Geochronology,geochemistry, and mineralization of the granodiorite porphyry hosting the Matou Cu–Mo (±W) deposit,Lower Yangtze River metallogenic belt,eastern China     

《Journal of Asian Earth Sciences》2014

Porphyry and skarn Cu–Fe–Au–Mo deposits are widespread in the Middle and Lower Yangtze River metallogenic belt (MLYMB), eastern China. The Matou deposit has long been regarded as a typical Cu–Mo porphyry deposit within Lower Yangtze part of the belt. Recently, we identified scheelite and wolframite in quartz veins in the Matou deposit, which is uncommon in other porphyry and skarn deposits in the MLYMB. We carried out detailed zircon U–Pb dating and geochemical and Sr–Nd–Hf isotopic studies of the granodiorite porphyry at Matou to define any differences from other ore-related granitoids. The porphyry shows a SiO₂ content ranging from 61.85 wt.% to 65.74 wt.%, K₂O from 1.99 wt.% to 3.74 wt.%, and MgO from 1.74 wt.% to 2.19 wt.% (Mg^# value ranging from 45 to 55). It is enriched in light rare earth elements and large ion lithophile elements, but relatively depleted in Nb, Ta, Y, Yb and compatible trace elements (such as Cr, Ni, and V), with slight negative Eu anomalies (Eu/Eu^* = 0.88–0.98) and almost no negative Sr anomalies. Results of electron microprobe analysis of rock-forming silicate minerals indicate that the Matou porphyry has been altered by an oxidized fluid that is rich in Mg, Cl, and K. The samples show relatively low ε_Nd(t) values from −7.4 to −7.1, slightly high initial ⁸⁷Sr/⁸⁶Sr values from 0.708223 to 0.709088, and low ε_Hf(t) values of zircon from −9.0 to −6.5, when compared with the other Cu–Mo porphyry deposits in the MLYMB. Zircon U–Pb dating suggests the Matou granodiorite porphyry was emplaced at 139.5 ± 1.5 Ma (MSWD = 1.8, n = 15), which is within the age range of the other porphyries in the MLYMB. Although geochemical characteristics of the Matou and other porphyries in the MLYMB are similar and all adakitic, the detrital zircons in the samples from Matou suggest that Archean lower crust (2543 ± 29 Ma, MSWD = 0.25, n = 5) was involved with the generation of Matou magma, which is different from the other porphyries in the belt. Our study suggests that the Matou granodiorite porphyry originated from partial melting of thickened lower crust that was delaminated into the mantle, similar to the other porphyries in the MLYMB, but it has a higher proportion of lower crustal material, including Archean rocks, which contributed to the formation of the porphyry and related W-rich magmatic-hydrothermal system.  相似文献   

Neoproterozoic granitic activities in the Xingdi plutons at the Kuluketage block,NW China: Evidence from zircon U–Pb dating,geochemical and Sr–Nd–Hf isotopic analyses     

《Journal of Asian Earth Sciences》2014

Neoproterozoic igneous rocks are widely distributed in the Kuluketage block along the northern margin of the Tarim Craton. However, the published literature mainly focuses on the ca. 800 Ma adakitic granitoids in the area, with the granites that intrude the 735–760 Ma mafic–ultramafic rocks poorly studied. Here we report the ages, petrography and geochemistry of two granites in the Xingdi mafic–ultramafic rocks, in order to construct a new view of the non-adakitic younger granites. LA-ICP-MS zircon U–Pb dating provided weighted mean ²⁰⁶Pb/²³⁸U ages of 743.0 ± 2.5 Ma for the No.I granite (G1) and 739.0 ± 3.5 Ma for the No.II granite (G2). A clear core-rim texture of similar age and a high zircon saturation temperature of ca. 849 ± 14 °C were observed for the No.I granite; in contrast, G2 has no apparent core-rim texture but rather inherited older zircons and a lower zircon saturation temperature of ca. 763 ± 17 °C. Geochemical analysis revealed that G1 is an alkaline A-type granite and G2 is a high-K calc-alkaline I-type granite. Both granites share similar geochemical characteristics of arc-related magmatic rocks and enriched Sr–Nd–Hf isotopes, likely due to their enriched sources or mixing with enriched magma. Whereas G1 and its host mafic rocks form typical bimodal intrusions of the same age and similar Sr–Nd–Hf isotope compositions, G2 is younger than its host mafic rocks and its Sr–Nd–Hf isotope composition indicates a lower crust origin. Although they exhibit arc-related geochemical features, the two granites likely formed in a rift setting, as inferred from thier petrology, Sr–Nd–Hf isotopes and regional tectonic evolution.  相似文献   

Geochemistry,and zircon U–Pb and molybdenite Re–Os geochronology of Jilongshan Cu–Au deposit,southeastern Hubei Province,China     

A‐Juan Pang  Sheng‐Rong Li  M. Santosh  Qing‐Yu Yang  Bao‐Jian Jia  Cheng‐Dong Yang 《Geological Journal》2014,49(1):52-68

The Jilongshan skarn Cu–Au deposit is located at the Jiurui ore cluster region in the southwestern part of the Middle–Lower Yangtze River valley metallogenic belt. The region is characterized by NW‐, NNW‐ and EW‐trending faults and the mineralization occurs at the contact of lower Triassic carbonate rocks and Jurassic granodiorite porphyry intrusions. The intrusives are characterized by SiO₂, K₂O, and Na₂O concentrations ranging from 61.66 to 67.8 wt.%, 3.29 to 5.65 wt.%, and 2.83 to 3.9 wt.%, respectively. Their A/CNK (A/CNK = n(Al₂O₃)/[n(CaO) + n(Na₂O) + n(K₂O)]) ratio, δEu, and δCe vary from 0.77 to 1.17, 0.86 to 1, and 0.88 to 0.96, respectively. The rocks show enrichment in light rare earth elements ((La/Yb)_N = 7.61–12.94) and large ion lithophile elements (LILE), and depletion in high field strength elements (HFSE), such as Zr, Ti. They also display a peraluminous, high‐K calc‐alkaline signature typical of intrusives associated with skarn and porphyry Cu–Au–Mo polymetallic deposits. Laser ablation inductively coupled plasma spectrometry (LA‐ICP‐MS) zircon U–Pb age indicates that the granodiorite porphyry formed at 151.75 ± 0.70 Ma. A few inherited zircons with older ages (677 ± 10 Ma, 848 ± 11 Ma, 2645 ± 38 Ma, and 3411 ± 36 Ma) suggest the existence of an Archaean basement beneath the Middle–Lower Yangtze River region. The temperature of crystallization of the porphyry estimated from zircon thermometer ranges from 744.3 °C to 751.5 °C, and 634.04 °C to 823.8 °C. Molybdenite Re–Os dating shows that the Jilongshan deposit formed at 150.79 ± 0.82 Ma. The metallogeny and magmatism are correlated to mantle–crust interaction, associated with the subduction of the Pacific Plate from the east. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

海南岛晚中生代花岗闪长岩及其包体的锆石U-Pb定年及构造意义   总被引：1，自引：0，他引：1       下载免费PDF全文

唐立梅  陈汉林  董传万 《地质科学》2014,(1):259-274

海南岛晚中生代的岩浆活动十分强烈,代表性的岩体有千家岩体、屯昌岩体和保城岩体,岩体岩性为花岗闪长岩,其中包含大量的闪长岩包体。系统的LA-ICP-MS锆石U-Pb定年结果表明,花岗闪长岩及包体均形成于101 Ma,为双峰式侵入岩,由来自地幔的高温基性岩浆注入下地壳较酸性的长英质岩浆,两种岩浆同时上侵冷却形成。它们形成的构造环境为板内拉张环境,指示了海南岛于101 Ma处于强烈的岩石圈减薄阶段,这与晚中生代太平洋板块俯冲引起的弧后拉张有关。  相似文献   

东准造山带原泥盆系的形成时代及源区：碎屑锆石U-Pb年代学证据   总被引：1，自引：0，他引：1       下载免费PDF全文

聂峰  田晓丽  李振生 《地质科学》2014,(2):695-717

新疆东准地区晚古生代地层出露广泛,其沉积时限的精确限定对理解中亚造山带的增生和拼贴过程、确立该地区构造框架及油气开发具有深远意义。然而,目前的研究主要集中于岩浆岩方面,对于晚古生代地层时代及其空间展布的研究则相对缺乏,特别是石炭系和泥盆系沉积地层标定较为模糊。为此,本文选取了3个原泥盆系砂岩进行了细致的野外剖面测制、岩石学观测和碎屑锆石U-Pb年代学分析。研究显示：原泥盆纪砂岩的最年轻碎屑锆石年龄为346～312 Ma,碎屑锆石年龄谱图分为：380～310 Ma（晚泥盆世-早石炭世,71.8%）、445～385 Ma（志留纪-早-中泥盆世,11.7%）、480～450 Ma（奥陶纪,3.9%）、540～485 Ma（寒武纪,4.5%）和前寒武纪年龄段（8.1%）,碎屑锆石年龄谱图区域上具有由南向北、由西向东呈简单化趋势且晚古生代年龄比重增加。结合该区岩浆岩年代学研究成果,将研究区原泥盆系沉积时代重新厘定到晚石炭系早-中期,认为东准地区的碰撞拼贴时间应发生于晚石炭世,并非是不同期次碰撞拼贴之产物。  相似文献   

鄂尔多斯盆地延长组长7段凝灰岩锆石U-Pb年龄、Hf同位素组成特征及其地质意义   总被引：9，自引：3，他引：6  

张辉  彭平安  张文正 《岩石学报》2014,30(2):565-575

鄂尔多斯盆地延长组长7优质烃源层中广泛分布了薄层和纹层状凝灰岩,凝灰岩中锆石U-Pb同位素年代学研究表明,长7段凝灰岩结晶年龄为234Ma左右。对比勉略缝合带、南秦岭的花岗岩的年龄,三叠系延长组凝灰岩应该形成于俯冲阶段。锆石的Hf同位素分析表明延长组长7段凝灰岩主要来自地壳岩石部分熔融,并且有一定的地幔物质加入。Hf同位素二阶段模式年龄大部分集中在1.1~1.3Ga,其中以1.2Ga为主峰,表明延长组凝灰岩主要来自元古代增生的地壳物质,在物质组成和时代上可能类似于南秦岭基底中的耀岭河群基性火山岩和郧西群酸性的混合。  相似文献   

内蒙古道伦达坝铜钨多金属矿黑云母花岗岩年代学、地球化学特征及其地质意义   总被引：10，自引：3，他引：7  

周振华  欧阳荷根  武新丽  刘军  车合伟 《岩石学报》2014,30(1):79-94

内蒙古道伦达坝铜钨多金属矿是大兴安岭南段近年来新发现的一个铜、钨、锡共生的多金属矿床,成矿与中粗粒黑云母花岗岩密切相关,但其形成时代还存在较大争议,对岩浆来源缺乏足够的研究。本文对道伦达坝矿床内黑云母花岗岩进行了系统的岩石地球化学、年代学、Hf-Pb同位素地球化学组成测试。道伦达坝黑云母花岗岩SiO2含量为65.42%～67.41%,富铝、钾,A/NCK值为1.08～1.27,CIPW标准矿物刚玉含量较高(1.82%～4.08%),岩石属于过铝质S型花岗岩。微量、稀土元素组成表现出的轻稀土富集、重稀土亏损型式和Eu负异常以及明显的Nb、Ta、Sr、Ti亏损的特点显示为壳源成因的火山弧花岗岩。LA-ICP-MS锆石U-Pb测年结果表明其形成年龄为292.1±0.84Ma(MSWD=1.18)～292.5±0.88Ma(MSWD=0.46)。Hf同位素测试结果显示,道伦达坝黑云母花岗岩的εHf(t)=-0.8～+13.3,176Hf/177Hf比值(0.282643～0.282804)偏低,二阶段Hf同位素模式年龄较高(740～1024Ma)。全岩Pb同位素组成较均一,206Pb/204Pb介于18.416～18.766,207Pb/204Pb介于15.519～15.542,208Pb/204Pb变化在38.238～39.460。黑云母花岗岩为早二叠世西伯利亚板块南缘俯冲增生背景下的产物,主要源自从亏损地幔新增生的年轻地壳物质的部分重熔,在侵位过程中可能受到了残留的古地壳或岩石圈地幔的混染。古生代是兴蒙造山带的一个重要的成矿阶段,矿化以岛弧或活动大陆边缘背景下的斑岩-矽卡岩-热液脉型铜钼金多金属矿床为主。  相似文献   

甘肃北山红石山蛇绿岩锆石U-Pb年代学研究及构造意义   总被引：15，自引：7，他引：8  

王国强  李向民  徐学义  余吉远  武鹏 《岩石学报》2014,30(6):1685-1694

红石山蛇绿岩位于中蒙边境附近,出露于红石山-百合山-蓬勃山蛇绿混杂岩带最西段。岩石地球化学分析表明,红石山蛇绿岩中的玄武岩主量、微量及稀土元素皆显示类似MORB型玄武岩的地球化学特征,表现为低Na₂O+K₂O（2.99%）和P₂O₅（0.08%）,中等含量TiO₂（1.46%）;LREE球粒陨石标准化分配型式具平坦型和轻稀土略微富集的特征。微量元素原始地幔标准化分配型式显示出富集大离子亲石元素（Rb、K）的特征,HFSE变化相对较为稳定。红石山蛇绿岩中的辉长岩的LA-ICP-MS锆石U-Pb同位素定年结果显示,其形成时代为346.6±2.8Ma,代表该蛇绿岩形成时代,即为早石炭世。结合前人研究成果,笔者认为红石山蛇绿岩可能为石炭纪大陆裂谷向大洋转化的构造环境下形成的初始小洋盆,其向西可与新疆境内的巴音沟蛇绿岩对比,二者同属“红海型”洋盆初始洋壳的地质记录。  相似文献   

北冈底斯带日土县-拉梅拉山口花岗岩体的岩石地球化学特征、锆石U-Pb测年及Hf同位素组成   总被引：2，自引：2，他引：0  

关俊雷  耿全如  王国芝  彭智敏  张璋  寇福德  丛峰  李娜 《岩石学报》2014,30(6):1666-1684

对西藏西部日土县城以南-拉梅拉山口一带的花岗岩体开展了详细的岩相学、岩石地球化学和锆石U-Pb年代学及Hf同位素研究。所有样品铝饱和指数A/CNK集中在0.76~1.0之间,为准铝质类型。CIPW标准矿物组合为Q+Or+Ab+An+Di（或C）+Hy。在稀土元素配分图中呈现出右倾缓倾斜型的特征,轻稀土元素富集并出现较强的分馏作用,重稀土元素无分馏-轻微分馏。δEu在0.56~0.99范围之间,属于铕亏损型。大离子亲石元素出现分化,富集Rb、Pb、Th而亏损K、Ba,高场强元素Nb、Ta、Ti等明显亏损。获得钾长花岗岩、二长花岗岩及花岗闪长岩中岩浆结晶锆石的LA-ICP-MS U-Pb年龄分别为：79.4±0.4Ma、 81.0±0.5Ma和81.3±0.5Ma,结合锆石稀土元素和岩浆振荡环带特征及Th/U比值,上述年龄结果可代表岩石的结晶年龄,表明该套岩体为晚白垩世侵位的大型岩基。两件样品的锆石均具有正的Hf同位素初始比值ε_Hf（t）,两阶段Hf模式年龄（t_DM2）分别介于547.5~658.0Ma、523.4~710.2Ma之间。分析认为该套岩体的物质来源应该为富角闪石的下地壳,可能为幔源岩浆首先侵入到地壳基底岩石中形成新生地壳,然后在温度约为700~800℃之间、压力<8kbar且富含流体的影响下,这种既有新生地壳又有古老基底地壳构成的混合地壳发生部分熔融而形成。这一结论与野外宏观露头上岩体中大量发育暗色微粒包体等直接岩石学证据相佐证。结合区域构造演化及岩体所处的大地构造位置,该套花岗岩体应该形成于洋壳闭合时的碰撞造山过程,其形成与侵位与北侧班公湖-怒江结合带的构造演化有成因上的联系,是班公湖-怒江特提斯洋向南的俯冲碰撞的产物。  相似文献   

柴达木盆地西部昆北断阶带基底花岗岩锆石U-Pb年龄、地球化学特征及其地质意义     

刘桂珍  张玉修  薛建勤  吴光大  陈琰 《岩石学报》2014,30(6):1615-1627

柴达木盆地西部基底分布有大量的有花岗岩类岩石。通过对柴达木盆地西部昆北断阶带钻遇的基底花岗岩样品开展详细的岩石学、锆石激光探针等离子体质谱U-Pb同位素年代学及岩石地球化学研究表明,锆石U-Pb同位素年龄为467~450Ma,显示基底花岗岩的结晶年龄为中-晚奥陶世,属于加里东期岩浆侵入旋回。详细的岩石地球化学分析表明,昆北断阶带基底花岗岩属过铝高钾钙碱性系列,其稀土元素配分模式为具有Eu负异常的轻稀土元素富集型,昆北断阶带中南部基底花岗岩属上地壳物质熔融,同碰撞环境下形成的花岗岩。综合区域上的研究成果,昆北断阶带及其以西地区存在中奥陶世-早志留世的加里东期构造-岩浆事件,这对探讨柴达木盆地西部基底花岗岩成因类型及岩浆演化具有重要的意义。  相似文献