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Geologic field evidence for non-lithostatic overpressure recorded in the North American Cordillera hinterland,northeast nevada

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Geoscience Frontiers 2022年第2期13卷 471-490页

作者： Andrew V.Zuza Drew A.Levy Suzanne R.Mulligan nevada bureau of mines and geology University of NevadaRenoNV 89557USA Department of Geoscience University of NevadaLas VegasNV 89154USA

There is a long-standing discrepancy for numerous North American Cordillera metamorphic core complexes between geobarometric pressures recorded in the exhumed rocks and their apparent burial depths based on palinspastic reconstructions from geologic field *** particular,metamorphic core complexes in eastern nevada are comprised of well-documented~12-15 km thick Neoproterozoic-Paleozoic stratigraphy of Laurentia’s western passive margin,which allows for critical characterization of field *** this contribution we focus on the Ruby Mountain-East Humboldt Range-Wood Hills-Pequop Mountains(REWP)metamorphic core complex of northeast nevada to explore reported peak pressure estimates versus geologic field relationships that appear to prohibit deep *** high pressure estimates of 6-8 kbar(23-30 km depth,if lithostatic)from the lower section of the Neoproterozoic-Paleozoic passive margin sequence require burial and or repetition of the passive margin sequence by 2-3×stratigraphic *** observations from the least migmatized and/or mylonitized parts of this complex,including field observations,a transect of peak-temperature(T_(p))estimates,and critical evaluation of proposed thickening/burial mechanisms cannot account for such deep *** Neoproterozoic-Cambrian(€)rocks part of a continuous stratigraphic section that transitions~8 km upsection to unmetamorphosed Permian strata that were not buried,we obtained new quartz-in-garnet barometry via Raman analysis that suggest pressures of~7 kbar(~26 km).A T_(p)traverse starting at the same basal€rocks reveals a smooth but hot geothermal gradient of≥40℃/km that is inconsistent with deep *** observation is clearly at odds with thermal gradients implied by high P-T estimates that are all≤25℃/*** similar discrepancies between pressure estimates and field observations have been discussed for the northern Snake Range metamorphic core complex,~200 km to the *** argue that

关键词： Non-lithostatic pressure Tectonic overpressure North American Cordillera Ruby Mountain-East Humboldt Range Peak temperature Geothermal gradient

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The Trace Element Distribution Patterns of Ediacaran-Early Cambrian Black Shales and the Origin of Selenium in the Guangning Area, Western Guangdong Province, South China

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Acta Geologica Sinica(English Edition) 2017年第6期91卷 1978-1991页

作者： TIAN Xinglei LUO Kunli Andrew V.ZUZA Institute of Geographic Sciences and Natural Resources Research Chinese Academy of Sciences University of the Chinese Academy of Sciences nevada bureau of mines and geology University of Nevada

The Ediacaran and early Cambrian black shales are widespread across the South China Craton （Yangtze and Cathaysia blocks）. However, the trace element distribution patterns of the Ediacaran and early Cambrian black shales in the Cathaysia Block are still unclear. In this study, thirty- four black shale samples in the Lechangxia Group （Ediacaran） and thirteen black shale samples in the lower Bacun Group （early Cambrian） from Guangning area, western Guangdong Province, South China, were analyzed for major and trace elements concentrations. Compared to the upper continental crust, the Ediacaran black shales exhibit strongly enriched Se, Ga, and As with enrichment factor values （EF） higher than 10, significantly enrichedBi and Rb （10〉EF〉5）, weakly enriched Mo, Ba, Cs, V, In, Be, TI, and Th （5〉EF〉2）, normal U, Cr, Cd, Sc, Pb, Cu, and Li （2〉EF〉0.5）, and depleted Ni, Zn, Sr, and Co. Early Cambrian black shales display strongly enriched Se, Ga, and As, significantly enriched Ba, Bi, and Rb, weakly enriched Mo, Cs, Cd, V, U, Be, In, and TI, normal Sc, Th, Cr, Li, Cu, Ni, and Pb and depleted Co, Zn, and Sr. Moreover, Se is the most enriched trace element in the Ediacaran and early Cambrian black shales： concentrations vary from 0.25 to 30.09 ppm and 0.54 to 5.01 ppm, and averaging 4.84 and 1.72 ppm, with average EF values of 96.87 and 34.32, for the Ediacaran and early Cambrian shales respectively. The average concentration of Se in the Ediacaran black shales is 2.8 times higher than that of early Cambrian black shales. Se contents in the Ediacaran and early Cambrian black shales exhibit significant variation （P = 0.03）. Provenance analysis showed that Se contents of both the Ediacaran and early Cambrian black shales were without detrital provenance and volcanoclastic sources, hut of hydrothermal origin. The deep sources of Se and the presence of pyrite may explain the higher Se contents in the Ediacaran black shales. Similar with the Se-rich characteristics of the contemporan

关键词： black shale selenium Ediacaran and early Cambrian Guangning area Cathaysia block

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Sedimentary Paleoenvironment of the Eastern Hexi Corridor, NW China: Constraints from Chert Geochemistry and Sedimentary Analysis of Early Paleozoic Strata

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Acta Geologica Sinica(English Edition) 2020年第4期94卷 1223-1237页

作者： ZHANG Yiping CHEN Xuanhua AVZUZA ZHANG Beihang ZHAO Heng Chinese Academy of Geological Sciences Beijing 100037China nevada bureau of mines and geology University of NevadaReno89557USA Institute of geology Chinese Academy of Geological SciencesBeijing 100037China

The eastern Hexi Corridor, northwest China, is located at the tectonic junction of the Alxa Block, the North China Craton, and the Qinling-Qilian Orogen. The early Paleozoic Xiangshan Group record critical information regarding paleoenvironment, paleoclimate and paleotectonic setting, from which we here present a focused study on the chert beds within the Xiangshan Group. Through field mapping, microstructural observation, whole-rock geochemistry analyses and detrital zircon dating, we suggest that the Xiangshan Group chert was deposited along a passive continental margin, formed primarily through biological activity with minor hydrothermal influence and terrestrial input. The characteristics of the chert support a low latitude sedimentary paleoenvironmental origin, and reveal the fact that the Alxa Block was separated from the North China craton, while emerged some paleogeographic affinity with the Qilian region in the Middle-Late Cambrian.

关键词： geochemistry sedimentary paleoenvironment Early Paleozoic Xiangshan Group chert Hexi Corridor

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Mineralization of a Proterozoic Sulfide Black Smoker Chimney and Thermophilous Microorganisms in Eastern Hebei,China

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Acta Geologica Sinica(English Edition) 2008年第4期82卷 858-863页

作者： XIA Xuehui LIAN Wei YUAN Congjian YAN Fei YUAN Jiazhong geology Research Institute of China Chemical geology and mines General bureau Zhuozhou Hebei 072754 China China Chemical geology and mines General bureau Beijing 100101 China

A sulfide black smoker chimney exists in the Gaobanhe seabed exhalation massive sulfide deposit in the Xingiong-Kuancheng secondary fault basin of the Proterozoic Yaniiao rift trough in Hebei Province, taking the shape of mounds, individually about 2-3 cm high. Abundant fossils of thermophilous bacteria and algae in perfect preservation are found in the ore surrounding the black smoker chimney. Scanning electron microscopy （SEM） and molecular biomarker studies on the microorganismai ore fabric show that the microorganism in the sulfide ore is in fact a sedimentary product of probiotic bacteria and algae. In the special food chain based on black smoker chimney at ancient seabed- thermophilous bacteria, the thermophilous bacteria and algae reproduce in large quantity. Intermittently erupting of fluid from the chimney creats conditions for formation of sulfide deposit. In the process of exhalation action of hot fluid, thermophilous bacteria and algae grow and reproduce around the sulfide black smoker chimney, absorbing mineralizing substances brought by the fluid. Massive sulfide deposits are formed in this process of absorption of seabed black smoker chimney exhalation-mineralizing fluid pulsation-thermophilous microorganism.

关键词： sulfide black smoker chimney thermophilous microorganisms mineralization,Mesoproterozoic

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A Comparison of Carlin-type Gold Deposits：Guizhou Province,Golden Triangle,Southwest China,and Northern nevada,USA

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地学前缘 2013年第1期20卷 1-18页

作者： Jean S.CLlNE John L.MUNTEAN Xuexiang GU Yong XIA University of nevada Las Vegas nevada BareaH of mines and geology and University of nevada Reno School of Earth Sciences and Resources China University of Geosiences(Beijing) State Key Laboratory of Ore Deposit Geochemistry.Institute of Geochemistry.Chinese Academy of Sciemces

Several Au deposits in Guizhou Province,southwest China,described as being similar to the highly productive Carlin-type gold deposits in northern ***,were examined to identify similarities and differences between the two *** were collected along transects from lowto high-grade rock,where possible,and fram stockpiles at the Shuiyindong,Zimudang,Taipingdong,Yata and Jinfeng(formerly Lannigou)*** used to examine ore and alteration minerals included hand-sample description:reflectance spectroscopy using an ASD Terraspec spectrometer;analyses of hand samples by carbonate staining with Alizaren red and potassium ferricyanide;transmitted and reflected light petrography;chemical analyses,mineral identification,and imaging using a ***-5610 scanning electron microscope:and quantitative chemical analyses using a JEOL JXA-8900 electron probe *** analyses of hand samples for 52 elements were done by ALS *** indicate both similarities and differences between the two *** districts have similar geologic *** deposits at both locations appear to have formed as a result of similar tectonic *** the district in southwest China lacks evidence of eoeval felsic igneous activity;however,the ore-stage minerals and the fluids that produced the minerals and deposits have some significant *** nevada deposits were dominated by fluid-rock reaction in which host rock Fe was sulfidized to form Au-bearing *** ore fluids sulfidized host rock Fe in the Cuizhou *** timing of Fe metasomatism is unknown,so whether the deposits formed in response to sulfidation or pyritization is ***-rock reaction between an acidic,aqueous fluid and highly reactive calcareous rocks in nevada caused extensive decarbonatization of host rocks,jasperoid replacemerit of carbonate minerals,and alteration of silty rock components to illite and *** Guizhou,CO2-bearing ore flu

关键词：地质地理学地质构造气藏

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Investigation of factors influencing roof stability at a Western *** coal mine

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International Journal of Mining Science and Technology 2019年第1期29卷 139-143页

作者： Meriel Young Gabriel Walton Elizabeth Holley Department.geology&Geol.Engineering Colorado School of Mines Department Mining Engineering Colorado School of Mines

The coal mine roof rating(CMRR) was developed to bridge the gap between geological variation in underground coal mines and engineering design. The CMRR accounts for the compressive strength of the immediate roof, the shear strength and intensity of any discontinuities present, and the moisture sensitivity of the immediate roof. The CMRR has been widely used and validated in Eastern US coal mines, but it has seen limited application in the Western US. This study focuses on roof behavior at a Western coal mine(Mine A). Mine A shows significant lateral geological variation, along with localized faulting and a laterally extensive sandstone channel network. The CMRR is not used to predict roof instability at the mine. It is, therefore, hypothesized that there are other factors that are correlated with roof instability in underground coal mines that could potentially also be considered in conjunction with the *** hypothesis was tested by collecting 30 CMRR measurements at Mine A. At each measurement location, a binary record of the roof condition(stable or unstable) was made, and other parameters such as depth of cover, presence of faulting, and sandstone channels were also recorded. ANOVA tests showed that the CMRR values and the roof conditions were not strongly correlated, indicating that the CMRR input criteria are not fully predictive of roof stability at this mine. The CMRR values showed statistically significant correlations(p less than 0.05) with faulting as well as with location at an intersection. For areas that had previously experienced roof fall but were currently stable, faulting was correlated with roof condition(p less than 0.05) only when the condition was classified as unstable.

关键词： Coal mine roof stability CMRR Western U.S.coal Case study

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Reflectance spectral characterization and mineralogy of acid sulphate soil in subsurface using hypcrspectral data

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International Journal of Sediment Research 2014年第2期29卷 149-158页

作者： Xian-Zhong SHI Mehrooz ASPANDIAR David OLDMEADOW Department of Applied geology Western Australian School of MinesCurtin University

Acid sulphate soil（ASS） is a kind of soil which is harmful to the *** is hard to efficiently assess efficiently in the subsurface,although it is detectable on the surface by remote *** paper aims to explore a new way to rapidly assess ASS in the subsurface by introducing a proximal hyperspectral instrument,namely the HyloggerTMsystem which can rapidly scan soil cores and provide high resolution hyperspectral *** minerals in ASS,which usually act as indicators of the severity of ASS,such as iron oxides,hydroxides,and sulphates,as well as some clay minerals,such as kaolinite,have diagnostic spectral absorption features in the reflectance spectral range（400-2500 nm）.Soil cores were collected from a study area and hyperspectral data were acquired by *** main minerals related to ASS were characterized spectrally,and were subsequently identified and mapped in the soil cores based on their reflectance spectral *** X-ray diffraction（XRD） and scanning electron microscope（SEM） were also applied to verify the results of the mineral *** main results of this study include the spectral characterisation of ASS and its main compositional minerals,as well as the distribution of these relevant minerals in different depth of cores.

关键词： Acid sulphate soil Hyperspectral sensing HyloggerTM Subsurface

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Understanding roof deformation mechanics and parametric sensitivities of coal mine entries using the discrete element method

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International Journal of Mining Science and Technology 2020年第1期30卷 123-129页

作者： Rami Abousleiman Gabriel Walton Sankhaneel Sinha Department of geology and Geological Engineering Colorado School of MinesGoldenCO 80218USA

Although conventional coal mine designs are conservative regarding pillar strength,local failures such as roof-falls and pillar bursts still affect mine safety and *** studies have identified that discontinuous,layered roof materials have some self-supporting *** research is a preliminary step towards understanding these mechanics in coal-measure *** others have considered broad conceptual models and simplified analogs for mine roof behavior,this study presents a unique numerical model that more completely represents in-situ roof *** discrete element method(DEM)is utilized to conduct a parametric analysis considering a range of in-situ stress ratios,material properties,and joint networks to determine the parameters controlling the stability of single-entries modeled in *** results are compared to empirical observations of roof-support effectiveness(ARBS)in the context of the coal mine roof rating(CMRR)*** such as immediate roof displacement,overall stability,and statistical relationships between model parameters and outcomes are presented *** practical applications of this line of research include:(1)roof-support optimization for a range of coal-measure rocks,(2)establishment of a relationship between roof stability and pillar stress,and(3)determination of which parameters are most critical to roof stability and therefore require concentrated evaluation.

关键词： Numerical modeling Discrete element method Coal mine roof rating Analysis of roof bolt systems Sensitivity analysis Strain softening ubiquitous joints Discrete fracture network

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Geochemistry of a paleosol horizon at the base of the Sausar Group,central India： Implications on atmospheric conditions at the Archeane Paleoproterozoic boundary

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Geoscience Frontiers 2016年第5期7卷 759-773页

作者： Sarada P.Mohanty Sangitsarita Nanda Department of Applied geology. Indian School of mines Dhanbad 826004 India

A paleosol horizon is described from the contact of the Sausar Group（w2400 Ma） and its basement（Tirodi Gneiss; 〉2500 Ma） in Central India. Physical evidence of pedogenesis is marked by the development of stress corrosion cracks, soil peds, corestone weathering and nodular rocks. XRD and SEM-EDX data indicate the presence of siderite, ankerite, uraninite, chlorite, alumino-silicate minerals, ilmenite,rutile and magnetite, in addition to quartz, feldspar and mica. The chemical index of alteration, the plagioclase index of alteration, and the chemical index of weathering show an increasing trend from parent rock to the paleosol and indicate a moderate trend of weathering. The A-CN-K plot indicates loss of feldspars, enrichment in Al2O3 and formation of illite. Different major element ratios indicate baseloss through hydrolysis, clay formation, leaching of some elements, and more precipitation with good surface drainage. The paleosol is depleted in HREE in comparison to the parent rock indicating high fluid-rock interaction during weathering. The paleosol samples show flat Ce and Eu anomalies, low SREE, and high（La/Yb）N, indicative of a reducing environment of formation. Reducing condition can also be inferred from the concentration of elements such as V, Co, Cu, Pb, and Zn in the paleosol profile. Although enriched in Fe and Mg, the overall geochemical patterns of the paleosol indicate oxygen deficient conditions in the atmosphere and development by weathering and leaching processes associated with high precipitation and good surface drainage at the time of development of this paleosol during the Archeane Paleoproterozoic transition.

关键词： Paleosol Anoxic weathering Great oxidation event Paleoproterozoic Sausar Group

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Integration of three-dimensional continuum model and two-dimensional bonded block model for studying the damage process in a granite pillar at the Creighton Mine,Sudbury,Canada

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Journal of Rock Mechanics and Geotechnical Engineering 2021年第2期13卷 275-288页

作者： Sankhaneel Sinha Gabriel Walton geology and Geological Engineering Colorado School of MinesGoldenCO80401USA

Bonded blockmodel(BBM)has shownpotential in replicating rockmass behavior aswell as the rockesupport interactionmechanism,but their practical application is limited totwo dimensions due to the high associated computational *** allow for the use of BBM in simulating three-dimensional(3D)problems,this study proposes an integrated 3D continuumetwo-dimensional(2D)discontinuum approach,in context of rock pillars.A cross-section of a granite pillar was simulated using a BBM with a load path from a calibrated mine-scale FLAC^(3D)*** support as employed in the mine was also incorporated in different stages during the *** was calibrated by varying the input parameters until the displacements at six locations within the pillarmatchedthosemeasuredby amulti-point borehole extensometer(MPBX)inthe *** calibratedmodel was subsequently used to understand how the support and load path influenced the damage evolution in the *** shear component of the load pathwas found to have amajor effect on the severity and extent of the damaged *** the support density was increased in the model,the lateral displacements along the pillar walls were significantly suppressed in a somewhat unpredictable *** explained by the interaction between the supports and the damaged regions at the corners,which ultimately modified the stresses along the pillar *** amount of displacement reduction obtained by increasing the support density illustrates the potential of BBMto be used as a support design tool.

关键词： Bonded block model(BBM) Rock pillars Supports Continuum-discontinuum integration

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