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Origin of mafic enclaves in the Alvand Mountains (Hamedan): evidence from petrographic and geochemical data | ||
| یافتههای نوین زمینشناسی کاربردی | ||
| Articles in Press, Accepted Manuscript, Available Online from 23 June 2025 | ||
| DOI: 10.22084/nfag.2025.31075.1677 | ||
| Authors | ||
| P. Vermazyar; A. Torkian* ; L. Izadi Kian | ||
| Abstract | ||
| The Alvand Mountains is one of the largest batholith masses in the middle part of the Sanandaj-Sirjan zone. This study investigates the origin of mafic enclaves in syn-plutonic dykes in this area. Based on field relationships and petrographic observations, the Alvand batholith is composed of mafic –felsic rocks (gabbro, olivine gabbro, tonalite, quartz diorite, quartz monzodiorite, monzogranite, syen-ogranite and granite) and mafic enclaves and syn-plutonic dykes. enclaves are fine-grained and more mafic than host rock. They are mafic microgranular enclaves (MMEs) and have composition of granodioritic to dioritic rocks. MMEs are mostly elongated ellipsoids, with coarse crystals, clear boundaries with the granitoid host, and aligned with the flow direction of felsic magma. The hosts are granitic in composition. Geochemical data display enclaves are metaaluminous and the hosts are peraluminous, and both are the calc-alkaline in nature. Geochemical results in spider- normalized diagrams indicate enclaves and their hosts are enriched in LILEs and depleted in HFSEs. In the rare earth element-normalized patterns, they show enrichment in LREEs and depletion in HREEs and enrichment in LREEs is more pronounced in hosts. This feature is one of the prominent characteristics of the calc-alkaline magmas in a volcanic arc environment. In discrimination tectonic setting diagrams, enclaves and hosts are plotted on the VAG field. Based on petrographic and geochemical studies, the microgranular mafic enclaves formed in a magmatic mixing/mingling process due to the absence of sedimentary fabrics and cumulative textures, along with different grain size characteristics. | ||
| Keywords | ||
| Enclave; Alvand; Sanandaj-Sirjan; magmatic mixing | ||
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