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通过对南岭中段骑田岭花岗岩基地质-岩石地球化学特征研究,判明了该岩基的侵位深度(5.5km)、围岩温度(196℃)及岩浆初始温度(950℃),建立起骑田岭花岗岩基的数学计算模型,计算得出:骑田岭花岗岩熔体侵位后,其初始温度降低至结晶温度所需的时间(Δtcol)为4.1Ma;由于结晶潜热释放而使结晶过程延长的时间(ΔtL)为2.6Ma;由于骑田岭花岗岩基放射性元素含量(U-15.3×10-6,Th-51.35×10-6,K2O-5.02%)是世界平均花岗岩放射性元素含量(U-5×10-6,Th-20×10-6,K2O-2.66%)的2~3倍,骑田岭花岗岩浆侵位后产生的放射成因热使结晶过程延长的时间(ΔtA)为35.4Ma,远长于世界平均花岗岩计算的ΔtA(2.93Ma)。因此,骑田岭花岗岩基的岩浆侵位-结晶固化时差(ΔtECTD)为42.1Ma,结合锆石U-Pb年龄值(161Ma),通过反演计算得出骑田岭花岗岩基侵位年龄值(tE)为203.1Ma,从而为骑田岭花岗岩基属于印支期侵位提供了重要的岩浆动力学佐证。
Through the study on the geo-lithogeochemical characteristics of Qitianling granite basement in the middle part of Nanling, the emplacement depth (5.5km), the surrounding rock temperature (196 ℃) and the initial magma temperature (950 ℃) have been determined and established The calculation model of Qiantangling granite base shows that the time required for the initial temperature to drop to the crystallization temperature (Δtcol) is 4.1Ma after the molten Qijianling granite invaded, and the crystallization process is released due to the release of latent heat of crystallization (ΔtL) is 2.6Ma. The radioactive element content of the Qitianling granite base (U-15.3 × 10-6, Th-51.35 × 10-6, K2O-5.02% -5 × 10-6, Th-20 × 10-6, K2O-2.66%). The time (ΔtA) for the prolongation of crystallization was 35.4 Ma, which is much longer than the calculated ΔtA (2.93Ma) of the world average granite. Therefore, the magmatic emplacement-crystallization solidification time difference (ΔtECTD) of Qitianling granite is 42.1Ma. Based on the zircon U-Pb age (161Ma), the emplacement age value of Qitianling granite base tE) was 203.1Ma, which provided important magmatism evidence for the Qilianling granitoids to belong to the Indosinian emplacement.