U-Pb SHRIMP Dating of Zircon from Quartz Veins of the Yangshan Gold Deposit in Gansu Province and Its Geological Significance

(整期优先)网络出版时间:2004-02-12
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TheYangshangolddepositisasuper-largefine-graineddisseminatedgolddepositlocatedinsouthernGansuProvince.ItsmetallogenicagehasbeendeterminedbyusingthecathodoluminescenceimageandionprobeU-Pbdatingtechniques.Itisfoundthatzirconsfromquartzveinletofthefine-graineddisseminatedgoldoreshowcharactersofmagmaticoriginwithprismidiomorphism,oscillatoryzoninganddominantTh/Uratiosof0.5-1.5.Threemainpopulationsofzirconsareobtained,givingaverage206pb/238Uagesof197.6±1.7Ma,126.9±3.2Maand51.2±l.3Marespectively.ThefirstagecorrespondstotheK-Arageoftheplagiogranitedike,whilethelattertwoagesindicatethatburiedCretaceousandTertiaryintrusivesexistintheorefield,suggestingthattheYangshangolddepositwasgeneticallyrelatedtothethreemagmatichydrothermalactivities.Bycontrast,zirconsfromcoarsegold-bearingquartzveinintheminingareaaremucholderthanthehostrock,indicatingthattheveinwasformedearlierandwasnotcontaminatedbylatermagmaticfluids.ItisconcludedthatthecouplingofmultiperiodichydrothermalactivitiesintheminingareahascontributedalottomineralizationoftheYangshangolddeposit.