Mineralogical and Fluid Inclusion Studies on Seafloor Hydrothermal Vents at TA25 Caldera, Tonga Arc

Title
Mineralogical and Fluid Inclusion Studies on Seafloor Hydrothermal Vents at TA25 Caldera, Tonga Arc
Author(s)
최선기; 박상준; 최상훈; 이경용; 김현섭; 이인경
KIOST Author(s)
Choi, Sun Ki(최선기)Kim, Hyun Sub(김현섭)
Alternative Author(s)
최선기; 박상준; 이경용; 김현섭
Publication Year
2015-12-17
Abstract
The extensive hydrothermal vent field was discovered at TA25(V18s-HR in the SO-167 cruise) caldera in the Tonga arc, southwest Pacific. The TA25 caldera is a submarine volcano of dacitic composition and hosts the NE- and NW-trending hydrothermal vent on the western caldera wall. These active hydrothermal crusters are mostly small (chimney: <0.5m in tall sulfide mound: <3m in diameter) and immature, and emit the transparent fluids of which temperature range from 150℃ to 242℃ (average = 203℃). The hydrothermal sulfide ores, recovered by ROV and/or TV-grab, are mainly composed of sphalerite, pyrite, marcasite, galena, chalcopyrite, covellite, tennantite, enargite and sulfates such as barite, gypsum/anhydrite. It is observed that three distinct mineralogical zonation from exterior to interior of the chimneys: (1) barite-gypsum/anhydrite-pyrite-sphalerite (2) sphalerite-pyrite-galena±chalcopyrite (3) sphaleirte-pyrite-chalcopyrite-enargite-tennantite±galena±covellite. FeS content in sphalerite increases from chimney exterior to interior. Chalcopyrite is more abundant in the mound than in the chimney, implying fluid temperatures in mound are greater than in the chimney. The enargite assemblage (pyrite-chalcopyrite-enargite-tennantite) is indicative of high-sulfidation epithermal deposits. Fluid inclusions on barite crystals from mound samples show mono-type inclusion (two-phase liquid-rich inclusions) which is othermal vent on the western caldera wall. These active hydrothermal crusters are mostly small (chimney: <0.5m in tall sulfide mound: <3m in diameter) and immature, and emit the transparent fluids of which temperature range from 150℃ to 242℃ (average = 203℃). The hydrothermal sulfide ores, recovered by ROV and/or TV-grab, are mainly composed of sphalerite, pyrite, marcasite, galena, chalcopyrite, covellite, tennantite, enargite and sulfates such as barite, gypsum/anhydrite. It is observed that three distinct mineralogical zonation from exterior to interior of the chimneys: (1) barite-gypsum/anhydrite-pyrite-sphalerite (2) sphalerite-pyrite-galena±chalcopyrite (3) sphaleirte-pyrite-chalcopyrite-enargite-tennantite±galena±covellite. FeS content in sphalerite increases from chimney exterior to interior. Chalcopyrite is more abundant in the mound than in the chimney, implying fluid temperatures in mound are greater than in the chimney. The enargite assemblage (pyrite-chalcopyrite-enargite-tennantite) is indicative of high-sulfidation epithermal deposits. Fluid inclusions on barite crystals from mound samples show mono-type inclusion (two-phase liquid-rich inclusions) which is
URI
https://sciwatch.kiost.ac.kr/handle/2020.kiost/24978
Bibliographic Citation
AGU Fall meeting, pp.1, 2015
Publisher
American
Type
Conference
Language
English
Publisher
American
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