Catalogo Articoli (Spogli Riviste)

OPAC HELP

Titolo:
Compositional variation of pyrite, diagenetic alteration and genesis of tone sandstone-type uranium deposits in Japan
Autore:
Shikazono, N; Nakata, M;
Indirizzi:
Keio Univ, Fac Sci & Technol, Dept Appl Chem, Kohoku Ku, Yokohama, Kanagawa 2238522, Japan Keio Univ Yokohama Kanagawa Japan 2238522 kohama, Kanagawa 2238522, Japan Tokyo Gakugei Univ, Dept Astron & Earth Sci, Koganei, Tokyo 1848501, JapanTokyo Gakugei Univ Koganei Tokyo Japan 1848501 anei, Tokyo 1848501, Japan
Titolo Testata:
RESOURCE GEOLOGY
, , anno: 1999,
pagine: 55 - 64
SICI:
1344-1698(1999):20<55:CVOPDA>2.0.ZU;2-U
Fonte:
ISI
Lingua:
ENG
Soggetto:
SOUTH TEXAS; SULFIDE; ISOTOPE; ORIGIN;
Keywords:
pyrite; uranium deposits; diagenesis; chemical composition of pyrite; minor elements in pyrite;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Physical, Chemical & Earth Sciences
Citazioni:
23
Recensione:
Indirizzi per estratti:
Indirizzo: Shikazono, N Keio Univ, Fac Sci & Technol, Dept Appl Chem, Kohoku Ku, Yokohama, Kanagawa 2238522, Japan Keio Univ Yokohama Kanagawa Japan 2238522 awa 2238522, Japan
Citazione:
N. Shikazono e M. Nakata, "Compositional variation of pyrite, diagenetic alteration and genesis of tone sandstone-type uranium deposits in Japan", RESOUR GEOL, 1999, pp. 55-64

Abstract

Pyrite from the Miocene sedimentary rocks in the Tone sandstone-type uranium mine area, Japan, has been investigated to elucidate diagenetic alteration processes and the chemical environment of uranium mineralization. Two types of pyrite can be distinguished; framboidal-type (Type A) and euhedral-subhedral-type (Type B). Electron microprobe analyses indicate that Type A pyrite contains small amounts of Mn, Ni and Co (usually less than 0.1 wt%), while Type B pyrite contains wide range of Mn, Ni and Co and sometimes appreciable amounts of Mn, Ni and Co up to 1.5 wt%, 0.2 wt% and 0.8 wt%, respectively. Abundance of Type A is smaller than Type B. Type A formed at earlier stage of diagenetic alteration process and in shallower parts in Tertiarysedimentary marine formation. Ni-rich and Go-rich pyrite has high delta(34)S values ranging from +7.0 to +29.0 parts per thousand. Electron microprobe analyses, microscopic observation, mineral paragenesisand delta(34)S demonstrate that Type A pyrite formed in oxidizing environment in which SO42- is predominant among aqueous sulfur species, while Type B in reducing environment in which H2S is predominant and trace elements(Mn, Ni, Co) incorporated into pyrite in late-stage reducing diagenetic environments.delta(34)S of Type B pyrite indicates that pyrite formed from evolved seawater trapped in the sediments. Uranium mineralization occurred at the margin of Type B pyrite grains in middle Midcene (ca. 15 Ma), which is close to the formation of the Type B pyrite. delta(18)O of calcite coexisting with Type B pyrite indicates that calcite formed from groundwater of meteoric water origin which has the chemical characteristic features similar to those of modern groundwater in the lower horizon of Tertiary sedimentary rocks. Itis inferred that the precipitation of the uranium minerals occurred at thetime changing from marine environment to terrestrial environment from the oxygenated groundwater mixed with evolved underlying reducing seawater by the reduction of U6+ to U4+ by the reductant such as organic matter, ferrousminerals and H2S in evolved seawater. Characteristic features of the Tone deposits are similar to those of Grants-type and Roll front-type, suggesting the similar genesis of the uranium mineralizations.

ASDD Area Sistemi Dipartimentali e Documentali, Università di Bologna, Catalogo delle riviste ed altri periodici
Documento generato il 30/11/20 alle ore 16:25:11