Geochemical Character and Tectonic Significance of the Qinling Dabu Granite Body in the Eastern Section of Western Qinling Mountains

After carrying out the detailed study on the petrology, isotope age, geochemistry of the Dabu granite batholithin Southeast Tianshui of Western Qinling Mountains, the original Dabugranite batholith has been further divided into Caledonian Baihua granite body and Indosinia Dabugranite body. The Baihua body has the character of I-type granite, which was formed in island-arc tectonic environment. The Dabu body is characterized by high AI₂O₃(with an average of 73.71%) and K₂O+Na₂O(8.50%~9.19%) contents, as well as low Fe₂O₃+FeO and MgO contents, which belong to peraluminous rocks and calc-alkaline-alkaline series. ∑REE values range from 183.27×10^-6 to 267.05×10^-6, with enriched LREE and obvious negative Eu anomaly (δEu=0.27~0.53). The (⁸⁷Sr/⁸⁶Sr)₀ values vary from 0.706 3 to 0.707 7, the δ¹⁸O values range from +9.12% to +9.86‰, showing the features of crust-derived granite and S-type granite, and suggesting that these granites were formed in post-collision tectonic environment and might be the products of continental uplift during the period of post-orogenics.