Document Type : Original Article
Authors
1
Geology department, Sciences college , University of Sistan and Baluchestan
2
Sistan and Baluchestan mining engineering organization
Abstract
The Taktelar igneous rocks crop out 140 km northwest of Zahedan within the Sistan suture zone. The regional geology is dominated by Eocene flysch deposits intruded by Oligo–Miocene igneous rocks. Following field studies, thin sections were prepared from collected samples, and the chemical compositions of selected samples were determined by XRF and ICP–MS. Petrographic and geochemical investigations indicate that the rocks comprise melanogabbro, gabbro, syenite, diorite, meladiorite, monzonite, monzodiorite, basalt, andesite, trachyte, trachyandesite, and dacite. They predominantly belong to the high-K calc-alkaline to shoshonitic series. Some samples exhibit adakitic-like geochemical characteristics, including high Sr/Y and La/Yb ratios and low Y and Yb contents. Trace- and rare-earth-element patterns, characterized by LILE and LREE enrichment, negative Nb, Ta, and Ti anomalies, and high LREE/HREE ratios, indicate a source in enriched, metasomatized lithospheric mantle. Although these rocks share geochemical similarities with magmas related to active continental margins and subduction, the widespread shoshonitic rocks, Oligocene magmatism, structural evidence, and NW–SE-trending strike-slip fault control favor a post-collisional setting. Following Neotethys closure and collision between the Lut and Afghan blocks, lithospheric thinning and asthenospheric upwelling induced limited partial melting of metasomatized lithospheric mantle. The resulting magmas underwent crystal fractionation, limited magma mixing, and crustal assimilation, forming the shoshonitic and adakitic-like rocks of the Taktelar region.
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