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SHRIMP U-Pb ages of zircons from dioritic gneiss in the Nyainqêntanglha Mountains ,Tibet
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2003
Year
Magmatic ProcessQuartz Dioritic OrthogneissVolcanologyEngineeringMagmatic Zircon.ion MicroprobePrecambrian GeologyChemistryEarth ScienceMesozoic TectonicsGeochronologyDioritic GneissMagmatismIgneous PetrogenesisGeologyShrimp U-pb AgesTectonicsNatural SciencesEvolutionary BiologyIon MicroprobeGeochemistryNyainqêntanglha MountainsPaleoecologyPetrologyMineral Geochemistry
Zircons from tonalitic and quartz dioritic orthogneisses in the Nyainqentanglha Mountains ,Ti-bet,were dated by ion microprobe(SHRIMP )and their origin was studied.In the Cathodoluminescence(CL)images the zircons extracted from the dioritic gneiss show good crystal morphology and clear oscilla-tory zoning,as is the case of magmatic zircon.Ion microprobe analyses revealed that the zircon from the orthogneiss has high Th /U ratios.Ion microprobe U-Pb dating of zircons from the tonalitic gneiss and quartz dioritic orthogneiss yielded statistically distinguishable 206 Pb / 238 U crystallization ages of 58.5±0.7Ma and63.5±0.8Ma ,respectively.The result suggests that the orthogneiss in the Nyainqentanglha Mountains may have crystallized during Andean-type Gangdise magmatism.