An Evaluation of the Effects of Primary and Cross‐Contamination during the Preparation of Rock Powders for Chemical Determinations          下载免费PDF全文

José P. Sertek  Sandra Andrade  Horstpeter H. Ulbrich 《Geostandards and Geoanalytical Research》2015,39(3):381-397

Quartz crystals from the Batatal site, Minas Gerais, southern Brazil, were used to determine quantitatively primary contamination when submitting the samples to milling processes. Crushing devices used were a primary steel jaw crusher (br1), a secondary tungsten carbide (WC) crusher (br2) and a hydraulic press with stainless steel plates (pr). Fragments with suitable sizes were then ground in different Fritsch planetary mills, equipped with agate, WC and chromium‐steel rings for 7, 4 and 3 min, respectively. Solutions of the powders were analysed initially with the TotalQuant^? method in a quadrupole ICP‐MS instrument, providing semi‐quantitative results for seventy‐five elements. Contamination from crushers and mills was visible in major and minor elements such as Fe, Mn and Ti, and noticeable in trace elements such as Cr, Co, Ni, Cu and also V, Zr, Sc; significant contamination was observed from W, Mo, Co, Ta and Nb (mainly by use of the WC devices). Little or no contamination was observed for Pb, REE, Sr and Rb, elements that are important in routine isotopic determinations. Cross‐contamination was tested by grinding either a granite or a basalt sample, followed by conventional cleaning with mica‐free quartz sand, before the working quartz powder was prepared.  相似文献   

银额盆地石炭-二叠系包裹体成分特征对油气运移的讨论     

韩伟  任战利  卢进才  魏建设  张云鹏 《吉林大学学报(地球科学版)》2015,(5):1342-1351

包裹体成分特征反映了油气的演化程度和运移期次。本文对银额盆地石炭-二叠系4组地层砂岩中的包裹体开展研究,发现研究区包裹体多≤5μm,呈串珠状分布于石英颗粒裂隙中,以气液两相的状态存在。根据包裹体中甲烷等有机组分的含量及其相互关系对研究区油气运移过程展开研究,认为二叠系至少经历过较高温较高盐度、较低温低盐度等两期油气运移;结合烃源岩热演化史研究,可分别对应二叠纪中期-二叠纪末和白垩纪早-晚期两期油气运移过程。  相似文献   

中国南部OIS5e时期中亚热带北移的古生物学证据     

李志文  李保生  孙丽  王丰年 《第四纪研究》2015,35(3)

大熊猫-剑齿象动物群是中国南方地区第四纪的代表性哺乳动物群,常见种属多见于亚热带地区,少数种属在自然状态下主要分布于热带-南亚热带地区,如猩猩、长臂猿、亚洲象和绝灭种巨貘、中国犀的现生种貘、犀等热带种,它们的存在指示了具热带气候性质的中亚热带南部的森林环境.本文在确定中国南部OIS 5e时期此类动物群种属构成与分布特征的基础上,主要以热带种属的分布及其北界为依据,推断出中业热带北界分布至秦岭-淮河以南,较现今北移约3°,1月份平均温较今高约4～5℃,年均温高约3℃,说明在现今的亚热带地区盛行中亚热带-热带的气候环境,发生了较大的生物-气候带变迁.该变迁事件对应于全球气候变化的高温期和35°N冬半年天文辐射总量的峰值,是全球气候变化影响下的结果.  相似文献   

电子商务信息及信息流的理论分析   总被引：9，自引：0，他引：9  

梁弘秀  黄宗捷 《成都信息工程学院学报》2002,17(3):200-205

在全部电子商务活动中，凭借电子化或网络化而进行生产、储存、传递和管理的信息，即电子商务信息，它具有数量庞大增长迅速等七大特征；电子商务信息的运动过程形成信息流，它具有不同的分类，具有双向及时互动等诸方面的基本特征；具有多方面的功能。  相似文献   

Late‐glacial and Holocene high‐altitude environmental changes in Vallée des Merveilles (Alpes–Maritimes,France): insect evidence     

Philippe Ponel  Valrie Andrieu‐Ponel  Franck Parchoux  Imola Juhasz  Jacques‐Louis de Beaulieu 《第四纪科学杂志》2001,16(8):795-812

  相似文献   

Deep‐sea channel evolution and stratigraphic architecture from inception to abandonment from high‐resolution Autonomous Underwater Vehicle surveys offshore central California     

Katherine L. Maier  Andrea Fildani  Charles K. Paull  Timothy R. McHargue  Stephan A. Graham  David W. Caress 《Sedimentology》2013,60(4):935-960

The Lucia Chica channel system is an avulsion belt with four adjacent channels that progressively avulsed to the north‐east from a single, upslope feeder channel. Avulsion occurred from underfilled channels, leaving open channels that were reactivated by flows stripped from younger, adjacent channels. Differences in relief (height from channel thalweg to levée crest), sinuosity and levée stratigraphy between adjacent channels correspond to relative channel age, and indicate a change in channel morphology and architecture with time. Potential triggers for the change over time include differences in gradient, flow behaviour and characteristics, and channel evolution. Gradient does not appear to be a major control on channel formation and avulsion because adjacent channels formed on the same gradient. Based on available ultra‐high‐resolution remote imaging obtained with an Autonomous Underwater Vehicle, differences in adjacent channel morphology are interpreted to be primarily a result of differences in channel maturity. The interpreted sequence of channel maturity involves erosional channel inception through scouring and incipient channels (defined by linear trains of scours) prior to development of continuous thalwegs. Channel narrowing, formation and growth of levées, increasing channel relief and development of sinuosity occurred as channels evolved. The evolutionary sequence interpreted from the high‐resolution Lucia Chica dataset provides a unique perspective on intrinsic controls of architecture for single channel elements. In addition to helping bridge the gap between outcrop and industry‐standard reflection‐seismic data resolutions and scopes, interpretations in this study also expose potential problems with hierarchical classifications in three‐dimensional imaging of distributary systems, and provide potentially important analogues for evolutionary morphologies not resolved in other deep‐water channel systems.  相似文献   

Ressaut de marée et Mascaret – exemples de la Garonne et de la Seine     

Natalie Bonneton  Philippe BonnetonJean-Paul Parisot  Aldo SottolichioGuillaume Detandt 《Comptes Rendus Geoscience》2012,344(10):508-515

In this article, we present a study on the tidal bore dynamics based on the analysis of the database acquired in 2011 during two simultaneous field campaigns in the Seine and Garonne Rivers. We have shown that in the Garonne River, contrary to the common view, undular tidal bore can form for a large majority of tides, even sometimes at neap tide when the river discharge is low. We have identified, from surface elevation measurements, low-steepness, low-frequency undular tidal bores which are not visually observable. Such low-frequency tidal bores have been also identified and characterised for the first time in the Seine River. In this river, the first undulation wave height can be higher than 1 m. We have shown that the secondary wave steepness strongly increases when the Froude number exceeds the critical value <em>Fem>_<em>cem>. The large-steepness tidal bore regime corresponds to what is commonly termed in French <em>mascaretem>.  相似文献   

Notes     

W. Oldershaw 《Australian Journal of Earth Sciences》2013,60(2):197-199

There are more than 300 sediment-hosted Zn–Pb deposits and occurrences in Iran and most of them occur within carbonate rocks, including world-class deposits such as Mehdiabad, Irankuh and Angouran. To achieve a broad metallogenetic framework for carbonate-hosted (CH) Zn–Pb resources in Iran, we developed a GIS database with all reported deposits and occurrences of this affinity. From this database and the age of host rocks, two major groups of CH Zn–Pb deposits can be established and linked to different tectonic events: (a) Permian–Triassic-hosted deposits (mainly of the Mississippi Valley-type; MVT), and (b) Cretaceous-hosted deposits. The Permian–Triassic-hosted deposits are concentrated in the Central Alborz metallogenic belt, the NE margin of Sanandaj–Sirjan Zone (SSZ), and the Tabas-Posht e Badam metallogenic belt, whereas those hosted by Cretaceous carbonate rocks are distributed in the SSZ, the Yazd Block and the Central Iranian Geological and Structural (CIGS) transitional zone. In addition, the formation of numerous F-rich deposits hosted by Permian–Triassic carbonate rocks is also explained by a MVT deposit model. According to our GIS-based metallogenic maps, there is a significant correspondence between the distribution of CH Zn–Pb deposits and the main suture zones in and around the Iran Plate. Most of the orogenic Permian–Triassic-hosted MVT deposits occur along the suture zones that resulted from the collision of the Iran Plate with the Eurasia Plate when the Paleo-Tethys Ocean closed (during Upper Triassic time). The close spatial, temporal and (therefore assumed) genetic relationships between the Permian–Triassic-hosted MVT deposits and the Main-Cimmerian orogenic events reflect the development of a foreland basin during the Upper Triassic, which encompassed Zn–Pb and F mineralising processes. The modern distribution of these deposits in Iran is explained by the formation of this foreland basin, and by the subsequent (post-Upper Triassic) fragmentation of the Central Iranian Microcontinent into blocks that rotated along right-lateral strike-slip faults. This late process split the Permian–Triassic-hosted MVT province into the Tabas-Posht e Badam and the Central Alborz metallogenic belts.  相似文献   

南秦岭勉略构造带高压基性麻粒岩变质作用及其锆石U-Pb年龄   总被引：1，自引：1，他引：0  

梁莎  刘良  张成立  杨永成  杨文强  康磊  曹玉亭 《岩石学报》2013,29(5):1657-1674

勉县-略阳地区是勉略蛇绿构造混杂岩带的代表区段,本文在勉县北部徐家坪地区确定了主要矿物为Grt+Cpx+Pl和具有典型"白眼圈"反应结构的两类高压基性麻粒岩,分别对其进行细致的岩相学研究,并利用THERMOCALC3.33程序进行P-T视剖面图计算。一类高压基性麻粒岩的峰期矿物组合为Grt1+Cpx+Pl1+Qz,对应温压条件为T=800～860℃,P=12.4～14.6kbar,晚期退变质矿物组合为Grt2+Hbl+Pl2+Qz。另一类是具有典型"白眼圈"反应结构的高压基性麻粒岩,"白眼圈"结构中斜长石为富Na的钠-更长石,以此推断该高压基性麻粒岩早期矿物组合中含绿辉石,因此其变质峰期矿物组合可能为Grt1+Omp(?)+Qz或Grt1+Cpx(?)+Pl+Qz,对应温压条件分别为T=775～900℃,P>19.2kbar和T=750～850℃,P=16.5～19.8kbar;该岩石后期经历了以矿物组合Grt2+Opx+Hbl1+Pl1+Qz为代表的麻粒岩相及以Grt3+Hbl2+Pl2+Qz为代表的角闪岩相两期退变质作用。造成这两种高压基性麻粒岩峰期变质矿物组合及其温压条件存在差异的原因可能是岩石原始成分的不同。对高压基性麻粒岩及其中的浅色脉体分别进行了LA-ICP-MS锆石U-Pb年代学分析,得到高压基性麻粒岩214±11Ma的变质年龄及脉体215±5Ma的结晶时代,并结合锆石微量元素特征分析,认为214±11Ma的年龄值代表该高压基性麻粒岩角闪岩相的退变质时代,同时获得该高压基性麻粒岩原岩形成时代可能为477Ma。综合两件高压基性麻粒岩的P-T演化轨迹及变质时代,建立高压基性麻粒岩的P-T-t演化轨迹,据此反映秦岭造山带在印支期沿勉略构造带发生俯冲-碰撞造山过程。  相似文献   

Ordovician backarc‐basin metadolerite and metabasalt of the South Kitakami Terrane,Northeast Japan          下载免费PDF全文

Takayuki Uchino  Makoto Kawamura 《Island Arc》2016,25(4):274-286

Basement rocks that occur along the northern margin of the South Kitakami Terrane in Japan consist of Ordovician ultramafic rocks (Hayachine ultramafic complex), gneissose amphibolite (Kuromoriyama amphibolite), and mafic rocks (Kagura igneous rocks, KIR). The KIR are composed of metagabbro, metadolerite, metabasalt, and minor felsic–intermediate dikes. Although the KIR contain green hornblende due to metamorphism of greenschist to epidote–amphibolite facies, they rarely retain primary brown hornblende. Approximately 30% of the metabasalt shows porphyritic textures, with phenocrysts of saussuritized plagioclase and/or altered mafic minerals. The geochemistry of the common metadolerite and metabasalt of the KIR shows a tholeiite trend, a low TiO₂ content, and high Th/Nb and Ti/V ratios. The KIR are therefore indicative of a supra‐subduction zone tectonic setting, which implies a backarc origin (as also indicated by discrimination diagrams). Trace element patterns of the KIR resemble those of the backarc‐basin basalt of the Japan and Yamato basins in the Japan Sea. We propose that the KIR formed during backarc spreading from the Ordovician to Early Silurian. This view is supported by the geochemical data, the tectonic setting of the Hayachine ultramafic rocks, and the provenance of clastics within Silurian sedimentary rocks.  相似文献