NEW BIOSTRATIGRAPHIC DATA AND GEOCHEMICAL DATA FROM THE SABZEVAR OPHIOLITE, NORTH CENTRAL IRAN

The Sabzevar ophiolite is one of the largest ophiolite complexes of Iran located along the northern boundary of the central Iranian microcontinent. The igneous rocks of this complex consist of peridotites (harzburgite, dunite and lherzolite), serpentinite, minor pyroxenite, gabbros, and a volcanic sequence that exhibits a wide range of composition from basalts and basaltic andesites to rhyodacite-dacites, rhyolites and basanites. Sedimentary rocks include a variety of Upper Triassic to Upper Cretaceous marine strata. These include pelagic fossiliferous carbonates that are mixed with the pillow basalt and basaltic andesite as interlayers or exotic blocks ranging in size from 10 to 100 meters. Also present are extensive units of radiolarian chert which are interbedded within the basalts and basaltic andesites. The result from geochemical analyses indicates the presence of at least four different types of extrusive rocks in the Sabzevar ophiolite. The geochemical data clearly identifies some of the extrusive rocks to have formed from three distinct types of basaltic melts; i) the group-1 basaltic rocks, which formed from an initial melt with N-MORB-like (LREE depleted) chemical signatures and are petrogenetically related to the gabbros, ii) group-2 basaltic rocks which have E-MORB chemical signatures, and iii) group-3 basaltic rocks with LREE-enriched signatures and incompatible trace element patterns that suggest an island arc affinity. Pelagic limestone samples from the volcanic member produced a number of identifiable planktonic foraminifera. The most significant of the taxa recovered include Globotruncanita calcarata (Zone 2B; uppermost Campanian) and Globotruncana contusa (Zone 1B, Sub-zone 1B1 to 1A; upper Maastrichtian). The Sabzevar ophiolite contains other volcanic rocks that have non-MORB like geochemical signatures (e.g., within-plate, island arc).