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Titolo:
EXTREME BOILING MODEL FOR VARIABLE SALINITY OF THE HOKKO LOW-SULFIDATION EPITHERMAL AU PROSPECT, SOUTHWESTERN HOKKAIDO, JAPAN
Autore:
SCOTT AM; WATANABE Y;
Indirizzi:
GEOL SURVEY JAPAN,MINERAL & FUEL RESOURCES DEPT,1-1-3 HIGASHI TSUKUBAIBARAKI 3058567 JAPAN GEOL SURVEY JAPAN,MINERAL & FUEL RESOURCES DEPT TSUKUBA IBARAKI 3058567 JAPAN
Titolo Testata:
Mineralium Deposita
fascicolo: 6, volume: 33, anno: 1998,
pagine: 568 - 578
SICI:
0026-4598(1998)33:6<568:EBMFVS>2.0.ZU;2-O
Fonte:
ISI
Lingua:
ENG
Soggetto:
WAIOTAPU GEOTHERMAL SYSTEM; FLUID-INCLUSION; NEW-ZEALAND; FRESNILLO DISTRICT; GOLD; MEXICO; MINERALIZATION; EVOLUTION; MINE; MINERALOGY;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Science Citation Index Expanded
Science Citation Index Expanded
Citazioni:
34
Recensione:
Indirizzi per estratti:
Citazione:
A.M. Scott e Y. Watanabe, "EXTREME BOILING MODEL FOR VARIABLE SALINITY OF THE HOKKO LOW-SULFIDATION EPITHERMAL AU PROSPECT, SOUTHWESTERN HOKKAIDO, JAPAN", Mineralium Deposita, 33(6), 1998, pp. 568-578

Abstract

The Hokko prospect is located in the Minamikayabe area southwestern Hokkaido, Japan, where gold-bearing quartz veins of Pliocene age are exposed at the surface. The alteration mineral assemblage is typical of low-sulfidation epithermal systems, with the quartz veins associated with adularia alteration overprinted on Late Miocene propylitic alteration. Fluid inclusion studies of the vein quartz reveal mean homogenization temperatures of approximately 220 degrees C, and the co-existenceof low-salinity (<2 wt.% NaCl equivalent) and moderate salinity (2 to12 wt.% NaCl equivalent) fluid inclusions within the same veins. The moderate salinity fluid inclusions (2-12 wt.% NaCl equivalent) typically have relatively low homogenization temperatures between 150 degreesto 200 degrees C. The results obtained from stable isotope analysis of delta(18)O in quartz vein material showed a gradual decrease in delta(18)O signatures with increasing depth. The majority of the samples have calculated fluid source signatures (delta(18)O(H2O)) between -8.0 and -10.0 parts per thousand, but there is a significant change in thecomposition above 185 m drill depth. The shallower samples in particular show a wide range of oxygen isotope signatures that are associatedwith the moderate salinity fluid inclusions. We interpret that low-salinity inclusions within the Hokko system represent the composition ofthe liquid phase of the fluid, before boiling, and that the moderate-salinity inclusions are representative of the residual liquid phase, after extensive non-adiabatic boiling and vapor loss in an open system. This mechanism resulted in the entrapment of fluids with variable salinities at the same time, and in close proximity to each other. This is also reflected in the delta(18)O(H2O) values which become more variable and heavier where the moderate-salinity inclusions occur. Deposition of ore minerals within the Hokko vein system also occurred at this time as a result of boiling and gas loss.

ASDD Area Sistemi Dipartimentali e Documentali, Università di Bologna, Catalogo delle riviste ed altri periodici
Documento generato il 14/07/20 alle ore 06:56:22