Numerous studies have revealed genetic similarities between Tethyan ophiolites and oceanic "proto-arc" sequences formed above nascent subduction zones. The Semail ophiolite (Oman-U.A.E.) in particular can be viewed as an analogue for this proto-arc crust. Though proto-arc magmatism and the mechanisms of subduction initiation are of great interest, insight is difficult to gain from drilling and limited surface outcrops in marine settings. In contrast, the 3-5 km thick upper-crustal succession of the Semail ophiolite, which is exposed in an oblique cross section, presents an opportunity to assess the architecture and volumes of different volcanic rocks that form during the proto-arc stage. To determine the distribution of the volcanic rocks and to aid exploration for the volcanogenic massive sulfide (VMS) deposits that they host, we have remapped the volcanic units of the Semail ophiolite by integrating new field observations, geochemical analyses, and geophysical interpretations with pre-existing geological maps. By linking the major-element compositions of the volcanic units to rock magnetic properties, we were able to use aeromagnetic data to infer the extension of each outcropping unit below sedimentary cover, resulting in a new map showing 2100 km.sup.2 of upper-crustal bedrock.