Trace elements and REE geochemistry of copper-bearing sandstone in the Middle Submember of the Liuju Member of the Upper Cretaceous Matoushan Formation, Dayao County, Yunnan Province, China.

The Middle Submember of the Liuju Member in the Upper Cretaceous Matoushan Formation is one of the copper-bearing horizons in the Liuju sandstone copper district. The sulphophile elements such as Mo, Cd, As and Cu are enriched in the sandstone. Trace elements are enriched in gray sandstone and depleted in purple sandstone. In the copper ore, value of V/(V+Ni) is over 0.7, which indicates that it is formed in oxygen-poor environment. The ∑REE of rocks ranges from 101.71×10-6 to 157.55×10-6. Chondrite-normalized REE distribution patterns show oblique to the HREE side with the poor Eu, Ce and enrichment in LREE. From the copper ore to gray sandstone, and then to purple sandstone, the average values of Mo, Cd, As and Hg reduced gradually, and Nb, Zr, Hf,Th and ∑REE increased gradually. It indicates that the copper ore and wall rock have the similar provenance. The copper ore formed by water-rock interaction of wall rock with weak alkaline and reducing property condition. The metallogenic mechanism is similar to that in the Liuju copper deposit. From north to south in Xiaohe ore block, the weakening mineralization ability of Cu, and the ore belt deflect to west part (purple sandstone).