Geochemical Signature of Au-Cu Mineralization in Soil Profiles of the Wadi Al Jaww Prospect and its Applications for Exploration, Saudi Arabia

Abstract A geochemical soil survey was carried out over the Wadi Al Jaww prospect located in the western part of the Arabian Shield between the Hijaz and Jeddah terranes. The area is approximately 150 km southwest of Maaden's Mahd Ahd Dahab mine and 150 km northeast of Jeddah city, and 200 km south of Madinah city. No historical work was reported at Wadi Al Jaww. The Maaden discovery was made from exploration geochemistry methodologies including silt, soil and rock samples. The gold and copper mineralization are hosted by the Shiwan complex of tonalite to granodiorite composition belonging to Kamil suite. The soil samples were collected from the horizons of a soil profile with a 50 m × 100 m grid spacing over the central part of the prospect and with a 100 m × 200 m spacing over northern and eastern extensions. The analytical results have been statistically examined using descriptive statistics, bivariate correlations, cluster and principal component analysis to determine elemental associations. Threshold values have been calculated through median±2MAD approaches to avoid the influence of outliers and to define subtle anomalies. PC-analysis was performed over CLR-transformed data and revealed associations of elements controlled by hypogene mineralization, the composition of host rocks, and surface processes. The first PC explains 47% of data variation and outlines the association of Au-Te. Gold is the main indicator of mineralization in soil profiles. Gold concentrations reach up to 2.39 ppm, indicating the position of near proximity to mineralization. While gold may be mobile in arid regions where the dissolution of elemental Au occurs by oxic, acidic, chloride-rich waters, the close spatial association of soil anomalies and hypogene gold mineralization indicates limited mobility of gold over the Wadi Al Jaww prospect. Tellurium is highly enriched in soils over mineralized zones but shows less consistent anomalies. The absorption of tellurium in soils could be associated with Fe (hydr) oxides and clay minerals. Copper is believed to be highly mobile in arid environments and usually incorporated into Fe-, Mn oxides and hydroxides. The composition of soil profiles and the arid environment at Wadi Al Jaww area explains the distribution of metals in soils. The soil geochemistry survey was the main contributor for discovery of Wadi Al Jaww Au-Cu mineralization and outlined association of elements could be used as a guide for future discoveries of similar types of mineralization associated with intrusive complexes along suture zones of Arabian Shield.