Major and trace elements geochemistry of pyrite: Implications for development of invisible gold deposits in the Takab-Angouran district, NW Iran

Tale Fazel, Ebrahim

Volume 7, Issue 2 (Autumn&Winter 2022) KJES 2022, 7(2): 97-117 | Back to browse issues page

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Tale Fazel E. Major and trace elements geochemistry of pyrite: Implications for development of invisible gold deposits in the Takab-Angouran district, NW Iran. KJES 2022; 7 (2) :97-117
URL: http://gnf.khu.ac.ir/article-1-2800-en.html

Major and trace elements geochemistry of pyrite: Implications for development of invisible gold deposits in the Takab-Angouran district, NW Iran

Ebrahim Tale Fazel ^*

Bu-Ali Sina University , tale.fazel@gmail.com

Abstract: (1212 Views)

Fe-As sulfide minerals are the most important hosts of gold in various deposits, which sedimentary rock-hosted disseminated gold deposits is known by high content of gold in arsenian pyrite composition. In this study, the textural-geochemical charecteristics of arsenian pyrite is specifically aimed at understanding how gold is distributed in the form of nanoparticles (Au⁰) or participation in the mineral crystal lattice (Au⁺) in three ore deposits: Zarshuran (average grade: 2.63 g/t), Agdarreh (average grade: 3.7 g/t), and Arabshah (average grade: 1.2 g/t), at Takab-Angouran metallogenic zone, have been studied. According to the results, a negative chemical relationship between arsenic and sulfur (R² = −0.61) was observed in the arsenian pyrite composition, which indicates the presence of As³⁺ with the empirical formula of Fe(As_xS_1−x)₂. Due to the paragenetic association of gold with pyrite and sphalerite ores, the absence of oxide minerals, near-neutral to acidic nature of pH (presence of argillic±sericitic alteration), and the high activity of sulfur, shown that the gold solubility and its transfer were conducted by Au(HS)₂^– bisulfide complex. Evidence suggests that pervasive fluid-rock interaction is caused decreased S₂^– activity - has resulted instability of bisulfide complex and gold deposition in the pyrite veins.

Keywords: Auriferous arsenian pyrite, Fe-rich carbonate, decarbonation alteration, Takab-Angouran district

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Type of Study: Review Article | Subject: Economic Geology
Received: 2022/01/16 | Accepted: 2022/04/5 | Published: 2022/06/26