激光显微探针^(40)Ar-^(39)Ar定年技术——大别山朱家冲榴闪岩年代学研究  

^(40)Ar-^(39)Ar Ultra-Violet Laser Ablation Microprobe(UVLAMP):Timing of Amphibolite-Facies Retrograde Metamorphism of Zhujiachong UHP Eclogite

作　　者：邱华宁[1,2] 徐义刚[1] 云建兵[1] 王强[1] 赵令浩[1] 

机构地区：[1]中国科学院广州地球化学研究所,广州510640 [2]构造与油气资源教育部重点实验室,中国地质大学,武汉430074

出　　处：《地质学报》2009年第8期1118-1124,共7页Acta Geologica Sinica

基　　金：国家自然科学基金(编号40772080和40272039)资助成果

摘　　要：高空间分辨率紫外激光显微探针40Ar-39Ar定年技术在钾矿物环带、次生加大边、多世代矿物和难分选矿物之年代学研究中发挥越来越重要的作用。南大别山朱家冲榴辉岩经过角闪岩相退变质作用,形成榴闪岩。本文利用激光显微探针40Ar-39Ar定年技术成功测定了朱家冲榴闪岩之石榴子石环外的角闪石"绿眼圈"年龄为217±3Ma,石榴子石环内的多硅白云母年龄265±3Ma,环外的钠云母年龄223±4Ma。榴闪岩基质激光阶段加热40Ar-39Ar分析,获得高温阶段坪年龄为230Ma。多硅白云母年龄可能指示朱家冲榴辉岩超高压变质作用发生在265Ma之前;基质年龄代表了退变质作用峰期发生于230Ma;而217Ma角闪石"绿眼圈"为退变质作用晚期产物。这些40Ar-39Ar年龄印证了岩石薄片观察的矿物结晶顺序。The Zhujiachong eclogite, distributed in the county of Huangzhen （renamed as Tianhuazhen）, Taihu, Anhui Province, was originally taken as low-temperature and high-pressure （LT-HP） eclogite, or cold＂ eclogite. Coesite pseudomorphs, however, indicated that it experienced ultra-high pressure （UHP） metamorphism. Amphibolite- facies retrograde metamorphism turned eclogite into garnet-bearing amphibolite. This study analyzed the retrograde amphobolite facies mineralogy of the eclogite using ^40Ar-^39Ar ultraviolet laser ablation microprobe （UVLAMP） to determine the ages of discrete minerals. The ^40Ar-^39 Ar apparent ages indicate that the UHP phengite formed before 265 Ma. Amphibolite-facies retrograde metamorphism occurring from 242 Ma to 217 Ma, accompanied by the hydrothermal activity, is responsible for the formation of coarse-grained paragonite and fluid inclusions in vein amphibole until 200 Ma.

关 键 词：激光显微探针 40Ar-39Ar定年 榴辉岩 榴闪岩 退变质作用 大别山 

分 类 号：P597.3[天文地球—地球化学]