| 华北克拉通古/中元古代界线和相关地质问题讨论 |
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| 引用本文： | 赵太平,邓小芹,胡国辉,周艳艳,彭澎,翟明国.华北克拉通古/中元古代界线和相关地质问题讨论[J].岩石学报,2015,31(6):1495-1508. |
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| 作者姓名： | 赵太平 邓小芹 胡国辉 周艳艳 彭澎 翟明国 |
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| 作者单位： | 西北大学大陆动力学国家重点实验室, 西安 710069;中国科学院广州地球化学研究所矿物学与成矿学重点实验室, 广州 510640;中国科学院广州地球化学研究所矿物学与成矿学重点实验室, 广州 510640;中国科学院大学, 北京 100049;中国地质科学院地质力学研究所, 北京 100081;中国科学院地质与地球物理研究所岩石圈演化国家重点实验室, 北京 100029;中国科学院地质与地球物理研究所岩石圈演化国家重点实验室, 北京 100029;西北大学大陆动力学国家重点实验室, 西安 710069;中国科学院地质与地球物理研究所岩石圈演化国家重点实验室, 北京 100029 |
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| 基金项目： | 本文受国家重点基础研究发展计划973项目(2012CB416606)和西北大学大陆动力学国家重点实验室开放课题的联合资助. |
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| 摘 要： | 从18到16亿年,全球构造格局、古地理环境及生物演化发生重要变革。就全球地质演化历史而言,结晶基底的形成标志着古元古代的结束,而稳定盖层的发育标志着中元古代的开始。在国际地层年表上,古元古代末期(18~16亿年)被称之为"固结纪",古/中元古代的界线被划定在16亿年。在华北克拉通,一般认为"吕梁运动"是结晶基底最终形成的标志性构造-热事件,此后发育以长城系为代表的地台型沉积盖层。长期以来,我国地质界一直以长城系的沉积代表中元古代的开始,并将古/中元古代的界限置于18亿年,与国际地层年表相差2亿年,以至于在中外文献中对中国18~16亿年间的地质记录的表述方式混乱。究其原因,主要有:1华北克拉通基底的形成或最终克拉通化是以"吕梁运动"的结束为标志,结晶基底最晚期的变质年龄不晚于18亿年;2长城系的底界年龄(18亿年)一直缺乏可靠的数据,目前对华北克拉通范围内稳定盖层发育的起始时间及代表性沉积记录,尚无统一的认识;3对华北克拉通由基底形成到盖层的演化及构造体制转折的动力学过程等见解不一,也缺少精细的年代学制约。本文综述了华北克拉通尤其是南部地区18~16亿年岩浆-沉积记录的研究进展,就古/中元古代界线及相关地层对比和划分方案进行了讨论,并指出了亟需解决的重要科学问题。作者认为:1华北克拉通18~16亿年的火山-沉积记录在其南部地区最广泛、最完整。其中,熊耳群火山岩系(18~17.5亿年),包括底部发育的河湖相砂岩-泥岩沉积——大古石组,早于蓟县剖面的长城群,是华北陆块结晶基底形成后最早的盖层沉积。2华北克拉通古/中元古代的分界年龄目前有2种选择:一是18亿年,即熊耳群火山岩系底部大古石组的起始沉积年龄;二是16亿年,将蓟县剖面长城系的高于庄组划归蓟县系,长城系的大红峪组及以下地层归为古元古代,18~16亿年的火山-沉积岩系均归为古元古代末期的固结纪。3华北克拉通18~16亿年的地质记录包括早期的熊耳群和晚期的长城群火山-沉积岩系,以及多期次的基性岩墙、斜长岩杂岩体、A-型花岗岩(包括环斑花岗岩)等的发育。目前对它们的成因和产出的地球动力学背景存有诸多争议,精确构建该时期岩浆-沉积作用的时序,并与全球典型克拉通进行对比,进而解析华北克拉通由结晶基底形成到稳定盖层发育阶段的构造体制转折和动力学过程,为重新厘定古/中元古代界线和相关地层划分方案提供依据。这些是我国前寒武纪地质研究的重要课题。
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| 关 键 词： | 华北克拉通 古/中元古代界限 中元古代地层划分方案 长城系 熊耳群 高于庄组 大红峪组 大古石组 |
| 收稿时间： | 2015/3/30 0:00:00 |
| 修稿时间： | 2015/5/15 0:00:00 |
The Paleoproterozoic-Mesoproterozoic boundary of the North China Craton and the related geological issues: A review |
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| ZHAO TaiPing,DENG XiaoQin,HU GuoHui,ZHOU YanYan,PENG Peng and ZHAI MingGuo.The Paleoproterozoic-Mesoproterozoic boundary of the North China Craton and the related geological issues: A review[J].Acta Petrologica Sinica,2015,31(6):1495-1508. |
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| Authors: | ZHAO TaiPing DENG XiaoQin HU GuoHui ZHOU YanYan PENG Peng and ZHAI MingGuo |
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| Institution: | State Key Laboratory of Continental Dynamics, Northwest University, Xi'an 710069, China;Key Laboratory of Mineralogy and Metallogeny, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China;Key Laboratory of Mineralogy and Metallogeny, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China;University of Chinese Academy of Sciences, Beijing 100049, China;Institute of Geomechanics, Chinese Academy of Geological Sciences, Beijing 100081, China;State Key Laboratory of Lithospheric Evolution, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China;State Key Laboratory of Lithospheric Evolution, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China;State Key Laboratory of Continental Dynamics, Northwest University, Xi'an 710069, China;State Key Laboratory of Lithospheric Evolution, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China |
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| Abstract: | 1.8~1.6Ga is a period when the planet Earth witnessed a critical revolution in global tectonic configuration, paleogeographic environment and biological evolution. The formation of the crystalline basement represents the end of the Paleoproterozoic, whereas the development of stable sedimentary covers represents the start of the Mesoproterozoic. The Late Paleoproterozoic (1.8~1.6Ga) is referred as the "Statherian" in the international chronostratigraphic chart, and the boundary between the Paleoproterozoic and the Mesoproterozoic is inferred at 1.6Ga by the International Commision on Stratigraphy (ICS). In the North China Craton (NCC), the "Lvliang Movement" was usually considered to be a significant tectono-thermal event marking the final generation of the crystalline basement, which was followed by the development of platform-type sedimentary covers represented by the Changcheng System. Most Chinese geologists take the deposition of the Changcheng System represents the beginning of the Mesoproterozoic in China at 1.8Ga, some 200Myr older than the age proposed by ICS. The expressions of the geological records between 1.8Ga and 1.6Ga are confusing in both domestic and international literatures. This confusion arises as there are different viewpoints: 1) The formation of the crystalline basement of the NCC or its final amalgamation is marked by "the Lvliang Movement", and the metamorphic age of the crystalline basement is no later than 1.8Ga; 2) Although many researchers believe that the bottom boundary age of the Changcheng System is 1.8Ga, the starting time of stable sedimentary cover and representative sedimentary records in the NCC vary in different region; 3) The geodynamic evolution in the NCC and its tectonic transition from basement formation to stable sedimentary cover development are controversial, besides, previous studies also lack precise geochronological constraints. In this paper, we review the progresses in the study of magmatic and sedimentary records in the NCC, especially the southern NCC from 1.8Ga to 1.6Ga, discuss the Paleo-Mesoproterozoic boundary and the division of related strata, and then address the challenging scientific issues. We suggest that, 1) the volcanic and sedimentary records during 1.8Ga to 1.6 Ga are well preserved in the southern NCC, whilst the Xiong'er Group (1.8~1.75Ga), which is older than the Changcheng Group, is the earliest sedimentary cover recorded subsequent to the formation of the crystalline basement. The Dagushi Formation is a typical fluvial-lacustrine sedimentary sequence mainly composed of sandstone and mudstone at the bottom of the Xiong'er Group. 2) There are two alternative schemes about the boundary age of the Paleo-Mesoproterozoic, one is 1.8Ga, being referred to the starting sedimentary time of the Dagushi Formation at the bottom of the Xiong'er Group; the other is 1.6Ga which moves the Gaoyuzhuang Formation from the Changcheng Group into the Jixian Group, the Dahongyu Formation and the lower formations in the Changcheng Group are classified as the Paleoproterozoic layers, and the 1.8~1.6Ga volcanic and sedimentary sequences are classified as the Late Paleoproterozoic Statherian. 3) The geological records during 1.8~1.6Ga in the NCC consist of well preserved volcanic series of the Xiong'er Group and the other volcanic and sedimentary sequences, multi-stage mafic dike swarms, anorthosite and A-type granites (including rapakivi granites). Though their petrogenesis and geodynamic setting are controversial, it is important to investigate the precise age of the Late Paleoproterozoic magmatism and sedimentation in the NCC, and compare them with other representative cartons worldwide to analyze the tectonic transition from the formation of crystalline basement to the deposition of stable sedimentary cover and their geodynamic evolution, and to provide necessary constraints on the definition of the Paleo-Mesoproterozoic boundary and the division of related strata. They are all important issues for Precambrian geology of the NCC. |
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| Keywords: | North China Craton Paleo-Mesoproterozoic boundary The division of Mesoproterozoic strata Changcheng System Xiong'er Group Gaoyuzhuang Formation Dahongyu Formation Dagushi Formation |
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