内蒙古白音宝力道花岗斑岩锆石U-Pb定年--白音宝力道金矿成矿主岩的形成时代   总被引：7，自引：4，他引：7  

张炯飞  庞庆邦朱群金成洙  刘国军 《地质通报》2004,23(2):189-192

内蒙古白音宝力道花岗斑岩位于内蒙古苏尼特左旗南部苏尼特左旗-贺根山缝合带北侧,为白音宝力道金矿的成矿主岩。其单颗粒锆石U-Pb年龄为(439.8±4.3)Ma(MSWD=0.001),表明白音宝力道金矿花岗斑岩及金矿形成于早古生代中期。  相似文献   

湖北蕲春花岗岩类锆石SHRIMP年龄：大别山造山带内弱变质—未变质晋宁期花岗岩类的发现   总被引：2，自引：0，他引：2       下载免费PDF全文

薛怀民  刘敦一  董树文  简平  刘晓春 《地质学报》2004,78(1):81-88

蕲春花岗质杂岩体包括斑状二长花岗岩和花岗岩两部分,它们之间在化学性质上存在着很大的差异,前者表现为高Al 2O3(15.73%)、相对高CaO(2.46%)、Na2O含量明显高于K2O(Na2O/K2O=1.27),尤以强烈亏损重稀土元素和极强的轻、重稀土元素分馏程度[(La/Yb)N=46.8]为特征而类似于太古宙高Al2O3的TTG岩石.而后者则以较低的Al2O3含量(14.05%)、贫CaO(0.82%)、K2O含量明显高于Na2O(Na2O/K2O=0.81)为特征,轻、重稀土元素的分馏程度[(La/Yb)N=10.89]也较片麻状二长花岗岩中弱得多.两类岩石中锆石的U-PbSHRIMP年龄分别为824.6±17.6 Ma和784±20 Ma,该时代与大别山造山带内花岗片麻岩的原岩形成年龄类似.大别山造山带内弱变质-未变质晋宁期花岗岩的出现表明扬子板块印支期向北俯冲时,该花岗质杂岩处于俯冲板片的后缘,可代表造山带内扬子基底的原地露头.而岩体周围的高压变质杂岩应是折返上来的无根构造岩片,大别山造山带内高压超高压变质杂岩的出露不是整体性抬升剥蚀的结果.  相似文献   

江西大吉山五里亭花岗岩单颗粒锆石U-Pb同位素年龄及其地质意义探讨   总被引：29，自引：6，他引：29       下载免费PDF全文

张文兰  华仁民  王汝成  李惠民  陈培荣 《地质学报》2004,78(3):352-358

江西大吉山五里亭花岗岩一直被认为是与大吉山钨矿有关的早阶段花岗岩体 ,时代为燕山早期。但实际上大吉山地区各阶段花岗岩体之间的时空关系并不清楚 ,前人的某些年龄数据也存在相互矛盾之处。本文利用单颗粒锆石 U - Pb化学法 ,对五里亭花岗岩进行了年代学研究 ,获得 2 38.4± 1Ma的岩体侵位年龄 ,这个年龄属印支期。本文还结合某些岩石学、地球化学特征研究及与相邻岩体的对比 ,认为五里亭花岗岩确应归属于印支期 ,因此 ,五里亭岩体与大吉山钨矿没有成因上的直接联系。五里亭花岗岩侵位年龄的厘定和该地区更多印支期花岗岩的不断发现 ,表明印支运动在华南的影响超出了人们以往的认识。在此基础上 ,本文还对华南印支运动和印支期花岗岩的问题进行了简单的讨论  相似文献   

Timing and geochemical characters of the Sanchazi magmatic arc in Mianlüe tectonic zone, South Qinling     

LI Shuguang  HOU Zhenhui  YANG Yongcheng  Sun Weidong  ZHANG Guowei  LI Qiuli 《中国科学D辑(英文版)》2004,47(4)

The Sanchazi mafic-ultramafic complex in Mianlue tectonic zone, South Qinling can be subdivided into two blocks, i.e. Sanchazi paleo-magmatic arc and Zhuangkegou paleo-oceanic crust fragment (ophiolite). The Sanchazi paleo-magmatic arc is mainly composed of andesite, basaltic and basalt-andesitic gabbro (or diorite), andesitic dyke, plagiogranite and minor ultramafic rocks, which have typical geochemical features of island arc volcanic rocks, such as high field strength element (e.g. Nb, Ti) depletions and lower Cr, Ni contents. The Light rare earth element (LREE) and K enrichments of these rocks and zircon xenocrystals of 900 Ma from plagiogranite suggest that this magmatic arc was developed on the South active continental margin of the South Qinling micro-continent. The U-Pb age of (300 ± 61)Ma for zircons from plagiogranite indicates that the Mianlue paleo-oceanic crust was probably subducted underneath the South Qinling micro-continent in Carboniferous. This is consistent with the formation time (309Ma) of the Huwan eclogite originating from oceanic subduction in Dabie Mountains, suggesting that the Mianlue paleo-ocean probably extended eastward to the Dabie Mountains in Carboniferous. The high-Mg adakitic rocks in Sanchazi paleo-magmatic arc suggest that the subducted oceanic crust was relatively young (＜25Ma) and hot.  相似文献   

Metamorphism and metamorphic K–Ar ages of the Mesozoic accretionary complex in Northland, New Zealand     

Yujiro  Nishimura  Philippa M.  Black  Tetsumaru  Itaya 《Island Arc》2004,13(3):416-431

Abstract A southwest dipping Mesozoic accretionary complex, which consists of tectonically imbricated turbiditic mudstone and sandstone, hemipelagic siliceous mudstone, and bedded cherts and basaltic rocks of pelagic origin, is exposed in northern North Island, New Zealand. Interpillow limestone is sometimes contained in the basaltic rocks. The grade of subduction‐related metamorphism increases from northeast to southwest, indicating an inverted metamorphic gradient dip. Three metamorphic facies are recognized largely on the basis of mineral parageneses in sedimentary and basaltic rocks: zeolite, prehnite‐pumpellyite and pumpellyite‐actinolite. From the apparent interplanar spacing d₀₀₂ data for carbonaceous material, which range from 3.642 to 3.564 Å, the highest grade of metamorphism is considered to have attained only the lowermost grade of the pumpellyite‐actinolite facies for which the highest temperature may be approximately 300°C. Metamorphic white mica K–Ar ages are reported for magnetic separates and <2 µm hydraulic elutriation separates from 27 pelitic and semipelitic samples. The age data obtained from elutriation separates are approximately 8 m.y. younger, on average, than those from magnetic separates. The age difference is attributed to the possible admixture of nonequilibrated detrital white mica in the magnetic separates, and the age of the elutriation separates is considered to be the age of metamorphism. If the concept, based on fossil evidence, of the subdivision of the Northland accretionary complex into north and south units is accepted, then the peak age of metamorphism in the north unit is likely to be 180–130 Ma; that is, earliest Middle Jurassic to early Early Cretaceous, whereas that in the south unit is 150–130 Ma; that is, late Late Jurassic to early Early Cretaceous. The age cluster for the north unit correlates with that of the Chrystalls Beach–Taieri Mouth section (uncertain terrane), while the age cluster for the south unit is older than that of the Younger Torlesse Subterrane in the Wellington area, and may be comparable with that of the Nelson and Marlborough areas (Caples and Waipapa terranes).  相似文献   

Age of Yingfeng rapakivi granite pluton on the north flank of Qaidam and its geological significance   总被引：2，自引：0，他引：2  

XIAO Qinghui  LU Xinxiang  WANG Fei  SUN Yangui  Wei Xiangdong  XlNG Zuoyun 《中国科学D辑(英文版)》2004,47(4)

Rapakivi granite is a very rare and special type of rocks in the crust. Nearly all the typical Proterozoic rapakivi occurred in stable craton, and was regarded as representing special anorogenic settings and rifting events of the supercontinents. Therefore, rapakivi has constantly been attracting the attention of researchers from various countries[15]. For example, the Protero- zoic rapakivi granites occurring in Miyun, Beijing, has been studied in detail by the researchers both at home and …  相似文献   

中国新疆博斯腾湖全新世沉积环境年代学特征   总被引：18，自引：1，他引：18  

张成君  曹洁  类延斌  尚华明 《沉积学报》2004,22(3):494-499

通过对博斯腾湖沉积物湖芯样品进行137Cs,14C-AMS测年分析,湖芯剖面上有明显的1986年的切尔诺贝利核事故蓄积峰,以及1975年和1963年次蓄积峰,这些137Cs蓄积峰对博斯腾湖现代沉积有明显的时标意义。通过质量深度与年代分析,博斯腾湖的沉积速率相对稳定,平均沉积速率为0.13±0.01g/cm2.a。与14C年代获得的中全新世以来的平均沉积速率0.13±0.03cm/a和0.12±0.05cm/a相似,表明博斯腾湖中全新世以来的沉积环境较稳定,并且也说明14C-AMS测年分析所得的结果较为可靠,可以利用博斯腾湖沉积物样品测定的14C年代进行线性回归作年代校正,由于湖泊沉积物中老碳效应的影响,博斯腾湖沉积物有机质14C测年偏老约650a左右。  相似文献   

北祁连玉石沟蛇绿岩形成于晚震旦世的SHRIMP年龄证据   总被引：45，自引：5，他引：45  

史仁灯  杨经绥  吴才来  J.WOODEN 《地质学报》2004,78(5):649-657

玉石沟蛇绿岩位于青藏高原东北缘的北祁连山中部 ,由地幔橄榄岩、堆晶辉长岩、辉绿岩、枕状熔岩以及夹杂在其中的硅质岩组成。地幔橄榄岩主要是方辉橄榄岩 ,其主要氧化物成分较为单一 ,具 L REE富集、Eu亏损的 U形 REE配分模式 ,亏损强不相容元素 ;枕状熔岩具典型 MORB特征 ,在构造判别图解上位于 MORB和 IAT区域 ,指示蛇绿岩可能形成于类似于洋中脊的构造环境 ,并受到火山弧岩浆作用的影响。堆晶辉长岩具明显的 Eu正异常 ,其锆石离子探针 (SHRIMP) 2 0 6 Pb/2 38U加权平均年龄为 5 5 0± 17Ma,Th/U值为 0 .5 3～ 1.85 ,大于0 .2 3,为岩浆成因锆石 ,其年龄代表辉长岩的成岩时代 ,推断玉石沟蛇绿岩形成于晚震旦世。  相似文献   

柴达木盆地北缘古生代超高压带中花岗质岩浆作用   总被引：38，自引：0，他引：38  

吴才来  杨经绥  许志琴  Joseph L.WOODEN  Trevor IRELAND  李海兵  史仁灯  孟繁聪  陈松永  Harold PERSING  Anders MEIBOM 《地质学报》2004,78(5):658-674

祁连南缘古生代超高压变质带 (榴辉岩年龄为 4 6 6～ 4 95 Ma)上一套中高级变质岩系 (达肯大坂片麻岩 )中存在三类花岗岩组合 : 类 :石英二长闪长岩 -花岗闪长岩 -二长花岗岩 , 类 :二长花岗岩 -二云母花岗岩-含白云母花岗岩 -正长花岗岩 , 类 :花岗闪长岩 -二长花岗岩 -黑云母花岗岩。 类岩石组合中的二长花岗岩锆石SHRIMP年龄为 4 73Ma, 类岩石组合中的正长花岗岩锆石 SHRIMP年龄为 4 4 6 Ma, 类岩石组合中的二长花岗岩锆石 SHRIMP年龄为 397Ma。从三类花岗岩组合的组成矿物来看 , 类和 类的矿物组合主要为斜长石、角闪石、石英、碱性长石、黑云母 , 类的矿物组合为钾长石、石英、白云母、黑云母、斜长石 ;从岩石地球化学特征上看 , 类和 类花岗岩为 型花岗岩 ,岩石的 Si O2 =6 1%～ 6 9% ,Na2 O/ K2 O>1,ANK<1,δEu=0 .7～ 1.0 ; 类花岗岩为 S型花岗岩 ,岩石的 Si O2 =70 %～ 76 % ,Na2 O/ K2 O<1,ANK>1,δEu=0 .1～ 0 .3;从构造环境上看 , 类花岗岩形成于岛弧环境或活动大陆边缘 , 类花岗岩形成于同碰撞 , 类花岗岩形成于碰撞后。结合区域地质特征 ,我们认为 ,早奥陶世 ,南祁连洋板块向北俯冲于祁连陆块之下 ,规模不大的南祁连洋很快闭合 ,但俯冲下去的大洋板块仍拖动柴达木陆块继续俯冲 ,俯冲  相似文献   

柴达木盆地北缘"沙柳河岩群"的重新启用   总被引：12，自引：0，他引：12  

辛后田  周世军  王惠初  郝国杰  陈能松  韩英善 《西北地质》2004,37(1):26-33

柴北缘变质基底岩系中的表壳岩包含了岩石组合、沉积建造、变质程度和地质时代不同的两套岩石组合。其中，分布在柴达木地块的沙柳河、鱼卡河等地的以大理岩、石英岩和含石榴石英片岩为主含榴辉岩透镜体的表壳岩系，时代限定在1．0～1．3Ga，与分布在欧龙布鲁克微陆块的全吉山、德令哈等地形成时代大约2.3～2.4Ga的达肯大坂岩群有着明显的不同，后者以斜长角闪岩、石榴石英片岩和黑云变粒岩为主，并具有较强的钾质混合岩化。由于前者岩石组合清楚，沉积建造特征明显，构造意义独特，且有一定的区域分布性和可比性，所以具备建立新的岩群的条件。根据定名优先的原则，决定重新启用沙柳河岩群。  相似文献