Epitaxial growth mechanism of the Au-bearing arsenian pyrites in Yeganli-2 gold deposit, north of Takab: New insight from complex interaction of crystal growth kinetics and gold concentration

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Department of Geology, Bu-Ali Sina university

Abstract

Understanding the complex interplay between the crystallization processes and distribution of precious trace elements (e.g., gold) is of great importance in economic geology. In this contribution, the effective factors on the incorporation of trace elements, especially gold, during the epitaxial growth of Au-bearing arsenian pyrite crystal in the Yeganli gold deposit (north of Takab) have been interpreted by advanced electron-atomic techniques. According to SEM evidence, As-rich (> 3 ppm) bright bands with a thickness of 10 nm have other trace elements (e.g., Cu, Sb, Pb, and Tl). According to the evidence of APT, the heterogeneous distribution of trace elements with the appearance of islands along the discontinuous planar features from the outer edge of the As-rich bright bands is known as Stranski-Krastanov growth mode, and with the distance from these bands, epitaxial growth occurs as a result of periodic fluid fluctuations. Also, As-induced lattice distor‌tion facilitates surface adsorption of dopant trace metals, which leads to “unstructured” impurities clustering lo‌cally in crystal defects. In summary, based on nano-scale textural-chemical evidence from arsenitepyrite crystals, it can be said that the kinetics of crystal growth and its complex interaction with the equilibrating hydrothermal fluid play an important role in the distribution and concentration of gold, which can be considered as a prospecting implication at the mineralogical scale.

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History

  • Receive Date: 18 June 2025
  • Revise Date: 13 August 2025
  • Accept Date: 13 September 2025

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