浙江普陀花岗杂岩体中的石英闪长质包体：斜长石内部复杂环带研究与岩浆混合史记录   总被引：11，自引：7，他引：11  

谢磊王德滋  王汝成邱检生 陈小明 《岩石学报》2004,20(6):1397-1408

浙江普陀花岗杂岩体包含若干石英闪长质包体,该类包体中存在三种不同类型的斜长石:正常环带的斜长石、筛孔构造的斜长石和酸性斜长石为核的“反环带”斜长石。根据斜长石的环带构造特征和成分分析,认为本区的岩浆演化过程大致如下:下部基性岩浆注入到上覆酸性岩浆中并进行混合作用,酸性岩浆中已结晶的富钠质斜长石晶体进入偏基性的混合岩浆中,部分熔融形成筛孔构造;随着端员岩浆的进一步混合,富钠质斜长石晶体与中性混合熔体仅形成粗糙的边界,而保留原先构造特征;同时混合岩浆可以直接结晶出正常环带斜长石,呈单颗粒或以膜的形式包围其它环带构造的长石。本文还通过与平潭甬闪辉长岩杂岩体内筛孔斜长石的对比,认为斜长石的环带构造和成分可以反映岩浆源区特征和岩浆演化历史。  相似文献   

Observations of the spring–neap modulation of the gravitational circulation in a partially mixed estuary     

C. H. A. Ribeiro  J. J. Waniek  J. Sharples 《Ocean Dynamics》2004,54(3-4):299-306

The long-term variability of the non-tidal circulation in Southampton Water, a partially mixed estuary, was investigated using 71-day acoustic Doppler current profiler (ADCP) time series. The data show evidence that the spring–neap tidal variability of the turbulent mixing modulates the strength of the non-tidal residual circulation, with subtidal neap tide surface flows reaching 0.12 m s^–1 compared to <0.05 m s^–1 at spring tides. The amplitude of the neap-tide events in this non-tidal circulation is shown to be related to a critical value of the tidal currents, illustrating the strong dependence on tidal mixing. The results suggest that the dominant mechanism for generating these neap-tide circulation events is the baroclinic forcing of the horizontal density gradient, rather than barotropic forcing associated with ebb-induced periodic stratification. While tidal turbulence is thought to be the dominant control on this gravitational circulation, there is evidence of the additional effect of wind-driven mixing, including the effects of wind fetch and possibly wave development with along-estuary winds being more efficient at mixing the estuary than across-estuary winds. Rapid changes in atmospheric pressure also coincided with fluctuations in the gravitational circulation. The observed subtidal flows are shown to be capable of rapidly flushing buoyant material out of the estuary and into the coastal sea at neap tides.Responsible Editor: Iris Grabemann  相似文献   

像元分解法提取积雪边界线   总被引：7，自引：1，他引：7  

延昊  张国平 《山地学报》2004,22(1):110-115

利用NOAA16-AVHRR的多光谱数据进行像元分解提取积雪边界线。首先对遥感数据进行主成分分析，提取含99％信息量的前两个主分量，对其进行散点图分析，获取终元。进行多光谱混合像元分解，提取积雪盖度参数，并依据积雪盖度提取积雪边界线。同时比较了最大似然分类提取的积雪边界线，发现分类积雪边界线变化较大，而盖度积雪边界线比较稳定，主要原因是像元分解提取的积雪边界线物理意义明确。  相似文献   

拱圈在基坑支护中的应用          下载免费PDF全文

许杰  周吉祥 《探矿工程》2004,31(12):5-8

珠海市海珠广场基坑支护工程采用双排搅拌桩帷幕墙止水、拱圈支护结构挡土方案。介绍了拱圈支护结构的设计及施工中应注意的问题。经过监测，采用拱圈支护结构变位很小。  相似文献   

二元混合体系的端元Sm-Nd模式年龄计算方法          下载免费PDF全文

杨晓松  胡家杰 《地质科学》1993,28(1):37-43

报道二元混合体系的端元Sm-Nd模式年龄的计算方法,即利用二元混合体系的Rb-Sr、Sm-Nd同位素分析结果,可以计算2个端元的Sm-Nd同位素组成,两端元在混源样品中的质量百分比,以及地壳残留时间。同时计算了广西花山复式花岗岩的端元模式年龄,结果显示该岩体的物质来源于2500Ma华南古陆壳和622Ma从亏损地幔分异出来的大洋地壳的混合物。  相似文献   

岩浆的生成、运移和混合——29届国际地质大会专题简介     

孟庆丽  周永昶 《吉林大学学报(地球科学版)》1993,(3)

介绍了洋中脊玄武岩浆、岛弧岩浆、地幔热柱成因的玄武质岩浆、俯冲带岩浆、长英质岩浆、的生成问题;岩浆运移的理论及制约因素;混合岩浆的成因机制及其有关标志。  相似文献   

Silicic magma entering a basaltic magma chamber: eruptive dynamics and magma mixing — an example from Salina (Aeolian islands,Southern Tyrrhenian Sea)   总被引：1，自引：0，他引：1  

Natale Calanchi  Rosanna De Rosa  Roberto Mazzuoli  Pierluigi Rossi  Roberto Santacroce  Guido Ventura 《Bulletin of Volcanology》1993,55(7):504-522

The Pollara tuff-ring resulted from two explosive eruptions whose deposits are separated by a paleosol 13 Ka old. The oldest deposits (LPP, about 0.2 km³) consist of three main fall units (A, B, C) deposited from a subplinian column whose height (7–14 km) increased with time from A to C, as a consequence of the increased magma discharge rate during the eruption (1–8x10⁶ kg/s). A highly variable juvenile population characterizes the eruption. Black, dense, highly porphyritic, mafic ejecta (SiO₂=50–55%) almost exclusively form A deposits, whereas grey, mildly vesiculated, mildly porphyritic pumice (SiO₂=56–67%) and white, highly vesiculated, nearly aphyric pumice (SiO₂=66–71%) predominate in B and C respectively. Mafic cumulates are abundant in A, while crystalline lithic ejecta first appear in B and increase upward. The LPP result from the emptying of an unusual and unstable, compositionally zoned, shallow magma chamber in which high density mafic melts capped low density salic ones. Evidence of the existence of a short crystal fractionation series is found in the mafic rocks; the andesitic pumice results from complete blending between rhyolitic and variously fractionated mafic melts (salic component up to 60 wt%), whereas bulk dacitic compositions mainly result from the presence of mafic xenocrysts within rhyolitic glasses. Viscosity and composition-mixing diagrams show that blended liquids formed when the visosities of the two end members had close values. The following model is suggested: 1. A rhyolitic magma rising through the metamorphic basement enterrd a mafic magma chamber whose souter portions were occupied by a highly viscous, mafic crystal mush. 2. Under the pressure of the rhyolitic body the nearly rigid mush was pushed upwards and mafic melts were squeezed against the walls of the chamber, beginning roof fracturing and mingling with silicic melts. 3. When the equilibrium temperature was reached between mafic and silicic melts, blended liquids rapidly formed. 4. When fractures reached the surface, the eruption began by the ejection of the mafic melts and crystal mush (A), followed by the emission of variously mingled and blended magmas (B) and ended by the ejection of nearly unmixed rhyolitic magma (C).  相似文献   

Vertical mixing in Überlinger See,western part of Lake Constance     

Gerhard Heinz  Johann Ilmberger  Michael Schimmele 《Aquatic Sciences - Research Across Boundaries》1990,52(3):256-268

Depth variable vertical eddy diffusion coefficients for heat (K _z) were calculated from continuously measured temperature profiles in Überlinger See (western part of Lake Constance). The temperatures were averaged over vertical intervals of 10 m yielding 14 discrete values (maximum depth of Überlinger See: 147 m). A linear fit from 10 June to 29 September 1987 was used to smooth the significant temperature fluctuations caused by internal seiches of Lake Constance.Assuming horizontal homogeneity for the smoothed data the Gradient-Flux-Method was applied to compute vertical diffusion coefficientsK _z at different depths using the depth variable volumes and surfaces of the 14 layers. The resulting mean diffusion coefficients for the period from June to September are 0.04 cm²/s near the thermocline and up to 0.8 cm²/s in deeper strata (accuracy: ± 50%). It is shown that horizontal mixing between Überlinger See and Obersee (main lake) alters the computation ofK _z by less than 50%.A relationship betweenK _z and stability (Brunt-Väisälä) frequencyN is found which corresponds well to the theory of internal wave induced turbulence.Combining the diffusion coefficients with measured phosphorus profiles, a phosphorus flux from the hypolimnion to the epilimnion of (0.7 ± 0.4) mg P m^–2 d^–1 was calculated, corresponding to about 20% of the average external loading per area of Lake Constance in 1986.  相似文献   

山区卵砾石河道水流阻力计算   总被引：1，自引：1，他引：1       下载免费PDF全文

罗铭  黄尔  王协康  杨奉广 《水科学进展》1990,31(3):404-412

卵砾石河道广泛存在于山区河流中，在卵砾石河床近底层的水流流速低于上方流速，速度剖面出现拐点，类似于自由剪切流动，传统的指数型和对数型水流阻力公式计算误差偏大。将自由剪切流理论类比到山区卵砾石河道，并考虑山区河流特殊流态、流场和剪切力的影响，引入雷诺数（Re）、弗劳德数（Fr）和摩阻流速利用水槽数据进一步修正了该类水流阻力公式。筛选位于意大利南部的亚平宁山脉140条山区河流野外数据对新公式进行验证，并检验对比了已发表的多个山区河流阻力公式。结果表明：修正后的水流阻力公式Nash-Sutcliffe效率指数最接近1、均方根误差最小、相对误差最小。自由剪切流动的类比是从湍流结构角度推导河道水流阻力，能更好地阐释特殊水流结构，进而提高计算精度。  相似文献   

腾冲热海地热田热储结构与岩浆热源的温度   总被引：16，自引：4，他引：12  

上官志冠 《岩石学报》2000,16(1):83-90

腾冲热海地区是一个由幔源岩浆侵入形成的地热田, 地热流体排放受深浅不同的三组活动断裂控制, 具多层地热储结构特征。气体、 同位素、 水化学地球化学温标显示, 深层热储的温度约为250±7℃、中、浅层地热储温度的变化范围分别为241～190℃和195～154℃。根据岩浆来源CO  相似文献