花岗岩浆侵位与结晶固化时差的研究与构造意义:以南岭骑田岭花岗岩基为例

J4 ›› 2010, Vol. 16 ›› Issue (1): 103-118.

花岗岩浆侵位与结晶固化时差的研究与构造意义:以南岭骑田岭花岗岩基为例

章邦桐，吴俊奇，凌洪飞，陈培荣

内生金属矿床成矿机制研究国家重点实验室(南京大学), 南京大学地球科学与工程学院，南京 210093

收稿日期:2010-03-20 修回日期:2010-03-20 出版日期:2010-03-20 发布日期:2010-05-25

On the Time Elapsed from Magma Emplacement to Crystallization-Solidification of Granites and Its Tectonic Implication: Taking the Qitianling Granite Batholith of Nanling Range in Sourth China as an Example

ZHANG Bang-tong，WU Jun-qi，LING Hong-fei，CHEN Pei-rong

State Key Laboratory for Mineral Deposits Research, School of Earth Sciences and Engineering, Nanjing University, Nanjing 210093, China

Received:2010-03-20 Revised:2010-03-20 Online:2010-03-20 Published:2010-05-25

摘要/Abstract

摘要：

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（5.5 km）、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（Δt col）为4.1 Ma；由于结晶潜热释放而使结晶过程延长的时间（Δt L）为2.6 Ma；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（Δt A）为35.4 Ma，远长于世界平均花岗岩计算的Δt A（2.93 Ma）。因此，骑田岭花岗岩基的岩浆侵位- 结晶固化时差（Δt ECTD）为42.1 Ma，结合锆石U-Pb 年龄值（161 Ma），通过反演计算得出骑田岭花岗岩基侵位年龄值（t E ）为203.1 Ma，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。

关键词: 骑田岭花岗岩基；侵位年龄；侵位-结晶时差；印支造山运动；岩浆动力学证据

Abstract:

From the geological-geochemical features of the Qitainling granite batholith, the depth of emplacement (5.5 km ),temperature of country rocks (196 ℃) and initial temperature of granite melt (950 ℃) during its emplacement are obtained.With these parameters a mathematic model calculating the emplacement age of the Qitainling granite batholith is established in this paper. Model calculation results suggest that the cooling time (Δt col ) for the Qitainling granite batholith from its initial temperature to crystallization temperature was 4.1 Ma, and the prolongation time (Δt L ) caused by latent heat generated from crystallization was 2.6 Ma. Since the radioactive elements of the Qitainling granite batholith (U，15.3×10-6；Th， 51.35×10-6；K2O， 5.02 % ) are as high as 2~3 times of those of the world average granite (U，5×10-6；Th， 20×10-6；K2O， 2.66 %) , the prolongation time (Δt A ) caused by radiogenic heat from the decay of the radioactive elements was 35.4 Ma , which is much longer than the Δt A value calculated for the world average granite (2.93 Ma). Therefore, the time elapsed from the magma emplacement to the crystallization-solidification (Δt ECTD), which should be the sum of Δt col , Δt L, and Δt A, was 42.1 Ma for the Qitainling granite batholith. In combination with zircon U-Pb age of the granite (161 Ma) representing the crystallization age, the emplacement age of the Qitainling granite batholith is estimated to be 203.1 Ma. This suggests that the emplacement of the Qitainling granite magma was in the Indo-Sinian Period.

Key words: Qitainling granite batholith, emplacement age, emplacement-crystallization time difference, Indo-Sinian orogeny;magma-dynamic evidence

章邦桐，吴俊奇，凌洪飞，陈培荣. 花岗岩浆侵位与结晶固化时差的研究与构造意义:以南岭骑田岭花岗岩基为例[J]. J4, 2010, 16(1): 103-118.

ZHANG Bang-tong，WU Jun-qi，LING Hong-fei，CHEN Pei-rong. On the Time Elapsed from Magma Emplacement to Crystallization-Solidification of Granites and Its Tectonic Implication: Taking the Qitianling Granite Batholith of Nanling Range in Sourth China as an Example[J]. J4, 2010, 16(1): 103-118.