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Conditions for early cretaceous emerald formation at Dyakou, China / G. Xue in Economic geology, Vol. 105 N° 2 (Mars/Avril 2010) 

Public ISBD [article]  in Economic geology > Vol. 105 N° 2 (Mars/Avril 2010) . - pp. 339-349 Titre : Conditions for early cretaceous emerald formation at Dyakou, China : fluid inclusion, Ar-Ar, and stable isotope studies Type de document : texte imprimé Auteurs : G. Xue, Auteur ; D. Marshall, Auteur ; S. Zhang, Auteur Année de publication : 2011 Article en page(s) : pp. 339-349 Note générale : Econopmic geology Langues : Anglais (eng) Mots-clés : Emerald  formation  Fluid  inclusion  Isotope  China Index. décimale : 553 Géologie économique. Minérographie. Minéraux. Formation et gisements de minerais Résumé : The Dyakou emerald occurrence is located in Malipo County in the province of Yunnan, southern China. The occurrence lies in the northern part of the Laojunshan-Song Chay metamorphic core complex, which is exposed in an area of approximately 2,000 km2 and extends across the border between China and Vietnam. Emerald mineralization is hosted by pegmatite and associated quartz veins that intrude deformed Proterozoic biotite-muscovite granofels and schist. Hydrogen and oxygen isotope results from the emerald channel waters and emerald, respectively, are consistent with an igneous fluid source. The δ18O fractionation between emerald and quartz yields vein temperatures of 365° to 420°C. Fluid inclusions indicate that the emerald precipitated from saline brines ranging from almost pure water to 10.5 mass percent NaCl equiv. Fluid inclusion isochores intersected with δ18O data yield pressures changing along the geothermal gradient from 1,500 to 3,300 bars. Ar-Ar geochronology of biotite and muscovite from the emerald veins yields consistent ages of 124 ± 1 Ma. These constraints combined with field observations indicate that the Dyakou emerald deposit is consistent with the igneous-related model for emerald formation. DEWEY : 553 ISSN : 0361-0128 En ligne : http://econgeol.geoscienceworld.org/content/105/2/339.abstract [article] Conditions for early cretaceous emerald formation at Dyakou, China : fluid inclusion, Ar-Ar, and stable isotope studies [texte imprimé] / G. Xue, Auteur ; D. Marshall, Auteur ; S. Zhang, Auteur . - 2011 . - pp. 339-349. Econopmic geology Langues : Anglais (eng) in Economic geology > Vol. 105 N° 2 (Mars/Avril 2010) . - pp. 339-349 Mots-clés : Emerald  formation  Fluid  inclusion  Isotope  China Index. décimale : 553 Géologie économique. Minérographie. Minéraux. Formation et gisements de minerais Résumé : The Dyakou emerald occurrence is located in Malipo County in the province of Yunnan, southern China. The occurrence lies in the northern part of the Laojunshan-Song Chay metamorphic core complex, which is exposed in an area of approximately 2,000 km2 and extends across the border between China and Vietnam. Emerald mineralization is hosted by pegmatite and associated quartz veins that intrude deformed Proterozoic biotite-muscovite granofels and schist. Hydrogen and oxygen isotope results from the emerald channel waters and emerald, respectively, are consistent with an igneous fluid source. The δ18O fractionation between emerald and quartz yields vein temperatures of 365° to 420°C. Fluid inclusions indicate that the emerald precipitated from saline brines ranging from almost pure water to 10.5 mass percent NaCl equiv. Fluid inclusion isochores intersected with δ18O data yield pressures changing along the geothermal gradient from 1,500 to 3,300 bars. Ar-Ar geochronology of biotite and muscovite from the emerald veins yields consistent ages of 124 ± 1 Ma. These constraints combined with field observations indicate that the Dyakou emerald deposit is consistent with the igneous-related model for emerald formation. DEWEY : 553 ISSN : 0361-0128 En ligne : http://econgeol.geoscienceworld.org/content/105/2/339.abstract