羌塘盆地侏罗系元素地球化学特征与成盐层位分析

近年来在羌塘盆地侏罗系发现的大面积石膏层位和高盐度的盐泉水,显示羌塘盆地侏罗纪可能具备成盐地质条件。本文通过对羌塘盆地雁石坪地区侏罗系元素地球化学分析,揭示了羌塘盆地侏罗纪特提斯洋海平面与古气候变化以及蒸发岩沉积条件。全岩Fe/Mn比值和CaCO3含量揭示布曲组和索瓦组沉积时期,由于特提斯洋海水入侵,盆地沉积大量海相碳酸盐岩,盆地海平面处于高位时期;雀莫错组和夏里组沉积时期处于海退后的海平面低值期。酸不溶态元素比值K2O/Al2O3、Na2O/Al2O3以及Na2O/K2O和化学蚀变指数(CIA)揭示雁石坪地区布曲组和夏里组沉积时期气候相对干旱,而雀莫错组和索瓦组沉积时期相对湿润。可溶态K+、Na+含量仅在夏里组出现高值,指示了该沉积时期有利于成盐。综合物源、古构造、古气候和古地理条件,本文认为羌塘盆地侏罗系夏里组是最具成盐潜力的层位,今后成盐研究重点应该放在盆地中-西部地区侏罗系夏里组。     

羌塘盆地中晚侏罗世雁石坪剖面夏里组古盐度与成盐意义

羌塘盆地是一个具有成盐远景的蒸发岩盆地,对羌塘盆地侏罗系雁石坪群夏里组出露的石膏层和具有钾、钠异常的盐泉水研究表明,夏里组是羌塘盆地潜在的形成钠盐、钾盐的目标层位之一。本文通过对羌塘盆地雁石坪剖面夏里组硼元素、锶元素和钡元素的测量,计算Adams古盐度和Sr/Ba比值,来恢复雁石坪剖面夏里组的古盐度。根据Sr/Ba比值、Adams古盐度和Walker相当硼含量的变化趋势,雁石坪剖面夏里组古盐度可以划分为以下3个阶段:夏里组下段(0~260 m、164~162.3 Ma)淡水环境、中段(260~500 m、162.3~160.7 Ma)咸水环境和上段(500~608 m、160.7~160.2 Ma)超咸水环境。另外,通过分析物源、气候以及古地理条件,认为夏里组具备适宜成盐的物源、气候和古地理条件,根据夏里组上段Ca^2+-SO4^2-离子、Na^+-Cl^-离子和K^+-Cl^-离子的相关性分析表明,夏里组上段古环境已经演化到沉积硫酸盐阶段或者沉积氯化物早期阶段,即夏里组上段形成石盐的环境要优于形成钾盐的环境。     

羌塘盆地侏罗系夏里组沉积相

<正> 青藏地区羌塘盆地地层出露以海相三叠系—侏罗系为主。盆地内侏罗系沉积巨厚,夏里组属中侏罗统。在夏里组沉积初期,羌塘盆地由北向南发生大规模海退,由此形成了北羌塘盆地以碎屑岩充填为主,南羌塘盆地以碳酸盐岩沉积为主的特点。根据41条露头剖面及分析化验资料,夏里组     

羌塘盆地多格错仁地区盐泉地球化学特征及成钾预测

多层次、大面积发育的石膏和前人的古地理资料表明,羌塘盆地侏罗纪海相地层具有较好的成盐地质条件。在多格错仁周缘地区侏罗系发育有一系列氯化钙型的盐泉。通过野外地质工作,采集了30个盐泉的水样,并在室内对其地球化学组成和氢氧同位素组成进行了测定。地球化学分析表明,盐泉中富集Na⁺、Cl^-、Ca²⁺、K⁺、Li和Rb,Br和B含量相对贫乏,而地球化学特征系数显示了明显的找钾异常。盐泉水的氢氧同位素特征表明盐泉的供给水源为大气降水,大气降水进入研究区岩层后成为地下水,溶滤了地层中的盐类矿物,从而形成了溶滤卤水,这与地球化学特征系数的判别结果是一致的。综合看来,多格错仁南岸找钾远景显示最好,该点盐泉具有盐度高、K⁺含量高的特征,而且很可能溶滤了钾盐-石盐岩、钾盐层,万安湖西北、源泉河、东温泉盐泉找钾远景次之,主要表现为盐度相对较低,但是含钾显示也异常明显。     

羌塘盆地热觉茶卡-藏夏河地区泉水水化学特征及其地质意义

泉水的水化学特征可以反映氧化-还原环境和水动力条件,近年来被广泛地用于石油、天然气以及天然气水合物的找矿工作中。本文对羌塘盆地热觉茶卡—藏夏河地区37处泉水和13件地表水进行了水化学特征、水溶性烃类气体特征和水中氢氧同位素特征分析,结果表明,羌塘盆地热觉茶卡—藏夏河地区的水型主要为Na₂SO₄型和MgCl₂型,其次为NaHCO₃型和CaCl₂型。矿化度普遍较高,说明该区具有较好的保存条件。铵根离子的平均含量为0.895 g/g,在藏夏河地区高达7.381 g/g,表明在藏夏河东部地区有机质相对较为丰富,这与区域上发育的富有机质页岩结果一致。氢氧同位素结果显示,该区水体的氢氧同位素落在了大气降水线附近,表明水体的来源主要受大气降水的补给。另外,采集的9个泉水样品中均检测出一定含量的水溶甲烷,在白云湖地区的甲烷含量相对较高,显示出较好的油气潜力。综合研究表明,藏夏河东和白云湖地区具有良好的油气烃源岩条件,保存条件较好,显示出良好的油气和天然气水合物资源前景。     

藏北羌塘盆地侏罗纪大孢子的发现

羌塘盆地位于青藏高原的北部 ,为高寒缺氧的无人区。该盆地呈东西走向 ,地表以侏罗系大面积分布为特征 ,大致呈东西向展布 ,地层出露全 ,厚度大 ,岩性岩相复杂。 1994— 1997年期间 ,我们实测了 17条羌塘盆地侏罗系剖面 ,获得了丰富的岩性、岩相和古生物资料 ,将青海省侏罗系岩石地层划分方案应用到西藏羌塘盆地 ,并根据具体情况进行适当的修改 ,使羌塘盆地侏罗系划分更趋于完善。将羌塘盆地侏罗系划分为下侏罗统那底岗日组 ,中侏罗统雀莫错组、布曲组、夏里组 ,上侏罗统索瓦组和雪山组。本次在独雪山的布曲组、拉雄错的夏里组和白龙冰河的…     

羌塘盆地晚侏罗世夏里组磁学参数指示的沉积环境及其成盐意义

羌塘盆地位于青藏高原中部,是一个具有沉积钠盐、钾盐远景的蒸发岩盆地。最近在羌塘盆地上侏罗统夏里组中发现多处具有钾、钠异常的盐泉这一重要的找钾盐线索,然而目前对上侏罗统夏里组的古环境演变仍然不甚了解,限制了对晚侏罗世羌塘盆地的成盐(成钾)条件和可能的层位等重大科学问题的理解。因此本文以热磁分析为主,对羌塘盆地雁石坪地区上侏罗统夏里组沉积物进行高分辨率岩石磁学研究,并讨论其古环境意义。最后,根据成盐(成钾)理论,综合分析羌塘盆地上侏罗统夏里组成盐(成钾)的构造、气候和物源条件。κ-T曲线、磁滞回线和热退磁结果共同表明磁铁矿和赤铁矿是夏里组的主要载磁矿物;磁学参数分析表明夏里组上段赤铁矿含量相对增加,揭示夏里组上段形成于干旱气候环境;综合分析构造、气候和物源条件表明,羌塘盆地上侏罗统夏里组上段最为具备良好的成盐(成钾)条件。     

西藏南羌塘盆地侏罗系烃源岩地球化学特征

依据剖面露头样品的实验测试资料,通过Rock-Eval岩石评价、显微镜下观察、镜质体反射率、烃源岩可溶有机质特征、单体烃碳同位素等分析方法,对南羌塘盆地侏罗系烃源岩地球化学特征进行综合研究。研究结果表明:南羌塘盆地侏罗系烃源岩有机质丰度较低,总体上夏里组泥质烃源岩要好于布曲组和索瓦组碳酸盐岩烃源岩;烃源岩的有机质类型较好,主要为Ⅱ1型,并且反映出烃源岩形成于具一定盐度的较强还原环境,其有机质以海相低等水生生物为主;烃源岩的热演化程度总体较高,达到高成熟阶段。正构烷烃单体烃碳同位素分析表明,侏罗系各组烃源岩之间在母质输入上可能存在较大差异,该地区白云岩油苗与夏里组泥质烃源岩有很强亲缘关系。     

胶东金矿床碳酸盐矿物的碳-氧和锶-钕同位素地球化学研究

对胶东四类金矿床(盆地边缘砾岩型、斑岩型-浅成热液型、石英脉型和破碎带蚀变岩型)矿石中的碳酸盐矿物开展了系统的碳-氧同位素和锶-钕同位素地球化学研究。研究结果表明，与宏观的成矿地质条件和矿床地质特征相对应，山东金矿床可能有亲岩浆岩和亲沉积盆地两个不同的成矿系统。前者包括斑岩型-浅成热液型、石英脉型和破碎带蚀变岩型三类金矿床，后者指盆地边缘砾岩型金矿床，二者具有不同的碳-氧和锶-钕同位素地球化学特征。山东亲岩浆岩系列的金矿床，其锶-钕同位素与同时代的幔源岩浆岩一致，碳同位素显示幔源碳和岩浆碳的特征，氧同位素则显示初生水与大气降水不同比例混合的可能性，因此有可能是以CO2为主、富合成矿金属的地幔流体与浅部下渗大气降水相互作用的结果。而与岩浆岩关系不密切、主要受盆地边缘断裂控制的盆地边缘砾岩型金矿床，其碳-氧和锶-钕同位素组成均较分散，可能主要与地壳浅部下渗大气降水对上地壳各种岩石淋滤萃取演化而成的成矿流体有关。     

西藏北羌塘盆地多格错仁地区盐泉水化学特征及其物质来源

西藏北羌塘盆地是我国侏罗系海相找钾的主要远景区之一,在多格错仁地区发育有一系列具有明显的含钾异常的现代盐泉,研究这些盐泉水的物质来源具有重要的找钾意义和科学价值。野外采集了40个盐泉水的样品,并在室内测定了其化学组分、δ34 S和87 Sr/86 Sr。分析结果显示,盐泉水具有富Na+、Ca2+、K+、Cl-,贫Mg2+、SO2-4、HCO-3的特征,其Cl-含量约占矿化度的50%以上,并与矿化度呈正相关关系,Na+、Ca2+、K+浓度也与矿化度呈正相关关系。根据盐泉水的钠氯系数和溴氯系数判断,盐泉水属于地层溶滤水;源泉河、东温泉、多格错仁湖南岸3处的盐泉水具有与侏罗纪海水相一致的硫同位素特征,表明其在地下运移时,很可能溶解了地层中的石膏沉积;盐泉水的1000/Sr-87Sr/86Sr投点图说明各处盐泉水在地下的运移路径和形成过程明显不同;盐泉水的87Sr/86Sr值与其区域背景值对比显示,盐泉水在形成过程中可能溶滤了夏里组二段和索瓦组一段中的蒸发岩,区内夏里组和索瓦组最有可能蕴含有成盐成钾层系。     

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