塔里木盆地东南缘阿克塔什塔格地区古元古代精细年代格架的建立及其地质意义  

Determination of the Paleoproterozoic Geochronological Framework in Aqtashtagh Area in Southeastern Tarim,China,and Its Geological Significance

作　　者：辛后田[1,2] 赵凤清[2] 罗照华[1] 刘永顺[2] 万渝生[3] 王树庆[2] 

机构地区：[1]中国地质大学(北京),北京100086 [2]天津地质矿产研究所,天津300170 [3]中国地质科学院北京离子探针中心,北京100086

出　　处：《地质学报》2011年第12期1977-1993,共17页Acta Geologica Sinica

基　　金：国土资源大调查项目(编号200413000006)资助成果

摘　　要：塔里木盆地东南缘的阿克塔什塔格地区,基底变质杂岩中含有较多的古元古代变质侵入体及敦煌岩群孔兹岩系。变质侵入体规模一般较小,它们以岩体特征明显、与米兰岩群的侵入接触界线清晰、钠质混合岩化不发育、角闪岩相变质等特征区别新太古代TTG岩系。其中,以岩体形式较大规模出露的有闪长质片麻岩、片麻状石英闪长岩、角闪石英正长岩、碳酸岩,呈脉体产出的有正长岩脉、(石英)二长岩脉和基性岩墙群等。对上述古元古代侵入体进行锆石SHRIMPU-Pb测年,获得片麻状闪长岩、片麻状石英闪长岩、灰白色长英质脉体(钠质混合岩化)的结晶年龄分别为2135±110Ma、2051.9±9.9Ma、2050±16Ma;石英正长岩的结晶年龄为1873.4±9.6Ma。此外,敦煌岩群中火山岩的年龄为2140.5±9.5Ma,其他新太古代变质岩的变质年龄均具有2.27～2.38Ga和1.9～2.05Ga的两期变质年龄。结合研究区前人获得的同位素年代学资料,建立塔里木克拉通古元古代的精细年代格架:古元古代中期(2.10～2.15Ga),敦煌岩群等孔兹岩系以及钙碱性岛弧型石英闪长岩侵位,指示了造山作用的早期俯冲阶段;古元古代晚期(1.93～2.05Ma),壳源岩石发生强烈的深熔作用形成火成碳酸岩、石英闪长岩以及钾质混合岩化,先存岩石经受角闪岩相变质和强烈的韧性剪切变形,为同碰撞造山阶段的响应;古元古代末期(1.85～1.87Ga)进入后造山阶段,发育石英二长岩、石英正长岩等后造山花岗岩。该精细年代格架的建立表明塔里木克拉通的早前寒武纪地质演化与华北克拉通更有亲缘性,二者同属于Nena陆块群,参与了古元古代哥伦比亚超大陆的汇聚。A large quantity of Paleoproterozoic metamorphic intrusive rocks and khondalites （in Dunhuang Group） were identified from basal metamorphic rocks in the Agetashtag area, southeastern margin of Tarim basin. The Paleoproterozoic granite （metamorphic intrusive rocks） differs from the Neoarchean TTG rocks in amphibolite facies metamorphism, non-sodium migmatization, and obvious boundary with Milan Group. Among them, the extensively exposed intrusions contain dioritic gneiss, gneissic quartz diorite, amphibole quartz syenite, and carbonatite, with syenite and monzonite marie rocks present in the forms of veins or dykes. Zircon SHRIMP U-Pb dating was performed on all the above-mentioned rocks. Crystallized ages obtained for gneissic diorite, gneissic quartz diorite, gray felsic veins （{elsic migmatization） and quartz syenite are 21354-110 Ma, 2051.9~9.9 Ma, 20504-16 Ma and 1873.44-9.6 Ma, respectively. In addition, the age of volcanic rocks in the Dunhuang Group is 1873.44-9.6 Ma. All other Neoarchean metamorphic rocks fall two metamorphic age groups of 2.27~2.38 Ga and 1.9~2.05 Ga. Combined with isotopic data by previous geologists for this area, a fine geochronological framework has been established as follows： （a） Mid-Paleoproterozic （2.10~2.15 Ga）, emplacement of the Dunhuang Group khondalite and calc-alkaline island arc quartz diorite indicates the early subduction stage of orogency; （b） Late Paleoproterozoic （1. 93~2. 05 Ga）, crust-derived rocks in this area underwent an entensive anatexis, forming igneous carbonatic rock, quartz diorite, and potassic migmatition, with pre- existing rocks suffering amphibolite facies metamorphism and intense ductile shearing deformation, and that is response to syn-collisional orogenesis; （c） The end of Paleoproterozoie era （1.85~ 1.87 Ga） saw the post-orogenic stage, during which the post-orogenic ganite such as quartz monzonite and quartz syenite were formed. At the early Meso-proterozoic developed swarms of NW-trending marie dykes and cove

关 键 词：精细年代格架 古元古代 锆石U-PB SHRIMP定年 塔里木克拉通 哥伦比亚超大陆 

分 类 号：P534.3[天文地球—古生物学与地层学]