Document Type : Original Article
Authors
1
Department of Mineral Resource and Groundwater, Faculty of Earth Sciences, University of Shahid Beheshti, Tehran, Iran
2
Department of geology, faculty of earth science, shahid beheshti university, tehran, iran
Abstract
In the southernmost part of the Sanandaj–Sirjan Zone, Mesozoic volcanic rocks crop out in the Baghat (north of Hajjiabad) and Dehsard (south of Kerman) areas. These rocks are mainly composed of basalt, andesite, and basaltic andesite, exhibiting porphyritic, trachytic microlitic, and microlitic–glassy textures. The main rock-forming minerals include plagioclase and pyroxene, with hornblende, olivine, and opaque minerals as accessory phases. The basaltic and andesitic rocks of the Baghat and Dehsard areas exhibit a tholeiitic to calc-alkaline affinity.
On primitive mantle-normalized trace element diagrams, the rocks show enrichment in Cs, Ba, Pb, Th, K, and U, coupled with pronounced depletion in high field strength elements (HFSEs) such as Nb, Ti, and Zr, which are characteristic features of subduction-related magmas. Furthermore, chondrite-normalized rare earth element (REE) patterns for the Dehsard basalts and andesites display fractionated patterns with LREE enrichment relative to HREE, whereas the Baghat andesites and basalts exhibit relatively flat REE patterns.
Petrogenetic modeling indicates that the majority of the andesitic and basaltic rocks from Dehsard were generated by 15–20% partial melting of an enriched mantle source with spinel–garnet lherzolite composition, whereas the Baghat rocks were derived from 15–30% partial melting of a relatively less enriched mantle source with a transitional composition from spinel lherzolite to spinel–garnet lherzolite. The formation of these rocks took place in an active continental margin volcanic arc setting, in association with the subduction of the Neotethyan slab. The extensional regime governing this magmatism is attributed to slab rollback
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