Petrology and petrogenesis of a tuff layer in the Upper Red Formation, north of Tabriz (NW Iran): shoshonitic magmatism with high Ba and Sr affinity

Document Type : Original Article

Authors

1 Assistant professor of petrology- Mining Engineering faculty, Sahand University of Technology, Tabriz, Iran

2 Department of Geology, Payame Noor University, P.O. Box 19395-3697 Tehran, I.R. of Iran

Abstract

In this study, the field features, petrography, mineralogy and geochemistry of the major and trace elements of the pyroclastic tuff layer, which is layered with the marl and sandstone sediments of the Upper Red Formation (Late Miocene), were investigated. This layer consists of dacite to trachyandesite tuff and is characterized by porphyry texture with phenocrysts of biotite (Mg-rich type), plagioclase (Na-rich type) and quartz in a glassy groundmass. Geochemically, these rocks show the characteristic of metaluminous and shoshonite magmatic suites. Wide variations of oxygen fugacity and the formation temperature of 700-800 ºC, according to the composition of biotites, can be expected for the studied rocks. These rocks show enrichment of light rare earth elements (LREE) compared to heavy rare earth elements (HREE) in the graphs of rare earth elements normalized to chondrite and have a specific negative anomaly in Eu. In addition, in the spider diagrams, an enrichment in large-ion lithophile elements (LILE) relative to high field strength elements (HFSE) is observed, along with a distinct negative anomaly in Ta, Nb, and Ti elements, which could be related to a tectonic environment (active continental margin) or origin. The studied rocks show the characteristic of non-adakite and high amounts of barium (930-1130 ppm) and strontium (400-540 ppm). According to the stratigraphic and spatial position of the tuff layer and its geochemical similarities with the Sahand volcano products, it seems that this tuff layer was formed as a result of the first explosive activity of the Sahand volcano in the Late Miocene.

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Petrological Journal

Articles in Press, Accepted Manuscript
Available Online from 10 August 2024

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History

  • Receive Date: 23 May 2024
  • Revise Date: 03 August 2024
  • Accept Date: 10 August 2024

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