大兴安岭北段下侏罗统柴河组的厘定及地质意义
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摘要
大兴安岭北段首次厘定出下侏罗统柴河组,为一套沉积岩及中性岩为主的火山岩岩石组合。在底部沉积岩层位中发现早侏罗世植物分子,为Podozamites sp.(苏铁衫属),Equisetites sp.(似木贼属)。火山岩-粗安岩锆石U-Pb同位素年龄为183.8±3.9Ma,时代为早侏罗世。锆石Hf同位素显示,初始~(176)Hf/~(177)Hf值分布于0.282935~0.282991之间,ε_(Hf)(t)值为+9.7~+11.4,Hf二阶段模式年龄T_(DM2)为495~612Ma,说明这些火山岩的原始岩浆来自新生中下地壳的部分熔融,表明额尔古纳地块的主体增生年代为新元古代。柴河期火山岩形成于活动陆缘弧环境,是早侏罗世蒙古-鄂霍茨克洋向南东方向俯冲的产物。下侏罗统柴河组的厘定,说明大兴安岭地区存在早侏罗世火山岩地层及相应的火山活动事件。该组的确立及引入,对大兴安岭中生代构造岩浆活动的研究及中生代火山岩地层划分对比、区域构造演化探讨具有重要的地质意义。
The Chaihe Formation of the Lower Jurassic is first defined in the northern Daxing'anling Range, which is a suite of sedimentary rocks and intermediate volcanic rocks. At the bottom of sedimentary rocks, we found plant molecular in the strata of Early Jurassic, namely Podozamites sp. and Equisetites sp. SHRIMIP zircon U-Pb age of the trachyandesites is 183.8±3.9 Ma. The ε_(Hf)(t) values of the zircons of trachyandesites range from +9.7~+11.4. The T_(DM2) model ages yield 495~612 Ma.This fact indicated that the rocks could have originated by partial melting of juvenile crust, and the accretion age of the Eergu'Na block's main part was Neoproterozoic. The volcanic rocks of Chaihe Formation formed in the environment of active continental arc, relating to the subduction of Mongolia Okhotsk ocean to the Southeast direction in the Early Jurassic. The determination of the Chaihe Formation of the Lower Jurassic indicates the volcanic activity in the Lower Jurassic in the Daxing'anling Range. The establishment and introduction of Chaihe Formation is of great geological significance for the study of tectonic-magmatic activities in the Mesozoic, the comparison of Mesozoic volcanic strata and regional tectonic evolution.
The Chaihe Formation of the Lower Jurassic is first defined in the northern Daxing'anling Range, which is a suite of sedimentary rocks and intermediate volcanic rocks. At the bottom of sedimentary rocks, we found plant molecular in the strata of Early Jurassic, namely Podozamites sp. and Equisetites sp. SHRIMIP zircon U-Pb age of the trachyandesites is 183.8±3.9 Ma. The ε_(Hf)(t) values of the zircons of trachyandesites range from +9.7~+11.4. The T_(DM2) model ages yield 495~612 Ma.This fact indicated that the rocks could have originated by partial melting of juvenile crust, and the accretion age of the Eergu'Na block's main part was Neoproterozoic. The volcanic rocks of Chaihe Formation formed in the environment of active continental arc, relating to the subduction of Mongolia Okhotsk ocean to the Southeast direction in the Early Jurassic. The determination of the Chaihe Formation of the Lower Jurassic indicates the volcanic activity in the Lower Jurassic in the Daxing'anling Range. The establishment and introduction of Chaihe Formation is of great geological significance for the study of tectonic-magmatic activities in the Mesozoic, the comparison of Mesozoic volcanic strata and regional tectonic evolution.
引文
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[19]王伟,许文良,王枫,等.满洲里-额尔古纳地区中生代花岗岩的锆石U-Pb年代学与岩石组合:对区域构造演化的制约.高校地质学报,2012,18(1):88-105.
[20]佘宏全,李进文,向安平,等.大兴安岭中北段原岩锆石U-Pb测年及其与区域构造演化关系.岩石学报,2012,28(2):571-594.
(1)内蒙古自治区第十地质矿产勘查开发院.内蒙古1∶5万乌音呼日勒庙幅、新巴尔虎右旗幅、霍特林呼都格幅、勃迪木呼都格幅区域地质调查报告.2017.
(2)内蒙古地矿局第二区调队一分队.内蒙古1∶20万索伦军马场幅、一二五公里幅区域地质调查报告.1990.
(3)吉林大学.内蒙古1∶5万河源、1355.3高地、基尔果山、毛尧口等四幅区域地质调查报告.2011.
(4)吉林大学.内蒙古1∶25万柴河镇幅区域地质调查报告.2013.
[2]佘宏全,李红红,李进文,等.内蒙古大兴安岭中北段铜铅锌金银多金属矿床成矿规律与找矿方向[J].地质学报,2009,83(10):1456-1472.
[3]李锦轶,张进,杨天南,等.北亚造山区南部及其毗邻地区地壳构造分区与构造演化[J].吉林大学学报(地球科学版),2009,39(4):584-605.
[4]刘永江,张兴洲,金巍,等.东北地区晚古生代区域构造演化[J].中国地质,2010,37(4):943-951.
[5]唐杰,许文良,王枫,等.张广才岭帽儿山组双峰式火山岩成因:年代学与地球化学证据[J].世界地质,2011,30(4):508-513.
[6]许文良,王枫,裴福萍,等.中国东北中生代构造体制与区域成矿背景:来自中生代火山岩组合时空变化的制约[J].岩石学报,2013,29(2):339-53.
[7]Mi K F,Liu Z J,Liu R B,et al.U-Pb zircon,geochemical and Sr-Nd-Hf isotopic constraints on age and origin of the intrusions from Wunugetushan porphyry deposit,Northeast China:implication for Triassic-Jurassic Cu-Mo mineralization in Mongolia-Erguna metallogenic belt[J].International Geology Review,2018,60(4):496-512.
[8]孟凡超,刘嘉麒,崔岩,等.中国东北地区中生代构造体制的转变:来自火山岩时空分布与岩石组合的制约[J].岩石学报,2014,30(12):3569-3585.
[9]郑吉林,王文东,杨华本,等.大兴安岭北部下侏罗统战备村组的建立及其地质意义[J].地质通报,2016,7:1106-1114.
[10]赵胜金,于海洋,周颖帅,等.内蒙古1∶5万乌音呼日勒庙等四幅区调新进展及主要成果[J].中国地质调查,2018,53(7):49-55.
[11]刘勃然,李伟,张守志,等.大兴安岭北段伸展构造[J].吉林大学学报(地球科学版),2016,46(5):1140-1148.
[12]黑龙江省区域地层表编写组.东北地区区域地层表(黑龙江省分册)[M].北京:地质出版社,1979.
[13]李文国,姜万德,王惠,等.内蒙古自治区岩石地层[M].武汉:中国地质大学出版社,1996.
[14]宋彪.用SHRIMP测定锆石U-Th-Pb同位素工作方法[J].地质通报,2015,34(10):1-12.
[15]Wu F Y,Yang Y H,Xie L W,et al.Hf isotopic compositions of the standard zircons and baddeleyites used in U-Pb geochronology[J].Chemical Geology,2006,234(1/2):105-126.
[16]Tang J,Xu W L,Wang F,et al.Geochronology and geochemistry of Neoproterozoic Magmatism in the Erguna Massif,NE China:petrogenesis and implications for the breakup of the Rodinia supercontinent[J].Precambrian Research,2013,224:597-611.
[17]Zhang J H,Ge W C,Wu F Y,et al.Large-scale Early Cretaceous volcanic events in the northern Great Xing'an Range,Northeastern China[J].Lithos:An International Journal of Mineralogy,Petrology,and Geochemistry,2008,102(1/2):138-157.
[18]Xu W L,Pei F P,Wang F,et al.Spatial-temporal relationships of Mesozoic volcanic rocks in NE China:Constraints on tectonic overprinting and transformations between multiple tectonic regimes[J].Journalof Asianearthsciences,2013,74(Sep.25):167-193.
[19]王伟,许文良,王枫,等.满洲里-额尔古纳地区中生代花岗岩的锆石U-Pb年代学与岩石组合:对区域构造演化的制约.高校地质学报,2012,18(1):88-105.
[20]佘宏全,李进文,向安平,等.大兴安岭中北段原岩锆石U-Pb测年及其与区域构造演化关系.岩石学报,2012,28(2):571-594.
(1)内蒙古自治区第十地质矿产勘查开发院.内蒙古1∶5万乌音呼日勒庙幅、新巴尔虎右旗幅、霍特林呼都格幅、勃迪木呼都格幅区域地质调查报告.2017.
(2)内蒙古地矿局第二区调队一分队.内蒙古1∶20万索伦军马场幅、一二五公里幅区域地质调查报告.1990.
(3)吉林大学.内蒙古1∶5万河源、1355.3高地、基尔果山、毛尧口等四幅区域地质调查报告.2011.
(4)吉林大学.内蒙古1∶25万柴河镇幅区域地质调查报告.2013.