Characteristics of element migration in the process of wall-rock alteration in the Shibangou gold deposit, western Henan

The Shibangou gold deposit in western Henan is associated with irregular qu artz veinlets occurring in altered shear zones dissecting a dioritic intrus ion. The altered shear zones are characterized by silicification, pyritizat ion, sericitization, chloritization and K-feldspar alteration. Zoning of al tered rocks adjacent to the Au-bearing quartz veins is obviously exhibited. Fine-grained sulphides and quartz veinlets of different ages and small-sca le fissures are widely distributed in the central part of the altered zones . Major mineralization types in this gold deposit are An-bearing quartz vei nlets and altered rocks in the shear zones. Samples were collected from dri lling cores according to the alteration zoning and mineralization type and all samples were analyzed for major and trace elements. Mass balance, volum e change (f(nu)=97.3-71.9%) and major element variation sequences are studi ed in terms of major elements. The changes of mobile components (SiO2, K2O, Fe2O3 and CaO) and immobile component (Al2O3) in the wall-rock alteration are discussed. The gold mineralization is associated with the enrichment of As, Ag, Hg and Pb and depletion of Cu and Zn. The study of compositional v ariation of altered rocks proves to be a very efficient method for defining the extent of wall-rock alteration, fluid activity and mineralization and enrichment.