2008年T213与德国降水数值预报产品对比检验分析

为了解各种数值预报的误差特点,更好地在预报过程中选择数值预报产品作为参考依据,将中国国家气象中心的T213降水预报和德国降水预报分别进行晴雨预报检验,对2008年5—8月期间东北地区降水资料进行对比分析。结果表明：两种模式24—120h预报正确率为60%—70%左右,随着预报时效的增加,正确率呈下降趋势,德国降水预报的正确率高于T213,两种预报漏报率均明显小于空报率,T213漏报率较低,为5%左右,德国降水预报空报率较低,为20%左右。对2008年4—6月出现东北冷涡过程的两种模式降水预报进行对比分析,发现德国降水预报正确率明显高于T213预报,对冷涡降水预报有一定的指示意义。     

湘东北九岭-清水地区韧性剪切带型金矿控矿特征及找矿方向

九岭-清水韧性剪切带是湘东北三条区域规模的韧性剪切带之一,黄金洞、万古等金矿床就处于该剪切带上,是典型的受韧性剪切带控制的矿床。武陵-雪峰期的韧性剪切变形不仅形成了导矿通道和容矿空间,也促使冷家溪群含金建造成矿物质的活化迁移;加里东-燕山期形成的NE向深大断裂和伴随的大规模岩浆活动,导致成矿热液再次活化转移并沉淀成矿。韧性剪切构造为金成矿创造了空间条件,而且还通过力学-化学耦合机制参与活化转移成矿各个环节。本文总结了该类矿床的控矿特征和找矿标志,指出了该地区的找矿方向。     

桂东北海洋山岩体锆石SHRIMP U-Pb定年和地球化学研究

桂东北海洋山岩体为岩性单一的二长花岗岩岩基。锆石SHRIMP U-Pb定年显示海洋山岩体主结晶年龄为431±7 Ma(MSWD=3.14),与赣湘桂内陆加里东期花岗闪长岩-二长花岗岩形成时代相似,为同一期成岩事件的产物。元素地球化学研究表明,绝大多数样品具有富硅(～68%),富钾(K2O/Na2O>1.5),弱过铝质(A/CNK均值1.05)和低Al2O3/TiO2值(<100)、高CaO/Na2O值(>0.3)的特征。与临区浅变质基底一致的εNd(t)值(-8.0～-8.6)和T2DM值(1.82～1.87 Ga),指示其理想源区为成熟度较低的古老变质杂砂岩。进一步的宏观地质特征和华南加里东造山带构造演化序列分析表明,海洋山岩体属于陆壳改造型花岗岩,其形成的构造环境很可能为汇聚造山向非造山转化的后造山伸张环境。     

火山活动对彝良向斜煤矿区成煤环境的影响

依据彝良向斜煤矿区钻孔资料,峨眉山玄武岩之上的宣威组底部广泛分布着数层厚薄不一的凝灰质泥岩,煤层夹矸中有火山蚀变成因矿物组成的粘土岩,这些火山活动所形成的玄武岩、凝灰质泥岩、煤层粘土岩夹矸在时空分布特征上反映了火山活动的规律,火山活动控制着区域沉积环境及成煤环境的演变。研究区自西向东受火山活动的影响逐渐减弱而使东部的含煤性优于西部,煤层的分布与火山活动痕迹呈此消彼长的关系,反映了火山活动的逐渐减弱使得宣威晚期逐渐形成了稳定的成煤环境。因此,研究区东部宣威组上段地层是煤炭资源进一步勘查的重点。     

Re–Os and U–Pb geochronology of porphyry Mo deposits in central Jilin Province: Mo ore-forming stages in northeast China

Central Jilin Province lies along the eastern edge of the Xing–Meng orogenic belt of northeast China. At least 10 Mo deposits have been discovered in this area, making it the second-richest concentration of Mo resources in China. To better understand the formation and distribution of porphyry Mo deposits in the area, we investigated the geological characteristics of the deposits and applied zircon U–Pb and molybdenite Re–Os isotope dating to constrain the age of mineralization. Our new geochronological data show the following: the Jidetun Mo deposit yields molybdenite Re–Os model ages of 164.6–167.1 Ma, an isochron age of 168 ± 2.5 Ma, and a weighted mean model age of 165.9 ± 1.2 Ma; the Houdaomu Mo deposit yields molybdenite Re–Os model ages of 167.4–167.7 Ma, an isochron age of 168 ± 13 Ma, and a weighted mean model age of 167.5 ± 1.2 Ma; and the Chang’anpu Mo deposit yields a zircon U–Pb age for granodiorite porphyry of 166.9 ± 1.5 Ma (N = 16). These new age data, combined with existing molybdenite Re–Os dates, show that intense porphyry Mo mineralization was coeval with magmatism during the Middle Jurassic (167.8 ± 0.4 Ma, r > 0.999). The geotectonic mechanisms responsible for Mo mineralization were probably related to subduction of the Palaeo-Pacific plate beneath the Eurasian continent. Combining published molybdenite Re–Os and zircon U–Pb ages for northeast China, the Mo deposits are shown to have been formed during multiple events coinciding with periods of magmatic activity. We identified three phases of mineralization, two of which had several stages: the Caledonian (485–480 Ma); the Indosinian comprising the Early–Middle Triassic (248–236 Ma) and Late Triassic (226–208 Ma) stages; and the Yanshanian phase comprising the Early–Middle Jurassic (202–165 Ma), Late Jurassic–early Early Cretaceous (154–129 Ma), and Early Cretaceous (114–111 Ma) stages. Although Mo deposits formed during each phase/stage, most of the mineralization occurred during the Early–Middle Jurassic.     

祁连山大雪山地区大气PM2.5细粒子中可溶性离子特征

为了研究祁连山大雪山地区大气PM_2.5细粒子中可溶性无机离子组分的变化特征, 于2010年7月至2011年7月在祁连山冰川与生态环境综合观测站附近采集46个大气PM_2.5的Telfon滤膜样品, 并应用离子色谱对可溶性离子进行了分析.结果显示: 所测样品的阴、 阳离子中, SO₄^2-、 NO^-₃、 Ca²⁺和NH⁺₄的质量浓度分别为1.54μg·m^-3、 0.38μg·m^-3、 0.73μg·m^-3和0.22μg·m^-3, 累计约占到水溶性离子总量的88%.可溶性离子浓度呈现出春夏季节明显高于秋冬季节的特征, 夏季的浓度最高, 其次是春季、 冬季和秋季. Cl^-、 Ca²⁺、 Na⁺和Mg²⁺之间的相关性极高, SO₄^2-和NO^-₃与大部分阳离子的相关性都很高, 说明大部分硫酸盐是来自于中亚沙尘源区的自然源, 而并非是通过人类活动造成的一次污染物通过二次反应过程得到的. NH⁺₄仅与SO₄^2-通过相关性检验说明, 该地区NH₃主要中和了大气中硫酸并生成(NH₄)₂SO₄.该地区的大气环境主要来源于自然源的影响, 但夏季风期间人为污染排放已经不可忽视, 这也得到HYSPLIT后向轨迹模式的计算验证.     

Long-term sediment yield in Crombie Reservoir catchment,Angus; and its regional significance within the Midland Valley of Scotland

Abstract

The drawdown of Crombie Reservoir in November 2001 afforded the opportunity to examine the exposed sediments trapped since impoundment in 1868. Direct measurements of infill depth enabled an isopachyte map to be produced. Gravimetric conversion using measured bulk densities and a trap efficiency term indicated a long-term catchment sediment yield of 59.1 t km^?2 year^?1. Core stratigraphy analysis indicated that sediments were dark brown/black cohesive silty-muds with multiple sandy sub-units, representing a combination of discrete flood events and previous drawdown surfaces. Dating, constrained by mineral magnetic and ¹³⁷Cs analysis, indicated that sedimentation rates have varied from 0.2 to 0.8 g cm^?2 year^?1, corresponding to a four-fold variation in catchment sediment yield (approximately 20–93 t km^?2 year^?1), most likely controlled by extensive conversion of moorland to woodland, and post-World War II agricultural expansion. The Crombie investigation is combined with other reservoir sedimentation surveys within the Midland Valley of Scotland. Area-specific sediment yields (t km^?2 year^?1) evidence a weak, though statistically significant (p > 0.05), positive correlation with catchment area (km²). The increase in area-specific yield with catchment area contradicts the decline, which is generally expected, and is taken to reflect the significance of channel erosion within water supply basins featuring mainly natural and semi-natural vegetation cover and low-intensity land management practices. With stable slopes channel erosion dominates and area-specific sediment yield increases downstream due to greater entrainment and transport potential. The high degree of scatter in the Midland Valley database reflects significant variations in the extent of land-use change and the local importance of agricultural improvements and afforestation practices.     

东北佳木斯-内蒙古地区中二叠世岩相古地理研究

严格按照等时性对比原则,选取岩相古地理图的制图单元.以野外实测剖面为基础,做精细沉积微相研究,在东北地区地层露头剖面识别出海相(浅海亚相、半深海亚相)、三角洲相(三角洲前缘:水下分流河道、河口坝,前三角洲)沉积.在露头点测量基础上,以点带线、以线带面,分析古沉积环境.在野外剖面沉积微相精细划分基础上,结合区域地质资料,...     

Upper Water Column Nitrous Oxide Distributions in the Northeast Subarctic Pacific Ocean

This is the first study to investigate the magnitude and distribution of N₂O concentrations along the Line P oceanographic transect in the Northeast (NE) subarctic Pacific Ocean. Concentrations of N₂O were measured from the surface to 600 m depth at five stations between 126°W and 145°W. Although nitrification within the mixed layer may produce some N₂O, we conclude that mixing and diffusion processes, which vertically transport N₂O upwards from below the mixed layer, are the primary sources of N₂O to the surface waters of the NE subarctic Pacific Ocean. Below the mixed layer, nitrification appears to be the dominant source of N₂O, and based on correlations of excess N₂O (ΔN₂O) versus apparent oxygen utilization and NO₃ ^? concentrations, we estimated that the N₂O yield from nitrification was approximately 0.028 to 0.040%. The longitudinal distributions of N₂O concentrations below the mixed layer were variable and we consider the potential role that different transiting water masses may play in contributing to this variability. Finally, we estimated that the regional average sea-to-air N₂O flux was 4.37 mol of N₂O km^?2 d^?1, a value which is approximately four times that of the global average seawater-to-air flux rate. Our N₂O yield estimates are within the range of those expected under oxic conditions, leading us to conclude that decreasing dissolved O₂ concentrations in the NE subarctic Pacific Ocean, and the water masses that influence this region, over the past 50 years have yet to produce a substantial increase in N₂O production. Given the expectation that dissolved O₂ concentrations in the subarctic Pacific Ocean will continue to decrease during this century, this study has provided an important baseline from which future studies will be able to track changes in seawater N₂O concentrations and fluxes to the atmosphere.

[Traduit par la rédaction] La présente étude est la première à s'intéresser à la valeur et à la distribution des concentrations de N₂O le long du transect océanographique de la ligne P dans le Pacifique Nord-Est subarctique. Les concentrations de N₂O ont été mesurées de la surface jusqu’à une profondeur de 600 m à cinq stations entre 126°O et 145°O. Bien que la nitrification à l'intérieur de la couche de mélange puisse produire du N₂O, nous concluons que le mélange et les processus de diffusion, qui transportent verticalement le N₂O vers le haut à partir d'en dessous de la couche de mélange, sont les sources principales de N₂O pour les eaux de surface du Pacifique Nord-Est subarctique. En dessous de la couche mélange, la nitrification semble être la principale source de N₂O, et d'après les corrélations de l'excès de N₂O (ΔN₂O) par rapport à l'utilisation apparente d'oxygène et aux concentrations de NO₃ ^?, nous avons estimé que le rendement en N₂O de la nitrification était approximativement de 0,028 à 0,040%. Les distributions longitudinales des concentrations de N₂O en dessous de la couche de mélange étaient variables et nous considérons le rôle possible que des différentes masses d'eau transitoires peuvent avoir à jouer dans cette variabilité. Finalement, nous avons estimé que la moyenne régionale du flux mer–air de N₂O était de 4,37 moles de N₂O km^?2 j^?1, une valeur qui est environ quatre fois celle du taux planétaire moyen du flux eau de mer–air. Nos estimations du rendement en N₂O sont de l'ordre de celles attendues dans des conditions oxyques, ce qui nous amène à conclure que la diminution des concentrations d'oxygène dissout dans le Pacifique Nord–Est subarctique, et dans les masses d'eau qui influencent cette région, au cours des cinquante dernières années ont encore à produire une augmentation substantielle de production de N₂O. Étant donné qu'on s'attend à ce que les concentrations d'oxygène dissout dans le Pacifique subarctique continuent à diminuer durant le présent siècle, cette étude a fourni une importante base de référence à partir de laquelle de futures études pourront suivre les changements dans les concentrations de N₂O dans l'eau de mer et dans ses flux vers l'atmosphère.     

Preservation of Mesoproterozoic age deep burial fluid signatures,NW Scotland

Bedding-parallel fibrous calcite is a widely developed feature of mudrock successions, reflecting conditions of fluid overpressure (Stoneley, 1983, Parnell et al., 2000, Cobbold et al., 2013). The calcite preserves signatures of fluids developed during deep burial, including hydrocarbons. Most studied examples are of Phanerozoic (<540 Ma) age. This study reports well-preserved fibrous calcite in the Mesoproterozoic (∼1180 Ma) Stoer Group, NW Scotland. The fibrous calcite occurs immediately above a unit of carbonaceous black shale. If hydrocarbons were generated from the black shales, they could have contributed to the development of fluid overpressure, but there is no direct evidence for this. The calcite reflects the original deep burial fluid, rather than a later overprint, because (i) it has a distribution related to stratigraphy, (ii) the bedding-parallel fibres have not been recrystallized, and (iii) later veining is at high angles to bedding. The calcite contains fluid inclusions, and has yielded stable isotope and entrained volatile data, indicating the potential to record diagenetic processes over one billion years ago.