Models of Spatial Structures of Regional Multi-element Geochemical Anomalies over Copper-Polymetallic Orefields

摘要

Regional stream sediment surveys at a 1:200,000 scale reveal positive and negative regional multi-element geochemical anomalies over medium to large copper-polymetallic orefields of different genetic types in China. Regional geochemical anomalies of orefield refer to those geochemical anomalies that are related to metallogenesis of an orefield in a certain area. The anomaly area is typically 10 to 100km~2. The regional multi-element anomalies related to mineralization can be divided into three groups, that is, the ore-element anomaly association, indicator element anomaly association, and metallogenic environmental element anomaly association. Their common spatial distributions over ore deposits or orefields possess unique structures. The model of spatial structure of regional multi-element geochemical anomalies (RAGSS) of an orefield delineates structural feature possessed by orderly spatial distributions of different groups of multi-element anomaly associations related to orefield metallogenesis. It is used to outline the common metallogenetic anomaly visage that is composed of the orderly spatial distribution of different groups of multi-element anomaly associations. The orderly spatial distribution of multi-element anomalies over an orefield reflects element distributions as they are changed from a dispersed "out-of-order" state into a concentrated "orderly" state during the mineralization of an orefield. Three different patterns of the spatial anomaly structure related to mineralization in an orefield can be concluded: (1) nested pattern; (2) eccentric pattern and; (3) peripheral pattern. There are marked differences between multi-element anomaly patterns related and not related to mineralization. RAGSS models of orefields can be used to better understand and evaluate regional multi-element anomalies and identify ore types.