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21.
We present analyses of plume rise into a linearly stratified environment, either with or without a uniform horizontal flow. In the case of a still ambient, we collate results on plume spreading height and volume flux, enabling the speed of the spreading intrusion in the buoyancy-inertia regime to be expressed in terms of the fundamental parameters of plume buoyancy flux and ambient buoyancy frequency. A theoretical expression for the final volume flux emanating from the plume-rise region, in terms of maximum rise height, is also derived. Hence it is shown that the ratio of the intrusion radius to the maximum rise height is a simple function of ambient buoyancy frequency and time. In the case of a wind, we analyse the theoretical model for a rising plume to obtain predictions for the downwind volume flux, and subsequent lateral spread, in the limits of strong and weak wind. We identify a regime of very weak wind, which may be modelled as a passive advection of plume flow in the still case as a first approximation. Numerical solutions of a general model are presented which show that it predicts a peak in entrainment, and hence volume-flux growth, in the case of intermediate wind strength. We verify the crosswind model predictions of lateral spread, upwind penetration and entrainment by comparison with large-eddy simulations. 相似文献
22.
The Kapalagulu layered ultramafic and mafic intrusion is emplaced between the Paleoproterozoic Ubendian basement and overlying Neoproterozoic Itiaso Group metasedimentary rocks, located near the western shore of Lake Tanganyika. High-grade platinum group element (PGE) mineralization (1–6 g/t Pt + Pd + Au) is associated with chromitite and sulfide-bearing harzburgite within the southeastern extension of the intrusion, known as the Lubalisi Zone, which is covered by a layer of nickel-rich (0.2–2%Ni) laterite regolith that contains linear areas of PGE mineralization.In the Lubalisi Zone, the mineralization may be divided into several significant geometallurgical domains: (a) high-grade PGE mineralization (1–6 g/t Pt + Pd + Au) associated with stratiform PGE reefs and chromitite seams within a harzburgite unit; (b) high-grade PGE mineralization (up to 12 g/t Pt + Pd + Au) associated with small bodies and veins of nickel massive sulfide within harzburgite below PGE-bearing reefs and chromitite seams; (c) low-grade PGE mineralization (0.1–0.5 g/t Pt + Pd + Au) associated with a sulfide-mineralized harzburgite unit above the PGE-bearing reefs; (d) laterite style residual PGE mineralization (0.2–4 g/t Pt + Pd + Au) associated with chromite concentrations in the saprolite and overlying red clay horizons of the laterite regolith; and (e) supergene Ni associated with the saprock and overlying saprolite clay.Mineralogical study of three samples from the PGE reef consisting of high grade PGE chromitite and harzburgite indicate that this mineralization will give a good metallurgical response to conventional grinding and floatation due to the relatively coarse-grained nature of the PGM (P80 from ∼37 to 52 µm), association with base metal sulfides, and unaltered gangue minerals (Wilhelmij and Cabri, 2016). In contrast, mineralogical and metallurgical study of the Ni and PGE mineralized laterite indicate that it cannot be processed using conventional mineral processing techniques but that a hydrometallurgical route should be used to recover the base and precious metals. Because any process is very much deposit-controlled, significant metallurgical and geometallurgical testing of mineralized samples, as well as pilot plant testing, will be required to arrive at feasibility studies. 相似文献
23.
云南富宁地区铜镍矿成矿地质条件分析 总被引:1,自引:0,他引:1
铜镍是富宁地区主要矿种。成矿母岩为"安定型"基性岩。岩体具有明显的分异现象,自边缘至中心可分成致密状辉绿岩相、中细粒橄榄辉长苏长岩相、中粒辉长苏长岩相、中粒闪长岩相四个相带。铜镍矿主要产于中细粒橄榄辉长苏长岩相中,其次产于中粒辉长苏长岩相中。对富宁地区铜镍矿成矿地质条件进行分析。 相似文献
24.
全球的世界地质公园活动是于1996年在房山周口店开始的。房山世界地质公园地跨北京市房山区和河北省涞水县、涞源县,地理坐标:东经114°36ˊ48"~116°08ˊ16",北纬39°09ˊ57"~39°43ˊ08"。公园东西长130.80km,南北宽75.09km,总面积953.95km2。其中划分为8个园区:周口店、石花洞、十渡、百花山-百草畔、上方山-云居寺、圣莲山、野三坡和白石山园区。房山区为3水合围,东面为永定河,北面为大石河,南面为拒马河。房山是以岩溶景观为特色的世界地质公园。其北面的大石河流域自上而下,依次发育鸡毛洞、银狐洞、石花洞和孔水洞,由一条地下暗河将其连为一个洞系。南面的拒马河流域,地层为产状平缓的中元古代雾迷山组硅质条带白云岩,形成新近纪石林与第四纪岩溶陡壁的组合地貌形态——房山地貌。 相似文献
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The differentiated Mesozoic alkali dolerite Prospect Intrusion contains a wide range of secondary minerals, including carbonates (primarily calcite), laumontite, prehnite and heulandite, whose stability relationships imply a formation temperature of <200°C. The δ18O data for carbonates define a higher temperature (160 – 195°C) suite, and a lower temperature (51 – 73°C) suite. The δ13C, δ18O and 87Sr/86Sr isotope systematics for these carbonates suggest derivation of the higher temperature group from magmatic fluids, whereas the other group had a major meteoric component that probably originated from porewater in the country rock. Source fluids for prehnite were meteoric rather than magmatic in origin based on their δD and δ18O ratios. Early in the intrusion's emplacement, CO2-rich hydrothermal fluids formed a carbonate rind sealing the upper part of the hydrothermal system and produced the higher temperature carbonates (calcite) and laumontite. Later, cooler fluids with a meteoric component infiltrated vesicles and fractures, depositing the lower temperature carbonates (calcite, aragonite), heulandite and prehnite. 相似文献
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本文阐述了菲律宾大马尼拉地区的地貌、气候、水文、地质等背景情况;介绍区内的地下水质水介质类型及含水层发育情况、富水性和导水性、地下水水力性质、水化学特征和补排条件以及地下水的开采情况和需求量,从而分析了大马尼拉地区海水的机理。 相似文献
30.
Eyjafjallajökull volcano, located in southern Iceland, is characterized by its quiet nature. Only about a handful of earthquakes associated with the volcanic system had been detected prior to the 1990s. Earthquake swarms did, however, occur in 1994 and 1999. Here we investigate the spatio-temporal evolution of a magmatic intrusion associated with the 1999 earthquake swarm via analysis of produced surface deformation. A series of interferometric synthetic aperture radar (InSAR) images, spanning various periods of the intrusion, show that in 1999 surface deformation occurred mainly on the southern flanks of the volcano. The deformation amounts to more than 20 cm of range change. Inverse modeling resolves the deformation source to be a sill intrusion at 6.3 km depth. Sill opening was up to 1 m and the total intruded volume amounts to ~0.03 km3. The InSAR data display a migration of the center of deformation through time, enabling us to create time-dependant sill-opening models. Furthermore, we investigate the spatio-temporal distribution of earthquakes and find that the distribution supports the InSAR derived model and additionally provides indications for a possible site of a feeder channel. Magmatic flow-rate estimates indicate an initial intrusion rate of 4–6 m3/s, declining over a few weeks. 相似文献