| Abstract:The Naruo large-scale porphyry copper (gold) deposit is one of the important deposit in the Duolong Ore district, Tibet. Previous studies have been made on the diagenetic and metallogenic age, source and ore-forming materials, genetic mechanism, dynamic background and preservation conditions, but there is a lack of geochemical characteristics of the ore-bearing magma evolution process. Therefore, in this paper, LA-ICP-MS method is used to analyze the trace element composition of zircon and apatite in the ore-bearing rocks of Naruo deposit to study the characteristics of magma crystallization differentiation process, oxygen fugacity and water content, so as to explore the evolution characteristics of ore-bearing magmas in the Naruo deposit and its implications for mineralization. Zircons in the ore-bearing rocks of Naruo deposit are characterized by strong positive Ce and negative-medium Eu anomalies, and apatite has strong negative Eu anomalies. The characteristics of zircon and apatite trace elements show that the magma was formed in the continental arc environment and belongs to type I granitic rock. The Th/U, Ce/Sm and Yb/Gd characteristics of zircon showed that the co-crystallization of apatite and titanite affected the zircon from high temperature to low temperature. The ore-bearing magma of the Naruo deposit exhibits higher water content and oxygen fugacity, and the ore-bearing magmas have undergone a higher degree of evolution than the ore-barren magmas. The high oxygen fugacity of ore-bearing magmas may be caused by SO2 degassing of sulfur-rich magmas and re-emplacement/mixing of magmas. Zircon Dy/Yb<0.2, 10 000*(Eu/Eu*)/Y>7, and Ce4+/Ce3+>200 can effectively distinguish ore-bearing and ore-barren rocks in the ore district. The research results of this paper show that the trace element characteristics of zircon and apatite can effectively indicate the source area characteristics, crystallization history, and ore-forming potential of igneous rocks. |
