Water-Flux Melting of Amphibolite in Paleozoic Leucogranite from the North Qinling, Central China: I

• 作 者: Jiangbo Wang Tong Li Yan Zhang Weihong Li
• 机 构: State Key Laboratory of Continental Dynamics, Department of Geology, Northwest University, Xi’an 710
• 出 处: 地球科学学刊（英文版）
• 发表日期: 2020年5期
• 关键词: leucogranite North Qinling Late Paleozoic crustal differentiation zircon Lu-Hf i

Paleozoic granites can provide important insights of crustal differentiation and collision pro-cess 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 moder-ate 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 εNd(t) (-10.4) and εHf(t) (-9.35 to -0.25) values and ancient TDM2 ages (1.2 to 1.7 Ga), suggesting the leucogranite are derived from an-cient 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 (～700 ℃) 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 post-collision setting may be a potential model for the genesis of granites in collisional orogenic belt.