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文章通过对南岭东段寨背和陂头岩基地质-岩石地球化学特征研究,判明它们的侵位深度(7.5 km)、围岩温度(250℃)及岩浆初始温度(950℃),建立起寨背—陂头岩基的数学计算模型,并计算得出:寨背和陂头花岗岩熔体侵位后,其初始温度降低至结晶温度所需的时间(Δtcol)分别为4.04 Ma(寨背岩基)和3.97 Ma(陂头岩基);由于结晶潜热释放而使结晶过程延长的时间(ΔtL)为3.02 Ma,2.96 Ma;由于寨背和陂头花岗岩基放射性元素的质量分数高于世界平均花岗岩放射性元素含量(w(U)=5×10-6,w(Th)=20×10-6,w(K2O)=2.66%),寨背和陂头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)分别为14.3 Ma和5.16 Ma,远长于按世界平均花岗岩放射性元素质量分数计算得出的ΔtA(3.1 Ma和2.9 Ma)。寨背和陂头花岗岩基的侵位-结晶时差(ΔtECTD)为21.4 Ma和12.1 Ma,结合同位素年龄值(锆石U-Pb年龄及全岩Rb-Sr等时线年龄的平均值为173.8 Ma(寨背)和182.3 Ma(陂头)),通过反演计算得出寨背和陂头花岗岩基侵位年龄值(tE)分别为195.2 Ma和194.4 Ma,从而为寨背和陂头花岗岩基属于印支期侵位提供了重要的岩浆动力学佐证。
Based on the study of the geo-lithogeochemical characteristics of Zhaigou and Yuantou basement in the eastern section of Nanling, the emplacement depth (7.5 km), surrounding rock temperature (250 ℃) and initial magmatic temperature (950 ℃) are established. The calculation model of Zhaizhu-Quaitou rock foundation is calculated and the results show that the time required for the initial temperature to decrease to the crystallization temperature (Δtcol) after the melt emplacement of Zaigou and Quantou granites are respectively 4.04 Ma Backfill basalts) and 3.97 Ma (piedtou basement). The time (ΔtL) for the crystallization process due to the release of latent heat of crystallization was 3.02 Ma and 2.96 Ma. Because the radioactive elements in the Zaidou and Yuantou granites are higher than The average radioactivity of granite in the world (w (U) = 5 × 10-6, w (Th) = 20 × 10-6, w (K2O) = 2.66% The time (ΔtA) for the prolongation of the crystallization process by radiation generative heat is 14.3 Ma and 5.16 Ma, respectively, much longer than ΔtA (3.1 Ma and 2.9 Ma) as calculated from the radioactive elemental mass fraction of the world average granite. The emplacement-crystallization time difference (ΔtECTD) of Zhabei and Yuantou granites is 21.4 Ma and 12.1 Ma, respectively. The age of combined isotopes (zircon U-Pb ages and Rb-Sr isochron ages) is 173.8 Ma (Walled back) and 182.3 Ma (陂 head)). Based on the inversion results, the emplacement age values (tE) of Zhaigou and Yuantou granites are 195.2 Ma and 194.4 Ma, respectively, It belongs to the Indosinian emplacement and provides important magmatism evidence.