| 华北克拉通中东部新太古代晚期变质火山岩及动力学体制 |
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| 引用本文： | 刘树文,包涵,高磊,孙国正,王伟,郭荣荣,郭博然,付敬浩,胡雅璐,白翔,胡方泱.华北克拉通中东部新太古代晚期变质火山岩及动力学体制[J].岩石学报,2021,37(1):113-128. |
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| 作者姓名： | 刘树文 包涵 高磊 孙国正 王伟 郭荣荣 郭博然 付敬浩 胡雅璐 白翔 胡方泱 |
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| 作者单位： | 北京大学造山带与地壳演化教育部重点实验室, 地球与空间科学学院, 北京 100871;中国地质大学(北京)地质过程与矿产资源国家重点实验室, 地球科学与资源学院, 北京 100083;东北大学深部金属矿山安全开采教育部重点实验室, 资源与土木工程学院地质系, 沈阳 110819;北京矿产地质研究院, 北京 100012;西南石油大学地球科学与技术学院, 成都 610500;中国地震局地质研究所, 吉林长白山火山国家野外科学观测研究站, 北京 100029;中国地震局地震与火山灾害重点实验室, 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 |
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| 基金项目： | 本文受国家自然科学基金项目（41772188、41530207）资助. |
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| 摘 要： | 热状态和壳幔岩浆作用是理解早期地壳形成演化动力学机制的关键。华北克拉通是世界范围内为数不多的保存有大量新太古代晚期(约26~25亿年)变质火山岩记录的克拉通之一,对揭示全球新太古代晚期壳-幔动力学演化过程具有重要的指示意义。在我们研究组近期关于华北克拉通中东部中新太古代热状态和地壳厚度研究基础上,本文收集并整理了726个华北克拉通中东部(包括中部带)新太古代晚期变质火山岩样品的有效地球化学资料。按照现代通用岩石地球化学标准来分类,这些样品主要包括超铁镁质岩石(其中含苦橄岩、苦橄质玄武岩和科马提岩,~7%)、稀土未分异型玄武岩(~14%)、稀土分异型玄武岩(~27%)、玻安岩(~4%)、高镁安山岩(~12%)、低镁安山岩(~26%)和英安岩-流纹岩(~10%)。然而不同区块之间火山岩岩石组合及其量比存在较大差异,其中吉林南部和赞皇等地区以大量稀土分异型玄武岩、高镁和低镁安山岩为主,含有少量的长英质火山岩;胶东、登封和阜新等地区以稀土未分异和稀土分异型玄武岩占有绝对优势,存在少量安山岩和长英质火山岩;冀北、冀东北部、冀东南部(迁安-滦县)、五台-云中山、辽北、辽南和鲁西等地区岩石组合比较复杂,最突出的特点是出现不同比例的玻安岩,组合有稀土未分异和大量稀土分异型玄武岩、高镁和低镁安山岩,出现少量超铁镁质岩石和长英质火山岩。岩石成因研究揭示稀土未分异型和分异型玄武岩、高镁安山岩和玻安岩主要形成于俯冲板片流体、熔体和沉积物熔体交代地幔的部分熔融,而低镁安山岩、英安岩和其它长英质火山岩则大都经历了上述俯冲相关初始岩浆的结晶分异或地壳物质熔融和地壳混染等过程。新太古代晚期胶东地区表现为相对较薄的地壳厚度和较高的地热梯度(18℃/km),而冀东地区表现为厚的地壳厚度和低的地热梯度(最低8.7℃/km),满足现代俯冲地热梯度需求,其它区域的地温梯度介于热俯冲和现代冷俯冲之间。综合以上资料,我们认为新太古代晚期板块构造体制已经是最主要的壳-幔动力学体制,地幔柱构造体制和板块构造-地幔柱联合作用体制可能仍然在局部地区存在,但其作用范围和强度已经明显减小。因此,随着地幔温度的下降,中太古代到新太古代晚期地幔柱和板片俯冲的转化可能是相互关联、此消彼长的动力学过程,而不是一个突变过程。
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| 关 键 词： | 新太古代晚期 变质火山岩及其成因 地壳热状态 动力学体制 华北克拉通中东部 |
| 收稿时间： | 2020/9/8 0:00:00 |
| 修稿时间： | 2020/11/15 0:00:00 |
Late Neoarchean metavolcanics and geodynamics regime in central and eastern North China Craton |
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| LIU ShuWen,BAO Han,GAO Lei,SUN GuoZheng,WANG Wei,GUO RongRong,GUO BoRan,FU JingHao,HU YaLu,BAI Xiang,HU FangYang.Late Neoarchean metavolcanics and geodynamics regime in central and eastern North China Craton[J].Acta Petrologica Sinica,2021,37(1):113-128. |
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| Authors: | LIU ShuWen BAO Han GAO Lei SUN GuoZheng WANG Wei GUO RongRong GUO BoRan FU JingHao HU YaLu BAI Xiang HU FangYang |
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| Institution: | MOE Key Laboratory of Orogenic Belts and Crustal Evolution, School of Earth and Space Sciences, Peking University, Beijing 100871, China;State Key Laboratory of Geological Processes and Mineral Resources, School of Earth Sciences and Resources, China University of Geosciences, Beijing 100083, China;MOE Key Laboratory on Safe Mining of Deep Metal Mines, Department of Geology, School of Resources and Civil Engineering, Northeastern University, Shenyang 110819, China;Beijing Institute of Geology for Mineral Resources, Beijing 100012, China;School of Geoscience and Technology, Southwest Petroleum University, Chengdu 610500, China;National Observation and Research Station of Jilin Changbaishan Volcano, Institute of Geology, China Earthquake Administration, Beijing 100029, China;Key Laboratory of Seismic and Volcanic Hazards, China Earthquake Administration, Beijing 100029, China; State Key Laboratory of Lithospheric Evolution, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China |
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| Abstract: | Thermal state and crust-and mantle-sourced magmatism are crucial to understanding geodynamic regime of early formation and evolution of continental crust.The North China Craton(NCC)is one of a few Archean cratons with records of Late Neoarchean(ca.2.6~2.5Ga)volcanic rocks in the world,which has important significance for revealing Late Neoarchean global crust-mantle dynamic processes.In this paper,based on our newly obtained Meso-to Neoarchean crustal thermal state and thickness,we selected 726 samples of Neoarchean meta-volcanic rocks from Central transitional zone and Eastern Block of the NCC.These samples include ultramafic rocks(i.e.komatiites,picrites and picrobasalts,~7%),REE-undifferentiated basalts(~14%),REE-differentiated basalts(~27%),boninites(~4%),high-Mg andesites(~12%),low-Mg andesites(~26%)and dacites-rhyolites(~10%).There are obvious differences in the lithological assemblages of metamorphic volcanic rocks and their lithological proportions in different areas of the NCC.Southern Jilin and Zanhuang areas mainly developed a lot of REE-differentiated basalts,andesites and minor dacites;Jiaodong,Dengfeng and Fuxin areas are dominated by REE-undifferentiated and-differentiated basalts with minor andesites and dacites;Eastern and northern Hebei,Wutai-Yunzhongshan,northern Liaoning,southern Liaoning and western Shandong areas are featured by REE-undifferentiated and-differentiated basalts,andesites with minor ultramafic rocks and dacites,especially by some boninites.The REE-undifferentiated and-differentiated basalts,boninites and high-Mg andesites and high-Mg dacites were mainly derived from partial melting of the mantle materials metasomatized by fluids and melts from subducted slabs and sediments,whereas the low-Mg andesites,dacites and other felsic volcanic rocks from either fractionation of the initial magmas or partial melting of pure crustal materials.Our studies on the thickness and thermal state of Neoarchean crust shows thin thickness and high geothermal gradient(18℃/km)in Jiaodong area,but thick thickness and low geothermal gradient(8.7℃/km),meeting the geothermal gradient of present-day subduction zone in eastern Hebei area.The geothermal gradients in the other areas are between those of hot subduction and modern cold subduction.Based on the above lines of evidence,we propose that plate tectonic regime had become the dominant crust-mantle dynamic mechanism in the Late Neoarchean.Though the mantle plume and plate-mantle plume interaction mechanisms might still exist in local areas,their scale and intensity significantly decreased in the Late Neoarchean.Therefore,with the decreasing mantle temperature,the Mesoarchean to Late Neoarchean transformation of mantle plume to plate subduction regimes may be an interrelated and reciprocal dynamic process,rather than a sudden transition. |
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| Keywords: | Late Neoarchean Metavolcanics and petrogenesis Crustal thermal state Geodynamic regime Central and eastern North China Craton |
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