TY - JOUR
T1 - Mineralogical and Geochemical Characteristics of the Utanobori Gold Deposit in Northern Hokkaido, Japan
AU - Sorulen, Thomas T.
AU - Takahashi, Ryohei
AU - Tanaka, So
AU - Suzuki, Kana
AU - Imai, Akira
AU - Watanabe, Yasushi
AU - Kikuchi, Shingo
N1 - Funding Information:
We thank Monbukagakusho (MEXT) for the support and scholarship offered during the research. We thank Irving Resources Inc., especially Ms Akiko Levinson, Dr Quinton Hennigh, and Mr Hidetoshi Takaoka for information, permission, and financial support to the fieldwork conducted and Ar‐Ar age dating of samples. We are grateful to Prof. Hiroharu Matsueda of Hokkaido University and Mr Ken Nakayama of Kochi University for their samples and to Dr Tetsuo Suzuki of H.R.S., Dr Masahiro Yahata of My Geo, and Mr Haruo Harada of Mitsui Mineral Development Engineering Co., Ltd. for their kind support and assistance. We also thank Dr Hinako Sato for her technical assistance in ICP‐MS and AAS analyses and Mr Akira Hara and Mr Aoki Nozomi of Akita University for their kind assistance in the translation from Japanese to English during a review of Japanese literature. We also extend our sincere gratitude to Dr Ken‐ichiro Hayashi of Resource Geology, Associate Editor, and Dr Arifudin Idrus of Gadjah Mada University for their critical review and valuable comments that significantly improved this manuscript. This work was supported by JSPS KAKENHI grant number 17K06982, the Japan Mining Promotive Foundation, and the Society of Resource Geology.
Funding Information:
We thank Monbukagakusho (MEXT) for the support and scholarship offered during the research. We thank Irving Resources Inc., especially Ms Akiko Levinson, Dr Quinton Hennigh, and Mr Hidetoshi Takaoka for information, permission, and financial support to the fieldwork conducted and Ar-Ar age dating of samples. We are grateful to Prof. Hiroharu Matsueda of Hokkaido University and Mr Ken Nakayama of Kochi University for their samples and to Dr Tetsuo Suzuki of H.R.S., Dr Masahiro Yahata of My Geo, and Mr Haruo Harada of Mitsui Mineral Development Engineering Co., Ltd. for their kind support and assistance. We also thank Dr Hinako Sato for her technical assistance in ICP-MS and AAS analyses and Mr Akira Hara and Mr Aoki Nozomi of Akita University for their kind assistance in the translation from Japanese to English during a review of Japanese literature. We also extend our sincere gratitude to Dr Ken-ichiro Hayashi of Resource Geology, Associate Editor, and Dr Arifudin Idrus of Gadjah Mada University for their critical review and valuable comments that significantly improved this manuscript. This work was supported by JSPS KAKENHI grant number 17K06982, the Japan Mining Promotive Foundation, and the Society of Resource Geology.
Publisher Copyright:
© 2019 The Society of Resource Geology
PY - 2019/10/1
Y1 - 2019/10/1
N2 - The Utanobori gold deposit is a low-sulfidation, epithermal vein-type deposit located in northern Hokkaido, Japan. The deposit is hosted by conglomerate, sandstone, and tuff of the Middle to Late Miocene Esashi Formation. These rocks were hydrothermally altered. Silica sinters and quartz-adularia veins are common in the deposit. The quartz-adularia veins either contain a ginguro band, which corresponds to the main gold-bearing vein (Type 1 Veins), or do not contain a ginguro band but contain minor adularia (Type 2 Veins). Type 1 Veins are divided into three stages with 12–14 substages. Ore minerals identified include electrum, naumannite, chlorargyrite, bromargyrite, an unidentified Fe-Sb mineral, and an Fe-(Sb)-As mineral. These ore minerals formed in the main mineralization stages I (bands I-b and I-d) and II (band II-a). Scanning electron microscopy with cathodoluminescence images show that cathodoluminescence-dark microcrystalline quartz exhibiting colloform (ghost-sphere) texture is closely associated with ore minerals in the Type 1 Vein and Type 2 Vein, and the Al and K contents of such quartz are commonly '1000 ppm. This indicates that the ore minerals were crystallized from alkaline, silica-saturated fluids at temperatures '200°C, which initially deposited amorphous silica that was recrystallized to microcrystalline quartz. The average Au content of electrum is 52.5 at% Au (n = 10), 65.7 at% Au (n = 20), and 55.5 at% Au (n = 5) in bands I-b, I-d, and II-a, respectively, of Type 1 Veins. The δ34SCDT values of two fine-grained disseminated pyrites in the altered conglomerate and bedded tuff in the argillic altered zone are −4.3 and −4.2‰. Ar-Ar dating on adularia yielded 13.6 ± 0.06 Ma, 13.6 ± 0.07 Ma, and 13.6 ± 0.06 Ma for the stages I, II, and III of the Type 1 Vein, respectively. K-Ar ages determined on adularia in the silica sinter and on whole-rock of glassy rhyolite of the Esashi Formation are 15.0 ± 0.4 Ma and 14.6 ± 0.4 Ma, respectively. These radiometric ages indicate that silica sinter associated with the rhyolitic volcanic rocks formed prior to the main gold mineralization.
AB - The Utanobori gold deposit is a low-sulfidation, epithermal vein-type deposit located in northern Hokkaido, Japan. The deposit is hosted by conglomerate, sandstone, and tuff of the Middle to Late Miocene Esashi Formation. These rocks were hydrothermally altered. Silica sinters and quartz-adularia veins are common in the deposit. The quartz-adularia veins either contain a ginguro band, which corresponds to the main gold-bearing vein (Type 1 Veins), or do not contain a ginguro band but contain minor adularia (Type 2 Veins). Type 1 Veins are divided into three stages with 12–14 substages. Ore minerals identified include electrum, naumannite, chlorargyrite, bromargyrite, an unidentified Fe-Sb mineral, and an Fe-(Sb)-As mineral. These ore minerals formed in the main mineralization stages I (bands I-b and I-d) and II (band II-a). Scanning electron microscopy with cathodoluminescence images show that cathodoluminescence-dark microcrystalline quartz exhibiting colloform (ghost-sphere) texture is closely associated with ore minerals in the Type 1 Vein and Type 2 Vein, and the Al and K contents of such quartz are commonly '1000 ppm. This indicates that the ore minerals were crystallized from alkaline, silica-saturated fluids at temperatures '200°C, which initially deposited amorphous silica that was recrystallized to microcrystalline quartz. The average Au content of electrum is 52.5 at% Au (n = 10), 65.7 at% Au (n = 20), and 55.5 at% Au (n = 5) in bands I-b, I-d, and II-a, respectively, of Type 1 Veins. The δ34SCDT values of two fine-grained disseminated pyrites in the altered conglomerate and bedded tuff in the argillic altered zone are −4.3 and −4.2‰. Ar-Ar dating on adularia yielded 13.6 ± 0.06 Ma, 13.6 ± 0.07 Ma, and 13.6 ± 0.06 Ma for the stages I, II, and III of the Type 1 Vein, respectively. K-Ar ages determined on adularia in the silica sinter and on whole-rock of glassy rhyolite of the Esashi Formation are 15.0 ± 0.4 Ma and 14.6 ± 0.4 Ma, respectively. These radiometric ages indicate that silica sinter associated with the rhyolitic volcanic rocks formed prior to the main gold mineralization.
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U2 - 10.1111/rge.12211
DO - 10.1111/rge.12211
M3 - Article
AN - SCOPUS:85070768846
SN - 1344-1698
VL - 69
SP - 402
EP - 429
JO - Resource Geology
JF - Resource Geology
IS - 4
ER -