辽东青城子矿集区金、银成矿时代及地质意义

为确定辽宁青城子矿集区金、银的成矿时代 ,分别以含金硅化岩和含银网脉状石英晶体内流体包裹体为对象 ,应用Rb_Sr法测得金、银成矿的等时线年龄为 (2 33± 31)Ma～ (2 34± 14 )Ma ;作为对Rb_Sr法测年结果的验证 ,又以与贵金属矿石矿物共生的热液石英为对象 ,用40 Ar/3 9Ar快中子活化法测得坪年龄tp=(2 38.78± 0 .74 )Ma～ (2 38.80± 0 .6 0 )Ma,等时线年龄ti=(2 39.4 6± 1.13)Ma～ (2 4 0 .35± 0 .88)Ma。Rb_Sr和40 Ar/3 9Ar两种方法的测年结果基本一致 ,与本区印支期岩浆活动时代〔2 17.6Ma～ (2 30 .7± 5 )Ma〕吻合。     

新疆萨吾尔金矿带40Ar-39Ar年龄及其意义

利用石英 4 0 Ar-39Ar同位素年代学方法对萨吾尔金矿带中两个重要的金矿床进行了成矿年龄测定。阔尔真阔腊金矿床主成矿年龄为3 3 2 .0 5± 2 .0 2 Ma～ 3 3 2 .5 9± 0 .5 1Ma,布尔克斯岱金矿床主成矿年龄为 3 3 5 .5 3± 0 .3 2 Ma～ 3 3 6.78± 0 .5 0 Ma,二者的成矿时代一致 ,且与金矿带内钙碱性火山岩年龄 (3 43± 2 2 Ma)相近 ,这为解决长期存在的萨吾尔金矿带中两个主要金矿床成矿时代及矿床成因问题提供了有力的证据 ,同时还确定了海西期阿尔泰地区除已知的两期成矿作用 (早泥盆世和晚石炭世—二叠纪两期构造 -岩浆成矿作用 )外 …     

华北地台北缘中段金矿床成矿年代学研究

华北地台北缘中段是我国重要的金矿化集中区。文中采用石英的4 0 Ar - 39Ar法和单颗粒锆石的U -Pb测年法 ,结合前人资料 ,提出本区绿岩带初生型金矿床的成矿时代为古元古代—新太古代 ,其中辽西排山楼金矿的成矿时代为 (2 10 5 .2± 10 .4)Ma ,金厂峪金矿的成矿时代为 (2 5 39± 2 3)Ma ,小营盘金矿的成矿时代为180 0Ma左右。构造期后再生型金矿床的成矿时代为燕山晚期—华力西中期 ,其中东坪金矿床的成矿时代为(35 0 .9± 0 .9)Ma ,冀东头道门子沟金矿的成矿时代为 (2 17.32± 2 .0 4)Ma ,峪耳崖金矿床的成矿时代为燕山早期 ,金厂沟梁和二道沟金矿的成矿时代为燕山晚期。     

华北地块南缘中段中生代花岗质岩石的40Ar-39Ar年代学研究

对华北地块南缘4个中生代花岗质岩体中的角闪石和黑云母进行了40Ar-39Ar定年研究。结果表明,陕西黑山村岩体黑云母花岗闪长岩中黑云母的40Ar-39Ar坪年龄为126. 6±0. 3Ma,河南马家湾岩体细粒黑云母花岗闪长岩中黑云母的40Ar-39Ar坪年龄为126. 6±0. 2Ma,河南洛宁南八百坡岩体黑云母二长花岗岩中角闪石的40Ar-39Ar坪年龄为128. 3±0. 3Ma,山西蚕坊岩体花岗闪长岩中角闪石的40Ar-39Ar坪年龄为129. 2±0. 2Ma。上述结果显示华北地块南缘中生代的岩浆活动主要发生在早白垩世。该期岩浆的产生应与中国东部早白垩世的伸展环境相联系。     

熊耳裂陷印支期同位素地质年龄耦合性

在熊耳裂陷构造环境背景和演化的基础上 ,应用U Pb稀释法精确确定岩浆活动年龄 (印支期 2 0 8.5±6 .2Ma ,燕山期 12 1.6± 3.9Ma) ;熊耳群上部安山岩40 Ar 3 9Ar法坪年龄 2 0 6 .5 5Ma ,等时线年龄 2 0 7.5 2± 2 .5 6Ma ,指示热扰动年龄 ;北岭金矿、陈胡子沟金矿蚀变矿物Sm Nd法内部等时线年龄 186± 2Ma。这些年龄大于燕山期 ,而与印支期相近 ,显示了印支期岩浆活动、热构造事件和有关成矿作用的耦合性。     

论河北丰宁牛圈银(金)矿床的成矿时限问题

对河北牛圈银(金)矿区细粒钾长花岗岩株和含矿隐爆角砾岩墙钾长石样品进行了详细的40Ar/39Ar同位素年龄测定。细粒钾长花岗岩株钾长石样品主要加热阶段所获得数据构成一条相关性很好的直线,其对应的同位素等时线年龄值为(216.6±3.2)Ma(2σ),40Ar/39Ar初始比值为297±28。相比之下,含矿隐爆角砾岩墙钾长石样品特定加热阶段(1200～1300℃和1360～1450℃)所获数据同样也构成两条直线,其对应的同位素等到时线年龄值分别为(227.9±4.8)Ma(2σ)和(216.7±6.1)Ma(2σ),40Ar/39Ar初始比值分别为307±41和269±39。考虑到所测样品均采自未受到明显后期构造-岩浆活动或其他热事件影响的岩(矿)体,因此,细粒钾长花岗岩株和含矿隐爆角砾岩墙的形成时代为216Ma,与印支期富钾岩浆作用具有密切成因联系。根据含矿隐爆角砾岩墙的野外地质证据,结合矿物共生组合关系和钾长石同位素年龄数值,可以推测牛圈银(金)矿区早期成矿作用发生在(227.9±4.8)Ma,而主要成矿期为(216.7±6.1)Ma,是印支期多阶段富碱质成矿流体活动的产物。牛圈银(金)矿区成矿作用时间的厘定对于提高该区成矿理论研究水平和寻找隐伏金属矿床均具重要意义。     

西秦岭南亚带层控金-硒矿床的赋矿地层年代与成矿时代

西秦岭南亚带层控金硒矿床的赋矿地层为太阳顶群 ,为一套主要由炭质硅岩和炭质板岩组成的硅岩建造。对于太阳顶群的时代 ,至今仍众说纷纭 ,莫衷一是 ,大多数人认为属晚寒武世—奥陶纪 ,也有认为属晚震旦—早寒武世。作者通过对古杯类化石的鉴定以及Rb Sr、Sm Nd同位素等时线年龄测定后认为 ,赋矿的太阳顶群时代应属早寒武世 ,而非晚寒武世—奥陶纪 ,更不可能为晚震旦世。对金硒矿床中 2个成矿阶段石英样品进行40 Ar/ 3 9Ar快中子活化测定后获得马鞍型谱线特征。其中坪年龄 (71 .4 5± 0 .5 5 )～ (80 .0 5± 0 .6 5 )Ma、最小视年龄 (70 .2 4± 1 .93)～ (78.5 9± 2 .85 )Ma和等时线年龄 (6 9.4 5± 0 .38)～ (81 .6 1± 0 .5 5 )Ma均十分接近 ,说明所测 2件石英样品的40 Ar/ 3 9Ar年龄真实可靠 ,表明太阳顶群中层控金硒矿床的成矿时间主要发生于燕山运动晚期     

辽西义县组火山岩40Ar/39Ar、K-Ar法年龄测定

义县组为辽西地区广泛分布的陆相火山-沉积地层,义县火山旋回分为 4个亚旋回.含珍稀化石的湖相沉积层与第二亚旋回火山岩伴生.运用激光微区 40Ar/39Ar法、常规 40Ar/39Ar阶段升温测年法和 K- Ar法,对义县旋回火山岩进行了系统的年龄测定,结果表明,直接覆盖义县组底砾岩的义县旋回第一亚旋回第一小旋回玄武岩的 K- Ar年龄为 (133.3± 2.6) Ma、 (133.6± 2.6) Ma,激光微区 40Ar/39Ar法给出的相关性很好的 Ar- Ar等时线年龄为 (132.9± 4.5) Ma,第三、第四小旋回玄武岩样品 40Ar/39Ar阶段升温获得平坦的年龄谱线,坪年龄分别为 (130.6± 0.5) Ma、 (127.7± 0.2) Ma;第二亚旋回玄武岩和流纹质凝灰岩样品 Ar- Ar等时线年龄为 (126.1± 1.7) Ma、 (127.4± 1.3) Ma,第三亚旋回火山岩全岩 K- Ar年龄为 (124.4± 2.4)～ (124.9± 2.4) Ma.义县火山旋回发生的时间大致介于 120～ 135 Ma之间, 义县组的时代应为早白垩世.     

河南洛宁太华岩群斜长角闪岩的锆石^207Pb／^206Pb和角闪石^40Ar／^39Ar年龄

运用单颗粒锆石逐层蒸发法和角闪石40Ar/39Ar阶段加热法研究了河南洛宁太华岩群斜长角闪岩的同位素年龄.获得锆石207Pb/206Pb年龄为2675±2 Ma,角闪石40Ar/39Ar坪年龄和等时线年龄分别为2372.98±47.46 Ma和2349.10±46.98 Ma.锆石207Pb/206Pb年龄代表了斜长角闪岩原岩的形成时代,而角闪石40Ar/39Ar年龄则为其变质时代,与Sm-Nd等时线年龄(2351±103Ma)相一致.上述年龄数据表明河南洛宁地区太华岩群形成于新太古代,在古元古代遭受过一次角闪岩相变质作用.     

华北地台北缘中段金矿床成矿年代学研究

华北地台北缘中段是我国重要的金矿化集中区.文中采用石英的(40)Ar-(39)Ar法和单颗粒锆石的U-Pb测年法,结合前人资料,提出本区绿岩带初生型金矿床的成矿时代为古元古代—新太古代,其中辽西排山楼金矿的成矿时代为(2 105.2±10.4)Ma,金厂峪金矿的成矿时代为(2 539±23)Ma,小营盘金矿的成矿时代为1 800Ma左右.构造期后再生型金矿床的成矿时代为燕山晚期—华力西中期,其中东坪金矿床的成矿时代为(350.9±0.9)Ma,冀东头道门子沟金矿的成矿时代为(217.32±2.04)Ma,峪耳崖金矿床的成矿时代为燕山早期,金厂沟梁和二道沟金矿的成矿时代为燕山晚期.     

The terrestrial fauna of the Late Triassic Pant-y-ffynnon Quarry fissures,South Wales,UK and a new species of Clevosaurus (Lepidosauria: Rhynchocephalia)

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.     

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.     

The effect of water on accessory phase solubility in subaluminous and peralkaline granitic melts

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.     

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