Clay mineralogy of the ocean sediments from the Wilkes Land margin,east Antarctica: implications on the paleoclimate,provenance and sediment dispersal pattern   总被引：1，自引：0，他引：1  

Kamlesh Verma  Sanjeeb Bhattacharya  P. Biswas  Prakash K. Shrivastava  Mayuri Pandey  N. C. Pant  IODP Expedition Scientific Party 《International Journal of Earth Sciences》2014,103(8):2315-2326

Core U1359 collected from the continental rise off Wilkes Land, east Antarctica, is analyzed for the clay mineralogy and carbon content. The temporal variation of the clay mineralogical data shows a dominance of illite with chlorite, smectite and kaolinite in decreasing concentration. Clay mineral illite is negatively correlated with smectite which shows enrichment during 6.2–6.8, 5.5–5.8, 4.5 and 2.5 Ma. The mineralogical analyses on the silt size fraction (2–53 μm) of some selected samples were also carried out. The combined result of both the size fractions shows the presence of chlorite and illite in both size fractions, smectite and kaolinite only in clay size fraction (<2 μm) and similarity in the crystallinity and chemistry of illite in both fractions. Similar nature of illite in both fractions suggests negligible role of sorting probably due to the deposition from the waxing ice sheet. During times of ice growth, nearby cratonic east Antarctica shield provided biotite-rich sediments to the depositional site. On the other hand, the presence of smectite, only in the clay size fraction, suggests the effective role of sorting probably due to the deposition from distal source in ice retreat condition. During times of ice retreat, smectite-rich sediment derived from Ross Orogen is transported to the core site through surface or bottom water currents. Poor crystallinity of illite due to degradation further corroborates the ice retreat condition. The ice sheet proximal sediments of U1359 show that in the eastern part of Wilkes Land, the ‘warming’ was initiated during late Miocene.  相似文献   

贵州五指山背斜纳雍枝铅锌矿地质特征及找矿前景分析     

吴先彪  朱尤清  廖树衡  锁瑞强 《地质与资源》2013,22(6):493-498

纳雍枝铅锌矿床位于五指山背斜北东部,是五指山矿集区的组成部分.区内铅锌矿体产于清虚洞组的白云岩中,自下而上共划分为9个矿体层,属沉积型铅锌矿床.矿石类型为碳酸盐岩型铅锌矿石.五指山地区位于紫云-垭都深大断裂的北东侧,南东侧有安顺-凯里深断裂,这些深断裂是纳雍枝矿床深部物质来源的前提,次一级的构造为矿床的形成提供了矿质流动的通道.五指山背斜Pb、Zn综合异常明显的部位,异常与区内构造较吻合,与矿床(点)展布方向一致.该矿床与典型密西西比河谷铅锌矿床具有较高的可比性.通过对纳雍枝铅锌矿床地质特征的总结及分析,认为五指山地区的找矿前景十分广阔.  相似文献   

The surficial nature of lunar swirls as revealed by the Mini-RF instrument     

C.D. Neish  D.T. Blewett  S.J. Lawrence  B.J. Thomson  The Mini-RF Team 《Icarus》2011,215(1):186-196

Lunar swirls are optically bright, sinuous albedo features found on the Moon. The Mini-RF synthetic aperture radar on the Lunar Reconnaissance Orbiter has provided a comprehensive set of X- and S-Band radar images of these enigmatic features, including the first radar observations of swirls on the farside of the Moon. A few general remarks can be made about the nature of the lunar swirls from this data set. First, the average radar properties of lunar swirls are identical to nearby non-swirl regions, in both total radar backscatter and circular polarization ratio (CPR). This implies that average centimeter-scale roughness and composition within the high-albedo portions of the swirls do not differ appreciably from the surroundings, and that the high optical reflectance of the swirls is related to a very thin surface phenomenon (less than several decimeters thick) not observable with X- or S-Band radar. Secondly, bright swirl material appears to be stratigraphically younger than a newly discovered impact melt flow at Gerasimovich D. This observation indicates that the swirls are capable of forming over timescales less than the age of the crater. The Mini-RF data set also provides clues to the origin of the lunar swirls. In at least one case, the presence of an enhanced crustal magnetic field appears to be responsible for the preservation of a high-albedo ejecta blanket around an otherwise degraded crater, Descartes C. The degree of degradation of Descartes C suggests it should not be optically bright, yet it is. This implies that the enhanced albedo is related to its location within a magnetic anomaly, and hence supports an origin hypothesis that invokes interaction between the solar wind and the magnetic anomaly.  相似文献   

Effects of hydrocarbon physical properties on caprock’s capillary sealing ability     

ZHANG LinYe  BAO YouShu  LIU Qing  ZHANG ShouChun  ZHU RiFang & ZHANG Lei Geology Scientific Research Institute  SinoPec Shengli Oilfield Company  Dongying  China 《中国科学:地球科学(英文版)》2010,(5)

A new mechanics formula of caprock’s capillary sealing ability has been established in this paper, in which the boundary layer resistance was considered and characterized by starting pressure gradient. The formula shows that capillary sealing ability of caprock is determined not only by the capillary force of rock and the buoyancy of hydrocarbon column, but also by the starting pressure gradient of hydrocarbons and the thickness of caprock. The buoyancy of hydrocarbon column, the starting pressure gradient of hydrocarbon, and the capillary force of caprock are affected by hydrocarbon density, hydrocarbon viscosity, and hydrocarbon-water interface tension respectively. Based on hydrocarbon property data of reservoirs of Jiyang Depression and equations from literature, the effects of hydrocarbon density, hydrocarbon viscosity, and hydrocarbon-water interface tension on the sealing ability of caprock are analyzed. Under formational conditions, the sealing ability of oil caprock can vary up to dozens times because of the variations of the oil density, oil viscosity, and oil-water interface tension. Thus, the physical characters of hydrocarbon should be considered when evaluating the capillary sealing ability of caprocks. Study of the effects of physical characters on sealing ability of caprock can provide guidance to exploring special physical property hydrocarbon resources, such as viscous oils, and hydrocarbon resources in special pressure-temperature environments.  相似文献   

西藏班戈地区雪如岩体的形成环境及成矿意义     

高顺宝  郑有业  谢名臣  张众  闫学欣  武斌  罗俊杰 《地球科学》2011,36(4):729-739

雪如岩体主要由中细粒二长花岗岩、中粗粒斑状二长花岗岩组成,在其与郎山组灰岩接触带附近发育有大量的矽卡岩型铜铁矿床或矿化点.岩石及锆石LA-ICP-MS U-Pb、XRF、ICP-AES等分析显示,雪如岩体富K₂O、SiO₂、LREE及Rb、Ba、Pb、Th等大离子亲石元素,而Nb、Ta、Sr、Ti等高场强元素含量相对较低,稀土元素配分曲线为明显的右倾曲线,具有中等的负Eu异常,属高钾钙碱性-钾玄岩岩石系列和后碰撞花岗岩类,成岩时代分别为79.25±0.97 Ma和79.72±0.51 Ma,形成于早白垩世末-晚白垩世初班公湖-怒江缝合带闭合后、羌塘地体与拉萨地体的后碰撞阶段.综合认为,雪如岩体岩浆源区为下地壳富含流体的石榴石角闪岩相-斜长角闪岩相的镁铁质岩石,是在后碰撞环境下经部分熔融形成的花岗岩类,对班戈地区铜铁多金属成矿非常有利;矽卡岩型铜铁成矿作用发生于80 Ma左右,该认识为区域找矿指明了方向.   相似文献   

Titan's surface from the Cassini RADAR radiometry data during SAR mode     

F. Paganelli  M.A. Janssen  E. Stofan  R.D. Lorenz  R.L. Kirk  C. Elachi  The Cassini Radar Team 《Planetary and Space Science》2008,56(1):100-108

We present initial results on the calibration and interpretation of the high-resolution radiometry data acquired during the Synthetic Aperture Radar (SAR) mode (SAR-radiometry) of the Cassini Radar Mapper during its first five flybys of Saturn's moon Titan.We construct maps of the brightness temperature at the 2-cm wavelength coincident with SAR swath imaging. A preliminary radiometry calibration shows that brightness temperature in these maps varies from 64 to 89 K. Surface features and physical properties derived from the SAR-radiometry maps and SAR imaging are strongly correlated; in general, we find that surface features with high radar reflectivity are associated with radiometrically cold regions, while surface features with low radar reflectivity correlate with radiometrically warm regions. We examined scatterplots of the normalized radar cross-section σ⁰ versus brightness temperature, outlining signatures that characterize various terrains and surface features. The results indicate that volume scattering is important in many areas of Titan's surface, particularly Xanadu, while other areas exhibit complex brightness temperature variations consistent with variable slopes or surface material and compositional properties.  相似文献   

Stratigraphic analysis of the northern polar layered deposits of Mars: Implications for recent climate history     

Sarah M. Milkovich  James W. Head III  The HRSC Co-Investigator Team 《Planetary and Space Science》2008,56(2):266-288

We examine the stratigraphy of the polar layered deposits (PLD) within the north polar cap of Mars to assess its layer continuity, correlations, cyclicity and structure and implications for the recent climate record. PLD sequences characterized using Fourier analysis and curve shape matching algorithms show that layers correlate throughout the upper part of the PLD. We tested for cyclicity and found that the uppermost ∼300 m contain a dominant wavelength layer packet of ∼30 m, interpreted to be a climate signal related to the 51 kyr precession cycle. Directly below this region we document a section of polar layered deposits ∼100 m thick without a dominant periodic signal; this is interpreted to represent a phase of low net accumulation and lag deposits formed during the last ice age, about 0.5-2 Ma ago. We further analyzed layer structure by combining these results with three-dimensional determinations of layer orientation (strike and dip) to assess the internal stratigraphy of the PLD and its implications for polar history. We show that individual layers within the PLD stratigraphy are not horizontal (no dip) but rather show broad variation in elevation with distance. Correlations suggest that the layer strikes and dips broadly follow present cap surface topography. Local variations in layer orientations in the vicinity of the troughs suggest that (1) trough structures were present at the time of layer accumulation and (2) dips may have been influenced by ice flow and/or static ice accumulation in the presence of preexisting troughs. This new information favors models in which the troughs are long-term structures of the PLD rather than (1) recently eroded into the PLD, or (2) very active and laterally migrating around the PLD. Our results strongly support the hypothesis that significant volumes of polar volatiles are mobilized and transported equator-ward during periods of increased obliquity. Our results predict that the upper ∼300 m of the north polar PLD accumulated in the last 500 ka, yielding net accumulation rates of ∼0.06 cm/yr. The presence and albedo of the no periodic signal zone suggest that polar net accumulation rates are very low and that dust rich lag deposits form during periods of sustained high obliquity. Layer sequences in the south polar and equatorial regions are examined and compared to those in the north; rhythmic sequences are observed in both regions but no direct correlations to the dominant signals of the north polar deposits have yet been found. These new techniques and observations provide a paradigm for further analysis of recent polar history (the upper kilometer of the record) and a basis for extending assessments to the lower part of the polar deposits and to other cyclic deposits in the geological record of Mars.  相似文献   

Fluvial channels on Titan: Initial Cassini RADAR observations     

Ralph D. Lorenz  Rosaly M. Lopes  Jonathan I. Lunine  Karl L. Mitchell  Ellen R. Stofan  Melissa Myers  Jani Radebaugh  Stephen D. Wall  the Cassini RADAR Team 《Planetary and Space Science》2008,56(8):1132-1144

Cassini radar images show a variety of fluvial channels on Titan's surface, often several hundreds of kilometers in length. Some (predominantly at low- and mid-latitude) are radar-bright and braided, resembling desert washes where fines have been removed by energetic surface liquid flow, presumably from methane rainstorms. Others (predominantly at high latitudes) are radar-dark and meandering and drain into or connect polar lakes, suggesting slower-moving flow depositing fine-grained sediments. A third type, seen predominantly at mid- and high latitudes, have radar brightness patterns indicating topographic incision, with valley widths of up to 3 km across and depth of several hundred meters. These observations show that fluvial activity occurs at least occasionally at all latitudes, not only at the Huygens landing site, and can produce channels much larger in scale than those observed there. The areas in which channels are prominent so far amount to about 1% of Titan's surface, of which only a fraction is actually occupied by channels. The corresponding global sediment volume inferred is not enough to account for the extensive sand seas. Channels observed so far have a consistent large-scale flow pattern, tending to flow polewards and eastwards.  相似文献   

Observation of water vapor in the stratosphere of Jupiter with the Odin space telescope     

T. Cavalié  F. Billebaud  M. Dobrijevic  J. Brillet  Å. Hjalmarson  U. Frisk  E.A. Bergin  The Odin Team 《Planetary and Space Science》2008,56(12):1573-1584

The water vapor line at 557 GHz has been observed with the Odin space telescope with a high signal-to-noise ratio and a high spectral resolution on November 8, 2002. The analysis of this observation as well as a re-analysis of previously published observations obtained with the submillimeter wavelength astronomy satellite seem to favor a cometary origin (Shoemaker-Levy 9) for water in the stratosphere of Jupiter, in agreement with the ISO observation results. Our model predicts that the water line should become fainter and broader from 2007. The observation of such a temporal variability would be contradictory with an IDP steady flux, thus supporting the SL9 source hypothesis.  相似文献   

中国西部铂矿床类型与找矿方向探讨     

涂怀奎 《化工矿产地质》2004,26(4):220-227

中国铂矿资源严重不足,主要分布在中国西部,根据原生矿床特征可划分为4类：①硫化物型;②铬铁矿型;③辉石岩型;④层控型。寻找铂矿新类型和富铂(岩石)资源,应成为解决中国铂矿资源紧缺的重要任务。铂矿找矿方向：地台与地槽接合部位,特别是围绕着基性、超基性岩内外接触带,铂的预富集岩带与层控型铂矿带,另外还有砂铂型铂矿发育区有望扩大找铂前景。  相似文献