Geochemistry, petrogenesis and petrology of intrusive rocks in Shadan gold deposit, SW Birjand, Eastern Iran

Document Type : Research Paper

Authors

School of Geology, College of Science, University of Tehran, Tehran, Iran.

10.22059/geope.2022.347096.648668

Abstract

Shadan gold (+ copper) deposit in the Lut block, east of Iran comprises Eocene to Oligocene intrusive and sub-intrusive rocks with intermediate to felsic composition, which have intruded Eocene volcanics- pyroclastics. Shadan intrusive rocks range from granodiorite, quartz monzonite, and diorite to microgabbrodiorite. Geochemical data indicate that Shadan intrusive rocks are I-type, metaluminous to peraluminous, belonging to the calc-alkaline to high-potassic calc-alkaline magmatic series. REE patterns of Shadan rocks display enrichment in light rare earth elements (LREE) and large ion lithophile elements (LILE) relative to heavy rare earth elements (HREE) and high field strength elements (HFSE). These characterize the formation of Shadan rocks in a subduction zone setting. The main hydrothermal alteration types contain quartz-carbonate, propylitic, argillic, phyllic and potassic which affected the rocks in varying degrees. Variation of major oxides versus SiO2 can be related to assimilation-fractionational crystallization (AFC) in parent magma. According to tectonomagmatic discrimination diagrams, all rock samples display evidence of a volcanic arc which was formed at an active continental margin. Based on Nb/Y vs. Rb/Y ratio, Shadan rock samples experienced subduction zone enrichment and crustal contamination. Ba/Rb vs. Rb implies the role of AFC processes in the upper continental crust. According to Nb/Zr vs. Nb/Ba ratio, source region of the Shadan intrusive rocks are attributed to the sub-continental lithosphere. Th/Yb vs. Nb/Yb ratio suggests an E-MORB like mantle source. La vs. La/Yb ratio reveals that partial melting played a significant role in the formation of Shadan rocks.

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Article Title [Persian]

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Articles in Press, Accepted Manuscript
Available Online from 24 October 2022
  • Receive Date: 13 August 2022
  • Revise Date: 19 October 2022
  • Accept Date: 24 October 2022
  • First Publish Date: 24 October 2022