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1.
《地质论评》2012,58(3)
本文报道了华北克拉通南缘豫西鲁山下汤地区古元古代片麻状花岗岩和黑云角闪斜长片麻岩的全岩地球化学和锆石SHRIMP U-Pb年龄和Hf同位素组成.岩石呈包体形式存在于中元古代花岗岩中.片麻状花岗岩具深熔特征,岩浆锆石年龄为2.30 Ga;岩石高SiO2和K2O,低∑FeO、MgO和CaO,具稀土总量较高(∑REE=165.8×10-6)、轻重稀土分离较强[(La/Yb)n=37.8]及弱负铕异常(Eu/Eu(*)=0.76)的稀土模式;εNd(t)(t=2.30 Ga)=-0.75; tDM(Nd) =2.66 Ga.黑云角闪斜长片麻岩变质原岩为辉长闪长岩,捕获锆石年龄为2.25 Ga;岩石低SiO2 和MgO,高Al2O3和P2O5,具稀土总量高(∑REE=373.4×10-6)、轻重稀土分离不强[ (La/Yb)n=9.4]及较强负铕异常( Eu/Eu*=0.44)的稀土模式;εNd(t)(t=2.25 Ga)=-1.21;tDM(Nd) =2.75 Ga.片麻状花岗岩和黑云角闪斜长片麻岩都记录了1.94 Ga变质锆石年龄.片麻状花岗岩的岩浆锆石组成域的εHf(t)(t=2.30 Ga)=-6.71~0.38,tDMI(Hf) =2627 ~2910 Ma,tDM2(CC)(Hf)=2823 ~ 3255 Ma.黑云角闪斜长片麻岩的捕获锆石组成域的εHf(t)(t=2.25 Ga)=-19.58~ -1.73,tDM1 (Hf) =2664~3360 Ma,tDM2(CC)(Hf)=2968 ~4011 Ma.结合前人资料,得出如下结论:华北克拉通南缘豫陕晋结合部地区存在—规模较大的约2.3 Ga地质体分布区;华北克拉通南缘很可能存在规模巨大的>2.7 Ga基底;中部造山带与孔兹岩带具有类似的古元古代晚期构造热事件演化历史.  相似文献   

2.
本文报道了华北克拉通南缘豫西鲁山下汤地区古元古代片麻状花岗岩和黑云角闪斜长片麻岩的全岩地球化学和锆石SHRIMP U-Pb年龄和Hf同位素组成。岩石呈包体形式存在于中元古代花岗岩中。片麻状花岗岩具深熔特征,岩浆锆石年龄为2.30Ga;岩石高SiO2和K2O,低ΣFeO、MgO和CaO,具稀土总量较高(ΣREE=165.8×10-6)、轻重稀土分离较强[(La/Yb)n=37.8]及弱负铕异常(Eu/Eu*=0.76)的稀土模式;εNd(t)(t=2.30Ga)=-0.75;tDM(Nd)=2.66Ga。黑云角闪斜长片麻岩变质原岩为辉长闪长岩,捕获锆石年龄为2.25Ga;岩石低SiO2和MgO,高Al2O3和P2O5,具稀土总量高(ΣREE=373.4×10-6)、轻重稀土分离不强[(La/Yb)n=9.4]及较强负铕异常(Eu/Eu*=0.44)的稀土模式;εNd(t)(t=2.25Ga)=-1.21;tDM(Nd)=2.75Ga。片麻状花岗岩和黑云角闪斜长片麻岩都记录了1.94Ga变质锆石年龄。片麻状花岗岩的岩浆锆石组成域的εHf(t)(t=2.30Ga)=-6.71~0.38,tDM1(Hf)=2627~2910Ma,tDM2(CC)(Hf)=2823~3255Ma。黑云角闪斜长片麻岩的捕获锆石组成域的εHf(t)(t=2.25Ga)=-19.58~-1.73,tDM1(Hf)=2664~3360Ma,tDM2(CC)(Hf)=2968~4011Ma。结合前人资料,得出如下结论:华北克拉通南缘豫陕晋结合部地区存在一规模较大的约2.3Ga地质体分布区;华北克拉通南缘很可能存在规模巨大的>2.7Ga基底;中部造山带与孔兹岩带具有类似的古元古代晚期构造热事件演化历史。  相似文献   

3.
鲁西沂山地区高级深熔混合岩中存在丰富的不同时代、不同类型的岩石包体。在详细野外地质工作基础上,本文对高级深熔混合岩中的包体进行了锆石SHRIMP U-Pb定年和Hf同位素分析及全岩地球化学研究,以期探讨沂山地区高级深熔混合岩的源区性质。英云闪长质片麻岩形成时代为~2.7Ga,存在2.69Ga和2.53~2.51Ga两期基性岩浆作用,并记录了2.52~2.50Ga变质作用。角闪斜长片麻岩与黑云角闪变粒岩互层产出,它们可能为变质火山岩,其岩浆锆石年龄为2.51Ga。变质基性岩的岩浆锆石ε_(Hf)(t)为0~+8.1,一阶段Hf模式年龄为2.83~2.54Ga;变质火山岩的岩浆锆石ε_(Hf)(t)为-1.2~+5.8,一阶段Hf模式年龄为2.89~2.71Ga。结合前人研究,这套高级深熔混合岩的源区组成包括了新太古代早期的英云闪长质片麻岩和变质辉长岩,新太古代晚期的石英闪长质片麻岩、变质火山岩及斜长角闪岩等岩石类型。~2.5Ga基性岩浆作用在鲁西地区发育广泛,为新太古代晚期深熔作用及高级深熔混合岩和壳源花岗岩的形成提供了热源。  相似文献   

4.
华北克拉通五台群LA-ICP-MS锆石U-Pb年龄和Hf同位素特征   总被引:2,自引:0,他引:2  
通过对五台群石咀亚群金刚库组4个典型样品的LA-ICP-MS锆石U-Pb年龄和Hf同位素研究,对五台群的形成时代及华北克拉通新太古代—古元古代期间的地壳演化进行了探讨。锆石U-Pb同位素测定结果表明,侵入金刚库组中的片麻状花岗岩锆石的U-Pb年龄为2548Ma,因此五台群的上限年龄约为2.5Ga;金刚库组黑云母石英片岩和片麻状石英闪长岩的原岩锆石U-Pb年龄分别为2663Ma和2636Ma,因此五台群的下限年龄约为2.7Ga。五台群的地质年龄为2.5~2.7Ga,属于新太古代。锆石Hf同位素研究结果表明,黑云母石英片岩和片麻状石英闪长岩的二阶段Hf模式年龄(tDM2)均为2.8Ga左右,指示2.8Ga左右是五台山区乃至整个华北克拉通地壳生长的重要时期;片麻状花岗岩tDM2平均为2.57Ga,与锆石结晶年龄非常接近,表明2.5Ga左右也是华北克拉通地壳的主要增生期。地壳的增长是幕式的,2.8Ga和2.5Ga都是华北克拉通地壳生长时期。  相似文献   

5.
本文报道了华北克拉通西部武川西乌兰不浪地区太古宙变质基底的锆石SHRIMP年龄和Hf同位素组成。一个片麻状奥长花岗岩样品的锆石具核边结构,核部岩浆锆石和边部变质锆石的207Pb/206Pb加权平均年龄分别为2692±17Ma和2528±16Ma。对9个样品进行了锆石Hf同位素分析。新太古代早期(2692~2697Ma)片麻状奥长花岗岩(2个样品)的岩浆锆石的εHf(t)、tDM1(Hf)和tDM2(Hf)分别为4.78~8.83、2646~2780Ma和2632~2845Ma;新太古代二辉麻粒岩(2个样品)中的捕获锆石的εHf(t)、tDM1(Hf)和tDM2(Hf)分别为-2.30~8.62、2543~2954Ma和2529~3189Ma;新太古代变质深成岩(4个样品)的岩浆锆石的εHf(t)、tDM1(Hf)和tDM2(Hf)分别为-2.60~8.09、2529~2880Ma和2538~3089Ma;古元古代蓝晶石榴长英质片麻岩(1个样品)的碎屑锆石的εHf(t)、tDM1(Hf)和tDM2(Hf)分别为1.52~6.59、2432~2774Ma和2498~2925Ma。结合前人研究结果,可得出如下结论和认识:1)该区存在新太古代早期片麻状奥长花岗岩,太古宙岩石在新太古代晚期普遍遭受高级变质作用影响;2)新太古代早期为该区地壳形成主要时期,新太古代晚期则主要表现为陆壳物质再循环;3)作为阴山地块的典型代表,固阳-武川地区与华北克拉通东部太古宙基底十分类似,可能表明华北克拉通在新太古代晚期已成为统一的整体。  相似文献   

6.
刘福来  刘平华 《岩石学报》2009,25(9):2113-2131
北苏鲁仰口地区出露超高压的变辉长岩.锆石阴极发光图像和其内部矿物包体激光拉曼测试的联合研究结果表明,变辉长岩锆石具有弱发光效应的岩浆韵律环带的核和被改造的强发光效应的边.岩浆韵律环带的核部保存大量而复杂的矿物包体,包括普通辉石(Cpx)+斜方辉石(Opx)+斜长石(P1)+石英(Qtz)+黑云母(Bt)+钛铁矿(Ilm)+磷灰石(Ap);边部保存的矿物包体则相对较少,包括普通辉石(Cpx)+斜方辉石(Opx)+斜长石(Pl)+磷灰石(Ap).尽管岩浆韵律环带核部的稀土元素总合量比被改造的锆石边部明显偏高,但二者稀土元素配分模式具有明显的相似性,主要表现为轻稀土相对亏损,而重稀土明显富集,相应的(La/Yb)N=0.00015~0.00039,并具有明显的负Eu异常(Eu/Eu*=0.20~0.26)、相对明显的正Ce异常(Ce/Ce*=71.5~147.4)和较高的Th/U比值(1.97~2.69).上述特征表明,仰口地区变辉长岩中的锆石均为继承性的岩浆锆石,而没有新生的变质锆石.LA-(MC)-ICP-MS锆石原位U-Pb定年和Lu-Hf同位素分析结果表明,两件锆石样品Y1和Y2的年龄数据所构成的不一致线显示了十分接近的上交点和下交点年龄.其上交点年龄分别为785±15Ma(2σ)和784±12Ma(2σ),应代表原岩的形成时代,表明变辉长岩的原岩与Rodinia超大陆裂解的岩浆事件存在密切的成因关系;而下交点年龄分别为226±24Ma(2σ)和228±26Ma(2σ),与苏鲁其它类型超高压岩石中含柯石英锆石微区记录的变质年龄十分吻合,应代表变辉长岩的超高压变质时代.岩浆结晶锆石的核部具有明显偏高的176Lu/177Hf(0.00044~0.00291)和176Yh/177Hf(0.0165~0.1168)比值,而176Hf/177Hf比值变化于0.281956~0.282048之间,相应的εHf(t)=-8.5~-14.0,tDM2=2.03~2.32Ga,表明仰口地区变辉长岩的原岩起源于古元古代时期的富集地幔或发生部分熔融的下地壳残留体.被改造的岩浆结晶锆石的边部则具有明显偏低的176Lu/177Hf(0.00029~0.00060)和176Yh/177Hf(0.0112~0.0200)比值,而176Hf/177Hf(t)比值变化于0.281953~0.282002之间,相应的εHf(t)=-10.2~-11.9,tDM2=2.12~2.21Ga.与岩浆结晶锆石核部相比,被改造的岩浆锆石边部的176Lu/177Hf、176Yb/177Hf、176Hf/177Hf(t)比值和εHf(t)和tDM2值的变化范围更小,表明中-新三叠纪的超高压变质作用使岩浆结晶锆石边部的Lu-Hf同位素体系发生调整,更趋向于均一化.  相似文献   

7.
张士英岩体位于华北地台南缘,岩石类型包括钾长花岗岩、似斑状花岗岩和石英斑岩脉,其中只在钾长花岗岩中发育有暗色岩石包体,在包体和寄主岩中发育反映岩浆混合作用的岩石结构。钾长花岗岩、似斑状花岗岩和石英斑岩脉的SHRIMP锆石U-Pb年龄分别为107.3±2.4Ma、106.7±2.5Ma和101±3Ma。锆石Hf同位素分析结果显示,钾长花岗岩的锆石εHf(t)为-15.96~-20.80,单阶段模式年龄(tDM1)为1396~1643Ma,两阶段模式年龄(tDM2)为1880~2018Ma;似斑状花岗岩的锆石εHf(t)为-18.97~-22.18,tDM1为1512~1640Ma,tDM2为1925~2080Ma;除了一粒年龄为2.6Ga的锆石具有εHf(t)为-0.71、tDM1为2943Ma和tDM2为3036Ma的组成,石英斑岩的锆石εHf(t)为-23.41~-27.95,tDM1为1678~1896Ma,tDM2为2144~2330Ma。这些数据暗示,除了存在少量太古宙地壳物质的贡献外,张士英岩体的物质来源可能主要为1.9~2.3Ga期间形成的新生地壳,但也不排除古老地壳与富集地幔源混合的可能。综合分析前人研究成果表明,在太平洋板块俯冲方向发生转变的过程中,先存断裂带发生拉张。张士英岩体与中国东部同期岩浆活动一起可能形成于这种受断裂带控制的伸展环境。  相似文献   

8.
卡而却卡铜多金属矿区花岗闪长岩体中广泛分布具有似斑状结构的闪长质包体,包体主要为椭圆形,定向排列,具有与寄主岩石相似的矿物组合,但角闪石含量明显比寄主岩石高,具有明显的不平衡反应结构,发育针状磷灰石。LA-MC-ICP-MS锆石U-Pb测试表明,暗色微粒包体形成于(234.1±0.6)Ma,寄主花岗闪长岩形成于(234.4±0.6)Ma,为岩浆混合作用的存在提供了有力证据。地球化学特征显示,暗色包体Si O2、Mg O含量较寄主岩石高,更偏基性;均富集大离子亲石元素和轻稀土元素,亏损高场强元素,但寄主花岗闪长岩LaN/YbN值(11.6~19.0)明显高于暗色包体(5.0~9.7),Nb/Ta值(10.6~11.7)低于暗色包体(11.6~14.8)。二者具有相近的Sr-Nd-Hf同位素组成,花岗闪长岩的εNd(t)值为-5.3~-4.2,(87Sr/86Sr)i值为0.71110~0.71125,εHf(t)为-5.8~-3.4,tDM(Hf)为1012~1102 Ma;暗色包体的εNd(t)值为-5.2~-5.0,(87Sr/86Sr)i值为0.71114~0.71171,εHf(t)为-6.3~-1.6,tDM(Hf)为937~1129 Ma。综上推测,在中三叠世俯冲—碰撞转换阶段,EMⅡ型富集岩石圈地幔在上涌软流圈物质的作用下发生部分熔融产生基性岩浆,并底侵下地壳物质局部熔融形成长英质岩浆房,进而由基性岩浆注入长英质岩浆房后,经过演化形成微粒包体,演化了的基性岩浆与长英质岩浆混合,最终形成含微粒包体的均一岩浆,这种岩浆结晶后形成含暗色包体花岗闪长岩。  相似文献   

9.
赵娇  张成立  郭晓俊  刘欣雨  王权 《岩石学报》2015,31(6):1606-1620
华北克拉通新太古代末与古元古代早期的构造转化对认识华北克拉通早期地壳演化具重要意义。该克拉通中部带吕梁地区盖家庄正长花岗岩获得2398~2408Ma的形成年龄,其成因研究将为探讨华北克拉通新太古代晚期与古元古代早期构造演化提供重要信息。该岩体富K,高硅、碱、Fe OT/Mg O,低Ca、Mg,富集Rb、Th、U等LILE、较高的HFSE,明显亏损Sr、Ba、P、Ti,具弱轻重稀土分异和强负Eu异常的"燕式"稀土分配模式,并具高的Ga/Al比值和高锆石饱和温度,显示了碰撞造山后A2型花岗岩的特征。岩体全岩εNd(t)=2.0~2.3,两阶段Nd模式年龄tDM2=2606~2629Ma,锆石εHf(t)=+2.2~+7.1,tDM2(2494~2791Ma)略高或接近其形成年龄,一致证明主要源自新太古代中晚期新生下部陆壳物质的部分熔融,并有少量幔源物质的添加。结合区域地质及同期钾质花岗岩类的广泛出现,盖家庄正长花岗岩与同期钾质花岗岩一同代表了华北克拉通~2.5Ga形成后,中部构造带于古元古代早期~2.4Ga发生的一次陆壳伸展拉张作用引发的地幔物质上涌基性岩浆上侵导致下部新生陆壳物质增温发生部分熔融构造岩浆事件,证明陆壳已转入伸展拉张构造环境。  相似文献   

10.
本文报道了内蒙古大青山地区早前寒武纪变质岩石的锆石Hf同位素和稀土组成。两个古元古代晚期(1.9~2.1 Ga)变质碎屑沉积岩样品中碎屑锆石的(n(176Hf)/n(177Hf))c、tDM1(Hf)和tDM2(Hf)分别为0.281079~0.281502、2548~3000 Ma、2612~3153 Ma和0.280916~0.281451、2533~2717 Ma、2600~3404 Ma; 一个古元古代早期(2.37 Ga)变质辉长岩样品中岩浆锆石的εHf(t)和tDM1(Hf)分别为1.50~6.68和2449~2647 Ma,表明大青山及邻区在新太古代晚期—古元古代早期存在强烈的构造岩浆热事件,既有地幔添加又有壳内再循环作用。三个样品的边部变质锆石εHf(t)、tDM1(Hf)和tDM2(Hf)分别为-9.49~3.91、2201~2686 Ma、2285~2887 Ma;-7.29~-2.42、2350~2540 Ma、2499~2740 Ma和-5.46~-0.53、2319~2507 Ma、2443~2687 Ma,Th/U比值普遍小于01。与核部锆石相比,边部变质锆石tDM2(Hf)变小,Th/U比值和稀土含量降低,但稀土模式十分类似。研究表明,变质锆石增生边的形成及其Hf同位素、稀土和U—Th组成受核部锆石和变质作用的双重制约。变质增生边的形成至少部分与核部锆石溶解以后的再结晶有关,变质流体起了重要作用。  相似文献   

11.
Pant-y-ffynnon Quarry in South Wales yielded a rich cache of fossils in the early 1950s, including articulated specimens of new species (the small sauropodomorph dinosaur Pantydraco caducus and the crocodylomorph Terrestrisuchus gracilis), but no substantial study of the wider fauna of the Pant-y-ffynnon fissure systems has been published. Here, our overview of existing specimens, a few described but mostly undescribed, as well as freshly processed material, provides a comprehensive picture of the Pant-y-ffynnon palaeo-island of the Late Triassic. This was an island with a relatively impoverished fauna dominated by small clevosaurs (rhynchocephalians), including a new species, Clevosaurus cambrica, described here from a partially articulated specimen and isolated bones. The new species has a dental morphology that is intermediate between the Late Triassic Clevosaurus hudsoni, from Cromhall Quarry to the east, and the younger C. convallis from Pant Quarry to the west, suggesting adaptive radiation of clevosaurs in the palaeo-archipelago. The larger reptiles on the palaeo-island do not exceed 1.5?m in length, including a small carnivorous crocodylomorph, Terrestrisuchus, and a possible example of insular dwarfism in the basal dinosaur Pantydraco.  相似文献   

12.
Lithostratigraphy, physicochemical stratigraphy, biostratigraphy, and geochronology of the 77–70 Ma old series bracketing the Campanian–Maastrichtian boundary have been investigated by 70 experts. For the first time, direct relationships between macro- and microfossils have been established, as well as direct and indirect relationships between chemo-physical and biostratigraphical tools. A combination of criteria for selecting the boundary level, duration estimates, uncertainties on durations and on the location of biohorizons have been considered; new chronostratigraphic units are proposed. The geological site at Tercis is accepted by the Commission on Stratigraphy as the international reference for the stratigraphy of the studied interval. To cite this article: G.S. Odin, C. R. Geoscience 334 (2002) 409–414.  相似文献   

13.
Robert L. Linnen   《Lithos》2005,80(1-4):267-280
The solubilities of columbite, tantalite, wolframite, rutile, zircon and hafnon were determined as a function of the water contents in peralkaline and subaluminous granite melts. All experiments were conducted at 1035 °C and 2 kbar and the water contents of the melts ranged from nominally dry to approximately 6 wt.% H2O. Accessory phase solubilities are not affected by the water content of the peralkaline melt. By contrast, solubilities are affected by the water content of the subaluminous melt, where the solubilities of all the accessory phases examined increase with the water content of the melt, up to 2 wt.% H2O. At higher water contents, solubilities are nearly constant. It can be concluded that water is not an important control of accessory phase solubility, although the water content will affect diffusivities of components in the melt, thus whether or not accessory phases will be present as restite material. The solubility behaviour in the subaluminous and peralkaline melts supports previous spectroscopic studies, which have observed differences in the coordination of high field strength elements in dry vs. wet subaluminous granitic glasses, but not for peralkaline granitic glasses. Lastly, the fact that wolframite solubility increases with increasing water content in the subaluminous melt suggests that tungsten dissolved as a hexavalent species.  相似文献   

14.
Some olistolites reworked in a Tertiary flysch of Mount Parnon (Peloponnesus, Greece) exhibit a Late Permian assemblage, dominated by Paradunbarula (Shindella) shindensis, Hemigordiopsis cf. luquensis and Colaniella aff. minima. This association corresponds to the Late Wuchiapingian (=Late Dzhulfian), a substage whose algae and foraminifera are generally little known. Contemporaneous limestones crop out in the middle part of the Episkopi Formation in Hydra, but they are rather commonly reworked in Mesozoic and Cainozoic sequences. The palaeobiogeographical affinities shared by the foraminiferal markers of Greece, southeastern Pamir, and southern China, are very strong (up to the specific level), and are congruent with the Pangea B reconstructions. To cite this article: E. Skourtsos et al., C. R. Geoscience 334 (2002) 925–931.  相似文献   

15.
PALEONTOLOGY     
正20141596 Liu Yunhuan(School of Earth Sciences and Resources,Chang’an University,Xi’an 710054,China);Shao Tiequan Early Cambrian Quadrapyrgites Fossils of Xixiang Boita in Southern Shaanxi Province(Journal of Earth Sciences and Environment,ISSN1672-6561,CN61-1423/P,35(3),2013,p.39-43,3 illus.,20 refs.)  相似文献   

16.
正20141719 Chen Zhijun(State Key Laboratory of Geological Processes and Mineral Resources,China University of Geosciences,Wuhan 430074,China);Chen Jianguo Automated Batch Mapping Solution for Serial Maps:A Case Study of Exploration Geochemistry Maps(Journal of Geology,ISSN1674-3636,CN32-1796/P,37(3),2013,p.456-464,2 illus.,2 tables,10 refs.)  相似文献   

17.
正20140962 Chen Fenning(Xi’an Institute of Geology and Mineral Resources,Xi’an710054,China);Chen Ruiming Late Miocene-Early Pleistocene Ostracoda Fauna of Gyirong Basin,Southern Tibet(Acta Geologica Sinica,ISSN0001-5717,CN11-1951/P,87(6),2013,p.872-886,6illus.,56refs.)  相似文献   

18.
PETROLOGY     
正1.IGNEOUS PETROLOGY20142008Cai Jinhui(Wuhan Center,China Geological Survey,Wuhan 430205,China);Liu Wei Zircon U-Pb Geochronology and Mineralization Significance of Granodiorites from Fuzichong Pb-Zn Deposit,Guangxi,South China(Geology and Mineral Resources of South China,ISSN1007-3701,CN42-1417/P,29(4),2013,p.271-281,7illus.,  相似文献   

19.
正20141205Cheng Weiming(State Key Laboratory of Resources and Environmental Information System,Institute of Geographic Sciences and Natural Resources Research,CAS,Beijing 100101,China);Xia Yao Regional Hazard Assessment of Disaster Environment for Debris Flows:Taking Jundu Mountain,Beijing as an  相似文献   

20.
正20141266Fan Chaoyan(Guangdong Provincial Key Laboratory of Mineral Resources and Geological Processes,Guangzhou 510275,China);Wang Zhenghai On Error Analysis and Correction Method of Measured Strata Section with Wire Projection Method(Journal of  相似文献   

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