Petrogenesis and tectonic implications of the Fanpu diorite in the northern Qinling orogenic belt
The petrogenesis of the Fanpu diorite can provide new constraints on the activity and deep process of the Paleozoic intermediate magmatism in the North Qinling orogenic belt.Two samples from the Fanpu pluton are dated at 422.1±5.5 Ma and 424.2±5.2 Ma,respectively,indicating that they formed in the Late Silurian.176Hf/177Hf ratios of zircon grains of the Fanpu diorite range from 0.282 272 to 0.282 918,εHf(t)values are between-8.48 and 14.45,and TDM2 are between 1 938 Ma and 488 Ma.The Fanpu diorite belongs to the calc-alkaline series,which are enriched in silicon,alkali,calcium,and magnesium,with Mg# values ranging from 41.7 to 57.4.In the spider diagram of trace elements,the Fanpu diorite has shown the depletion of Nb,Ta and Ti.Total REE contents of the Fanpu diorite are between 117×10-6 and 171×10-6,and ratios of(La/Yb)N range from 6.71 to 18.1.The δEu values are between 0.82 and 0.95.Their REE distribution patterns are characterized by light REE enrichment and heavy REE depletion,without obvious negative Eu anomaly.Magma of the Fanpu diorite might originate from the lower crust and underwent crust-mantle interaction in an island arc tectonic environment,which was related to the northward subduction of the Shangdan Ocean.
Fanpu dioriteZircon U-Pb ageLate SilurianIsland arcNorth Qinling orogenic belt
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维普
