Alteration,Chemical Processes,and Parent Rocks of Haléo-Danielle Plateau Bauxite,Adamawa–Cameroon     

Nyamsari  D. G.  Yalçin  M. G.  Wolfson  I. 《Lithology and Mineral Resources》2020,55(3):231-243

Lithology and Mineral Resources - The Haléo-Danielle Plateau bauxite deposit forms the largest part of the 15 km long Minim-Martap Bauxite ore district in the Adamawa Region of Cameroon. The...  相似文献   

Chemical Composition,U–Th–Pb Age,and Geodynamic Setting of Metavolcanic Filla Series (Rauer Islands,East Antarctica)     

Mikhalsky  E. V.  Alexeev  N. L.  Kamenev  I. A.  Larionov  A. N.  Gogolev  M. A.  Svetov  S. A.  Kunakkuzin  E. L. 《Geotectonics》2020,54(3):285-307

Geotectonics - An assemblage of mafic granulites (schists), plagiogneisses, and metasedimentary rocks, which is referred to as the Filla Series, is exposed in the Rauer Islands (opposite the...  相似文献   

Tectono-sedimentary evolution of Jurassic–Cretaceous diapiric structures: Miravete anticline,Maestrat Basin,Spain     

Jaume Vergés  Yohann Poprawski  Ylènia Almar  Peter A. Drzewiecki  Mar Moragas  Telm Bover-Arnal  Chiara Macchiavelli  Wayne Wright  Grégoire Messager  Jean-Christophe Embry  David Hunt 《Basin Research》2020,32(6):1653-1684

Integration of extensive fieldwork, remote sensing mapping and 3D models from high-quality drone photographs relates tectonics and sedimentation to define the Jurassic–early Albian diapiric evolution of the N–S Miravete anticline, the NW-SE Castel de Cabra anticline and the NW-SE Cañada Vellida ridge in the Maestrat Basin (Iberian Ranges, Spain). The pre shortening diapiric structures are defined by well-exposed and unambiguous halokinetic geometries such as hooks and flaps, salt walls and collapse normal faults. These were developed on Triassic salt-bearing deposits, previously misinterpreted because they were hidden and overprinted by the Alpine shortening. The Miravete anticline grew during the Jurassic and Early Cretaceous and was rejuvenated during Cenozoic shortening. Its evolution is separated into four halokinetic stages, including the latest Alpine compression. Regionally, the well-exposed Castel de Cabra salt anticline and Cañada Vellida salt wall confirm the widespread Jurassic and Early Cretaceous diapiric evolution of the Maestrat Basin. The NE flank of the Cañada Vellida salt wall is characterized by hook patterns and by a 500-m-long thin Upper Jurassic carbonates defining an upturned flap, inferred as the roof of the salt wall before NE-directed salt extrusion. A regional E-W cross section through the Ababuj, Miravete and Cañada-Benatanduz anticlines shows typical geometries of salt-related rift basins, partly decoupled from basement faults. These structures could form a broader diapiric region still to be investigated. In this section, the Camarillas and Fortanete minibasins displayed well-developed bowl geometries at the onset of shortening. The most active period of diapiric growth in the Maestrat Basin occurred during the Early Cretaceous, which is also recorded in the Eastern Betics, Asturias and Basque-Cantabrian basins. This period coincides with the peak of eastward drift of the Iberian microplate, with speeds of 20 mm/year. The transtensional regime is interpreted to have played a role in diapiric development.  相似文献   

Soil resistances for laterally loaded rigid piles in multi-layered elastic soil     

Bipin K. Gupta 《Geomechanics and Geoengineering》2020,15(1):10-28

ABSTRACT

Short stubby piles like monopiles and large diameter drilled shafts undergo rigid body translation and rotation when subjected to a lateral force and/or a moment at the head. A method of analysis for these piles embedded in multi-layered elastic soil is developed using the variational principles of mechanics. Using this analysis, the soil resistance against pile movement can be rigorously related to the soil elastic constants, and the pile head displacement and rotation can be quickly calculated. The equilibrium equations for pile and soil displacements are obtained using the principle of virtual work and solved using an iterative algorithm. Pile responses obtained from the analysis match well with those obtained from three-dimensional finite element analyses in which the same inputs of loads, geometry, and material properties are given. Based on the new analysis, fitted equations for soil resistance parameters are developed, which can be used to directly calculate the pile head displacement and rotation without the use of the iterative algorithm. Numerical examples are provided that demonstrate how the method can be used to analyse practical problems.  相似文献   

Identification of Induced Seismicity in the Fault Zone of the Korobkovskoye Deposits (Kursk Magnetic Anomaly) Based on Observations of a Small-Aperture Seismic Array     

Adushkin  V. V.  Varypaev  A. V.  Kushnir  A. F.  Sanina  I. A. 《Doklady Earth Sciences》2020,493(1):548-551

Doklady Earth Sciences - The results of recording and determining the locations of seismic events triggered by industrial explosions conducted by OJSC Kombinat KMAruda at the Korobkovskoe iron ore...  相似文献   

Laser-Induced Dissociation of the Monolayer of Adsorbed Methanol Molecules     

Varakin  V. N.  Murga  M. S. 《Astronomy Reports》2020,64(4):319-325

Astronomy Reports - Astronomical observations indicate a high abundance of methanol molecules in the gas phase of molecular-cloud dense cores, which cannot be explained by gas-phase chemical...  相似文献   

Geography Deserts: State and Regional Variation in the Formal Opportunity to Learn Geography in the United States, 2005–2015     

Mark C. Jones  Marcos Luna 《The Journal of geography》2019,118(2):88-100

The formal opportunity to learn geography in the United States is unevenly distributed across space, creating possible geography deserts. Data on the number of exams taken in Advanced Placement Human Geography (APHG) and bachelor’s degrees earned in geography are mapped at the state and regional scales. Normalized rates are ranked and grouped into quintiles. For APHG exams, states in the southeastern region of the United States are in the uppermost quintiles while states in the northeastern region are in the lowermost quintiles. The pattern for bachelor’s degrees in geography is somewhat the spatial inverse of that for APHG.  相似文献   

Hyperspectral imaging of drill core from the Steen River impact structure,Canada: Implications for hydrothermal activity and formation of suevite‐like breccias     

E. A. MacLagan  E. L. Walton  C. D. K. Herd  B. Rivard 《Meteoritics & planetary science》2020,55(7):1564-1580

Hyperspectral imaging can be used to rapidly identify and map the spatial distributions of many minerals. Here, hyperspectral mapping in three wavelength regions (visible and near‐infrared, shortwave infrared, and thermal infrared) was applied to drill cores (ST001, ST002, and ST003) penetrating a continuous sequence of crater‐fill breccias from the Steen River impact structure in Alberta, Canada. The combined data sets reveal distinct mineralogical layering, with breccias derived predominantly from sedimentary rocks overlying those derived from granitic basement. This stratigraphy demonstrates that the breccias were not appreciably disturbed following deposition, which is inconsistent with formation models of similar breccias (suevites) by explosive impact melt–fluid interaction. At Steen River, volatiles from sedimentary target rocks were an inherent part of forming these enigmatic breccias. Approximately three quarters of terrestrial impact structures contain sedimentary target rocks; therefore, the role of volatiles in producing so‐called suevitic breccias may be more widespread than previously realized. The hyperspectral maps, specifically within the SWIR wavelength region, also delineate minerals associated with postimpact hydrothermal activity, including ammoniated clay and feldspar minerals not detectable using traditional techniques. These nitrogen‐bearing minerals may have originated from microbial processes, associated with oil‐ and gas‐producing units in the crater vicinity. Such minerals may have important implications for the production of habitable environments by impact‐induced hydrothermal activity on Earth and Mars.  相似文献   

Using Models of the Deep Structure of the Earth’s Crust and Upper Mantle Based on GOCE Gravity Data in Metallogenic Analysis     

Volkov  A. V.  Galyamov  A. L.  Savchuk  Yu. S. 《Izvestiya Atmospheric and Oceanic Physics》2020,56(12):1528-1536

Izvestiya, Atmospheric and Oceanic Physics - Gravimetric data obtained by the GOCE spacecraft contributes to the development of global models of the deep structure of the Earth’s crust and...  相似文献   

Connections between the Long-Period Variability Modes of Both Temperature and Depth of the Upper Mixed Layer of the North Atlantic and the Climate Variability Indices     

Sukhonos  P. A.  Diansky  N. A. 《Izvestiya Atmospheric and Oceanic Physics》2020,56(3):300-311

Izvestiya, Atmospheric and Oceanic Physics - The interannual–multidecadal variability of the temperature and depth of the upper mixed layer (UML) in the North Atlantic (NA) is analyzed on the...  相似文献