Geophysical surveying over VMS deposits in Oman

Abstract

Airborne and ground geophysical information was acquired to help locate prospective ground and to directly detect Cyprus-type Volcanogenic Massive Sulphides in the Northern Oman Ophiolite terrane. Airborne magnetic low zones were identified as areas of interest for ground geophysical surveying since footwall alteration, including magnetite destruction, is associated with the generation of these copper-rich VMS deposits. The Hatta and Shinas gossans and surrounding prospective volcanic rocks were surveyed with Time Domain Gradient Array Induced Polarisation, 100 m single moving loop SiroTEM and ground magnetic data. The 2 Mt Shinas deposit hidden beneath 20 m of resistive gravel cover, exhibits a weak Ch5 TEM anomaly related to copper-rich pyritic massive sulphide and an associated discrete IP anomaly coincident with the underlying stringer mineralisation. These are down-faulted from the outcropping auriferous debris flow breccia gossan. At a lower stratigraphic position in the nearby Hatta area, SiroTEM and Gradient Array IP anomalies have outlined four smaller massive sulphide breccia deposits that host economic copper grades. These deposits are associated with a major hydrothermal upflow zone in the footwall basalts that is characterised by magnetite depletion and weak chargeability. A combined approach of airborne geophysics, Landsat, geochemistry and geological mapping identified prospective areas for the utilisation of ground geophysics, which provided valuable guidance to site discovery drillholes.