Zircon geochronology constraints on the age and nature of ‘Precambrian metamorphic rocks’ in the Xing’an block of Northeast China
Zircon geochronology constraints on the age and nature of ‘Precambrian metamorphic rocks’ in the Xing’an block of Northeast China
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DOI：
10.1080/00206814.2014.883183
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发表时间：
2014-03
影响因子：
2.6
通讯作者：
Wei Sun;Xiaoguo Chi;Zhi Zhao;Shile Pan;Jianfeng Liu;Rui Zhang;Jingyu Quan
中科院分区：
文献类型：
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作者：
Wei Sun;Xiaoguo Chi;Zhi Zhao;Shile Pan;Jianfeng Liu;Rui Zhang;Jingyu Quan
中国东北大兴安岭位于中亚造山带的东部。从北到南，大兴安岭分为额尔古纳、兴安和松辽三个板块。以往的U-Pb锆石年代学结果显示，兴安地块部分“前寒武纪变质岩”具有显生宙原岩年龄，质疑兴安地块是否存在前寒武纪基底。利用激光烧蚀电感耦合等离子体质谱法（LA-ICP-MS）测定了兴安地块疑似前寒武纪变质岩中的锆石U-Pb年龄。嫩江新开岭群变质流纹岩岩浆年龄为355.8 Ma。多宝山新开岭群千元岩碎屑锆石的居群分别为1505、810和485 Ma，最年轻的峰值限制了其沉积年龄小于485 Ma。嫩江新开岭群角闪片麻岩锆石的岩浆年龄为308.6 Ma。嫩江新开岭群糜棱质花岗岩锆石岩浆年龄为164 Ma。加拉山森林骆马湖群二云母石英片岩的碎屑锆石产量约为2419、1789、801、536、480和420 Ma，最年轻的峰值表明其沉积年龄<420 Ma。塔尔旗鄂尔群河组糜棱化绢绿泥石片岩碎屑锆石居群为982 ~ 948年，约519年和约410 Ma，最年轻的峰值表明其沉积年龄小于410 Ma。不同岩性的锆石年龄表明，大兴安岭变质岩形成于显生宙（164-485 Ma），地壳以古生代为主。综合上述研究结果和已发表的资料，我们认为兴安地块不存在前寒武纪变质基底。综上所述，年龄资料表明兴安地区可能不存在前寒武纪变质基底。
The Great Xing’an Range in Northeast China is located in the eastern part of the Central Asian Orogenic Belt. From north to south, the Great Xing’an Range is divided into the Erguna, Xing’an, and Songliao blocks. Previous U–Pb zircon geochronology results have revealed that some ‘Precambrian metamorphic rocks’ in the Xing’an block have Phanerozoic protolith ages, questioning whether Precambrian basement exists in the Xing’an block. We present laser ablation inductively coupled plasma mass spectrometry (LA–ICP–MS) U–Pb dating results for zircons from suspected Precambrian metamorphic rocks in the Xing’an block. Meta-rhyolites of the Xinkailing Group in Nenjiang yield magmatic ages of 355.8 Ma. Detrital zircons from phyllites of the Xinkailing Group in Duobaoshan yield populations of ca. 1505, ca. 810, and ca. 485 Ma, with the youngest peak constraining its depositional age to be <485 Ma. Zircons from amphibolitic gneisses of the Xinkailing Group in Nenjiang have magmatic ages of 308.6 Ma. Mylonitic granites of the Xinkailing Group in Nenjiang have zircon magmatic ages of 164 Ma. Detrital zircons from two-mica quartz schists of the Luomahu Group in the Galashan Forest yield ca. 2419, ca. 1789, ca. 801, ca. 536, ca. 480, and ca. 420 Ma, with the youngest peak indicating its depositional age as <420 Ma. Detrital zircons from mylonitized sericite–chlorite schist of the Ergunhe Formation in Taerqi yield populations of 982–948, ca. 519, and ca. 410 Ma, with the youngest peak demonstrating that its depositional age is <410 Ma. These zircon ages for a range of lithologies show that the Great Xing’an Range metamorphic rocks formed during the Phanerozoic (164–485 Ma) and that this crust is mostly Palaeozoic. Based on these results and published data, we conclude that there is no evidence of Precambrian metamorphic basement in the Xing’an block. In summary, the age data indicate that Precambrian metamorphic basement may not exist in the Xing’an region.