• journal_title：Economic Geology
• Contributor：G. Xue ; D. Marshall ; S. Zhang ; T. D. Ullrich ; T. Bishop ; L. A. Groat ; D. J. Thorkelson ; G. Giuliani ; A. E. Fallick
• Publisher：Society of Economic Geologists
• Date：2010-
• Format：text/html
• Language：en
• Identifier：10.2113/gsecongeo.105.2.339
• journal_abbrev：Economic Geology
• issn：0361-0128
• volume：105
• issue：2
• firstpage：339
• section：Articles

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.