华北克拉通新太古代板块俯冲作用:来自山西云中山地区变质高镁火成岩组合的证据   总被引：3，自引：3，他引：0  

王惠初  康健丽  肖志斌  相振群  李建荣  孙义伟  施建荣  张家辉 《岩石学报》2018,34(4):1099-1118

在华北克拉通中部的山西云中山地区,新太古代花岗闪长质片麻岩中存在一些超镁铁质岩-镁铁质岩块及由斜长角闪岩、角闪变粒岩、石英岩和石榴夕线黑云片岩等岩石类型构成的变质表壳岩残片,其中的超镁铁质-镁铁质岩、斜长角闪岩和角闪变粒岩构成一套高镁火成岩组合。超镁铁质岩已变质为橄榄绿泥阳起片岩等岩石类型,呈变余斑状结构,橄榄石斑晶仍有保存;岩石SiO_2含量为39.22%～44.99%,Al_2O_3为8.82%～13.47%,Mg O为19.24%～22.13%,Na_2O+K_2O=0.71%～1.11%,CaO为5.75%～8.42%;Al_2O_3/TiO_2=14.8～17.4,CaO/Al_2O_3=0.60～0.84;化学成分上与科马提岩有一定的相似性。与之紧密伴生的斜长角闪岩也具有高镁特征,Mg O含量为11.28%～15.09%,铝、硅和碱质均偏低,具正铕异常,显示堆晶辉长岩的特征。非高镁斜长角闪岩有相对高的铝、硅和碱质,其原岩应为钙碱性玄武岩。角闪变粒岩样品的SiO_2含量为54.21%～55.71%,Al_2O_3为14.24%～15.49%,Mg O为6.26%～8.28%,Fe OT/Mg O=1.11～1.58,高钠低钾,Na_2O+K_2O=3.7%～4.78%,Na_2O/K_2O=5.15%～13.13,Mg#=53.0～61.5,属于高镁安山岩。由超镁铁质质岩-斜长角闪岩-角闪变粒岩构成的变质高镁火山岩组合具有钙碱性系列趋势。超镁铁质岩稀土元素含量总量较低,具有轻稀土富集和重稀土亏损的稀土型式;斜长角闪岩与超镁铁质岩比较,除富集大离子亲石元素和Cr、Ni明显较低外,具有相似的微量元素图谱形态。三种岩石类型在微量元素蛛网图上均显示出Ta、Nb、Ti负异常和Pb正异常。野外产状和岩石地球化学特征表明超镁铁质岩和高镁斜长角闪岩属于阿拉斯加型杂岩体,角闪变粒岩属于赞岐岩质高镁安山岩。在Zr/Nb-Nb/Th和Nb/Y-Zr/Y构造环境判别图解上显示出与俯冲相关的演化趋势,在Hf-Th-Ta、Nb/La-(La/Sm)N和Th/Yb-Nb/Yb图解上也落在岛弧钙碱性岩石区域。以上特征表明高镁火成岩组合形成于与板块俯冲相关的岛弧构造背景。野外地质关系和锆石U-Pb年龄限定高镁火成岩组合形成时代在～2.5Ga。云中山地区阿拉斯加型镁铁质-超镁铁质杂岩与赞岐岩质高镁安山岩共生,表明该地区存在新太古代的板块俯冲作用,为太古宙存在板块构造机制提供了新证据。  相似文献   

Precambrian Tectonic Affinity of the Southern Langshan Area, Northeastern Margin of the Alxa Block: Evidence from Zircon U-Pb Dating and Lu-Hf Isotopes     

NIU Pengfei  QU Junfeng  ZHANG Jin  ZHANG Beihang  ZHAO Heng 《《地质学报》英文版》2022,96(5):1516-1533

The Alxa Block is the westernmost part of the North China Craton (NCC), and is regarded as one of the basement components of the NCC. Its geological evolution is of great significance for the understanding of the NCC. However, the Precambrian basement of the Alxa Block is still poorly studied. In this study, we present new in situ LA-ICP-MS zircon U-Pb and Lu-Hf isotope data from the Diebusige Metamorphic Complex (DMC) which located in the eastern Alxa Block. Field and petrological studies show that the DMC consists mainly of metamorphic supracrustal rocks and minor metamorphic plutonic rocks and has experienced amphibolite-granulite facies metamorphism. Zircon U-Pb dating results suggested that the amphibolite sample yields a crystallization age of 2636 ± 14 Ma and metamorphic ages of 2517–2454 Ma and 1988–1952 Ma, proving the existence of exposed Archean rocks in the Langshan area and indicating that late Neoarchean to Paleoproterozoic metamorphic events existed in the Alxa Block. Two paragneiss samples show that the magmatic detrital zircons from the DMC yield 207Pb/206Pb ages ranging from 2.48 Ga to 2.10 Ga with two youngest peaks at 2.13 Ga and 2.16 Ga, respectively, and they were also overprinted by metamorphic events at 1.97–1.90 Ga and 1.89–1.79 Ga. Compilation of U-Pb ages of magmatic detrital and metamorphic zircons suggested that the main part of the DMC may have been formed at 2.1–2.0 Ga. Zircon Lu-Hf isotope data show that the source materials of the main part of the DMC were originated from the reworking of ancient Archean crust (3.45–2.78 Ga). The Hf isotope characteristics and the tectonothermal event records exhibit different evolution history with the Khondalite Belt and the Yinshan Block and the other basements of the Alxa Block, indicating that the Langshan was likely an independent terrain before the middle Paleoproterozoic and was subjected to the middle to late Paleoproterozoic tectonothermal events with the Khondalite Belt as a whole.  相似文献   

鲁西地区新太古代地壳增生事件：来自花岗岩和二长花岗岩U-Pb年代学、Hf同位素和岩石地球化学的证据     

王跃  周奇明  张金龙  周光峰 《吉林大学学报(地球科学版)》2022,52(2):463-485

鲁西地区是全球完整保存新太古代早期TTG（英云闪长岩-奥长花岗岩-花岗闪长岩）和绿岩带的区域,是研究太古宙岩浆演化类型和太古宙时期壳幔作用以及构造模式的典型区域。本文在野外地质调查的基础上,通过年代学、Hf同位素和岩石地球化学等手段,探讨了鲁西地区新太古代花岗岩和二长花岗岩的地球化学特征和形成背景。鲁西地区新太古代花岗岩和二长花岗岩U-Pb年龄主要为2 537和2 566 Ma。花岗岩（TA1802）εHf (t)值为-1.4～2.9,平均值为0.65,二阶段模式年龄约为2.9 Ga;二长花岗岩（TA1812）εHf (t) 值为-0.4～2.7,平均值为1.31,二阶段模式年龄为 3 073～2 886 Ma,平均值约为2.9 Ga;二长花岗岩（TA1817）εHf (t) 值为0.3～4.7,平均值为3.35,二阶段模式年龄为3 032～2 762 Ma,平均值约为2.8 Ga。在εHf (t)-t 图解上,鲁西地区新太古代花岗岩和二长花岗岩年龄演化线均落在2.9～2.8 Ga地壳演化线上,且与二阶段模式年龄大致相同,即表明鲁西地区新太古代花岗岩和二长花岗岩源于2.9～2.8 Ga的古老地壳重融。鲁西地区新太古代花岗岩和二长花岗岩均表现为高w(SiO2)、w(Al2O3)和富Na2O特征,大部分属于准铝质岩石。稀土元素球粒陨石标准化分布型式上,均表现为轻稀土元素（LREE）富集和重稀土元素（HREE）亏损,且中重稀土元素出现分馏。花岗岩样品中,有两个样品（TA1801-1与TA1824）表现出Ta富集,其余样品均表现为K、Rb、Ba和Th等大离子亲石元素富集,Nb、Ta、Ti亏损。二长花岗岩也同样表现为K、Rb、Ba和Th等大离子亲石元素富集,Nb、Ta、Ti亏损,部分熔融残余矿物存在石榴石、金红石以及少量斜长石、角闪石。根据上述地球化学特征, 并结合区域地质特征,鲁西地区新太古代花岗岩和二长花岗岩构造背景为同碰撞背景,该构造模式是大陆地壳有效增生。  相似文献   

Archean (about 2500 Ma) anatexis in eastern North China Block     

《China Geology》2021,4(2):215-229

Two Neoarchean alkaline feldspar-rich granites sourced from partially melted granulite-facies granodioritic orthogneiss have been here recognised in the eastern part of the North China Block (NCB). These poorly foliated granites have previously been assumed to be Mesozoic in age and never dated, and so their significance has not been recognised until now. The first granite (AG1) is a porphyritic syenogranite with megacrystic K-feldspar, and the second (AG2) is a quartz syenite with perthitic megacryst. Zircons from the granites yield LA-ICP-MS U-Pb ages of 2499 ± 10 Ma (AG1), and 2492 ± 28 Ma (AG2), which are slightly younger than the granodioritic orthogneiss that they intrude with a crystallisation U-Pb age of 2537 ± 34 Ma. The younger granites have higher assays for SiO₂ (71.91% for AG1 and 73.22% for AG2) and K₂O (7.52% for AG1 and 8.37% for AG2), and much lower assays for their other major element than the granodioritic orthogneiss. All of the granodioritic orthogneiss and granite samples have similar trace element patterns, with depletion in Th, U, Nb, and Ti and enrichment in Rb, Ba, K, La, Ce, and P. This indicates that the granites are derived from the orthogneiss as partial melts. Although they exhibit a similar REE pattern, the granites have much lower total REE contents (30.97×10⁻⁶ for AG1, and 25.93×10⁻⁶ for AG2), but pronounced positive Eu anomalies (Eu/Eu* = 8.57 for AG1 and 27.04 for AG2). The granodioritic orthogneiss has an initial ⁸⁷Sr/⁸⁶Sr ratio of 0.70144, εNd(t) value of 3.5, and εHf(t) values ranging from −3.2 to +2.9. The orthogneiss is a product of fractional crystallisation from a dioritic magma, which was derived from a mantle source contaminated by melts derived from a felsic slab. By contrast, the AG1 sample has an initial ⁸⁷Sr/⁸⁶Sr ratio of 0.6926 that is considered too low in value, εNd(t) value of 0.3, and εHf(t) values between +0.57 and +3.82; whereas the AG2 sample has an initial ⁸⁷Sr/⁸⁶Sr ratio of 0.70152, εNd(t) value of 1.3, and εHf(t) values between +0.5 and +14.08. These assays indicate that a Sr-Nd-Hf isotopic disequilibrium exists between the granite and granodioritic orthogneiss. The elevated εHf(t) values of the granites can be explained by the involvement of Hf-bearing minerals, such as orthopyroxene, amphibole, and biotite, in anatectic reactions in the granodioritic orthogneiss. Based on the transitional relationship between the granites and granodioritic orthogneiss and the geochemical characteristics mentioned above, it is concluded that the granites are the product of rapid partial-melting of the granodioritic orthogneiss after granulite-facies metamorphism, and their crystallisation age of about 2500 Ma provides the minimum age of the metamorphism. This about 2500 Ma tectonic-metamorphic event in NCB is similar to the other cratons in India, Antarctica, northern and southern Australia, indicating a possible connection between these cratons during the Neoarchean.  相似文献   

坦桑尼亚盖塔(Geita)绿岩带型金矿矿床地质特征          下载免费PDF全文

龚鹏辉  刘晓阳  王杰  许康康  左立波  孙凯  刘宇 《地质找矿论丛》2015,30(S1):93-97

盖塔(Geita)金矿是坦桑尼亚重要的绿岩带型金矿之一。文章阐述了矿床地质背景、矿床地质特征,以及矿床同位素年代特征,并对矿床成矿模式进行了对比。在此基础上认为盖塔金矿以块状黄铁矿和浸染状黄铁矿的矿化为主,成矿时代约为2644~2680Ma,属于太古宙热液型金矿床,具有明显的"层控"特征,后生成矿模式可能是盖特金矿的矿床成因。  相似文献   

五台山新太古代绿岩带中高镁安山岩（HMA）的化学特征   总被引：2，自引：0，他引：2       下载免费PDF全文

张永忠  刘翠  邓晋福  李德胜  周继华  赵凤清  赵祯祥  孙占亮 《地学前缘》2012,19(5):187-194

采用高镁安山岩（HMA）新的分类方法,描述了五台地区新太古代绿岩带中HMA的化学特征,并与实验的HMA以及自然界中典型的HMA（日本的Chichijima地区HMA和Setouchi地区HMA）进行了对比,显示该区HMA具有与上述HMA类似的化学特征。初步认为五台新太古代HMA产于洋俯冲带的环境,进而表明板块构造理论的适用时间范围可推演到新太古代。  相似文献   

吉东南新太古代晚期片麻岩类的时代、成因及其对早期地壳形成演化的制约     

王朝阳  孟恩  李壮  李艳广  靳梦琪 《吉林大学学报(地球科学版)》2018,48(3):587-625

吉林省东南部通化地区广泛出露早前寒武纪花岗质片麻岩类,其岩石组成、形成时代和成因对深化认识华北克拉通东北缘早期地壳形成演化历史具有重要意义。本文系统的岩石学、锆石U-Pb年代学、元素和Lu-Hf同位素地球化学等研究结果表明,这些花岗质片麻岩类按照SiO₂质量分数总体可划分为高硅和低硅两组：前者主要由二长花岗质片麻岩、奥长花岗质片麻岩及英云闪长质片麻岩组成,其原岩形成于2 549~2 557 Ma;而后者由石英二长闪长质片麻岩及花岗闪长岩质片麻岩组成,其原岩形成于2 534~2 552 Ma;并且两组岩石都含有约2 600 Ma的捕获锆石,共同遭受了约2 500 Ma变质作用的影响。地球化学分析结果显示,低硅岩组具有较高的MgO、CaO、Na₂O质量分数,属于高钾—中钾钙碱性系列,并且富集LREE、亏损HREE和HFSE;与之相比,高硅岩组则具有较低的MgO和CaO质量分数,显示更强烈的轻、重稀土元素分馏以及Nb、Ta、P、Ti等亏损的特征;但两者均具有较弱的正或负Eu异常。结合区域最新研究成果,认为研究区低硅和高硅两组岩石应具有相同的源区,其形成可能与大洋板片俯冲、岩浆底侵引起的地壳部分熔融作用有关。此外,两组岩石具有相似的ε_Hf（t）值（2.72~7.95）和模式年龄（2.86~2.55 Ga）,暗示区域主要存在新太古代晚期地壳生长事件;结合区域内变质火山岩的研究进展,认为吉林省东南部通化地区花岗质片麻岩类可能形成于活动大陆边缘的构造背景。  相似文献   

长白山新生代火山岩之下新太古代基底年代学及地球化学特征     

张宏涛  张兴洲  曾振  刘洋  崔维龙 《世界地质》2017,36(3):763-776

对长白山第四系玄武岩覆盖区零星出露的花岗质岩石和片麻岩进行LA-ICPMS锆石U-Pb年龄测定及地球化学分析,结果显示花岗质岩石的年龄为2 509~2 558 Ma;斜长角闪片麻岩的年龄为2 475~2 553 Ma。地球化学特征上,这些岩石均属奥长花岗岩-英云闪长岩-石英闪长岩系列(TTG),稀土元素配分模式图呈右倾型,轻重稀土元素分馏明显(LREE/HREE=3.85~34.48),白云母二长花岗岩具有铕的负异常(δEu=0.41~0.54),富集Rb、K、Th等元素,亏损Nb、Sr、P、Ti等元素;黑云斜长角闪石片麻岩具有铕负异常(δEu=0.67~0.76),富集Rb、K、La、Nd等元素,亏损Th、Nb、Sr、P、Yb等元素;花岗质片麻岩和黑云斜长片麻岩具有铕的弱负-正异常(δEu=0.87~3.3),富集Rb、K、Sr等元素,亏损Nb、Th、P等元素。年代学和地球化学特征与白山地块和和龙地块中的同类岩石基本一致,表明白山地块与和龙地块在晚太古代是同一个陆块(龙岗陆块),二者目前的分布格局是后期北东向左行断裂构造改造的结果。  相似文献   

Decoding Neoarchaean to Palaeoproterozoic tectonothermal events in the Rangnim Massif,North Korea: regional correlation and broader implications   总被引：1，自引：0，他引：1  

Xiaohui Zhang  Yanbin Zhang  Mingguo Zhai  Fuyuan Wu  Quanlin Hou  Lingling Yuan 《International Geology Review》2017,59(1):16-28

Any knowledge about Archaean to Palaeoproterozoic magmatic and metamorphic events in North Korea has the potential to make a significant difference to our understanding of the early tectonic configuration and evolution of East Asia. This zircon U–Pb dating and Hf isotopic study documents multiple Neoarchaean to Palaeoproterozoic tectonothermal events from the meta-igneous complex in the Machollyong ‘Group’ of the Rangnim Massif. Two tonalitic-trondjemitic gneiss samples record a crystallization age of meta-igneous protoliths at ca. 2.56 Ga and multiple migmatization and metamorphism from 2.52 to 1.85 Ga. A meta-dolerite sample yields a magmatic emplacement age of ca. 1.83 Ga. In situ zircon Hf isotopic data indicate that most zircons from the gneiss samples have ε_Hf(t) values from –16.9 to + 3.1 and crustal model ages from 2.84 to 3.73 Ga, whereas magmatic zircons from the meta-dolerite dike record ε_Hf(t) values from –5.2 to + 5.2 and model ages of 2.05–2.44 Ga. The first-recognized Neoarchaean tonalitic-trondjemitic migmatite complex in the Rangnim Massif, together with previously identified tonalitic-trondhjemitic-granodioritic (TTG) rocks in the Rimjingang Belt and the coeval counterparts in western Gyeonggi massif, represents the oldest crustal nuclei in the Korean Peninsula. The multiple tectonothermal events in this study present reliable evidence not only for attesting to consanguinity of the basement between the Korean Peninsula and the North China Craton but also for defining the influence scope of the late Palaeoproterozoic orogeny in the Korean Peninsula.  相似文献   

赞皇地区～2.5Ga A型花岗岩的成因及构造背景:以黄岔岩体为例   总被引：1，自引：1，他引：0  

李伦  杨永强  杨崇辉  杜利林  宋会侠  任留东  谢进  刘大鹏 《岩石学报》2017,33(9):2850-2866

位于华北克拉通中部的赞皇杂岩中保留有丰富的新太古代-古元古代岩石记录,是探究华北克拉通早期演化的重要地区之一。其中新太古代晚期TTG片麻岩和花岗岩的成因研究是探讨赞皇杂岩构造演化过程的关键。本文选择出露于河北省邢台市西部山区的黄岔花岗岩体进行研究。该岩体呈不规则的岩株产出,与周围地层主要呈构造接触关系,局部侵入于官都群石英岩中。岩体主要由片麻状、似斑状二长花岗岩组成,边缘相偶见细粒片麻岩包体,斑晶为长石和少量石英。LA-ICP-MS岩浆锆石的~(207)Pb/~(206)Pb加权平均年龄为2488±6Ma,代表岩体的形成时代。由于黄岔岩体侵入于官都群,根据该花岗岩的时代可以限定官都群地层时代为太古代,而非古元古代。但官都群与赞皇群的关系还需要进一步研究。黄岔岩体具有高硅(Si O2=72.64%~74.16%)、富钾(K_2O=3.53%~6.15%)、富碱(ALK=7.59%~9.07%)及铁(Fe_2O_3T=1.84%~3.03%),贫钙(CaO=0.67%~1.67%)、低钛(TiO_2=0.18%~0.28%)、低镁(MgO=0.31%~0.46%)的特征。岩石的稀土总量较高(ΣREE=364.2×10~(-6)~661.1×10~(-6)),轻重稀土元素分异较强烈((La/Yb)_N=18.7~29.8),并具有明显的负Eu异常(Eu/Eu*=0.23~0.33)。微量元素中,富Zr、Zn、Nb、Ga、Y,而贫Sr、V、Cr、Co、Ni等元素,Rb/Sr比值较高,介于0.73~2.72之间,平均1.96。岩石Ga/Al值(2.75×10-4~3.11×10-4)高,全岩Zr饱和温度为826~877℃,具有A型花岗岩特征。黄岔岩体锆石εHf(t)为0.96~6.2,单阶段和两阶段Hf模式年龄分别为2552~2746Ma和2576~2826Ma。黄岔岩体具有造山后A型花岗岩的特征,为2.7~2.5Ga的新太古代TTG片麻岩在造山后地壳拉张减薄初期的构造背景下部分熔融所形成。~2.5Ga的碱性花岗岩在华北不同地区分布,并形成于伸展的构造背景。该期碱性花岗岩的出现,标志华北克拉通在太古宙末期已经初步形成稳定的克拉通。  相似文献