Separation of the Mahabad young basalts, trachytes and trachy-andesites, geochemical and tectono-magmatic setting aspects; necessity of the Mahabad 1:100000 sheet reform

• Published in: Pitruluzhī (Online) 2019-06, Vol.10 (1), p.97-124
• Main Authors: Monir Modjarrad, Yosef Rahim Souri
• Format: Article
• Language: per
• Subjects: adakite; geochemistry; high niobium basalt; mahabad; trachy-andesite; trachyte
• ISSN: 2228-5210; 2322-2182
• DOI: 10.22108/ijp.2019.114728.1115

In the Mahabad region accompaniment of trachytes and trachy-andesites with OIB-like alkali-basalts are shown. Trachytes at the Soltan Mountain heights, trachy-andesites as darker enclaves in it and alkali-basalts in the three sites, Khatton Bagh, Bardarashan and Badam are outcropped. Alkali-basalts have shoshonitic, met-aluminous and OIB-like characteristics with LREE/HREE enrichment and generate at deep garnet peridotitic source. Trachytes and its intermediate trachy-andesite enclaves at the Sltan Mountain with shoshonitic, per-aluminous affinity have high LREE/HREE ratios with HFSE and Ti depletion and continental arc relevant signatures. The Soltan Mountain trachytes have adakitic nature which accompany with the High niobium basaltic (HNB) affinity of Badam, Barderashan and Khatoon Bagh basalts of Mahabad and their similarities to Ghorveh HNB could clarify the relationship between adakites and basalts along the Neo-Tethys post collisional activities. Computer modelling clarify the fractional crystallization opportunity for the intermediate to acidic terms production from mantle basaltic liquid. In addition, very high contents of incompatible elements in the most evolved rocks suggest the occurrence of open-system magmatic processes. Continuous fractional crystallization from a primitive basaltic source, similar to post-plateau coeval basalts, towards acidic terms combined with small rates of assimilation (AFC) in a shallow magmatic reservoir, is best explains for the young volcanic association in the Mahabad. These phenomena are occurred after Neo-Tethys closure at the Quaternary.