首页> 中文期刊> 《高校地质学报》 >燕山早期花岗岩基印支期侵位的岩浆动力学证据及构造意义:基于南岭8个岩体侵位年龄计算结果

燕山早期花岗岩基印支期侵位的岩浆动力学证据及构造意义:基于南岭8个岩体侵位年龄计算结果

         

摘要

根据各花岗岩体地质构造特征、有关的热物理参数及主体花岗岩的放射性元素含量,采用简化的立方体数学模型计算得出:南岭地区8个花岗岩基侵位后,其初始温度降低至结晶温度所需的时间(Δtcol)为3.9(金鸡岭)~5.5 Ma(九峰);由于结晶潜热释放而使结晶过程延长的时间(ΔtL)为2.6~3.5 Ma;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5.2(陂头)~45.1 Ma(姑婆山)。南岭地区8个燕山早期花岗岩基的侵位-结晶时差(△tECTD)为12.1(陂头)~52.2 Ma(姑婆山),结合锆石U-Pb年龄通过反演计算得出其侵位年龄(tE )为194.4(陂头)~219.3 Ma(九峰)。这为南岭燕山早期花岗岩基属于印支期侵位提供了重要的岩浆动力学佐证,揭示出近东西向展布的南岭晚中生代造山带具有印支期构造格架(以侵位年龄为代表)和燕山早期花岗岩(以锆石U-Pb年龄为代表)的双重特征。%Based on the geological-tectonic features,the related thermophysical parameters and the radioactive element concentrations for each granite batholith, the simplified cubic mathematic model calculation results suggest that the cooling time from initilal temperature to crystallization temperature (Δtcol) for the 8 Early Yanshanian batholiths in Nanling (NR) Rang were 3.9 Ma(Jingjiling batholith)~5.5 Ma (Jiufeng batholith), the prolongation time caused by latent heat generated from crystallization (ΔtL) were 2.6~3.5 Ma and the prolongation time caused by radiogenic heat from decay of the radioactive elements (ΔtA) were 5.2 Ma (Pitou batholith)~45.1 Ma (Guposhan batholith). The time difference elapsed from the magma emplacement to the crystallization (△tECTD) were12.1 Ma (Pitou batholith)~52.2 Ma (Guposhan batholith)for the 8 Early Yanshanian batholiths in Nanling Rang and in combination with the zircon U-Pb ages of these granitoids and inversion calculation, the emplacement ages were 194.4 Ma (Pitou batholith)~219.3 Ma (Jiufeng batholith). These data provide important magma-dynamic evidence for the Indosinian emplacement of the Early Yanshanian batholiths in Nanling Rang and display the double magmatic-tectonic features in NR i.e., the E-W trending Indosinian tectonic framework( represented by tE ) and the Early Yanshan granite batholiths(represented by tC).

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