Geochemical characteristics and significance of major elements, trace elements and REE of NM copper polymetal deposit in Laos

Abstract

The NM copper polymetal deposit is located in the middle north part of the Truong Son metallogenic belt in Laos, which is the skarn-typed deposit and located in the contact between Indosinian granite and Lower Carboniferous limestone. All the ore-bodies in NM deposit can be divided into four types according to their occurrences: I copper ore-body as the massive restite developed in inner contact near the granite in north part; II-1 zinc-copper ore body and II-2 copper-iron ore body developed within contact between the granite and carbonate rocks, III copper-zinc ore body developed in the cranny among the southern carbonate stratum, indicating that all the ore-bodies were related to Indosinian granite emplacing into the Carboniferous limestone and causing the metallogenic system from closed state getting into half open state. The geochemical characteristics and mineral assemblages of them showed that all the orebodies in NM deposit derived from a similar origin and their ore-forming fluids with the evolution trend from reductive state in early stage to oxidative state in later stage were mainly related to the coupling interaction between post-magmatic hydrothermal fluid and basin fluid.