地质温度计在桂东南那卜韧性剪切带花岗质糜棱岩中的适用性  

Applicability of Geothermometer to Granitic Mylonites in Nabu Ductile Shear Zone,Southeast Guangxi

作　　者：辛良伟 李赛赛[1,2] 冯佐海[1,2] 刘兴源 吴江波 王秋宇 Xin Liangwei;Li Saisai;Feng Zuohai;Liu Xingyuan;Wu Jiangbo;Wang Qiuyu(Collaborative Innovation Center for Exploration of Nonferrous Metal Deposits and Efficient Utilization of Resources by the Province and Ministry,Guilin University of Technology,Guilin 541004,China;College of Earth Sciences,Guilin University of Technology,Guilin 541004,China)

机构地区：[1]有色金属矿产勘查与资源高效利用省部共建协同创新中心,桂林理工大学,广西桂林541004 [2]桂林理工大学地球科学学院,广西桂林541004

出　　处：《地球科学》2024年第6期1946-1965,共20页Earth Science

基　　金：广西自然科学基金资助项目(Nos.2020GXNSFAA297091,桂科AD19110121);国家自然科学基金资助项目(Nos.42262026,42072259)。

摘　　要：糜棱岩的变质变形温度测定对其变形演化过程和热年代学同位素定年结果解释具有重要的意义.本文仅讨论各地质温度计在那卜韧性剪切带中的适用性.利用糜棱岩中的矿物组合、矿物动态重结晶特征以及EBSD(electron back-scattered diffraction)石英轴组构等塑性变形特征,估算出那卜韧性剪切带的变质变形温度范围为400~550℃.在电子探针分析技术基础上,利用绿泥石成分地质温度计、白云母-绿泥石地质温度计以及白云母/黑云母Ti温度计对那卜韧性剪切带中的花岗质糜棱岩样品进行变质变形温度计算,获得相应的温度分别为305~325℃、390~500℃、395~492℃和473~565℃、431~574℃.通过对比分析发现,利用绿泥石成分地质温度计获得的结果明显低于利用塑性变形特征估算出的温度范围和其他温度计的计算结果,结合前人研究结果表明其仅适用于低温变质变形作用的温度计算;而另外3种温度计获得的结果在误差范围内均位于利用塑性变形特征估算出的温度范围内,表明其均适用于该剪切带的变质变形温度计算.其中白云母-绿泥石地质温度计适用于低温糜棱岩,白云母/黑云母Ti温度计适用于相对高温的糜棱岩.The measurement of metamorphic and deformation temperature of mylonites is of great significance for the interpretation of deformation evolution process and thermochronological isotope dating results.In this paper it only discusses the applicability of each geothermometers in the Nabu ductile shear zone.Using the plastic deformation characteristics,such as the mineral assemblage,dynamic recrystallization characteristics of minerals and EBSD(electron back-scattered diffraction)quartz caxis fabrics in mylonites,the metamorphic deformation temperature range of the Nabu ductile shear zone is estimated to be 400 to 550℃.Based on the electron probe microanalysis(EMPA),the chlorite compositional geothermometer,muscovite-chlorite geothermometer,Ti-in-muscovite and Ti-in-biotite geothermometers were applied to calculate the metamorphic deformation temperature of the granitic mylonite samples in the Nabu ductile shear zone.The corresponding temperatures are 305 to 325℃,390 to 500℃,395 to 492℃and 473 to 565℃,431 to 574℃.Through comparative analysis,it is found that the results obtained by using chlorite compositional geothermometer are obviously lower than the temperature range estimated by using plastic deformation characteristics and the results calculated by other geothermometers.Combined with the results of previous studies,the chlorite compositional geothermometer is only suitable for the temperature calculation of low temperature metamorphic deformation.The results obtained by the other three geothermometers are all within the error range of the temperature estimated by using the plastic deformation characteristics,indicating that they are suitable for the calculation of metamorphic deformation temperature of the Nabu ductile shear zone.Among them,the muscovite-chlorite geothermometer is suitable for low temperature mylonite,and Ti-in-muscovite and Ti-in-biotite geothermometers are suitable for relatively high temperature mylonite.

关 键 词：糜棱岩 韧性剪切带 地质温度计 变质变形温度 那卜镇 构造地质 

分 类 号：P588.3[天文地球—岩石学]