Assessing the potential of two typical layered complexes from the Arabian Shield for hosting Ni-Cu mineralization through stream sediment geochemistry

Two late Proterozoic (< 630 Ma) mafic layered complexes (Al-Jilani and Shai) from the central and southern Arabian Shield were chosen for a preliminary rock and stream sediment survey to test their potential for hosting Ni–Cu sulfide mineralization. The choice was made on the basis of the highly differentiated and exceptionally well-layered nature of these intrusives, with the ultimate aim of drawing inferences on the mineralization potential of other mafic bodies of the same age and setting. The results showed a marked depletion of the target elements and their pathfinders (Ni, Cu, Co, Cr, and PGE), except for a single anomalous location at Shai which appears to lithologically induced rather than representing a true sulfide signature. The two major problems in the stream sediment results were the masking effect from the host lithologies and the dilution by felsic detritus. Applying factor analysis to the data set failed to yield an “ore factor” that excludes mafic lithophile elements, but revealed the important role of the Fe–Mn oxyhydroxides in adsorbing certain metal cations even in the arid climate of the Arabian Shield, thus opening up the possibility of future work utilizing partial leach techniques in this part of the world. Overall, the two complexes do not seem to satisfy the necessary requirements for Ni–Cu sulfide enrichment in that there is a general lack of an external source of sulfur, in addition to the absence of a concentration mechanism for any produced sulfides.