Genetic Environments of the Eunjeok Au–Ag Deposit in the Yeongam District: Implications for Cretaceous Epithermal Au–Ag Mineralization in South Korea
Abstract
:1. Introduction
2. Tectonic Framework
3. Geology
4. Ore veins and Hydrothermal Alterations
5. Mineralization and Paragenesis
5.1. Stage I Vein Mineralization
5.2. Stage II Vein Mineralization
5.3. Stage III Vein Mineralization
5.4. Stage IV Vein Mineralization
6. Fluid Inclusion Study
6.1. Inclusions in Stage II Veins
6.2. Inclusions in Stage III Vein
6.3. Inclusions in Stage IV Carbonate Vein
6.4. Variations in Temperature and Composition of Auriferous Fluids
7. Chemical Environments of Ore Deposits
8. Stable Isotope Studies
8.1. Sulfur Isotope Study
8.2. Oxygen and Carbon Isotope Studies
9. Discussion
10. Conclusions
Author Contributions
Funding
Data Availability Statement
Acknowledgments
Conflicts of Interest
References
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Elements Sample No. | Fe % | Pb % | Zn % | Cu mg/kg | In mg/kg | Ga mg/kg | Ge mg/kg | Se mg/kg | Te mg/kg | Y mg/kg | Mo mg/kg | Re mg/kg | W mg/kg | Sm mg/kg | Eu mg/kg | Ba mg/kg | Ag mg/kg | Au mg/kg | U mg/kg |
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
EJ-3 | 3.56 | 0.08 | 0.61 | 1787 | 8 | 71 | 141.8 | 8 | 38 | 213 | 350 | 1 | 837 | 37 | 6 | 3046 | 206 | 41 | 95 |
EJ-4 | 12.84 | 0.08 | 0.13 | 50 | 4 | 33 | 273.7 | 89 | 76 | 70 | 1325 | N.D | 651 | 15 | 3 | 58 | 216 | 100 | 21 |
EJ-5 | 4.79 | 0.17 | 0.30 | 92 | 2 | 13 | 123.1 | 31 | 28 | 37 | 4787 | 2 | 1006 | 12 | 1 | 524 | 325 | 132 | 39 |
EJ-7 | 2.95 | 0.29 | 0.01 | 175 | 6 | 53 | 111.3 | 6 | - | 334 | 657 | 1 | 876 | 42 | 4 | 4843 | 157 | 10 | 114 |
EJ-8 | 4.18 | 0.20 | 0.71 | 1751 | 5 | 38 | 106.9 | 75 | 16 | 9 | 262 | 2 | 1202 | 1 | N.D | 1990 | 124 | 304 | 4 |
EJ-10 | 1.85 | 0.45 | 0.39 | 2690 | 11 | 89 | 94.5 | 135 | - | 59 | 755 | 3 | 673 | 15 | 2 | 304 | 158 | 30 | 14 |
Description | K (%) | 40Ar (mol/g) | 40Ar Rad. (%) | Age (Ma) |
---|---|---|---|---|
Sericite from alteration selvage | 7.40 | 1.3236 × 10−10 | 80.49 | 86.15 ± 7.7 |
Sample No. | Stage | Association Minerals | Fe (wt.%) | As (wt.%) | S (wt.%) | Total | As (atomic %) |
---|---|---|---|---|---|---|---|
Ej-3 | Ⅱa | py + asp | 34.65 | 43.90 | 21.52 | 99.92 | 31.21 |
Ej-5 | Ⅱa | py + asp | 35.08 | 44.24 | 21.08 | 101.06 | 31.47 |
Ej-6 | Ⅱa | py + asp | 34.89 | 43.51 | 20.53 | 98.93 | 31.47 |
Ej-12 | Ⅱb | py + asp + sp | 35.29 | 42.81 | 21.70 | 99.80 | 30.40 |
Ej-13 | Ⅱb | py + asp + el + sp + arg | 35.11 | 43.40 | 21.26 | 99.77 | 30.96 |
Ej-16 | Ⅱc | py + arg + cp + gn | 34.50 | 42.63 | 22.56 | 99.69 | 30.10 |
Ej-19 | Ⅱc | py + asp | 35.01 | 43.22 | 21.94 | 100.17 | 30.56 |
Sample No. | Stage | Association Minerals | FeS (mole %) |
---|---|---|---|
Ej-1 | Ⅱa | py + asp + po | 18.20 |
Ej-2 | Ⅱa | py + asp | 17.50 |
Ej-3 | Ⅱb | asp + gn | 10.71 |
Ej-8 | Ⅱb | asp + py | 8.95 |
Ej-9 | Ⅱb | py + arg + el + gn + cp | 8.58 |
Ej-11 | Ⅱb | asp + py | 8.95 |
Ej-14 | Ⅱb | asp + gn + el + arg | 10.71 |
Ej-15 | Ⅱb | py + el + gn | 10.24 |
Ej-17 | Ⅱb | asp + py + el + gn | 9.80 |
Ej-22 | Ⅱb | py + el + gn | 10.02 |
Sample No. | Au (wt. %) | Ag (wt. %) | Atomic Fraction (NAg) |
---|---|---|---|
Ej-9 | 37.60 | 62.77 | 0.7529 |
Ej-13 | 27.89 | 71.40 | 0.8238 |
Ej-14 | 33.24 | 66.71 | 0.7857 |
Ej-15 | 33.30 | 65.70 | 0.7777 |
Ej-17 | 21.85 | 78.15 | 0.8672 |
Sample No. | Stage | Minerals | δ34S (‰) | py-sp | T (°C) |
---|---|---|---|---|---|
Ej-4 | alteration | asp | 6.52 | ||
Ej-5 | alteration | asp | 6.70 | ||
Ej-6 | alteration | asp | 6.56 | ||
Ej-1 | Ⅱa | asp | 7.40 | ||
Ej-2 | Ⅱa | asp | 7.46 | ||
Ej-3 | Ⅱa | asp | 7.46 | ||
Ⅱa | py | 4.93 | |||
Ej-8 | Ⅱa | py | 4.91 | ||
Ej-9 | Ⅱa | py | 5.21 | ||
Ej-12 | Ⅱb | py | 6.50 | 1.1 | 251 ± 38 |
Ⅱb | sp | 5.40 | |||
Ⅱb | sp | 5.50 | |||
Ej-14 | Ⅱc | asp | 7.00 | ||
Ej-15 | Ⅱc | py | 6.20 |
Sample No. | Minerals | δ13C (‰) | δ18O (‰) | δ18OH2O (‰) | T (℃) |
---|---|---|---|---|---|
Ej-23 | calcite | −4.93 | 5.53 | 3.01 | 220 |
Ej-24 | calcite | −5.37 | 5.82 | 2.72 | 220 |
Deposit | Eunjeok [11,12] | Mugeuk [4,5,6,7,10] | Haenam–Jindo [3,9,47,48] |
---|---|---|---|
Geologic setting | Volcano–tectonic setting(Mokpo cauldron) | Pull-apart sedimentary setting(Eumseong basin) | Volcano–tectonic setting (Haenam basin) |
Major fault system | Gwangju–Hwangsan fault | Gongju–Eumseong fault | Gwangju–Yeongdong fault |
Host rock | Late Cretaceous volcanics, granite | Jurassic granitoids and sedimentary rocks | Intermediate-to-silicic extrusive rocks in the Cretaceous volcano–tectonic terrane |
Age of gold–silver mineralization | 86.0 Ma | 105.7 or 98.0 Ma | <70.3 Ma |
Commodities | Ag ≥ Au | Ag ≥ Au | Ag ≫ Au |
Mineral composition (range, average) | |||
Au (at.%) in el | 62.77–78.15 | 5.2–82.0 | 8.6–57.5 |
FeS (mole%) in sp | 8.58–10.71 | 0.03–7.4 | 0.2–6.6 |
As (at.%) in ap | 31.47–32.20 | 28.5–32.7 | Not found |
Fluid inclusion data | |||
Fluid system | H2O-NaCl | H2O-NaCl | H2O/-CO2-NaCl |
Type | I ≫ II | I ≫ II | I > II > III |
Th (℃) | 204–314 | 137–341 | 113–298 |
Salinity (wt.% equiv. NaCl) | 2.5–5.4 | 0.8–7.9 | 0.0–3.4 |
Isotope data (range, average) | |||
Oxygen (‰) | |||
quartz | - | 7.7–12.7, 9.4 | 1.6–10.2 |
calculated δ18OH2O | - | −1.2 to 3.8, 0.5 | −10.1 to −2.1 |
carbonate | 5.53–5.82 | 6.9 | 0.0–3.8 |
calculated δ18OH2O | 2.72–3.01 | −2.6 | −9.5 to −7.8 |
Hydrogen (‰) | |||
quartz | - | −73 to −71, −72 | −76 to −71 |
carbonate | - | −76 | −80 to −52 |
Carbon (‰)(carbonate) | −4.94 to −5.37 | −4.7 | −6.9 to −5.0 |
Sulfur (‰) | −4.91 to −7.46 | - | - |
calculated δ34SH2S | 3.7–5.1 | - | - |
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Heo, C.-H.; Kim, S.-Y.; Oh, I.-H. Genetic Environments of the Eunjeok Au–Ag Deposit in the Yeongam District: Implications for Cretaceous Epithermal Au–Ag Mineralization in South Korea. Minerals 2021, 11, 1088. https://doi.org/10.3390/min11101088
Heo C-H, Kim S-Y, Oh I-H. Genetic Environments of the Eunjeok Au–Ag Deposit in the Yeongam District: Implications for Cretaceous Epithermal Au–Ag Mineralization in South Korea. Minerals. 2021; 11(10):1088. https://doi.org/10.3390/min11101088
Chicago/Turabian StyleHeo, Chul-Ho, Seong-Yong Kim, and Il-Hwan Oh. 2021. "Genetic Environments of the Eunjeok Au–Ag Deposit in the Yeongam District: Implications for Cretaceous Epithermal Au–Ag Mineralization in South Korea" Minerals 11, no. 10: 1088. https://doi.org/10.3390/min11101088