Geochemical Characteristics and Tectonic Setting of Epidote Rocks in the Hongshiyan Pb-Zn-Cu Polymetallic Ore Deposit , Southeastern Yunnan Province

The Hongshiyan orefield in southeastern Yunnan Province lies in the intersection between the NW-striking Wenshan-Malipo fault and the NS-striking Maguan strike-slip fault. The regional metamorphism and major deep faults exert a critical control on the well-developed epidote rocks. This paper studies the major, trace and rare earth elements of the epidote rocks from the Hongshiyan Pb-Zn-Cu polymetallic ore deposit. The results show that: ① The average composition of the major elements is similar to the volcanic arc basalts, and the FeO*, MnO, and CaO are high, Al2O3 and TiO2 are low. ② Massive meta-basalt is rich in LILE (Rb, Ba,Th), whereas Ta,Nb,Y are depleted, (Rb/Yb)N (31.72 on average), similar to volcanic arc basalts; primitive mantle-normalized diagram shows an uplift pattern. It is enriched in LFSE, relatively depleted in HFSE, similar to back-arc basin basalt. ③ REE: ΣREE ratios are relatively low (averagely 110.05×10-6). It is enriched in LREE(LREE/HREE is 8.34 on average; (La/Yb)N7), rare earth fractionation is relatively obvious((La/Sm)N is 4.04 on average; ∑Ce/∑Y3). ④ The discrimination diagram of environment structure suggests that the original rock of epidote rocks of the study area is back-arc basin tholeiite.