-

Abstract

Igneous rocks, a part of a dismembered ophiolitic complex, cropping out in the south of Amlash, are mostly composed of basaltic lavas, doleritic dikes, gabbroic and pyroxenitic intrusions. Clinopyroxenes in these rocks are generally augite and diopside, which belong to calcic pyroxene category. Distribution of Si and Al in clinopyroxene composition demonstrates these minerals are high Al pyroxenes. All Si cations with some Al cations enter into tetrahedral sites and the rest of Al occupies the octahedral sites. The distributions of Al at tetra- and octahedral sites may suggest that the clinopyroxenes crystallized at low pressure in a water bearing magma. The content of Fe+3 in the pyroxene composition is the direct result of higher O2 fugacity in magma chamber. The temperature of magma crystallization is evaluated from clinopyroxene composition between 900-1100?C.

Keywords