Geochemical characteristics and geological significance of the Dianzhong Formation slate from the Sinongduo Ag polymetallic deposit, Xizang

The Linzizong Group is an important product of the India-Asia continental convergence, primarily consisting of a suite of volcanic rocks and a small amount of sedimentary rocks. In this work, a significant amount of slate was discovered in the Dianzhong Formation of the Linzizong Group volcanic rocks from the Sinongduo Ag polymetallic deposit. In order to study the origin of the slate and its indications for mineralization, petrological and whole-rock geochemical studies were carried out on the slate. The results show that the slate exhibits a gradual contact relationship with the Dianzhong Formation volcanic rocks and has a similar geochemical composition of most of the major, rare earth, and trace elements of the volcanic rocks, which is different from that of the slate of sedimentary origin. However, the sub-iron and arsenic contents of the slate are significantly higher than those of the Dianzhong Formation volcanic rocks. Although the arsenic contents of the slate of sedimentary origin are similarly high, there is no clear relationship between the sub-iron and arsenic contents. The results suggest that the protolith of the slate from the Sinongduo Ag polymetallic deposit is the Dianzhong Formation acidic volcanic rocks, and was formed by the metamorphism of the Dianzhong Group volcanic rocks through the reheating of the later magmatic events, contributing to the enrichment of gold in the volcanic rocks. Regional low temperature metamorphism may be a necessary condition for the formation of gold ores in the Dianzhong Formation volcanic rocks.