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Applications of Natural Radiation-Induced Paramagnetic Defects in Quartz to Exploration in Sedimentary Basins

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Journal of China university of Geosciences 2006年第3期17卷 258-271页

作者：潘元明 Botis S Nokhrin S department of geological sciences University of Saskatchewan

Quartz grains in contact with uranium-bearing minerals or fluids are characterized by natural radiation-induced paramagnetic defects （e. g. , oxygen vacancy centers, silicon vacancy centers, and peroxy radicals）, which are amenable to study by electron paramagnetic resonance （EPR） spectroscopy. These natural radiation-induced paramagnetic defects, except for the oxygen vacancy centers, in quartz are concentrated in narrow bands penetrated by α particles：（1） in halos around U- and Th-bearing mineral inclusions and （2） in outer rims or along fractures. The second type of occurrence provides information about uranium mineralization or remobilization （i. e. , sources of uranium, timing of mineralization or remobilization, pathways of uranium-bearing fluids）. It can also be used to evaluate sedimentary basins for potential of uranium mineralization. In particular, the peroxy radicals are stable up to 800℃ and, therefore, are useful for evaluating metasedimentary rocks （e. g. , Paleoproterozoic metasedimentary sequences in the central zone of the North China craton）. EPR study of the Changcheng Series can focus on quartz from the sediment-basement unconformity and faults to determine the presence and types of natural radiation-induced paramagnetic defects, with which to identify and prioritize uranium anomalies. Other potential applications of natural radiation-induced paramagnetic defects in quartz include uranium-bearing hydrocarbon deposits in sedimentary basins. For example, the Junggar, Ordos, and Tarim basins in northwestern China all contain important oil and natural gas fields and are well known for elevated uranium concentrations, including economic sandstone-hosted uranium deposits. Therefore, systematic studies on the distribution of natural radiation-induced paramagnetic defects in quartz from host sedimentary sequences are expected to provide information about the migration of oil and natural gas in those basins.

关键词： quartz natural radiation-induced paramagnetic defects EPR spectroscopy uranium deposits hydrocarbon resources Chinese sedimentary basins.

The Dynamics of Barotropic Vortex Merging

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Advances in Atmospheric sciences 2016年第8期33卷 987-995页

作者： Chanh KIEU department of geological sciences Indiana University

The merging of multiple vortices is a fundamental process of the dynamics of Earth＇s atmosphere and oceans. In this study, the interaction of like-signed vortices is analytically and numerically examined in a framework of two-dimensional inviscid barotropic flows. It is shown that barotropic vortex interaction turns out to be more intricate than simple merging scenarios often assumed in previous studies. Some particular configurations exist in which the vortex merging process is never complete despite strong interaction of like-signed vortices, regardless of the strengths or distances between the *** the conditions for a complete vortex merging process introduced in this study appear to be too strict for most practical applications, this study suggests that careful criteria for vortex mergers should be properly defined when simulating the interaction of vortices, because the merging may not always result in a final enhanced circulation at the end of the interaction,as usually assumed in the literature.

关键词： barotropic vortex vortex merger vortex dynamics binary vortex interaction

Overprint of neotectonism along the course of River Chel,North Bengal,India

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Journal of Palaeogeography 2016年第3期5卷 221-240页

作者： Sunipa Mandal Subir Sarkar department of geological sciences Jadavpur University

This paper aims to unveit neotectonic imprints in topography, drainage and sediments in the 46.25 km tong course of the River Chet from its source down to its attuvial fan at the base of the Himatayan Mountain Front in the Darjeeting-Jatpaiguri districts of India. A semi-circutar ridge detimits its primary catchment. Within confinement of this watershed basin the drainage pattern is composite being convergent atong the periphery and divergent on a butte inside. AtE these geomorphic neotectonic imprints are accom- panied by ramp and fiat structures and spectacutar mytonitization of rocks. High hypsometric index and convex shape of the hypsometric curve derived from the centrat near-straight course of the river between the primary catchment and the Main Frontat Thrust （MFT） atso reftects tectonic youthfutness of the river course. It is wett manifested atso in widety variabte stream index and stream gradient index ratios （SL/K） often exceeding 2. In response to neotectonism, this river course as a whore shifted westward between 1962 and 2007. Maximum reduction of the stream gradient on top of the MFT is etoquent enough about recent uptift of the thrust ridge. The high average stope gradient of canyon watt about 45.68° is wett consistent with this uptift. Very tow channet-width/vaUey-height ratio along the river further corroborates the uptift. The attuviat fan system of the River Chet is comprised of five morphogenetic fans stacked one above another with a tendency to shrink and shift progressively upstope. They differ from each other in terms of titt, axiat orientation, primary depositionat surface gradient and convexity in transverse section and thus present a writ of ongoing tectonism. Progressive upward increase in the share of distat crystattine rocks in ctast composition within attuviat fan package is a dear proxy for southerty advancement of the MFT. Concomitant increase in maximum ctast size is in good agreement with sediment source uptift. Art the five fans

关键词： Uptift of Main Frontat Thrust Neotectonism Hypsometric index Stream-sradient index,Atluviat fan system evotution Fan attributes Ctast size and composition

Isotope Geochemistry of Volcanic Rocks from the Barton Peninsula,King George Island,Antarctica

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Journal of Earth Science 2011年第1期22卷 40-51页

作者： Jeong Hwang 郑祥身 Edward M Ripley Jong-Ik Lee Dongbok Shin department of geological Engineering Daejeon University Institute of Geology and Geophysics Chinese Academy of Sciences department of geological sciences Indiana University Korea Polar Research Institute department of geological sciences Kongju University

C, O, H, S and Sr isotopes were investigated to characterize the isotopic composition of the Paleocene-Eocene volcanic rocks in Barton Peninsula, King George Island, Antarctica. The analyzed samples of volcanic rocks cover a range from basalt to andesite. The δ 13C and 61SO values of calcite in volcanic rocks range from -7.5‰ to -3.2‰ and 0.4‰ to 5.1‰, respectively. The homogenous δ 13C cal and depleted δ18 Ccal values relative to primary magmatic values reflect the effect of high temperature alteration of volcanic rocks. The δ18 O of volcanic rocks ranges from -1.1‰ to 7.2‰, and the majority of values are significantly lower than those of primary magmatic values. The low δ18 O WR values are compatible with high temperature alteration. The initial values of 87Sr/86Sr of volcanic rocks span a narrow range from 0.703 312 to 0.703 504 which belong to the present mid-oceanic ridge basalt. The values of 87Sr/86Sr of volcanics in the Barton Peninsula are similar to those determined in the Fildes Peninsula, King George Island. The δD WR and H2O contents of volcanic rocks range from -74‰ to -66‰ and 0.67 wt.% to 2.74 wt.%, respectively. The higher δD WR and H2O wt.% of volcanic rocks relative to fresh basalts also result from high temperature alteration. Sulfur isotope compositions of the volcanic rocks range from -12.5‰ to -7.0‰; these values may represent fractionation accompanying partial oxidation of magmatic S or incorporation of some bacteriogenic sulfide. The low S contents and negative correlation with C and H2O reflect the formation of calcite and breakdown of sulfide as a result of high temperature water-rock interaction.

关键词： isotope volcanic rock high temperature alteration Antarctica.

Landslide Susceptibility Mapping Using RBFN-Based Ensemble Machine Learning Models

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Computer Modeling in Engineering & sciences 2025年第1期142卷 467-500页

作者： Landslide Susceptibility Mapping Using RBFN-Based Ensemble Machine Learning Models Duc-Dam Nguyen Nguyen Viet Tiep Quynh-Anh Thi Bui Hiep Van Le Indra Prakash Romulus Costache Manish Pandey Binh Thai Pham Faculty of Civil Engineering University of Transport TechnologyThanh XuanHa Noi100000Vietnam Faculty of Hydraulic Engineering Hanoi University of Civil EngineeringHa Noi100000Vietnam DDG(R)geological Survey of India Gandhinagar382010India Research Institute of the university of Bucharest Bucharest050663Romania National Institute of Hydrology and Water Management Bucharest013686Romania department of Civil Engineering Transilvania University of BrasovBrasov500152Romania Danube Delta National Institute for Research and Development Tulcea820112Romania Marwadi university Research Center(MURC) Marwadi UniversityRajkotGujaratBharat360003India department of Civil Engineering Faculty of Engineering&TechnologyMarwadi UniversityRajkotGujaratBharat360003India

This study was aimed to prepare landslide susceptibility maps for the Pithoragarh district in Uttarakhand,India,using advanced ensemble models that combined Radial Basis Function Networks(RBFN)with three ensemble learning techniques:DAGGING(DG),MULTIBOOST(MB),and ADABOOST(AB).This combination resulted in three distinct ensemble models:DG-RBFN,MB-RBFN,and ***,a traditional weighted method,Information Value(IV),and a benchmark machine learning(ML)model,Multilayer Perceptron Neural Network(MLP),were employed for comparison and *** models were developed using ten landslide conditioning factors,which included slope,aspect,elevation,curvature,land cover,geomorphology,overburden depth,lithology,distance to rivers and distance to *** factors were instrumental in predicting the output variable,which was the probability of landslide *** analysis of the models’performance indicated that the DG-RBFN model,with an Area Under ROC Curve(AUC)of 0.931,outperformed the other *** AB-RBFN model achieved an AUC of 0.929,the MB-RBFN model had an AUC of 0.913,and the MLP model recorded an AUC of *** results suggest that the advanced ensemble ML model DG-RBFN was more accurate than traditional statistical model,single MLP model,and other ensemble models in preparing trustworthy landslide susceptibility maps,thereby enhancing land use planning and decision-making.

关键词： Landslide susceptibility map spatial analysis ensemble modelling information values(IV)

Review of Late Jurassic-early Miocene sedimentation and plate-tectonic evolution of northern California:illuminating example of an accretionary margin

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Chinese Journal Of Geochemistry 2015年第2期34卷 123-142页

作者： W.G.Ernst department of geological & Environmental sciences Stanford University

Production of voluminous igneous arc rocks,high-pressure/low-temperature(HP/LT) metamafic rocks,westward relative migration of the Klamath Mountains province,and U-Pb ages of deposition,sediment sources,and spatial locations of Jurassic and younger,detrital zirconbearing clastic rocks constrain geologic development of the northern California continental edge as follows:(1) At~ 175 Ma,transpressive plate underflow began to generate an Andean-type Klamath-Sierran arc along the margin.(2)Oceanic crustal rocks were metamorphosed under HP/LT conditions in an inboard,east-inclined subduction zone from~ 170-155 *** for the Red Ant blueschists,such Ethologies remained stored at depth;most HP/LT mafic tectonic blocks returned surfaceward only during mid- and Late Cretaceous time,chiefly entrained in circulating,buoyant Franciscan mud-matrix melange.(3) By ~ 165 Ma and continuing to ~ 150-140 Ma,erosion supplied volcanogenic debris to proximal Mariposa-Galice ± Myrtle overlap strata.(4) At ~ 140,immediately prior to the onset of paired Franciscan and Great Valley Group(GVG) +Hornbrook deposition,the Klamath salient was deformed and displaced ~ 100-150 km westward relative to the Sierran arc,stranding pre-existing oceanic crust on the south as the Coast Range Ophiolite(CRO).(5) After the end-ofJurassic seaward step-out of the Farallon-North American convergent plate junction,terrigineous debris began to be deposited in the outboard Franciscan trench and intervening Great Valley forearc.(6) Voluminous sedimentation and accretion of Franciscan Eastern + Central belts and GVG detritus took place during paroxysmal igneous activity and rapid,nearly orthogonal plate convergence at^125-80 Ma.(7) Sierran arc volcanism-plutonism ceased by^80 Ma in northern California,signaling a transition to shallow,nearly subhorizontal eastward plate underflow attending Laramide orogeny far to the east.(8) Presently exposed Paleogenelower Miocene Franciscan Coastal Belt sedimentary strata were

关键词：板块构造早中新世加利福尼亚州晚侏罗世增生保证金 U-Pb年龄地层沉积

Effects of confinement on rock mass modulus:A synthetic rock mass modelling(SRM) study

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Journal of Rock Mechanics and Geotechnical Engineering 2018年第3期10卷 436-456页

作者： I.Vazaios K.Farahmand N.Vlachopoulos M.S.Diederichs department of geological sciences and geological Engineering Queen's UniversityKingston Ontario

The main objective of this paper is to examine the influence of the applied confining stress on the rock mass modulus of moderately jointed rocks（well interlocked undisturbed rock mass with blocks formed by three or less intersecting joints）. A synthetic rock mass modelling（SRM） approach is employed to determine the mechanical properties of the rock mass. In this approach, the intact body of rock is represented by the discrete element method（DEM）-Voronoi grains with the ability of simulating the initiation and propagation of microcracks within the intact part of the model. The geometry of the preexisting joints is generated by employing discrete fracture network（DFN） modelling based on field joint data collected from the Brockville Tunnel using LiDAR scanning. The geometrical characteristics of the simulated joints at a representative sample size are first validated against the field data, and then used to measure the rock quality designation（RQD）, joint spacing, areal fracture intensity（P21）, and block volumes. These geometrical quantities are used to quantitatively determine a representative range of the geological strength index（GSI）. The results show that estimating the GSI using the RQD tends to make a closer estimate of the degree of blockiness that leads to GSI values corresponding to those obtained from direct visual observations of the rock mass conditions in the field. The use of joint spacing and block volume in order to quantify the GSI value range for the studied rock mass suggests a lower range compared to that evaluated in situ. Based on numerical modelling results and laboratory data of rock testing reported in the literature, a semi-empirical equation is proposed that relates the rock mass modulus to confinement as a function of the areal fracture intensity and joint stiffness.

关键词： Synthetic rock mass modelling (SRM) Discrete fracture network (DFN) Rock mass modulus geological strength index (GSI) Confinement

The Siberian Traps and the End-Permian mass extinction:a critical review

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Chinese Science Bulletin 2009年第1期54卷 20-37页

作者： Andy SAUNDERS Marc REICHOW department of geological sciences University of Leicester

The association between the Siberian Traps,the largest continental flood basalt province,and the largest-known mass extinction event at the end of the Permian period,has been strengthened by re-cently-published high-precision 40Ar/39Ar dates from widespread localities across the Siberian prov-ince[1]. We argue that the impact of the volcanism was amplified by the prevailing late Permian envi-ronmental conditions―in particular,the hothouse climate,with sluggish oceanic circulation,that was leading to widespread oceanic anoxia. Volcanism released large masses of sulphate aerosols and carbon dioxide,the former triggering short-duration volcanic winters,the latter leading to long-term warming. Whilst the mass of CO2 released from individual eruptions was small compared with the total mass of carbon in the atmosphere-ocean system,the long ‘mean lifetime’ of atmospheric CO2,com-pared with the eruption flux and duration,meant that significant accumulation could occur over periods of 105 years. Compromise of the carbon sequestration systems (by curtailment of photosynthesis,de-struction of biomass,and warming and acidification of the oceans) probably led to rapid atmospheric CO2 build-up,warming,and shallow-water anoxia,leading ultimately to mass extinction.

关键词：西伯利亚二叠纪温室气候海洋缺氧 CO2 SO2

Continental accretion and incremental deformation in the thermochronologic evolution of the Lesser Caucasus

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Geoscience Frontiers 2019年第6期10卷 2189-2202页

作者： William Cavazza Irene Albino Ghazar Galoyan Massimiliano Zattin Silvia Cattò department of Biological Geologicaland Environmental SciencesUniversity of BolognaItaly Institute of geological sciences National Academy of SciencesYerevanArmenia department of Geosciences University of PaduaItaly

Apatite fission-track analysis and thermochronologic statistical modeling of Precambrian-Oligocenc plutonic and metamorphic rocks from the Lesser Caucasus resolve two discrete cooling *** occurred during incremental crustal shortening due to obduction and continental accretion along the margins of the northern branch of the Neotethys.(1)The thermochronometric record of a Late Cretaceous(Turonian-Maastrichtian)cooling/exhumation event,coeval to widespread ophiolite obduction,is still present only in a relatively small area of the upper plate of the Amasia-Sevan-Akera(ASA)suture zone,*** suture marking the final closure of the northern Neotethys during the *** area has not been affected by significant later exhumation.(2)Rapid cooling/exhumation occurred in the Early-Middle Miocene in both the lower and upper plates of the ASA suture zone,obscuring previous thermochronologic signatures over most of the study *** contractional reactivation of the ASA suture zone occurred contemporaneously with the main phase of shortening and exhumation along the Bitlis suture zone marking the closure of the southern branch of the Neotethys and the ensuing ArabiaEurasia *** collisional stress from the Bitlis suture zone was transmitted northward across the Anatolian hinterland,which was left relatively undeformed,and focused along preexisting structural discontinuities such as the eastern Pontides and the ASA suture zone.

关键词： Lesser Caucasus Low-temperature thermochronology Apatite fission-track analysis Structural reactivation Far-field tectonics