Abstract:Laozhaiwan gold deposit is one of the finegrained gold deposits with large scale in "DianQianGui Golden Triangle Area". Many geological work have been carried out in this deposit in detail, but mostly focus on geological characteristics and the origin. Little research has been carried out on geochemical characteristics of the elements in the process of transformation. Since the secondary oxidation in the later stage will destroy the primary structure of monazite, the formation is quite controversial. In this paper, through the electron probe test of monazite in Laozhaiwan gold mining area, the internal structure, mineral composition and rare earth element geochemical characteristics of monazite have been analyzed. As showed by the results, there is a new thoriumpoor monazite at the edge of the preexisting thoriumrich monazite, and its geochemical characteristics are completely different from the parent body. Through a comparative analysis of the trace element geochemical characteristics of the edge monazite, it is believed that its origin should be heat liquid metasomatism. It was formed by the metasomatism of gold bearing hydrothermal fluid after magmatic stage and accompanied by the precipitation of gold, and accompanied by gold precipitation. Based on geological characteristics of this area, it is believed that the formation of Laozhaiwan gold deposit is probably related to magmatism.
