This paper reports statistical results of Seismo-Ionospheric Anomalies(SIAs) of the Total Electron Content(TEC) in the Global Ionosphere Map(GIM) associated with 56 M≥6.0 earthquakes in China during 1998—2012.To det...This paper reports statistical results of Seismo-Ionospheric Anomalies(SIAs) of the Total Electron Content(TEC) in the Global Ionosphere Map(GIM) associated with 56 M≥6.0 earthquakes in China during 1998—2012.To detect SIA,a quartile-based(i.e.median-based) process is performed.TEC anomalies for the period of earthquakes without being led by magnetic storms about 10 days are further isolated and examined to confirm the SIP existence.Results show that SIA is the TEC significantly decrease in the afternoon period 2—9 days before the earthquakes in China,which is in a good agreement with the SIA appearing before the 12 May 2008 M 8.0 Wenchuan earthquake.展开更多
Araneiforms are spider-like ground patterns that are widespread in the southern polar regions of Mars.A gas erosion process driven by the seasonal sublimation of CO_(2)ice was proposed as an explanation for their form...Araneiforms are spider-like ground patterns that are widespread in the southern polar regions of Mars.A gas erosion process driven by the seasonal sublimation of CO_(2)ice was proposed as an explanation for their formation,which cannot occur on Earth due to the high climatic temperature.In this study,we propose an alternative mechanism that attrib-utes the araneiform formation to the erosion of upwelling salt water from the subsurface,relying on the identification of the first terrestrial analog found in a playa of the Qaidam Basin on the northern Tibetan Plateau.Morphological analysis indicates that the structures in the Qaidam Basin have fractal features comparable to araneiforms on Mars.A numerical model is developed to investigate the araneiform formation driven by the water-diffusion mechanism.The simulation res-ults indicate that the water-diffusion process,under varying ground conditions,may be responsible for the diverse aranei-form morphologies observed on both Earth and Mars.Our numerical simulations also demonstrate that the orientations of the saltwater diffusion networks are controlled by pre-existing polygonal cracks,which is consistent with observations of araneiforms on Mars and Earth.Our study thus suggests that a saltwater-related origin of the araneiform is possible and has significant implications for water searches on Mars.展开更多
The Grains containing Oil Inclusions(GOI)data in currently gas/condensate-beating Jurassic and Cretaceous reservoir sandstones of Well Pen 5(the Mosuowan area of central Junggar Basin,NW China)are generally greater th...The Grains containing Oil Inclusions(GOI)data in currently gas/condensate-beating Jurassic and Cretaceous reservoir sandstones of Well Pen 5(the Mosuowan area of central Junggar Basin,NW China)are generally greater than the empirical threshold line of 5%.This is consistent with the gas-condensate section originally containing a palaeo-oil column.In order to assess the origin of the oil trapped in the oil inclusion and its relationship to the free oil/gas-condensate,a detailed molecular geochemical study was carried out for correlation between the free and inclusion oils.The paleo oil is most likely sourced from the Lower Permian Fengeheng Formation,which generated hydrocarbons primarily during Late Triassic and the oils were later secondarily altered and dysmigrated along faults likely during Late Jurassic-Early Cretaceous.In contrast,the current reservoired oil/gas-condensate mainly derived from the Middle Permian Lower Wuerhe Formation,whose peak generation time last from Late Cretaceous even to the present.This paper showed that integrated oil-bearing fluid inclusion analyses have likely allowed a complex multi-phase charge history to be recognized and resolved with a high degree of confidence.展开更多
The Ni-Cu-platinum group element sulfide ore deposits of the Kharaelakh Intrusion,Noril′sk Region,Siberia,represent a large concentration of sulfides associated with a small differentiated intrusion formed at the edg...The Ni-Cu-platinum group element sulfide ore deposits of the Kharaelakh Intrusion,Noril′sk Region,Siberia,represent a large concentration of sulfides associated with a small differentiated intrusion formed at the edge of the Siberian Craton in the roots of the Siberian Trap flood basalt.The deposit is associated with an intrusion that occupies a flanking periclinal structure adjacent to the Noril′sk-Kharaelakh Fault.The intrusion is strongly differentiated and comprises taxitic gabbrodolerites,picritic gabbrodolerites,and gabbrodolerites within the main body which in turn forms a chonolith within a sheet-like intrusion that extends laterally to form extensive undifferentiated sills of gabbrodolerite.The intrusion substantially replaces the stratigraphy of the country rocks,and although it appears to have exploited the axis of structures developed in response to transtension,the intrusion has created space by both mechanical dilation of stratigraphy and magmatic replacement of pre-existing sedimentary rocks.The frontal lobes of the main intrusion have complex apophyses of gabrodolerite on a range of scales that demonstrate replacement of the sedimentary rocks and link to the development of an extensive metamorphic halo in the country rocks.This halo is much narrower over the main body of the intrusion,and these observations have implications for the thermal history of the intrusion.Mg-skarns and breccias are developed in the roof of the main body of the intrusion.Within the intrusion,the taxitic rocks contain vesicles and the blebby sulfides developed in the picritic and taxitic gabbrodolerites appear to have a linkage to volatile phases.Cuprous sulfide mineralization developed at the roof of the Kharaelakh Intrusion is associated with metamorphosed and skarn-bearing country rocks,and appears to have been generated by a combination of sulfide fractionation and associated metasomatism.The geological relationships appear consistent with a chonolith model for the development of the differentiated intrusion and mineralization,but the extent of metasmorphism of the country rocks appears to be related to the unusual thickness of gabbrodolerite apophyses at the flanks of the intrusion rather than metamorphism produced by the passage of mafic magma through the intrusion.Variations in disseminated sulfide compositions and metasomatic textures in the skarns are described,and a model is proposed which balances traditional views on the evolution of the magma conduits with the impact of magmatic fluids transported through the magma column(i.e.transmagmatic fluids).The importance of structures in controlling the nature of the conduit,and the resultant small intrusions with excess sulfide is a feature of many other Ni-Cu sulfide deposits including Voisey′s Bay,and it is suggested that the sulfides are more likely to have beentransported from depth into their final resting place rather than developed by in-situ equilibration of sulfide with fresh magma in the chonolith.展开更多
Distinguishing geochemical anomalies from background is a basic task in exploratory geochemistry. The derivation of geochemical anomalies from stream sediment geochemical data and the decomposition of these anomalies ...Distinguishing geochemical anomalies from background is a basic task in exploratory geochemistry. The derivation of geochemical anomalies from stream sediment geochemical data and the decomposition of these anomalies into their component patterns were described. A set of stream sediment geochemical data was obtained for 1 880 km 2 of the Pangxidong area, which is in the southern part of the recently recognized Qinzhou-Hangzhou joint tectonic belt. This belt crosses southern China and tends to the northwest (NE) direction. The total number of collected samples was 7 236, and the concentrations of Ag, Au, Cu, As, Pb and Zn were measured for each sample. The spatial combination distribution law of geochemical elements and principal component analysis (PCA) were used to construct combination models for the identification of combinations of geochemical anomalies. Spectrum-area (S-A) fractal modeling was used to strengthen weak anomalies and separate them from the background. Composite anomaly modeling was combined with fractal filtering techniques to process and analyze the geochemical data. The raster maps of Au, Ag, Cu, As, Pb and Zn were obtained by the multifractal inverse distance weighted (MIDW) method. PCA was used to combine the Au, Ag, Cu, As, Pb, and Zn concentration values. The S-A fractal method was used to decompose the first component pattern achieved by the PCA. The results show that combination anomalies from a combination of variables coincide with the known mineralization of the study area. Although the combination anomalies cannot reflect local anomalies closely enough, high-anomaly areas indicate good sites for further exploration for unknown deposits. On this basis, anomaly and background separation from combination anomalies using fractal filtering techniques can provide guidance for later work.展开更多
The Ailaoshan aquamarine-bearing pegmatites are associated with Proterozoic metamorphic rocks in the southern portion of the Ailaoshan fault-folded complex.The gem-bearing pegmatite mineralization zones of the region ...The Ailaoshan aquamarine-bearing pegmatites are associated with Proterozoic metamorphic rocks in the southern portion of the Ailaoshan fault-folded complex.The gem-bearing pegmatite mineralization zones of the region occur in areas generally consistent with the regional tectonic trend.The pegmatites are found in metamorphic rocks,migmatites and in the inner/outer contact zones of gneissoid granites. The Rb-Sr isochron drawn for the pegmatites is 26～31 Ma,(i.e.in Himalayan).The homogenization temperatures of melt and liquid inclusions in minerals vary from 185 to 920℃,which are comparable to the inclusions observed in banded migmatites and ptygmatic quartz veins in the surrounding metamorphic rocks. The mineralization fluids of the pegmatite were rich in HCO_3 and CO_2,and their compositional assemblages are comparable to metamorphic fluids.Results of H,O,C,Si etc.isotopic analyses and REE,and Be analyses indicates that the sources of mineralization components that formed the pegmatites are closely associated with metamorphic fluids and the enclosing metamorphic rocks. A pegmatite structure simulation experiment was conducted at high temperature and pressure(840℃and 1,500×105Pa.),with various metamorphic rock samples in a water-rich and volatile-rich environment.When the liquidus was reached,the temperature was gradually decreased at the rate of 5～10℃/day over a time period of three months.SEM energy-dispersive spectrum analyses were performed on the experimental products.A series of pegmatoid textures were observed including zonal texture,megacryst texture,drusy cavities,crystal druses,and vesicular texture along with more than ten types of minerals including plagioclase,microcline,quartz and biotite.Different metamorphic rock melts generated different mineral assemblages.Experiment results revealed that the partial melting of metamorphic rocks could form melts similar to pegmatite magmas. Based upon the geological characteristics,geochemistry,and pegmatite texture simulation experimental results,it is concluded that the mineralization components of Ailaoshan aquamarine-bearing pegmatites came from metamorphic rocks.The petrogenetic model for the origin of pegmatites is related to ultrametamorphism and metamorphic anatexis.展开更多
The characteristics of hosted magmas and their petrogenesis based on electron microprobe determination of trace element contents in zircons were discussed. Trace element geochemistry of zircons indicates that zircons ...The characteristics of hosted magmas and their petrogenesis based on electron microprobe determination of trace element contents in zircons were discussed. Trace element geochemistry of zircons indicates that zircons in both gabbro and quartz syenite have two-generations. Zircons of the first generations are crystallized in the magma chamber, whereas those of the second generations are formed in supercooling environment. The former is richer in Zr, but poorer in U, Th, Hf and Y. Quartz diorite porphyrite contains zircons that can be distinguished into the early and late generations. Compared to the late generation, the early generation is richer in Zr but poorer in U, Th, Hf and Y. No conspicuous disruption of zircon evolution has been found in both biotite monzogranite and fine-grained granite. However, the content of zircon in fine-grained granite is higher in U, Th and Y and lower in Zr relative to biotite monzogranite without significant contrast in mass fraction ratio of ZrO2 to HfO2 ratio. Such differences in zircon geochemistry of various intrusive phases and the occurrence of the two zircon generations within a single intrusive phase suggest that these phases of magmas are generated from diverse sources during post-collisional continental extension. These magmas ascend rapidly and cool quickly in a short interval.展开更多
In this paper,the HRTEM lattice fringe micrograph of Caocun No.2 coal was extracted by ArcGIS,the length and orientation of the fringes were calculated,and the rose diagram for the lattice fringe micrograph was drawn ...In this paper,the HRTEM lattice fringe micrograph of Caocun No.2 coal was extracted by ArcGIS,the length and orientation of the fringes were calculated,and the rose diagram for the lattice fringe micrograph was drawn by Matlab.By controlling the segmentation points of each lattice fringe,the coordinates of the segmentation points were processed by a self-programmed Python program,and then a series of curvature characterizations including segmentation angle,cumulative angle and tortuosity were performed for lattice fringes with different lengths.The results show that Caocun No.2 coal is mainly composed of short naphthalene fringes.Lattice fringes with the length ranging from 0.3 nm to 1.14 nm account for more than 90%of the total number of fringes,and the number of polynuclear aromatic rings was 2-4.The direction of lattice fringes is concentrated between 110°and 120°,which indicates well structural orientation of lattice fringes.The number of segment angles ranging from 0°to 20°account for about half of the total,which reflects the structural orientation further.For fringes with the length ranging from 0.3 nm to 1.14 nm,the cumulative angles are mainly concentrated at 4°to 160°.Fringes with the tortuosity in the range of 1.0-1.1 are more than 92%of the total number of fringes.In addition,short fringes have large curvature,which shows significant effects on the placement and frequency of non-six-membered rings and lattice imperfection in the aromatic structure.展开更多
Based on the detailed petrographic study,the characteristics of source region of the Weiya gabbro and tectonic implications were studied.The results show that the gabbroic rock consists mainly of gabbro,with less amou...Based on the detailed petrographic study,the characteristics of source region of the Weiya gabbro and tectonic implications were studied.The results show that the gabbroic rock consists mainly of gabbro,with less amount of ultra-mafic rocks.The ultra-mafic rocks show cumulate texture and are gradually transitional contact with gabbro,indicating that they are cumulate products of parental magma.The ultra-mafic rocks consist mainly of spinel periodite and spinel clinopyroxenite.The former is mainly composed of olivine(65%-70%),spinel(10%-15%),hornblende(5%-10%) and phlogopite(5%-10%);the latter consists mainly of clinopyroxene(70%-80%),spinel(15%-20%) and phlogopite(0-10%),with minor amounts of carbonate(0-2%).No olivine or orthopyroxene is found.The gabbro is composed mainly of clinopyroxene(35%-40%),plagioclase(An 55-65,40%-45%),hornblende(5%-15%),with variable amounts of carbonate(0-5%).Petrographic observations show that the source region of the Weiya gabbroic rock is water-rich due to intensive intra-continental A-type subduction occurring in this region during late Permian to early Triassic.展开更多
One of the significant consequences of the climate change predicted for the next decades is the sea and ocean level rise.The coastal zone of Mohammedia (Morocco),a site of significant socio-economic activeties largely...One of the significant consequences of the climate change predicted for the next decades is the sea and ocean level rise.The coastal zone of Mohammedia (Morocco),a site of significant socio-economic activeties largely open to the Atlantic Ocean,is thus confronted with hydrodynamic agents and a possible sea level rise,whose impacts will result in an immersion of the low topography areas。展开更多
Drinking water supply for the Main Ethiopian Rift (MER) area principally relies on groundwater wells and springs and is characterized by fluoride contamination. New analyses reveal that the F^- geochemical anomaly is ...Drinking water supply for the Main Ethiopian Rift (MER) area principally relies on groundwater wells and springs and is characterized by fluoride contamination. New analyses reveal that the F^- geochemical anomaly is associated with other potentially toxic elements such as As,B,Mo,U,Al,Fe and Mn. Particularly,35%of the 23 investigated groundwater wells and 70%of the 14 hot springs(and展开更多
Landslide is one of the most destructive types of natural hazards on Siwalik Hills where the slope forming materials,such as loose rock blocks,soil, artificial fills and organic materials along with the entrained air ...Landslide is one of the most destructive types of natural hazards on Siwalik Hills where the slope forming materials,such as loose rock blocks,soil, artificial fills and organic materials along with the entrained air and water undergo outward and downward movement.Apart from tectonic activities and the fragile geology of the Siwalik-Himalayas, anthropogenic activities like improper land use,ill planned constructions,deforestation and other展开更多
The Oligocene Afro-Arabian flood volcanic province contains significant silicic pyroclastic rocks (】60000 km^3 constituting up to 20%of the volcanic stratigraphy).Rhyolitic tephras,synchronous with the Afro-Arabian s...The Oligocene Afro-Arabian flood volcanic province contains significant silicic pyroclastic rocks (】60000 km^3 constituting up to 20%of the volcanic stratigraphy).Rhyolitic tephras,synchronous with the Afro-Arabian silicic pyroclastic rocks,are found in Indian Ocean ODP holes 711A.They are geoche-mically akin to the Afro-Arabian silicic pyroclastic rocks.This suggests that the tephras originated from Afro-Arabian silicic eruptions and represents more distal fallout of this volcanism.The temporal coin-展开更多
Landslide is one of the most frequently occurring natural hazards in Manipur which is a tectonically active area.Rainfall-induced landslides are studied along NH-39 to find out the impact of rainfall.Though rainfall-i...Landslide is one of the most frequently occurring natural hazards in Manipur which is a tectonically active area.Rainfall-induced landslides are studied along NH-39 to find out the impact of rainfall.Though rainfall-induced landslides are usually shallow slips in nature and the volume of slip mass is not very large, the damage caused to the properties and infrastructures can be quite serious due to their highly frequent occurrences.NH-39,which is one of the life lines of Manipur,is regularly affected by frequent landslides during rainy season and the frequency is increasing at present as compared to the recent past.Several lands-展开更多
Mount Bambouto is a polygenic stratovolcano of the Cameroon Volcanic Line,built between 21 Ma and 4.5 Ma(Nkouathio et al.,2008).It is situated at about 200 km NE of mount Cameroon,at 09°55′and 10°15′East a...Mount Bambouto is a polygenic stratovolcano of the Cameroon Volcanic Line,built between 21 Ma and 4.5 Ma(Nkouathio et al.,2008).It is situated at about 200 km NE of mount Cameroon,at 09°55′and 10°15′East and,05°25′and 05°50′North.This volcano covers an area of 500 Km^2 and culminates at 2740 m at Meletan hill and bears a collapsed elliptical caldera at the summit(13×8 km).Mount展开更多
The Ediacarian volcanic series from the Lac Ifni sector are composed of a large variety of rocks from basalts and rhyolites to intermediates facies such as andesites,rhyodacites and pyroclastites.All these rocks are i...The Ediacarian volcanic series from the Lac Ifni sector are composed of a large variety of rocks from basalts and rhyolites to intermediates facies such as andesites,rhyodacites and pyroclastites.All these rocks are intruded by dolerite dikes.Secondary processes are reflected by total serpentinization of olivine within basic andesite and by albitization展开更多
文摘This paper reports statistical results of Seismo-Ionospheric Anomalies(SIAs) of the Total Electron Content(TEC) in the Global Ionosphere Map(GIM) associated with 56 M≥6.0 earthquakes in China during 1998—2012.To detect SIA,a quartile-based(i.e.median-based) process is performed.TEC anomalies for the period of earthquakes without being led by magnetic storms about 10 days are further isolated and examined to confirm the SIP existence.Results show that SIA is the TEC significantly decrease in the afternoon period 2—9 days before the earthquakes in China,which is in a good agreement with the SIA appearing before the 12 May 2008 M 8.0 Wenchuan earthquake.
基金supported by the Strategic Priority Research Program of the Chinese Academy of Sciences(XDB41000000)the Fundamental Research Funds for the Central Universities(WK2080000144)。
文摘Araneiforms are spider-like ground patterns that are widespread in the southern polar regions of Mars.A gas erosion process driven by the seasonal sublimation of CO_(2)ice was proposed as an explanation for their formation,which cannot occur on Earth due to the high climatic temperature.In this study,we propose an alternative mechanism that attrib-utes the araneiform formation to the erosion of upwelling salt water from the subsurface,relying on the identification of the first terrestrial analog found in a playa of the Qaidam Basin on the northern Tibetan Plateau.Morphological analysis indicates that the structures in the Qaidam Basin have fractal features comparable to araneiforms on Mars.A numerical model is developed to investigate the araneiform formation driven by the water-diffusion mechanism.The simulation res-ults indicate that the water-diffusion process,under varying ground conditions,may be responsible for the diverse aranei-form morphologies observed on both Earth and Mars.Our numerical simulations also demonstrate that the orientations of the saltwater diffusion networks are controlled by pre-existing polygonal cracks,which is consistent with observations of araneiforms on Mars and Earth.Our study thus suggests that a saltwater-related origin of the araneiform is possible and has significant implications for water searches on Mars.
基金National Natural Science Foundation of China Grant （No. 40602014） by China＇s 973 National Key Research and Development Program （Grant No.2005CB422103 , 2003CB214608）.
文摘The Grains containing Oil Inclusions(GOI)data in currently gas/condensate-beating Jurassic and Cretaceous reservoir sandstones of Well Pen 5(the Mosuowan area of central Junggar Basin,NW China)are generally greater than the empirical threshold line of 5%.This is consistent with the gas-condensate section originally containing a palaeo-oil column.In order to assess the origin of the oil trapped in the oil inclusion and its relationship to the free oil/gas-condensate,a detailed molecular geochemical study was carried out for correlation between the free and inclusion oils.The paleo oil is most likely sourced from the Lower Permian Fengeheng Formation,which generated hydrocarbons primarily during Late Triassic and the oils were later secondarily altered and dysmigrated along faults likely during Late Jurassic-Early Cretaceous.In contrast,the current reservoired oil/gas-condensate mainly derived from the Middle Permian Lower Wuerhe Formation,whose peak generation time last from Late Cretaceous even to the present.This paper showed that integrated oil-bearing fluid inclusion analyses have likely allowed a complex multi-phase charge history to be recognized and resolved with a high degree of confidence.
基金Key Laboratory for the Study of Focused Magmatism and Giant Ore Deposits,MLR
文摘The Ni-Cu-platinum group element sulfide ore deposits of the Kharaelakh Intrusion,Noril′sk Region,Siberia,represent a large concentration of sulfides associated with a small differentiated intrusion formed at the edge of the Siberian Craton in the roots of the Siberian Trap flood basalt.The deposit is associated with an intrusion that occupies a flanking periclinal structure adjacent to the Noril′sk-Kharaelakh Fault.The intrusion is strongly differentiated and comprises taxitic gabbrodolerites,picritic gabbrodolerites,and gabbrodolerites within the main body which in turn forms a chonolith within a sheet-like intrusion that extends laterally to form extensive undifferentiated sills of gabbrodolerite.The intrusion substantially replaces the stratigraphy of the country rocks,and although it appears to have exploited the axis of structures developed in response to transtension,the intrusion has created space by both mechanical dilation of stratigraphy and magmatic replacement of pre-existing sedimentary rocks.The frontal lobes of the main intrusion have complex apophyses of gabrodolerite on a range of scales that demonstrate replacement of the sedimentary rocks and link to the development of an extensive metamorphic halo in the country rocks.This halo is much narrower over the main body of the intrusion,and these observations have implications for the thermal history of the intrusion.Mg-skarns and breccias are developed in the roof of the main body of the intrusion.Within the intrusion,the taxitic rocks contain vesicles and the blebby sulfides developed in the picritic and taxitic gabbrodolerites appear to have a linkage to volatile phases.Cuprous sulfide mineralization developed at the roof of the Kharaelakh Intrusion is associated with metamorphosed and skarn-bearing country rocks,and appears to have been generated by a combination of sulfide fractionation and associated metasomatism.The geological relationships appear consistent with a chonolith model for the development of the differentiated intrusion and mineralization,but the extent of metasmorphism of the country rocks appears to be related to the unusual thickness of gabbrodolerite apophyses at the flanks of the intrusion rather than metamorphism produced by the passage of mafic magma through the intrusion.Variations in disseminated sulfide compositions and metasomatic textures in the skarns are described,and a model is proposed which balances traditional views on the evolution of the magma conduits with the impact of magmatic fluids transported through the magma column(i.e.transmagmatic fluids).The importance of structures in controlling the nature of the conduit,and the resultant small intrusions with excess sulfide is a feature of many other Ni-Cu sulfide deposits including Voisey′s Bay,and it is suggested that the sulfides are more likely to have beentransported from depth into their final resting place rather than developed by in-situ equilibration of sulfide with fresh magma in the chonolith.
基金Project(1212010071012) supported by Guangdong Pangxidong Mineral Prospect Investigation, ChinaProject(41004051) supported by the National Natural Science Foundation of ChinaProject ([2007]038-01-18) supported by Nationwide Mineral Resource Potential Evaluation Projects of Ministry of Land and Resources, China
文摘Distinguishing geochemical anomalies from background is a basic task in exploratory geochemistry. The derivation of geochemical anomalies from stream sediment geochemical data and the decomposition of these anomalies into their component patterns were described. A set of stream sediment geochemical data was obtained for 1 880 km 2 of the Pangxidong area, which is in the southern part of the recently recognized Qinzhou-Hangzhou joint tectonic belt. This belt crosses southern China and tends to the northwest (NE) direction. The total number of collected samples was 7 236, and the concentrations of Ag, Au, Cu, As, Pb and Zn were measured for each sample. The spatial combination distribution law of geochemical elements and principal component analysis (PCA) were used to construct combination models for the identification of combinations of geochemical anomalies. Spectrum-area (S-A) fractal modeling was used to strengthen weak anomalies and separate them from the background. Composite anomaly modeling was combined with fractal filtering techniques to process and analyze the geochemical data. The raster maps of Au, Ag, Cu, As, Pb and Zn were obtained by the multifractal inverse distance weighted (MIDW) method. PCA was used to combine the Au, Ag, Cu, As, Pb, and Zn concentration values. The S-A fractal method was used to decompose the first component pattern achieved by the PCA. The results show that combination anomalies from a combination of variables coincide with the known mineralization of the study area. Although the combination anomalies cannot reflect local anomalies closely enough, high-anomaly areas indicate good sites for further exploration for unknown deposits. On this basis, anomaly and background separation from combination anomalies using fractal filtering techniques can provide guidance for later work.
基金the National Natural Science Foundation of Ghina （Funds Nos.49673189 , 49873018 ） the Doctoral Scientific Program Special Fund of the Education Department （Fund No.98055807） The State Key Laboratory for Mineral Deposits. ...Research, Nanjing University.
文摘The Ailaoshan aquamarine-bearing pegmatites are associated with Proterozoic metamorphic rocks in the southern portion of the Ailaoshan fault-folded complex.The gem-bearing pegmatite mineralization zones of the region occur in areas generally consistent with the regional tectonic trend.The pegmatites are found in metamorphic rocks,migmatites and in the inner/outer contact zones of gneissoid granites. The Rb-Sr isochron drawn for the pegmatites is 26～31 Ma,(i.e.in Himalayan).The homogenization temperatures of melt and liquid inclusions in minerals vary from 185 to 920℃,which are comparable to the inclusions observed in banded migmatites and ptygmatic quartz veins in the surrounding metamorphic rocks. The mineralization fluids of the pegmatite were rich in HCO_3 and CO_2,and their compositional assemblages are comparable to metamorphic fluids.Results of H,O,C,Si etc.isotopic analyses and REE,and Be analyses indicates that the sources of mineralization components that formed the pegmatites are closely associated with metamorphic fluids and the enclosing metamorphic rocks. A pegmatite structure simulation experiment was conducted at high temperature and pressure(840℃and 1,500×105Pa.),with various metamorphic rock samples in a water-rich and volatile-rich environment.When the liquidus was reached,the temperature was gradually decreased at the rate of 5～10℃/day over a time period of three months.SEM energy-dispersive spectrum analyses were performed on the experimental products.A series of pegmatoid textures were observed including zonal texture,megacryst texture,drusy cavities,crystal druses,and vesicular texture along with more than ten types of minerals including plagioclase,microcline,quartz and biotite.Different metamorphic rock melts generated different mineral assemblages.Experiment results revealed that the partial melting of metamorphic rocks could form melts similar to pegmatite magmas. Based upon the geological characteristics,geochemistry,and pegmatite texture simulation experimental results,it is concluded that the mineralization components of Ailaoshan aquamarine-bearing pegmatites came from metamorphic rocks.The petrogenetic model for the origin of pegmatites is related to ultrametamorphism and metamorphic anatexis.
文摘The characteristics of hosted magmas and their petrogenesis based on electron microprobe determination of trace element contents in zircons were discussed. Trace element geochemistry of zircons indicates that zircons in both gabbro and quartz syenite have two-generations. Zircons of the first generations are crystallized in the magma chamber, whereas those of the second generations are formed in supercooling environment. The former is richer in Zr, but poorer in U, Th, Hf and Y. Quartz diorite porphyrite contains zircons that can be distinguished into the early and late generations. Compared to the late generation, the early generation is richer in Zr but poorer in U, Th, Hf and Y. No conspicuous disruption of zircon evolution has been found in both biotite monzogranite and fine-grained granite. However, the content of zircon in fine-grained granite is higher in U, Th and Y and lower in Zr relative to biotite monzogranite without significant contrast in mass fraction ratio of ZrO2 to HfO2 ratio. Such differences in zircon geochemistry of various intrusive phases and the occurrence of the two zircon generations within a single intrusive phase suggest that these phases of magmas are generated from diverse sources during post-collisional continental extension. These magmas ascend rapidly and cool quickly in a short interval.
基金Supported by the National Natural Science Foundation of China(41602177,41802191,41702175)
文摘In this paper,the HRTEM lattice fringe micrograph of Caocun No.2 coal was extracted by ArcGIS,the length and orientation of the fringes were calculated,and the rose diagram for the lattice fringe micrograph was drawn by Matlab.By controlling the segmentation points of each lattice fringe,the coordinates of the segmentation points were processed by a self-programmed Python program,and then a series of curvature characterizations including segmentation angle,cumulative angle and tortuosity were performed for lattice fringes with different lengths.The results show that Caocun No.2 coal is mainly composed of short naphthalene fringes.Lattice fringes with the length ranging from 0.3 nm to 1.14 nm account for more than 90%of the total number of fringes,and the number of polynuclear aromatic rings was 2-4.The direction of lattice fringes is concentrated between 110°and 120°,which indicates well structural orientation of lattice fringes.The number of segment angles ranging from 0°to 20°account for about half of the total,which reflects the structural orientation further.For fringes with the length ranging from 0.3 nm to 1.14 nm,the cumulative angles are mainly concentrated at 4°to 160°.Fringes with the tortuosity in the range of 1.0-1.1 are more than 92%of the total number of fringes.In addition,short fringes have large curvature,which shows significant effects on the placement and frequency of non-six-membered rings and lattice imperfection in the aromatic structure.
基金Projects(40672040,40472042 and 40603008) supported by the National Natural Science Foundation of ChinaProject(2001CB409802) supported by the Major State Basic Research Development Program of China+1 种基金 Project(2005038237) supported by the Postdoctoral Science Foundation of China Project supported by the Opening Foundation of State Key Laboratory of Continental Dynamics,Northwest University
文摘Based on the detailed petrographic study,the characteristics of source region of the Weiya gabbro and tectonic implications were studied.The results show that the gabbroic rock consists mainly of gabbro,with less amount of ultra-mafic rocks.The ultra-mafic rocks show cumulate texture and are gradually transitional contact with gabbro,indicating that they are cumulate products of parental magma.The ultra-mafic rocks consist mainly of spinel periodite and spinel clinopyroxenite.The former is mainly composed of olivine(65%-70%),spinel(10%-15%),hornblende(5%-10%) and phlogopite(5%-10%);the latter consists mainly of clinopyroxene(70%-80%),spinel(15%-20%) and phlogopite(0-10%),with minor amounts of carbonate(0-2%).No olivine or orthopyroxene is found.The gabbro is composed mainly of clinopyroxene(35%-40%),plagioclase(An 55-65,40%-45%),hornblende(5%-15%),with variable amounts of carbonate(0-5%).Petrographic observations show that the source region of the Weiya gabbroic rock is water-rich due to intensive intra-continental A-type subduction occurring in this region during late Permian to early Triassic.
文摘One of the significant consequences of the climate change predicted for the next decades is the sea and ocean level rise.The coastal zone of Mohammedia (Morocco),a site of significant socio-economic activeties largely open to the Atlantic Ocean,is thus confronted with hydrodynamic agents and a possible sea level rise,whose impacts will result in an immersion of the low topography areas。
文摘Drinking water supply for the Main Ethiopian Rift (MER) area principally relies on groundwater wells and springs and is characterized by fluoride contamination. New analyses reveal that the F^- geochemical anomaly is associated with other potentially toxic elements such as As,B,Mo,U,Al,Fe and Mn. Particularly,35%of the 23 investigated groundwater wells and 70%of the 14 hot springs(and
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