We use interferometric synthetic aperture radar (InSAR) and broadband seismic waveform data to estimate a source model of the 11th July, 2004 M W 6.2 Zhongba earthquake, Tibet of China. This event occurred within th...We use interferometric synthetic aperture radar (InSAR) and broadband seismic waveform data to estimate a source model of the 11th July, 2004 M W 6.2 Zhongba earthquake, Tibet of China. This event occurred within the seismically active zone of southwestern Tibetan Plateau where the east-west extension of the upper crust is observed. Because of limitations in one pair of InSAR data available, there are trade-offs among centroid depth, rupture area and amount of slip. Available seismic data tightly constrain the focal mechanism and centroid depth of the earthquake but not the horizontal location. Together, two complementary data sets can be used to identify the actual fault plane, better constrain the slip model and event location. We first use regional seismic waveform to estimate point source mechanism, then InSAR data is used to obtain better location. Finally, a joint inversion of teleseismic P-waves and InSAR data is performed to obtain a distributed model. Our preferred point source mechanism indicates a seismic moment of ~2.2×10 18 N·m (~M W 6.2), a fault plane solution of 171° (342 ° )/42 ° (48 ° )/-83 ° (-97 ° ), corresponding to strike/dip/rake, and a depth of 11 km. The fault plane with strike of 171 ? and dip of 42° is identified as the ruptured fault with the aid of InSAR data. The preferred source model features compact area of slips between depth of 5–11 km and 10 km along strike with maximum slip amplitude of about 1.5 m.展开更多
Principal component analysis(PCA)was employed to determine the implications of geochemical and isotopic data from Cenozoic volcanic activities in the Southeast Asian region,including China(South China Sea(SCS),Hainan ...Principal component analysis(PCA)was employed to determine the implications of geochemical and isotopic data from Cenozoic volcanic activities in the Southeast Asian region,including China(South China Sea(SCS),Hainan Island,Fujian-Zhejiang coast,Taiwan Island),and parts of Vietnam and Thailand.We analyzed 15 trace element indicators and 5 isotopic indicators for 623 volcanic rock samples collected from the study region.Two principal components(PCs)were extracted by PCA based on the trace elements and Sr-Nd-Pb isotopic ratios,which probably indicate an enriched oceanic island basalt-type mantle plume and a depleted mid-ocean ridge basalt-type spreading ridge.The results show that the influence of the Hainan mantle plume on younger volcanic activities(<13 Ma)is stronger than that on older ones(>13 Ma)at the same location in the Southeast Asian region.PCA was employed to verify the mantle-plume-ridge interaction model of volcanic activities beneath the expansion center of SCS and refute the hypothesis that the tension of SCS is triggered by the Hainan plume.This study reveals the efficiency and applicability of PCA in discussing mantle sources of volcanic activities;thus,PCA is a suitable research method for analyzing geochemical data.展开更多
We analyze co-seismic displacement field of the 26 December 2004, giant Sumatra–Andaman earthquake derived from Global Position System observations,geological vertical measurement of coral head, and pivot line observ...We analyze co-seismic displacement field of the 26 December 2004, giant Sumatra–Andaman earthquake derived from Global Position System observations,geological vertical measurement of coral head, and pivot line observed through remote sensing. Using the co-seismic displacement field and AK135 spherical layered Earth model, we invert co-seismic slip distribution along the seismic fault. We also search the best fault geometry model to fit the observed data. Assuming that the dip angle linearly increases in downward direction, the postfit residual variation of the inversed geometry model with dip angles linearly changing along fault strike are plotted. The geometry model with local minimum misfits is the one with dip angle linearly increasing along strike from 4.3oin top southernmost patch to 4.5oin top northernmost path and dip angle linearly increased. By using the fault shape and geodetic co-seismic data, we estimate the slip distribution on the curved fault. Our result shows that the earthquake ruptured *200-km width down to a depth of about 60 km.0.5–12.5 m of thrust slip is resolved with the largest slip centered around the central section of the rupture zone78N–108N in latitude. The estimated seismic moment is8.2 9 1022 N m, which is larger than estimation from the centroid moment magnitude(4.0 9 1022 N m), and smaller than estimation from normal-mode oscillation data modeling(1.0 9 1023 N m).展开更多
P-and SV-wave dispersion and attenuation have been extensively investigated in saturated poroelastic media with aligned fractures.However,there are few existing models that incorporate the multiple wave attenuation me...P-and SV-wave dispersion and attenuation have been extensively investigated in saturated poroelastic media with aligned fractures.However,there are few existing models that incorporate the multiple wave attenuation mechanisms from the microscopic scale to the macroscopic scale.Hence,in this work,we developed a unified model to incorporate the wave attenuation mechanisms at different scales,which includes the microscopic squirt flow between the microcracks and pores,the mesoscopic wave-induced fluid flow between fractures and background(FB-WIFF),and the macroscopic Biot's global flow and elastic scattering(ES)from the fractures.Using Tang's modified Biot's theory and the mixed-boundary conditions,we derived the exact frequency-dependent solutions of the scattering problem for a single penny-shaped fracture with oblique incident P-and SV-waves.We then developed theoretical models for a set of aligned fractures and randomly oriented fractures using the Foldy approximation.The results indicated that microcrack squirt flow considerably influences the dispersion and attenuation of P-and SV-wave velocities.The coupling effects of microcrack squirt flow with the FB-WIFF and ES of fractures cause much higher velocity dispersion and attenuation for P waves than for SV waves.Randomly oriented fractures substantially reduce the attenuation caused by the FB-WIFF and ES,particularly for the ES attenuation of SV waves.Through a comparison with existing models in the limiting cases and previous experimental measurements,we validated our model.展开更多
The hydraulic testing of pre-existing fractures(HTPF)is one of the most promising in situ stress measurement methods,particularly for three-dimensional stress tensor determination.However,the stress tensor determinati...The hydraulic testing of pre-existing fractures(HTPF)is one of the most promising in situ stress measurement methods,particularly for three-dimensional stress tensor determination.However,the stress tensor determination based on the HTPF method requires at least six tests or a minimum of 14-15 tests(under different conditions)for reliable results.In this study,we modified the HTPF method by considering the shear stress on each pre-existing fracture,which increased the number of equations for the stress tensor determination and decreased the number of tests required.Different shear stresses were attributed to different fractures by random sampling;therefore,the stress tensors were obtained by searching for the optimal solution using the least squares criterion based on the Monte Carlo method.Thereafter,we constrained the stress tensor based on the tensile strength criterion,compressive strength criterion,and vertical stress constraints.The inverted stress tensors were presented and analyzed based on the tensorial nature of the stress using the Euclidean mean stress tensor.Two stress-measurement campaigns in Weifang(Shandong Province,China)and Mercantour road tunnel(France)were implemented to highlight the validity and efficiency of the modified HTPF(M-HTPF)method.The results showed that the M-HTPF method can be applied for stress tensor inversion using only three to four tests on pre-existing fractures,neglecting the stress gradient.The inversion results were confined to relatively small distribution dispersions and were significantly reliable and stable due to the shear stresses on the fractures and the stress constraints employed.The M-HTPF method is highly feasible and efficient for complete stress tensor determination in a single borehole.展开更多
The dynamics of long-wavelength(kθ<1.4 cm^(-1)),broadband(20 kHz–200 kHz)electron temperature fluctuations(Te/Te)of plasmas in gas-puff experiments are observed for the first time in HL-2A tokamak.In a relatively...The dynamics of long-wavelength(kθ<1.4 cm^(-1)),broadband(20 kHz–200 kHz)electron temperature fluctuations(Te/Te)of plasmas in gas-puff experiments are observed for the first time in HL-2A tokamak.In a relatively low density(ne(0)■0.91×10^(19)m^(-3)–1.20×10^(19)m^(-3))scenario,after gas-puffing the core temperature increases and the edge temperature drops.On the contrary,temperature fluctuation drops at the core and increases at the edge.Analyses show the non-local emergence is accompanied with a long radial coherent length of turbulent fluctuations.While in a higher density(ne(0)?1.83×10^(19)m^(-3)–2.02×10^(19)m^(-3))scenario,the phenomena are not observed.Furthermore,compelling evidence indicates that E×B shear serves as a substantial contributor to this extensive radial interaction.This finding offers a direct explanatory link to the intriguing core-heating phenomenon witnessed within the realm of non-local transport.展开更多
The concentrations of two fresh Chinese coals (lignitie and fatty coal ) from dif-ferent geological origin and the corresponding fly and bottom ashes were determined us-ing inductively coupled plasma mass spectrometry...The concentrations of two fresh Chinese coals (lignitie and fatty coal ) from dif-ferent geological origin and the corresponding fly and bottom ashes were determined us-ing inductively coupled plasma mass spectrometry(ICP-MS). The ranges and means of concentrations of these elemennts were given. Based on the combustion simulating ex-periment in the one-dismensional boiler, the contents of REE (rare-earth element) of 18 samples in lignite, fatty coal and their fly and bottom ashes in different combustion condi-tion were determined, and geochemical feature of REE were analyzed.展开更多
We analyzed the elemental concentrations and the isotopic compositions of helium and argon in Cambrian to Jurrassic aged Gastropod, Ammonite and Trilobite fossils in order to examine variation in these gases through t...We analyzed the elemental concentrations and the isotopic compositions of helium and argon in Cambrian to Jurrassic aged Gastropod, Ammonite and Trilobite fossils in order to examine variation in these gases through time. Fossil samples yielded He and Ar isotopic ratios close to the present day atmospheric values, but also indicated some addition of a radiogenic component. We compared the results to theoretical values calculated from a mathematical model of Earth’s atmosphere assuming mantle degassing. Results from our mathmatical models showed that the 40Ar/36Ar ratio of Earth’s atmosphere increased rapidly after the formation of the Earth, but has been almost identical to the present day value for the last 1 Ga. For atmospheric helium, model results were consistent with present day atmospheric values, assuming complete helium degassing from the continental crust into the atmosphere. The model suggests that the atmospheric 3He/4He ratio has remained relatively constant for the last 0.1 Ga. Given the similarity between present day and ancient He and Ar isotopic ratios, we conclude that the corresponding ratios measured in ancient fossil material may partially reflect composition of the ancient atmosphere and are not necessarily due to contamination by the present day atmosphere.展开更多
Using the latest results of seismic tomography, we studied the deep tectonic settings of the moderate and strong earthquakes in Anhui Province and its neighboring areas (28°~39°N, 112°~124°E). Th...Using the latest results of seismic tomography, we studied the deep tectonic settings of the moderate and strong earthquakes in Anhui Province and its neighboring areas (28°~39°N, 112°~124°E). The results are as follows: (1) There exists a certain correlation between the location of moderate-strong earthquake, the geologic structure of the surface and the partitioning of active tectonic elements with the upper-crust velocity structure. Most earthquakes recording M≥6.0 occur in high-velocity zones or in the transitional areas between high-velocity and low-velocity zones in the upper crust. Seismicity in the low-velocity zone has a lesser impact. Earthquakes occuring in the high-velocity zone are distributed mainly in the velocity variation area. The boundary belts and the interior of the North China plain fault block are the main active sites of moderate-strong earthquakes. Beneath the fault basins in the western and northern sides of the block, the upper crust is characterized by a wide discontinuous distribution in the low-velocity zone, and in the transition zone from the low- to high velocities, the moderate strong seismicity shows a zonal distribution where active faults are developed. The NW-extension Zhoukou-Hefei-Xuancheng low-velocity zone separates the high-velocity zones of Dabieshan Mountains and west Shandong-Anhui, and moderate-strong earthquakes on its northern side bordering the high-velocity zones are relatively frequent. This low-velocity zone is probably an important and deeply structured boundary between the North China and the South China tectonic provinces. (2) The frequent moderate-strong earthquake recorded in the past and the recent small earthquake activities in the Huoshan-Lu’an area are the result of a low-velocity zone in the middle crust beneath the central part of Dabieshan and the two sets of deep faults that cut through the crust.(3) In terms of deep structures, the distribution of moderate-strong earthquake in Anhui Province has an obvious regional feature. Based on historical earthquake recurrence intervals and analogue principles of deep seismogenic tectonics, the potential earthquake risk zones recording M_S5.0 in Anhui Province are determined.展开更多
Coral samples collected from the waters off the Leizhou Peninsula, the Hainan Island and the Yongxing Island of the Xisha Islands were analyzed by thermal ionization mass spectrometry (TIMS) and multi-collector induct...Coral samples collected from the waters off the Leizhou Peninsula, the Hainan Island and the Yongxing Island of the Xisha Islands were analyzed by thermal ionization mass spectrometry (TIMS) and multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS) for their U-Th systematics. Their uranium contents are mostly lower than 3μg/g, and the δ+{234}U(T) values are within the range of 150±5. X-ray diffraction analysis showed that the corals are all composed of aragonite. This demonstrates that the corals determined have maintained a close system for 7000 years and their skeletons bear much information about the primitive tropical marine environment. The highly precise age sequence of the corals determined has revealed that there occurred three phases of high sea level in the South China Sea waters, which are dated at 6799-6307 a B.P., 4472-4285 a B.P. and 1279-1012 a B.P., respectively. The three phases lasted 492 a, 187 a and 267 a, respectively. These three phases of high sea level are corresponding to the warm environments that had appeared in China during the Megathermal Period and the Medieval Warm Period in the past ten thousand years.展开更多
The Shaxi porphyry copper (gold) deposits are a typical example of porphyry copper deposits associated with diorite in eastern China. Quartz diorite, which hosts the deposits, has a Rb-Sr isochron age of 127.9 ± ...The Shaxi porphyry copper (gold) deposits are a typical example of porphyry copper deposits associated with diorite in eastern China. Quartz diorite, which hosts the deposits, has a Rb-Sr isochron age of 127.9 ± 1.6 Ma. Geochemically, the rock is rich in alkalis (especially sodium), light rare earth elements (LREE) and large-ion lithophile elements (LILE), and has a relatively low initial strontium isotopic ratio (Isr=0.7058); thus it is the product of differentiation of crust-mantle mixing source magma. The model of alteration and mineralization zoning is similar to the Hollister (1974) diorite model. The ore fluids have a relatively high salinity and contain significant amounts of CO2, Ca2+, Na+ and ***CI?. The homogenization temperatures of fluid inclusions for the main mineralization stage range from 280 to 420°C, the δ18O values of the ore fluids vary from 3.51 to 5.52 %, the δD values are in the range between ?82.4 and ?59.8 %, the δ34S values of sulphides vary from ?0.3 to 2.49 %, and the δ13C values of CO2 in inclusions range between ?2.66 and ?6.53 %. Isotope data indicate that the hydrothermal ore fluids and ore substances of the Shaxi porphyry copper (gold) deposits were mainly derived from magmatic systems.展开更多
Dongguan (东莞) City, located in the Pearl River Delta, South China, is famous for its rapid industrialization in the past 30 years. A total of 90 topsoil samples have been collected from agricultural fields, includ...Dongguan (东莞) City, located in the Pearl River Delta, South China, is famous for its rapid industrialization in the past 30 years. A total of 90 topsoil samples have been collected from agricultural fields, including vegetable and orchard soils in the city, and eight heavy metals (As, Cu, Cd, Cr, Hg, Ni, Pb, and Zn) and other items (pH values and organic matter) have been analyzed, to evaluate the influence of anthropic activities on the environmental quality of agricultural soils and to identify the spatial distribution of trace elements and possible sources of trace elements. The elements Hg, Pb, and Cd have accumulated remarkably here, incomparison with the soil background content of elements in Guangdong (广东) Province. Pollution is more serious in the western plain and the central region, which are heavily distributed with industries and rivers. Multivariate and geostatistical methods have been applied to differentiate the influences of natural processes and human activities on the pollution of heavy metals in topsoils in the study area. The results of cluster analysis (CA) and factor analysis (FA) show that Ni, Cr, Cu, Zn, and As are grouped in factor F1, Pb in F2, and Cd and Hg in F3, respectively. The spatial pattern of the three factors may be well demonstrated by geostatistical analysis. It is shown that the first factor could be considered as a natural source controlled by parent rocks. The second factor could be referred to as "industrial and traffic pollution sources". The source of the third factor is mainly controlled by long-term anthropic activities, as a consequence of agricultural activities, fossil fuel consumption, and atmospheric deposition.展开更多
Leaching is an important way of separation of trace elements from coal. Based on leaching experiments, the content of trace elements separated out from coal is related to their existing state and content in coal, the ...Leaching is an important way of separation of trace elements from coal. Based on leaching experiments, the content of trace elements separated out from coal is related to their existing state and content in coal, the duration of leaching process, temperature of leaching liquor and its acidity and basicity. The higher the temperature of leaching liquor and the longer the leaching time, the higher the contents of separated trace elements will be. In the course of leaching, the pH values of leaching liquors change and different trace elements are affected differently by the pH values.展开更多
A systematic sedimentological and chronological study of typical Paleogene basins in eastcentral Tibet suggests that the depositional characteristics of extensively developed huge-bedded, purplish-red coarse clastic r...A systematic sedimentological and chronological study of typical Paleogene basins in eastcentral Tibet suggests that the depositional characteristics of extensively developed huge-bedded, purplish-red coarse clastic rocks formed in a tectonic setting of regional thrusting and strike-slipping represent a typical dry and hot subaerial alluvial fan environment formed in a proximal and rapidaccumulating sediment body in debris flows and a fan-surface braided river. Combining results from basin-fill sequences, sequences of coarse clastic rocks, fauna and sporo-pollen associations and thermochronological data, it is conduded that the coarse clastic rocks formed in the period of 54.2- 24.1 Ma, nearly coeval with the formation of Paleogene basins in the northern (Nangqen-Yushu thrust belt), middle (Batang-Lijiang fault belt), and disintegration of large basins in the southern (LanpingSimao fold belt) segments of Tibet. The widespread massive-bedded coarse clastic rocks, fold thrusting and strike-slip, thrust shortening, and igneous activities in the Paleogene basins of eastcentral Tibet indicate that an early diachronous tectonic uplift might have occurred in the Tibetan Plateau from Middle Eocene to Oligocene, related to the initial stage of collision of the Indian and Asian plates.展开更多
In the process of combustion of coal organic and inorganic materials in it will undergo a complex variation. Part of them will become volatiles and, together with coal smoke, enter into atmosphere, some will remain in...In the process of combustion of coal organic and inorganic materials in it will undergo a complex variation. Part of them will become volatiles and, together with coal smoke, enter into atmosphere, some will remain in micro-particulates such as ash and dust and find their way into atmosphere in the form of solid particles, and the rest will be retained in ash and slag. Coal ashes are the residues of organic and inorganic substances in coal left after coal combustion and the composition of coal ashes is dependent on that of minerals and organic matter in coal. This paper deals with the chemical composition of coal ashes, the distribution of trace elements in them and their petrological characteristics, and also studies the relationship between the yield of coal ashes and the distribution of trace elements. In addition, a preliminary study is also undertaken on the factors that affect the chemical composition of coal ashes. As viewed from the analyses of coal ash samples collected from the Yanzhou mining district, it can be seen clearly that coal ashes from the region studied are composed chiefly of crystalline materials, glassy materials and uncombusted organic matter and the major chemical compositions are SiO 2, Al 2O 3, Fe 2O 3, and CaO, as well as minor amounts of SO 3, P 2O 5, Na 2O, K 2O and TiO 2. During the combustion of coal, its trace elements will be redistributed and most of them are enriched in coal ashes. At the same time, the concentrations of the trace elements in flying ash are much higher than those of bottom ash, i.e., with decreasing particle-size of coal ashes their concentrations will become higher and higher. So the contents of trace elements are negatively proportional to the particle-size of coal ashes. There has been found a positive correlation between the trace elements Th, V, Zn, Cu and Pb and the yield of coal ashes while a negative correlation between Cl and the yield of coal ashes.展开更多
The weight of evidence (WofE) model has been widely used for mineral potential mapping. During the conversion of a multiclass map into a binary map a lot of mineralization information is artificially added or lost b...The weight of evidence (WofE) model has been widely used for mineral potential mapping. During the conversion of a multiclass map into a binary map a lot of mineralization information is artificially added or lost because the generalization of the class within the cumulative distance interval to a linear feature is based on a maximum contrast, which matches a cumulative distance interval. Additionally, some categorical data evidence cannot be generated by this method because a maximum contrast does not exist. In this article, an alternative (W^+ -W^- )-based WofE model is proposed. In this model, the "(W^+ -W^- ) greater than zero or not" is used as a criterion to reclassify the corresponding categorical class into a presence or absence class to convert a multielass map into a binary map. This model can be applied to both categorical data and successive data. The latter can be operated as categorical data. The Wt and W^- of the generated binary maps can be recalculated, and several binary maps can be integrated on the condition that the reclassified binary evidences are conditionally independent of each other. This method effectively reduces artificial data and both nominal and categorical data can be operated. A ease study of gold potential mapping in the Abitibi area, Ontario, Canada, shows that the gold potential map by the (W^+ -W^- ) model displays a smaller potential area but a higher posterior probability (POP), whereas the potential map by the traditional (W^+ - W^- ) model exhibits a larger potential area but a lower POP.展开更多
In China, most directions of river flowing are from west to east. During historic period, since the water traffic played an important role, it was very important to form a cross-horizontal net of water carriage route....In China, most directions of river flowing are from west to east. During historic period, since the water traffic played an important role, it was very important to form a cross-horizontal net of water carriage route. Canals should be dug so as to make up the lack of north-south river. Tongji Grand Canal, dug in the first year of Daye (605 A.D.) in the Sui Dynasty, was the important component of north-south system of Grand Canals in China. It promoted economic and social development of the Sui, Tang and Song dynasties (605 A.D.-1279 A.D.). As Tongji Canal (i.e. Tongji Grand Canal) flowed across the Huaibei Plain, which is aggraded by abundant mud and sand deposit resulted from the Huanghe (Yellow) River flooding, many traces (such as old channel) and human culture heritages were buried under mud-sand. Tongji Canal was silted up, and disappeared in the Jin Dynasty (1115 A.D.-1234 A.D.). From then on, there were many different stories about the flowing route of the canal in historical literature. Based on space-bone and air-bone remote sensing imagery, we attempt to search the old channel of Tongji Canal, and supplement historical record. The paper discusses transformation process of Tongji Canal’s traffic function, and resumptively summarizes the reasons of the transformation, which results from synthetic function of physical geographical, political, economic, and social conditions.展开更多
The Cuobuzha high-Cr chromitites in the western segment of Yarlung Zangbo Suture Zone of Tibet are mainly hosted in the harzburgites as massive type, which are characterized by high concentrations of platinum group el...The Cuobuzha high-Cr chromitites in the western segment of Yarlung Zangbo Suture Zone of Tibet are mainly hosted in the harzburgites as massive type, which are characterized by high concentrations of platinum group elements(PGE) ranging from 380 to 577 ppb, and low Pd/Ir ratios(<0.1). In mid-ocean ridge basalts(MORB)-normalized spidergrams, chromites of the Cuobuzha chromitites are depleted in Al, Ga, V, Mg and Zn, and enriched in Mn and Cr, sharing similar patterns with those of ophiolitic boninites in the Bonin and Thetford Mines. Approximately 20 platinum group mineral(PGM) grains were discovered from the samples, including laurite, erlichmanite, Os-Fe alloy, cuproiridsite, and irarsite. The PGM assemblages indicate that sulfur fugacity was initially low enough to allow the precipitation of Os-Fe alloy and increased thereafter, with the fall in temperature. Primary Fe-Ni and Fe-Cr alloys, which are stable in a highly reduced environment, occur as inclusions within chromites or clinopyroxenes. Calculated results show that the parental magma has an intimate affinity with boninites. Based on our observations, a model is proposed wherein the Cuobuzha chromitites contain high-pressure and low-pressure chromites. Low-pressure chromites were formed via reaction between boninitic melts and peridotites, during which the high-pressure chromites hosting highly reduced minerals were mobilized by melts and were reallocated to podiform chromitites.展开更多
The biogenic silica (BSi) ,total organic carbon (TOC) ,total nitrogen (TN) and grain size were analyzed with a gravity core (3250-6) collected from the mud area in the north East China Sea.The average deposition rate ...The biogenic silica (BSi) ,total organic carbon (TOC) ,total nitrogen (TN) and grain size were analyzed with a gravity core (3250-6) collected from the mud area in the north East China Sea.The average deposition rate of the upper core was about 0.078cm yr1based on the results of 210Pbex.The mean grain size increased with depth in general.The frequency distribution of grain size showed that two marked changes of deposition environment occurred at 30 cm and 50 cm depths (about 1550 AD and 1300 AD,respectively) .The variations of BSi and TOC indicated two distinct major periods of primary productivity over the past 800 years:a stage of low primary productivity corresponding to weak upwelling and low nutrient input below 30 cm depth (about 1200-1550 AD) ,and a stage of high primary productivity with strong currents and upwelling above 30 cm depth (about 1550-1950 AD) .The stage with high primary productive appeared to be due to the northward-expanded muddy area caused by strong Asian Winter Monsoon and enhanced Yellow Sea Warm Current in winter.In conclusion,the BSi and TOC in the muddy sediments,the symbols of marine primary productivity,can be then used to investigate the evolution history of currents and relative climate change in the offshore areas.展开更多
Weights of evidence (WofE) is an artificial intelligent method for integration of information from diverse sources for predictive purpose in supporting decision making. This method has been commonly used to predict ...Weights of evidence (WofE) is an artificial intelligent method for integration of information from diverse sources for predictive purpose in supporting decision making. This method has been commonly used to predict point events by integrating point training layer and binary or ternary evidential layers (multiclass evidence less commonly used). Omnibus weights of evidence integrates fuzzy training layer and diverse evidential layers. This method provides new features in comparison with the ordinary Wore method. This new method has been implemented in a geographic information system-geophysical data analysis system and the method includes the following contents: (1) dual fuzzy weights of evidence (DFWofE), in which training layer and evidential layers can be treated as fuzzy sets. DFWofE can be used to predict not only point events but also area or line events. In this model a fuzzy training layer can be defined based on point, line, and areas using fuzzy membership function; and (2) degree-of-exploration model for WorE is implemented through building a degree of exploration map. This method can be used to assess possible spatial correlations between the degree of exploration and potential evidential layers. Importantly, it would also make it possible to estimate undiscovered resources, if the degree of exploration map is combined with other models that predict where such resources are most likely to occur. These methods and relevant systems were vafidated using a case study of mineral potential prediction in Gejiu (个旧) mineral district, Yunnan ( 云南), China.展开更多
基金study was supported jointly by National Natural Science Foundation of China (Nos.40821160549 and 41074032)CAS Knowledge Innovation Program (No. KZCX2-YW-116-1)Joint Seismological Science Fundation of China(Nos.200808078 and 200708035)
文摘We use interferometric synthetic aperture radar (InSAR) and broadband seismic waveform data to estimate a source model of the 11th July, 2004 M W 6.2 Zhongba earthquake, Tibet of China. This event occurred within the seismically active zone of southwestern Tibetan Plateau where the east-west extension of the upper crust is observed. Because of limitations in one pair of InSAR data available, there are trade-offs among centroid depth, rupture area and amount of slip. Available seismic data tightly constrain the focal mechanism and centroid depth of the earthquake but not the horizontal location. Together, two complementary data sets can be used to identify the actual fault plane, better constrain the slip model and event location. We first use regional seismic waveform to estimate point source mechanism, then InSAR data is used to obtain better location. Finally, a joint inversion of teleseismic P-waves and InSAR data is performed to obtain a distributed model. Our preferred point source mechanism indicates a seismic moment of ~2.2×10 18 N·m (~M W 6.2), a fault plane solution of 171° (342 ° )/42 ° (48 ° )/-83 ° (-97 ° ), corresponding to strike/dip/rake, and a depth of 11 km. The fault plane with strike of 171 ? and dip of 42° is identified as the ruptured fault with the aid of InSAR data. The preferred source model features compact area of slips between depth of 5–11 km and 10 km along strike with maximum slip amplitude of about 1.5 m.
基金Supported by the State Key Laboratory of Marine Environmental Science Visiting Fellowship(No.MELRS2233)the State Key Laboratory of Marine Geology,Tongji University(No.MGK202302)+4 种基金the Innovation Group Project of Southern Marine Science and Engineering Guangdong Laboratory(Zhuhai)(No.311021003)the Zhujiang Talent Project Foundation of Guangdong Province(No.2017ZT07Z066)the Fundamental Research Funds for the Central Universities,Sun Yat-sen University(Nos.22qntd2101,2021qntd23)the Major Projects of the National Natural Science Foundation of China(Nos.41790465,41590863)the National Natural Science Foundation of China(Nos.42102333,41806077,41904045)。
文摘Principal component analysis(PCA)was employed to determine the implications of geochemical and isotopic data from Cenozoic volcanic activities in the Southeast Asian region,including China(South China Sea(SCS),Hainan Island,Fujian-Zhejiang coast,Taiwan Island),and parts of Vietnam and Thailand.We analyzed 15 trace element indicators and 5 isotopic indicators for 623 volcanic rock samples collected from the study region.Two principal components(PCs)were extracted by PCA based on the trace elements and Sr-Nd-Pb isotopic ratios,which probably indicate an enriched oceanic island basalt-type mantle plume and a depleted mid-ocean ridge basalt-type spreading ridge.The results show that the influence of the Hainan mantle plume on younger volcanic activities(<13 Ma)is stronger than that on older ones(>13 Ma)at the same location in the Southeast Asian region.PCA was employed to verify the mantle-plume-ridge interaction model of volcanic activities beneath the expansion center of SCS and refute the hypothesis that the tension of SCS is triggered by the Hainan plume.This study reveals the efficiency and applicability of PCA in discussing mantle sources of volcanic activities;thus,PCA is a suitable research method for analyzing geochemical data.
基金supported by the Special Fund of Fundamental Scientific Research Business Expense for Higher School of Central Government(Projects for creation teams ZY20110101)NSFC 41090294talent selection and training plan project of Hebei university
文摘We analyze co-seismic displacement field of the 26 December 2004, giant Sumatra–Andaman earthquake derived from Global Position System observations,geological vertical measurement of coral head, and pivot line observed through remote sensing. Using the co-seismic displacement field and AK135 spherical layered Earth model, we invert co-seismic slip distribution along the seismic fault. We also search the best fault geometry model to fit the observed data. Assuming that the dip angle linearly increases in downward direction, the postfit residual variation of the inversed geometry model with dip angles linearly changing along fault strike are plotted. The geometry model with local minimum misfits is the one with dip angle linearly increasing along strike from 4.3oin top southernmost patch to 4.5oin top northernmost path and dip angle linearly increased. By using the fault shape and geodetic co-seismic data, we estimate the slip distribution on the curved fault. Our result shows that the earthquake ruptured *200-km width down to a depth of about 60 km.0.5–12.5 m of thrust slip is resolved with the largest slip centered around the central section of the rupture zone78N–108N in latitude. The estimated seismic moment is8.2 9 1022 N m, which is larger than estimation from the centroid moment magnitude(4.0 9 1022 N m), and smaller than estimation from normal-mode oscillation data modeling(1.0 9 1023 N m).
基金This work was supported by the Laoshan National Laboratory Science and Technology Innovation Project(No.LSKJ202203407)the National Natural Science Foundation of China(Grant Nos.42174145,41821002,42274146)+1 种基金Guangdong Provincial Key Laboratory of Geophysical High-resolution Imaging Technology(2022B1212010002)Shenzhen Stable Support Plan Program for Higher Education Institutions(20220815110144003).
文摘P-and SV-wave dispersion and attenuation have been extensively investigated in saturated poroelastic media with aligned fractures.However,there are few existing models that incorporate the multiple wave attenuation mechanisms from the microscopic scale to the macroscopic scale.Hence,in this work,we developed a unified model to incorporate the wave attenuation mechanisms at different scales,which includes the microscopic squirt flow between the microcracks and pores,the mesoscopic wave-induced fluid flow between fractures and background(FB-WIFF),and the macroscopic Biot's global flow and elastic scattering(ES)from the fractures.Using Tang's modified Biot's theory and the mixed-boundary conditions,we derived the exact frequency-dependent solutions of the scattering problem for a single penny-shaped fracture with oblique incident P-and SV-waves.We then developed theoretical models for a set of aligned fractures and randomly oriented fractures using the Foldy approximation.The results indicated that microcrack squirt flow considerably influences the dispersion and attenuation of P-and SV-wave velocities.The coupling effects of microcrack squirt flow with the FB-WIFF and ES of fractures cause much higher velocity dispersion and attenuation for P waves than for SV waves.Randomly oriented fractures substantially reduce the attenuation caused by the FB-WIFF and ES,particularly for the ES attenuation of SV waves.Through a comparison with existing models in the limiting cases and previous experimental measurements,we validated our model.
基金supported by the National Natural Science Foundation of China(Grant No.42174118)a research grant(Grant No.ZDJ 2020-7)from the National Institute of Natural Hazards,Ministry of Emergency Management of China.
文摘The hydraulic testing of pre-existing fractures(HTPF)is one of the most promising in situ stress measurement methods,particularly for three-dimensional stress tensor determination.However,the stress tensor determination based on the HTPF method requires at least six tests or a minimum of 14-15 tests(under different conditions)for reliable results.In this study,we modified the HTPF method by considering the shear stress on each pre-existing fracture,which increased the number of equations for the stress tensor determination and decreased the number of tests required.Different shear stresses were attributed to different fractures by random sampling;therefore,the stress tensors were obtained by searching for the optimal solution using the least squares criterion based on the Monte Carlo method.Thereafter,we constrained the stress tensor based on the tensile strength criterion,compressive strength criterion,and vertical stress constraints.The inverted stress tensors were presented and analyzed based on the tensorial nature of the stress using the Euclidean mean stress tensor.Two stress-measurement campaigns in Weifang(Shandong Province,China)and Mercantour road tunnel(France)were implemented to highlight the validity and efficiency of the modified HTPF(M-HTPF)method.The results showed that the M-HTPF method can be applied for stress tensor inversion using only three to four tests on pre-existing fractures,neglecting the stress gradient.The inversion results were confined to relatively small distribution dispersions and were significantly reliable and stable due to the shear stresses on the fractures and the stress constraints employed.The M-HTPF method is highly feasible and efficient for complete stress tensor determination in a single borehole.
基金Project supported by the National Key Research and Development Program of China(Grant No.2017YFE0301203)the Innovation Program of Southwestern Institute of Physics(Grant No.202301XWCX001)+2 种基金the Sichuan Science and Technology Program(Grant Nos.2023ZYD0014 and 2021YFSY0044)the National Natural Science Foundation of China(Grant No.12175055)the Shenzhen Municipal Collaborative Innovation Technology Program-International Science and Technology Cooperation Project(Grant No.GJHZ20220913142609017)。
文摘The dynamics of long-wavelength(kθ<1.4 cm^(-1)),broadband(20 kHz–200 kHz)electron temperature fluctuations(Te/Te)of plasmas in gas-puff experiments are observed for the first time in HL-2A tokamak.In a relatively low density(ne(0)■0.91×10^(19)m^(-3)–1.20×10^(19)m^(-3))scenario,after gas-puffing the core temperature increases and the edge temperature drops.On the contrary,temperature fluctuation drops at the core and increases at the edge.Analyses show the non-local emergence is accompanied with a long radial coherent length of turbulent fluctuations.While in a higher density(ne(0)?1.83×10^(19)m^(-3)–2.02×10^(19)m^(-3))scenario,the phenomena are not observed.Furthermore,compelling evidence indicates that E×B shear serves as a substantial contributor to this extensive radial interaction.This finding offers a direct explanatory link to the intriguing core-heating phenomenon witnessed within the realm of non-local transport.
基金Supported by the National Natural Science Key Foundation of China (40133010) Educational Natural Science Foundation of Anhui (2004kj114) Natural Science Foundation of Anhui University of Science and Technology for Ph.D to Research(DG414)
文摘The concentrations of two fresh Chinese coals (lignitie and fatty coal ) from dif-ferent geological origin and the corresponding fly and bottom ashes were determined us-ing inductively coupled plasma mass spectrometry(ICP-MS). The ranges and means of concentrations of these elemennts were given. Based on the combustion simulating ex-periment in the one-dismensional boiler, the contents of REE (rare-earth element) of 18 samples in lignite, fatty coal and their fly and bottom ashes in different combustion condi-tion were determined, and geochemical feature of REE were analyzed.
文摘We analyzed the elemental concentrations and the isotopic compositions of helium and argon in Cambrian to Jurrassic aged Gastropod, Ammonite and Trilobite fossils in order to examine variation in these gases through time. Fossil samples yielded He and Ar isotopic ratios close to the present day atmospheric values, but also indicated some addition of a radiogenic component. We compared the results to theoretical values calculated from a mathematical model of Earth’s atmosphere assuming mantle degassing. Results from our mathmatical models showed that the 40Ar/36Ar ratio of Earth’s atmosphere increased rapidly after the formation of the Earth, but has been almost identical to the present day value for the last 1 Ga. For atmospheric helium, model results were consistent with present day atmospheric values, assuming complete helium degassing from the continental crust into the atmosphere. The model suggests that the atmospheric 3He/4He ratio has remained relatively constant for the last 0.1 Ga. Given the similarity between present day and ancient He and Ar isotopic ratios, we conclude that the corresponding ratios measured in ancient fossil material may partially reflect composition of the ancient atmosphere and are not necessarily due to contamination by the present day atmosphere.
基金The research was under the key science and technologyresearchfunds of the Earthquake Administration of Anhui Province ,China .
文摘Using the latest results of seismic tomography, we studied the deep tectonic settings of the moderate and strong earthquakes in Anhui Province and its neighboring areas (28°~39°N, 112°~124°E). The results are as follows: (1) There exists a certain correlation between the location of moderate-strong earthquake, the geologic structure of the surface and the partitioning of active tectonic elements with the upper-crust velocity structure. Most earthquakes recording M≥6.0 occur in high-velocity zones or in the transitional areas between high-velocity and low-velocity zones in the upper crust. Seismicity in the low-velocity zone has a lesser impact. Earthquakes occuring in the high-velocity zone are distributed mainly in the velocity variation area. The boundary belts and the interior of the North China plain fault block are the main active sites of moderate-strong earthquakes. Beneath the fault basins in the western and northern sides of the block, the upper crust is characterized by a wide discontinuous distribution in the low-velocity zone, and in the transition zone from the low- to high velocities, the moderate strong seismicity shows a zonal distribution where active faults are developed. The NW-extension Zhoukou-Hefei-Xuancheng low-velocity zone separates the high-velocity zones of Dabieshan Mountains and west Shandong-Anhui, and moderate-strong earthquakes on its northern side bordering the high-velocity zones are relatively frequent. This low-velocity zone is probably an important and deeply structured boundary between the North China and the South China tectonic provinces. (2) The frequent moderate-strong earthquake recorded in the past and the recent small earthquake activities in the Huoshan-Lu’an area are the result of a low-velocity zone in the middle crust beneath the central part of Dabieshan and the two sets of deep faults that cut through the crust.(3) In terms of deep structures, the distribution of moderate-strong earthquake in Anhui Province has an obvious regional feature. Based on historical earthquake recurrence intervals and analogue principles of deep seismogenic tectonics, the potential earthquake risk zones recording M_S5.0 in Anhui Province are determined.
文摘Coral samples collected from the waters off the Leizhou Peninsula, the Hainan Island and the Yongxing Island of the Xisha Islands were analyzed by thermal ionization mass spectrometry (TIMS) and multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS) for their U-Th systematics. Their uranium contents are mostly lower than 3μg/g, and the δ+{234}U(T) values are within the range of 150±5. X-ray diffraction analysis showed that the corals are all composed of aragonite. This demonstrates that the corals determined have maintained a close system for 7000 years and their skeletons bear much information about the primitive tropical marine environment. The highly precise age sequence of the corals determined has revealed that there occurred three phases of high sea level in the South China Sea waters, which are dated at 6799-6307 a B.P., 4472-4285 a B.P. and 1279-1012 a B.P., respectively. The three phases lasted 492 a, 187 a and 267 a, respectively. These three phases of high sea level are corresponding to the warm environments that had appeared in China during the Megathermal Period and the Medieval Warm Period in the past ten thousand years.
文摘The Shaxi porphyry copper (gold) deposits are a typical example of porphyry copper deposits associated with diorite in eastern China. Quartz diorite, which hosts the deposits, has a Rb-Sr isochron age of 127.9 ± 1.6 Ma. Geochemically, the rock is rich in alkalis (especially sodium), light rare earth elements (LREE) and large-ion lithophile elements (LILE), and has a relatively low initial strontium isotopic ratio (Isr=0.7058); thus it is the product of differentiation of crust-mantle mixing source magma. The model of alteration and mineralization zoning is similar to the Hollister (1974) diorite model. The ore fluids have a relatively high salinity and contain significant amounts of CO2, Ca2+, Na+ and ***CI?. The homogenization temperatures of fluid inclusions for the main mineralization stage range from 280 to 420°C, the δ18O values of the ore fluids vary from 3.51 to 5.52 %, the δD values are in the range between ?82.4 and ?59.8 %, the δ34S values of sulphides vary from ?0.3 to 2.49 %, and the δ13C values of CO2 in inclusions range between ?2.66 and ?6.53 %. Isotope data indicate that the hydrothermal ore fluids and ore substances of the Shaxi porphyry copper (gold) deposits were mainly derived from magmatic systems.
基金supported by the Ministry of Land and Resources of China (No. [2005]011-16)State Environment Protection Administration of China (No. 2001-1-2)+2 种基金State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciencesthe Guangdong Provincial Office of SciencesTechnology via NSF Team Project and Key Project (Nos. 06202438, 2004A3030800)
文摘Dongguan (东莞) City, located in the Pearl River Delta, South China, is famous for its rapid industrialization in the past 30 years. A total of 90 topsoil samples have been collected from agricultural fields, including vegetable and orchard soils in the city, and eight heavy metals (As, Cu, Cd, Cr, Hg, Ni, Pb, and Zn) and other items (pH values and organic matter) have been analyzed, to evaluate the influence of anthropic activities on the environmental quality of agricultural soils and to identify the spatial distribution of trace elements and possible sources of trace elements. The elements Hg, Pb, and Cd have accumulated remarkably here, incomparison with the soil background content of elements in Guangdong (广东) Province. Pollution is more serious in the western plain and the central region, which are heavily distributed with industries and rivers. Multivariate and geostatistical methods have been applied to differentiate the influences of natural processes and human activities on the pollution of heavy metals in topsoils in the study area. The results of cluster analysis (CA) and factor analysis (FA) show that Ni, Cr, Cu, Zn, and As are grouped in factor F1, Pb in F2, and Cd and Hg in F3, respectively. The spatial pattern of the three factors may be well demonstrated by geostatistical analysis. It is shown that the first factor could be considered as a natural source controlled by parent rocks. The second factor could be referred to as "industrial and traffic pollution sources". The source of the third factor is mainly controlled by long-term anthropic activities, as a consequence of agricultural activities, fossil fuel consumption, and atmospheric deposition.
文摘Leaching is an important way of separation of trace elements from coal. Based on leaching experiments, the content of trace elements separated out from coal is related to their existing state and content in coal, the duration of leaching process, temperature of leaching liquor and its acidity and basicity. The higher the temperature of leaching liquor and the longer the leaching time, the higher the contents of separated trace elements will be. In the course of leaching, the pH values of leaching liquors change and different trace elements are affected differently by the pH values.
基金This research was supported by the National Key Project for Basic Research on the Tibetan Plateau (Grant G1998040800-3);National Natural Science Foundation of China (Grants 49972026 and 39972026);Chinese Academy of Sciences (CAS) Projects (Grant KZ952-JI408) ; US-NSF project (Grant 980612).
文摘A systematic sedimentological and chronological study of typical Paleogene basins in eastcentral Tibet suggests that the depositional characteristics of extensively developed huge-bedded, purplish-red coarse clastic rocks formed in a tectonic setting of regional thrusting and strike-slipping represent a typical dry and hot subaerial alluvial fan environment formed in a proximal and rapidaccumulating sediment body in debris flows and a fan-surface braided river. Combining results from basin-fill sequences, sequences of coarse clastic rocks, fauna and sporo-pollen associations and thermochronological data, it is conduded that the coarse clastic rocks formed in the period of 54.2- 24.1 Ma, nearly coeval with the formation of Paleogene basins in the northern (Nangqen-Yushu thrust belt), middle (Batang-Lijiang fault belt), and disintegration of large basins in the southern (LanpingSimao fold belt) segments of Tibet. The widespread massive-bedded coarse clastic rocks, fold thrusting and strike-slip, thrust shortening, and igneous activities in the Paleogene basins of eastcentral Tibet indicate that an early diachronous tectonic uplift might have occurred in the Tibetan Plateau from Middle Eocene to Oligocene, related to the initial stage of collision of the Indian and Asian plates.
文摘In the process of combustion of coal organic and inorganic materials in it will undergo a complex variation. Part of them will become volatiles and, together with coal smoke, enter into atmosphere, some will remain in micro-particulates such as ash and dust and find their way into atmosphere in the form of solid particles, and the rest will be retained in ash and slag. Coal ashes are the residues of organic and inorganic substances in coal left after coal combustion and the composition of coal ashes is dependent on that of minerals and organic matter in coal. This paper deals with the chemical composition of coal ashes, the distribution of trace elements in them and their petrological characteristics, and also studies the relationship between the yield of coal ashes and the distribution of trace elements. In addition, a preliminary study is also undertaken on the factors that affect the chemical composition of coal ashes. As viewed from the analyses of coal ash samples collected from the Yanzhou mining district, it can be seen clearly that coal ashes from the region studied are composed chiefly of crystalline materials, glassy materials and uncombusted organic matter and the major chemical compositions are SiO 2, Al 2O 3, Fe 2O 3, and CaO, as well as minor amounts of SO 3, P 2O 5, Na 2O, K 2O and TiO 2. During the combustion of coal, its trace elements will be redistributed and most of them are enriched in coal ashes. At the same time, the concentrations of the trace elements in flying ash are much higher than those of bottom ash, i.e., with decreasing particle-size of coal ashes their concentrations will become higher and higher. So the contents of trace elements are negatively proportional to the particle-size of coal ashes. There has been found a positive correlation between the trace elements Th, V, Zn, Cu and Pb and the yield of coal ashes while a negative correlation between Cl and the yield of coal ashes.
基金This paper is supported by the Open Fund of the State Key Laboratoryof Geological Processes and Mineral Resources of China , and by aNSERC Discovery Research Grant .
文摘The weight of evidence (WofE) model has been widely used for mineral potential mapping. During the conversion of a multiclass map into a binary map a lot of mineralization information is artificially added or lost because the generalization of the class within the cumulative distance interval to a linear feature is based on a maximum contrast, which matches a cumulative distance interval. Additionally, some categorical data evidence cannot be generated by this method because a maximum contrast does not exist. In this article, an alternative (W^+ -W^- )-based WofE model is proposed. In this model, the "(W^+ -W^- ) greater than zero or not" is used as a criterion to reclassify the corresponding categorical class into a presence or absence class to convert a multielass map into a binary map. This model can be applied to both categorical data and successive data. The latter can be operated as categorical data. The Wt and W^- of the generated binary maps can be recalculated, and several binary maps can be integrated on the condition that the reclassified binary evidences are conditionally independent of each other. This method effectively reduces artificial data and both nominal and categorical data can be operated. A ease study of gold potential mapping in the Abitibi area, Ontario, Canada, shows that the gold potential map by the (W^+ -W^- ) model displays a smaller potential area but a higher posterior probability (POP), whereas the potential map by the traditional (W^+ - W^- ) model exhibits a larger potential area but a lower POP.
基金Under the auspices of the National Natural Science Foundation of China (No.40571162), the Natural Science Foun-dation of Anhui Province (No.050450401), Natural Science Foundation of Anhui Provincal Education Department (No.2004kj65zd), Postdoctoral Foundation of University of Science and Technology of China
文摘In China, most directions of river flowing are from west to east. During historic period, since the water traffic played an important role, it was very important to form a cross-horizontal net of water carriage route. Canals should be dug so as to make up the lack of north-south river. Tongji Grand Canal, dug in the first year of Daye (605 A.D.) in the Sui Dynasty, was the important component of north-south system of Grand Canals in China. It promoted economic and social development of the Sui, Tang and Song dynasties (605 A.D.-1279 A.D.). As Tongji Canal (i.e. Tongji Grand Canal) flowed across the Huaibei Plain, which is aggraded by abundant mud and sand deposit resulted from the Huanghe (Yellow) River flooding, many traces (such as old channel) and human culture heritages were buried under mud-sand. Tongji Canal was silted up, and disappeared in the Jin Dynasty (1115 A.D.-1234 A.D.). From then on, there were many different stories about the flowing route of the canal in historical literature. Based on space-bone and air-bone remote sensing imagery, we attempt to search the old channel of Tongji Canal, and supplement historical record. The paper discusses transformation process of Tongji Canal’s traffic function, and resumptively summarizes the reasons of the transformation, which results from synthetic function of physical geographical, political, economic, and social conditions.
基金funded by grants from the Ministry of Science and Technology of China (2014DFR21270)from the China Geological Survey (DD20160023-01 and DD20160022-01)+1 种基金from the National Natural Science Foundation of China (41802034)from the National Science Foundation of China (41720104009, 41672063, 41773029).
文摘The Cuobuzha high-Cr chromitites in the western segment of Yarlung Zangbo Suture Zone of Tibet are mainly hosted in the harzburgites as massive type, which are characterized by high concentrations of platinum group elements(PGE) ranging from 380 to 577 ppb, and low Pd/Ir ratios(<0.1). In mid-ocean ridge basalts(MORB)-normalized spidergrams, chromites of the Cuobuzha chromitites are depleted in Al, Ga, V, Mg and Zn, and enriched in Mn and Cr, sharing similar patterns with those of ophiolitic boninites in the Bonin and Thetford Mines. Approximately 20 platinum group mineral(PGM) grains were discovered from the samples, including laurite, erlichmanite, Os-Fe alloy, cuproiridsite, and irarsite. The PGM assemblages indicate that sulfur fugacity was initially low enough to allow the precipitation of Os-Fe alloy and increased thereafter, with the fall in temperature. Primary Fe-Ni and Fe-Cr alloys, which are stable in a highly reduced environment, occur as inclusions within chromites or clinopyroxenes. Calculated results show that the parental magma has an intimate affinity with boninites. Based on our observations, a model is proposed wherein the Cuobuzha chromitites contain high-pressure and low-pressure chromites. Low-pressure chromites were formed via reaction between boninitic melts and peridotites, during which the high-pressure chromites hosting highly reduced minerals were mobilized by melts and were reallocated to podiform chromitites.
基金funded by the National Basic Research Program of China (973 Program,No.2010CB428902)
文摘The biogenic silica (BSi) ,total organic carbon (TOC) ,total nitrogen (TN) and grain size were analyzed with a gravity core (3250-6) collected from the mud area in the north East China Sea.The average deposition rate of the upper core was about 0.078cm yr1based on the results of 210Pbex.The mean grain size increased with depth in general.The frequency distribution of grain size showed that two marked changes of deposition environment occurred at 30 cm and 50 cm depths (about 1550 AD and 1300 AD,respectively) .The variations of BSi and TOC indicated two distinct major periods of primary productivity over the past 800 years:a stage of low primary productivity corresponding to weak upwelling and low nutrient input below 30 cm depth (about 1200-1550 AD) ,and a stage of high primary productivity with strong currents and upwelling above 30 cm depth (about 1550-1950 AD) .The stage with high primary productive appeared to be due to the northward-expanded muddy area caused by strong Asian Winter Monsoon and enhanced Yellow Sea Warm Current in winter.In conclusion,the BSi and TOC in the muddy sediments,the symbols of marine primary productivity,can be then used to investigate the evolution history of currents and relative climate change in the offshore areas.
基金supported by the National Natural Science Foundation of China (No. 40638041)National Key Technology R&D Program (No. 2006BAB01A01)+2 种基金Project of China Geological Survey (No. 1212010633910)the National High Technology Research and Development Program of China (Nos. 2006AA06Z115, 2006AA06Z113)State Key Laboratory of Geological Processes and Mineral Resources (No. GPMR2007-12)
文摘Weights of evidence (WofE) is an artificial intelligent method for integration of information from diverse sources for predictive purpose in supporting decision making. This method has been commonly used to predict point events by integrating point training layer and binary or ternary evidential layers (multiclass evidence less commonly used). Omnibus weights of evidence integrates fuzzy training layer and diverse evidential layers. This method provides new features in comparison with the ordinary Wore method. This new method has been implemented in a geographic information system-geophysical data analysis system and the method includes the following contents: (1) dual fuzzy weights of evidence (DFWofE), in which training layer and evidential layers can be treated as fuzzy sets. DFWofE can be used to predict not only point events but also area or line events. In this model a fuzzy training layer can be defined based on point, line, and areas using fuzzy membership function; and (2) degree-of-exploration model for WorE is implemented through building a degree of exploration map. This method can be used to assess possible spatial correlations between the degree of exploration and potential evidential layers. Importantly, it would also make it possible to estimate undiscovered resources, if the degree of exploration map is combined with other models that predict where such resources are most likely to occur. These methods and relevant systems were vafidated using a case study of mineral potential prediction in Gejiu (个旧) mineral district, Yunnan ( 云南), China.