Abstract:

Geochemical gene is a new technique to classify and trace geological materials. The current research focuses on testing the gene steady properties and traceability of soils from the weathering of magmatic and (minor) carbonate rocks. Two weathering profiles developed on dolomite in the Shangmanggang gold deposit at Luxi (Yunnan Province, SW China) were investigated for the steady properties of geochemical genes, including lithogenes (LG01 and LG03), metallogene (MGAu and MGW), and REE (rare earth element) genes (REEG01 and REEG02). The geochemical results indicate that the dolomite was totally leached during the pedogenetic stage, followed by the soil evolution stage. Chemical weathering indices of CIA (chemical index of alteration) and WIG (weathering index of granite) were used to quantify the degrees of weathering, however the CIA may indicate the weathering degrees of the provenance sediments of dolomite. Therefore, WIG is better than CIA to determine the weathering degrees of carbonate rocks. Based on the results of heredities and inheritances of geochemical genes on weathering products, the parent rocks may have been geochemically homogeneous. The dolomite and its weathering products are classified as the intermediate-like compositions on felsic similarities of lithogenes, as anomalous gold-mineralized samples on mineralization similarities of gold metallogene, similar to the upper continental crust on REE genes. Although the anomaly materials classified on mineralization similarities of gold metallogene are not necessarily gold ores, they have likely the potential to offer ore-forming materials. The mineralization similarity of gold metallogene can be used to determine whether a weathering-type deposit was formed on the parent rock, which offers new insight or technique on tracing the provenance of ore-forming materials.

Key words: dolomite, weathering, geochemical gene, Shangmanggang gold deposit, mineralization similarity of metallogene