岩溶泉流量衰减曲线分析   总被引：5，自引：0，他引：5       下载免费PDF全文

常勇  吴吉春  刘玲  罗跃 《水文》2016,36(1):15-21

由于岩溶含水介质的强烈非均质性和各向异性,如何有效认识岩溶含水层内部的水文地质特征为研究难点之一,岩溶泉衰减曲线分析为认识岩溶含水层的一种有效手段。总结了目前广泛用于泉流量衰减曲线分析的几种常见方法,主要包括指数型衰减、非指数型衰减分析方法以及综合型的衰减曲线分析方法,讨论了管道可能对泉流量衰减曲线的影响,最后提出了今后对岩溶泉流量衰减曲线分析拟解决的一些关键问题。  相似文献   

松嫩平原哈尔滨地区地下水环境背景值分析          下载免费PDF全文

李天宇  董宏志  孔庆轩  卞建民 《水文》2016,36(3):24-28

受自然条件及人类活动的影响,地下水环境发生了较大的变化,地下水污染问题日益引起广泛的关注。正确确定背景值对地下水污染评价十分重要。以收集的松嫩平原哈尔滨地区150余组地下水水化学样品分析数据为依据,在分析区域流场、补给径流条件的基础上,选用数理统计法和经验法求取了研究区潜水和承压水地下水环境背景值,并对地下水环境背景值进行比较。结果表明:数理统计法以自然地理环境和人类长期活动的综合作用为基础,克服了经验法的不足,可较真实地反映研究区地下水背景状况;研究区内潜水中指标NO3-、Fe、Mn和承压水中指标Fe、Mn均为高背景值指标;区内地下水环境背景值与人类活动、地下水的补、径、排和沉积环境条件具有密切的关系。  相似文献   

P–T–t evolution of garnet amphibolites in the Wutai–Hengshan area,North China Craton: insights from phase equilibria and geochronology          下载免费PDF全文

J. H. Qian  C. J. Wei 《Journal of Metamorphic Geology》2016,34(5):423-446

Garnet amphibolites can provide valuable insights into geological processes of orogenic belts, but their metamorphic evolution is still poorly constrained. Garnet amphibolites from the Wutai–Hengshan area of the North China Craton mainly consist of garnet, hornblende, plagioclase, quartz, rutile and ilmenite, with or without titanite and epidote. Four samples selected in a south–north profile were studied by the pseudosection approach in order to elucidate the characteristics of their metamorphic evolution, and to better reveal the northwards prograde change in <i>P–T</i> conditions as established previously. For the sample from the lower Wutai Subgroup, garnet exhibits obvious two‐substage growth zoning characteristic of pyrope (<i>X</i><sub>py</sub>) increasing but grossular (<i>X</i><sub>gr</sub>) decreasing outwards in the core, and both <i>X</i><sub>py</sub> and <i>X</i><sub>gr</sub> increasing outwards in the rim. Phase modelling using thermocalc suggests that the garnet cores were formed by chlorite breakdown over 7–9 kbar at 530–600 °C, and rims grew from hornblende and epidote breakdown over 9.5–11.5 kbar at 600–670 °C. The isopleths of the minimum An in plagioclase and maximum <i>X</i><sub>py</sub> in garnet were used to constrain the peak <i>P–T</i> conditions of ~11.5 kbar/670 °C. The modelled peak assemblage garnet + hornblende + epidote+ plagioclase + rutile + quartz matches well the observed one. Plagioclase–hornblende coronae around garnet indicate post‐peak decompression and fluid ingress. For the samples from the south Hengshan Complex, the garnet zoning weaken gradually, reflecting modifications during decompression of the rocks. Using the same approach, the rocks are inferred to have suprasolidus peak conditions, increasing northwards from 11.5 kbar/745 °C, 12.5 kbar/780 °C to 13 kbar/800 °C. Their modelled peak assemblages involve diopside, garnet, hornblende, plagioclase, rutile and quartz, yet diopside is not observed petrographically. The post‐peak decompression is characterized by diopside + garnet + quartz + melt = hornblende + plagioclase, causing the diopside consumption and garnet compositions to be largely modified. Thus, the pesudosection approach is expected to provide better pressure results than conventional thermobarometry, because the later approach cannot be applied with confidence to rocks with multi‐generation assemblages. U–Pb dating of zircon in the Wutai sample records a protolith age of <i>c</i>. 2.50 Ga, and a metamorphic age of <i>c</i>. 1.95 Ga, while zircon in the Hengshan samples records metamorphic ages of <i>c</i>. 1.92 Ga. The <i>c</i>. 1.95 Ga is interpreted to represent the pre‐peak or peak metamorphic stages, and the ages of <i>c</i>. 1.92 Ga are assigned to represent the cooling stages. All rocks in the Wutai–Hengshan area share similar clockwise <i>P–T</i> morphologies. They may represent metamorphic products at different crustal depths in one orogenic event, which included a main thickening stage at <i>c</i>. 1.95 Ga followed by a prolonged uplift and cooling after 1.92 Ga.  相似文献   

Time‐scale of deformation and intertectonic phases revealed by P–T–D–t relationships in the orogenic middle crust of the Orlica‐Śnieżnik Dome,Polish/Czech Central Sudetes     

E. Skrzypek  J. Lehmann  J. Szczepański  R. Anczkiewicz  P. Štípská  K. Schulmann  A. Kröner  D. Białek 《Journal of Metamorphic Geology》2014,32(9):981-1003

A section of the orogenic middle crust (Orlica‐?nie?nik Dome, Polish/Czech Central Sudetes) was examined to constrain the duration and significance of deformation (D) and intertectonic (I) phases. In the studied metasedimentary synform, three deformation events produced an initial subhorizontal foliation S1 (D<sub>1</sub>), a subsequent subvertical foliation S2 (D<sub>2</sub>) and a late subhorizontal axial planar cleavage S3 (D<sub>3</sub>). The synform was intruded by pre‐, syn‐ and post‐D<sub>2</sub> granitoid sheets. Crystallization–deformation relationships in mica schist samples document I<sub>1–2</sub> garnet–staurolite growth, syn‐D<sub>2</sub> staurolite breakdown to garnet–biotite–sillimanite/andalusite, I<sub>2–3</sub> cordierite blastesis and late‐D<sub>3</sub> chlorite growth. Garnet porphyroblasts show a linear Mn–Ca decrease from the core to the inner rim, a zone of alternating Ca–Y‐ and P‐rich annuli in the inner rim, and a Ca‐poor outer rim. The Ca–Y‐rich annuli probably reflect the occurrence of the allanite‐to‐monazite transition at conditions of the staurolite isograd, whereas the Ca‐poor outer rim is ascribed to staurolite demise. The reconstructed <i>P</i>–<i>T</i> path, obtained by modelling the stability of parageneses and garnet zoning, documents near‐isobaric heating from ~4 kbar/485 °C to ~4.75 kbar/575 °C during I<sub>1–2</sub>. This was followed by a progression to 4–5 kbar/580–625 °C and a subsequent pressure decrease to 3–4 kbar during D<sub>2</sub>. Pressure decrease below 3 kbar is ascribed to I<sub>2–3</sub>, whereas cooling below ~500 °C occurred during D<sub>3</sub>. In the dated mica schist sample, garnet rims show strong Lu enrichment, oscillatory Lu zoning and a slight Ca increase. These features are also related to allanite breakdown coeval with staurolite appearance. As Lu‐rich garnet rims dominate the Lu–Hf budget, the 344 ± 3 Ma isochron age is ascribed to garnet crystallization at staurolite grade, near the end of I<sub>1–2</sub>. For the dated sample of amphibole–biotite granitoid sheet, a Pb–Pb single zircon evaporation age of 353 ± 1 Ma is related to the onset of plutonic activity. The results suggest a possible Devonian age for D<sub>1</sub>, and a Carboniferous burial‐exhumation cycle in mid‐crustal rocks that is broadly coeval with the exhumation of neighbouring HP rocks during D<sub>2</sub>. In the light of published ages, a succession of telescoping stages with time spans decreasing from <i>c</i>. 10 to 2–3 Ma is proposed. The initially long period of tectonic quiescence (I<sub>1–2</sub> phase, <i>c</i>. 10 Ma) inferred in the middle crust contrasts with contemporaneous deformation at deeper levels and points to decoupled <i>P</i>–<i>T</i>–<i>D</i> histories within the orogenic wedge. An elevated gradient of ~30 °C km<sup>?1</sup> and assumed high heating rates of <i>c</i>. 20 °C Ma<sup>?1</sup> are explained by the protracted intrusion of granitoid sheets, with or without deformation, whereas fast vertical movements (2–3 Ma, D<sub>2</sub> phase) in the crust require the activity of deformation phases.  相似文献   

Proterozoic low-pressure/high-temperature metamorphism and an anticlockwise P–T–t path for the Hazeldene area, Mount Isa Inlier, Queensland, Australia     

M. J. RUBENACH 《Journal of Metamorphic Geology》1992,10(3):333-346

In the Hazeldene area, situated in the Mount Isa Inlier, Queensland, the metamorphic grade changes from chlorite zone, through biotite and cordierite zones, to sillimanite/K-feldspar zone.
Microstructural studies of rocks near the sillimanite isograd demonstrate that cordierite grew early during the development of a steep foliation (S2), was replaced by biotite, andalusite and sillimanite at the metamorphic peak late in S2, and in turn by kyanite + chlorite adjacent to localized small post-D2 shear zones. Although the anticlockwise P–T–t path is well defined, the precise P–T conditions are uncertain because of problems with experimental and thermodynamic data. The best estimate for the metamorphic peak for rocks close to the sillimanite isograd is around 600° C at 4 kbar.
The metamorphism has been dated at 1544 Ma, and was synchronous with a major crustal shortening event. Because proposed extensional events occurred more than 60 Ma earlier, their contribution to the peak metamorphic thermal perturbation would have been insignificant. The syn-metamorphic Mica Creek Pegmatites, the abundance of high heat-producing elements in the nearby pre-D2 Sybella Granite, and advective heat by fluids which caused considerable metasomatism in the Hazeldene area, may have each contributed to the thermal budget. However, the metamorphic thermal gradient may be 80°C km^-1 or higher, strongly suggesting a local magmatic control. As none are known in the area, such syn-metamorphic plutons would have to lie beneath the exposed high-grade rocks.  相似文献   

新县高压超高压榴辉岩及变质作用     

张宗恒  任爱琴  侯海燕 《河南国土资源》2001,(1)

大别造山带西段的新县高压超高压变质带中 ,分布着多种不同类型的榴辉岩。研究发现 ,尽管它们有着不同的峰变质条件 ,但都经历了相同的绿帘角闪岩相前进变质 ,具有相近的峰变质年龄和相似的退变质轨迹。其形成和折返可能与华北、扬子两大古陆在早奥陶世末的陆—陆碰撞有关。  相似文献   

沙溪斑岩型铜(金)矿床成矿地球化学研究及靶区圈定   总被引：1，自引：0，他引：1  

杨晓勇  王奎仁  孙立广  杨学明  黄德志  李英贤  石昆发 《大地构造与成矿学》2002,26(3):263-270

沙溪和菖蒲山地区位于扬子金属成矿带中部,前者是一个已经探明并圈定地质储量的中型斑岩型铜(金)矿床.本文通过地质-地球化学-地球物理综合研究,在沙溪矿床的邻区———菖蒲山地区预测并应用高精度地球物理方法圈定了一个与已知矿床规模相近的斑岩铜矿成矿异常区,该异常区由硫化物矿化所引起,呈北北东展布,长1500m,宽500m,总面积接近0.8km2。本文提出了一个斑岩型铜矿的控矿模型,结合区域资料和前人关于我国铜矿成矿研究成果,综合分析得出,本区为形成大型斑岩型铜(金)矿床的有利成矿远景区。  相似文献   

工程控制网的稳定性研究     

吴杰  余腾  潘庆林 《测绘科学》2011,36(5):31-33

工程控制网的点位差异是由于观测误差引起的,还是由位移引起的,必须对其进行区分.本文简要介绍了整体稳定性检验的平均间隙法、单点位移稳定性的间隙分块法、限差法和t检验法,并结合具体的实例进行分析,得出了有益的结论.  相似文献   

MÉTHODE D'ÉTUDE DES NAPPES LIBRES DANS LES AQUIFÈRES ANISOTROPES     

Claude VIGUIER 《水文科学杂志》2013,58(1):21-27

<b>Abstract</b></p> The necessary and sufficient conditions for non-zero phase shift and non-zero attenuation in linear flood routing can be derived from the continuity equation alone and are found to depend on the existence of an imaginary part in the expression for frequency or in the expression for wave number. It is shown that in linear flood routing the phase lag between flow rate and area of flow is directly related to the attenuation per unit wave length. The effects of using various forms of the momentum equation, in addition to the continuity equation, are exemplified by deriving analytical expressions in terms of the frequency, both for attenuation per unit channel length and for phase shift, for the kinematic wave, the general diffusion analogy, and the complete St. Venant equation.  相似文献   

Diachronic metamorphic and structural evolution of the Connecticut Valley–Gaspé trough,Northern Appalachians     

Morgann Perrot  Alain Tremblay  Gilles Ruffet  Loic Labrousse  Félix Gervais  Fabien Caroir 《Journal of Metamorphic Geology》2020,38(1):3-27

The Connecticut Valley–Gaspé (CVG) trough represents a major, orogen-scale Silurian–Devonian basin of the Northern Appalachians. From Gaspé Peninsula to southern New England, the CVG trough has experienced a contrasting metamorphic and structural evolution during the Acadian orogeny. Along its strike, the CVG trough is characterized by increasing strain and polyphase structures, and by variations in the intensity of regional metamorphism and contrasting abundance of <i>c</i>. 390–370 Ma granitic intrusions. In southern Quebec and northern Vermont, a series of NW–SE transects across the CVG trough have been studied in order to better understand these along-strike variations. Detailed structural analyses, combined with phase equilibria modelling, Raman spectrometry, and muscovite <sup>40</sup>Ar/<sup>39</sup>Ar dating highlight a progressive and incremental deformation involving south–north variation in the timing of metamorphism. Deformation evolves from a D<sub>1</sub> crustal thickening event which originates in Vermont and progresses to southern Québec where it peaked at 0.6 GPa/380°C at <i>c</i>. 375 Ma. This was followed by a D<sub>2</sub> event associated with continuous burial in Vermont from 378 to 355 Ma, which produced peak metamorphic conditions of 0.85 GPa/380°C and exhumation in Quebec from 368 to 360 Ma. The D<sub>3</sub> compressional exhumation event also evolved from south to north from 345 to 335 Ma. D<sub>1</sub> to D<sub>3</sub> deformation events form part of a continuum with an along-strike propagation rate of ~50 km/Ma During D<sub>1</sub>, the burial depth varied by more than 15 km between southern Quebec and Vermont, and this can be attributed to the occurrence of a major crustal indenter, the Bronson Hill Arc massif, in the New England segment of the Acadian collision zone.  相似文献