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1.
The Enshi area, Hubei Province in China, is a typical seleniferous environment, where seleniferous carbonaceous shale and carbonaceous siliceous rocks of Permian widely occur. In the 1960＇s, the first selenosis case in the human population in the world had even brought out at Yutangba Village, Shuanghe community, which resulted in move-off all local residenters The Enshi area possesses the advantageous natural conditions to develop Se-hyperaccnmulator. The selenosis case of human population may be related to having eaten the wild vegetable hyperaccumulating selenium. Mao Dajun （1997） found that the most seleniferous plant was cabbage in the Enshi area which contains Se 224.30 mg/kg. In order to find out Se-hyperaccnmulator in China as soon as possible, the present research made a lot of work on many numbers of wild plants which grow in Enshi, Hubei Province, China. Finally, we found Thlaspi arvenst L., the first Se-hyperaccumulator of China at Yutangba Village. In this plant, Thlaspi arvenst L., the contents of selenium （DW） are 802-870 mg/kg （the average 843 mg/kg） for the whole plant, 1121 mg/kg for root, 511 mg/kg for stem and 1427 mg/kg for leaf, respectively. The newly found Thlaspi arvenst L. by us is the most seleniferous plant which has been found in China up to now, whose Se in its leaf is higher than the international criterion of 1000 mg/kg for Se-hyperaccnmulator.  相似文献   

2.
Kuh-e Mond Field is a conventional heavy oil resource in the Zagros foreland Basin, Iran, produced from the fractured carbonates partially filled by dolomite, calcite, and anhydrite cement. Vitrinite reflectance data from carbonate reservoir suggest low-maturation levels corresponding to paleotemperatures as low as 50 °C. The observed maturation level (< 0.5% Rmax) does not exceed values for simple burial maturation based on the estimated burial history. Oil inclusions within fracture-filled calcite and dolomite cement indicate the key role of these fractures in oil migration.The fluid inclusion temperature profiles constructed from the available data revealed the occurrence of petroleum in dolomite, calcite, and anhydrite and characterize the distinct variations in the homogenization temperatures (Th). Fluid inclusions in syntectonic calcite veins homogenize between 22 °C and 90 °C, showing a salinity decrease from 22 to 18 eq. wt.% NaCl. Fluid inclusions in anhydrite homogenize at < 50 °C, showing that the pore fluids became warmer and more saline during burial. The Th range in the calcite-dolomite cement depicts a change in water composition; therefore, we infer these cements precipitated from petroleum-derived fluids. The microthermometry data on the petroleum fluid inclusions suggest that the reservoir was filled with heavy black oils and high-salinity waters and indicate that undersaturated oil was present in a hydrostatically pressured reservoir.The Th data do not support vertical migration of hot fluids througout the section, but extensive lateral fluid migration, most likely, drove tectonically dewatering in the south or west of the pool.  相似文献   

3.
ZU Bo  XUE Chunji  ZHAO Yi 《地质学报》2014,88(Z2):957-958
Please refer to the attachment(s) for more details.  相似文献   

4.
A synthesis of the petrological characters of granulite facies rocks that contain equilibrium sapphirine ＋ quartz assemblage from two localities （Tonagh Island （TI） and Priestley Peak （PP）） in the Napier Complex,East Antarctica,provides unequivocal evidence for extreme crustal metamorphism possibly associated with the collisional orogeny during Neoarchean.The reaction microstructures associated with sapphirine ＋ quartz vary among the samples,probably suggesting different tectonic conditions during the metamorphic evolution.Sapphirine and quartz in TI sample were probably in equilibrium at the peak stage,but now separated by corona of Grt ＋ Sil ＋ Opx suggesting near isobaric cooling after the peak metamorphism,whereas the Spr ＋ Qtz ＋ Sil ＋ Crd ＋ Spl assemblage replaces garnet in PP sample suggesting post-peak decompression.The application of mineral equilibrium modeling in NCKFMASHTO system demonstrated that Spr ＋ Qtz stability is lowered down to 930 ℃ due to small Fe3＋ contents in the rocks （mole Fe2O3/（FeO ＋ Fe2O3） =0.02）.The TI sample yields a peak p-T range of 950-1100 ℃ and 7.5-11 kbar,followed by cooling toward a retrograde stage of 800-950 ℃ and 8-10 kbar,possibly along a counterclockwise p-T path.In contrast,the peak condition of the PP sample shows 1000-1050 ℃ and ＞12 kbar,which was followed by the formation ofSpr ＋ Qtz corona around garnet at 930-970 ℃ and 6.7-7.7 kbar,suggesting decompression possibly along a clockwise p-T trajectory.Such contrasting p-T paths are consistent with a recent model on the structural framework of the Napier Complex that correlates the two areas to different crustal blocks.The different p-T paths obtained from the two localities might reflect the difference in the tectonic framework of these rocks within a complex Neoarchean subduction/collision belt.  相似文献   

5.
Please?refer?to?the?attachment(s)?for?more?details.  相似文献   

6.
A typical HP/MT (high pressure/medium temperature) eclogite from Xiongdian, northwestern Dabie Mountains, has been geochronologically studied using the single-zircon U-Pb, 40Ar-39Ar and Sm-Nd methods. Prismatic zircons occurring as inclusions within garnets define a minimum crystallization age of 399.5±1.6 Ma. 40Ar-39Ar dating on amphibole gives a plateau age.of 399.2 ± 4 Ma, which is interpreted as a retrogression age of amphibolite facies. This integrated study enables us to conclude that the age of high-pressure metamorphism is older than 399.5 ± 1.6 Ma, suggesting Caledonian collision between the North China and Yangtze plates. Round zircon within the aggregate of quartz and muscovite gives a concordant age of 301± 2 Ma, reflecting a later retrogression event. An age profile of post-eclogite metamorphism is documented, including amphibolite facies metamorphism at 399.2 Ma shortly after eclogitization and later retrogressive metamorphism at 301 Ma. Sm-Nd mineral isochron of garnet+omphacite gives  相似文献   

7.
Kersty Hobson 《Geoforum》2011,42(4):405-407
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8.
Widely developed in the Dabie complex are various disequilibrium textures which provide direct evidence for the evolution of metamorphism and late-stage uplifting history.The typical mineral assemblasge in the Opx-Gt-Pl-Bi gneiss in Huangtuling,Luotian County,Hubei Province,Is Opx(I) Gt Pl(I) Bi(I) Q.The corona composed of cordierite and orthopyroxene(Ⅱ）growing around garnets in the granulite makes it clear that there occurres the following metamorphic reaction:Gt Q→Cd Opx(Ⅱ）.It is estimated that the gran ulite-forming temperature(T)and pressure(P)are 857-998℃ and 1.18-1.23Gpa,respectively,and the corona was formed under the following conditions:T=829-911℃ and P=0.52-0.59GPa.The above results indicate that There occurred a rapid and nearly adiabatic uplifting event and a decompressional metamorphism in the Dabie complex after the formation of granulite.As compared with the granulites worldwidely distributed in 90 locations(Harley 1989),the Huangtuling granulite should belong to the high-pressure type,which represents the composition of the crust at a depth of more than 40 kilometers.  相似文献   

9.
The results of geochronological, mineralogical, petrographical, and geochemical study of the Ilbokich ultramafic lamprophyre are reported. The specific features in the mineral and chemical compositions of the studied ultramafic lamprophyre indicate that it can be regarded as a variety similar to aillikite, while other differences dominated by K-feldspar can be referred to damtjernite. According to Rb–Sr analysis, ultramafic lamprophyre dikes intruded at the turn of the Early and Middle Devonian, about 392 Ma ago. This directly proves the existence of Early Paleozoic alkali–ultramafic magmatism in the northern part of the southwest Siberian Platform. A finding of Devonian alkali–ultramafic lamprophyre is of dual predictive importance. On the one hand, it is indicative of the low probability of finding large diamond-bearing deposits in close association with aillikite. On the other hand, it can be indicative of a possible large Devonian diamond province in the studied territory, where diamondiferous kimberlite is structurally separated from aillikite.  相似文献   

10.
Previous prospectivity modelling for epithermal Au–Ag deposits in the Deseado Massif, southern Argentina, provided regional-scale prospectivity maps that were of limited help in guiding exploration activities within districts or smaller areas, because of their low level of detail. Because several districts in the Deseado Massif still need to be explored, prospectivity maps produced with higher detail would be more helpful for exploration in this region.We mapped prospectivity for low- and intermediate-sulfidation epithermal deposits (LISEDs) in the Deseado Massif at both regional and district scales, producing two different prospectivity models, one at regional scale and the other at district-scale. The models were obtained from two datasets of geological evidence layers by the weights-of-evidence (WofE) method. We used more deposits than in previous studies, and we applied the leave-one-out cross validation (LOOCV) method, which allowed using all deposits for training and validating the models. To ensure statistical robustness, the regional and district-scale models were selected amongst six combinations of geological evidence layers based on results from conditional independence tests.The regional-scale model (1000 m spatial resolution), was generated with readily available data, including a lithological layer with limited detail and accuracy, a clay alteration layer derived from a Landsat 5/7 band ratio, and a map of proximity to regional-scale structures. The district-scale model (100 m spatial resolution) was generated from evidence layers that were more detailed, accurate and diverse than the regional-scale layers. They were also more cumbersome to process and combine to cover large areas. The evidence layers included clay alteration and silica abundance derived from ASTER data, and a map of lineament densities. The use of these evidence layers was restricted to areas of favourable lithologies, which were derived from a geological map of higher detail and accuracy than the one used for the regional-scale prospectivity mapping.The two prospectivity models were compared and their suitability for prediction of the prospectivity in the district-scale area was determined. During the modelling process, the spatial association of the different types of evidence and the mineral deposits were calculated. Based on these results the relative importance of the different evidence layers could be determined. It could be inferred which type of geological evidence could potentially improve the modelling results by additional investigation and better representation.We conclude that prospectivity mapping for LISEDs at regional and district-scales were successfully carried out by using WofE and LOOCV methods. Our regional-scale prospectivity model was better than previous prospectivity models of the Deseado Massif. Our district-scale prospectivity model showed to be more effective, reliable and useful than the regional-scale model for mapping at district level. This resulted from the use of higher resolution evidential layers, higher detail and accuracy of the geological maps, and the application of ASTER data instead of Landsat ETM + data. District-scale prospectivity mapping could be further improved by: a) a more accurate determination of the age of mineralization relative to that of lithological units in the districts; b) more accurate and detailed mapping of the favourable units than what is currently available; c) a better understanding of the relationships between LISEDs and the geological evidence used in this research, in particular the relationship with hydrothermal clay alteration, and the method of detection of the clay minerals; and d) inclusion of other data layers, such as geochemistry and geophysics, that have not been used in this study.  相似文献   

11.
The eastern Himalayan syntaxis in Namjagbarwa is a high-grade metamorphic terrain formed by the India-Eurasia collision and northward indentation of the Indian continent into Asia. Right- and left-lateral slip zones were formed by the indentation on the eastern and western boundaries of the syntaxis respectively. The Dongjug-Mainling fault zone is the main shear zone on the western boundary. This fault zone is a left-lateral slip belt with a large component of thrusting. The kinematics of the fault is consistent with the shortening within the syntaxis, and the slipping history along it represents the indenting process of the syntaxis. The Ar-Ar chronological study shows that the age of the early deformation in the Dongjug-Mainling fault zone ranges from 62 to 59 Ma. This evidences that the India-Eurasia collision occurred in the early Paleocene in the eastern Himalayan syntaxis.  相似文献   

12.
The principle prerequisite for the formation of a volcano is the generation of a channel for magma transportation. There is little research on the deep mechanical mechanism for the formation of a magma transportation channel in the Tibetan plateau. Based on the subcrustal mantle convectiongenerated stress field inversed by gravity anomalies, together with its relationship to the Cenozoic volcanism in the plateau, and the mechanism of crustal fracture formation, as well as the numerical results of the evolution of mantle convection beneath the plateau, this paper investigates the deep mechanical mechanism for the formation of a magma transportation channel in the Tibetan plateau. There are two significant extensional convection-generated stress zones beneath the plateau, in which the volcanic rocks in the central and northern parts of the plateau are distributed. The Linzizong volcanism in southern Tibet correlates the upwelling mantle flow prior to the India-Asia collision or during the early stage of the collision. The magnitude of the stress is - 100 MPa, which is the same order of force that causes crustal fractures. The evidence implies that the mantle convection-generated stress is one of the principle causes of crustal fractures, and furthermore, the formation of the magma transportation channel in the Tibetan plateau.  相似文献   

13.
The Tongling area is one of the 7 ore-cluster areas in the Middle-Lower Yangtze metallogenic belt,East China,and has tectonically undergone a long-term geologic history from the late Paleozoic continental rifting,through the Middle Triassic continent-continent collision to the Jurassic-Cretaceous intracontinental tectono-magmatic activation.The Carboniferous sedimentary-exhalative processes in the area produced widespread massive sulfides with ages of 303-321 Ma,which partly formed massive pyrite-Cu deposits,but mostly provided significant sulfur and metals to the skarn Cu mineralization associated with the Yanshanian felsic intrusions. To understand the Carboniferous submarine hydrothermal system,an area of about 1046 km~2 was chosen to carry out the geological fluid mapping.Associated with massive sulfide formation,footwall sequences 948 m to 1146m thick,composed of the Lower Silurian-Upper Devonian sandstone,siltstone and thin-layered shale,were widely altered.This hydrothermal alteration is interpreted to reflect large- scale hydrothermal fluid flow associated with the late Paleozoic crustal rifting and subsidence.Three hydrothermal alteration types,i.e.,deep-level semiconformable silicification(S_1),fracture-controlled quartz-sericite-pyrite alteration(S_(2-3)),and upper-level sub-discordant quartz-sericite-chlorite alteration(D_3),were developed to form distinct zones in the mapped area.About 50-m thick semiconformable silicification zones are located at～1-km depth below massive sulfides and developed between an impermeable shale caprock(S_1)and the underlying Ordovician unaltered limestone. Comparisons with modern geothermal systems suggest that the alteration zones record a sub-seafloor aquifer with the most productive hydrothermal fluid flow.Fracture-controlled quartz-sericite-pyrite alteration formed transgressive zones,which downward crosscut the semiconformable alteration zones, and upwards grade into sub-discordant alteration zones that enveloped no economic stringer- stockwork zones beneath massive sulfides.This transgressive zone likely marks an upflow path of high- flux fluids from the hydrothermal aquifer.Lateral zonation of the sub-discordant alteration zones and their relationship to overlying massive sulfide lenses suggest lateral flows and diffusive discharging of the hydrothermal fluids in a permeable sandstone sequence.Three large-sized,14 middle-small massive sulfide deposits,and 40 massive sulfide sites have been mapped in detail.They show regional strata- bound characters and two major styles,i.e.,the layered sheet plus strata-bound stringer-style and the mound-style.Associated exhalite and chemical sedimentary rock suites include(1)anhydrite-barite,(2) jasper-chert,(3)Mg-rich mudstone-pyrite shale,(4)barite lens,(5)siderite-Fe-bearing dolomite,and (6)Mn-rich shale-mudstone,which usually comprise three sulfide-exhalite cyclic units in the area. The spatial distribution of these alteration zones(minerals)and associated massive sulfides and exhalites,and regional variation inδ~(34)S of hydrothermal pyrite and inδ~(18)O-δ~(34)C of hanging wall carbonates,suggest three WNW-extending domains of fluid flow,controlled by the basement faults and syn-depositional faults.Each fluid domain appears to have at least two upflow zones,with estimated even spacing of about 5-8 km in the mapped area.The repeated appearance of sulfide-sulfate or sulfide-carbonate rhythmic units in the area suggests episodically venting of fluids through the upflow conduits by breaking the overlying seals of the hydrothermal aquifer.  相似文献   

14.
INTRODUCTION Volcanoesaremostlyobservedinoceanicridges,hotspotsandcontinentalriftzones(Hongetal.,2003),andarerarelyobservedincontinentalinteri ors.However,sincethevolcanoeswithintheconti nentinteriorscannotbeattributedtotheplate/block marginprocess,theydr…  相似文献   

15.
The presence of the reversals of the geomagnetic field within the Brunhes is indicated by paleomagnetic stuides on Cenozoic volcanic rocks in the Leizhou Peninsula, loess strata and Quaternary marine sediments in the Pearl River Mouth basin in China. These regional reversals occured at 0.58±0.13 Ma, 0.45 Ma and 0.47—0.48 Ma respectively according to the results of K-Ar isotopic dating and climatostratigraphic and biostratigraphic analyses. The reversals equivalent to the Emperor Event is suggested.The reversals revealed in different regions with various lithologic characters in China prove that the Emperor Event is a global reversal event rather than a geomagnetic excursion, and its confirmation will permit a precise definition of the Middle/Late Pleistocene boundary.  相似文献   

16.
The aims of present study are investigation of endemic plants at Masjed–Daghi area introducing hyperaccumulator and indicator plants for Au, Ag, As, Cu, Mo, Hg, Re, Sb, and Te mineralization and also describe the biogeochemical response pattern over a known Au–Cu mineralized site. The Masjed–Daghi prospecting area is covered by Eocene flysch, andesite, trachyandesite, dacite, rhyodacite, Oligocene agglomerate, and Quaternary deposits. Previous researches reported copper porphyry mineralization and related epithermal gold veins in this area. This study presents that plants with high metal intake enabled us to obtain invaluable information about natural concentrations of chemical elements in the substrate and to recognize new potential areas for mineral prospecting. Stachys inflata has biological absorption coefficient mean exceeding or near hyperaccumulating criterion >1 for most of the elements investigated then could be as a hyperaccumulator. The indicator values belong to S. inflata, Artemisia sp., Salvia sp., Astragalus sp., Peganum harmala, Moltkia coerulea, and Cousinia sp.  相似文献   

17.
Conditions for the Formation of oil and gas pools in Tertiary volcanics in the western part of the Huimin sag, Shandong and then (?)stribution have been studied based on the geological, seismic and well-logging information. In this paper, the types and lithofacies of the volcanic rocks in the western part of the Huimin sag are described; the relationship between rocks and electrical properties, the seismic reflection structures, the development and distribution of the volcanic rocks are expounded; and the fourfold role of the volcanic activities in the formation of the oil and gas pools is also dealt with. It is considered by the authors that the volcanic activities were not destructive to the formation of oil and gas pools but a factor favourable to the accumulation of organic matters and their conversion to hydrocarbon. The volcanic rocks might have served as reservoir rocks and cap rocks, or as a synsedimentary anticline. The prerequisites and important factors for the formation of oil and gas pools and their distribution are pointed out in the paper.  相似文献   

18.
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19.
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20.
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