Geochemistry and mineral chemistry of Shahabad gabbroic intrusion, NW Nourabad, Lorestan province

زمین شناسی اقتصادی

Article 5, Volume 5, Issue 2 - Serial Number 9, January 2014, Pages 291-305   

Document Type: Research Article

DOI: 10.22067/econg.v5i2.31986

Authors

Reza Zarei Sahamieh^{* 1}; Amir Ali Tabbakh Shabani²; Seyed Vahid Shahrokhi³; Nasrin Barak³

¹Lorestan

²Kharazmi

³Islamic Azad University

Abstract

The Shahabad gabbroic intrusion, with NW-SE trend cropped out at the boundary of Zagros and Sanandaj-Sirjan zones is composed of olivine gabbro, orthogabbro and troctolite. Plagioclase, clinopyroxene and olivine are the main minerals; and magnetite, titanomagnetite and serpentine are minor and secondary minerals. Microprobe analyses of the minerals show that plagioclase is labradorite, pyroxene diopsidic augite and olivine, chrysolite. The rocks appear to have calc-alkaline and metaluminous nature. The plots of some trace elements and composition of clinopyroxenes in the tectonic discrimination diagrams indicate a volcanic arc environment. In addition, spider diagram pattern of elements shows Sr enrichment and Ti, Nb, Zr and P depletion, typical characteristics of volcanic arc subduction related magmas. Furthermore, close similarity between the patterns of spider diagram for the Shahabad pluton with those of Andean basic rocks suggests that the Shahabad calc-alkaline basic magma may have formed in a subduction environment. Based on geological, geochemical and mineralogical features, formation of the gabbros, as a part of ophiolite mélange, is attributed to a suprasubduction system.

Keywords

Gabbro; Clinopyroxene; Olivine; Plagioclase; Sanandaj–Sirjan zone; Shahabad; Lorestan

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