江西冷水坑火山-侵入杂岩LA-ICP-MS锆石U-Pb年龄及地质意义

江西冷水坑矿田是武夷山地区重要的银铅锌矿集中区之一,以斑岩型矿床和火山沉积-热液改造型矿床为特色,前人对冷水坑矿床的成岩成矿作用、控矿构造、成矿模式等开展了大量的研究,但对不同地质体与成矿的先后关系、岩浆活动期次与成矿作用的关系研究相对薄弱。本文对打鼓顶组火山岩和含矿花岗斑岩进行了激光剥蚀电感耦合等离子体质谱(LA-ICP-MS)锆石U-Pb年代学研究,结果表明打鼓顶组底板、顶板晶屑凝灰岩形成时代分别为161.3±1.3 Ma、160.75±0.96 Ma,含矿花岗斑岩形成时代为168.09±0.80 Ma,结合以往研究资料,将冷水坑矿田火山-侵入岩岩浆活动划分为3个期次:第Ⅰ期火山-侵入岩浆活动形成于164~170 Ma;第Ⅱ期火山-侵入岩浆活动发生于157~161 Ma,为火山沉积-热液改造型矿床和斑岩型矿体的主要成矿时代,岩浆活动和成矿时代基本一致;第Ⅲ期火山-侵入岩浆活动时限为140~146 Ma。也暗示华南冷水坑等地晚侏罗世火山岩形成于华南中生代构造体制转换的关键时期,为华南晚中生代构造背景的研究提供了重要地质依据。     

黑龙江多宝山铜(钼)矿床叠加成矿:辉钼矿Re-Os年龄和硫化物原位硫同位素证据SCIEI北大核心CSCD

斑岩型矿床易受后期岩浆、构造、变质等地质作用影响,使得矿床自身发生改造变形。后期的热事件不仅可以将原有矿体再活化,还能够带来新的成矿物质,进而发生新一期成矿作用。不同地质时期的成矿作用在同一空间互相叠加,会形成与斑岩矿床矿化特征截然不同的矿床,称为叠加改造型斑岩矿床。多宝山铜(钼)矿床位于中亚造山带东段,兴蒙造山带内。该矿床在成矿构造地质、矿石组构和成矿期次等方面表现出多期改造与叠加成矿的特征。本次根据野外观察和成矿年代学研究,推测多宝山铜矿至少存在两期成矿作用。对采自矿坑340平台10件叠加矿化类型的辉钼矿样品进行Re-Os同位素分析,获得辉钼矿的模式年龄介于435.6±10.5Ma~446.1±7.1Ma之间,等时线年龄为440.1±4.5Ma (MSWD=0.56)。结合前人获得的年龄资料,确认多宝山叠加成矿与晚奥陶世玄武安山岩应形成于统一的成岩成矿地质事件。不同矿化期次的黄铜矿和黄铁矿原位硫同位素结果显示:典型斑岩型矿脉中黄铜矿δ^(34)S平均值为-2.12‰;叠加矿化黄铜矿δ^(34)S平均值为-1.78‰,黄铁矿δ^(34)S平均值为-1.03‰,均落入幔源硫范围,表明硫主要来自岩浆。而前人在叠加期形成的黄铜矿中,测试到较低的δ^(34)S值(-12.9‰~-5.6‰),这是后期流体易携带轻硫^(32)S发生迁移并在应力较低的区域内重新沉淀的结果。同位素组成指示叠加成矿期的矿化元素即来源于新的岩浆活动,又继承了先前存在的岩(矿)体。     

四川省拉拉铜矿田矿床成因模型

四川省会理县拉拉铜矿田处于川滇被动大陆边缘裂谷系的构造环境,成矿作用受会理-东川裂陷槽构造-岩浆演化控制。矿体产于古元古界河口群富钠质的细碧-角斑岩系中。矿石中金属硫化物的δ34S值集中分布在-1‰～4‰之间,均接近0,具塔式分布特征,表明硫主要来自火山喷发作用。矿床与火山喷流沉积型矿床的流体类型相似,其包裹体基本为早期石英硫化物中的Ⅰ型包裹体及后期方解石、石英硫化物中的Ⅱ和Ⅲ型包裹体,Ⅰ型包裹体反映为火山喷发沉积期的主成矿阶段;而Ⅱ型和部分Ⅲ型包裹体反映了晚期流体混溶现象,显示矿床经历了后期改造。根据同位素测年数据,将矿床的成矿过程大致分为火山喷流作用(1600～1800 Ma)、变质变形作用(1000～1100 Ma)和热液叠加改造作用(770～900 Ma) 3个阶段。初步认为拉拉铜矿田矿床成因类型属海相火山岩型铜矿床,但河口群不同的火山喷发旋回具有不同的矿化样式。     

福建紫金山矿田罗卜岭铜钼矿化斑岩锆石LA-ICP- MS U-Pb年龄及成矿岩浆高氧化特征研究

罗卜岭斑岩铜钼矿床是紫金山Cu-Au-Mo浅成低温-斑岩矿田内新近发现的大型斑岩铜钼矿床,本文在岩芯及光薄片系统观察的基础上,分析了矿化斑岩锆石LA-ICP-MS U-Pb年龄及锆石Ce4/Ce3+比值.罗卜岭赋矿斑岩体可分为两期,早期为角闪黑云母花岗闪长斑岩及黑云母花岗闪长斑岩,晚期为黑云母花岗闪长斑岩.早期角闪黑云母花岗闪长斑岩和黑云母花岗闪长斑岩锆石LA-ICP-MS U-Pb年龄分别为103.7±1.2Ma,MSWD=0.33和103.0±0.9Ma,MSWD=1.00;晚期黑云母花岗闪长斑岩锆石LA-ICP-MS U-Pb年龄为97.6±2.1Ma,MSWD=6.00.罗卜岭成矿斑岩基质普遍发育硬石膏,两期成矿斑岩锆石都具较高的Ce4 +/Ce3平均值,在630 ～770之间,高于区内非成矿花岗岩锆石的Ce4+/Ce3+平均值(182 ～577),显示罗卜岭斑岩矿床成矿岩浆具有高氧逸度的特征.据罗卜岭斑岩矿床的形成时代、高氧逸度岩浆特征,结合华南地区中生代构造背景,我们初步认为罗卜岭斑岩矿床的形成可能和中生代古太平洋向北西西方向俯冲有关.     

粤北大宝山多金属矿床LA-ICP-MS锆石U-Pb和辉钼矿Re-Os定年及其地质意义

对粤北大宝山多金属矿床次英安斑岩(样品ZK5803)中锆石LA-ICP-MS U-Pb定年结果为(174.6±1.5)Ma(MSWD=0.7),与矿区花岗闪长斑岩的形成年龄基本一致;3个斑岩型和矽卡岩型钼钨矿石辉钼矿Re-Os模式年龄为(163.2±2.3)Ma(样品CD-30)、(165.2±2.4)Ma(样品DB-18)和(163.4±2.4)Ma(样品CD-38),与层状铜铅锌矿中辉钼矿Re-Os模式年龄(164.7±3.0)Ma基本一致;上述4个样品给出的加权平均年龄为(164.0±2.5)Ma(MSWD=0.16);该成矿年龄与南岭地区其他钼多金属矿床形成时间一致,同属于华南地区中生代第二阶段成矿作用。矿床地质特征、流体包裹体氢氧同位素(δ18O=-3.75‰～7.0‰,δD=-50.7‰～-56.1‰)和矿石硫化物硫同位素(δ34S=-2.00‰～3.00‰)资料表明,该矿床为与矿区次英安斑岩和花岗闪长斑岩有成因联系的岩浆期后热液矿床。矿区各类矿床应为同一期成矿事件的产物,不同于前人认为的存在加里东期海底喷流沉积和燕山期叠加成矿,或燕山期两期成岩成矿的观点。结合岩石微量元素图解和前人研究结果,推测其成矿动力学背景为南岭地区后造山伸展环境。     

新疆鄯善县阿奇山铅锌（铜）矿床地质地球化学与成因探讨

新疆鄯善阿奇山铅锌(铜)矿位于东天山造山带西南缘。为探讨其矿床成因,在分析矿区地质特征的基础上,对矿体、矿石、典型矿物、蚀变分带及矽卡岩等进行了研究。结合成矿阶段划分、物质来源、同位素分析及小东山花岗斑岩锆石U-Pb定年数据,表明成矿与区内同源幔源岩浆作用及早石炭世雅满苏组矿源层关系密切,早石炭世花岗斑岩(331.5±2.0Ma)引起了雅满苏矿源层元素初始活化、局部富集,并提供了部分矿质,后期叠加了与小东山火山机构有关的受近东西向断裂构造控制的火山期后热液-交代充填成矿过程。综合上述信息,认为矿床受断裂构造控制,是与幔源岩浆岩有关的火山沉积-热液叠加改造型铅锌矿床。     

新疆阿尔泰铁木尔特铅锌矿床稳定同位素组成特征

新疆阿尔泰山南缘克兰盆地中的铁木尔特中型铅锌矿床赋存于上志留统—下泥盆统康布铁堡组上亚组第二岩性段,容矿岩石为大理岩、绿泥石英片岩、变钙质粉砂岩、矽卡岩。矿床经历了喷流沉积期、叠加改造期和表生期。喷流沉积期硫化物δ34S值集中于-27.8‰～-16.0‰,峰值为-26.0‰,少量1.7‰～3.4‰,表明硫主要来自细菌还原海水硫酸盐及岩浆活动。氢、氧同位素组成表明,叠加改造期石英和方解石的δD变化于-122‰～-61‰,δ18O变化于9.5‰～10.9‰,δ18O水为-5.8‰～4.8‰,表明叠加改造期成矿流体具有多来源特征,是岩浆水、大气降水和变质水的混合产物。铁木尔特铅锌矿床在成因类型上为VMS型,矿床形成后又经历了叠加改造。     

新疆小热泉子铜矿床成因

新疆小热泉子铜矿床位于古板块缝合带上,在石炭纪为火山喷流沉积环境.矿体具明显的沉积和后期热液改造特征,硫同位素δ(34S)值为-0.11‰～11.10‰,平均为5.73‰,接近大气降水的δ(34S)值.δ(DH2O)为-78.1‰～-77.0‰,明显低于变质水区域值,而接近于岩浆水区域值(-80‰～-40‰),在δ(18O)-δ(D)相关图上,数据点落在近岩浆水区域,表明成矿流体可能为次火山热液与地下水的混合流体.小热泉子铜矿床中黄铁矿的w(Se)高(0.009 5%～0.37%),w(S)/w(Se)值为143～2 137,反映成矿与岩浆热液作用关系密切.矿石中石英的流体包裹体均一温度反映出两阶段热液成矿的特征.矿床硫化物K-Ar同位素年龄显示,矿床的模式年龄有2个年龄段:斑点状闪锌矿与结核状闪锌矿的模式年龄分别为387.2,444.9 Ma,二者组成的等时线年龄为339.1 Ma,与地层年龄早石炭世较接近,可作为火山喷流沉积成矿阶段的起始时间;浸染状黄铜矿的模式年龄为230.2 Ma,可作为热液期中后期的成矿年龄.综合分析矿床成矿特征和地球化学数据认为,该矿床为火山喷流沉积-热液叠加改造型矿床.     

甘肃阳山超大型卡林-类卡林型复合式金矿床特征

阳山金矿于世纪之交勘查并扩大为超大微细浸染型金矿,矿床形成受地层、浅成花岗斑岩、韧-脆性剪切构造及热液活动的多种因素的叠加与改造控制,研究认为矿床具有卡林型和类卡林型两种矿化类型特点,卡林型矿化于韧性剪切早、早—中期阶段和晚期阶段,分别出现含砷黄铁矿-毒砂-次显微金-白云石-石英矿化组合及黄铁矿-辉锑矿-石英方解石矿化组合,及Au-As-Sb-Hg的成矿地球化学组合;类卡林型矿化出现在脆性中—晚期阶段,以黄铁矿-毒砂-自然金-碲铋矿-白云石-石英矿化(含黄铜-闪锌-方铅矿)组合为特征,及Au-As-Cu-Pb-Zn-Te-Bi成矿地球化学组合。阳山复合式金矿含矿地层中沉积成岩黄铁矿δ34S为-24.6‰～-29.0‰,早期—早中期韧-脆性剪切金属硫化物矿化产物δ34S值为5.0‰～7.0‰,中—晚期蚀变花岗斑岩中金属硫化物矿化产物δ34S值为-2.9‰～-2.1‰,显示地层中生物硫、强变形造山带地壳硫、少量岩浆硫混入的多源特征。流体包裹体氢氧同位素与硫同位素近同步特征,成矿热液显示地下流体、强烈改造水和少量岩浆水的混合。     

青海西南三江北段早古新世成岩、成矿事件：陆日格斑岩钼矿LA ICP MS锆石U Pb和辉钼矿Re Os定年

对青海南部西南三江多金属成矿带北段陆日格斑岩钼矿床开展了锆石LA-ICP-MS U-Pb和辉钼矿Re-Os同位素定年研究.研究表明,陆日格黑云母花岗斑岩、细粒花岗斑岩的锆石LA-ICP-MS 206Pb/238U加权平均年龄分别为62.1±0.4Ma、61.7±0.3Ma,所测锆石均显示岩浆成因特点,锆石U-Pb年龄可代表斑岩的结晶年龄;5件辉钼矿的Re-Os加权平均模式年龄为60.7±1.5Ma,锆石U-Pb同位素年龄与辉钼矿的Re-Os年龄非常吻合,所获年龄准确厘定了陆日格矿床的岩浆活动与矿化时限为早古新世.陆日格与三江带中北段主要斑岩型矿床成岩成矿年龄相差近20Ma,表明三江北段自古新世起,区域内至少有两期较大规模的斑岩成矿作用,作为目前已知新生代三江成矿带最早的一次岩浆成矿事件,陆日格斑岩钼矿具有非常重要的理论与找矿工作意义.     

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.     

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.     

Quaternary stresses revealed by calcite twinning inversion: insights from observations in the Savonnières underground quarry (eastern France)

Calcite samples were extracted both from the rock matrix and the superficial coating of a karstified fault plane of an underground quarry, located in the eastern border of the Paris basin. The karstification is dated as Quaternary. Analysis of mechanical calcite twinning reveals that only the calcite matrix has also undergone a compression trending WNW that can be attributed to the Mio-Pliocene alpine collision. Both coating and matrix have undergone a strike-slip regime with σ₁ roughly trending north–south, that could correspond to the regional present-day state of stress, a strike-slip compression rather trending NNW, modified by local phenomena. To cite this article: M. Rocher et al., C. R. Geoscience 335 (2003).     

HYDROGEOLOGY

正20141756 Chen Ruige(Mathematical College,China University of Geosciences,Beijing100083,China);Zhou Xun Numerical Simulation of Groundwater Level Fluctuation in a Coastal Confined Aquifer with Sloping Initial Groundwater Level Induced by the Tide(Geological Bulletin of China,ISSN1671-2552,CN11-4648/P,32(7),2013,p.1099-1104,6 illus.,16 refs.) Key words:confined water,groundwater level     

METAMORPHIC PETROLOGY

正20141408 Cai Jia(Institute of Geology,Chinese Academy of Geological Sciences,Beijing100037,China);Liu Fulai Petrogenesis and Metamorphic P-T Conditions of Garnet-Spinel-Biotitebearing Paragneiss in Danangou Area,Daqingshan-Wulashan Metamorphic Complex Belt(Acta Petrologica Sinica,ISSN1000-0569,CN11-1922/P,29(7),     

SERIALS

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GEOPHYSICAL EXPLORATION

正20142386An Guoying(China Aero Geophysical Survey and Remote Sensing Center for Land and Resources,Beijing 100083,China)Application of Satellite Remote Sensing in Regional Hydrogeological Investigation:Taking Cenozoic Strata in Wenquan Sheet(1∶250 000)of Karakoram Range as an Example(Geosci-     

QUATERNARY GEOLOGY & GEOMORPHOLOGY

正20141016An Chengbang(Key Laboratory of Western China’s Environmental Systems,Ministry of Education,Lanzhou University,Lanzhou 730000,China);Zhao Yongtao Lake Records during the Last Glacial Maximum from Xinjiang,NW China and Their Climatic Impli-     

PETROLEUM GEOLOGY

正20141538 Cao Qing(School of Earth Sciences and Engineering,Xi’an Petroleum University,Xi’an 710065,China);Zhao Jingzhou Characteristics and Significance of Fluid Inclusions from Majiagou Formation,Yichuan Huangling Area,Ordos Basin(Advances in Earth Science,ISSN1001-8166,CN62-1091/P,28(7),2013,p.819-828,7 illus.,3 tables,43 refs.)     

GEOCHEMISTRY

正20142002 Wei Hualing(Institute of Geophysical and Geochemical Exploration,Chinese Academy of Geological Sciences,Langfang065000,China);Zhou Guohua Element Content and Mineral Compositions in Different Sizes of Soil in Tongling Area,Anhui Province(Geological Bulletin of China,ISSN1671-2552,CN11-4648/P,32(11),2013,p.1861