大兴安岭地区扎兰屯变质杂岩的碎屑锆石U-Pb年龄及其大地构造意义  

Detrital zircon U-Pb dating of the Zhalantun Metamorphic Complex and its tectonic implications,Great Xing'an,NE China

作　　者：周建波[1] 王斌[1] 曾维顺[1] 曹嘉麟[1] 

机构地区：[1]吉林大学地球科学学院,长春130061

出　　处：《岩石学报》2014年第7期1879-1888,共10页Acta Petrologica Sinica

基　　金：国家973项目(2013CB429802);中国地质调查局项目(1212011120153);国家自然科学基金项目(41272241;41390441;41190075)联合资助

摘　　要：兴安地块位于额尔古纳和松辽地块之间,长期存在着是稳定陆块和造山带等不同的认识。本文针对兴安地块南部扎兰屯地区出露的原兴华渡口群进行了专项研究,结合前人的研究成果,对该变质杂岩的形成时代、碎屑锆石年龄谱进行了研究,研究成果对该地块的大地构造属性具有重要的制约作用。（1）扎兰屯地区变质杂岩主要为绿片岩-低角闪岩相变质的碎屑岩-火山碎屑岩系,其形成时代晚于481Ma,为早古生代晚期。岩石组合、变质程度与年代学研究表明其与北部的典型兴华渡口群不同,两者不能作为同一地层单元,应该予以解体。（2）扎兰屯变质杂岩碎屑锆石年龄谱主要分为三期：481~580Ma,峰期年龄为529Ma;699~998Ma,峰期年龄为833Ma和1213~3200Ma峰期年龄为2000Ma,分别记录了泛非期Gondwana、新元古Rodinia两期重大地质事件和变质基底的年龄信息。（3）兴安地块以发育兴华渡口群为标志,存在时代为新元古代甚至为太古代的变质结晶基底,因此兴安地块应为一稳定的微陆块,而非夹持于额尔古纳和松辽地块之间的造山带。The Xing＇ an Block is located in the transitional area between the Eerguna and Songliao blocks in the CAOB, with a controversial tectonic affinity of micro-continent vs. orogenic belt. In this paper, we focused on the Zhalantun Metamorphic Complex from the Zhalantun area in the Xing＇ an Block. The Zhalantun Metamorphic Complex was named ＇ Xinghuadukou Group＇ according 1 ： 200000 geological map, which consists of metasandstone, slate, phyllite, mica-schist, meta-acidic volcanics and meta-volcanic tuff. Mica-schist of analyzed sample was collected from south of the Xiangyangyu Reservoir, which consists of quartz （35% -40% ）, chlorite （20% -25% ）, muscovite （20% -25% ） and feldspar （8%）. Sample D09-02A yielded abundant zircon grains, most of which are rounded to subhedral and range from 50 to 180μm in size. CL imaging reveals that most grains are oscillatory zoned and of magmatic origin, although some portions are darker with less distinct zoning. A total of 55 analyses were made on 55 grains. The data show a spread along concordia, with variable discordance. The detrital zircon components show great variation in U and Th contents and Th/U ratios, ranging respectively from 196 ×10^-6 -2106 × 10^-6, 75 × 10^-6 -2455×10^-6 and 0. 2 - 1.8. The 55 zircons from DO9- 02A yield apparent ages ranging from 2952 ± 32 to 481± 12Ma. These results not only give information for the formation ages and detrital zircon age distributions of the Zhailantun Metamorphic Complex in this area, but also show the evidence to confirm the tectonic affinity of the Xing＇ an Block. （ 1 ） The Zhalantun Metamorphic Complex mainly occurs as a sequence of meta-clastic and meta- volcaniclastic rocks and shows greenschist to low-amphibolite facies metamorphism. Its formation age is younger than 481Ma and different from that of the Xinghuadukou Group in the north of the Great Xing＇ an. （2） Detrital zircon U-Pb dating of the Zhalantun Metamorphic Complex yields three age groups at： 481 -580Ma with a peak ag

关 键 词：兴安地块 扎兰屯变质杂岩 碎屑锆石年龄 大地构造属性 中亚造山带 

分 类 号：P597.3[天文地球—地球化学]