A study of primary halo anomaly structure of the Lannitang porphyry copper deposit in northwest Yunnan, China

The Lannitang deposit in Shangri-La county, Yunan Province, is a typical porphyry copper deposit. The main orebodies are distributed 300~500 meters below the surface and the vein-type orebodies develop in the surface. In order to decipher the primary halo anomaly structure, based on the theory and method of anomaly structure, the element association, anomaly characteristics and horizontal zonation of surface of tunnel rocks and ore samples of the deposit are conducted.Research results show that the structure of the geochemical system of the Lannitang copper deposit consists of a primary halo of enriched and depleted ore-forming elements and their associated elements. The positive anomalies of Cu and Mo occupy the ore primary haloes, and the negative anomalies of Sc, Ti, V, Cr and W coincide with the positive anomalies of Cu and Mo. Positive anomalies of S, and negative anomalies of Mn, Co, Zn and Cd appear at the edge of positive anomalies of Cu and Mo. The positive anomalies of Zn, Cd, Ag, Pb, Hg, and Sb appear in the periphery of the metallogenic belt. Ag, Pb, Hg, and Sb belong to distal indicator elements or supra ore halo elements. The contents of CaO, K₂O and Na₂O of the samples in the copper mineralization zone are relatively low, which belong to low background or negative anomaly, while the peripheral area belong to middle background area or high background area.It is suggest that the ratio of the geometric mean of Cu and Mo to the geometric mean of Sc, Ti, V and Cr can be used as a marker to delineate the contrast geochemical anomaly, which can better define the spatial location of copper mineralization bodies.