Citation: | SUN Jian, SUN Dongliang. THE GEOCHEMICAL CHARACTERISTICS AND TECTONIC SIGNIFICANCE OF LA-ICP-MS ZIRCON U-PB DATING OF YAMATUO INTRUSIVE ROCKS, QINHAI PROVINCE[J]. Journal of Geomechanics, 2017, 23(4): 567-576. |
Yamatuo intrusive rocks, distributing in the northern margin of Qaidam basin, compose the east part of Tataleng River batholith. The lithology of these rocks is the combination of porphyritic-like syenogranite and porphyritic monzogranite. The phenocryst content in the rocks is 6~25% and its grain size is 1~5 cm, revealing rapakivi texture. The geochemical characteristics show that Eu is with obvious depleted characteristics reflecting the strong fractional crystallization of rocks which is very similar to crustal-derived granite (S). All the facts indicate the intrusive rocks are the partial melting of the crust, belonging to the mixture of crust-derived magmatite in post-collisional tectonic setting. The result analysis of LA-ICP-MS zircon U-Pb dating indicates that the rock mass was formed in early Silurian 429.9±1.4 Ma, being the signature of the end or near the end of the orogenic process in early Paleozoic This finding provides important chronological constraints for further study of the tectonic evolution of the northern margin of Qaidam orogenic belt.
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Tectonic location of Yamatuo intrusive rock
Distribution map of the sample collection position
NASC normalized REE pattern of Yamatuo intrusive rocks
Spider diagram of trace element ratio of Yamatuo intrusive rocks
Giant potash feldspar phenocryst in the rock
Fine-grained rims and chilled borders in the rock
Nbversus Y diagrams of Yamatuo intrusive rocks
Rbversus Nb+Y diagrams of Yamatuo intrusive rocks
CL Images of porphyritic biotite monzogranite zircons
Zircon U-Pb concordia diagram of Yamatuo intrusive rocks
Zircon U-Pb ages weighted graph of Yamatuo intrusive rocks