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001-es BibID:BIBFORM073874
Első szerző:Czuppon György
Cím:Stable (H, O, C) and noble-gas (He and Ar) isotopic compositions from calcite and fluorite in the Speewah Dome, Kimberley Region, Western Australia: implications for the conditions of crystallization and evidence for the influence of crustal-mantle fluid mixing / Gy. Czuppon, R. R. Ramsay, I. Özgenc, A. Demény, L. G. Gwalani, K. Rogers, A. Eves, L. Papp, L. Palcsu, M. Berkesi, P. J. Downes
Dátum:2014
ISSN:0930-0708 1438-1168
Megjegyzések:In this study, the C-O-isotopic data from calcite at Yungul and Wilmott (Speewah. Western-Australia) are integratedwithmicrothermometry,H2O-,CO2-contentandH-HeAr-isotopic data from fluid inclusions in genetically related calcite and fluorite to map the origin and crystallization paths of the fluids. In addition to the hydrogen isotopic compositions of fluid inclusions in fluorite, oxygen isotopic compositionswerealsodeterminedbycavityring-downspectroscopy. The geochemical data suggest mixing of a CO2-dominatedmantle fluid and a H2O-domintated crustal brine. The fluid produced by this mixing is characterized by radiogenic (crustal-like) 3He/4He ratios, crustal-like ?D values, relatively high salinity (19?24wt.% NaCl eq.), moderate homogenization temperatures (150?450 ?C) and mantle-like CO2/3He ratios. Moreover, the large isotopic and elemental variations found in calcite indicate that its formation was accompanied byanextensivedegassing(opensystem)leadingtoadecrease in ?D and an increase in the CO2/3He values relative to the starting fluid composition. This degassing is consistent with the fluidal- and breccia-like texture of calcite observed in the field.Incontrast,thefluoritewhichhascoarse-grainedbanded to vughy textures formed in a passive aqueous system. Apparently the fluid that formed the fluorite has the same originasthecalcite,butthehigherwatercontentandthemore radiogenic 3He/4He ratios reflect a greater involvement of crustal fluids. The historical description of the calcite-fluorite system in the Speewah area as "carbonatite" is now considered inappropriate because there is no evidence that crystallization is dominated by magmatic processes.
Tárgyszavak:Természettudományok Fizikai tudományok idegen nyelvű folyóiratközlemény külföldi lapban
age dating
helium-3
helium-4
isotope measurements
methods and equipment
noble gas mass spectrometry
palaeoclimate reconstruction
tritium
water
Megjelenés:Mineralogy and Petrology. - 108 : 6 (2014), p. 759-775. -
További szerzők:Ramsay, R. R. Özgenc I. Demény András (1944-) (fizikus) Gwalani, L. G. Rogers, K. Eves, A. Papp László (1983-) (környezetkutató fizikus geográfus) Palcsu László (1975-) (fizikus) Berkesi M. Downes, P. J.
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