LA-ICP-MS U-Pb geochronology of detrital zircons from the Huade Group in the northern margin of the North China Craton and its tectonic significance.
LA-ICP-MS U-Pb geochronology of detrital zircons from the Huade Group in the northern margin of the North China Craton and its tectonic significance.
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发表时间：
2009
影响因子：
1.8
通讯作者：
B. Hu;M. Zhai;Jh Guo;P. Peng;F. Liu;S. Liu
中科院分区：
文献类型：
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作者：
B. Hu;M. Zhai;Jh Guo;P. Peng;F. Liu;S. Liu
华德群位于北中国克拉通北缘，毗邻中亚造山带南段，东至古-中元古界白云鄂博和扎尔台-狼山裂谷，西至古-新元古代燕山凹陷，发育典型的长城、集县、青白口系，属典型的长城系、集县系和青白口系。丰镇群(钾长岩系)变质为麻粒岩相，U-Pb同位素年龄为1.9~1.8Ga，发育典型的长城系、集县系和青白口系。中亚造山带古生代岩石向北出露至华德群。地层层序显示出多个沉积旋回。每一个层序自下而上发育砾质砂岩、砂岩、碳酸盐岩、泥质岩。岩石组合指示了从河流到滨海相到浅海相的沉积环境。华德群的地层层序与榕树鄂博群和扎尔泰群相当。华德群4个样品的沉积锆石LA-ICPMS U-Pb年龄显示出1800+50 Ma和1850+50 Ma两个主要年龄峰这四个年龄组均对应于北中国克拉通的重大构造热事件。华德群底部变质卵石方石英碎屑锆石的最小一致年龄为1758±7 Ma，制约了该群最古老的沉积年龄。根据锆石颗粒的化学发光图像，1800±50 Ma和1850+50 Ma的主峰主要是变质颗粒，也有少量岩浆岩。这表明华德群的物源主要是古元古代变质岩，~2500 Ma和~2000 Ma的碎屑锆石代表了华德群的较老物源。碎屑锆石的U-Pb年龄制约了华德群从古元古代晚期到中元古代的沉积年龄。年龄组对应于北中国克拉通的重大构造-热事件，没有与中亚造山带地质事件有关的古生代年龄信息。地层特征表明，华德群是一个稳定的浅海-浅海沉积盆地。华德盆地、扎尔泰-狼山盆地和巴音鄂博盆地共同构成了中国克拉通北缘的被动大陆边缘裂谷系统。该裂谷可能与燕山、雄耳凹陷开始同时代，推测北中国克拉通与中亚造山带的分界线在华德盆地以北，通过对碎屑锆石特征的详细分析，认为华德群以南孔兹岩系可能是华德群的主要物源。
The Huade Group,consisting of low-grade and un-metamorphosed sedimentary rocks without volcanic rock,is located at the northern margin of the North China Craton and adjoining the south part of the Central Asian Orogenic Belt.It is east to the Paleo-Mesoproterozoic Bayan Obo and Zhaertai-Langshan rifts and northwest to the Paleo-Neoproterozoic Yanshan aulacogen,in which the typical Changcheng,Jixian and Qingbaikou systems are developed.The Fengzhen Group(kbondalite series ),which were metamorphosed to granulite facies with 1.9～1.8Ga U-Pb isotopic ages,occur south to the Huade Group.The Paleozoic rocks of the Central Asian Orogenic Belt outcrop north to the Huade Group.The stratigraphic sequences show several cycles of deposition.Each of them developed pebbly sandstones,sandstones,carbonate rocks,pelites from bottom upward.The rock association indicates the sedimentary environments evolving from fluvial through littoral to shallow marine facies.The stratigraphic sequences of the Huade Group are comparable to those of the Banyan Obo Group and the Zhaertai Group.The LA-ICP-MS U-Pb ages of the detrital zircons from four samples of the Huade Group show two main age peaks at 1800 + 50Ma and 1850 + 50Ma,as well as two other minor age peaks at～2500Ma and～2000Ma.All the four age populations correspond to significant tectonic-thermal events of the North China Craton.The youngest concordant age of the detrital zircons from meta-pebbly arkosite at the bottom of the Huade Group is 1758 + 7Ma,which constrains the oldest sedimentary age of this group.According to the CL images of the zircon grains,the main peaks at 1800 +50Ma and 1850 +50Ma are mostly of metamorphic grains,and a few of magmatic ones.This indicates that the provenances of the Huade Group are mainly Paleoproterozoic metamorphic rocks,with minor magmatic rocks.The detrital zircons of～2500Ma and～2000Ma represent older provenances of the Huade Group.The U-Pb ages of detrital zircons constrain the sedimentary age of the Huade Group from Late Paleoproterozoic to Mesoproteozoic.The age populations correspond to significant tectonic-thermal events of the North China Craton and there is no Paleozoic age information related to geological events of the Central Asian Orogenic Belt.The stratigraphic characteristics indicate the Huade Group is a stable shallow-hypabyssal sedimentary basin.The Huade basin,Zhaertai-Langshan basin and Bayan Obo basin commonly constitute a passive continental margin rift system at the northern margin of the North China Craton. This rift would have initiated coeval with the Yanshan and Xionger aulacogens.It is reasonable to suggest that the boundary between the North China Craton and the Central Asian Orogenic Belt is further north to the Huade Basin.Based on detailed analyses of the characteristics of detrital zircons,we suggest that the khondalite series south to the Huade Group were likely to be the main provenance of the Huade Group.