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

发布时间：2018-06-05 05:20

本文选题：长龙山组 + 青白口系　；参考：《地质学报》2017年08期

【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~1.85Ga,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(~1.85Ga)记录了华北克拉通东、西两大陆块的碰撞拼合事件,~2.6Ga(2.603Ga和2.556Ga)和~2.9Ga(2.935Ga)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2.4~2.0Ga(2.07Ga、2.177Ga、2.228Ga、2.286Ga、2.324Ga和2.388Ga)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。~1.6Ga(1.580Ga)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~2.5Ga事件可能是由于长龙山期海侵超覆沉积使得~2.5Ga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(1.573Ga)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]:Changlongshan formation (or Camel Ridge formation) of Qingbakou system in Longfengshan area of Huailai, Hebei Province has attracted much attention because of the discovery of Longfeng Mountain Biota. This paper reports the LA-ICP-MS U-Pb age of zircon from siltstone in the middle of Changlongshan formation near the fossil production horizon of Longfengshan biota in the Xipo section of Longfeng Mountain. The age distribution is between 1573 Ma and 2931 Ma. There is an obvious peak value in the age spectrum of the clastic zircon, with a peak age of 1.85Ga. in addition, there are several other sub-peak ages, respectively, which respond to some major Precambrian geological events in the North China Craton. The main age peak of 1.85Ga) recorded the collision and assemblage events of the two continental blocks in the east and west of the North China Craton (2.6Ga2.603Ga and 2.556Ga) and the peak age of 2.9Ga-2.935Ga) corresponding to the important continental crust growth time of the North China Craton, the former corresponding to the highest crustal growth in the eastern part of the North China Craton. The secondary peak age of 2.228Gaan2.228Gaan2.324Ga and 2.388Ga2.177Ga2.177Ga2.177Ga2.177Ga2.177Ga2.177Ga2.177Ga2.177Ga2.07Ga2.07Ga2.07Ga2.07Ga2.177Ga2.177Ga2.177Ga2.177Ga2.177Ga1.07Ga2.177Ga2.177Ga1.07Ga2.177Ga1.07Ga2.177Ga2.177Ga2.228GaN 2.324Ga and 2.388Ga2.388Ga). The absence of a wide spread of North China Craton may be due to the overlying marine transgression during the Changlong Mountains, which caused the outcrops of 2.5 Ga to be generally covered. The minimum harmonic age (1.573Ga) measured in this paper can not effectively constrain the lower limit of the sedimentary age according to the porphyry age reported by the Lower Maling formation in the underlying strata of the Changlongshan formation. A comparative study of the zircon ages of the Changlongshan formation or comparable strata in different areas of Yanliao rift trough shows that there are differences in the responses to the above tectonic events within the Yanliao rift trough. It suggests that the inner paleogeography of Yanliao rift trough is quite complicated. The age distribution of zircon from Qingbakou formation in Liujiang area of Qinhuangdao and Changlongshan formation of Qingbaikou system in Liaodong Peninsula is different from that of Changlongshan formation in Yanliao rift trough, which is restricted to a great extent by the paleogeographic background at that time.
【作者单位】：中国地质科学院矿产资源研究所国土资源部盐湖资源与环境重点实验室;中国地质大学(北京)博物馆;中国地质大学(北京)地球科学与资源学院;中国地质调查局;中国人民武装警察部队黄金第九支队;
【基金】：中央高校基本科研业务费专项资金(批准号:2652014005)资助
【分类号】：P531;P597.3

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