Study of Tectonic Environment and U-Pb Dating of Zircons from the Mengxi Plagioclase Granite Porphyry
详细信息
- 责任者：Wang Dequan (Chang’an University ; Xi’an 710054 ; China) ; Liu Jianchao
- 刊名：Journal of Mineralogy and Petrology
- 出版年：2013
- 卷期：33(3)
- 页码：p.63-69
- issnNo：ISSN1001-6872
- isbnNo：CN51-1143/TD
摘要
Copper mineralization in Mengxi plagioclase granite porphyry,which intruded the Huangcaopo Group of Mid-late Ordovician,occurred in the east Qiongheba multi-metal deposits area of East Junggar.Analysis showed that the ratio of K2O ranges from 1.59%to 5.06%,belonging to calc-alkaline to high-K calc-alkaline series.Also,the average value of A/CNK is 1.22,the ratio ofΣREE ranges from 29.99×10-6 to 90.99×10-6 with an average value of 62.00×10-6,the ratio of Ba/Th ranges from 140.19to 629.74with an average value of 395.72,suggesting that the fluids in subduction zones is significant to magma source.The ratio of(La/Yb)N ranges from 1.46to 6.56(average value 4.69)revealed that the fractionation of light and heavy rare earth was not obvious.The ratio ofδEu ranges from 0.77to 1.13(average value 0.99)demonstrated that the abnormality of Eu is weak.The magma was the mixture of mantle material and upper crust sediment formed through subduction.Cathodoluminescence image showed that zircons were colorless,transparent,crack free,with well developed magma concussion rhythm annulus and core.Through LA-ICP-MS U-Pb isotopic dating,plagioclase granite porphyry was formed in410Ma±11Ma and the age of single grain zircon is 410Ma±16Ma,indicating that the Mengxi granite porphyry formed in late Silurian.