金红石中锆含量温度计及其微量元素地球化学特征——来自徐淮地区中生代侵入杂岩中榴辉岩类包体的信息

Zr-in-rutile thermometrv and eeochemical characteristics of trace element in rutile from eclogite inclusions of Mesozoic intrusive complexes in Xuzhou-Huainian area,

zack et al.(2004a)、Watson et al.(2006)以及Tomkins et al.(2007)(在2GPa条件下)的金红石中锆含量温度计计算结果显示,徐淮地区中生代侵入杂岩所含榴辉岩类包体所经历的榴辉岩相变质的温度范围分别为776～1099℃(平均898℃)、663～923℃(平均750℃)和714～981℃(平均804℃),这些温度结果可能并非榴辉岩相峰期变质温度;其角闪岩相退变质作用过程中保存的温度范围分别为555～777℃(平均697℃)、541～663℃(平均617℃)和588～714℃(平均667℃),这些结果不能代表角闪岩相退变质再平衡后的温度,而只能代表角闪岩相退变质作用过程中某一阶段的温度。微量元素地球化学特征研究表明,榴辉岩类包体所含金红石中的某些微量元素(如Nb、Ta、Cr、Fe、V等)含量与其原岩有继承和对应关系,其原岩主要为镁铁质岩石;榴辉岩类包体与其寄主岩石中部分高价态/高场强元素(HFSE)呈相互消长的关系。榴辉岩的形成与扬子地块和华北地块之间的俯冲-碰撞作用有关。

The calcutate results of temperature to eclogite inclusions from Mesozoic intrusive complexes in Xuzhou-Huainian area, China make use of zircon-m-rutile thermometry of Zack et al. (2004a), Watson el at. (2006) and Tomkins et al. (2007) (under 2GPa) indicate that it Underwent metamorphic temperature of eclogite facies range from 776 to 1099 degrees C (average 898 degrees C), from 663 to 923 degrees C average 750 degrees C) and from 714 to 981 degrees C (average 804 degrees C), respectively. These calculate results of temperature may be not peak metamorphic temperature of eclogite facies; and the temperature was kept in the course of the amphibolite facies retrogressive metamorphism are 555 similar to 777 degrees C ( average 697 degrees C) 541 similar to 663 degrees C ( average 617 degrees C) and 588 similar to 714 degrees C ( average 667 degrees C) respectively. The results do not represent the equilibrium temperature after amphibolite facies retrogressive metamorphism, but represent certain temperature in the course of the amphibolite facies retrogressive metamorphism. The research on geochemical characteristics of trace element in rutile from eclogite inclusions shows that the components of some trace elements(c. g. Nb,Ta,Cr,Fe,V,etc.)inherited the original matter which dominant are malic rock, which high electrovalency element or/and high field strength element emerge the decrease and increase between eclogite inclusions and its host magmatic complex. The eclogite was resulted from the subduction-collision action between the Yangtze block and the North China block.