作者：李旭平 焦丽香 郑庆道 董晓 孔凡梅 宋召...黑龙江省桦南地区麻山杂岩碎屑锆石complexzircondatingweightedaverageagesmetamorphicage同位素年代学前寒武纪基底碰撞造山事件绿片岩相古亚洲洋闭合佳木斯地块造山作用早古生代新元古代
摘要：黑龙江杂岩主要由绿片岩相变质岩和糜棱岩化构造片岩组成,长期以来与麻山杂岩一起被认为代表佳木斯地块的前寒武纪基底,但这种认识缺乏可信的同位素年代学及古生物资料的支持.对出露于黑龙江省东部桦南地区湖南营组绿片岩进行了锆石LA-ICP-MS U-Pb定年研究.结果显示锆石的Th/U比值为0.27～1.27,变化较大;获得两组~(206)pb/~(238)年龄数据:其加权平均年龄分别为:511±10Ma(n=13,MSWD=1.6)和274.7±3.6Ma(n=9,MSWD=0.91).黑龙江杂岩中最老的年龄969～747Ma表现来自中元古和新元古代.这些年龄与黑龙江杂岩的年龄与来自俯冲碰撞变质事件的～511Ma的年龄结合起来,表明黑龙江杂岩中含有经历晚新元古--早古生代造山作用的碎屑锆石,亦或代表着在俯冲拼贴过程中混入的麻山杂岩块体.～275Ma年龄反映黑龙江杂岩经历的一次碰撞造山事件,可能与晚古生代古亚洲洋闭合相关. Abstract： The Heilongjian complex is consist of greeschist rocks and tectonic mylonites, and has been believed making up of Precambrian basement with the Mashan complex together in northeastern China. This conclusion, however, lacks of evidences of isotopic age and paleontology. LA-ICP-MS zircon U-Pb dating of the greeschist from the Hunanying Formation of the Heilongjian complex is carried out in order to determine the age and to discuss geotectonic background and metamorphic events the Heilongjian complex has experienced. Results show that zircons from analyzed sample present available Th/U ratio between 0.27～1.27 and show well defined two group ages, i. e. weighted average ~(206)pb/~(238)U ages are 511±10Ma (n=13, MSWD=1.6) and 274.7±3.6Ma (n=9, MSWD=0.91). The oldest ages from 969～747Ma imply the origination of Mesoproterozoic to Neoproterozoic. These ages along with metamorphic age of～511 Ma display that the Heilongjian complex, contains detrital zircons, which are possibly derived from the spatially intimately associated Mash
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