Element behavior analysis and its implications for geochemical anomaly identification: A case study for porphyry Cu–Mo deposits in Eastern Tianshan, China

Abstract Geochemical anomaly identification in areas with overburden is a challenging task because primary geochemical anomaly signals from buried mineralization could be masked by cover layers, and could also be overprinted by various pseudo-geochemical anomalies formed by mobile elements. In this study, porphyry Cu–Mo deposits in the Gobi desert, a covered geographical landscape of Eastern Tianshan, China, are taken as an example to illustrate delineation of significant geochemical anomalies in covered area. Firstly, element behavior was analyzed by means of accumulation coefficient (AC) analysis for investigating possible mobility of elements to assist in determining a set of suitable indicator elements including Cu, Mo, Pb and Zn for porphyry Cu–Mo mineralization. Next, the singularity mapping technique was employed to recognize weak geochemical anomaly signals of the indicator elements. Finally, single element geochemical anomalies were normalized and combined to derive a comprehensive geochemical anomaly, and Student's t -statistic was used to quantitatively estimate the spatial relationship between the integrated geochemical anomaly and known porphyry Cu–Mo deposits for classifying and grading the anomaly in order to delineate potential porphyry Cu–Mo prospects for future exploration in the study area. It is concluded that: (1) AC analysis is an easy and efficient method to characterize enrichment or depletion of elements in different geological units for determining probable mobility of elements; (2) there exists a strong genetic relationship of geochemical composition between bedrock and Gobi desert cover in the Eastern Tianshan region; (3) it is important to analyze element behavior for identifying principal geochemical anomalies in overburden as found in the Gobi desert; (4) singularity mapping is a proper method to delineate weak geochemical anomalies in overburden; and (5) there is probably a high potential to discover buried porphyry Cu–Mo deposits beneath identified anomalies with or without associated known porphyry Cu–Mo deposits.