Geophysical Hunt for Chromite in Ophiolite

Ophiolite of Oman are famous world over, and are favorite for exploring chromite, which is a source of chromium that is used widely in steel, nichrome, and plating and painting industries. The best known chromite deposits are found in the Bushveld complex of South africa, however countries like Pakistan and Oman are also contributing but less than 2% of the world production. Chromite is found in the mantle rocks such as peridotite and its altered products. Large economic deposits are generally found in stratiform structure and the smaller ones in pod-like or tabular lenses. In Oman the chromite deposits occur in Oman ophiolite (Semile), mainly in the mantle sequence comprising harzburgite and dunite. The mining efforts for chromite in Oman are in progress but not on scientific grounds. On a site called Izki (670 m asl) the chromite was expected on the top of a hill in a small area (150x50 m) of ophiolite, and mining through pitting procedure was tried over there but remained unsuccessful. Geophysical methods were applied in the same area to search out the possibility of the existence of the ore. Since chromite is denser, more conductive and magnetically less susceptible deposit as compared to the host rocks harzburgite and serpentinite, it is expected that the existence of a shallow sizable ore body would generate favorable gravity, magnetic, and resistivity signals. The integrated geophysical study (gravity, magnetic and resistivity) reveals the probability of chromite within 30 m depth. For confirmation the drilling was recommended on a point upto a depth of 35 meters. The drilling could not be continued beyond 12 meters depth due to reasons known to the lease owner. The drilling showed harzburgite up to 8 meters depth, then a chromite layer of 0.7 meter thickness, after that harzburgite started for the next 3 meters depth. This state of affairs confirms not only the presence of chromite but also the revealing power of geophysics.