Actively forming Kuroko-style massive sulfide mineralisation and hydrothermal alteration at Iheya North, Okinawa Trough; key petrological results of IODP Expedition 331

Author(s): Yeats, Christopher; Hollis, Steven; Corona, Juan Carlos
Integrated Ocean Drilling Program, Expedition 331 Scientific Party
Author Affiliation(s): Primary:
Commonwealth Scientific and Industrial Research Organisation, Earth Science and Resource Engineering, Kensington, N.S.W., Australia
Other:
University of Southampton, United Kingdom
Binghamton University, United States
Volume Title: 34th international geological congress; abstracts
Source: International Geological Congress [International Geological Congress, Abstracts = Congrès Géologique International, Résumés, Vol.34, p.301; 34th international geological congress, Brisbane, Queensl., Australia, Aug. 5-10, 2012. Publisher:], [location varies], International CODEN: IGABBY
Note: In English. Accessed on June 17, 2014
Summary: IODP Expedition 331 drilled five sites at the Iheya North hydrothermal field within the Okinawa Trough backarc basin. At Iheya North, hydrothermal alteration and sulfide mineralisation is hosted in a geologically complex mixed sequence of coarse pumiceous volcaniclastic and fine hemipelagic sediments, overlying dacitic to rhyolitic volcanic substrate. At Site C0016, coring adjacent to the foot of an actively venting sulfide mound intersected massive sphalerite-(pyrite-chalcopyrite)-rich sulfides that strongly resemble the black ore of the Miocene-age Kuroko deposits of Japan -- the first time that such material has been recovered from an active seafloor hydrothermal system. The sulfide mineralisation shows clear textural evidence of formation via a combination of surface detrital and subsurface chemical processes. Altered volcanic rocks beneath the massive sulfide exhibit quartz-muscovite/illite and quartz-chlorite alteration, reminiscent of the proximal footwall alteration typically associated with ancient volcanic-hosted massive sulfide mineralisation. At the nearby Site C0013, a likely location of recent high-temperature discharge, intense hydrothermal alteration obliterates primary mineralogy and texture. Near surface alteration is dominated by kaolinite and muscovite with locally abundant native sulphur, suggesting acidic fluids; grading to Mg chlorite dominated assemblages at depths of >5m below sea floor. Late coarse-grained anhydrite veining over prints the earlier alteration and is interpreted to have precipitated from downwelling seawater that penetrated the sediments when hydrothermal activity at the site waned.
Year of Publication: 2012
Research Program: IODP Integrated Ocean Drilling Program
Key Words: 05 Petrology, Igneous and Metamorphic; 27 Economic Geology, Metals; Depth; Expedition 331; Hydrothermal alteration; Hydrothermal vents; IODP Site C0016; Igneous rocks; Iheya North hydrothermal field; Integrated Ocean Drilling Program; Kuroko-type deposits; Massive deposits; Massive sulfide deposits; Metal ores; Metasomatism; Mineral assemblages; Mineralization; Native elements; North Pacific; Northwest Pacific; Ocean floors; Okinawa Trough; Overprinting; Pacific Ocean; Sea water; Sulfur; Veins; Volcanic rocks; West Pacific
Coordinates: N274727 N274727 E1265348 E1265348
Record ID: 2014083195
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