Abstract

The Waziristan complex, covering over 500 km 2 , was tectonically emplaced during the Paleocene to early Eocene. It consists of ultramafic rocks, gabbros, sheeted dikes, pillow lavas, and pelagic sediments--a typical ophiolite suite. However, a complete sequence does not occur in any single locality due to tectonic dismemberment. The podiform chromitites consist of aluminochromite (Cr 2 O 3 :49-61%) with subordinate chromian chlorite and/or chromian serpentine + magnetite. In Cr-Al-Fe (super +3) + Ti space the chromites plot in the area of alpine chromites, but on other diagrams they overlap the fields of chromites from alpine and stratiform complexes. Many chromites are zoned with "ferrit-chromit" margins richer in Cr/(Cr + Al) and poorer in Mg/(Mg + Fe (super +2) ) than the unaltered cores. The chlorites are generally rich in SiO 2 and MgO and poor in Al 2 O 3 . It appears that during greenschist facies metamorphism (or alteration) diffusion of Mg, Al, and some Cr from the chromite margins toward the silicate matrix resulted in the development of ferrit-chromit and chlorite.

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