Abstract:

This article focuses on the structures and geochemistry of veins that are typically cross-curring the Dahongshan copper and
iron ore deposits. Systematic sampling was conducted and the REE geochemistry of samples was analyzed. The results show that
(1) the mine in the region of various types of rock (ore) shows a decreasing trend in REE amount from mineralized tectonite, to ore, to
non-mineralized tectonite, which reflects differences in the degree of water-rock interactions between ore-forming fluids and rocks;
(2) the (La/Yb)N shows that LREE of similar tectonite in the mine displays large degree of fractionation, but different tectonites show
relatively uniform differentiation. LREE / HREE and (La/Yb)N ratio characteristics of the surrounding rocks, ore and tectonites indicate
that there is similarity in the degree of fractionation between LREE and HREE, suggesting that the REE of the ore-forming fluids is
inherited in certain rocks; (3) LREE / HREE (5.66~13.27) shows a gradual increase from formation of rock, tonon- mineralized
tectonite, to mineralized tectonite, to blocky and stripped ores, reflecting REE migration in the process of fracturing; The δEu of various

types of rock (ore) is greater than 1 and δCe shows a weak negative anomaly, suggesting that Dahongshan copper and iron ore
mineralization took place in a relatively oxidizing environment.

Key words: REE, geochemistry, copper and iron deposits, Yunnan