河北怀来龙凤山青白口系长龙山组碎屑锆石LA-ICP-MS U-Pb年龄及其构造古地理意义
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中国地质科学院矿产资源研究所,中国地质大学(北京)地球科学与资源学院,中国地质大学(北京)地球科学与资源学院,中国地质大学(北京)地球科学与资源学院

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中央高校基本科研业务费专项资金(批准号:2652014005)


Detrital Zircon LA-ICP-MS U-Pb Dating of the Changlongshan Formation of Qingbaikou System in Huailai County, Hebei Provinceand Its TectonicPaleogeographic Significance
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Institute of Mineral Resources, Chinese Academy of Geological Sciences,School of the Earth Sciences and Resources, China University of Geosciences,School of the Earth Sciences and Resources, China University of Geosciences,School of the Earth Sciences and Resources, China University of Geosciences

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    摘要:

    河北怀来龙凤山地区青白口系长龙山组(或称骆驼岭组)因发现“龙凤山生物群”而备受关注。本文报道了龙凤山西坡剖面长龙山组中部临近“龙凤山生物群”化石产出层位之下的粉砂岩中碎屑锆石的LA-ICP-MS U-Pb年龄。其年龄分布于1573~2931 Ma之间,碎屑锆石年龄谱存在一个明显的峰值,峰值年龄为~185 Ga,此外还有其它若干次级峰值年龄,分别响应了华北克拉通主要的前寒武纪若干地质事件。年龄主峰(~1.85 Ga)记录了华北克拉通东、西两大陆块的碰撞拼合事件,~2.6 Ga(2.603 Ga和2.556 Ga)和~2.9 Ga(2.935 Ga)峰值年龄对应了华北克拉通重要的陆壳生长时间,前者对应了华北克拉通东部地壳生长的最高峰。介于2.4~2.0 Ga(2.07 Ga、2.177 Ga、2.228 Ga、2.286 Ga、2.324 Ga和2.388 Ga)的次级峰值年龄代表了华北克拉通经历的陆内拉伸-裂谷事件。~1.6 Ga(1.580 Ga)峰值年龄是大红峪的岩浆事件的反映,大致对应于Columbia超大陆裂解的时间。缺失广布华北克拉通的~2.5 Ga事件可能是由于长龙山期海侵超覆沉积使得~2.5 Ga的露头被普遍覆盖所致。参照长龙山组下伏地层下马岭组报道的斑脱岩年龄,本文测得的最小谐和年龄(1.573 Ga)并不能有效地约束其沉积时代的下限。对燕辽裂陷槽不同地区长龙山组或与之可对比地层的碎屑锆石年龄的对比研究表明,燕辽裂陷槽内部对上述构造事件响应存在差异,暗示了燕辽裂陷槽发育期内部古地理具有相当的复杂程度。秦皇岛柳江地区和辽东半岛青白口系长龙山组碎屑锆石年龄分布特征与燕辽裂陷槽内长龙山组存在的差异,很大程度上是受当时的古地理背景制约。

    Abstract:

    The Changlongshan Formation (also called the Luotuoling Formation) of Qingbaikou System in Huailai County, Hebei Province receives much concern for the discovery of the Longfengshan Biota. The study reports an LA-ICP-MS U-Pb age of detrital zircons from siltstone occurring in the middle Longshan Formation (near to the strata bearing the Longfengshan Biota) in the west slope of Longfengshan Mountain. The result shows that U-Pb ages yielded are distributed between 1573 Ma~2931 Ma, with a distinct peak at~1.85 Ga, and several other secondary age peaks responding to some geological events of the North China Craton (NCC) in the Pre-Cambrian. The main peak age of 1.85 Ga reveals the amalgamation event of the western and eastern blocks of the NCC, 2.6 Ga (2.603 Ga and 2.556 Ga) and 2.9 Ga (2.935 Ga) correspond to the important continental crust growth time of the NCC, and especially the former (2.6 Ga) correspond to the most prominent time of continental rapidly growth of the NCC. Detrital zircon ages of between 2.4~2.0 Ga (2.07 Ga, 2.177 Ga, 2.228 Ga, 2.286 Ga, 2.324 Ga and 2.388 Ga) record intracontinental extension and rifting events of the NCC. 1.6 Ga (1.580 Ga) age peak reflects the Gaoyuzhuang period magmatic event, roughly corresponding to the Columbia supercontinent breakup. Widespread lack of 2.5 Ga age peak of the NCC may be due to the Changlongshan transgression, which likely covers all the 2.5 Ga outcrop. Referring to the bentonite age (1.36~1.38 Ga) of underlying Xiamaling Formation, the minimum concordia age (1.573 Ga) of the detrital zircon ages obtained in this study can not effectively constrain the deposition time of the Changlongshan Formation. Comparative study on the detrital zircon ages of Changlongshan Formation or comparable strata within the YanLiao aulacogen indicates that internal differences response to the above tectonic events in the Yan-Liao Aulacogen, suggesting considerable complexity of the geography within the Yan-Liao Aulacogen in the Changlongshan period. The age distribution of detrital zircons from the Changlongshan Formation of Qingbaikou System in the Liujiang region and the Liaodong Peninsula has obvious differences with that in the YanLiao Aulacogen, which is largely restrained by the paleogeographical background.

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王振涛,沈阳,王训练,马伯永,黄晓宏.2017.河北怀来龙凤山青白口系长龙山组碎屑锆石LA-ICP-MS U-Pb年龄及其构造古地理意义[J].地质学报,91(8):1760-1775.
WANG Zhentao, SHEN Yang, WANG Xunlian, MA Boyong, HUANG Xiaohong.2017. Detrital Zircon LA-ICP-MS U-Pb Dating of the Changlongshan Formation of Qingbaikou System in Huailai County, Hebei Provinceand Its TectonicPaleogeographic Significance[J]. Acta Geologica Sinica,91(8):1760-1775.

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  • 收稿日期:2016-03-17
  • 最后修改日期:2016-05-26
  • 录用日期:2017-08-16
  • 在线发布日期: 2017-08-18
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