Geochemistry of Sang-e-Sayad volcanic rocks In SE Bardsir(Kerman province)

Abstract: Sang-e-Sayad volcanic complex is a part of Dehaj-Sarduieh volcanic belt and located in the South-east of Kerman province. This complex consists of several types of lava flows, intrusive bodies, pyroclastic deposits, volcano-sedimentary rocks and limestones. The lavas contain plagioclase rich olivine basalts, basalts and andesitic basalts. Neumerous intrusive bodies such as granitoids, monzogabbros and diorotes have invaded other lithologies. Pyroclastic rocks contain welded tuff, volcanic breccia and ignimbrites and finally volcano-sedimentary rocks consist of conglomerates, tuffaceous sandstones and siltstones. Olivine basalt lava flows are more primitive than the other lavas, because they have not any evidences for magma mixing, and in their plagioclase phenocrysts, there are not any disequilibrium textures such as sieve or resorption textures or zoning, whereas in basalts and andesitic-basalts plagioclases, there are many evidences that show they have been affected by magma mixing and other magmatic evolutions. The patterns of whole rock chemistry data in variation diagrams reveal a clear differentiation trends from olivine-basalts to basalts and andesitic basalts. These patterns are similar for basic intrusive bodies, and it is probably that volcanic and basic intrusive rocks are co-magmatic. These rocks are belong to calcalkaline series and they are very similar to the volcanic associations of magmatic arcs. The absence of hydrous minerals in these lava flows may be due to high temperature crystallization conditions (1050 c) or low contents of Na2O in theire magmas. The investigation of depositional environments and facies analyses in Sang-e-Sayad compelex reveal that the various lithologies have formed in a continental arc environments. When the eruption cease, volcanic rocks erode and their sediments deposit in deltaic and alluvial environments and discontinuous volcano-sedimentary successions are formed. Sedimentary textures such as cross bedding, lag deposits and lenticular shape of volcano-sedimentary rocks, show that these rocks have been deposited in turbulent alluvial environments.