Geochemistry of the Zargoli granite: Implications for development of the Sistan Suture Zone, southeastern Iran

Abstract

AbstractThe Zargoli granite, which extends in a northeast–southwest direction, intrudes into the Eocene–Oligocene regional metamorphic flysch‐type sediments in the northwest of Zahedan. This pluton, based on modal and geochemical classification, is composed of biotite granite and biotite granodiorite, was contaminated by country rocks during its emplacement, and is slightly changed to more aluminous. The SiO2 content of these rocks range from 62.4 to 66 wt% with an alumina saturation index of Shand [molar Al2O3/(CaO + Na2O + K2O)] ∼ 1.1. Most of its chemical variations could be explained by fractionation or heterogeneous distribution of biotite. The features of the rocks resemble those which are typical to post‐collisional granitoids. Chondrite‐normalized rare‐earth element patterns of these rocks are fractionated at (La/Lu)N = 2.25–11.82 with a pronounced negative Eu anomaly (Eu/Eu* = 3.25–5.26). Zircon saturation thermometry provides a good estimation of magma temperatures (767.4–789.3°C) for zircon crystallization. These characteristics together with the moderate Mg# [100Mg/(Mg + Fe)] values (44–55), Fe + Mg + Ti (millications) = 130–175, and Al–(Na + K + 2Ca) (millications) = 5–50 may suggest that these rocks have been derived from the dehydration partial melting of quartz–feldspathic meta‐igneous lower crust.