共查询到20条相似文献，搜索用时 31 毫秒
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RésuméÀ la suite d’un violent orage, une lave torrentielle d’un volume supérieur à 100 000 m3 s’est répandue sur le cône de déjection du torrent du Bez, provoquant des dégâts considérables aux infrastructures. Les observations réalisées durant l’événement et les investigations menées dans le bassin versant nous permettent de mieux comprendre le déclenchement de cette lave. Le flot boueux marquant le début de l’événement a été en grande partie alimenté par les ravinements affectant le haut du bassin versant. La lave à blocs qui a suivi s’est nourrie quant à elle des dépôts morainiques recouvrant la rive gauche du torrent, dans la partie inférieure du bassin versant. Au lendemain de la crue, on pouvait observer deux grandes entailles d’une profondeur maximale de 15 m. L’instabilité des berges qui en résultait a alors été rapidement enrayée par d’importants travaux de terrassements et d’enrochements. © Elsevier, Paris 相似文献
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《中国地质大学学报(英文版)》2000,(2)
The petrography,the geochemistry and the burial his-tory all constrain the origin and m odification history ofdolomites in an ancient periplatform carbonate slope deposit,the Machari Form ation (late Middle to early L ate Cambrian) ,Korea.The formation is mainly composed of rhythmic bed-ding,lam inated to bedded lime mudstone alternating withargillaceous lime mudstone.The rhythm ic bedding is a prod-uct of the deposition of offshore periplatform ooze andhemipelagic clay on a periplatform slo… 相似文献
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Zhang Shengye Wei Sheng Wang JiayingDepartment of Applied Geophysics China University of Geosciences Wuhan Zhang Xianjueth Geophysical Prospecting Team of Central South Bureau of Petroleum Geology Ministry oj Geology Mineral Resources X 《中国地质大学学报(英文版)》1995,(2)
In order to study the deep geoelectrical structure and the regional geological structure and detect potential oil and gas areas in Qiangtang basin in northern Xizang (Tibet), 222 MT soundings were conducted along three N - S MT profiles across the basin .The MT results indicate that the south and north parts of the Qiangtang basin have a good contrast in the deep electrical structure . In the south Qiangtang , there are generally two high conductivity layers in the crust . The first is at a depth of about 10-25 km and possesses a resistivity of about 10-80 Ωm . The second, the high conductivity layer in the lower crust, is at a depth of about 40-70 km with 3- 50 Ωm . In the north Qiangtang , there is generally one high conductivity layer . It is at a depth of about 10-30 km and the resistivity is about 1-60 Ωm . The thickness of the second high conductivity layer in both the south Qiangtang and the Bangong-Nujiang suture is much greater than that of the first . The thickness of the lithosphere is abou 相似文献
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Shahram AVARJANI Asadollah MAHBOUBI Reza MOUSSAVI-HARAMI Hassan AMIRI-BAKHTIAR 《《地质学报》英文版》2014,88(3):931-948
The Asmari Formation deposited in the Zagros foreland basin during the OligoceneMiocene. Lithologically, the Asmari Formation consists of limestone, dolomitic limestone, dolomite, argillaceous limestone, some anhydrite(Kalhur Member) and sandstones(Ahwaz Member). This study is based on the analysis of core samples from four subsurface sections(wells Mn-68, Mn-281, Mn-292 and Mn-312) in the Marun Oilfield in the Dezful embayment subzone in order to infer their provenance and tectonic setting of the Ahwaz Sandstone Member. Petrographical data reveal that the Ahwaz Sandstone comprises 97.5% quartz, 1.6% feldspar, and 0.9% rock fragments and all samples are classified as quartz arenites. The provenance and tectonic setting of the Ahwaz Sandstone have been assessed using integrated petrographic and geochemical studies. Petrographic analysis reveals that mono- and poly-crystalline quartz grains from metamorphic and igneous rocks of a craton interior setting were the dominant sources. Chemically, major and trace element concentrations in the rocks of the Ahwaz Sandstone indicate deposition in a passive continental margin setting. As indicated by the CIW′ index(chemical index of weathering) of the Ahwaz Sandstone(average value of 82) their source area underwent "intense" recycling but "moderate to high" degree of chemical weathering. The petrography and geochemistry results are consistent with a tropical, humid climate and low-relief highlands. 相似文献
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《Chemie der Erde / Geochemistry》2022,82(4):125915
Thermodynamic properties of several TeO2 polymorphs and metal tellurites were measured by a combination of calorimetric techniques. The most stable TeO2 polymorph is α-TeO2, with its enthalpy of formation (ΔfHo) selected from literature data as ?322.0 ± 1.3 kJ·mol?1. β-TeO2 is metastable (in enthalpy) with respect to α-TeO2 by +1.40 ± 0.07 kJ·mol?1, TeO2 glass by a larger amount of +14.09 ± 0.11 kJ·mol?1. >200 experimental runs and post-synthesis treatments were performed in order to produce phase-pure samples of Co, Cu, Mg, Mn, Ni, Zn tellurites. The results of the hydrothermal and solid-state syntheses are described in detail and the products were characterized by powder X-ray diffraction. The standard thermodynamic data for the Te(IV) phases are (standard enthalpy of formation from the elements, ΔfHo in kJ·mol?1, standard third-law entropy So in J·mol?1·K?1): Co2Te3O8: ΔfHo = ?1514.2 ± 6.0, So = 319.2 ± 2.2; CoTe6O13: ΔfHo = ?2212.5 ± 8.1, So = 471.7 ± 3.3; MgTe6O13: ΔfHo = ?2525.8 ± 7.9, So = 509.2 ± 3.6; Ni2Te3O8: ΔfHo not measured, So = 293.3 ± 2.1; NiTe6O13: ΔfHo = ?2198.7 ± 8.2, So = 466.5 (estimated); CuTe2O5: ΔfHo = ?820.2 ± 3.3, So = 187.2 ± 1.3; Zn2Te3O8: ΔfHo = ?1722.5 ± 4.0, So = 299.3 ± 2.1. The solubility calculations show that the Te(IV) concentration in an aqueous phase, needed to produce such phases, must be at least 3–5 orders of magnitude higher than the natural Te background concentrations. The occurrence of these minerals, as expected, are restricted to hotspots of Te concentrations. In order to produce more reliable phase diagrams, more work needs to be done on the thermodynamics of potential competing phases in these systems, including Te(VI) phases. 相似文献
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Tolga Oyman 《Ore Geology Reviews》2010,37(3-4):175-201
The Ayazmant Fe–Cu skarn deposit is located approximately 20 km SE of Ayval?k or 140 km N of Izmir in western Turkey. The skarn occurs at the contact between metapelites and the metabasites of the Early Triassic K?n?k Formation and the porphyritic hypabyssal intrusive rocks of the Late Oligocene Kozak Intrusive Complex. The major, trace, and rare earth-element geochemical analysis of the igneous rocks indicate that they are I-type, subalkaline, calc-alkaline, metaluminous, I-type products of a high-level magma chamber, generated in a continental arc setting. The 40Ar–39Ar isochron age obtained from biotite of hornfels is 20.3 ± 0.1 Ma, probably reflecting the age of metamorphic–bimetasomatic alteration which commenced shortly after intrusion into impure carbonates. Three stages of skarn formation and ore development are recognized: (1) Early skarn stage (Stage I) consisting mainly of garnet with grossular-rich (Gr75–79) cores and andradite-rich (Gr36–38) rims, diopside (Di94–97), scapolite and magnetite; (2) sulfide-rich skarn (Stage II), dominated by chalcopyrite with magnetite, andraditic garnet (Ad84–89), diopside (Di65–75) and actinolite; and (3) retrograde alteration (Stage III) dominated by actinolite, epidote, orthoclase, phlogopite and chlorite in which sulfides are the main ore phases. 40Ar–39Ar age data indicate that potassic alteration, synchronous or postdating magnetite–pyroxene–amphibole skarn, occurred at 20.0 ± 0.1 Ma. The high pyroxene/garnet ratio, plus the presence of scapolite in calc-silicate and associated ore paragenesis characterized by magnetite (± hematite), chalcopyrite and bornite, suggests that the bulk of the Ayazmant skarns were formed under oxidized conditions. Oxygen isotope compositions of pyroxene, magnetite and garnet of prograde skarn alteration indicate a magmatic fluid with δ18O values between 5.4 and 9.5‰. On the basis of oxygen isotope data from mineral pairs, the early stage of prograde skarn formation is characterized by pyroxene (Di94–97)-magnetite assemblage formed at an upper temperature limit of 576 °C. The lower temperature limit for magnetite precipitation is estimated below 300 °C, on the basis of magnetite–calcite pairs either as fracture-fillings or massive ore in recrystallized limestone-marble. The sulfide assemblage is dominated by chalcopyrite with subordinate molybdenite, pyrite, cubanite, bornite, pyrrhotite, galena, sphalerite and idaite. Gold–copper mineralization formed adjacent to andradite-dominated skarn which occurs in close proximity to the intrusion contacts. Native gold and electrum are most abundant in sulfides, as fine-grained inclusions; grain size with varying from 5 to 20 µm. Sulfur isotope compositions obtained from pyrrhotite, pyrite, chalcopyrite, sphalerite and galena form a narrow range between ? 4.8 and 1.6‰, suggesting the sulfur was probably mantle-derived or leached from magmatic rocks. Geochemical data from Ayazmant shows that Cu is strongly associated with Au, Bi, Te, Se, Cd, Zn, Pb, Ni and Co. The Ayazmant mineralizing system possesses all the ingredients of a skarn system either cogenetic with, or formed prior to a porphyry Cu(Au–Mo) system. The results of this study indicate that the Aegean Region of Turkey has considerable exploration potential for both porphyry-related skarns and porphyry Cu and Au mineralization. 相似文献
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J. F. Lindsay 《Australian Journal of Earth Sciences》2013,60(1):127-139
The Neoproterozoic Heavitree Quartzite is widespread in the Amadeus Basin and has correlatives in all of the major central Australian intracratonic basins. The origin of the formation is enigmatic, not only because of its widespread sheet‐like distribution and uniformity of composition, but also because intense silicification makes facies studies difficult. Recently discovered exposures at the eastern end of the basin are relatively free of diagenetic quartz allowing a detailed study of sedimentary structures and an understanding of the depositional architecture of the formation. The formation, which consists largely of pale‐tan or white quartzose sandstone interbedded with rare laminated mudstone and conglomerate intervals, was deposited in at least four depositional sequences. The sheet‐like nature of the sandstone results from an abundant supply of sediments deposited in a high‐energy, open, shelf‐like environment on a regionally subsiding, low‐gradient ramp. Environmental settings switched both laterally and temporally between sand waves deposited by reversing tidal flow and higher velocity unidirectional currents involving dunes and plane beds. In the early stages of deposition, mud‐dominated, tidal‐flat environments alternated with higher energy, sand‐dominated, tidally influenced settings. However, in the later stages of deposition a major eustatic sea‐level fall moved base‐level basinwards, earlier sediments were reworked by streams to form a ravinement surface, gravel was carried well into the basin and fines largely disappeared from the environment. Gravel deposition was followed by a return to high‐energy, tidally influenced deposits involving large sand waves or dunes. Towards the top of the formation sand waves deposited by reversing tidal currents gradually decline and are eventually replaced by dunes deposited by unidirectional current flow. The transition to the shallow‐marine, anoxic rocks of the Bitter Springs Formation is gradational in response to increased accommodation in a ramp setting which lacked a clearly defined shelf break. The Heavitree Quartzite was probably deposited as a direct response to the events surrounding the assembly and breakup of Rodinia, in particular peneplanation during regional uplift in response to a rising mantle plume followed by broad regional subsidence as the plume decayed prior to the breakup of the supercontinent. The large supply of quartz sand resulted from peneplanation associated with the rising plume and the lack of soil‐stabilising vascular plants, an environmental setting with no modern analogue. The ultimate disposition of fines is not known but, given the environment of deposition, it is likely that they were removed during peneplanation and bypassed the sag basin completely. 相似文献
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