南岭寨背和陂头花岗岩基属印支期侵位的岩浆动力学证据及构造意义

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...

Magma-dynamic evidence for Indo-sinian cycle emplacement of the Zhaibei and Pitou granite batholith of Nanling range in south China and the tectonic implication

The geological-geochemical features of the Zhaibei and Pitou Granite Batholith reveal that the emplacement depth is 7.5km and temperature of the enclosing rock 250℃,the initial temperature of the magma 950℃.Based on the data mathematic model is established calculating that after emplacement the cooling period from the initial magma temperature to the crystallization is 4.04 Ma at Zhaibei and 3.97 Ma at Pitou;the prolongation period（ΔtL） caused by latent heat release 3.02 Ma and 2.96 Ma respectively.Since the radioactive element content of the Batholith,U=10.32×10-6,Th=46.9×10-6t,K2O=5.38%（Zhaibei）;U=6.28×10-6t,Th=29.7×10-6t,K2O=5.37%（Pitou） are as high as 2 times of those of the global granite average,U=5×10-6t,Th=20×10-6t,K2O=2.66%,the prolongation period（ΔtA） caused by radiogenic heat are 14.3 Ma and 5.16Ma,which are much longer than the global averageΔtA,3.1 Ma and 2.9Ma.Therefore,the time elapsed from emplacement to the end of crystallization（ΔtECTD） should be the sum ofΔtcol,ΔtL and ΔtA,21.4 Ma and 12.1 Ma.In combination with isotopic ages of 173.8 Ma and 182.3 Ma which represent the crystallization age,the emplacement ages at Zhaibei and Pitou are estimated to be 195.2 Ma and 194.4 Ma.These suggest that the emplacement of the Zhaibei and Pitou granite Batholith took place in the Indo-Sinian Period.