The purpose of this study is to investigate the effect of Panoramic Virtual Reality(PVR)applied to online earth science classes on students’learning flow.To this end,a PVR learning material was made with a geology le...The purpose of this study is to investigate the effect of Panoramic Virtual Reality(PVR)applied to online earth science classes on students’learning flow.To this end,a PVR learning material was made with a geology learning site,which contains a core geologic concept contained in a high school curriculum in Korea.To this end,a PVR learning material was made at a geologic field site to provide an interactive and engaging way for students to grasp core geologic concepts according to the high school curriculum in Korea.The PVR was applied to online earth science classes with 45 high school students.In order to examine the effect of the PVR on students'learning flow,pre-post learning flow test papers were used,then matchedsample t-test analysis and students'responses were analyzed.The result shows online classes with PVR have positive effects on learning flow(p<0.05).And it was possible for the students to observe three-dimensional geologic structures effectively in online classes as in offline field trips.And the students'responded with positive feedbacks.These suggest that PVR in online classes can be used as an effective teaching method,which can improve students'flow and eventually understanding subjects.展开更多
The green energy transition relies heavily on critical metals,such as rare earth elements(REEs).However,their reserves are primarily focused in a few countries,such as China,which accounts for approximately 70%of glob...The green energy transition relies heavily on critical metals,such as rare earth elements(REEs).However,their reserves are primarily focused in a few countries,such as China,which accounts for approximately 70%of global production.Hence,several countries are currently looking for alternative resources for REEs.Alternative REE resources in the supply chain include recycling of e-waste,industrial waste like red mud and phosphogypsum,coal ash,mine tailings,ocean floor sediments,and even certain types of sedimentary deposits like phosphorites where REEs are present in lower concentrations but at larger volumes compared to primary ore deposits which are becoming targets by REEs industry.Currently,several studies are going on the development of eco-friendly REEs extraction technologies from phosphorite deposits.Consequently,advanced data analysis tools,such as Machine Learning(ML),are becoming increasingly important in mineral prospectivity and are rapidly gaining traction in the earth sciences.Phosphorite deposits are mainly used to manufacture fertilizers as these rocks are known for their significant phosphorus content.Moreover,these formations are considered a prospective resource of REEs.The different types of phosphorite deposits such as continental,seamount,and ore deposits worldwide reported concentrations of∑REE upto 18,000µg/g.Due to the augmented claim of REEs for various ultra-modern,and green technology applications that are required to switch over to a carbon-neutral environment,these phosphorite deposits have become an important target mostly because of their relatively higher content of REEs especially heavy rare earth elements(HREE).For example,Mississippian phosphorites reported ∑ HREE 7,000µg/g.To have a comprehensive understanding of the REEs potential of these phosphorite deposits which also include several Chinese phosphorite deposits,this study is undertaken to review the phosphorite deposits in the world and their REEs potential,in addition to some of the associated aspects such as applications and formation mechanisms for different types of phosphorite deposits such as igneous phosphate deposits,sedimentary phosphorite deposits,marine phosphorite deposits,cave phosphate deposits,and insular guano deposits.Other important aspects include their occurrences,types,geochemical characteristics,the REEs enrichment mechanisms,and various recovery methods adopted to recover REEs from different phosphorite deposits.The present review paper concludes that the recent studies highlight the global potential of phosphorite deposits to satisfy the increasing demand for REEs.Extracting REEs from phosphorite presents no significant technological or environmental difficulties,as long as radioactive elements are eliminated.In India,more comprehensive geological surveys,along with the advancement of new methods and evaluations,are required to locate phosphorite deposits with high concentrations of REEs.展开更多
The 3^(rd) International Earth Science Olympiad(www.ieso2009.tw/home/home.html)was organized by the National Taiwan Normal University at Taipei,Taiwan.Fifty students from 14 countries participated in the 3^(rd) IESO.F...The 3^(rd) International Earth Science Olympiad(www.ieso2009.tw/home/home.html)was organized by the National Taiwan Normal University at Taipei,Taiwan.Fifty students from 14 countries participated in the 3^(rd) IESO.Four other countries sent Observers.展开更多
This paper reviewed the level of Geoscience education in Ghana and offers recommendations for improvement.The review showed that Geoscience education in Ghana is inadequate and Geoscience literacy and awareness in the...This paper reviewed the level of Geoscience education in Ghana and offers recommendations for improvement.The review showed that Geoscience education in Ghana is inadequate and Geoscience literacy and awareness in the public are weak.Currently,the level of Geoscience content in the formal educational curricula of Basic and Senior High schools as well as colleges of education in Ghana is very low.In addition,out of 129 universities in Ghana,only seven offer Geoscience or Geoscience-related programs.To improve the level of formal Geoscience education we recommend the following:(1)introduce geoscience degree programs in colleges of education,(2)introduce Geoscience as a subject in the Senior High School curriculum,(3)improve the Geoscience content in the Basic School curriculum,(4)Encourage more universities to offer degree programs in Geoscience.To train the next generation of Geoscientists,we recommend improvements in Geoscience degree programs in terms of(1)the curriculum,content,proficiencies,and skills,(2)the use of pedagogy and technology,and(3)the preparation of teachers to build capacity in science and core geology.To help increase Geoscience awareness and literacy in Ghana,the Geoscience workforce should team up with relevant stakeholders to promote Geoscience outreach in Ghana.展开更多
Introduction.The International Union of Geological Sciences(IUGS)is a prominent non-governmental organization dedicated to promoting and fostering the study of geological sciences internationally.Established in 1961,t...Introduction.The International Union of Geological Sciences(IUGS)is a prominent non-governmental organization dedicated to promoting and fostering the study of geological sciences internationally.Established in 1961,the IUGS is a member of the International Science Council and plays a pivotal role in setting global standards in geological sciences,facilitating international collaboration,and supporting the coordination of major global geological events and research initiatives(Cheong and Kim,2021).One of the key events organized by the IUGS is the International Geological Congress(IGC),held every four years.This congress serves as a vital forum for geologists from around the world to share their latest research findings,discuss advancements in the field,and explore new directions in geological sciences.The IGC encompasses a wide range of topics including geology,geophysics,mineralogy,paleontology,and sedimentology,among others,reflecting the diversity and interdisciplinary nature of the field(Cheong and Kim,2021).展开更多
Both fractional crystallization and fluid-melt-crystal interaction are involved in the formation of highly fractionated granites.This paper assessed those two processes using geochemistry of muscovite and tourmaline a...Both fractional crystallization and fluid-melt-crystal interaction are involved in the formation of highly fractionated granites.This paper assessed those two processes using geochemistry of muscovite and tourmaline and bulkrock chemistry of multi-phase Wangxianling granitoids,South China.Compositional variations suggest the coarse-grained muscovite granite is produced from fractional crystallization of the two-mica granite whereas the fine-grained muscovite granite represents a distinct magma pulse.Progressive fractionation of quartz,feldspar and biotite leads to elevated boron and aluminum content in melt which promoted muscovite and tourmaline to crystallize,which promotes two-mica granite evolving towards tourmaline-bearing muscovite granite.Fluid-melt-crystal interaction occurred at the magmatichydrothermal transitional stage and resulted in the textural and chemical zonings of tourmaline and muscovite in finegrained muscovite granite.The rims of both tourmaline and muscovite are characterized by the enrichment of fluid mobile elements such as Li,Mn,Cs and Zn and heavierδ^(11)B values of the tourmaline rims(-15.0‰to-13.6‰)compared to cores(-15.7‰to-14.3‰).Meanwhile,significant M-type REE tetrad effects(TE_(1,3)=1.07-1.18)and low K/Rb ratios(48-52)also correspond to fluid-melt-crystal interaction.This study shows zoned muscovite and tourmaline can be excellent tracers of fractional crystallization and late-stage fluid-melt-crystal interaction in highly evolved magmatic systems.展开更多
The GPS data sourced from the permanent GPS network in the Kashmir Himalaya were utilized to quantify both vertical and horizontal deformation rates in the Kashmir Valley of the northwestern Himalaya.While lateral def...The GPS data sourced from the permanent GPS network in the Kashmir Himalaya were utilized to quantify both vertical and horizontal deformation rates in the Kashmir Valley of the northwestern Himalaya.While lateral deformation in the Kashmir basin has been previously quantified,the vertical component has not been studied yet.To quantify the vertical and horizontal deformation rates in the Kashmir Valley,we use GAMIT/GLOBK software to process the GPS data.The lateral motion data indicate that the Indian plate continues to move towards the Eurasian plate at a rate of 36-42 mm/yr,while the vertical vectors infer a transition zone across the Kashmir valley.Using ArcGIS,Iso-base and Iso-ketabase maps were generated from the GPS vertical vectors to study the vertical deformation status of the Kashmir Valley.The analysis of vertical vectors reveals a significant transition zone in the Kashmir Valley.The vertical vector data show distinct patterns:GPS stations in the northeast,south,and southeast of the Kashmir Valley exhibit uplift,while stations in the north,northwest,and southwest show subsidence.The uplift velocity increases as we move from the Srinagar station to the Kulgam station via Tral and Ashmuqam,while the subsidence rate increases as we move from the Bandipora station to Mulgam and Uri.Specifically,the highest uplift rate(5.2±0.6 mm/yr)is observed at the Kulgam station and the highest subsidence rate(-6.5±1.26 mm/yr)at the Uri station.On average,vertical subsidence of-2.81 mm/yr is recorded along the north and northwest sides of the valley,and an average uplift of 3.04 mm/yr in the south and southeast.Integrating geomorphological observations with GPS measurements,we infer the presence of an active normal fault running northeast-southwest across the Kashmir Valley,transverse to the major thrust faults.Recent seismic events,including the M_(W)3.9 event near Nagbal and the M_(W)3.7 event near Mujgund in 2020,clustering of local seismic events,and two devastating historical seismic events(1828 AD and 1877/1878 AD)along this transition zone highlight the fault's activity and the region's vulnerability to future earthquakes.Delineation of such geological structures is crucial for seismic hazard assessment and micro-seismic zonation in the Kashmir Valley.Therefore,this study represents a significant step towards understanding the geodynamics and kinematics of the region and improving seismic risk mitigation strategies.展开更多
In this study,a powerful thermo-hydro-mechanical(THM)coupling solution scheme for saturated poroelastic media involving brittle fracturing is developed.Under the local thermal non-equilibrium(LTNE)assumption,this sche...In this study,a powerful thermo-hydro-mechanical(THM)coupling solution scheme for saturated poroelastic media involving brittle fracturing is developed.Under the local thermal non-equilibrium(LTNE)assumption,this scheme seamlessly combines the material point method(MPM)for accurately tracking solid-phase deformation and heat transport,and the Eulerian finite element method(FEM)for effectively capturing fluid flow and heat advection-diffusion behavior.The proposed approach circumvents the substantial challenges posed by large nonlinear equation systems with the monolithic solution scheme.The staggered solution process strategically separates each physical field through explicit or implicit integration.The characteristic-based method is used to stabilize advection-dominated heat flows for efficient numerical implementation.Furthermore,a fractional step approach is employed to decompose fluid velocity and pressure,thereby suppressing pore pressure oscillation on the linear background grid.The fracturing initiation and propagation are simulated by a rate-dependent phase field model.Through a series of quasi-static and transient simulations,the exceptional performance and promising potential of the proposed model in addressing THM fracturing problems in poro-elastic media is demonstrated.展开更多
This study characterizes the instrumental record of California climate for the last 170 years.Our goal is to look for hydrologic variability at decadal and longer time scales that would be consistent with paleoclimate...This study characterizes the instrumental record of California climate for the last 170 years.Our goal is to look for hydrologic variability at decadal and longer time scales that would be consistent with paleoclimate estimates of hydrologic variability in California for the last 3000 years.Our study focuses on meteorological summaries of annual precipitation and temperature.The precipitation records go back as far as 1850;the temperature records go back as far as 1880.California hydrologic records show strong variability at the interannual level due to ENSO forcing.They also all show a strong decadal(∼14 yr)cyclicity and evidence for multi-decadal to centennial variability that is consistent with California paleoclimate studies.California temperature records show a long-term warming of 5°F-6°F(2.8°C-3.4°C)associated with global warming,but there is no evidence for a similar long-term trend in hydrologic variability.Long-term Pacific Ocean variability adjacent to central and northern California,Pacific Decadal Oscillation(PDO)and North Pacific Gyre Oscillation(NPGO),show a similar decadal to centennial pattern of variability that we associate with our long-term hydrologic variability.The positive phase of the NPGO and the negative phase of the PDO are associated with the decadal scale(∼14 yr)dry cycles in California for the last 70 years.展开更多
The mechanics of slow-slip events and earthquakes is controlled by the constitutive behavior of rocks in active fault zones,which is sensitive to many factors encompassing lithology,temperature,confining and pore-flui...The mechanics of slow-slip events and earthquakes is controlled by the constitutive behavior of rocks in active fault zones,which is sensitive to many factors encompassing lithology,temperature,confining and pore-fluid pressure,and slip-rate,among others.Understanding the frictional properties of faults is crucial to predicting many aspects of the seismic cycle,from the source characteristics and recurrence patterns of earthquakes to the mechanics of remote triggering.Here,we describe a constitutive model that explains the slip-rate-,state-,temperature-,and normal-stress-dependence of fault friction for a wide variety of rock types,explaining the evolution of frictional stability under various barometric and hydrothermal conditions relevant to natural and induced seismicity,encompassing the brittle-ductile transition.The frictional strength is controlled by the area of contact junctions that form along a rough interface or by grain-to-grain contact in fault gouge and follows a nonlinear function of normal stress.The physical model explains the direct and evolutionary effects following perturbations in temperature,normal stress,and slip-rate,and the dependence of the frictional parameters on ambient physical conditions.The competition among healing and deformation mechanisms explains the dependence of fault stability on temperature,slip-rate,and effective normal stress for a wide range of rocks.The brittle-to-flow transition at the bottom of the seismogenic zone is caused by the thermobaric activation of semi-brittle deformation mechanisms.The model unifies and extends previous formulations,providing a single framework to explain rock deformation in Earth’s brittle and ductile layers.展开更多
The Mahabad rhyolitic complex,mostly composed of rhyolite but also including granite and granodiorite,is exposed in NW Iran as a part of the Central Iran Block.Porphyritic,hyalo-porphyritic and spheroidal are the main...The Mahabad rhyolitic complex,mostly composed of rhyolite but also including granite and granodiorite,is exposed in NW Iran as a part of the Central Iran Block.Porphyritic,hyalo-porphyritic and spheroidal are the main textures of the studied samples of rhyolite.U-Pb zircon chronology on three samples of Mahabad rhyolitic complex yielded Cambrian to Ediacaran ages of 537.6±6.6 Ma,547.4±6.5 Ma and 556.2±7.1 Ma.Based on geochemical analyses,the original magma was high potassium calc-alkaline to shoshonitic.The rocks are enriched in LREEs relative to HREEs.Trace element patterns of Mahabad rhyolite normalized to chondrites show negative anomalies of high-fi eld-strength elements(Ti,Nb,Ta,Hf,Yb,Y and Zr)and high LREEs and large ion lithophile element contents(Rb,K,Th and Ba).^(208)Pb/^(204) Pb(36.7219–39.0367),^(207) Pb/^(204) Pb(15.4963–15.7669)and ^(206) Pb/^(204) Pb(16.9405–19.9567)ratios indicate an EM-II enriched mantle source for the rhyolite magma.Large variation ofεHf(t)from−5.2 to+4.5 points to a mantle source with crustal material contribution in the magma genesis.The rhyolitic magma erupted in an active continental margin.The formation of calc-alkaline high potassium magma was probably related to metasomatism of the mantle because of the north to south subduction of Proto-Tethys oceanic crust beneath the northern margin of Gondwana continental crust.展开更多
The Middle to Late Jurassic,high-pressure metamorphic ophiolites of Inzecca Unit are well exposed in the Noceta-Vezzani area of Alpine Corsica.These metaophiolites were studied by using a multidisciplinary approach to...The Middle to Late Jurassic,high-pressure metamorphic ophiolites of Inzecca Unit are well exposed in the Noceta-Vezzani area of Alpine Corsica.These metaophiolites were studied by using a multidisciplinary approach to reconstruct the architecture of the oceanic sector from which they derived.The collected data indicate that this oceanic crust consists of a mantle metaperidotites and metaophicalcites,both covered by massive or pillow metabasalts with or without a layer of ophiolite-bearing metabreccias.展开更多
Lower Carboniferous clastic sedimentary rocks(i.e.,the Nanduan Formation)in the Changning-Menglian belt of the southeastern Tibetan Plateau may provide new insights into the tectonic evolution of the Paleo-Tethys Ocea...Lower Carboniferous clastic sedimentary rocks(i.e.,the Nanduan Formation)in the Changning-Menglian belt of the southeastern Tibetan Plateau may provide new insights into the tectonic evolution of the Paleo-Tethys Ocean.This paper presents new petrographic,geochemical,and detrital zircon U-Pb age data to constrain the provenance and depositional setting of these rocks.Sandstone samples of the Nanduan Formation are all quartz arenites(Q_(92-99)F_(1-7)L_(0-2))with high SiO_(2)contents(85.1 wt.%-95.2 wt.%;average=90.9 wt.%),indicating high compositional maturity.They exhibit fractionated rare earth element(REE)patterns,with light REE enrichment[(La/Yb)_(N)=6.48-12.1]and negative Eu anomalies(Eu/Eu^(*)=0.53-0.74),and marked negative Sr-Cs-V-Cr-Ni anomalies in upper continental crust-normalised multi-element diagrams.The geochemical features and heavy mineral assemblages suggest that sediments were mainly derived from ancient sedimentary rocks in cratonic interiors or stable continental areas,and were probably deposited in a passive continental margin setting.Detrital zircon U-Pb dating(n=256)of the Nanduan Formation sandstones defines three distinct age peaks in the Pan-African(600-500 Ma),younger Grenvillian(950-850 Ma),and older Grenvillian(1250-1000 Ma).Their zircon age spectra are similar to those of Lower Paleozoic sedimentary rocks(i.e.,the Mengtong and Mengdingjie groups)in the BaoshanSibumasu Block,but significantly different from those of older rocks in the Simao-Indochina and other surrounding blocks(i.e.,the western Yangtze,western Cathaysia,western Qiangtang,Tethyan Himalaya,and Lhasa blocks).This suggests that the Nanduan Formation was deposited at the margin of the Baoshan-Sibumasu Block.Combining the new data presented in this study with published data,we suggest that the Nanduan Formation and underlying Lancang Group were deposited in the same setting during the Early and Late Paleozoic,respectively.展开更多
Geological CO_(2) storage is a promising strategy for reducing greenhouse gas emissions;however,its underlying multiphase reactive flow mechanisms remain poorly understood.We conducted steady-state imbibition relative...Geological CO_(2) storage is a promising strategy for reducing greenhouse gas emissions;however,its underlying multiphase reactive flow mechanisms remain poorly understood.We conducted steady-state imbibition relative permeability experiments on sandstone from a proposed storage site,comple-mented by in situ X-ray imaging and ex situ analyses using scanning electron microscopy(SEM)and energy-dispersive X-ray spectroscopy(EDS).Despite our use of a brine that was pre-equilibrated with CO_(2),there was a significant reduction in both CO_(2) relative permeability and absolute permeability during multiphase flow due to chemical reactions.This reduction was driven by decreased pore and throat sizes,diminished connectivity,and increased irregularity of pore and throat shapes,as revealed by in situ pore-scale imaging.Mineral dissolution,primarily of feldspar,albite,and calcite,along with precipitation resulting from feldspar-to-kaolinite transformation and fines migration,were identified as contributing factors through SEM-EDS analysis.This work provides a benchmark for storage in mineralogically complex sandstones,for which the impact of chemical reactions on multiphase flow properties has been measured.展开更多
Large-scale Danian-age(post-K/Pg boundary)Deccan magmatism is well known from the Mumbai metropolitan area,located in the structurally complex Panvel flexure zone along the western Indian rifted continental margin.Thi...Large-scale Danian-age(post-K/Pg boundary)Deccan magmatism is well known from the Mumbai metropolitan area,located in the structurally complex Panvel flexure zone along the western Indian rifted continental margin.This compositionally diverse late-Deccan magmatic suite contains subaerial tholeiitic lavas and dykes typical of the main Deccan province,with many features atypical of the Deccan,such as spilitic pillow lavas,“intertrappean”sediments(often containing considerable volcanic ash),rhyolitic lavas and tuffs,gabbro-granophyre intrusions,and trachyte intrusions containing alkali basalt enclaves.Most of these units,previously dated at 62.5 Ma to 61 Ma,are contemporaneous with or slightly postdate the 62.5 Ma India-Seychelles continental breakup and Panvel flexure formation.In the Dongri-Uttan area,two samples of a>50-m-thick,columnar-jointed rhyolite from the Darkhan Quarry and from a section behind the current Uttan Sagari Police Station have previously been dated at 62.6±0.6 Ma and 62.9±0.2 Ma(^(40)Ar/^(39)Ar,2r errors).New exposures reveal that these two statistically indistinguishable 40 Ar/39 Ar ages correspond to two distinct rhyolite units,separated by well-bedded silicic ash.The columnar rhyolites are microcrystalline,composed of quartz and alkali feldspar,with rare small(1–2 mm),altered feldspar phenocrysts,and no recognisable relict vitroclasts.Given the westerly structural dip,most of their lateral extent is submerged under the Arabian Sea,and we consider them to be possible flood rhyolite lavas.We interpret the ash beds,composed of pumice clasts and glass shards,as a low-grade(nonwelded)vitric ash,derived from a possibly distal Plinian eruption and deposited by fallout.The lavas and ash are peraluminous rhyolites.The lavas are Sr-Ba-poor and Rb-Zr-Nb-rich,and show“seagull-shaped”rare earth element patterns with deep negative europium anomalies.These crystal-poor lavas are“hot-dry-reduced”rhyolites typical of intraplate,continental rift and rifted margin settings.The very different high-field strength element contents of the lavas and the ash indicate compositionally distinct magma batches.The 62.5 Ma Dongri-Uttan sequence provides clear evidence for rapid silicic eruptions of effusive and explosive nature,alternating with each other and sourced from distinct magma chambers and eruptive vents.A newly identified,highly feldspar-phyric trachyte intrusion marks the last phase of magmatic activity in the area,corresponding with late-stage trachyte-syenite intrusions exposed in coastal western India and the Seychelles,and shows that the Mumbai rhyolites and trachytes form a compositional continuum.展开更多
基金supported by the research grant of the Kongju National University in 2023.
文摘The purpose of this study is to investigate the effect of Panoramic Virtual Reality(PVR)applied to online earth science classes on students’learning flow.To this end,a PVR learning material was made with a geology learning site,which contains a core geologic concept contained in a high school curriculum in Korea.To this end,a PVR learning material was made at a geologic field site to provide an interactive and engaging way for students to grasp core geologic concepts according to the high school curriculum in Korea.The PVR was applied to online earth science classes with 45 high school students.In order to examine the effect of the PVR on students'learning flow,pre-post learning flow test papers were used,then matchedsample t-test analysis and students'responses were analyzed.The result shows online classes with PVR have positive effects on learning flow(p<0.05).And it was possible for the students to observe three-dimensional geologic structures effectively in online classes as in offline field trips.And the students'responded with positive feedbacks.These suggest that PVR in online classes can be used as an effective teaching method,which can improve students'flow and eventually understanding subjects.
基金the Anusandhan National Research Foundation(ANRF),Science and Engineering Research Board(SERB),Department of Science&Technology,Government of India for a start-up research grant(M-14/0599,Sanction order no.SRG/2022/001478)Seed Grant under Institutions of Eminence(IoE),Banaras Hindu University(BHU)(Dev.Scheme No.6031)for financial assistance.
文摘The green energy transition relies heavily on critical metals,such as rare earth elements(REEs).However,their reserves are primarily focused in a few countries,such as China,which accounts for approximately 70%of global production.Hence,several countries are currently looking for alternative resources for REEs.Alternative REE resources in the supply chain include recycling of e-waste,industrial waste like red mud and phosphogypsum,coal ash,mine tailings,ocean floor sediments,and even certain types of sedimentary deposits like phosphorites where REEs are present in lower concentrations but at larger volumes compared to primary ore deposits which are becoming targets by REEs industry.Currently,several studies are going on the development of eco-friendly REEs extraction technologies from phosphorite deposits.Consequently,advanced data analysis tools,such as Machine Learning(ML),are becoming increasingly important in mineral prospectivity and are rapidly gaining traction in the earth sciences.Phosphorite deposits are mainly used to manufacture fertilizers as these rocks are known for their significant phosphorus content.Moreover,these formations are considered a prospective resource of REEs.The different types of phosphorite deposits such as continental,seamount,and ore deposits worldwide reported concentrations of∑REE upto 18,000µg/g.Due to the augmented claim of REEs for various ultra-modern,and green technology applications that are required to switch over to a carbon-neutral environment,these phosphorite deposits have become an important target mostly because of their relatively higher content of REEs especially heavy rare earth elements(HREE).For example,Mississippian phosphorites reported ∑ HREE 7,000µg/g.To have a comprehensive understanding of the REEs potential of these phosphorite deposits which also include several Chinese phosphorite deposits,this study is undertaken to review the phosphorite deposits in the world and their REEs potential,in addition to some of the associated aspects such as applications and formation mechanisms for different types of phosphorite deposits such as igneous phosphate deposits,sedimentary phosphorite deposits,marine phosphorite deposits,cave phosphate deposits,and insular guano deposits.Other important aspects include their occurrences,types,geochemical characteristics,the REEs enrichment mechanisms,and various recovery methods adopted to recover REEs from different phosphorite deposits.The present review paper concludes that the recent studies highlight the global potential of phosphorite deposits to satisfy the increasing demand for REEs.Extracting REEs from phosphorite presents no significant technological or environmental difficulties,as long as radioactive elements are eliminated.In India,more comprehensive geological surveys,along with the advancement of new methods and evaluations,are required to locate phosphorite deposits with high concentrations of REEs.
文摘The 3^(rd) International Earth Science Olympiad(www.ieso2009.tw/home/home.html)was organized by the National Taiwan Normal University at Taipei,Taiwan.Fifty students from 14 countries participated in the 3^(rd) IESO.Four other countries sent Observers.
文摘This paper reviewed the level of Geoscience education in Ghana and offers recommendations for improvement.The review showed that Geoscience education in Ghana is inadequate and Geoscience literacy and awareness in the public are weak.Currently,the level of Geoscience content in the formal educational curricula of Basic and Senior High schools as well as colleges of education in Ghana is very low.In addition,out of 129 universities in Ghana,only seven offer Geoscience or Geoscience-related programs.To improve the level of formal Geoscience education we recommend the following:(1)introduce geoscience degree programs in colleges of education,(2)introduce Geoscience as a subject in the Senior High School curriculum,(3)improve the Geoscience content in the Basic School curriculum,(4)Encourage more universities to offer degree programs in Geoscience.To train the next generation of Geoscientists,we recommend improvements in Geoscience degree programs in terms of(1)the curriculum,content,proficiencies,and skills,(2)the use of pedagogy and technology,and(3)the preparation of teachers to build capacity in science and core geology.To help increase Geoscience awareness and literacy in Ghana,the Geoscience workforce should team up with relevant stakeholders to promote Geoscience outreach in Ghana.
文摘Introduction.The International Union of Geological Sciences(IUGS)is a prominent non-governmental organization dedicated to promoting and fostering the study of geological sciences internationally.Established in 1961,the IUGS is a member of the International Science Council and plays a pivotal role in setting global standards in geological sciences,facilitating international collaboration,and supporting the coordination of major global geological events and research initiatives(Cheong and Kim,2021).One of the key events organized by the IUGS is the International Geological Congress(IGC),held every four years.This congress serves as a vital forum for geologists from around the world to share their latest research findings,discuss advancements in the field,and explore new directions in geological sciences.The IGC encompasses a wide range of topics including geology,geophysics,mineralogy,paleontology,and sedimentology,among others,reflecting the diversity and interdisciplinary nature of the field(Cheong and Kim,2021).
基金funded by the National Natural Science Foundation of China(Grant Nos.42072089 and 41530206)。
文摘Both fractional crystallization and fluid-melt-crystal interaction are involved in the formation of highly fractionated granites.This paper assessed those two processes using geochemistry of muscovite and tourmaline and bulkrock chemistry of multi-phase Wangxianling granitoids,South China.Compositional variations suggest the coarse-grained muscovite granite is produced from fractional crystallization of the two-mica granite whereas the fine-grained muscovite granite represents a distinct magma pulse.Progressive fractionation of quartz,feldspar and biotite leads to elevated boron and aluminum content in melt which promoted muscovite and tourmaline to crystallize,which promotes two-mica granite evolving towards tourmaline-bearing muscovite granite.Fluid-melt-crystal interaction occurred at the magmatichydrothermal transitional stage and resulted in the textural and chemical zonings of tourmaline and muscovite in finegrained muscovite granite.The rims of both tourmaline and muscovite are characterized by the enrichment of fluid mobile elements such as Li,Mn,Cs and Zn and heavierδ^(11)B values of the tourmaline rims(-15.0‰to-13.6‰)compared to cores(-15.7‰to-14.3‰).Meanwhile,significant M-type REE tetrad effects(TE_(1,3)=1.07-1.18)and low K/Rb ratios(48-52)also correspond to fluid-melt-crystal interaction.This study shows zoned muscovite and tourmaline can be excellent tracers of fractional crystallization and late-stage fluid-melt-crystal interaction in highly evolved magmatic systems.
文摘The GPS data sourced from the permanent GPS network in the Kashmir Himalaya were utilized to quantify both vertical and horizontal deformation rates in the Kashmir Valley of the northwestern Himalaya.While lateral deformation in the Kashmir basin has been previously quantified,the vertical component has not been studied yet.To quantify the vertical and horizontal deformation rates in the Kashmir Valley,we use GAMIT/GLOBK software to process the GPS data.The lateral motion data indicate that the Indian plate continues to move towards the Eurasian plate at a rate of 36-42 mm/yr,while the vertical vectors infer a transition zone across the Kashmir valley.Using ArcGIS,Iso-base and Iso-ketabase maps were generated from the GPS vertical vectors to study the vertical deformation status of the Kashmir Valley.The analysis of vertical vectors reveals a significant transition zone in the Kashmir Valley.The vertical vector data show distinct patterns:GPS stations in the northeast,south,and southeast of the Kashmir Valley exhibit uplift,while stations in the north,northwest,and southwest show subsidence.The uplift velocity increases as we move from the Srinagar station to the Kulgam station via Tral and Ashmuqam,while the subsidence rate increases as we move from the Bandipora station to Mulgam and Uri.Specifically,the highest uplift rate(5.2±0.6 mm/yr)is observed at the Kulgam station and the highest subsidence rate(-6.5±1.26 mm/yr)at the Uri station.On average,vertical subsidence of-2.81 mm/yr is recorded along the north and northwest sides of the valley,and an average uplift of 3.04 mm/yr in the south and southeast.Integrating geomorphological observations with GPS measurements,we infer the presence of an active normal fault running northeast-southwest across the Kashmir Valley,transverse to the major thrust faults.Recent seismic events,including the M_(W)3.9 event near Nagbal and the M_(W)3.7 event near Mujgund in 2020,clustering of local seismic events,and two devastating historical seismic events(1828 AD and 1877/1878 AD)along this transition zone highlight the fault's activity and the region's vulnerability to future earthquakes.Delineation of such geological structures is crucial for seismic hazard assessment and micro-seismic zonation in the Kashmir Valley.Therefore,this study represents a significant step towards understanding the geodynamics and kinematics of the region and improving seismic risk mitigation strategies.
基金supported by National Natural Science Foundation of China(Grant No.42377149)the Research Grants Council of Hong Kong(General Research Fund Project No.17202423).
文摘In this study,a powerful thermo-hydro-mechanical(THM)coupling solution scheme for saturated poroelastic media involving brittle fracturing is developed.Under the local thermal non-equilibrium(LTNE)assumption,this scheme seamlessly combines the material point method(MPM)for accurately tracking solid-phase deformation and heat transport,and the Eulerian finite element method(FEM)for effectively capturing fluid flow and heat advection-diffusion behavior.The proposed approach circumvents the substantial challenges posed by large nonlinear equation systems with the monolithic solution scheme.The staggered solution process strategically separates each physical field through explicit or implicit integration.The characteristic-based method is used to stabilize advection-dominated heat flows for efficient numerical implementation.Furthermore,a fractional step approach is employed to decompose fluid velocity and pressure,thereby suppressing pore pressure oscillation on the linear background grid.The fracturing initiation and propagation are simulated by a rate-dependent phase field model.Through a series of quasi-static and transient simulations,the exceptional performance and promising potential of the proposed model in addressing THM fracturing problems in poro-elastic media is demonstrated.
文摘This study characterizes the instrumental record of California climate for the last 170 years.Our goal is to look for hydrologic variability at decadal and longer time scales that would be consistent with paleoclimate estimates of hydrologic variability in California for the last 3000 years.Our study focuses on meteorological summaries of annual precipitation and temperature.The precipitation records go back as far as 1850;the temperature records go back as far as 1880.California hydrologic records show strong variability at the interannual level due to ENSO forcing.They also all show a strong decadal(∼14 yr)cyclicity and evidence for multi-decadal to centennial variability that is consistent with California paleoclimate studies.California temperature records show a long-term warming of 5°F-6°F(2.8°C-3.4°C)associated with global warming,but there is no evidence for a similar long-term trend in hydrologic variability.Long-term Pacific Ocean variability adjacent to central and northern California,Pacific Decadal Oscillation(PDO)and North Pacific Gyre Oscillation(NPGO),show a similar decadal to centennial pattern of variability that we associate with our long-term hydrologic variability.The positive phase of the NPGO and the negative phase of the PDO are associated with the decadal scale(∼14 yr)dry cycles in California for the last 70 years.
基金funded by the National Science Foundation(No.EAR-1848192)。
文摘The mechanics of slow-slip events and earthquakes is controlled by the constitutive behavior of rocks in active fault zones,which is sensitive to many factors encompassing lithology,temperature,confining and pore-fluid pressure,and slip-rate,among others.Understanding the frictional properties of faults is crucial to predicting many aspects of the seismic cycle,from the source characteristics and recurrence patterns of earthquakes to the mechanics of remote triggering.Here,we describe a constitutive model that explains the slip-rate-,state-,temperature-,and normal-stress-dependence of fault friction for a wide variety of rock types,explaining the evolution of frictional stability under various barometric and hydrothermal conditions relevant to natural and induced seismicity,encompassing the brittle-ductile transition.The frictional strength is controlled by the area of contact junctions that form along a rough interface or by grain-to-grain contact in fault gouge and follows a nonlinear function of normal stress.The physical model explains the direct and evolutionary effects following perturbations in temperature,normal stress,and slip-rate,and the dependence of the frictional parameters on ambient physical conditions.The competition among healing and deformation mechanisms explains the dependence of fault stability on temperature,slip-rate,and effective normal stress for a wide range of rocks.The brittle-to-flow transition at the bottom of the seismogenic zone is caused by the thermobaric activation of semi-brittle deformation mechanisms.The model unifies and extends previous formulations,providing a single framework to explain rock deformation in Earth’s brittle and ductile layers.
文摘The Mahabad rhyolitic complex,mostly composed of rhyolite but also including granite and granodiorite,is exposed in NW Iran as a part of the Central Iran Block.Porphyritic,hyalo-porphyritic and spheroidal are the main textures of the studied samples of rhyolite.U-Pb zircon chronology on three samples of Mahabad rhyolitic complex yielded Cambrian to Ediacaran ages of 537.6±6.6 Ma,547.4±6.5 Ma and 556.2±7.1 Ma.Based on geochemical analyses,the original magma was high potassium calc-alkaline to shoshonitic.The rocks are enriched in LREEs relative to HREEs.Trace element patterns of Mahabad rhyolite normalized to chondrites show negative anomalies of high-fi eld-strength elements(Ti,Nb,Ta,Hf,Yb,Y and Zr)and high LREEs and large ion lithophile element contents(Rb,K,Th and Ba).^(208)Pb/^(204) Pb(36.7219–39.0367),^(207) Pb/^(204) Pb(15.4963–15.7669)and ^(206) Pb/^(204) Pb(16.9405–19.9567)ratios indicate an EM-II enriched mantle source for the rhyolite magma.Large variation ofεHf(t)from−5.2 to+4.5 points to a mantle source with crustal material contribution in the magma genesis.The rhyolitic magma erupted in an active continental margin.The formation of calc-alkaline high potassium magma was probably related to metasomatism of the mantle because of the north to south subduction of Proto-Tethys oceanic crust beneath the northern margin of Gondwana continental crust.
基金supported by PRIN 2020 project(Resp.Michele Marroni)Claudia D’Oriano(INGV)Matteo Masotta and Danis Filimon(Earth Science Dept)are also thanked for analytical support in the laboratoriesThis work benefited from the PRA 2022 project handled by Francesca Meneghini.
文摘The Middle to Late Jurassic,high-pressure metamorphic ophiolites of Inzecca Unit are well exposed in the Noceta-Vezzani area of Alpine Corsica.These metaophiolites were studied by using a multidisciplinary approach to reconstruct the architecture of the oceanic sector from which they derived.The collected data indicate that this oceanic crust consists of a mantle metaperidotites and metaophicalcites,both covered by massive or pillow metabasalts with or without a layer of ophiolite-bearing metabreccias.
基金financially supported by the Yunnan Fundamental Research Projects(No.202201AT070077)the Ministry-Province Cooperation Pilot Projects(No.2023ZRBSHZ059)+1 种基金the Major Science and Technology Special Plan of Yunnan Province(No.202202AG050006)the National Natural Science Foundation of China(No.41603032)。
文摘Lower Carboniferous clastic sedimentary rocks(i.e.,the Nanduan Formation)in the Changning-Menglian belt of the southeastern Tibetan Plateau may provide new insights into the tectonic evolution of the Paleo-Tethys Ocean.This paper presents new petrographic,geochemical,and detrital zircon U-Pb age data to constrain the provenance and depositional setting of these rocks.Sandstone samples of the Nanduan Formation are all quartz arenites(Q_(92-99)F_(1-7)L_(0-2))with high SiO_(2)contents(85.1 wt.%-95.2 wt.%;average=90.9 wt.%),indicating high compositional maturity.They exhibit fractionated rare earth element(REE)patterns,with light REE enrichment[(La/Yb)_(N)=6.48-12.1]and negative Eu anomalies(Eu/Eu^(*)=0.53-0.74),and marked negative Sr-Cs-V-Cr-Ni anomalies in upper continental crust-normalised multi-element diagrams.The geochemical features and heavy mineral assemblages suggest that sediments were mainly derived from ancient sedimentary rocks in cratonic interiors or stable continental areas,and were probably deposited in a passive continental margin setting.Detrital zircon U-Pb dating(n=256)of the Nanduan Formation sandstones defines three distinct age peaks in the Pan-African(600-500 Ma),younger Grenvillian(950-850 Ma),and older Grenvillian(1250-1000 Ma).Their zircon age spectra are similar to those of Lower Paleozoic sedimentary rocks(i.e.,the Mengtong and Mengdingjie groups)in the BaoshanSibumasu Block,but significantly different from those of older rocks in the Simao-Indochina and other surrounding blocks(i.e.,the western Yangtze,western Cathaysia,western Qiangtang,Tethyan Himalaya,and Lhasa blocks).This suggests that the Nanduan Formation was deposited at the margin of the Baoshan-Sibumasu Block.Combining the new data presented in this study with published data,we suggest that the Nanduan Formation and underlying Lancang Group were deposited in the same setting during the Early and Late Paleozoic,respectively.
文摘Geological CO_(2) storage is a promising strategy for reducing greenhouse gas emissions;however,its underlying multiphase reactive flow mechanisms remain poorly understood.We conducted steady-state imbibition relative permeability experiments on sandstone from a proposed storage site,comple-mented by in situ X-ray imaging and ex situ analyses using scanning electron microscopy(SEM)and energy-dispersive X-ray spectroscopy(EDS).Despite our use of a brine that was pre-equilibrated with CO_(2),there was a significant reduction in both CO_(2) relative permeability and absolute permeability during multiphase flow due to chemical reactions.This reduction was driven by decreased pore and throat sizes,diminished connectivity,and increased irregularity of pore and throat shapes,as revealed by in situ pore-scale imaging.Mineral dissolution,primarily of feldspar,albite,and calcite,along with precipitation resulting from feldspar-to-kaolinite transformation and fines migration,were identified as contributing factors through SEM-EDS analysis.This work provides a benchmark for storage in mineralogically complex sandstones,for which the impact of chemical reactions on multiphase flow properties has been measured.
基金supported by the research award project RI/0220-10000618-001 to Sheth from the Industrial Research and Consultancy Centre(IRCC)IIT Bombay.Shekhar and Astha were supported by Prime Minister’s Research Fellowships(PMRF,File Nos.1303100 and 1303103,respectively)+4 种基金Naik was initially supported by an IIT Bombay Institute Post-Doctoral Fellowship(File No.HR-1(HRM-1)/Rect/33/2022/20003002)subsequently by a Goa State Research Foundation Post-doctoral Fellowship(File No.PDF2024003)We express our sincere gratitude to Prof.N.Prabhakar for kindly granting us access to the WD-XRF spectrometry facility(SIP ProjectWBS Code:IN/22-1111039E-01)the ICP-MS facility,and the SERB-funded EPMA National Facility(IRPHA Grant No.IR/S4/ESF-16/2009(G))in the Department of Earth Sciences,IIT Bombay.
文摘Large-scale Danian-age(post-K/Pg boundary)Deccan magmatism is well known from the Mumbai metropolitan area,located in the structurally complex Panvel flexure zone along the western Indian rifted continental margin.This compositionally diverse late-Deccan magmatic suite contains subaerial tholeiitic lavas and dykes typical of the main Deccan province,with many features atypical of the Deccan,such as spilitic pillow lavas,“intertrappean”sediments(often containing considerable volcanic ash),rhyolitic lavas and tuffs,gabbro-granophyre intrusions,and trachyte intrusions containing alkali basalt enclaves.Most of these units,previously dated at 62.5 Ma to 61 Ma,are contemporaneous with or slightly postdate the 62.5 Ma India-Seychelles continental breakup and Panvel flexure formation.In the Dongri-Uttan area,two samples of a>50-m-thick,columnar-jointed rhyolite from the Darkhan Quarry and from a section behind the current Uttan Sagari Police Station have previously been dated at 62.6±0.6 Ma and 62.9±0.2 Ma(^(40)Ar/^(39)Ar,2r errors).New exposures reveal that these two statistically indistinguishable 40 Ar/39 Ar ages correspond to two distinct rhyolite units,separated by well-bedded silicic ash.The columnar rhyolites are microcrystalline,composed of quartz and alkali feldspar,with rare small(1–2 mm),altered feldspar phenocrysts,and no recognisable relict vitroclasts.Given the westerly structural dip,most of their lateral extent is submerged under the Arabian Sea,and we consider them to be possible flood rhyolite lavas.We interpret the ash beds,composed of pumice clasts and glass shards,as a low-grade(nonwelded)vitric ash,derived from a possibly distal Plinian eruption and deposited by fallout.The lavas and ash are peraluminous rhyolites.The lavas are Sr-Ba-poor and Rb-Zr-Nb-rich,and show“seagull-shaped”rare earth element patterns with deep negative europium anomalies.These crystal-poor lavas are“hot-dry-reduced”rhyolites typical of intraplate,continental rift and rifted margin settings.The very different high-field strength element contents of the lavas and the ash indicate compositionally distinct magma batches.The 62.5 Ma Dongri-Uttan sequence provides clear evidence for rapid silicic eruptions of effusive and explosive nature,alternating with each other and sourced from distinct magma chambers and eruptive vents.A newly identified,highly feldspar-phyric trachyte intrusion marks the last phase of magmatic activity in the area,corresponding with late-stage trachyte-syenite intrusions exposed in coastal western India and the Seychelles,and shows that the Mumbai rhyolites and trachytes form a compositional continuum.
