西藏甲玛矿床南坑高分异Ⅰ型花岗斑岩及黑云母矿物学特征     

陈国良  张忠坤  孙渺  林彬  赫健  唐攀  格桑顿珠  苏贵喆  任绍渊  胡海涛 《矿物岩石地球化学通报》2021,40(2):411-424

高硅花岗岩对于理解浅部岩浆房的行为具有重要意义。本文对西藏甲玛矿区南坑矿段的花岗斑岩开展了岩相学、岩石地球化学及黑云母矿物学研究。结果显示,该花岗斑岩具有高SiO2(73.39%~77.99%)、高K2O(4.34%~6.45%)和低P2O5(0.03%~0.06%)特征,铝饱和指数为0.97~0.98,富集Rb、Th、U和Pb,明显亏损Ba、Nb、Ta、Sr、P、Ti和Eu等,属准铝质高分异I型花岗岩类;其中的黑云母具有高Al2O3(9.87%~10.92%)、高MgO(13.38%~14.64%)、高F(0.56%~1.11%)和高Cl(0.07%~0.12%)特征,Mg#为0.61~0.63,属镁质黑云母,黑云母源区为壳幔混合源。研究认为,该区花岗斑岩可能为甲玛矿区浅部埃达克质二长花岗斑岩的岩浆经矿物结晶分异演化出高硅残余熔体,并以岩脉形式上侵就位,而残留在岩浆房的物质结晶形成似斑状二长花岗岩,二者构成互补的关系,即主体为似斑状二长花岗岩,补体为高分异花岗斑岩。  相似文献   

青海省那陵郭勒河中游晚三叠世侵入岩地球化学特征及地质意义     

吉明甲  魏丽琼  徐博  刘博  白洪溪  陈晓琳  李兄 《西北地质》2021,(1)

那陵郭勒河中游位于东昆仑西段祁漫塔格地区,分布着大量的花岗岩。对该地区晚三叠世侵入岩的研究有助于认识东昆仑造山带印支期构造-岩浆演化历史。对研究区内花岗岩进行了岩石学、年代学及岩石地球化学分析。分析结果表明,研究区花岗闪长岩和二长花岗斑岩锆石LA-ICP-MS U-Pb年龄分别为(225.7±1)Ma、(213.74±1)Ma,为晚三叠世岩浆活动产物。岩石地球化学分析结果显示,该地区晚三叠世侵入岩属高钾钙碱性系列,饱和铝指数显示为偏铝质到过铝质,富集Rb、Th、K等大离子亲石元素和轻稀土元素,明显亏损Nb、P、Ti等高场强元素。花岗岩具有I型花岗岩特征,具有板块俯冲阶段的特征。通过分析认为岩浆岩形成于板块碰撞前的火山弧环境中。  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   

三江造山带义敦岛弧中段格聂（南）花岗岩体地球化学特征及地质意义   总被引：2，自引：0，他引：2  

马比阿伟  木合塔尔·扎日  文登奎  张明春 《地质学报》2015,89(2):305-318

夹持于甘孜—理塘结合带与金沙江结合带之间的义敦弧岩浆岩带上发育了3条纵贯南北的造山花岗岩带,其中:中带形成了由20余个岩体组成的雀而山—格聂花岗岩带和相关的银、锌、铅-锌多金属矿床。本文对格聂(南)花岗岩体进行研究,发现其岩石类型为花岗闪长岩、二长花岗岩和钾长花岗岩三类,以二长花岗岩为主体。锆石LA-ICP-MS U-Pb定年结果表明格聂花岗岩的成岩年龄为89.9±3.6Ma。地球化学研究表明,岩石中主量元素化学成分具有富硅、富铝、低钠高钾的特征,为典型的S型花岗岩。铝饱和指数ASI1,指示岩浆源自地壳;(CaO)%/(Na2O)%值等于0.1左右,表明源岩为大陆地壳沉积岩区的泥质岩。稀土总量均值228.83×10-6,稀土配分曲线呈略右倾近直线海鸥型,与地壳熔融型花岗岩形态一致。轻重稀土分馏不明显;铕出现明显负异常(δEu=0.13),显示岩浆分异结晶作用强烈。微量元素蛛网图上明显亏损大离子亲石元素Sr;富集高场强元素U。Rb/Sr平均比值14.97,表明格聂花岗岩的源岩为上部陆壳。结合Rb-(Y+Nb)图解、(Rb/30)-Hf-(Ta×3)图解、R1-R2变异图解,格聂南岩体形成于后碰撞造山环境,应是甘孜-理塘洋盆和金沙江洋盆闭合后,造山后伸展作用活动的产物。  相似文献   

格陵兰岛西南部Nassaq地区辉钼矿Re-Os年龄及意义   总被引：1，自引：0，他引：1  

赵元艺  聂凤军  李振清  李小赛  卢伟  APPEL Peter W 《地质论评》2015,61(2):457-462

格陵兰矿产资源丰富,种类繁多,目前已探明的金属矿点(床)有800多个,具有巨大的找矿潜力,世界主要矿业公司多数对格陵兰的找矿与开发表现出积极态度。因此,选择典型地区开展深入研究对进一步找矿有重要的理论指导意义。格陵兰西南部的那萨克(Nassaq)地区交通较为便利,本文在对该地区系统的野外地质特征研究基础上,采集了含辉钼矿斜长角闪岩样品,并从中选择代表性样品,进行辉钼矿Re-Os年代学研究,为其成矿作用及相关问题的研究提供基本依据。该地区辉钼矿的形成年龄为2553 Ma,为新太古界末期的产物,其矿化是Qorqut花岗岩侵入时(2550Ma)所形成,在格陵兰西南部应重视Qorqut花岗岩有关的辉钼矿的找矿与评价工作。  相似文献   

阿拉善宗乃山岩体东南缘花岗岩LA-ICP-MS锆石U-Pb年龄与地球化学特征   总被引：2，自引：0，他引：2  

谢奋全  王黎栋  李琦  石朝霞  陈学兵  韦岸 《岩矿测试》2015,34(3):375-382

阿拉善宗乃山岩体东南缘分布多种类型的花岗岩,本文主要采用岩相学、激光剥蚀电感耦合等离子体质谱(LA-ICP-MS)锆石U-Pb定年、岩石地球化学等技术手段,对宗乃山岩体东南缘岩石类型、年代学、源岩特征以及构造背景进行了研究。结果表明:岩石类型主要为碱性-钙碱性准铝质花岗岩和闪长岩;单颗粒锆石分析获得黑云母斜长花岗岩年龄为236.8±1.9 Ma~249.7±2.6 Ma,片麻状花岗岩年龄为268.1±1.1 Ma,岩体成岩时期主要为华力西晚期和印支期早期,具有多期侵入的特征。该岩体岩石源岩为I型花岗岩,源于地壳火山弧区和同碰撞区,表明由于洋壳俯冲作用,在宗乃山东南缘形成了岛弧花岗岩侵入体。LA-ICP-MS锆石U-Pb定年技术为洋壳俯冲提供了年代学约束,确定了研究区碰撞时间为早于236.8±1.9 Ma。  相似文献   

湖南宝峰仙花岗岩地球化学特征与锆石SHRIMP U-Pb定年   总被引：1，自引：1，他引：0  

陈希清  付建明  程顺波  马丽艳  卢友月 《矿床地质》2015,34(3):602-616

湘东南宝峰仙地区发育3个小规模花岗岩体,岩性均为黑云母二长花岗岩,与南岭产有大型-超大型钨锡多金属矿床的骑田岭和千里山岩体位于同一成矿带内,相距不远。文章通过对宝峰仙岩体进行锆石SHRIMP UPb测年,获得(细)中粒斑状黑云母二长花岗岩(早期)和细粒黑云母花岗岩(晚期)的形成年龄分别为(147.0±4.0)Ma(MSWD=1.6)和(141.3±3.3)Ma(MSWD=1.09),为燕山期构造岩浆活动的产物。这2种花岗岩具有高w(Si)(平均75.11%)、富w(K2O)(平均5.07%)、低w(Ti O2)、w(Mg O)、w(Ca O),10000×Ga/Al值(大于2.6)较高、δEu较小的特点,为铝质A型花岗岩的岩石地球化学特征。宝峰仙花岗岩的εNd(t)偏高,T2DM偏小,显示在花岗岩成岩过程中有幔源组分参与,与千里山和骑田岭相似。花岗岩石成矿元素W、Sn、Pb、Zn等含量偏高,且岩体与围岩接触带的岩石蚀变较强、钨锡矿化点广泛分布。综合分析宝峰仙地区花岗岩成岩年龄、岩石地球化学特征及其所处构造位置,认为该区具有较大的钨锡多金属找矿潜力。  相似文献   

桂北苗儿山地区高岭印支期花岗岩及石英脉型钨成矿作用   总被引：1，自引：0，他引：1  

张迪  张文兰  王汝成  储著银  龚名文  蒋桂新 《地质论评》2015,61(4):817-834

高岭石英脉型钨矿床位于桂北苗儿山—越城岭岩体南部,根据花岗岩中含有斑晶与否,将其与矿关系密切的花岗岩分为两种:一种为中细粒似斑状二云母花岗岩,一种为中细粒二云母花岗岩;岩石地球化学表明,成矿花岗岩具有高硅、准铝—弱过铝、高分异S型特征。岩体稀土总量中等—偏低,富集轻稀土、Cs、Rb、Th、U、Pb元素,相对亏损重稀土、Ba、Sr和Ti元素;利用锆石LA-ICP-MS U-Pb原位定年方法,对两种花岗岩中的锆石进行了定年分析,获得侵位年龄分别为224.9±1.4、220.2±1.6Ma,该数据为印支期岩浆活动的产物。除此之外,本文首次对高岭石英脉型钨矿的白钨矿石进行了Sm-Nd同位素分析,获得了钨成矿年龄为212±20Ma,数据表明钨成矿作用也发生在印支期,这再一次证实了南岭西部的苗儿山与越城岭地区存在较广泛的印支期成岩与成矿作用。对钨矿石的镜下和电子探针背散射图像的详细研究表明,高岭钨矿经历了两个主要的成矿阶段:(1)黑钨矿—白钨矿—石英阶段,(2)白钨矿(黑钨矿)—硫化物—石英阶段。白钨矿εNd(t)=-8.88~-9.39,为负值,这与成矿母岩属S型花岗岩相吻合,它们都属于古老壳源物质重熔作用的产物,而形成白钨矿的物质,则来自于重熔型花岗岩岩浆高度分异演化形成的富含成矿元素的成矿流体。  相似文献   

LA-ICP-MS Zircon U-Pb Geochronology of the Fine-grained Granite and Molybdenite?Re-Os?Dating in the Wurinitu Molybdenum Deposit, Inner Mongolia, China   总被引：3，自引：0，他引：3  

LIU Cui  DENG Jinfu  KONG Weiqiong  XU Liquan  ZHAO Guochun  LUO Zhaohu  LI Ning 《《地质学报》英文版》2011,85(5):1057-1066

The Wurinitu molybdenum deposit, located in Honggor, Sonid Left Banner of Inner Mongolia, China, is recently discovered and is considered to be associated with a concealed fine-grained granite impregnated with molybdenite.?The wall rocks are composed of Variscan porphyritic-like biotite granite and the Lower Ordovician Wubin’aobao Formation.?LA-ICP-MS zircon U-Pb dating of the fine-grained granite reveals two stages of zircons,?one were formed at 181.7±7.?4 Ma and?the other at 133.6±3.3 Ma. The latter age is believed to be the formation age of the fine-grained granite, while the former may reflect the age of inherited zircons, based on the morphological study of the zircon and regional geological setting. The Re-Os model age of molybdenite is 142.2±2.5?Ma, which is older than the diagenetic age of the fine-grained granite.?Therefore the authors believe that the metallogenic age of the Wurinitu molybdenum deposit should be?nearly 133.6±3.3 Ma or slightly later, i.e., Early Cretaceous.?Combined with regional geological background research, it is speculated that the molybdenum deposits were formed at the late Yanshanian orogenic cycle in the Hingganling-Mongolian orogenic belt, belonging to the relaxation epoch posterior to the compression and was associated with the closure of the Mongolia-Okhotsk?Sea.  相似文献   

内蒙古宝音图晚二叠世—晚三叠世花岗岩岩石化学特征及其构造环境   总被引：1，自引：0，他引：1  

赵勇  蔡向民  李亚林  徐吉祥  孙永华 《矿物岩石》2011,31(1)

宝音图花岗岩基位于华北地台北缘西段,针对其中牙马图岩体、罕乌拉岩体及布格道苏绍崩岩体等的岩石地球化学研究与年代学测定,结果表明岩体时代分别为261Ma±1.3 Ma,220.9 Ma±0.3 Ma和204.9 Ma±5.9 Ma,系晚二叠世—晚三叠世侵入岩体,其岩石类型主要为黑云母花岗闪长岩、斑状黑云母花岗岩和二云母花岗岩,其中晚二叠世花岗闪长岩Na2O/K2O平均值为2.06,A/CNK为0.96~1.15,平均值为1.03,里特曼指数(σ)平均值为1.9,总体属过铝质钙碱性岩;晚三叠世花岗岩Na2O/K2O平均值为0.82,A/CNK为0.92~1.16,平均值为1.03,里特曼指数(σ)为2.18,属过铝质钙碱性岩。岩石化学构造环境分析表明,晚二叠世—晚三叠世早期岩浆活动是俯冲造山过程中形成的具有岛弧性质的闪长岩类和花岗岩类,而晚三叠世晚期岩浆作用是与之有关的造山晚期陆缘花岗岩类。  相似文献