Geochemical characteristics and Cr metallogenic potential evaluation of the middle section of the northern margin of the Qaidam Basin

This study extracted 59238 pieces of original data on different scales (1:50000 stream sediment surveys and 1:25000 geochemical surveys) of the middle section of the northern margin of the Qaidam Basin. Based on these data, this study conducted the superposition analysis of mathematical index statistics and multivariate statistics, aiming to discover the element association relationship and determine the major metallogenic elements in the region and provide basic support for subsequent mineral work. According to the statistics, the mathematical indexes of Au, W, and Cr in the study area show great metallogenic potential. Combined with the multivariate statistical analysis and existent metallogenic facts, the authors of this study believed that the study area has the great potential for the prospecting of chromium deposits associated with ultramafic rocks besides tectonic altered rock-type and hydrothermal gold deposits. Owing to the relatively high overall background value of local chromium (Cr) element, the traditional method using X+2σ (129×10-6) or the cumulative frequency 85% (142.9×10-6) used to delineate the anomaly threshold cannot meet the requirement for delineating local anomalies in the study area. Therefore, this study improved the anomaly threshold using the 1/4 concentration grading value (234×10-6). As a result, many anomalies exhibiting significant zonal distribution in the concentration center were delineated, and most weak anomalies were eliminated. Based on the geological, geophysical, and geochemical results, this study inferred zones favorable for the further exploration of chromium deposits and determined four favorable metallogenic zones and five prospecting areas.