磷灰石微区原位LA-MC-ICP-MS U-Pb同位素定年

利用激光剥蚀多接收器电感耦合等离子体质谱法(LA-MC-ICP-MS), 建立了磷灰石微区原位U-Pb同位素定年新方法, 本文给出了这一新方法的分析流程, 报道了利用这一新方法对5个磷灰石样品的分析结果, 并应用同位素稀释-热电离质谱法(ID-TIMS)对一些样品定年结果进行了验证。磷灰石工作标样SDG的U-Pb同位素年龄: (1596±15) Ma (MSWD=1.5, n=7, LA-MC-ICP-MS), (1602±13) Ma (MSWD=0.578, n=5, ID-TIMS); 某铁矿石中磷灰石的LA-MC-ICP-MS U-Pb同位素年龄: (125±14) Ma (MSWD=0.68, n=25), (124.2±3.5) Ma (MSWD=1.5, n=37); 新疆阿尔金地区片麻岩中磷灰石的LA-MC-ICP-MS U-Pb同位素年龄: (250.8±3.9) Ma (MSWD=8.6, n=26), (245.4±2.9) Ma (MSWD=2.1, n=39)。     

氟碳铈矿U-Pb定年技术研究

本文以稀土矿床中的常见副矿物氟碳铈矿为研究对象,通过优化实验条件和仪器参数,分别采用激光剥蚀多接收电感耦合等离子体质谱法(LA-MC-ICP-MS)和同位素稀释热电离质谱法(ID-TIMS)对氟碳铈矿样品SAM进行U-Pb定年技术研究,并将此两种方法得到的结果进行对比。LA-MC-ICP-MS得到的U-Pb年龄为(409±18)Ma(N=27,MSWD=4.5),ID-TIMS得到的206Pb/238U U-Pb年龄为(407.8±3.3)Ma(N=3,MSWD=0.029),两种方法得到的U-Pb年龄结果在误差范围内一致。通过比较两种方法的实验流程和结果,总结了各自的优缺点,为氟碳铈矿U-Pb定年方法选择提供了参考依据。     

内蒙古赵井沟铌钽矿床燕山期成矿:来自LA-MC-ICP-MS独居石、锆石U-Pb和黑云母40Ar-39Ar年龄的证据

内蒙古武川县赵井沟铌钽矿是新近取得勘查突破的一例大型铌钽矿床.矿体赋存岩石为含天河石钠长花岗岩,其次为花岗细晶岩、云英岩及天河石花岗伟晶岩.运用LA-MC-ICP-MS法对矿区钠长花岗（细晶）岩脉、正长花岗岩中的独居石、锆石进行了U-Pb同位素年龄测定,同时对石英-黑云母脉中的黑云母进行了40Ar-39Ar定年.4件独居石的LA-MC-ICP-MS U-Pb年龄分别为124±2 Ma（MSWD=2.9,n=27）、124±3 Ma（MSWD=2.0,n=46）、121±1 Ma（MSWD=3.3,n=43）和124±2 Ma（MSWD=3.2,n=12）,1件锆石的LA-MC-ICP-MS U-Pb年龄为125±1 Ma（MSWD=1.6,n=18）;黑云母40Ar-39Ar坪年龄为133.84±0.79 Ma（MSWD=3.31）,40Ar/36Ar-39Ar/36Ar等时线年龄为134.55±0.79 Ma（MSWD=1.93）,反等时线年龄为134.58±0.80 Ma（MSWD=1.99）,这些年龄限定赵井沟铌钽矿形成于早白垩世.综合分析表明,燕山期是内蒙古地区重要的铌钽成矿期,赵井沟铌钽矿是燕山期伸展体制下构造岩浆活动的产物.      

榍石LA-ICP-MS U-Pb定年技术研究

榍石具有较高的U含量和封闭温度,是一种重要的适用于U-Pb定年的副矿物。然而,基体效应与普通Pb校正成为制约榍石LA-ICP-MS U-Pb定年发展的主要因素。本文以~(206)Pb/~(238)U为例,采用基体归一化因子(F_(AVG))评估了锆石与榍石U-Pb定年标准的基体效应,结果显示榍石F_(AVG)几乎都大于1.20,而锆石F_(AVG)明显都小于1.20,表明锆石与榍石U-Pb定年标准存在显著的基体效应。以BLR-1榍石标准为外部校准标样,OLT1榍石获得的谐和年龄1014.9±4.8Ma(95%置信水平,n=23,MSWD=0.32)与SHRIMP谐和年龄1017.1±3.6Ma及ID-TIMS谐和年龄1014.6±1.3 Ma在误差范围内一致,同时获得~(206)Pb/~(238)U、~(207) Pb/~(235) U、~(207) Pb/~(206) Pb加权平均年龄在误差范围内与其谐和年龄一致;而以91500锆石为外部校准标样,OLT1榍石获得的~(206)Pb/~(238)U加权平均年龄为891.3±9.5 Ma(n=23,MSWD=5.3),与ID-TIMS测得的谐和年龄相比偏低约12%。经~(207)Pb法校正后,TCB榍石获得的~(206)Pb/~(238) U加权平均年龄1015.6±6.2 Ma(n=16,MSWD=0.84)与ID-TIMS谐和年龄1018.1±1.7Ma在误差范围内一致。本研究表明,采用基体匹配的榍石标准为外部标样,利用LA-ICP-MS对榍石进行U-Pb定年也能获得与ID-TIMS相一致的年龄,精度(2RSE)小于2%。     

冈底斯中段岗讲斑岩铜钼矿床锆石U-Pb和辉钼矿Re-Os年代学及其地质意义

岗讲铜钼矿床是西藏冈底斯成矿带中段典型的斑岩型矿床,岗讲矿床成岩成矿时代、岩浆演化过程及其与成岩成矿关系尚不明确,利用LA-ICP-MS锆石U-Pb定年方法对岗讲矿区主要岩体二长花岗斑岩、花岗闪长斑岩和英云闪长玢岩成岩时代进行研究,获得锆石U-Pb年龄加权平均值分别为16.6±0.3 Ma (MSWD=0.94,n=10)、16.1±0.2 Ma (MSWD=1.07,n=12)、14.4±0.4 Ma (MSWD=1.12,n=7);同时采用辉钼矿Re-Os同位素测年方法首次对岗讲矿床石英硫化物脉中的辉钼矿进行定年,获得12件辉钼矿Re-Os同位素模式年龄集中于13.24±0.20 Ma~13.55±0.22 Ma,加权平均年龄为13.4±0.1 Ma (MSWD=0.65),等时线年龄为13.6±1.6 Ma (MSWD=1.2).结果表明:(1) 岗讲矿区复式岩体侵入序列为含巨斑黑云二长花岗岩-二长花岗斑岩-花岗闪长斑岩-流纹斑岩 (深部定名为英云闪长玢岩),成岩时限为16.6~14.4 Ma,成矿时代为13.4 Ma左右,成岩成矿是一个连续的岩浆演化过程;(2) 辉钼矿中Re含量为155.4~171.1 μg/g,均值为162.9 μg/g,指示其成矿物质中有幔源成分的加入;(3) 矿床产出于中新世印度-亚洲大陆碰撞后伸展构造环境.      

新太古代花岗片麻岩中麻粒岩包体磷灰石U-Pb定年对燕辽裂陷槽中元古代长城群底界年龄的制约

近年来,燕辽裂陷槽中-新元古界年代学研究进展突出,最重要的进展之一是长城群底界年龄的确定,目前基本可以比较准确地将其定为1 650 Ma。本文报道了支持此认识的新证据——下伏于长城群常州沟组之下的新太古代片麻岩中的麻粒岩包体的磷灰石U-Pb年龄。通过高精度ID-TIMS定年方法,对天津蓟县下营镇常州村附近长城群常州沟组不整合覆盖的新太古代遵化杂岩中的麻粒岩中磷灰石进行了U-Pb定年,获得了制约"长城群"底界的年龄:~(207)Pb/~(206)Pb表面年龄加权平均值为1 666±16 Ma(MSWD=1.8,n=11),不一致线上交点年龄1 667±23 Ma(MSWD=1.7,n=11),二者在误差范围内完全一致。该测年成果再一次有力制约了燕辽裂陷槽长城群的底界年龄为1 650 Ma。     

江西九瑞地区宝山斑岩型铜多金属矿床锆石U-Pb和辉钼矿Re-Os年龄及其地质意义

宝山斑岩型铜多金属矿床位于九瑞矿集区西北部,隶属于九江-瑞昌铜金矿田,为长江中下游铜金成矿带、大冶-九江成矿亚带的组成部分。对宝山岩体的花岗闪长斑岩进行LA-MC-ICP-MS U-Pb同位素测年,获得其锆石U-Pb年龄为(147.81±0.48)Ma(MSWD=1.07);首次对宝山矿床的辉钼矿进行Re-Os同位素定年,获得矿床的成矿年龄:6件辉钼矿的Re-Os同位素模式年龄范围为(146.1±2.2)Ma~(148.7±2.0)Ma,加权平均年龄为(147.42±0.84)Ma,等时线年龄为(147.7±1.2)Ma。成岩年龄与成矿年龄在误差范围内一致。辉钼矿的Re含量指示宝山矿床的成矿物质来自于壳幔混源。宝山矿区的成岩、成矿时代与九瑞矿集区典型岩体和矿床的成岩、成矿时代相似,也与长江中下游地区铜陵、安庆和鄂东南(部分地区)的典型铜多金属矿床的成岩、成矿时代基本一致,都属于长江中下游成矿带早白垩世多金属成矿事件的一部分。     

粤北石角围花岗岩型铀矿床沥青铀矿LA-ICP-MS原位U-Pb定年研究

石角围花岗岩型铀矿床位于粤北下庄铀矿田东部,沥青铀矿是矿床的主要矿石矿物,也是厘定成矿年龄的理想对象。前人采用同位素稀释法(ID-TIMS)和电子探针U-Th-totalPb化学定年法获得的成矿年龄为38～138Ma,但前人年龄变化范围大,可靠性有待考究,难以有效约束矿床的成矿时代。本文利用LA-ICP-MS原位微区分析技术,对石角围矿床矿石中沥青铀矿开展了原位U-Pb定年。研究表明:沥青铀矿的206Pb/238U年龄为52. 46～56. 89Ma,加权平均年龄为54. 68±0. 53Ma(MSWD=1. 19,n=18)。本次沥青铀矿原位U-Pb定年与前人相比更好地避免了矿物包裹体、后期次生变化、显微裂隙等因素的影响,获得的沥青铀矿原位U-Pb同位素年龄代表矿床的成矿年龄。本研究获得的石角围矿床成矿年龄(～55Ma)与华南花岗岩型铀矿床主成矿期(～50Ma)相一致,指示石角围矿床铀成矿作用与华南岩石圈局部伸展作用下的断裂构造活动密切相关。     

河北省涞源县龙门斑岩型钼矿床锆石U-Pb和辉钼矿Re-Os年龄及其地质意义

龙门钼矿床是太行山北段成矿带内近些年探明的一个大型钼矿床,钼矿体主要产于花岗斑岩、闪长岩和新太古代片麻岩中,以角砾岩型矿石为主.矿区内辉钼矿化主要类型为浸染状、薄膜状、细脉状,发育钾长石化、硅化、绢云母化、黄铁矿化蚀变,类似典型的斑岩型矿床的矿化和蚀变特征.文章对龙门钼矿床的闪长岩和花岗斑岩进行了LA-ICP-MS锆石U-Pb同位素测年,获得闪长岩的锆石谐和年龄为(138.1±0.6)Ma(MSWD=0.6,n=21),花岗斑岩的锆石谐和年龄为(137.0±0.7)Ma(MSWD=1.03,n=17),结合地质特征,显示花岗斑岩晚于闪长岩形成.对主要矿石类型中的辉钼矿进行了Re-Os同位素测年,获得辉钼矿的Re-Os等时线年龄为(136.5±1.5)Ma,与赋矿的花岗斑岩的侵位年龄相一致,二者应为同一岩浆-流体活动的产物.龙门钼矿床辉钼矿样品的w(Re)为13.1×10-6～59.3×10-6,表明其成矿物质来源于壳幔混源.龙门矿区及太行山北段成矿带内的隐爆角砾岩体是下一步找矿勘查的方向.     

内蒙古东部得耳布尔铅锌矿床安山岩的形成环境和岩浆热液演化史:锆石U-Pb定年

得耳布尔铅锌矿床是一座与火山作用有关的中型以上热液脉型多金属矿床,产于大兴安岭西坡中段得尔布干成矿带北段。笔者对矿区内发育的赋矿围岩安山岩开展了单颗粒锆石U-Pb测年,实验结果揭示:安山岩的岩浆期为144~139 Ma(加权平均年龄为141.6±1.8 Ma,MSWD=0.69,n=6)、岩浆热液期为136~132 Ma(加权平均年龄为134.7±5.7 Ma,MSWD=1.3,n=3)及热液期为129~128 Ma(加权平均年龄为128.4±2.5 Ma,MSWD=0.074,n=3),火山岩浆-热液作用经历了至少13 Ma;成岩作用发生在中国东部早白垩世岩石圈减薄期。     

Définition d'une limite multicritère ; stratigraphie du passage Campanien–Maastrichtien du site géologique de Tercis (Landes,SW France)Definition of a multi-criteria boundary; stratigraphy of the Campanian–Maastrichtian interval of the geological site at Tercis (Landes,SW France)

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.     

Late Wuchiapingian (Late Dzhulfian,early Late Permian) limestone olistolites within the Tertiary flysch of Glypia Unit (Mount Parnon,central–eastern Peloponnesus,Greece)

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.     

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.)     

GEOCHEMICAL EXPLORATION

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.)     

MICROPALAEONTOLOGY

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.)     

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.,     

ENVIRONMENTAL GEOLOGY

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     

PROSPECTING EXPLORATION

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     

OCEANOGRAPHY & MARINE GEOLOGY

正20140582 Fang Xisheng(Key Lab.of Marine Sedimentology and Environmental Geology,First Institute of Oceanography,State Oceanic Administration,Qingdao 266061,China);Shi Xuefa Mineralogy of Surface Sediment in the Eastern Area off the Ryukyu Islands and Its Geological Significance(Marine Geology Quaternary Geology,ISSN0256-1492,CN37     

ENVIRONMENTAL GEOLOGY

正20141810 Bian Yumei(Geological Environmental Monitoring Center of Liaoning Province,Shenyang 110032,China);Zhang Jing Zoning Haicheng,Liaoning Province,by GeoHazard Risk and Geo-Hazard Assessment(Journal of Geological Hazards and Environment Preservation,ISSN1006-4362,CN51-1467/P,24(3),2013,p.5-9,2 illus.,tables,refs.)