Petrographic and geochemical study of the granitoid intrusions north of Ahar (south of Kaleybar) with emphasis on the role of the tetrad effect in the rare earth element patterns

Authors

1 Department of Earth Sciences, Faculty of Natural Sciences, University of Tabriz, Tabriz, Iran.

2 Department of Earth Sciences, Faculty of Natural Sciences, University of Tabriz, Tabriz,, Iran.

3 Department of Geology, Bu-Ali Sina university

Abstract

The granitoid intrusions in northern Ahar is located in the south of Kaleibar city, NW Iran. The granitoids are essentially composed of granite, quartz-monzonite, microdiorite, monzonite, monzodiorite, and porphyry granodiorite with granular, pegmatite, graphitic and perthitic textures. The I-type granitoids are shown by meta-aluminous nature and have a range of sub-alkaline to alkaline rocks. The main minerals of these rocks include quartz, alkali feldspar, plagioclase, muscovite, and biotite, and minor minerals composed of titanite, zircon (allanite, apatite, and pyrochlore). The Ahar granitoids chondrite normalized REE pattern shows an M-type tetrad effect pattern with a strongly negative Eu anomaly. This M-type tetrad effect indicate the final stages of granite magma evolution accompanied by interactions with coexisting fluids. The Y/Ho and Zr/Hf ratios in the basic to intermediate igneous rocks are close to the chondrite ratios, which indicates the CHARAC behavior of these elements in the melts. The La/Nb and La/Ta ratios show an inverse relationship with the tetrad effect. With increasing fractionation, the Rb/Sr ratio in the rocks increased, and as a result, the tetrad effect of the granitoid samples of north Ahar occurred in a higher range of Rb/Sr ratio. The study of the trace element ratios, especially geochemical pairs, indicates the non-CHARAC behavior of these elements.

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History

  • Receive Date: 07 November 2024
  • Revise Date: 01 June 2025
  • Accept Date: 07 June 2025

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