Paleozoic granites can provide important insights of crustal differentiation and collision process of the North Qinling terrane. The Dafanggou leucogranites that intruded in the Qinling Complex is a Paleozoic granite with zircon U-Pb age of 404±6.4 Ma (MSWD=0.13, n=9). The leucogranites display moderate SiO₂ (68.4 wt.% to 71.7 wt.%) content and high Na₂O/K₂O (1.07 to 2.74) and Sr/Y (42 to 65) ratios, and low A/CNK (1.04 to 1.08) and Rb/Sr (0.09 to 0.16) ratios. Combined with negative ε_Nd(t) (−10.4) and ε_Hf(t) (− 9.35 to −0.25) values and ancient T_DM2 ages (1.2 to 1.7 Ga), suggesting the leucogranite are derived from ancient amphibolitic crust in the Qinling Group. In addition, the absence of coeval mafic igneous rocks or mafic enclaves occurred in the Dafanggou pluton and the low T_Zrn (∼700 °C) of leucogranites preclude that the leucogranites derived from high temperature dehydration melting of amphibolite. Thus, we propose that the occurrence of the Dafanggou leucogranite indicates that water-flux melting of middle-lower crust in postcollision setting may be a potential model for the genesis of granites in collisional orogenic belt.

古生代花岗岩可以为北秦岭地壳的地壳分异和碰撞过程提供重要的见识。侵入秦岭综合体的大方沟白云岩是古生代花岗岩，锆石U-Pb年龄为404±6.4 Ma（MSWD = 0.13，n = 9）。无色花岗岩显示出中等的SiO ₂（68.4 wt。％至71.7 wt。％）含量和高的Na ₂ O / K ₂ O（1.07至2.74）和Sr / Y（42至65）比，以及低的A / CNK（1.04）至1.08）和Rb / Sr（0.09至0.16）比。具有负组合ε_钕（吨）（-10.4）和ε_的Hf（吨（ - 9.35 -0.25）值和古）Ť _DM2年龄（1.2到1.7 Ga）表明白云石是秦岭组的古代两栖类地壳。此外，在大房沟岩体中没有近代镁铁质火成岩或镁铁质飞地，并且白云母的低T _Zrn（〜700°C）排除了角闪石高温脱水融化产生的白云母。因此，我们认为大方沟白云石的发生表明碰撞后环境中下地壳的水流融化可能是碰撞造山带花岗岩成因的潜在模型。