Tolga Oyman
Khin Zaw
Majid Ghaderi
Chun-Kit Lai4- 1Department of Geological Engineering, Dokuz Eylül University, Izmir, Türkiye
- 2Centre for Ore Deposit and Earth Sciences, University of Tasmania, Hobart, TAS, Australia
- 3Department of Economic Geology, Tarbiat Modares University, Tehran, Iran
- 4Global Project Generation and Targeting, Fortescue Metals Group Ltd., Perth, WA, Australia
Editorial on the Research Topic
Orogenic gold deposits
This Research Topic comprises papers submitted on the geology, geochemistry, and mineralogy-petrography of orogenic gold deposits. The accepted papers include detailed mineralogical analysis and regional-scale contributions from different geological terranes, which aim to bridge the gap between laboratory studies and fieldwork of different scales (e.g., He; Zhen et al.; Li et al.; Yan et al.).
Orogenic gold deposits are found in metamorphic terranes spanning from the Paleoarchean to the Tertiary. These deposits contribute approximately one-third of the world’s total gold production (Goldfarb and Groves, 2015; Groves et al., 2020; Nassif et al., 2022). Orogenic gold deposits occur in different tectonic settings in subduction-related accretionary to collisional terranes. Worldwide exploration of gold deposits has focused on the orogenic belts of different ages, geological backgrounds, tectonic settings, and formation processes (e.g., Hronsky et al., 2012). Since the 1980s, studies from different parts of orogenic terranes focused mainly on the controls on ore formation, the source of metals, the ore-forming fluids, and the mineralizing processes. Several studies have presented evidence for and against certain models of orogenic gold ore genesis in recent years. This Research Topic focuses on the source of ore-bearing fluids and discusses the main controls and genesis of orogenic systems and associated ore deposits. The area of research covers a broad range of geographical locations.
The goal of this Research Topic is to better understand the geological processes triggering the transport and deposition of metals (Au, Ag, Sb, As, Hg, etc.) over space and time, main controls on ore, and alteration of mineral assemblages. The topics related to SI are summarized below:
• Detailed alteration mineralogy-petrography studies critical to understanding many of the studied deposits, which were complicated by the following tectonic and metamorphic overprint.
• The geochemistry, and origin of granitoids, which act either as a source for ore-bearing magmatic-hydrothermal fluids or as a heat source for remobilization of the earlier mineralization.
• Isotope geochemistry and integrated fluid inclusion studies focus on mixing fluids from different sources or later overprints to test the convenience of metamorphic models.
The papers describe the mode of occurrence, ore petrography, structural geology, metamorphic petrology, and geochemistry. The contributions to this Research Topic range from detailed mineralogical analysis (e.g., the correlation between fluid inclusion composition and Au mineralization in three dimensions or the relationship between gold and mineral paragenesis, which represents reducing and oxidizing conditions) to a regional scale synthesis (e.g., mineralization and structural controls both in brittle and ductile deformation).
Despite the increasing economic interest in orogenic gold deposits, the models explaining the sources of the metals and fluids and ore-forming processes are still under debate. The presence of CO2-CH4±Η2S-NaCl-bearing fluids in the orogenic gold system is unequivocally accepted and the source of volatiles, especially CO2 is variously interpreted from lower crustal to mantle origin. However, the relationship of CO2 with gold for mineral exploration is questionable to use as an exploration guide due to the presence of CO2 in both mineralized and barren quartz of the orogenic gold deposits. Limited but significant studies on gas composition by laser Raman at the Sigma Mine (Val-d’Or, Quebec) recorded enrichment of only CH4 as well as H2S in the gold-rich veins, although CO2 is abundant in both mineralized and barren veins (Sherlock et al., 1993). Zaw et al. (1994) also noted that high-grade mineralized ironstones contain CH4 and N2-rich ore fluids compared to barren ironstones at Tennant Creek (Northern Territory, Australia). In an earlier study, Bottrell et al. (1988) recorded that the auriferous zone (>6.7 Au ppm) showed higher CH4 values and low CO2/CH4 ratios than those of the barren veins by bulk inclusion analyses at Dolgellau Gold Belt, North Wales. The enrichment of reduced carbon and sulfur is also consistent with the precipitation of Au (HS)2− + 0.5 H2 + H+ = Au⇓ + 2H2S ⇑ and hydrocarbon-rich fluids and organic matters in the orogenic gold system (e.g., Gaboury, 2019; Gaboury, 2021; Gaboury et al., 2021; Makoundi et al., 2021). The studies and implementation of the analysis of volatile compounds in the context of orogenic gold deposits can prove highly valuable in the initial stages of exploration targeting.
The source of gold in the orogenic gold deposits is widely debated from magmatic rocks, such as basalts, lamprophyre, and felsic rocks, to sedimentary rocks rich in carbonaceous matters and iron-rich sediments as reviewed by Tomkins (2013) and Gaboury (2019), although sedimentary source model is becoming popular (e.g., Large et al., 2012; Tomkins, 2013; Gaboury et al., 2021). For exploration targeting, a well-defined “gold source” will be required for the development of the practical exploration model, especially for emerging prospective terrane, such as Phanerozoic SE Asia (e.g., Zaw et al., 2014a; Zaw et al., 2014b; Goldfarb et al., 2014; Zaw, 2019; Khaing et al., 2020; Bounliyong et al., 2021; Hlaing et al., 2021; Myint et al., 2022; Makoundi et al., 2023). Although orogenic gold (low-salinity, gas-rich fluid) and porphyry copper-gold deposits (high-salinity fluid) possess differing ore fluid characteristics, these two types are found in the same orogenic/tectonic settings and sometimes occur spatially in close proximity. Recent advances in a range of precise U-Pb-Hf zircon geochronological methods and their trace elements should be harnessed to pinpoint the timing and characteristics of these ore types in connection with the evolving orogenic belts in both time and space, which would provide guides and valuable insights for the appropriate area selection. The special edition is unable to cover all the advancements in tectonic/geodynamic evolution and metallogeny of orogenic gold deposits. However, forthcoming research promises to yield valuable insights.
Author contributions
TO: Conceptualization, Methodology, Writing–original draft, Writing–review and editing. KZ: Conceptualization, Supervision, Validation, Visualization, Writing–review and editing. MG: Conceptualization, Validation, Writing–review and editing. C-KL: Supervision, Validation, Writing–review and editing.
Funding
The author(s) declare that no financial support was received for the research, authorship, and/or publication of this article.
Acknowledgments
We would like to express our sincere gratitude to the reviewers and authors for their valuable contributions, which have played a crucial role in ensuring that the papers in this Research Topic are innovative, unique, and timely. A special note of appreciation goes to Chief Editor DL and the editorial office staff for their invaluable assistance and insightful guidance throughout the manuscript handling process.
Conflict of interest
Author C-KL was employed by Fortescue Metals Group Ltd.
The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.
Publisher’s note
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References
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Keywords: orogenic gold deposits, orogenic belts, ore formation, mineralization, metallogeny
Citation: Oyman T, Zaw K, Ghaderi M and Lai C-K (2024) Editorial: Orogenic gold deposits. Front. Earth Sci. 11:1345511. doi: 10.3389/feart.2023.1345511
Received: 27 November 2023; Accepted: 27 December 2023;
Published: 09 January 2024.
Edited and reviewed by:
David R. Lentz, University of New Brunswick Fredericton, CanadaCopyright © 2024 Oyman, Zaw, Ghaderi and Lai. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
*Correspondence: Tolga Oyman, tolga.oyman@deu.edu.tr