--> ABSTRACT: Current Research at the Izena Hydrothermal Field in the Okinawa Trough, Pt. 1, A Black Smoker, Chimneys and Sulfide Mounds Investigated by the Japanese Submersible SHINKAI 2000., by Ko-Ichi Nakamura; #90097 (1990).

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ABSTRACT: Current Research at the Izena Hydrothermal Field in the Okinawa Trough, Pt. 1, A Black Smoker, Chimneys and Sulfide Mounds Investigated by the Japanese Submersible SHINKAI 2000.

Ko-Ichi Nakamura

The submersible studies by the JAMSTEC SHINKAI 2000 were conducted at the Izena hydrothermal site. Five and ten dives were carried out in September 1988 and in June to July 1989, respectively.

A black smoker, which was injecting ^sim320°C hot water and many active chimneys covered by Paralvinella sp. were observed on the sulfide mounds. Each mound is about 10 m high and 10 to 30 m long. Upper part of the mound is composed of massive or porous sulfide ore gravels. Several ore gravels show conglomeratic textures. Massive ore is composed of sphalerite, tetrahedrite, galena, chalcopyrite, and minor amount of pyrite. The matrix of the ore conglomerate is mainly composed of sphalerite and barite. These facts indicate destructive events at the mound and subsequent succession of hydrothermal activity. Such multistage activity corresponds to the variety of metal content of the ores. However, in general, the ores contain zinc, lead, copper, and iron in order of abundance with go d and silver up to 12 ppm and 1000 ppm, respectively. The hot water from the black smoker and chimneys is rich in volatile components, such as CO2, CH4, and H2S. The CO2-rich fluid bubbles were observed to be flowing out from the surrounding altered and heated sediments.

AAPG Search and Discovery Article #90097©1990 Fifth Circum-Pacific Energy and Mineral Resources Conference, Honolulu, Hawaii, July 29-August 3, 1990