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1.
First order geodetic measurements show that strain rates in southeastern New South Wales are about 50 × 10‐8 y‐1. These strain rates are much greater than those suggested by seismicity. The direction of the principal axis of compression varies with position, but it is consistent with compression axis directions of the earthquake focal mechanisms in the Bowning area, and with the pattern of late Cainozoic vertical displacements suggested by geomorphology. In southwestern Western Australia strain identified from geodetic measurements is patchy in distribution, and is irregular in magnitude and direction. It is found close to areas of historic faulting, in areas of high measured stress, and across the Darling Fault line of weakness separating the Perth Basin from the Yilgarn Craton.  相似文献   

2.
The Production and Release of CFCs from Coal Combustion   总被引：3，自引：0，他引：3  
The destruction of the ozone layer in the atmosphere caused by industrially synthesized CFCs has aroused greatest concerns from the international society, but the CFCs formed from burning of coal containing fluorine have not been recognized by the world yet. In the present study, we condensed the gas through cold traps and used the GC-MS to measure the gas composition, and found that the content of CFC-12 in the smog from coal combustion was significantly higher than the background value of the local atmosphere. This proves that CFC-12 is formed in the process of coal combustion. This paper discusses a new source of non-synthesized CFCs.  相似文献   

3.
In order to understand the distribution characteristics of biomarkers in source rocks,which may be related to organic input,Quaternary sediments from the Caohai Basin and the Chaiwobu Lake were analyzed for sterols,As a result,various sterols,have been found in the sediments.The composition of sterols in the sediments revealed that cholesterols and cholestadienols are more abundant than their C29 counterparts in the Chaiwobu Lake sediments and that C29 sterols are more abundant in the peats from the Caohai Basin,It is also found that stanol/sterol ratios in clays are higher than in peats.Studies show that organic input to the Chaiwobu Lake is mainly plankton and zooplankton and to the Caohai Basin is mainly terrestrial high plant.The authors have proposed that the relative abundance of C27 or C29 sterane in source rocks may reflect input characteristics to some extent and the stanol/sterol ratios may reflect the redox conditions of the depositional environments.  相似文献   

4.
During the last century, several lead mines and a metal smelter were in production in the Upper Ribeira Valley, southeastern Brazil. After fifty years of activity, the refinery was shut down in November 1995 and, thereafter the last mines in production were closed. Since 1998, a multidisciplinary research group has carried out an ambitious investigation among the population of five municipalities in the Ribeira Valley （sampled population of 472 children and 523 adults） to assess the human exposure to lead. The highest blood lead levels were found among the population of two villages in the vicinity of the smelter where soil and indoor-dust are highly contaminated. During the present study, the lead contents of several food species that are part of local population diet were investigated. Greens, vegetables, corn, chicken eggs and cow milk, were sampled in two occasions, July 2004 and February 2005. The analytical procedures included burning of organic matter, pre-concentration of lead and, finally, determination by AAS using background correction. The quantification limit was 0.05 μg/g Pb. Soil samples were also collected and analyzed by X-ray fluorescence spectroscopy with a quantification limit of 2 μg/g Pb. The results are very impressing since 100% of greens, vegetables and eggs yielded lead concentrations exceeding the upper limits established by Brazilian regulations whereas milk and maize samples presented lead contents below the regulated limit of 0.05 μg/g Pb. Lead concentrations in soil varied between 156 and 1292 μg/g Pb, resembling the results of previous studies and far exceeding the threshold of 200 μg/g Pb indicated as the intervention value. Lead contents in some species vary consistently with lead concentrations in soils, however, other factors may account for the bioavailability of lead and its intake by plants, like the soil pH, its cationic exchange capacity, clay and organic matter contents, characteristics of the plant species itself, climate, among others.  相似文献   

5.
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6.
Mantle-derived xenoliths and xenocrysts in Pale-ozoic diamondiferous ki mberlites in Mengyin (Shan-dong Province) and Fuxian (Liaoning Province) showthe presence of a cold,thick lithospheric mantle be-neath the North China craton ( NCC) in the MiddleOrdovician ( Griffin et al ., 1998 ; Menzies et al .,1993 ;Fan and Menzies ,1992) . However ,studies onmantle peridotites captured in the Tertiary to Neo-gene basalts of the NCC have revealed the existenceof a thin, hot and fertile lithosph…  相似文献   

7.
Failure of borehole sources in weathered and fractured crystalline basement aquifers in Malawi in southern Africa has been linked with poor borehole design, mechanical failure and badly sited boreholes. However, recent work in Malawi indicates that demand may now exceed long-term resource potential in some places and that this is also a cause of water point failure. An 11-year climate cycle (including a wet and dry period) necessitates overdraft from groundwater storage during the dry-cycle years before episodic rainfall events in the wetter part of the cycle again recharge the aquifers. Data, particularly groundwater hydrograph data, are sparse, but sufficient to evaluate the long-term renewable groundwater potential for both fractured and weathered basement-aquifer types in each of the 15 management areas in Malawi. The groundwater potential or long-term renewable resource (recharge) is given by the sum of Darcian throughflow and dry-season depletion of storage. Estimated rural demand exceeds the renewable resource in the fractured-rock aquifer in two management units and in the weathered-rock aquifer in two other units. Although there is inherent uncertainty in the water-balance estimates, the likelihood that rural demand is exceeding long-term average recharge in some areas is cause for concern.  相似文献   

8.
Taipingxi, Yichang, Hubei province, China, is situated on the left of the Three-Gorges Dam of the Yangtze River. The bedrock is granite. Yhe Three-Gorges Project began to sluice in June, 2004. The contents of magnesium, aluminum and fluoride in rock and s…  相似文献   

9.
The Eclogite Zone, of the Tauern Window is an exhumed subduction channel comprising eclogites with different grades of retrogression in a matrix of high-pressure metasediments. The rocks were exposed to 600 °C and 20–25 kbars, and then retrogressed during their exhumation, first under blueschist facies and later under amphibolite facies metamorphism. To gain insights into the deformation within the subduction channel during subduction and exhumation, both fresh and retrogressed eclogites, as well as the surrounding metasediments were investigated with respect to their deformation microstructures and crystallographic preferred orientations (CPOs). Pristine and retrogressed eclogites show grain boundary migration and subgrain rotation recrystallization microstructures in omphacite. A misorientation axes analysis reveals the activity of complementary deformation mechanisms including grain boundary sliding and dislocation creep. The omphacite CPOs of the eclogites correspond to dominant SL-fabrics characteristic of plane strain deformation, though there are local variations towards flattening or constriction within the paleosubduction channel. The glaucophane CPOs in retrogressed eclogites match those of omphacite, suggesting that a constant strain geometry persisted during exhumation at blueschist facies conditions. Plastic deformation of the host high-pressure metasediments outlasted that of the eclogites, as indicated by white mica fabrics and quartz CPO. The latter is consistently asymmetric, pointing to the operation of non-coaxial deformation. The microstructures and CPO data indicate a continuous plastic deformation cycle with eclogite and blueschist facies metamorphism related to subduction and exhumation of the different rock units.  相似文献   

10.
In this paper both processes of landslide and subsidence are consid-ered to be limited systems.Each of these systems in nature might be re-garded as an organism.Generally their lifespan must develop with com-mon ecological characteristics,including several evolutional stages,such asinitiation,growth,maturation,decline and death.Among these stages,maturation is emphasized so as to find the occurring or thriving date ofboth systems.An once-through cycle of both landslide and subsidence isestablished and is accurately predicted by a developed,mathematic model of thePoisson cycle.The Weibull distribution is cited for a landslide example.Both fundamentals are discussed.Stage predictions of landslide and subsid-ence are performed for several examples.Back analysis of landslides thathave already happened are studied with the same model.And when com-pared with results from the biological mathematic model and with practicalresults,it is found that they correspond.Stage prediction of subsidences isalso researched  相似文献   

11.
Mudrocks from three lower Paleozoic basins in the British Caledonides (southern Lake District, northern Lake District and Southern Uplands) were investigated to determine the influence of sub-greenschist facies metamorphism on Li and the factors that control Li in fine-grained terrigenous sedimentary rocks. Metamorphic grade, as determined by KI (Kübler index) does not correlate with Li content ([Li]) and δ7Li, indicating that sub-greenschist facies metamorphism has negligible effect on Li in these rocks. Collectively, the data for all three basins show a negative correlation between [Li] and δ7Li and a positive correlation between [Li] and the Chemical Index of Alteration (CIA), suggesting that provenance exerts the greatest control on Li in mudrocks. Samples from the northern Lake District, which were deposited in an extensional basin, have homogeneous REE patterns, similar to shale composites (PAAS), the highest CIA, Th/U and [Li] and the lowest δ7Li and εNd, consistent with their derivation from a highly weathered, ancient continental source. By contrast, mudrocks from the Southern Uplands range to the lowest CIA, Th/U and [Li] and have the highest δ7Li and εNd. These samples were deposited in a forearc basin on the southern margin of the Laurentian craton and contain volcanic detritus. Their REE patterns are the most variable, ranging from average shale-like patterns to less LREE-enriched patterns. The compositional heterogeneity within the Southern Uplands mudrocks is consistent with a mixed provenance that includes juvenile crustal materials (lower [Li], εNd and Th/U, higher δ7Li), likely derived from the arc, as well as more highly weathered continental detritus. Mudrocks from the southern Lake District were deposited in a foreland basin, and exhibit geochemical characteristics intermediate between the northern Lake District and the Southern Uplands mudrocks, indicating their derivation from a mixed source. Our study shows that Li concentrations and δ7Li can provide additional information on the degree of weathering of the provenance of mudrocks.  相似文献   

12.
Studies of the mantle-derived iherzolites from Nushan show that in addition to CO2,there were present H2O and small amounts of CO, CH4, SO2,Cl and F in the initial mantlc fluids derived fron the asthenospheric mantlc plumc .The imitial fluids accumulated in some regions of the mantle, resulting in lowering of the mantle solidus (and liquidus) and partial melting of the upper mantle. Melts formed from low-degree of fluid-involved partial melting of the upper mantle would be highly enriched in incompatible elements.Fluies and melts are allthe metasomatic agents for mantle metasomatism, and the interaction between them and the depleted mantle could result in the substan-tial local enrichment of LREE and incompatible elements in the latter.In case that the concentration of H2O in the fluids (and melts) is lower ,only cryptic metasomatism would occur, in case that the concentration of H2O is higher,the degree of partial melting would be higher and hydrous metasomatic phases(e.g. amphiboles )would nucleate. Under such circumstances, there would occur model metasomatism.  相似文献   

13.
This paper provides first report of silica-rich anthropogenic spherules of varying colour, shape, size, surface texture and chemical composition found in road-deposited sediments (RDS) of Allahabad city, Uttar Pradesh, India. Morphological details and lithophile elemental composition of the silica-rich spherules are compared to microtektites and impact spherules from India to demonstrate their striking morphological similarities and chemical variability. This study suggests the need to use spherule data carefully while assigning an impact origin to spherule-finds or spherule-bearing lithological horizons.  相似文献   

14.
The chemical leaching method is used for a systematic analysis of distribution characteristics of acid-soluble and acid-insoluble REE and other trace elements from the Luochuan loess deposits. The study shows that the acid-insoluble phase in loess and palaeosol is a stable component of old aeolian dusts and is characteristic of the provenance; the acid-soluble phase is the unstable component in the weathering pedogenic process and reflects rock-forming features after accumulation of aeolian dusts. The acid-insoluble REE and acid-soluble Sr and Pb can be used as geochemical indicators respectively to trace the provenance characteristics and the weathering pedogenic process.  相似文献   

15.
We have examined microstructures, mineralogical composition, geochemical alteration, and texture of four selected fault rock samples from the Deep Geodynamical Laboratory (DGLab) Gulf of Corinth project using optical microscopy, cathodoluminescence microscopy (CL), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and synchrotron X-ray diffraction measurements. The fault core is composed of red and gray clayey gouge material and surrounded by a damage zone of brecciated limestones. Pressure solution features, calcite veins and calcite clasts in the breccia and gouge material attest the presence of paleo-fluids and fluid-driven mass transfer during deformation. Differences in CL-colors between the matrix and calcite vein cement and inside the vein cement suggest repeated infiltration of fluids with different composition from various sources (formation water and meteoric water). Twin lamellae densities estimated in calcite veins are used as paleo-piezometer. The deduced differential stress is ∼140 ± 70 MPa for the older vein generation and appears to be higher than stress for the youngest veins (45 ± 23 MPa). In spite of the relatively small clay content in both samples, newly formed clay minerals have been observed in gray as well as red clayey gouge material. Differences between gray and red clay gouge material are found in fault rock composition, porosity and clay fabric. The proportion of chlorite in the red gouge is significantly less than that in the gray gouge whereas the initial porosity is significantly higher than in the gray gouge material. The detection of a well-oriented clay fabric in red clay gouge samples is unique in comparison to other major fault zones.  相似文献   

16.
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17.
Titanium contents of quartz have been analyzed in samples of granulites from various metamorphic complexes of eastern Siberia (Sutam, Chogar, and Sharyzhalgai) that contain mineral assemblages conventionally regarded as indicative of “ultrahigh-temperature” metamorphism. The related TitaniQ temperature estimates (Wark and Watson, 2006) are consistent with those of other mineralogical geothermometers and are commonly much lower than “ultrahigh-temperature”.  相似文献   

18.
Four experiments have been done on the influence of times of infusion, temperature, time and ratio of tea to water on the dissolving characteristics of fluoride and aluminum in brick tea. According to the results, the behaviors of F and Al which found their way into tea liquor were analyzed and the conclusions have been drawn： the dissolution of F and Al is not synchronous and after the elements find their way into tea liquor respectively, they will be reset to form complexes of F and Al.  相似文献   

19.
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20.
Nine pieces of gabbroic xenoliths from Hannuoba were examined for their major and trace elements and Nd,Sr and Pb isotopes.The results show that the gab-broic xenoliths are of more mafic basaltic composition .Their abundances show narrow variations in major elements.The trace element contents are highly variable in contrast with those of host basalts and lherzolite xenoliths.The gabbroic xenoliths are rich in Nd(0.51159-0.51249),Sr(0.70491-0.70768) and low in radiogenic Pb(16.283-17.046, 15.191-15.381 and 36.999-37.476),significantly different from basalts and lherzolites in isotopic space.The calculated Nd and Pb model ages are about 3.0-3.5 Ga.The rocks have relatively low equilibrium T(-850℃) and P(0.8-0.9 Gpa).They could be inter-preted to be the product of upper mantle melting at the boundary between the lower crust and the upper mantle.Their chemical and isotopic variations can be ascribed to different degrees of melting,segregation and long-term evolution.  相似文献   

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