Geochemistry and tectonic setting of volcanic rocks in the Mahiroud volcano-plutonic complex, Southeast of Sarbisheh (Eastern Iran)

• Published in: Pitruluzhī (Online) 2024-06, Vol.15 (2), p.129-152
• Main Authors: Sahar Benrashidiyan, Ahmad Ahmadi Khalaji, Peyman Eskandarnia, Shahriar Keshtgar, Zahra Tahmasbi
• Format: Article
• Language: per
• Subjects: eastern iran; island arc; mahiroud; sistan suture zone; subalkali basalt
• ISSN: 2228-5210; 2322-2182
• DOI: 10.22108/ijp.2023.137324.1297

Introduction Mahiroud volcano-plutonic complex as an anticline (Lahnu-Mahiroud) forms a part of the Sistan suture zone (SiSuZ), and lies in the northern part of the Sistan suture zone (SiSuZ). According to Tirrul et al. (1983), the Mahiroud complex, which includes a series of metamorphosed intrusive and extrusive rocks, is related to the rifting of the ocean, and they also believe that the general nature of this complex is ophiolitic, but because layered gabbros and ultramafic rocks do not outcrop, this issue is not certain. Delavari et al. (2017) by studying the volcanic rocks of southern Gazik in the vicinity of the Mahiroud volcano-plutonic complex, believe these rocks belong to the magmatism of the island arc. Also, Keshtgar et al. (2019) studied the tonalitic stock of the Mahiroud volcano-plutonic complex and attributed these rocks to the environment above the subduction zones, especially the present-day island arc (IAT). The main purpose of the present study is to study and to determine the tectonomagmatism of the volcanic rocks of the Mahiroud volcano-plutonic complex.  Regional Geology The oldest rocks of the studied area related to the ophiolitic and ultrabasic rocks of the Lower Cretaceous, and after that, the volcano-plutonic rocks of Mahiroud along with sandstone, limestone and shales of the Upper Cretaceous were exposed. The sequences of flysch sediments from Paleocene to Pliocene exist in this area, so that the Oligo-Miocene magmatism can also be seen in it. The largest outcrop of the Mahiroud complex is located in the southern part of this belt and consisting of two parts: (1) The western part, which mainly includes pillow lava, andesite, tuff, and conglomerate. (2) The eastern part, including a complex of sheeted dykes and diabase trending approximately north - south. Analytical Methods 50 samples of the rocks under study with the least amount of weathering and alteration were collected from which, 20 thin sections were prepared for microscopic studies. Among these samples, 11 samples were selected for ICP-MS geochemical analysis for minor elements and AF-01-Lithium Fusion for major elements at the Zarazma Laboratory in Tehran. GCDkit, Excel and Corel Draw software were used to check the chemical results. Petrography The rocks of the studied area include volcanic rocks ranging from andesite- basalt, basalt and diabase, crosscutting by a tonalitic stock of Upper Cretaceous (Keshtgar et al., 2019). The boundary between the sedimentary-volcani