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Titolo:
Trace metal-rich Quaternary hydrothermal manganese oxide and barite deposit, Milos Island, Greece
Autore:
Hein, JR; Stamatakis, MG; Dowling, JS;
Indirizzi:
US Geol Survey, Coastal & Marine Geol, Menlo Park, CA 94025 USA US Geol Survey Menlo Park CA USA 94025 ine Geol, Menlo Park, CA 94025 USA Natl Univ Athens, Dept Geol, Athens, Greece Natl Univ Athens Athens Greece l Univ Athens, Dept Geol, Athens, Greece
Titolo Testata:
TRANSACTIONS OF THE INSTITUTION OF MINING AND METALLURGY SECTION B-APPLIEDEARTH SCIENCE
, volume: 109, anno: 2000,
pagine: B67 - B76
SICI:
0371-7453(200005/08)109:<B67:TMQHMO>2.0.ZU;2-B
Fonte:
ISI
Lingua:
ENG
Soggetto:
ELEMENTS; ARC;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Physical, Chemical & Earth Sciences
Citazioni:
31
Recensione:
Indirizzi per estratti:
Indirizzo: Hein, JR US Geol Survey, Coastal & Marine Geol, 345 Middlefield Rd,MS 999,Menlo Park, CA 94025 USA US Geol Survey 345 Middlefield Rd,MS 999 Menlo Park CA USA 94025
Citazione:
J.R. Hein et al., "Trace metal-rich Quaternary hydrothermal manganese oxide and barite deposit, Milos Island, Greece", T I MIN M-B, 109, 2000, pp. B67-B76

Abstract

SynopsisThe Cape Vani Mn oxide and barite deposit on Miles Island offers an excellent opportunity to study the three-dimensional characteristics of a shallow-water hydrothermal system. Miles Island is part of the active Aegean volcanic are. A 1 km long basin located between two dacitic domes in northwest Miles is filled with a 35-50 m thick section of Quaternary volcaniclastic and pyroclastic rocks capped by reef limestone that were hydrothermally mineralized by Mn oxides and barite. Manganese occurs as thin layers, as cement of sandstone and as metasomatic replacement of the limestone, including abundant fossil shells. Manganese minerals include chiefly delta -MnO2, pyrolusite and ramsdellite. The MnO contents for single beds range up to 60%. TheMn oxide deposits are rich in Pb (to 3.4%), BaO (to 3.1%), Zn (to 0.8%), As (to 0.3%), Sb (to 0.2%) and Ag (to 10 ppm). Strontium isotopic compositions of the Mn oxide deposits and sulphur isotopic compositions of the associated barite show that the mineralizing fluids were predominantly sea water. The Mn oxide deposit formed in close geographical proximity to sulphide-sulphate-Au-Ag deposits and the two deposit types probably formed from the same hydrothermal system. Precipitation of Mn oxide took place at shallow burial depths and was promoted by the mixing of modified sea water (hydrothermal fluid) from which the sulphides precipitated at depth and sea water thatpenetrated along faults and fractures in the Cape Vani volcaniclastic and tuff deposits. The hydrothermal fluid was formed from predominantly sea water that was enriched in metals leached from the basement and overlying volcanogenic rocks. The hydrothermal fluids were driven by convection sustainedby heat from cooling magma chambers. Barite was deposited throughout the time of Mn oxide mineralization, which occurred in at least two episodes. Manganese mineralization occurred by both focused and diffuse flow, the fluids mineralizing the beds of greatest porosity and filling dilatational fractures along with barite.

ASDD Area Sistemi Dipartimentali e Documentali, Università di Bologna, Catalogo delle riviste ed altri periodici
Documento generato il 25/10/20 alle ore 11:25:35