Conditions for Early Cretaceous Emerald Formation at Dyakou, China: Fluid Inclusion, Ar-Ar, and Stable Isotope Studies


Back to previous page
Authors: Xue, G; Marshall, D; Zhang, S; Ullrich, TD; Bishop, T; Groat, LA; Thorkelson, DJ; Giuliani, G; Fallick, AE
Year: 2010
Journal: Econ. Geol. 105: 339-349   Article Link (DOI)
Title: Conditions for Early Cretaceous Emerald Formation at Dyakou, China: Fluid Inclusion, Ar-Ar, and Stable Isotope Studies
Abstract: 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 km(2) 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 delta(18)O fractionation between emerald and quartz yields vein temperatures of 365 to 420 degrees 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 delta(18)O 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.
Back to previous page
 


Departmental members may update their publication list.