大兴安岭北段漠河富源沟林场早侏罗世花岗岩——年代学、地球化学特征及构造意义     

胡军海  杨华本  周传芳  高晓琦  魏小勇  孙桐  李宇菡  马靖 《地质与资源》2018,27(3):224

通过对大兴安岭北段富源沟林场早侏罗世二长花岗岩进行岩相学、地球化学、LA-ICP-MS U-Pb定年研究,探讨其对该区构造演化的制约.该花岗岩主要由二长花岗岩组成,锆石测年结果显示,样品WJL030二长花岗岩结晶年龄为200±1Ma,样品WJL032二长花岗岩结晶年龄为202±1Ma,形成与早侏罗世.富源沟林场早侏罗世二长花岗岩为高钾钙碱性、偏铝质的I型花岗岩类,富集轻稀土和大离子亲石元素（Rb、K、Ba等）,亏损重稀土和高场强元素（Nb、Ta和P）.岩石为壳源成因,形成于俯冲环境,是玄武质下地壳部分熔融的产物.结合区域资料,花岗岩的侵位反映了研究区早侏罗世期间,漠河地区仍处于蒙古-鄂霍次克大洋板块俯冲于额尔古纳地块之下的构造环境.  相似文献   

滇西潞西地区晚寒武世岩浆构造热事件的新认识     

宋冬虎  刘兵  路永岩  刘晓玮  包佳凤  王燕  刘军平  孙柏东  田素梅 《地质与资源》2021,30(5):533-543

保山地块作为冈瓦纳大陆的重要组成部分,其西缘发育有以平河岩体为代表的大量早古生代侵入岩,但由于缺少野外调查资料,其地质意义存在长期争议.通过1：5万区域地质调查,详实的野外接触关系证实平河岩体存在两期侵入岩.沉积作用及年代学、岩石地球化学等赋予了其新的地质意义.潞西地区早期侵入岩主要岩石类型为二长花岗岩,应用LA-ICP-MS获得锆石U-Pb年龄为488.3±3.9 Ma.通过主、微量元素分析,其岩石属高温富黑云母含堇青石过铝花岗岩,属高钾钙碱系列岩石,具中等负Eu异常稀土特征,属"南岭型"花岗岩.结合沉积作用和区域地质构造背景,认为该期侵入岩为晚寒武世保山地块与腾冲地块碰撞拼合后上地壳部分熔融产物.  相似文献   

北秦岭西段胡店片麻状二长花岗岩LA-ICP-MS锆石U-Pb测年及其地质意义   总被引：2，自引：4，他引：2  

王洪亮  何世平  陈隽璐  徐学义孙 勇第五春荣李海平 《中国地质》2007,34(1):17-25

北秦岭西段陕西胡店片麻状细粒二长花岗岩中获得(1770±13)Ma的LA-ICP-MS单颗粒锆石微区U-Pb同位素年龄;岩石地球化学资料研究证明,该片麻状细粒二长花岗岩形成于板块边缘的俯冲-碰撞构造环境,岩浆源于部分熔融的中上地壳物质。该变形侵入体形成的地质构造背景及时代与太白岩基巩坚沟变形侵入体基本一致,代表了北秦岭造山带西段古元古代末、中元古代初期的一次强烈的构造岩浆事件。该事件与中国的吕梁运动时代大体相当,可能与Columbia超大陆的形成有一定的成因联系。这一新的资料,对研究北秦岭造山带元古宙大地构造格局、构造演化及中国大陆动力学具有重要意义。  相似文献   

Microchemical and Sr Isotopic Investigation of Zoned K-feldspar Megacrysts: Insights into the Petrogenesis of a Granitic System and Disequilibrium Crystal Growth   总被引：6，自引：0，他引：6  

GAGNEVIN  D.; DALY  J. S.; POLI  G.; MORGAN  D. 《Journal of Petrology》2005,46(8):1689-1724

K-feldspar megacrysts (Kfm) are used to investigate the magmaticevolution of the 7 Ma Monte Capanne (MC) monzogranite (Elba,Italy). Dissolution and regrowth of Kfm during magma mixingor mingling events produce indented resorption surfaces associatedwith high Ba contents. Diffusion calculations demonstrate thatKfm chemical zoning is primary. Core-to-rim variations in Ba,Rb, Sr, Li and P support magma mixing (i.e. high Ba and P andlow Rb/Sr at rims), but more complex variations require othermechanisms. In particular, we show that disequilibrium growth(related to variations in diffusion rates in the melt) may haveoccurred as a result of thermal disturbance following influxof mafic magma in the magma chamber. Initial ⁸⁷Sr/⁸⁶Sr ratios(I_Sr) (obtained by microdrilling) decrease from core to rim.Inner core analyses define a mixing trend extending towardsa high I_Sr–Rb/Sr melt component, whereas the outer coresand rims display a more restricted range of I_Sr, but a largerrange of Rb/Sr. Lower I_Sr at the rim of one megacryst suggestsmixing with high-K calc-alkaline mantle-derived volcanics ofsimilar age on Capraia. Trace element and isotopic profilessuggest (1) early megacryst growth in magmas contaminated bycrust and refreshed by high I_Sr silicic melts (as seen in theinner cores) and (2) later recharge with mafic magmas (as seenin the outer cores) followed by (3) crystal fractionation, withpossible interaction with hydrothermal fluids (as seen in therim). The model is compatible with the field occurrence of maficenclaves and xenoliths. KEY WORDS: Elba; monzogranite; K-feldspar megacrysts; zoning; magma mixing; trace element; Sr isotopes; petrogenesis  相似文献   

金平铜厂铜钼矿床赋矿岩体锆石LA-ICP-MS U-Pb年龄及意义   总被引：8，自引：1，他引：7  

黄波  梁华英  莫济海  谢应雯 《大地构造与成矿学》2009,33(4)

金平铜厂铜钼矿床赋矿岩体位于哀牢山-金沙江新生代成矿带南端,红河走滑断裂西侧,赋矿岩体主要由二长花岗斑岩及二长花岗岩组成。岩体锆石阴极发光图(CL)环带构造发育,不同环带U-Pb年龄在误差范围内基本一致。锆石LA-ICP-MS U-Pb年结果表明赋矿岩体主要是35.1±0.3Ma形成的。含矿岩体形成与印度板块与欧亚板块碰撞产生的红河-哀牢山左行走滑断裂活动有关。  相似文献   

格咱岛弧带热林二长花岗岩的岩石成因及动力学背景:岩石地球化学、年代学及Hf同位素约束   总被引：1，自引：0，他引：1  

杨富成 《地质与勘探》2017,53(2):283-289

云南格咱岛弧带是近年来西南三江特提斯构造带新发现的重要Cu-Mo多金属成矿带之一,燕山晚期伴随着碰撞型岩浆侵入作用形成了斑岩-矽卡岩型Mo(Cu)和热液型W(Mo)矿床。其中,热林Mo-Cu矿床是区内燕山晚期成岩成矿作用的代表性矿床。本文对热林Mo-Cu矿床二长花岗岩进行了锆石LA-ICP-MS U-Pb定年、岩石地球化学和Lu-Hf同位素分析。结果表明,热林二长花岗岩属高硅(SiO_2=69.88%~74.58%)、富碱(K_2O+Na_2O=7.24%~8.62%)的高钾钙碱性、准铝质(A/CNK=0.93~1.05)花岗岩。岩石具有较高的稀土元素总量(∑REE为(80.72~284.85)×10-6,平均值为190.86×10-6),轻重稀土元素分馏程度较高,具Eu负异常(δEu=0.46~0.83),相对富集LREE和LILE(K、Rb),亏损HFSE(Nb、Ta、P、Ti)和HREE,具埃达克岩亲和性。本文两件二长花岗岩样品的锆石U-Pb年龄分别为79.4±2.0 Ma(MSWD=1.1)、78±1.6 Ma(MSWD=1.8),代表了热林Mo-Cu矿床二长花岗岩的岩浆侵位结晶时代为燕山晚期;锆石的εHf(t)值为-12.12~-4.41,均小于0,二阶段模式年龄峰值在1.35~1.4Ga之间,揭示了热林二长花岗岩来源于中元古代地壳基底的深熔作用。研究表明,热林二长花岗岩是碰撞后的陆内伸展环境下壳源岩浆侵位结晶的产物,并伴随有成矿热液活动形成了Mo-Cu多金属矿化,最终形成热林Mo-Cu多金属矿床,其成岩成矿作用与燕山期碰撞造山作用密切相关。  相似文献   

东昆仑五龙沟地区猴头沟二长花岗岩年龄、成因、源区及其构造意义   总被引：5，自引：0，他引：5  

严威  邱殿明  丁清峰  刘飞 《吉林大学学报(地球科学版)》2016,46(2):443-460

对东昆仑造山带五龙沟地区的猴头沟二长花岗岩开展了详细的岩相学、地球化学、锆石U-Pb年龄及Hf同位素的分析测试和研究工作。LA-ICP-MS锆石U-Pb测年表明,猴头沟二长花岗岩的²⁰⁶Pb/²³⁸U加权平均年龄值为(419.0±1.9)Ma,属于晚志留世。岩石地球化学数据表明:猴头沟二长花岗岩属于高钾钙碱性系列的A₂型花岗岩,富SiO₂、K₂O、Y(>33×10^-6)和Yb,贫Al₂O₃和Sr(<100×10^-6),具有强烈的负铕异常;Rb、Th、U、La、Ce、Nd相对富集,Nb、Ta、Ba、Sr、P、Ti亏损。锆石的Hf同位素研究表明,其ε_Hf(t)值为0.2~5.1,对应二阶段模式年龄(T_DM2)为1066~1371 Ma,由此推测花岗岩源区来自中元古代镁铁质下地壳部分熔融。微量元素及其特征比值的构造判别图解表明,猴头沟二长花岗岩形成于早古生代晚志留世东昆仑造山旋回的造山后伸展阶段。据此认为,原特提斯洋在东昆仑地区的最晚闭合时限应该不晚于晚志留世末期(~419 Ma),而不是前人认为的早泥盆世。  相似文献   

中国东北额尔古纳地块新太古代岩浆事件钻孔片麻状二长花岗岩锆石LA-ICP-MS测年证据   总被引：5，自引：0，他引：5  

邵军  李永飞  周永恒  王宏博  张璟 《吉林大学学报(地球科学版)》2015,45(2):364-373

额尔古纳地块基底岩石时代与构造属性一直颇受争议。笔者对额尔古纳地块南部比列亚铅锌多金属矿区ZK6301钻孔226 m片麻状二长花岗岩岩心进行了锆石LA-ICP-MS定年。测试结果显示,24个测试点的数据均在谐和线上,²⁰⁷Pb/²⁰⁶Pb年龄包括4个不同年龄区段,分别为:2 549~2 562 Ma(加权平均年龄为(2 555±19) Ma,MSWD=0.17,n=3),2 596~2 624 Ma(加权平均年龄为(2 606±17) Ma,MSWD=0.032,n=17),2 688~2 715 Ma(加权平均年龄为(2 702±18) Ma, MSWD=0.70,n=3),2 786 Ma(n=1)。通过锆石的Th,U质量分数与Th/U值分析,²⁰⁷Pb/²⁰⁶Pb年龄((2 606±17) Ma)代表了该片麻状二长花岗岩的结晶年龄;²⁰⁷Pb/²⁰⁶Pb年龄((2 549~2 562) Ma)很可能代表了构造热事件的作用年龄;本次报道的岩石结晶年龄,揭示了额尔古纳地块上存在新太古代的结晶基底。结合前人研究资料分析可知,额尔古纳地块上该期变质结晶基底可能在该地块的南、北部均有分布,并且得尔布干断裂可能并非该地块的南部边界。综合分析前寒武纪古老地块的演化历史可得出,额尔古纳地块经历了全球大陆构造旋回演化的完整过程。  相似文献   

西藏厅宫矿区始新世斑岩的厘定及其地质意义   总被引：3，自引：0，他引：3  

杜等虎  杨志明  李秋耘  刘云飞  格桑平措  王海勇 《矿床地质》2012,31(4):745-757

厅宫铜矿的勘查工作一直是围绕英云闪长斑岩、斑状二长花岗岩等几套斑岩进行的,而未对这几期岩浆岩的年代及成因做过详细评价,并且一直认为这几套斑岩为中新世岩浆岩.笔者通过研究,发现在矿区大面积出露的斑状二长花岗岩并非中新世岩浆岩,而是始新世岩浆岩[(48.88±0.53) Ma],为冈底斯岩基的重要组成部分.文章通过精确的SIMS锆石微区O同位素和LA-MC-ICPMS锆石Hf同位素分析,获得斑状二长花岗岩锆石εHf(t)值变化于4.4～8.4之间,δ18O值变化于5.81‰～6.62‰之间,显示出亏损的地球化学特征,表明该岩体可能起源于新生地壳的部分熔融或者楔形地幔部分熔融形成的岩浆发生分异结晶后的产物.通过对比研究还发现,厅宫矿区岩浆岩组合特征与矿集区内冲江、白容及岗讲矿床类似.因此,在进行找矿勘查工作部署时,应充分考虑这套斑状二长花岗岩与矿化的关系,对缩小勘查范围具有重要的现实意义.  相似文献   

Zircon U-Pb ages,geochemistry, and Sr-Nd-Pb-Hf isotopic compositions of the Pinghe pluton,Southwest China: implications for the evolution of the early Palaeozoic Proto-Tethys in Southeast Asia     

《International Geology Review》2012,54(7):885-904

The geological record of the Neoproterozoic to early Palaeozoic Proto-Tethyan Ocean in Southeast Asia is not clear. To better constrain the evolution of the Proto-Tethys, we present new geochronology, geochemistry, and petrology of the late Cambrian to Ordovician Pinghe pluton monzogranite from the Baoshan block, western Yunnan, southwest China. Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) analyses of four zircon samples yield ages of 482–494 and 439–445 Ma for the pluton, interpreted as two episodes within one magmatic event accompanying the whole process of subduction–collision–orogeny between buoyant blocks and oceanic crust of the Proto-Tethys. The monzogranite belongs to the strong peraluminous, high-K, calc-alkaline series and shows characteristics of both I-type and S-type granitic rocks. It is characterized by extremely high Rb/Sr and Rb/Ba but low TiO₂, MgO, FeOt, and CaO/Na₂O ratios. The monzogranite is also moderately enriched in light rare earth elements (LREEs), depleted in heavy rare earth elements (HREEs), lacks HREE fractionation, and has strongly negative Eu (Eu/Eu* = 0.06–0.49), Ba, Nb, Ta, Sr, and Ti anomalies. Whole-rock ε_Nd(t) and ε_Hf(t) values range from ?8.7 to ?11.6 and ?5.55 to ?9.58, respectively. Nd and Hf two-stage model ages range from 1.66 to 2.06 Ga and 2.14 to 3.00 Ga, respectively, with variable radiogenic ²⁰⁶Pb/²⁰⁴Pb_(t) (16.547–18.705), ²⁰⁷Pb/²⁰⁴Pb_(t) (15.645–15.765), and ²⁰⁸Pb/²⁰⁴Pb_(t) (38.273–38.830). These signatures suggest that the monzogranite magma was derived from partial melting of heterogeneous metapelite, which was generated from Neoarchean to Palaeoproterozoic materials mixed with basaltic magma. The monzogranite magma underwent crystallization differentiation of plagioclase, K-feldspar, and ilmenite. Magmatism to form the Pinghe pluton occurred in a post-collisional setting. Based on the comparison of coeval granites throughout adjacent regions (e.g. Himalayan orogen, Lhasa Terrane, and parts of Gondwana supercontinent), we propose that the Baoshan block was derived from the northern Australian Proto-Tethyan Andean-type active continental margin of Gondwana and experienced subduction of the Proto-Tethyan oceanic crust and accretion of an outboard micro-continent. The Pinghe pluton could have formed when a subducting oceanic slab broke off during collision.  相似文献