In Situ Ore Formation Experiment: Amino Acids and Amino Sugars Trapped in Artificial Chimneys on Deep-Sea Hydrothermal Systems at Suiyo Seamount, Izu-Bonin Arc, Pacific Ocean

摘要

The present study reports on the bio-organic composition of a deep-seaventing hydrothermal system originating from arc volcanism; the origin of theparticulates in hydrothermal fluids from the Suiyo Seamount in the southernIzu-Bonin (Ogasawara) Arc is discussed with regard to amino compounds. Chimneysamples on deep-sea hydrothermal systems and core samples at Suiyo Seamountwere determined for amino acids, and occasionally amino sugars. Two types ofchimney samples were obtained from active hydrothermal systems by submersiblevehicles: one was natural chimney (NC) on a hydrothermal natural vent; theother was artificial chimneys (AC), mainly formed by the growth and depositionof sulfide-rich particulate components in a Kuwabara-type in situ incubator (KIincubator). Total hydrolyzed amino acids (THAA) and hydrolyzed hexosamines (HA)in AC ranged from 10.7 nmol/g to 64.0 nmol/g and from 0 nmol/g to 8.1 nmol/g,respectively, while THAA in hydrothermally altered core samples ranged from26.0 nmol/g to 107.4 nmol/g-rock. The THAA was thus of the same order ofmagnitude in AC and core samples. The representative biochemical indicatorratios of {eta}-alanine/aspartic acid and {gamma}-aminobutyric acid/glutamicacid were low. This is consistent with a large microbial population and labilesubterranean biogenic organic compounds. A micro energy dispersive X-rayspectrometer ({mu}EDX) was used to show that the formation of massive pyrite-and chalcopyrite-ores, the major matrixes of the natural chimney structures,were processed during hydrothermal activity. These data suggest that labileparticulate organic matter (POM) and/or dissolved organic matter (DOM) fromhydrothermal fluid were continuously trapped to form concentrated organicmatter in a sulfide-rich matrix.