In October 2008, Tim Barrett visited Oman, courtesy of the National Mining Company, to examine several VMS deposits hosted by mafic volcanic rocks of the famous Semail Ophiolite Compex, a large and well preserved segment of Cretaceous ocean crust that outcrops for several hundred kilometres along much of the length of the country. The main past-producing deposits, which were mined for Cu, include the Lesail, Bayda and Aarja deposits, and the more recently discovered Hatta, Shinas and Ghuzayn deposits. The Lesail deposit, at about 10 Mt, was the largest. The Bayda deposit is also the site of the first described fossilized worm tubes, which indicate that the sulfides were formed at black smoker sites (Hayman et al., 1984).

The previously mined massive sulfide deposits in the ophiolite complex appear to occur at or close to the contact between two major volcanic sequences known as the Geotimes and Lesail units (Alabaster, 1985). However, this has not been demonstrated as yet in the areas of recent discoveries. A program of sampling of the stratigraphy around the latter deposits therefore has been initiated in order to define the chemostratigraphic sequence in detail, in particular the main paleo-surface of ore deposition. This framework will be applied to both outcrop mapping and new drilling in order to identify and follow the main contacts of exploration interest.

Semail Ophiolite Complex. Extrusives in foreground, mantle sequence in background.

Geotimes basalt unit. This unit forms the footwall to the Lesail deposit.

Aarja open-pit deposit, now mined out.

Cu-rich massive sulfides (clastic). Hattas deposit.

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