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The Dairi SEDEX Zn + Pb + Ag deposit (North Sumatra, Indonesia): Insights from mineralogy and sulfur isotope systematics
Rivai T.A.a, Syafrizalc, Yonezu K.a, Tindell T.a, Boyce A.J.d, Sanematsu K., Satori S., Watanabe K.a
a Department of Earth Resources Engineering, Kyushu University, Fukuoka, Japan
b Geological Survey of Japan, National Institute of Advanced Industrial Science and Technology, Tsukuba, Japan
c Faculty of Mining and Petroleum Engineering, Bandung Institute of Technology, Bandung, Indonesia
d Scottish Universities Environmental Research Centre, East Kilbride, United Kingdom
[vc_row][vc_column][vc_row_inner][vc_column_inner][vc_separator css=”.vc_custom_1624529070653{padding-top: 30px !important;padding-bottom: 30px !important;}”][/vc_column_inner][/vc_row_inner][vc_row_inner layout=”boxed”][vc_column_inner width=”3/4″ css=”.vc_custom_1624695412187{border-right-width: 1px !important;border-right-color: #dddddd !important;border-right-style: solid !important;border-radius: 1px !important;}”][vc_empty_space][megatron_heading title=”Abstract” size=”size-sm” text_align=”text-left”][vc_column_text]© 2020 Elsevier B.V.The Dairi Zn + Pb + Ag deposit is the only giant SEDEX deposit that has been discovered to date in Sumatra. Ore-gangue mineralogy and sulfur isotope studies have been carried out to elucidate the paragenetic sequence, deformation of ore, flow direction of ore forming fluid, and sources of sulfur in the Dairi deposit. Stratiform orebodies hosted by the Julu unit (interbedded dolomitic siltstone and carbonaceous shale; multilayers; accounting for greater than 90% of metal resources) consist of pyrite-rich massive, sphalerite-rich massive, bedded sulfide, galena-rich breccias, and vein ore types, whereas discordant orebodies hosted by the Jehe unit (massive and brecciated arenaceous dolostone) comprise vein and disseminated ore types. Fine-grained, subhedral-euhedral and framboidal pyrite (enriched in Co, Ni, Cu, As, Bi, Ag relative to hydrothermal pyrite) were precipitated in the diagenetic stage, followed by precipitation of pyrite (enriched in Zn, Pb, Mn, Tl relative to diagenetic pyrite), sphalerite, galena, chalcopyrite, pyrrhotite, acanthite, tetrahedrite, tennantite, pyrargyrite, boulangerite, freieslebenite, and diaphorite in the hydrothermal stage derived from the exhaled ore-forming fluid. Metamorphic pyrite (enriched in Co and depleted in Cu, Zn, Mn, Tl, Ag relative to the other pyrites) formed from pyrrhotite (depleted in Co relative to metamorphic pyrite) and soft sulfides were remobilized into pyrite fractures and veins during sub-greenschist metamorphism. Ore-forming fluid ascended through fractures in the Jehe unit (forming the discontinuous orebodies) and then it discharged and flowed from SE to NW on the seafloor (forming the stratiform orebodies). Reduced sulfur for diagenetic pyrite (δ34S = -4.1‰ to + 11.6‰) was supplied by bacteriogenic reduction of Carboniferous seawater sulfate. Hydrothermal sulfur was considered as the source of sulfur for the Jehe-hosted orebodies (δ34S = +3.5‰ to + 8.0‰). The heavier δ34S of sulfides in the Julu-hosted orebodies (δ34S = +6.4‰ to + 28.8‰) suggests large-scale bacteriogenic reduction of Carboniferous seawater sulfate in a restricted, anoxic basin. A bacteriogenic reduced sulfur reservoir, rather than hydrothermal sulfur, may be more plausible to account for the scale of the giant Dairi deposit.[/vc_column_text][vc_empty_space][vc_separator css=”.vc_custom_1624528584150{padding-top: 25px !important;padding-bottom: 25px !important;}”][vc_empty_space][megatron_heading title=”Author keywords” size=”size-sm” text_align=”text-left”][vc_column_text]Base metals,Dairi,Indonesia,Ore-forming fluid,Sedex deposits,Sulfur isotope,Sumatra,Sumatra , Indonesia[/vc_column_text][vc_empty_space][vc_separator css=”.vc_custom_1624528584150{padding-top: 25px !important;padding-bottom: 25px !important;}”][vc_empty_space][megatron_heading title=”Indexed keywords” size=”size-sm” text_align=”text-left”][vc_column_text]Dairi,Indonesia,Pyrite-pyrrhotite trace elements,Sediment-hosted base metal deposits,Sedimentary exhalative ore,Sumatra[/vc_column_text][vc_empty_space][vc_separator css=”.vc_custom_1624528584150{padding-top: 25px !important;padding-bottom: 25px !important;}”][vc_empty_space][megatron_heading title=”Funding details” size=”size-sm” text_align=”text-left”][vc_column_text][{‘$’: “We would like to thank the management and staffs of PT Bumi Resources Minerals, Tbk. for allowing us to conduct field surveys and sampling inside the company’s concession in Dairi. We are also immensely grateful to Ir. Dedy Hendrawan and Dr. Suseno Kramadibrata for personal discussion about the Dairi deposit, to Prof. Akira Imai for invaluable comments and advice regarding the manuscript content and quality, and to Mrs. Alison McDonald for assisting us in sulfur isotope study. Dr. Yoshiaki Kon is thanked for his supervision and guidance during LA-ICP-MS analysis. This study is partially funded by Advanced Graduate Program in Global Strategy for Green Asia and the Society of Resource Geology.”}, {‘$’: ‘We would like to thank the management and staffs of PT Bumi Resources Minerals, Tbk. for allowing us to conduct field surveys and sampling inside the company’s concession in Dairi. We are also immensely grateful to Ir. Dedy Hendrawan and Dr. Suseno Kramadibrata for personal discussion about the Dairi deposit, to Prof. Akira Imai for invaluable comments and advice regarding the manuscript content and quality, and to Mrs. Alison McDonald for assisting us in sulfur isotope study. Dr. Yoshiaki Kon is thanked for his supervision and guidance during LA- ICP -MS analysis. This study is partially funded by Advanced Graduate Program in Global Strategy for Green Asia and the Society of Resource Geology .’}][/vc_column_text][vc_empty_space][vc_separator css=”.vc_custom_1624528584150{padding-top: 25px !important;padding-bottom: 25px !important;}”][vc_empty_space][megatron_heading title=”DOI” size=”size-sm” text_align=”text-left”][vc_column_text]https://doi.org/10.1016/j.oregeorev.2020.103510[/vc_column_text][/vc_column_inner][vc_column_inner width=”1/4″][vc_column_text]Widget Plumx[/vc_column_text][/vc_column_inner][/vc_row_inner][/vc_column][/vc_row][vc_row][vc_column][vc_separator css=”.vc_custom_1624528584150{padding-top: 25px !important;padding-bottom: 25px !important;}”][/vc_column][/vc_row]