Element geochemical division of the middle segment of the Sanjiang (Three-River) region

This paper describes the aim and principle of element geochemical division, the source of samples and data processing, the choice of divisional indices and the division of index value ranges. According to the geological structures and characteristic values (the accumulated value of enrichment coefficient) of the mantle-type elements (K T) this region can be divided into seven geochemical zones, i.e., the Yangtze basement, the Yangtze cover, the Jinshajiang paleo-Tethys, the Lancangjiang paleo-Tethys, the Lanping Mesozoic basin, the Indosinian granite, and the Himalayan granite. Again in accordance with the different characteristic values of high field strength elements (HFSE) (K Nb) or radiogenic elements (K Th) 16 geochemical sub-zones can be divided. Meanwhile, this paper also discusses the rules of variation in characteristic value of the various sub-zones and points out the characteristics of enrichment of oreforming elements in some of the sub-zones.