辽东营口—辽阳地区古元古代花岗岩和变质基性岩形成时代及意义

李超 孙克克 陈斌
摘要:遼东地区保存有较为完好的古元古代地质记录。对位于辽东营口—辽阳地区古元古代花岗岩(建一花岗岩)和变质基性岩(隆昌变质辉绿岩和蒜盘峪变质辉长岩)进行了锆石UPb定年、地球化学和岩石成因学研究。结果表明:建一花岗岩形成于(2 322±18)Ma,隆昌变质辉绿岩形成于(2 335±21)Ma,蒜盘峪变质辉长岩形成于(2 353±22)Ma;建一花岗岩源自太古宙古老地壳部分熔融,属于准铝质钙碱性I型花岗岩,富集Rb、Ba、U等大离子亲石元素,亏损Nb、Ta、Zr、Hf等高场强元素,具有俯冲带岩浆特征;隆昌变质辉绿岩和蒜盘峪变质辉长岩均具有富集型洋中脊玄武岩(EMORB)特点,并显示岛弧地球化学特征;隆昌变质辉绿岩源自新太古代富集程度不高的地幔部分熔融,并在上升过程中受到年轻地壳的改造,蒜盘峪变质辉长岩是古太古代—中太古代富集地幔部分熔融的产物;古元古代早期,辽吉地区处于大陆弧后盆地构造环境,弧后伸展作用导致大陆岩石圈部分熔融产生花岗岩和基性岩,在后期的地体拼贴过程中,两者遭受到不同程度的变质变形,进而形成了条痕状花岗岩和变质基性岩。
关键词:花岗岩;基性岩;古元古代;锆石UPb年龄;地球化学;弧后盆地;胶辽吉带;华北克拉通
中图分类号:P588.12文献标志码:A
Paleoproterozoic Granites and Metamafic Rocks from YingkouLiaoyang
Area of the Eastern Liaoning and Their Significance
LI Chao1, SUN Keke1, CHEN Bin1,2
(1. School of Earth and Space Sciences, Peking University, Beijing 100871, China; 2. School of Resources
and Environmental Engineering, Hefei University of Technology, Hefei 230009, Anhui, China

Abstract: Paleoproterozoic geological records are well preserved in the eastern Liaoning. The zircon UPb dating, geochemical and petrogenesis of Paleoproterozoic granites (Jianyi granite) and metamafic rocks (Longchang metadiabase and Suanpanyu metagabbro) in YingkouLiaoyang area of the eastern Liaoning were studied. The results show that LAICPMS zircon UPb ages of Jianyi granite, Longchang metadiabase and Suanpanyu metagabbro are (2 322±18), (2 335±21), (2 353±22)Ma, respectively; Jianyi Granite forms from partial melting of Archean crust, and belongs to metaluminouscalcalkaline Itype granite, and is enriched in large ion lithophile element (LILE), and is depleted in high field strength element (HFSE), showing the characteristics of magma in subduction zones; Longchang metadiabase and Suanpanyu metagabbro belong to enriched midocean ridge basalts (EMORB) and have the geochemical characteristics of island arc; Longchang metadiabase is generated from partial melting of Neoarchean mantle which is not very enriched, and the diabase is contaminated by juvenile crust during upwelling; Suanpanyu metagabbro is produced from partial melting of PaleoarcheanMesoarchean enriched mantle; LiaoningJilin region is a continental backarc basin in Early Paleoproterozoic, and the strong extension in the backarc region results in partial melting of continental lithosphere, which generates the granites and metamafic rocks; these rocks are later metamorphosed, deformed and pushed together in later processes of terrane amalgamation.
Key words: granite; mafic rock; Paleoproterozoic; zircon UPb age; geochemistry; backarc basin; JiaoLiaoJi Belt; North China Craton
0引言
華北克拉通具有38 Ga的演化历史,丰富的太古宙—古元古代地质记录使其成为研究早期地壳演化这一重大科学问题的天然实验室[110]。华北克拉通被中部造山带划分为东部陆块和西部陆块,胶辽吉带将东部陆块进一步划分为龙岗陆块和狼林陆块,孔兹岩带将西部陆块进一步划分为阴山陆块和鄂尔多斯陆块[1114]。
胶辽吉带内古元古代岩石保存较为完好,出露有一套具有条带状、片麻状特征,被称为条痕状花岗岩(辽吉花岗岩)的古元古代二长花岗片麻岩[15]。学术界对其来源、成因、类型及构造环境等一直争论不休:刘光启将该花岗岩识别为层状混合岩,认为其原岩是沉积变质岩[16];赵凤顺等认为该花岗岩以火山沉积岩重熔型的S型花岗岩为主[1718];路孝平等认为该花岗岩为A型花岗岩[1920],杨明春等则认为该花岗岩属于I型花岗岩[21]。此外,在胶辽吉带北部的辽东地区亦分布有古元古代变质辉长岩(部分变质程度达到斜长角闪岩)。关于这些变质基性岩的形成环境,刘永达等认为辽河群早期沉降阶段的海相拉斑玄武岩形成于大陆边缘或类似弧后盆地的大地构造环境[22];王艺芬等认为辽东古元古代基性岩具有大陆拉斑玄武岩和大洋拉斑玄武岩的双重特征,是辽河裂谷由大陆壳向大洋壳演化过程中的产物[23];Meng等认为基性岩形成于岛弧环境[2425],而Wang等则认为基性岩是陆内裂谷作用的产物[26]。
上述有关条痕状花岗岩及变质基性岩的争议严重制约了对区域构造演化的深入认识。作为辽吉地区重要岩石组成,条痕状花岗岩和变质基性岩经历了区域形成与演化的整个过程,并在持续的地质演化过程中经历了强烈变形,因此,对花岗岩和变质基性岩进行年代学、地球化学和成因学研究,可以解决上述争议,还原辽吉地区古元古代地质演化的整个过程,并进一步深入探讨华北克拉通早前寒武纪构造样式。鉴于此,本文选择辽东地区条痕状花岗岩和变质基性岩,对其进行详细的年代学、地球化学和成因学研究,以期进一步深入探讨胶辽吉带北部辽吉地区的早前寒武纪地质演化。
1区域地质背景
胶辽吉带呈NE—SW向展布于华北克拉通东部,介于龙岗陆块和狼林陆块之间,展布范围包括北部的辽吉地区和南部的胶北地区,辽东地区在古元古代地质构造划分上属于辽吉地区。辽吉地区古元古代岩石组合主要包括变质火山沉积岩、花岗岩和镁铁质侵入体(图1),其中变质火山沉积岩被划分为北侧的老岭群和北辽河群、以及南侧的集安群和南辽河群[27]。老岭群和北辽河群由透闪变粒岩、钠长浅粒岩、变质石英砂岩、硅质条带大理岩、白云石大理岩、十字石榴二云片岩和千枚岩等组成,原岩为陆源碎屑岩碳酸盐岩建造[28];集安群和南辽河群由透辉变粒岩、蛇纹石化大理岩、斜长角闪岩、石墨大理岩、细粒黑云片麻岩、石榴矽线片麻岩等组成,原岩为火山岩陆源碎屑岩碳酸盐岩建造,以含有较多的变质火山岩区别于老岭群和北辽河群。
近年来的研究表明,辽吉地区火山沉积岩形成于2.0~2.1 Ga,并于1.88~1.90 Ga发生变质作用[2939]。区域古元古代花岗质岩浆作用分为两期:条痕状花岗岩形成于约2.2 Ga[19,21,4043];斑状花岗岩和碱性正长岩侵位于1.85~1.88 Ga[28,4447]。辽吉地区古元古代基性岩亦分为约2.2 Ga[2426,48]和约1.85 Ga[4952]两期,但与火山沉积岩和花岗岩相比出露较少。
2岩石学特征
条痕状花岗岩(二长花岗岩)采自辽宁省营口市建一镇附近[图2(a)],侵入于南辽河群里尔峪组中(简称“建一花岗岩”)。建一花岗岩呈浅肉红色[图3(a)],具中粗粒花岗变晶结构、片麻状构造。主要矿物组成为石英(体积分数为25%~30%)、斜长石(15%~20%)、微斜长石(10%~15%)、条纹长石(10%~15%)、钾长石(约5%)、磁铁矿(约3%)和角闪石(1%~3%),副矿物有锆石、榍石、独居石、褐帘石等[图3(d)]。石英呈他形粒状,大都呈集合体排布,具有拉长和波状消光现象;斜长石呈短柱状,发育聚片双晶,部分遭受绢云母化和黝帘石化;微斜长石发育格子双晶[图3(d)]。
变质基性岩分别采自辽宁省辽阳市隆昌镇(简称“隆昌变质辉绿岩”)和蒜盘峪村(简称“蒜盘峪变质辉长岩”)附近[图2(b)、(c)],侵位于北辽河群里尔峪组中。隆昌变质辉绿岩呈深绿色[图3(b)],具有细粒变余辉长结构,受后期变质变形作用的影响;辉石已被交代成细粒角闪石,呈不规则柱粒状,部分纤状[图3(e)]。隆昌变质辉绿岩主要矿物组成为斜长石(体积分数为45%~50%)、角闪石(30%~45%)、石英(3%~5%)和绿帘石(1%~3%),副矿物主要为磁铁矿、钛铁矿。矿物定向明显,斜长石呈他形—半自形板粒状,遭受绢云母化和钠黝帘石化。角闪石遭受绿泥石化、绢云母化。蒜盘峪变质辉长岩呈深灰色[图3(c)],已变质成为斜长角闪岩[图3(f)],岩石具粒状变晶结构,矿物颗粒较大,变质重结晶程度明显高于隆昌变质辉绿岩。蒜盘峪变质辉长岩主要矿物组成为角闪石(体积分数为65%~70%)和斜长石(25%~30%),斜长石发生轻微绢云母化。
3分析方法
用于LAICPMS年代学测定的样品通过常规重选和磁选技术分选出锆石;阴极发光(CL)图像在北京锆年领航科技有限公司的扫描电镜JSM6510上拍摄完成;锆石UPb定年在中国地质科学院国家地质实验测试中心完成;LAICPMS激光剥蚀系统为美国New Wave公司生产的ArF准分子系统,激光器波长为193 nm,ICPMS仪为Thermo Elment Ⅱ型;采用GJ1[53]和Plesovice[54]作为外标进行校正,同位素比值及年龄误差类型均为1σ;数据结果处理采用ISOPLOT2.49软件[55]。
全岩主量、微量元素分析在北京大学造山带与地壳演化教育部重点实验室完成。主量元素分析采用X射线荧光光谱法(XRF)进行,分析误差优于5%;微量元素分析在ICPMS仪上测定;元素含量(质量分数,下同)大于10×10-6的精度优于5%,小于10×10-6的精度优于10%。
全岩RbSr、SmNd同位素的分离及测试在核工业北京地质研究院分析测试研究中心完成,化学分离和纯化通过阳离子交换柱法完成。同位素比值在IsoProbeT热电离质谱计上完成,分析误差小于05%。Sr质量分馏用N(86Sr)/N(88Sr)=0119 4进行校正;Rb实验室流程本底为2×10-10 g,Sr为2×10-10 g。Nd质量分馏用N(146Nd)/N(144Nd)=0721 9进行校正;SmNd全流程本底小于50×10-12 g。
4结果分析
4.1锆石UPb年龄
建一花岗岩锆石为浅灰色短柱状[图4(a)],晶形较为完好,具有岩浆锆石典型的韵律环带结构,锆石长80~150 μm,长短轴比值介于10~15之间。w(Th)/w(U)值为040~0.62,N(207Pb)/N(206Pb)年龄为2 256~2 400 Ma(表1)。23个分析点的加权平均年龄为(2 322±18)Ma,平均标准权重偏差(MSWD)为0.77(置信度为95%),因此,建一花岗岩的结晶年龄为(2 322±18)Ma[图5(b)]。
隆昌变质辉绿岩锆石为短柱状至长柱状[图4(b)],晶形略有破碎,具有岩浆锆石典型的韵律环带结构,锆石长80~120 μm,长短轴比值介于10~1.5之间。w(Th)/w(U)值为0.45~1.26,N(207Pb)/N(206Pb)年龄为2 269~2 393 Ma(表1)。17个分析点的加权平均年龄为(2 335±21)Ma,MSWD值为082(置信度为95%),因此,隆昌变质辉绿岩的结晶年龄为(2 335±21)Ma[图5(d)]。
蒜盘峪变质辉长岩锆石为短柱状[图4(c)],晶形发生破碎,锆石长70~110 μm,长短轴比值介于10~12之间。w(Th)/w(U)值为0.41~0.84,属于岩浆锆石,N(207Pb)/N(206Pb)年齡为2 283~2 424 Ma(表1)。19个分析点的加权平均年龄为(2 353±22)Ma,MSWD值为15(置信度为95%),因此,蒜盘峪变质辉长岩的结晶年龄为(2 353±22)Ma[图5(f)]。
4.2地球化学特征
建一花岗岩主要成分包括SiO2(含量为7326%~7445%)、Al2O3(1189%~1325%)、K2O(403%~474%)、Na2O(364%~437%)、TFe2O3(205%~348%)、CaO(114%~132%)、TiO2(015%~024%)、MgO(010%~020%)和MnO(003%~004%)(表2)。建一花岗岩稀土元素总含量较高,轻、重稀土元素分馏明显[图6(a)],w(La)N/w(Sm)N
值为273~662,w(La)N/w(Yb)N值为479~2720,具有弱的负Eu异常。在球粒陨石标准化稀土元素配分模式[图6(a)]中,轻稀土元素富集,呈右倾模式,重稀土元素呈平坦分布模式。在原始地幔标准化微量元素蛛网图[图6(b)]中,建一花岗岩具有较高的Rb含量((99.44~125.61)×10-6)、U含量((1.21~2.18)×10-6)、Nd含量((17.90~8478)×10-6),以及较低的Nb含量((1221~2455)×10-6)、Ta含量((0.90~1.75)×10-6)和P含量((119.42~153.17)×10-6)。其中,w(·)N为元素含量球粒陨石标准化后的值。
隆昌变质辉绿岩SiO2含量为5267%~5378%,Al2O3为1274%~1301%,K2O为027%~038%,Na2O为534%~558%,TFe2O3为1202%~1291%,CaO为520%~572%,TiO2为132%~140%,MgO为707%~730%,MnO为009%~010%(表2)。隆昌变质辉绿岩轻、重稀土元素分馏不显著[图6(c)],w(La)N/w(Sm)N值为177~267,w(La)N/w(Yb)N值为348~751,无或仅有略微负Eu异常。样品轻稀土元素相对重稀土元素略有富
5讨论
5.1岩石成因
建一花岗岩的10 000w(Ga)/w(Al)值大于26,在Whalen等提出的判别图解[58]中落入在A型花岗岩区域[图7(a)]或是接近A型花岗岩区域[图7(b)],路孝平等也据此认为辽吉地区古元古代条痕状花岗岩为A型花岗岩[1920,59]。然而,A型花岗岩和高分异的I型花岗岩地球化学特征非常相似,不能仅仅依靠10 000w(Ga)/w(Al)值来判断岩石是否为A型花岗岩。建一花岗岩中不含碱性矿物,不含铁橄榄石和钛铁矿,缺乏A型花岗岩的典型特征:在TAS图解中,建一花岗岩位于亚碱性花岗岩区域内[图8(a)];在K2OSiO2图解中,建一花岗岩位于高钾钙碱系列区域[图8(b)]。
图(a)、(b)引自文献[58];图(c)引自文献[60]
因此,建一花岗岩是钙碱性花岗岩,不是碱性花岗岩,也就不是A型花岗岩。建一花岗岩含有榍石和磁铁矿,表明岩浆富水且具有高的氧逸度,这是I型花岗岩的典型特征。在稀土元素特征方面,A型花岗岩通常显示巨大的负Eu异常(V字形),但建一花岗岩Eu异常(035~063)并不显著[图6(a)],且富集轻稀土元素,亏损重稀土元素,与A型花岗岩富集重稀土元素的特征相矛盾。在图6(b)中,建一花岗岩富集Rb、Ba、U等大离子亲石元素,亏损Nb、Ta、Zr、Hf等高场强元素,具有俯冲环境下I型花岗岩的典型特征。建一花岗岩铝饱和指数(ASI)为087~091,A/NK值为105~108,在A/CNKA/NK图解中落入准铝质区域[图8(c)],属于准铝质I型花岗岩,而不是过碱性A型花岗岩。
建一花岗岩具有相对平坦的重稀土元素分布模式[图6(a)],反映其源自无石榴石残留相的熔融源区。强烈亏损的Sr元素[图6(b)]暗示花岗岩源区处于斜长石稳定域内。建一花岗岩εNd(t)值为-92~-12,二阶段模式年龄为2 810~3 454 Ma,大于岩石形成年龄,表明花岗岩源区主要为太古宙古老地壳。建一花岗岩富集Rb、Ba、U等大离子亲石元素和轻稀土元素,亏损Nb、Ta、Zr、Hf等高场强元素,具有明显的俯冲带岩浆特征[6466]。这种岛弧地球化学特征可能是花岗质岩浆本身的特点,也可能是继承自源区的太古宙地壳。在RbY+Nb图解中,建一花岗岩落入火山弧花岗岩以及火山弧花岗岩和板内花岗岩之间的过渡区域[图7(c)],花岗岩w(Nb)/w(Ta)值(1359~1449)介于地壳w(Nb)/w(Ta)值(11~12)和地幔w(Nb)/w(Ta)值(约175)之间,反映其源区受到了来自俯冲带交代地幔流体的影响[67]。
在TAS图解中,隆昌变质辉绿岩和蒜盘峪变质辉长岩均位于亚碱性区域[图8(a)]。隆昌变质辉绿岩和蒜盘峪变质辉长岩的球粒陨石标准化稀土元素配分模式呈略微右倾模式[图6(c)、(e)],具有明顯的富集型洋中脊玄武岩(EMORB)地球化学特征,这一点也得到了w(Nb)/w(Yb)值的验证。在Nb/YbTh/Yb图解中,隆昌变质辉绿岩和蒜盘峪变质辉长岩均位于EMORB上方,表明两者同时具有弧岩浆特征[图9(b)]。蒜盘峪变质辉长岩富集Rb、Ba、Th、U等大离子亲石元素,且隆昌变质辉绿岩和蒜盘峪变质辉长岩明显亏损Nb、Ta、Zr、Hf等高场强元素[图6(d)、(f)]。此外,在Hf/3ThNb/16图解[图9(a)]中,蒜盘峪变质辉长岩位于火山弧玄武岩区域内,隆昌变质辉绿岩位于火山弧玄武岩与板内玄武岩之间。因此,笔者认为建一花岗岩、隆昌变质辉绿岩和蒜盘峪变质辉长岩最有可能的产出环境为大陆弧后盆地。同时,相比于蒜盘峪变质辉长岩,较晚侵位的隆昌变质辉绿岩显示较低的Ba、Th、Pb等流体活动元素含量,较高的εNd值,表明其形成过程中软流圈地幔贡献逐渐增大,标志着弧后盆地愈发成熟。
在初始N(87Sr)/N(86Sr)εNd(t)图解中,蒜盘峪变质辉长岩位于地幔序列中,较为接近EMⅠ型富集地幔,隆昌变质辉绿岩则偏离地幔序列(图10)。隆昌变质辉绿岩εNd(t)值为-2.0~-0.8,二阶段模式年龄为2 791~2 885 Ma,暗示隆昌变质辉绿岩源自新太古代富集程度不高的地幔部分熔融,并在上升过程中受到年轻地壳的改造。蒜盘峪变质辉长岩εNd(t)值为-7.0~-3.3,二阶段模式年龄为3 006~3 303 Ma,表明其源自古太古代—中太古代富集地幔的部分熔融。此外,地壳中K2O和Rb的富集程度远大于地幔。因此,可以通过观察εNd(t)值随K2O和Rb含量的变化关系来判断地幔岩石是否受到地壳的混染。如果地幔岩石受地壳混染明显,则εNd(t)值会随着K2O和Rb含量发生规律性变化。但隆昌变质辉绿岩和蒜盘峪变质辉长岩的K2O、Rb含量与εNd(t)值并无明显关系,表明变质基性岩受地壳混染微弱或不明显(图11)。
图10初始N(87Sr)/N(86Sr)εNd(t)图解
Fig.10Diagram of Initial N(87Sr)/N(86Sr)εNd(t)
图11变质基性岩K2OεNd(t)图解及RbεNd(t)图解
Fig.11Diagrams of K2OεNd(t) and RbεNd(t) of Metamafic Rocks
5.2构造演化
关于辽吉地区古元古代地质演化,前人的学术观点大致可以分为裂谷和岛弧两类。裂谷观点认为华北克拉通东部陆块在太古宙时为一整体,在古元古代早期经历了裂谷作用而形成洋盆,将东部陆块分裂为北部的龙岗陆块和南部的狼林陆块,其后伴随着洋盆的消减闭合,最终裂谷消失,龙岗陆块和狼林陆块又重新拼合[26,29,7073]。这一观点着重强调龙岗陆块和狼林陆块在太古宙时本来是一整体,正是由于古元古代的裂谷作用才产生了胶辽吉带,辽吉地区的演化经历了一个从大陆拉张形成洋盆到大洋俯冲消减陆块重新拼合的完整威尔逊旋回,裂谷作用是这一观点的核心内容。而与裂谷观点相悖的岛弧观点则认为龙岗陆块和狼林陆块之前并不在一起,两陆块无亲缘关系,只是由于大洋的消失才使得两陆块最终拼合在一起[24,31,50,7475]。这一观点强调俯冲作用在胶辽吉带形成过程中的重要作用及意义,并且龙岗陆块和狼林陆块在古元古代之前没有亲源性。此外,近年来还有研究提出了双向俯冲再闭合的模型[52]。
辽东地区南辽河群和北辽河群的主要差异在于:南辽河群主要由火山碎屑岩构成,具有逆时针的变质PT轨迹;而北辽河群主要是陆源碎屑岩,具有顺时针的PT轨迹,并且在吉林南部集安群与北部老岭群的差别也同样如此[27,32]。此外,东南部集安群和南辽河群内卷入的古元古代侵入岩也明显多于西北部的老岭群和北辽河群。上述岩石构造组合的空间分布最符合板块构造体制下的大陆弧后盆地环境[7677];东南部的集安群和南辽河群靠近俯冲带海沟一侧,西北部的老岭群和北辽河群靠近内陆一侧,来自火山弧一侧的火山碎屑岩、侵入岩和来自内陆一侧的陆源碎屑岩共同充填了辽吉地区这一古元古代弧后盆地。更为重要的是,不断深入的锆石UPb年代学显示,狼林陆块主要由古元古代岩石组成,太古宙岩石比例极为有限,而同样的古元古代地质记录在胶辽吉带以北的龙岗陆块中则非常罕见[7881]。这一事实强有力地证明,狼林陆块在古元古代时为一活动大陆边缘,而胶辽吉带以北的龙岗陆块在古元古代时则处于内陆地区。本文的岩石成因学研究成果支持辽吉地区弧后盆地构造模型。此外,辽吉地区的弧后盆地属性也得到了前人对区域内同期变质基性岩(包括基性火山岩和侵入岩)相关研究的支持[24,49]。
图12古元古代早期辽吉地区构造环境示意图
Fig.12Schematic Illustration Showing Tectonic
Environment of LiaoningJilin Region During Early Paleoproterozoic
前人关于裂谷和岛弧的争论往往是在讨论辽吉地区本身是否标志着消失了的大洋(缝合带)[24,26,29,31,50,52,7075]。而实际上发生俯冲的洋壳远在东部陆块东南(即现今朝鲜半岛东南),并不位于辽吉地区:古元古代时期,东部陆块东侧的岩浆弧大致位于朝鲜半岛(图12),即朝鲜岛弧;辽吉地区处于朝鲜岛弧(大陆边缘弧)的弧后区域[82]。结合区域地质资料,本文的岩石成因学研究成果不支持前人构造演化观点。换而言之,无论是前人的裂谷观点还是岛弧观点,它们均认为辽吉活动带代表主大洋所在位置,但本研究认为辽吉活动带并不代表主大洋的存在,古元古代时主大洋应该位于华北东部陆块东南(即现今朝鲜半岛东南)。辽吉地区存在海相沉积,但辽吉弧后盆地最终是否拉张形成玄武质洋壳还不确定,这仍需进一步深入研究。
古元古代早期(2.2~2.3 Ga),東部陆块以东的大洋岩石圈板块向西北方向俯冲于东部陆块之下[82],洋壳的持续俯冲导致弧后伸展,进而在大陆岛弧后侧产生2.2~2.3 Ga期间的辽吉弧后盆地(图11),弧后伸展作用导致大陆岩石圈部分熔融形成花岗岩和基性岩,并在后期地体拼贴过程中遭受到不同程度的变质变形。大陆边缘弧(朝鲜弧)一侧的火山碎屑岩和内陆一侧的陆源碎屑岩分别从两侧经搬运沉积在辽吉弧后盆地中,最终形成了以火山碎屑岩为主的南辽河—集安群和以陆源碎屑岩为主的北辽河—老岭群。
6结语
(1)辽东营口—辽阳地区保存有较好的古元古代地质记录,其中建一花岗岩形成于(2 322±18)Ma,隆昌变质辉绿岩形成于(2 335±21)Ma,蒜盘峪变质辉长岩形成于(2 353±22)Ma。
(2)建一花岗岩为钙碱性I型花岗岩,源自太古宙古老地壳部分熔融;隆昌变质辉绿岩形成自新太古代富集程度不高的地幔部分熔融,并在上升过程中受到年轻地壳的改造;蒜盘峪变质辉长岩是古太古代—中太古代富集地幔部分熔融的产物。三者均具有俯冲带岩浆特征。
(3)古元古代早期(2.2~2.3 Ga),辽吉地区处于大陆弧后盆地构造环境,弧后伸展作用导致大陆岩石圈部分熔融产生花岗岩和基性岩,在后期的地体拼贴过程中,两者遭受到不同程度的变质变形,进而形成了条痕状花岗岩和变质基性岩。
参考文献:
References:
[1]ZHAO G C,CAWOOD P A,WILDE S A,et al.Metamorphism of Basement Rocks in the Central Zone of the North China Craton:Implications for Paleoproterozoic Tectonic Evolution[J].Precambrian Research,2000,103(1/2):5588.
[2]ZHAO G C.Palaeoproterozoic Assembly of the North China Craton[J].Geological Magazine,2001,138(1):8791.
[3]ZHENG J P,GRIFFIN W L,OREILLY S Y,et al.36 Ga Lower Crust in Central China:New Evidence on the Assembly of the North China Craton[J].Geology,2004,32(3):229232.
[4]GUO J H,SUN M,CHEN F K,et al.SmNd and SHRIMP UPb Zircon Geochronology of Highpressure Granulites in the Sanggan Area,North China Craton:Timing of Paleoproterozoic Continental Collision[J].Journal of Asian Earth Sciences,2005,24(5):629642.
[5]WU F Y,ZHAO G C,WILDE S A,et al.Nd Isotopic Constraints on Crustal Formation in the North China Craton[J].Journal of Asian Earth Sciences,2005,24(5):523545.
[6]ZHAI M G,LI T S,PENG P,et al.Precambrian Key Tectonic Events and Evolution of the North China Craton[J].Geological Society,London,Special Publications,2010,338(1):235262.
[7]KUSKY T M.Geophysical and Geological Tests of Tectonic Models of the North China Craton[J].Gondwana Research,2011,20(1):2635.
[8]ZHAI M G,SANTOSH M.Metallogeny of the North China Craton:Link with Secular Changes in the Evolving Earth[J].Gondwana Research,2013,24(1):275297.
[9]ZHAI M G.Multistage Crustal Growth and Cratonization of the North China Craton[J].Geoscience Frontiers,2014,5(4):457469.
[10]KUSKY T M,POLAT A,WINDLEY B F,et al.Insights into the Tectonic Evolution of the North China Craton Through Comparative Tectonic Analysis:A Record of Outward Growth of Precambrian Continents[J].Earthscience Reviews,2016,162:387432.
[11]ZHAO G C,SUN M,WILDE S A,et al.Late Archean to Paleoproterozoic Evolution of the North China Craton:Key Issues Revisited[J].Precambrian Research,2005,136(2):177202.
[12]遼宁省地质矿产勘查局.辽宁省区域地质志[M].北京:地质出版社,1989.
Liaoning Bureau of Geology and Mineral Resources Exploration.Regional Geology in Liaoning Province[M].Beijing:Geological Publishing House,1989.
[13]WU F Y,YANG J H,WILDE S A,et al.Geochronology,Petrogenesis and Tectonic Implications of Jurassic Granites in the Liaodong Peninsula,NE China[J].Chemical Geology,2005,221(1/2):127156.
[14]ZHAO G C,ZHAI M G.Lithotectonic Elements of Precambrian Basement in the North China Craton:Review and Tectonic Implications[J].Gondwana Research,2013,23(4):12071240.
[15]张秋生.辽东半岛早期地壳与矿床[M].北京:地质出版社,1988.
ZHANG Qiusheng.Early Crust and Mineral Deposits of Liaodong Peninsula[M].Beijing:Geological Publishing House,1988.
[16]刘光启.辽吉东部层状混合岩的成因[J].吉林地质,1989(4):4249.
LIU Guangqi.On Origin of the Bedded Migmatite in Eastern Parts of LiaoningJilin Provinces[J].Jilin Geology,1989(4):4249.
[17]赵凤顺,胡平.虎皮峪条痕状花岗质岩石特征及成因探讨[J].辽宁地质,1989,6(4):298311.
ZHAO Fengshun,HU Ping.Features and Origin of Streaky Graniticrocks from Hupiyu[J].Liaoning Geology,1989,6(4):298311.
[18]曲洪祥,张永,雷广新,等.试论辽东地区古元古代壳幔混合杂岩[J].辽宁地质,2000,17(3):199205.
QU Hongxiang,ZHANG Yong,LEI Guangxin,et al.On the Paleoproterozoic Crustmantle Mixed Complex in East Liaoning[J].Liaoning Geology,2000,17(3):199205.
[19]路孝平,吴福元,张艳斌,等.吉林南部通化地区古元古代辽吉花岗岩的侵位年代与形成构造背景[J].岩石学报,2004,20(3):381392.
LU Xiaoping,WU Fuyuan,ZHANG Yanbin,et al.Emplacement Age and Tectonic Setting of the Paleoproterozoic Liaoji Granites in Tonghua Area,Southern Jilin Province[J].Acta Petrologica Sinica,2004,20(3):381392.
[20]郝德峰,李三忠,赵国春,等.辽吉地区古元古代花岗岩成因及对构造演化的制约[J].岩石学报,2004,20(6):14091416.
HAO Defeng,LI Sanzhong,ZHAO Guochun,et al.Origin and Its Constraint to Tectonic Evolution of Paleoproterozoic Granitoids in the Eastern Liaoning and Jilin Province,North China[J].Acta Petrologica Sinica,2004,20(6):14091416.
[21]杨明春,陈斌,闫聪.华北克拉通胶—辽—吉带古元古代条痕状花岗岩成因及其构造意义[J].地球科学与环境学报,2015,37(5):3151.
YANG Mingchun,CHEN Bin,YAN Cong.Petrogenesis of Paleoproterozoic Gneissic Granites from JiaoLiaoJi Belt of North China Craton and Their Tectonic Implications[J].Journal of Earth Sciences and Environment,2015,37(5):3151.
[22]刘永达,邴志波,董景超.辽东半岛早元古宙海相拉斑玄武岩特征及其意义[J].辽宁地质,1989,6(4):289297.
LIU Yongda,BING Zhibo,DONG Jingchao.Features and Significance of Marine Tholeiite of Early Proterozoic in Liaoning Peninsular[J].Liaoning Geology,1989,6(4):289297.
[23]王艺芬,徐贵忠,佘宏全,等.辽东地区早元古代火山岩特征及其形成的动力学背景[J].现代地质,2005,19(3):315324.
WANG Yifen,XU Guizhong,SHE Hongquan,et al.Characteristics of the Early Proterozoic Volcanic Rocks and Its Dynamic Background of Formation in the Liaodong Area[J].Geoscience,2005,19(3):315324.
[24]MENG E,LIU F L,LIU P H,et al.Petrogenesis and Tectonic Significance of Paleoproterozoic Metamafic Rocks from Central Liaodong Peninsula,Northeast China:Evidence from Zircon UPb Dating and Insitu LuHf Isotopes,and Wholerock Geochemistry[J].Precambrian Research,2014,247:92109.
[25]LI Z,CHEN B,WANG J L.Geochronological Framework and Geodynamic Implications of Mafic Magmatism in the Liaodong Peninsula and Adjacent Regions,North China Craton[J].Acta Geologica Sinica:English Edition,2016,90(1):138153.
[26]WANG X P,PENG P,WANG C,et al.Petrogenesis of the 2 115 Ma Haicheng Mafic Sills from the Eastern North China Craton:Implications for an Intracontinental Rifting[J].Gondwana Research,2016,39:347364.
[27]賀高品,叶慧文.辽东—吉南地区早元古代两种类型变质作用及其构造意义[J].岩石学报,1998,14(2):152162.
HE Gaopin,YE Huiwen.Two Types of Early Proterozoic Metamorphism and Its Tectonic Significance in Eastern Liaoning and Southern Jilin Areas[J].Acta Petrologica Sinica,1998,14(2):152162.
[28]路孝平,吴福元,郭敬辉,等.通化地区古元古代晚期花岗质岩浆作用与地壳演化[J].岩石学报,2005,21(3):721736.
LU Xiaoping,WU Fuyuan,GUO Jinghui,et al.Late Paleoproterozoic Granitic Magmatism and Crustal Evolution in the Tonghua Region,Northeast China[J].Acta Petrologica Sinica,2005,21(3):721736.
[29]LUO Y,SUN M,ZHAO G C,et al.LAICPMS UPb Zircon Ages of the Liaohe Group in the Eastern Block of the North China Craton:Constraints on the Evolution of the JiaoLiaoJi Belt[J].Precambrian Research,2004,134(3/4):349371.
[30]LUO Y,SUN M,ZHAO G C,et al.A Comparison of UPb and Hf Isotopic Compositions of Detrital Zircons from the North and South Liaohe Groups:Constraints on the Evolution of the JiaoLiaoJi Belt,North China Craton[J].Precambrian Research,2008,163(3/4):279306.
[31]LU X P,WU F Y,GUO J H,et al.Zircon UPb Geochronological Constraints on the Paleoproterozoic Crustal Evolution of the Eastern Block in the North China Craton[J].Precambrian Research,2006,146(3/4):138164.
[32]WAN Y S,SONG B,LIU D Y,et al.SHRIMP UPb Zircon Geochronology of Palaeoproterozoic Metasedimentary Rocks in the North China Craton:Evidence for a Major Late Palaeoproterozoic Tectonothermal Event[J].Precambrian Research,2006,149(3/4):249271.
[33]XIE L W,YANG J H,WU F Y,et al.PbSL Dating of Garnet and Staurolite:Constraints on the Paleoproterozoic Crustal Evolution of the Eastern Block,North China Craton[J].Journal of Asian Earth Sciences,2011,42(1/2):142154.
[34]孟恩,刘福来,刘平华,等.辽东半岛东北部宽甸地区南辽河群沉积时限的确定及其构造意义[J].岩石学报,2013,29(7):24652480.
MENG En,LIU Fulai,LIU Pinghua,et al.Depositional Ages and Tectonic Implications for South Liaohe Group from Kuandian Area in Northeastern Liaodong Peninsula,Northeast China[J].Acta Petrologica Sinica,2013,29(7):24652480.
[35]秦亚,陈丹丹,梁一鸿,等.吉林南部通化地区集安群的年代学[J].地球科学,2014,39(11):14871499.
QIN Ya,CHEN Dandan,LIANG Yihong,et al.Geochronology of Jian Group in Tonghua Area,Southern Jilin Province[J].Earth Science,2014,39(11):14871499.
[36]HU G Y,LI Y H,FAN C F,et al.In situ LAMCICPMS Boron Isotope and Zircon UPb Age Determinations of Paleoproterozoic Borate Deposits in Liaoning Province,Northeastern China[J].Ore Geology Reviews,2015,65:11271141.
[37]李壯,陈斌,刘经纬,等.辽东半岛南辽河群锆石UPb年代学及其地质意义[J].岩石学报,2015,31(6):15891605.
LI Zhuang,CHEN Bin,LIU Jingwei,et al.Zircon UPb Ages and Their Implications for the South Liaohe Group in the Liaodong Peninsula,Northeast China[J].Acta Petrologica Sinica,2015,31(6):15891605.
[38]LI Z,CHEN B,WEI C J,et al.Provenance and Tectonic Setting of the Paleoproterozoic Metasedimentary Rocks from the Liaohe Group,JiaoLiaoJi Belt,North China Craton:Insights from Detrital Zircon UPb Geochronology,Wholerock SmNd Isotopes,and Geochemistry[J].Journal of Asian Earth Sciences,2015,111:711732.
[39]王惠初,任云伟,陆松年,等.辽吉古元古代造山带的地层单元划分与构造属性[J].地球学报,2015,36(5):583598.
WANG Huichu,REN Yunwei,LU Songnian,et al.Stratigraphic Units and Tectonic Setting of the Paleoproterozoic LiaoJi Orogen[J].Acta Geoscientica Sinica,2015,36(5):583598.
[40]LI S Z,ZHAO G C.SHRIMP UPb Zircon Geochronology of the Liaoji Granitoids:Constraints on the Evolution of the Paleoproterozoic JiaoLiaoJi Belt in the Eastern Block of the North China Craton[J].Precambrian Research,2007,158(1/2):116.
[41]胡古月,范昌福,李延河,等.辽东明安硼镁矿床混合花岗岩的锆石UPb年龄及对成矿时代的制约[J].矿床地质,2014,33(2):397405.
HU Guyue,FAN Changfu,LI Yanhe,et al.Zircon UPb Dating of Migmatitic Granites of Mingan Mgborate Deposit in Kuandian Area,Eastern Liaoning Province,and Its Constrains on Mineralization Age[J].Mineral Deposits,2014,33(2):397405.
[42]陈斌,李壮,王家林,等.辽东半岛~2.2 Ga岩浆事件及其地质意义[J].吉林大学学报:地球科学版,2016,46(2):303320.
CHEN Bin,LI Zhuang,WANG Jialin,et al.Liaodong Peninsula ~22 Ga Magmatic Event and Its Geological Significance[J].Journal of Jilin University:Earth Science Edition,2016,46(2):303320.
[43]ZHAI M G,ZHAO Y,ZHAO T P.Main Tectonic Events and Metallogeny of the North China Craton[M].Singapore:Springer,2016.
[44]蔡剑辉,阎国翰,牟保磊,等.辽宁盖县梁屯—矿洞沟碱性正长岩杂岩体的UPb和SmNd年龄及其地质意义[J].岩石学报,2002,18(3):349354.
CAI Jianhui,YAN Guohan,MOU Baolei,et al.UPb and SmNd Isotopic Ages of an Alkaline Syenite Complex Body in LiangtunKuangdonggou,Gai County,Liaoning Province,China and Their Geological Significance[J].Acta Petrologica Sinica,2002,18(3):349354.
[45]路孝平,吳福元,林景仟,等.辽东半岛南部早前寒武纪花岗质岩浆作用的年代学格架[J].地质科学,2004,39(1):123138.
LU Xiaoping,WU Fuyuan,LIN Jingqian,et al.Geochronological Successions of the Early Precambrian Granitic Magmatism in Southern Liaoning Province and Its Constrains on Tectonic Evolution of the North China Craton[J].Chinese Journal of Geology,2004,39(1):123138.
[46]杨进辉,吴福元,谢烈文,等.辽东矿洞沟正长岩成因及其构造意义:锆石原位微区UPb年龄和Hf同位素制约[J].岩石学报,2007,23(2):263276.
YANG Jinhui,WU Fuyuan,XIE Liewen,et al.Petrogenesis and Tectonic Implications of Kuangdonggou Syenites in the Liaodong Peninsula,East North China Craton:Constraints from Insitu Zircon UPb Ages and Hf Isotopes[J].Acta Petrologica Sinica,2007,23(2):263276.
[47]杨明春,陈斌,闫聪.吉南地区古元古代双岔巨斑状花岗岩成因及其构造意义:岩石学、年代学、地球化学和SrNdHf同位素证据[J].岩石学报,2015,31(6):15731588.
YANG Mingchun,CHEN Bin,YAN Cong.Petrological,Geochronological,Geochemical and SrNdHf Isotopic Constraints on the Petrogenesis of the Shuangcha Paleoproterozoic Megaporphyritic Granite in the Southern Jilin Province:Tectonic Implications[J].Acta Petrologica Sinica,2015,31(6):15731588.
[48]于介江,杨德彬,冯虹,等.辽南海城斜长角闪岩原岩的形成时代:锆石LAICPMS UPb定年证据[J].世界地质,2007,26(4):391396,408.
YU Jiejiang,YANG Debin,FENG Hong,et al.Chronology of Amphibolite Protolith in Haicheng of Southern Liaoning:Evidence from LAICPMS Zircon UPb Dating[J].Global Geology,2007,26(4):391396,408.
[49]王惠初,陆松年,初航,等.辽阳河栏地区辽河群中变质基性熔岩的锆石UPb年龄与形成构造背景[J].吉林大学学报:地球科学版,2011,41(5):13221334.
WANG Huichu,LU Songnian,CHU Hang,et al.Zircon UPb Age and Tectonic Setting of Metabasalts of Liaohe Group in Helan Area,Liaoyang,Liaoning Province[J].Journal of Jilin University:Earth Science Edition,2011,41(5):13221334.
[50]LI Z,CHEN B.Geochronology and Geochemistry of the Paleoproterozoic Metabasalts from the JiaoLiaoJi Belt,North China Craton:Implications for Petrogenesis and Tectonic Setting[J].Precambrian Research,2014,255:653667.
[51]秦亚,梁一鸿,张青伟,等.辽东地区什司县变质基性岩墙群的LAICPMS锆石UPb测年及其意义[J].矿物学报,2015,35(4):540544.
QIN Ya,LIANG Yihong,ZHANG Qingwei,et al.LAICPMS Zircon UPb Age of Plagioclase Amphibolite from Shensixian Mafic Dyke Swarm in Liaodong Area,China and Its Significance[J].Acta Mineralogica Sinica,2015,35(4):540544.
[52]YUAN L L,ZHANG X H,XUE F H,et al.Two Episodes of Paleoproterozoic Mafic Intrusions from Liaoning Province,North China Craton:Petrogenesis and Tectonic Implications[J].Precambrian Research,2015,264:119139.
[53]JACKSON S E,PEARSON N J,GRIFFIN W L,et al.The Application of Laser Ablationinductively Coupled Plasmamass Spectrometry to Insitu UPb Zircon Geochronology[J].Chemical Geology,2004,211(1/2):4769.
[54]SLAMA J,KOSLER J,CONDON D J,et al.Plesovice Zircon:A New Natural Reference Material for UPb and Hf Isotopic Microanalysis[J].Chemical Geology,2008,249(1/2):135.
[55]LUDWIG K R.Users Manual for Isoplot/Ex Rev.249:A Geochronological Toolkit for Microsoft Excel[R].Berkeley:Berkeley Geochronology Center,2001.
[56]SUN S S,MCDONOUGH W F.Chemical and Isotopic Systematics of Oceanic Basalts:Implications for Mantle Composition and Processes[J].Geological Society,London,Special Publications,1989,42:313345.
[57]DEPAOLO D J.Neodymium Isotopes in the Colorado Front Range and Crustmantle Evolution in the Proterozoic[J].Nature,1981,291:193196.
[58]WHALEN J B,CURRIE K L,CHAPPELL B W.Atype Granites:Geochemical Characteristics,Discrimination and Petrogenesis[J].Contributions to Mineralogy and Petrology,1987,95(4):407419.
[59]李三忠,楊振升.胶辽地块古元古代花岗岩类型及成因[J].西北地质,1997,18(3):2126.
LI Sanzhong,YANG Zhensheng.Types and Genesis of Paleoproterozoic Granites in the JiaoLiao Massif[J].Northwestern Geology,1997,18(3):2126.
[60]PEARCE J A,HARRIS N B W,TINDLE A G.Trace Element Discrimination Diagrams for the Tectonic Interpretation of Granitic Rocks[J].Journal of Petrology,1984,25(4):956983.
[61]MIDDLEMOST E A K.Naming Materials in the Magma/Igneous Rock System[J].Earthscience Reviews,1994,37(3/4):215224.
[62]PECCERILLO A,TAYLOR S R.Geochemistry of Eocene Calcalkaline Volcanic Rocks from the Kastamonu Area,Northern Turkey[J].Contributions to Mineralogy and Petrology,1976,58(1):6381.
[63]MANIAR P D,PICCOLI P M.Tectonic Discrimination of Granitoids[J].Geological Society of America Bulletin,1989,101(5):635643.
[64]FLOYD P A,WINCHESTER J A.Magma Type and Tectonic Setting Discrimination Using Immobile Elements[J].Earth and Planetary Science Letters,1975,27(2):211218.
[65]PEARCE J A.Trace Element Characteristics of Lavas from Destructive Plate Boundaries[M]∥THORPE R S.Andesites:Orogenic Andesites and Related Rocks.New York:John Wiley and Sons,1982:525548.
[66]BRIQUEU L,BOUGAULT H,JORON J L.Quantification of Nb,Ta,Ti and V Anomalies in Magmas Associated with Subduction Zones:Petrogenetic Implications[J].Earth and Planetary Science Letters,1984,68(2):297308.
[67]GREEN T H.Significance of Nb/Ta as an Indicator of Geochemical Processes in the Crustmantle System[J].Chemical Geology,1995,120(3/4):347359.
[68]WOOD D A.The Application of a ThHfTa Diagram to Problems of Tectonomagmatic Classification and to Establishing the Nature of Crustal Contamination of Basaltic Lavas of the British Tertiary Volcanic Province[J].Earth and Planetary Science Letters,1980,50(1):1130.
[69]PEARCE J A.Geochemical Fingerprinting of Oceanic Basalts with Applications to Ophiolite Classification and the Search for Archean Oceanic Crust[J].Lithos,2008,100(1/2/3/4):1448.
[70]陳荣度.一个早元古代裂谷盆地:辽东裂谷[J].辽宁地质,1984,1(2):125133.
CHEN Rongdu.A Paleoproterozoic Rift Basin:Liaodong Rift[J].Liaoning Geology,1984,1(2):125133.
[71]张秋生.中国早前寒武纪地质及成矿作用[M].长春:吉林人民出版社,1984.
ZHANG Qiusheng.Geology and Metallogeny of the Early Precambrian in China[M].Changchun:Jilin Peoples Publishing House,1984.
[72]刘永江,李三忠.辽东海城—大石桥—吉洞地区早元古代花岗岩[J].辽宁地质,1996,13(1):1018.
LIU Yongjiang,LI Sanzhong.Paleoproterozoic Granite in HaichengDashiqiaoJidong Area,Eastern Liaoning[J].Liaoning Geology,1996,13(1):1018.
[73]LI S Z,ZHAO G C,SUN M,et al.Deformation History of the Paleoproterozoic Liaohe Assemblage in the Eastern Block of the North China Craton[J].Journal of Asian Earth Sciences,2005,24(5):659674.
[74]白瑾,黄学光,戴凤岩,等.中国前寒武纪地壳演化[M].北京:地质出版社,1993.
BAI Jin,HUANG Xueguang,DAI Fengyan,et al.Precambrian Crustal Evolution of China[M].Beijing:Geological Publishing House,1993.
[75]FAURE M,LIN W,MONIE P,et al.Palaeoproterozoic Arc Magmatism and Collision in Liaodong Peninsula (Northeast China)[J].Terra Nova,2004,16(2):7580.
[76]
瘙 塁 ENGOR A M C.Plate Tectonics and Orogenic Research After 25 Years:A Tethyan Perspective[J].Earthscience Reviews,1990,27(1/2):1201.
[77]CONDIE K C.Plate Tectonics and Crustal Evolution[M].4th ed.Oxford:ButterworthHeinemann,1997.
[78]ZHAO G C,CAO L,WILDE S A,et al.Implications Based on the First SHRIMP UPb Zircon Dating on Precambrian Granitoid Rocks in North Korea[J].Earth and Planetary Science Letters,2006,251(3/4):365379.
[79]ZHAI M G,GUO J H,PENG P,et al.UPb Zircon Age Dating of a Rapakivi Granite Batholith in Rangnim Massif,North Korea[J].Geological Magazine,2007,144(3):547552.
[80]吳福元,李秋立,杨正赫,等.朝鲜北部狼林地块构造归属与地壳形成时代[J].岩石学报,2016,32(10):29332947.
WU Fuyuan,LI Qiuli,YANG Jonghyok,et al.Crustal Growth and Evolution of the Rangnim Massif,Northern Korean Peninsula[J].Acta Petrologica Sinica,2016,32(10):29332947.
[81]赵磊,张艳斌,杨正赫,等.朝鲜狼林地块东南缘太古宙岩石及其对古元古代构造热事件的响应[J].岩石学报,2016,32(10):29482964.
ZHAO Lei,ZHANG Yanbin,YANG Zhenghe,et al.Archean Rocks at the Southeastern Margin of the Rangnim Massif,Northern Korean Peninsula,and Their Response to Paleoproterozoic Tectonothermal Event[J].Acta Petrologica Sinica,2016,32(10):29482964.
[82]PENG P,WANG X P,WINDLEY B F,et al.Spatial Distribution of ~1 9501 800 Ma Metamorphic Events in the North China Craton:Implications for Tectonic Subdivision of the Craton[J].Lithos,2014,202/203:250266.