The Zircon U-Pb dating and Geologic Significance of Granite xenolith in alkalic-rich porphyry from Liuhe,Yunnan
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    Abstract:

    There are a series of Cenozoic alkali-rich porphyries along Jinshajiang -Ailaoshan fracture belt in western Yunnan province. Granite xenoliths ,which are paragenesis with mafic-ultramafic deep xenoliths, have been discovered from Liuhe alkali-rich porphyries.CL imaging LA-ICP-MS U-Pb dating and trace element analysis were carried out for the zircon from granite xenoliths. Studies show that the zircons have three types: magmatic zircons, magmatic zircons with old cores and new growth zones and metamorphic zircons.The new growth zones of magmatic zircons shows that average-weighted age is 39.2±2Ma,which is the petrogenic age of granite xenoliths. And the 39.2±2Ma is concordant to age of alkali-rich porphyries The old zones shows that average-weighted age are 828.1±7.1Ma,which is the age of basal rock. The age of metamorphic zircons is 108.4±4.4Ma, which stands for the mineral crystalline age of mantle fluid metasoatism. 108.4±4.4Ma coincides with age of amphibole in amphiboled flogopite garnet bistagite(102.87±1.19Ma)It is indicated that mantle fluid metasoatism continued cross cretaceous for a long time.Combinating with studies of petrography, it exhibits that the granite xenoliths were melted when it were captured. Presently,we calculate that the genesis of granite xenoliths is strongly linked to part melting of crust caused by mantle upwelling and contamination of mantle and crust fluid.

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zhaofufeng.2011. The Zircon U-Pb dating and Geologic Significance of Granite xenolith in alkalic-rich porphyry from Liuhe, Yunnan[J]. Acta Geologica Sinica,85(10):1574-1584

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History
  • Received:April 22,2011
  • Revised:July 11,2011
  • Adopted:July 25,2011
  • Online: September 28,2011
  • Published: