吉林辉南幔源橄榄岩流变学与组构特征及其动力学启示
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国家自然科学基金项目(面上项目,重点项目,重大项目)


Rehology and Fabric Characteristics of Mantle Xenoliths in Huinan,Jinlin Province and Its Dynamic Implications
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    摘要:

    吉林辉南位于华北克拉通(NCC)东北部边缘,新生代玄武岩中含有大量的新鲜幔源包体。包体类型主要为尖晶石二辉橄榄岩。包体矿物化学成分反映的平衡温度为:982-1085 ℃。氧化缀饰方法揭示了样品中橄榄石的显微特征,表明包体存在形态各异的位错样式:位错壁、亚颗粒、位错环、位错网等,指示了样品可能经历了以位错蠕变为主的塑性变形。依据亚颗粒大小推算上地幔差异流动应力为:21.3-36.5 MPa。利用电子背散射衍射(EBSD)技术测定橄榄石的晶格学优选方位(LPOs),反映了本区总体上A型组构的特征。其中,LQLW08-18温度和组构类型及地震波各向异性上的差异暗示了温度差异可能产生更倾向于作用在[100]晶轴上的一个效应。橄榄石、橄榄岩地震波各向异性与橄榄岩中矿物含量的研究,定量的说明了斜方辉石的效果是降低总体的各向异性。橄榄岩包体的各种流变学参数和组构特征既为该区上地幔进一步研究提供了基础信息和约束,也说明了该区上地幔整体上的不均一性和为该区的破坏动力学机制可能主要为地幔置换作用(化学侵蚀作用)提供了流变学条件。

    Abstract:

    There is a large numbers of mantle xenoliths derived from the Cenozoic basalt in Huinan, Jilin province. The mantle xenoliths are dominated by spinel lherzolite. Equilibrium temperature calculated by the mineral chemical compositions show that temperature is within the range of 982-1085 ℃. As revealed by the oxidation decoration technique, the samples have undergone dislocation creep dominated plastic deformation, resulting in different kinds of the dislocation structures. By using the size of subgrain, the differential stress of olivine is estimated to be in the range of 21.3-36.5 MPa. The LPOs of olivine, which is measured by the EBSD technique,show A-type olivine fabrics as a whole. The variation of temperature and fabric and seismic anisotropy of LQLW08-18 suggest that the temperature may have a effect in preference to the [100] crystal axis. According to the study of olivine and peridotite anisotropy and the mineral compositions in the peridotite, the orthopyroxene can reduce the overall effect of the anisotropy. Different kinds of rheological parameters and fabrics characteristics not only provide basic information and restrictions for the further study of the upper mantle but also show the mantle heterogeneity and the replacement (chemical erosion) may be the main dynamic mechanism of destruction in this area.

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干微,金振民,王根厚,徐海军.2011.吉林辉南幔源橄榄岩流变学与组构特征及其动力学启示[J].地质学报,85(4):491-504.
GanWei, JinZhenmin, WangGenhou, XuHaijun.2011. Rehology and Fabric Characteristics of Mantle Xenoliths in Huinan,Jinlin Province and Its Dynamic Implications[J]. Acta Geologica Sinica,85(4):491-504.

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  • 收稿日期:2010-10-27
  • 最后修改日期:2011-01-08
  • 录用日期:2011-01-11
  • 在线发布日期: 2011-04-01