准噶尔西北部塔尔巴哈台组早石炭世植物和遗迹化石的发现及其古地理意义*

首次在准噶尔西北部塔尔巴哈台组上部发现了早石炭世维宪期植物化石 Archaeocalamites scrobiculatus,Sublepidodendron grabaui,S. mirabile,S. cf. mirabile,Sublepidodendron sp., Lepidodendropsis sp., Mesocalamites sp., Sigillaria sp., Rhodiopteridium?sp.,Knorria sp.,证实了该组的时代可延续到早石炭世。根据研究区塔尔巴哈台组和上覆黑山头组的生物组合面貌及二者的接触关系,论证了塔尔巴哈台组顶部和黑山头组在准噶尔西北部具有明显的穿时性,前者从杜内期延续到维宪期,后者从杜内期延续到谢尔普霍夫期。与植物化石共同保存的深水相遗迹化石指示了塔尔巴哈台地区在早石炭世早中期为半深海-深海沉积环境,不同于东部吉木乃地区同期的滨浅海沉积环境,说明准噶尔西北部在早石炭世存在着不同的沉积体系。北疆地区早石炭世广泛的海侵活动以及额尔齐斯-斋桑洋向南侧哈萨克斯坦板块俯冲是造成这种沉积差异的主控因素,同时也造成了塔尔巴哈台组和黑山头组在区域上具穿时性。     

THEMIS statistical study on the plasma properties of high-speed flows in Earth’s magnetotail

Using Time History of Events and Macroscale Interactions during Substorms(THEMIS) observations from 2007 to 2011 tail seasons, we study the plasma properties of high speed flows(HSFs) and background plasma sheet events(BPSs) in Earth's magnetotail(|Y_(GSM)|13R_E, |Z_(GSM)|5R_E, –30R_EX_(GSM)–6R_E), and their correlations with solar wind parameters. Statistical results show that the closer the HSFs and BPSs are to the Earth, the hotter they become, and the temperature increase of HSFs is larger than that of BPSs. The density and temperature ratios between HSFs and BPSs are also larger when events are closer to Earth. We also find that the best correlations between the HSFs(BPSs) density and the solar wind density occur when the solar wind density is averaged 2(3.5) hours prior to the onset of HSFs(BPSs). The normalized densities of both HSFs and BPSs are correlated with the interplanetary magnetic field(IMF) θ angles(θ=arctan(B_Z/((B_x~2)+(B_y~2))~(1/2) which are averaged 3 hours before the observation time. Further analysis indicates that both HSFs and BPSs become denser during the northward IMF period.     

Sedimentary evidence of Late Holocene human activity in the Pearl River delta,China

This study examines the sedimentary evidence of human activities during the last 4000 years in the Pearl River deltaic area. The analyses are focused on indentifying agricultural signatures present in the sedimentary record and establishing the timing of a change from a simple, rice‐based agriculture to a more advanced, diverse agriculture. The examination is based on modern sediment and plant samples and a sediment core collected from the deltaic area. The analyses include particle size and diatom analysis to determine the environmental conditions that were associated with the period of human activities. Organic carbon isotope ratios and major metal elements reveal an expansion in commercial crop production and metal smelting in the Pearl River delta area about 2000 years ago. The input of organic matter from introduced sugarcane, a C4 plant, elevates the bulk organic carbon isotope values in the estuarine sediments above that represented by other common agricultural crops in the study area, including rice, banana and lotus, which are all C3 plants. The increase in bulk organic isotopic value coincides with the rise in the concentration of copper, iron and lead in the sedimentary sequence, suggesting a wider use of metal tools. These results indicate that advanced agriculture started about 2000 years ago as an expansion in human population took place in the area. This record also provides sedimentary evidence that help ascertain the timing and type of human activities that are linked to subsequent land reclamation on the deltaic plain, resulting in rapid shoreline advancement in the last 2000 years. Copyright © 2010 John Wiley & Sons, Ltd.     

Cassini growth of population between two metropolitan cities—A case study of Beijing-Tianjin region, China

The existing models of population distribution often focus on the region with a single city or even multiple centers, and lack the detailed explorations of the common and special type of urbanization areas with two centers. Taking Beijing-Tianjin region of China, which is a distinct dual-nuclei metropolitan area in the world, as an example and choosing Landsat-5 TM image in 2005, population, etc. as the data, this paper devotes to comprehending and illustrating a model of Cassini growth of population between the two metropolitan cities through the research of spatial population distribution pattern, aided with RS and GIS techniques. Main technical processes include Kriging interpolation of the population data and character simulation of the Cassini ovals. According to the calculation of a/b, a key characteristic index of Cassini growth model, the spatial structures of population distribution were given. When a/b<1, it is a curve with two separated loops with a population density more than 3000 persons/km². When a/b=1, it is a lemniscate curve with a population density about 3000 persons/km². When 1<a/b√2, it is a dog-bone shaped concave curve with a population density between 500–3000 persons/km². When a/b=√2, it is an oblate curve with a population density about 500 persons/km². When a/b>√2, there is an oval-shaped convex curve with a population density less than 500 persons/km². The results show that owing to the combined action and influence of the regional dual-nuclei, the population distribution of Beijing-Tianjin region is in accord with Cassini model significantly. There-fore, there is Cassini growth of population between the two metropolitan cities in Beijing-Tianjin region. In addition, the process of Cassini growth has extraordinarily instructive significance for judging the development stages of the dual-nuclei metropolitan areas. Foundation item: Under the auspices of National High-Tech Research and Development Program of China (863 Program) (No. 2007AA12Z235), National Natural Science Foundation of China (No. 40471058)     

云南砚山晚二叠世煤中V、Cr、Mo和U的丰度与赋存状态

运用电离耦合等离子体质谱(ICP-MS)和逐级化学提取(SCEE)的方法测定了云南砚山晚二叠世煤中金属元素的含量,发现煤中高度富集V、Cr、Mo和U,含量分别为621 μg/g、315 μg/g、198 μg/g和167 μg/g.逐级化学提取结果表明,这4种元素主要赋存在有机质和硅铝化合物中,反映其是在泥炭聚集期间或成岩作用早期进入到泥炭沼泽而富集的.     

Simultaneous Determination of Major and Trace Elements in Fused Volcanic Rock Powders Using a Hermetic Vessel Heater and LA‐ICP‐MS

Fused glass prepared without the addition of a flux is generally more homogeneous than a pressed powder pellet and thus ideal for analysis of bulk samples by LA‐ICP‐MS. In this work, a new glass‐making method using a boron nitride crucible was developed to prepare homogenous glass samples from silicate rock powder. The apparatus consisted of a small boron nitride vessel with net volume of about 34 mm³ and two molybdenum strips. Applying the summed metal oxide normalisation technique, both major and trace element contents in the fused glass were measured by LA‐ICP‐MS. Analyses of five geochemical reference materials (spanning the compositional range basalt–andesite–rhyolite) indicated that the measured SiO₂, Al₂O₃ and P₂O₅ contents matched the preferred values to within 5%, and the other major elements generally matched the preferred values to within 8%. Except for the transition metals, the measured trace element contents generally matched the preferred values to within 10%. Compared with the iridium heater method developed by Stoll et al. (2008), element volatilisation during high‐temperature melting was effectively suppressed in our method, but metal segregation caused by reduction of BN may cause loss of Cr, Ni and Cu. Although analysis with a large spot size has the advantage of improving counting statistics, matrix effects induced by mass loading of the ICP may hamper the accurate determination of some elements.     

Re-examination of tropical cyclone formation in monsoon troughs over the western North Pacific

The monsoon trough(MT) is one of the large-scale patterns favorable for tropical cyclone(TC) formation over the western North Pacific(WNP). This study re-examines TC formation by treating the MT as a large-scale background for TC activity during May–October. Over an 11-year(2000–10) period, 8.3 TC formation events on average per year are identified to occur within MTs, accounting for 43.1% of the total TC formation events in the WNP basin. This percentage is much lower than those reported in previous studies. Further analysis indicates that TC formation events in monsoon gyres were included at least in some previous studies. The MT includes a monsoon confluence zone where westerlies meet easterlies and a monsoon shear line where the trade easterlies lie north of the monsoon westerlies. In this study, the large-scale flow pattern associated with TC formation in the MT is composited based on the reference point in the confluence zone where both the zonal and meridional wind components are zero with positive vorticity. While previous studies have found that many TCs form in the confluence zone, the composite analysis indicates that nearly all of the TCs formed in the shear region, since the shear region is associated with stronger low-level relative vorticity than the confluence zone. The prevailing easterly vertical shear of zonal wind and barotropic instability may also be conducive to TC formation in the shear region, through the development of synoptic-scale tropical disturbances in the MT that are necessary for TC formation.     

秦岭造山带金属成矿系统

秦岭造山带是一个多旋回复合大陆碰撞造山带，是我国重要的多金属成矿带之一，自太古代以来秦岭经历了四大构造演化阶段及多种构造体制的转化，导致了多期构造热事件和成矿作用的发生，形成了多个构造成矿旋回，为秦岭金属元素的大规模富集成矿创造了条件，根据构造，建造，成矿作用及矿床组合特征，从早到晚可将秦岭区域成矿划分为六大成矿系统。其中，中晚元古代与海相火山岩及岛弧菌浆活动有关的成矿系统，早古生代与海相火山热液有关的成矿系统，海西期与海底热液及岩浆作用有关的成矿系统及中生代与陆内造山体制构造一岩浆活动有关的成矿系统对成矿的贡献最大，成矿系统的叠加是区内大多数大型，超大型矿床形成的前提。     

长庆气田靖边区北部奥陶系马五1储层难采储量区块综合评价

鄂尔多斯盆地长庆气田靖边区北部奥陶系马五1储层天然气藏因春开采难度较大，被称之为难采区，然其难采程度不一致，且存在较大差异，通过分析天然气难采主控因素－产能的高低及分布状况，进一步了解影响产能的沉积－成岩微相特征、储集物性、岩溶古地貌等因素，将难采程度分为最难采、难采、较难采3类，建立评价标准，并对研究区难采储量区块进行综合评价。     

鄂尔多斯盆地东缘C-P煤系致密砂岩储层敏感性分析

鄂尔多斯盆地临兴地区上古生界致密砂岩储集层中矿物组成多样、孔隙结构复杂且黏土矿物含量高,直接影响储层改造和开发效果。文章基于X 衍射、铸体薄片、气测孔渗、压汞和敏感性实验,系统研究了储层敏感性及其影响因素。结果表明研究区砂岩中石英和岩屑含量高,长石含量较低,以岩屑砂岩、岩屑石英砂岩、长石岩屑砂岩和石英砂岩为主。黏土矿物主要为伊利石、高岭石、绿泥石以及伊/蒙混层;储层普遍低孔低渗,孔隙结构较差。速敏以太原组最强,山西组最弱,与伊利石+绿泥石含量正相关,高岭石含量负相关。水敏下石盒子组最强,太原组最弱,与伊/蒙混层含量正相关。盐敏与水敏有类似特点,与伊/蒙混层含量表现出正相关。酸敏山西组最强,下石盒子组最弱,与绿泥石和铁白云石矿物含量正相关。碱敏性山西组最强,太原组最弱,受长石、石英和高岭石含量影响。相关认识有助于指导研究区钻井、压裂等施工工艺选择和排采控制。