered plutons, the Northern Saranovsky massif has a large amount of chrome ore bodies as compared to ultramafic host rocks. As many studies have shown, the chromitites of the Main Saranovskoe deposit are severely tectonized. The strike and dip of the ore bodies is complicated by numerous faults. These observations imply that the massif is a fragment of a large stratified pluton intruded into the Proterozoic metasedimentary unit. The fracturing reflects the massif intrusion conditions and provides new petrogenetic information on the relevance of our study of the tectonic fractures of the Saranovsky massif. Studies have been made on the fracture and furrow displacement orientations along the planes in the main ore bodies: western, central and eastern, within the two parts of the deposit. The local stress tensor has been reconstructed using the Angelier method in the Win-Tensor program. It has been stated that the chromitites studied contain 3–4 main fracture systems whose orientation varies together with the orientation of the ore bodies. The main compressive stress axis is oriented subvertically both in the central and southern parts of the deposit, and the main tensile stress axis forms an acute angle with the ore body contacts in the center of the deposit and is oriented subperpendicular to them in the southern part. It has been concluded that fracturing of the chrome ore bodies in the Main Saranskoe deposit took place during the massif motion into the upper crustal horizons with the subvertical orientation of the ore bodies remained unchanged. This casts doubts on the probability of formation of the Northern Saransky massif as a result of gravity differentiation of magmatic melt, since in this case the ore bodies should have undergone a vertical turn which is not exhibited by their fracturing.