Petrology and tectono-magmatic setting of Zorrati granitoid, southwest of Birjand (East of Lut block)

• Published in: Pitruluzhī (Online) 2023-06, Vol.14 (2), p.1-30
• Main Authors: Ebadolah Toulabi Nejad, Ahmad Ahamadi Khalaji, Mohammad Ebrahimi, Habib Biabangard, Rasoul Esmaeili
• Format: Article
• Language: per
• Subjects: collision setting zorrati granitoid southwest of birjand lut block; type granitoid collision and post
• ISSN: 2228-5210; 2322-2182
• DOI: 10.22108/ijp.2021.125463.1207

The Zorrati granitoid (ZG) pluton exposed on the eastern edge of the Lut block trending north-south. The Lut block surrounded in the north by the Darone fault, in the south by the Jazmurian fault and in the east and  the  west by Nahbandan and Naiband faults respectively (Naderi Miqan and Akrami, 2006). A number of  investigations have been carried out  by various researchers regarding  how and when the magmatism and volcanism of the Lut Block was initiated among which Eftekharnezhad (1980) can be notable, who predicted the subduction of the oceanic crust towards the west and under the Lut Block based on the volume and time distribution. Saccani et al. (2010) suggested that the subduction of the oceanic crust took place towards the east and under the Afghan block. The closest intrusive bodies to the Zorrati granitoid are the Shah Kouh granitoid, the Deh Salam granitoid, the Chahar Farsakh granitoid, and the Sefidkoh granitoid.Regional GeologyThis dominant rocks of the pluton under study are  biotite tonalite and syenogranite-alkali feldspar granite together with biotite and tourmaline porphyritic granodiorite, and granite. The ZG consisting of igneous and metasediment enclaves as well as felsic veins and dykes. According to several studies including field observations, petrology, and geochemical studies the rock units make up the studied pluton have possibly different origins.Materials and methodsFor lithological and geochemical investigations of the Zorrati granitoid pluton and its tonalitic enclaves, after microscopic studies, 11 fresh samples were selected and sent to the Institute of Geology and Geophysics of the Chinese Academy of Sciences for XRF and ICP-MS analyses.PetrographyThe constituent minerals of the granitoid rocks are quartz, plagioclase, microcline, orthoclase, biotite, muscovite and tourmaline.Whole Rock ChemistryThe Zorrati granitoid (ZG) is a high potassium calc-alkaline, peraluminous, and S-type granitoid. Trace element plots show at least two trends, which probably point to  different origins for the rock units forming this pluton. The studied rocks are Rb, Th, U, K, and Pb enrichment and depleted in Nb, Sr, P, Ti, and Zr, indicative of the crustal origin of the relevant magmas in a collision zone. Tourmaline porphyritic granodiorite and syenogranite-alkali feldspar granite were formed by melting a clay-rich metapelitic protolith with upper crust origin due to muscovite dehydration without the intervention of the mantle in a continent