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1.
Characteristic mineralogy of the Zhutishi granite:Implication for petrogenesis of the late intrusive granite 总被引：3，自引：0，他引：3
Many granitic batholiths occur in the form of com-plexes, presented principally by a temporal-spacial association between two stages of intrusion, in the Nanling region. Compared with main intrusive gran-ites, late intrusive granites are characterized by fine- grained texture, Si- and Al-enriched composition, and small occurrence as stock or apophysis. On the basis of its rock chemistry (e.g., increasing aluminium saturation index) and geochemistry (e.g., Eu depletion, decreasing concentratio… 相似文献
2.
V. S. Kuksenko E. E. Damaskinskaya A. G. Kadomtsev 《Izvestiya Physics of the Solid Earth》2011,47(10):879-885
Mechanisms of fracture of granite specimens subjected to loading controlled by the defect formation rate are studied in the
experiments on stick-slip initiation and deformation of water-saturated specimens from the acoustic emission measurements.
It is found that under mechanical loading of dry specimens, the initially dispersed formation of defects is followed by the
stage of their localization, and then a fracture nucleates whose development results in the formation of macrofracture and
failure of the specimen. In water-saturated specimens, multiple defects are formed randomly throughout the entire volume,
which causes intense damage to the material. At the final stage of deformation, several source regions appear in which the
main cracks develop. If fracturing follows the stick-slip scenario, the stoppers located on the sides of the fault are destroyed. 相似文献
3.
Summary Gamma-ray spectra of the samples were measured by standard laboratory multichannel spectrometry. The weighted least squares method was applied to the digital output data in order to determine the concentrations of U238, Th232 and K40 present. U and Th increase towards the rim of the massif (from 4 ppm U and 20 ppm Th in the coarse-grained central facies to 23 ppm U and 42 ppm Th in the fine-grained rim variety), whereas K remains fairly constant at 3.85%.On leave Eidgenössische Technische Hochschule, Zurich (Switzerland) 相似文献
4.
A pumping test in a granite aquifer provides information about the interaction between the upper weathered zone and lower fractured zone. A radial flow numerical model is used to interpret the test and estimate aquifer parameters. This model successfully reproduces both the fractured zone response and the shallow weathered zone response which is characterised by increasing drawdown even after abstraction ceases. When the deep fractured aquifer was exploited, a serious decline in groundwater heads and yields occurred; this behaviour can be reproduced by the model. The model is then used to investigate the effective long-term exploitation of the aquifer and the results indicate that dug-cum-bore wells can be used for the safe and efficient exploitation of the aquifer resources. 相似文献
5.
An understanding of the frictional sliding on faults that can lead to earthquakes requires a knowledge of both constitutive behavior of the sliding surfaces and its mechanical interaction with the loading system. We have determined the constitutive parameters for frictional sliding of initially bare surfaces of Westerly granite, using a recently developed high pressure rotary shear apparatus that allows long distances of sliding and therefore a greater assurance of attaining steady state behavior. From experiments conducted at room temperature and normal stresses of 27–84 MPa several important results have been found. (1) A gouge layer 100 to 200 m thick was developed from the initially bare rock surfaces after 18 to 70 mm of sliding. (2) The steady state frictional resistance, attained after about 10 mm of sliding, is proportional to the negative of the logarithm of the sliding velocity. (3) Abrup changes in the velocity of sliding result in initial changes in the frictional resistance, which have the same sign as the velocity change, and are followed by a gradual decay to a new steady state value over a characteristic distance of sliding. This velocity weakening behavior is essentially identical with that found by several previous workers on the same material at lower normal stress. (4) Our results are well described by a two state variable constitutive law. The values of the constitutive parameters are quite similar to those found previously at low normal stress, but the characteristic distance is about an order of magnitude smaller than that found at 10 MPa normal stress with thicker layers of coarser gouge. (5) We have approximated our results with a one state variable constitutive law and compared the results with the predictions of existing nonlinear stability analysis; in addition, we have extended the stability analysis to systems possessing two state variables. With such formulations good agreement is found between the experimentally observed and theoretically predicted transitions between stable and unstable sliding. These results allow a better understanding of the instabilities that lead to earthquakes. 相似文献
6.
Illman and Tartakovsky (2005a, 2005b) developed a new approach for the interpretation of three-dimensional pneumatic well tests conducted in porous or fractured geologic media, which is based on a straight-line analysis of late-time data. We modify this approach to interpret three-dimensional well tests in the saturated zone and use it to analyze the cross-hole hydraulic test data collected in the Full-Scale Engineered Barrier Experiment gallery at the Grimsel Test Site in Switzerland. The equivalent hydraulic conductivity and specific storage obtained from our analysis increase with the radial distance between the centroids of the pumping and monitoring intervals. Since this scale effect is observed from a single test type (cross-hole tests), it is less ambiguous than scale effects typically inferred from laboratory and multiple types of hydraulic tests (e.g., slug, single- and cross-hole tests). The statistical analysis of the estimated hydraulic parameters shows a strong correlation between equivalent hydraulic conductivity and specific storage. 相似文献
7.
A sample of Westerly granite was deformed under constant stress conditions: a pore pressure of 5 MPa, a confining pressure of 10 MPa, and an axial load of 170 MPa. Pore volume changes were determined by measuring the volume of pore fluid (0.01M KClaq) injected into the sample. After 6 days of creep, characterized by accelerating volumetric stain, the sample failed along a macroscopic fault. Measurements of complex resistivity over the frequency range 0.001–300 Hz, taken at various times during creep, showed a gradual increase in both conductivity and permittivity. When analysed in terms of standard induced polarization (IP) techniques, the changing complex resistivity resulted in systematic changes in such parameters as percent frequency effect and chargeability. These results suggest that it may be possible to monitor the development of dilatancy in the source region of an impending earthquake through standard IP techniques. 相似文献
8.
9.
为开展秦岭翠华山等大型花岗岩地震山崩的动力响应机制研究,研发配制用于振动台物理模型试验的花岗岩相似材料是该研究工作的基础。选取铁矿粉、石英砂、重晶石粉为骨料,石膏为调节材料,松香酒精溶液为黏结剂的相似材料配比方案,设计考虑4因素5水平的正交试验,并对试验结果进行极差分析及多元线性回归拟合,获得各因素对花岗岩相似材料物理力学性质的影响结果和相似材料配比经验方程。结果表明：花岗岩相似材料的密度随铁粉与重晶石粉占骨料比的增加而增大;随着黏结剂浓度的增加,花岗岩相似材料的抗压强度、弹性模量及黏聚力均显著增大;随着石膏含量的增加,密度、抗压强度及内摩擦角均减小。该试验得到的相似材料配比经验方程可以较好地为花岗岩相似材料或其他相似材料的配制提供参考。 相似文献
10.
Origin of Li-F-rich granite: Evidence from high P-T experiments 总被引：2，自引：0，他引：2
LI Fuchun ZHU Jinchu RAO Bing JIN Zhangdong & ZHANG Linsong . School of Resource Environment Sciences Nanjing Agriculture University Nanjing China . State Key Laboratory for Mineral Deposits Research Nanjing University Nanjing China . Nanjing Institute of Geography Limnology Chinese Academy of Sciences Nanjing China 《中国科学D辑(英文版)》2004,47(7):639-650
In South China and some regions around the world, there is a special type of rocks. These rocks are usually ultra-acidic, peraluminous, rich in Na and volatile components, such as H2O, F, B and P, and with higher concentrations of lithophile rare metal elements, including Li, Rb, Cs, Be, Ta, Nb, Sn, W, etc. Rocks of this type are commonly called Li-F-rich, rare-metal bearing granitic rocks, or Li-F granites for short[1]. The economic importance and distinct forma-tion mechanism of Li-… 相似文献
11.
The majority of geomorphological papers about Dartmoor have been essentially speculative, particularly when discussing weathering processes and the evolution of the Dartmoor landscape. In contrast, this article presents a synthesis of several experimental investigations aimed at studying the chemical weathering of Dartmoor granite through the systematic analysis of soil and water samples. This involved the computation of a geochemical budget to determine the amount of erosion in the catchment, as well as more detailed mineralogical investigations within a soil profile. The annual output of solutes due to weathering was 116 kg ha?1 a?1 of which the majority was silica (93 kg ha?1 a?1). From an examination of the soil mineralogy, it was calculated that these solutes were derived from the dissolution of approximately 200 kg ha?1 a?1 plagioclase, 90 kg ha?1 a?1 biotite, and 40 kg ha?1 a?1 orthoclase. As well as the weathering of granite, there was also the production of kaolinite (150 kg ha?1 a?1) and gibbsite (0.02 kg ha?1 a?1). Analysis of the soil water chemistry confirmed that kaolinite was the stable mineral phase in the regolith, although in areas where interflow was the dominant mode of water movement, the solute composition was in equilibrium with both kaolinite and gibbsite. Examination of the clay mineralogy confirmed these results. The microtexture of quartz grains was examined by the scanning electron microscope as another means of investigating the hydrochemical environment in the soil. Silica was found precipitated on all the grains examined but the maximum amount occurred in the Bs horizon. This evidence showed that, firstly, the dissolution of aluminosilicate minerals is greater than that calculated by the chemical budget and, secondly, that models of granite weathering must take localized weathering in the soil profile into account. The final part of the paper highlights the limitations of calculating denudation rates for an entire catchment and stresses the need to consider weathering as a highly localized phenomenon, particularly where there are high volumes of interflow at hill crest sites. Observations on granite decomposition in the future should be quantitative in approach and be related to the local site conditions. 相似文献
12.
Yozo Kudo Osam Sano Naokuni Murashige Yoshiaki Mizuta Koji Nakagawa 《Pure and Applied Geophysics》1992,138(4):641-656
The double-torsion test using Aji granite was carried out to investigate the interaction between stress-induced crack path and mineral grains. Crack velocities were controlled at range 10–7 m/s to 10–1 m/s. After the stressed specimens were dyed, we checked the crack path by thin section analysis, using an optical microscope. The stress-induced crack path was divided into two types, transgranular and intergranular cracks, and each path was subdivided with respect to mineral grains. In spite of the extensive range of crack velocities, the ratios between the transgranular and intergranular crack lengths did not change. The crack paths were all jagged, and often showed detour around the grain boundary when faced with obstacles like hard grains or preexisting cracks. That is to say, quartz grain played an important role as an obstacle. Feldspar grain could change the crack path because of its cleavage plane. Biolite grain had a serious effect on the path even if its constitution ratio is very small. Fractal dimensions of the crack paths were calculated by three methods, as indicators of surface roughness. The fractal dimensions were shown in a slight trend with the change of crack velocity. This trend can be explained from the point of limited cracking rate in stress corrosion. 相似文献
13.
通常情况下花岗岩岩性稳定、岩石完整,是隧道工程的理想围岩.我国沿海地区花岗岩覆盖普遍,但因气候炎热,秋夏两季多台风暴雨,降雨量丰富,化学风化作用剧烈,使得花岗岩差异风化严重.风化作用不仅仅发生在近地表,而且深切入地下达数百米,常穿过隧道洞身.本文以新建厦门至深圳高速铁路(简称厦深高铁)某隧道工程勘察为例,采用探测深度大、工作方便的天然场源高频大地电磁测深法(HMT),探测花岗岩差异风化情况.四条相邻测线综合探测结果表明:根据HMT法二维反演剖面图中电阻率的差异,成功解释了已开挖段的施工塌陷范围,并预测了将要开挖段的强风化弱地质结构分布范围;通过垂向相对低阻异常特征定量推断了岩体风化带向下延伸情况,为隧道安全施工提供了科学指导. 相似文献
14.
Layers of artificial granite gouge have been deformed on saw-cut granite surfaces inclined 30° to the sample axes. Samples were deformed at a constant confining pressure of 250 MPa and temperatures of 22 to 845°C. The velocity dependence of the steady-state coefficient of friction (ss) was determined by comparing sliding strengths at different sliding rates. The results of these measurements are consistent with those reported bySolberg andByerlee (1984) at room temperature andStesky (1975) between 300 and 400°C. Stesky found that the slip-rate dependence of (ss) increased above 400°C. In the present study, however, the velocity dependence of (ss) was nearly independent of temperature. 相似文献
15.
Using the induced fission-track method, mobile uranium leaching and lead isotope analysis, this work obtianed geochemical features of the peraluminous Fucheng granite basement and the host rock (shoshonite) of the No. 6722 uranium deposit in southern Jiangxi Province, (i) Uranium contents of the leucocratic rock-forming minerals (0.18 μg/g for quartz, 0.36 μg/g for feldspar) are lower than the uranium content of the whole rock (4.6 μg/g). Biotite and some accessory mineral inclusions (zircon, monazite and uraninite) are the main uranium carriers of the Fucheng granite pluton. The fissure uranium in altered minerals (hydromica and chlorite) increased evidently, (ii) Leachable rate of mobile uranium in the biotite granite is 10.4⨴; while that in the altered granite increased to 31· · (iii) Caculation based on lead isotopes shows that during alteration the Fucheng granite lost uranium (AU = −37%–−65· · ), whereas the Caotaobei shoshonite gained uranium (AU = +37· ·–+58 · ·). These features suggest that the ore-forming material of the No. 6722 uranium deposit was mainly derived from the altered peraluminous granite basement of Fucheng pluton. 相似文献
16.
Biotite granite from the Sierra Nevada batholith was reacted, with known water contents in sealed platinum capsules, in a piston-cylinder apparatus between 10 and 35 kb. With the liquid just over-saturated with respect to water, temperatures for solidus and liquidus (quartz/coesite-out curve), respectively, are: 2 kb, 680°C, 715°C; 10 kb, 620°C, 725°C; 25 kb, 655°C, 800°C; 35 kb, 700°C, 850°C. The temperature interval is 35°C at 2 kb, 105°C at 10 kb, and 150°C at 35 kb, indicating that granite departs from a eutectic composition at depths greater than about 40–50 km. We conclude that crystal-liquid equilibria are not likely to yield primary rhyolite or granite magmas by partial fusion of oceanic crust in subduction zones. The solubility of water in granite liquids, in wt%, is 22.5 ± 2.5 at 25 kb and 810°C and 27 ± 2.5 at 35 kb and 850°C. These results indicate that a miscibility gap persists between water-saturated silicate magmas and aqueous vapor phase at least to pressures corresponding to 100 km depth in the mantle. The formation of kyanite near the liquidus of water over-saturated granite indicates that the aqueous vapor phase is enriched in alkalis and possibly silica, relative to the condensed phases. 相似文献
17.
Summary Strain relaxation in the Barre Granite and surrounding metasediments in Vermont, was measured by overcoring strain gauge rosettes bonded to outcrop surfaces. The average maximum expansion upon relieving 15.2 cm diameter cores trends N55°W, while the average maximum expansion of 7.6 cm diameter cores coaxial with 15.2 cm cores trends N70°W. The maximum strain relief of the internal overcores is normal to the microfracture fabric. Therefore, the mechanism of strain relaxation is attributed to the opening of microfractures either parallel to the rift direction of the Barre Granite or parallel to the foliation of the metasediment. The lack of parallelism between the normal to the rift plane and the maximum expansion of the initial overcore suggests an extenrally applied strain superimeposed on the strain caused by opening of microfractures.Lamont-Doherty Geological Observatory Contribution No. 2455. 相似文献
18.
A series of rock friction experiments has been carried out to study the complexities in rock fracture and rock friction. Intact Westerly granite samples were loaded to shear failure in a laboratory polyaxial loading apparatus. The resultant fractured samples were reloaded to cause frictional sliding. Both polyaxial loading (1 > 2 > 3 > 0) and equal confining condition (1 > 2 = 3 > 0) were used. The deformation processes were monitored by macroscopic axial stress-strain, optical holography, and ultrasonic velocity measurements.Intense localized deformation along the fracture occurred very early in the loading of fractured samples. Contacts on the fracture surfaces continuously broke during loading. No acoustic velocity anomaly was observed for the fractured sample, in contrast to a 25% drop in the velocity before the failure of the corresponding intact sample. The current study and previous research suggest that the deformation localization is an important process in governing the instability of rock friction. Instability analysis of rock friction needs to include not only the deformation processes along the sliding surfaces, but also those adjacent to the fractures such as the localized deformation along the fractures observed in the current study. The instability analysis of rock friction with rate- and state-dependent friction laws does not specifically include the deformation localization adjacent to the faults and thus ignores an important class of instability as described byRudnicki (1977).A dependence of frictional strengths on the stress components normal to the sliding and in the plane of the fracture surface was observed. This dependence can be understood by considering the loading of the irregular fracture surface under polyaxial loading conditions. This observation requires the friction laws in the macroscopic scale to be modified for those cases where the three principal stresses (1, 2, and 3) are significantly different. 相似文献
19.
Brooks B. Ellwood 《Earth and Planetary Science Letters》1981,55(2):311-316
One of the major problems in paleomagnetic sampling of granites in the southeastern United States is finding fresh outcrop. Since most outcrops are weathered to some extent, it is important to quantify the effect of weathering on the magnetic properties of individual samples. The Lake Sinclair dam site near Milledgeville, Georgia, was chosen for this study, where a very fresh, stable granite outcrops in the excavated spillway. Lying immediately above is the weathered equivalent. Drilled samples were obtained from fresh and weathered portions at one outcrop, and the remanent and induced magnetizations measured. With AF demagnetization, it was possible to obtain the stable remanent directions, exhibited by fresh samples, from all weathered samples. The induced and remanent magnetic behavior can be explained by maghemitization during weathering and the development of a secondary low oxidation magnetic phase and the reduction in domain size of primary magnetite. 相似文献
20.
Age and generation of Fogang granite batholith and Wushi diorite-hornblende gabbro body 总被引：3，自引：0，他引：3
XU XiSheng? LU WeiMin & HE ZhenYu State Key Laboratory of Crust-Mantle Evolution Mineralization Department of Earth Sciences Nanjing University Nanjing China 《中国科学D辑(英文版)》2007,50(2):209-220
Fogang granitic batholith, the largest Late Mesozoic batholith in the Nanling region, has an exposure area of ca. 6000 km2. Wushi diorite-hornblende gabbro body is situated at the northeast part of the ba- tholith. Both the granitic batholith main body and the diorite-hornblende gabbro body belong to high-K calc alkaline series. Compared with the granitic main body, the Wushi body has lower Si (49%―55%), higher Fe, Mg, Ca, lower REE, less depletion of Eu, Ba, P, Ti, and obvious depletion of Zr, Hf. Zircon LA-ICP-MS dating and the mineral-whole rock isochron dating reveal that Fogang granitic main body and Wushi body were generated simultaneously at ca. 160 Ma. The Fogang granitic main body has high (87Sr/86Sr)i ratios (0.70871―0.71570) and low εNd(t) values (?5.11―?8.93), suggesting the origins of the granitic rocks from crustal materials. Their Nd two-stage model ages range from 1.37―1.68 Ga. The Sr and Nd isotopic compositions and the Nd model ages of the granitic rocks may suggest that the giant Fogang granitic main body was generated from a heterogeneous source, with participation of mantle component. Wushi diorite-hornblende gabbro is an unusual intermediate-basic magmatic rock series, with high (87Sr/86Sr)i ratios (0.71256―0.71318) and low εNd(t) values (?7.32―?7.92), which was possibly formed through mixing between the mantle-derived juvenile basaltic magma and the magma produced by the dehydration melting of lower crustal basaltic rocks. 相似文献