量研学術機関リポジトリ「QST-Repository」は、国立研究開発法人 量子科学技術研究開発機構に所属する職員等が生み出した学術成果（学会誌発表論文、学会発表、研究開発報告書、特許等）を集積しインターネット上で広く公開するサービスです。 Welcome to QST-Repository where we accumulates and discloses the academic research results(Journal Publications, Conference presentation, Research and Development Report, Patent, etc.) of the members of National Institutes for Quantum Science and Technology.
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Ages of hydrothermal mineral samples were determined by 230Th/234U radioactive disequilibrium dating technique. Sulfide
samples were collected from four active sites in the most
southern region of the Mariana Trough; Snail site (located on
the spreading axis), Archaean site (located on a mound 1.5 km
distant from the axis), Pika site (located on an off-axis knoll
4.9 km distant from the axis) and Urashima site (located on the
northern slope of the same knoll). Samples were collected from
active hydrothermal vents and inactive sulfide spires during
dive expeditions of YK10-10 cruise using the submersible
SHINKAI6500. In addition, massive sulfide ores were cored
by shallow drilling using a BMS (Benthic Multi-coring
System) during the TAIGA10 cruise.
Sulfide ores collected from the hydrothermal mound of the
Archaean site range in age from < 100 to 3520 years old. The
growth rate of the massive sulfide ore body is calculated to be
0.12 - 1.5 mm/year based on results of the core samples. These
results suggest that a few thousand years of continuous
hydrothermal activity would be required for formation of
massive ore deposit that overlays the hydrothermal mound 50-
100 m high and 250-300 m in diameter.
Sulfide ores collected from the two hydrothermal fields
located on the off-axis knoll (Pika and Urashima sites) are up
to 9000 years old. When combined with geophysical evidence
for crustal velocity anomaly, this mineralization is considered
to be in the late-stage of the hydrothermal activity, and related
to a cooling magma body.
Dating Hydrothermal Minerals in Active Hydrothermal Fields in the Southern Mariana Trough
