Characteristics of tectonic deformation in the Tạ Khoa area, Bắc Yên District, Sơn La Province

Vũ Xuân Lực, Trần Thanh Hải,
Đinh Hữu Minh, Trần Quang Phương

The Tạ Khoa area, Bắc Yên District, Sơn La Province lies in the West Bắc Bộ Structure, a region of very complicated geological structure. It is composed of many geological formations with different compositions, ages, origins and characteristics of deformation and metamorphism bearing the polyepisodic character. It contains various mineral manifestations, among them the Bản Phúc copper-nickel deposit is of economic significance.

Rock associations in the studied area suffered different deformation impacts, among them the oldest rocks suffered at least 5 tectonic deformation phases. Each of these phases is characterized by one or an association of structures of the same origin, formed during a same time, a same deformation regime and representing a stage of geological development of regional character. Early phases (phases 1 and 2) took place in a completely ductile environment, while later phases (phases 3 and 4) – in a ductile to ductile-brittle environment and latest phases – in the brittle environment. Some structure types have close relation and controlling role to copper-nickel mineralizations in the area, among them the deformation phase 1 controlled the formation of Cu-Ni accumulation in slip zones surrounding the Bản Phúc ultramafic massif. The deformation phase 3 led to the reconcentration of mineralization in some ductile-brittle slip zones of NW-SE direction in the northeast of the studied area. The detailed structural interpretation has not only an important role in the interpretation of the history of regional geology, but also in the prediction of metallogenic potential and orientation of Cu-Ni prospecting in the Tạ Khoa and adjacent areas.

Người biên tập: Trần Văn Trị