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191.
广西珊瑚钨锡矿床成矿年代学研究及其地质意义 总被引:2,自引:0,他引:2
珊瑚钨锡矿床位于富贺钟钨锡多金属成矿集中区的中部,是南岭钨锡多金属成矿带内典型的热液石英脉型矿床之一。本文采用白云母~(40)Ar-~(39)Ar法和石英流体包裹体Rb-Sr法,对矿床V32号含矿石英脉进行精细年代学研究,获得石英脉中白云母~(40)Ar-~(39)Ar坪年龄为101.7±0.7 Ma(MSWD=0.34),正等时线年龄为102.0±1.0 Ma(MSWD=1.17);石英流体包裹体Rb-Sr等时线年龄为106.4±3.5 Ma(MSWD=0.83)。它们在误差范围内一致,是华南地区燕山晚期成岩成矿高峰期的产物。同时通过石英包裹体H-O同位素组成的初步分析,认为成矿流体属于"再平衡岩浆水",主要来自岩浆,在矿床深部可能存在隐伏花岗岩体。该成果对研究区域成矿规律,指导类似地区的找矿勘查工作具有重要意义。 相似文献
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塔吾尔别克金矿床是西天山吐拉苏断陷盆地中一个重要的金矿床。矿体主要赋存于早石炭世二长斑岩及大哈拉军组第五岩性段安山岩、蚀变凝灰岩中,受断裂构造控制,矿床围岩蚀变作用普遍而强烈。矿石金属矿物主要为黄铁矿、自然金、赤铁矿和黄铜矿等,非金属矿物主要为石英、斜长石、方解石等。成矿过程大致划分为3个成矿阶段:1石英-黄铁矿阶段;2石英-硫化物脉阶段;3石英-碳酸盐阶段。石英及方解石中流体包裹体类型简单,主要为气液两相水包裹体和纯液相水包裹体。包裹体测试均一温度为100~196℃,流体盐度为0.0%~7.3%(质量分数,NaCl_(eq)),流体密度为0.9~1.0 g/cm~3,计算出成矿压力为5.2~81.9 MPa,对应成矿深度为0.5~7.4 km。塔吾尔别克金矿床成矿流体包裹体显示低温度、低盐度和较低密度的流体特征,表明成矿压力小和深度较浅。结合矿床地质特征、流体包裹体特征及前人研究成果,初步认为该矿床为浅成低温热液型金矿床。 相似文献
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通过在水基钻井液中添加纳米氧化物颗粒,来改善其润滑性能。选用了Al2O3、TiO2及SiO2三种纳米氧化物颗粒作为钻井液改性添加剂,利用极压润滑仪及销盘摩擦磨损实验仪研究了添加不同种类和浓度纳米颗粒氧化物对水基钻井液的润滑性能及减摩效果的影响。结果表明,所添加的3种球形纳米颗粒均有润滑减阻减摩的效果,其中SiO2颗粒的钻井液的润滑性能、滤失性能以及减摩效果都是最好的。当纳米SiO2颗粒加量为0.4%时,滤失量最小,润滑系数降低率达到15.6%,摩擦系数降低率为32.0%,磨痕轨迹平滑,减摩效果最为明显。当纳米颗粒浓度超过0.5%时,减摩效果降低,磨盘脱层磨损明显。 相似文献
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High speed liquid jet and shockwave can be produced when a bubble collapses near a rigid wall, which may cause severe damage to solid structures. A hybrid algorithm was adopted to simulate bubble motion and associated pressures near a wall combining Level Set-Modified Ghost Fluid-Discontinuous Galerkin (LS-MGF-DG) method and boundary element method (BEM). Numerical results were compared with experimental data to validate the presented algorithm. Jet formation was simulated by BEM and the induced pressure on the wall was calculated with auxiliary function. The pressure at the point on the wall where the jet points to reaches its peak value after the jet penetrates the bubble. Bubble collapse and rebounding were simulated by the LS-MGF-DG method. Shock-wave is induced when the bubble collapse toroidally to a minimum volume and the pressure at wall center reaches the maximum due to shockwave superposition. A third pressure peak is found associated with the bubble rebounds and bubble splitting. In the case studied, a higher pressure was found due to collapse shockwave than bubble jet and affects a larger area of the wall. In addition, the three pressure peaks due to jet impact, collapse impact as well as bubble rebounding and splitting decrease with the increase of the standoff distance. 相似文献
198.
In the present study, locomotion of a real longfin inshore squid (Doryteuthis pealeii) was numerically investigated. Geometry of a real squid was obtained using computed tomography (CT) images. In addition to a two-dimensional axisymmetric squid model, a modified squid model with no cavities around her head and an ellipse shaped model were generated with a fineness ratio (the ratio of body length to maximum body diameter) of 7.56. These numerical models were exposed to an acceleration with two different velocity programs. Added mass and basset forces on bodies were calculated during acceleration of the squid models starting from rest. Pressure and viscous drag forces were also calculated due to pressure variation along the squid models and friction on the surface of the models. The effect of a nozzle diameter on jet velocities and propulsive efficiency at all bodies were evaluated when time dependent velocity profiles (from 0 to 10 m/s in 0.5 and 1 s time durations) were set for the inlet of computational domain. The modified squid model required least thrust force during acceleration phase of time dependent velocity profile compared to the other models while the 0.02 m nozzle diameter provided largest propulsive efficiency for all models. 相似文献
199.
Hydrothermal Fluid Sources of the Fengjia Barite–fluorite Deposit in Southeast Sichuan,China: Evidence from Fluid Inclusions and Hydrogen and Oxygen Isotopes
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The Fengjia barite–fluorite deposit in southeast Sichuan is a stratabound ore deposit which occurs mainly in Lower Ordovician carbonate rocks. Here we present results from fluid inclusion and oxygen and hydrogen isotope studies to determine the nature and origin of the hydrothermal fluids that generated the deposit. The temperature of the ore‐forming fluid shows a range of 86 to 302 °C. Our detailed microthermometric data show that the temperature during mineralization of the fluorite and barite in the early ore‐forming stage was higher than that during the formation of the calcite in the late ore‐forming stage. The salinity varied substantially from 0.18% to 21.19% NaCl eqv., whereas the density was around 1.00 g/cm3. The fluid composition was mainly H2O (>91.33%), followed by CO2, CH4 and traces of C2H6, CO, Ar, and H2S. The dominant cation was Na+ and the dominant anion Cl‐, followed by Ca2+, SO42‐, K+, and Mg2+, indicating a mid–low‐temperature, mid‐low‐salinity, low‐density NaCl–H2O system. Our results demonstrate that the temperature decreased during the ore‐forming process and the fluid system changed from a closed reducing environment to an open oxidizing environment. The hydrogen and oxygen isotope data demonstrate that the hydrothermal fluids in the study area had multiple sources, primarily formation water, as well as meteoric water and metamorphic water. Combined with the geological setting and mineralization features we infer that the stratabound barite–fluorite deposits originated from mid–low‐temperature hydrothermal fluids and formed vein filling in the fault zone. 相似文献
200.
Xiaowei Tang Xiwen Zhang Qi Shao Zhenqing Li 《Marine Georesources & Geotechnology》2016,34(6):594-601
In the last 20 years, the bucket foundation has been developed as a new type of offshore platform structure. Because of its short period of application to engineering practices, the theoretical decision on the rotation center and horizontal bearing capacity of the bucket foundation has yet to be agreed. A limit analysis method is used to determine the updated rotation center position and horizontal bearing capacity to evaluate the failure mechanisms of the bucket foundations. The results are compared with numerical simulation and experiments, and also with other theoretical methods. The proposed method can satisfactorily consider the engineering conditions and the result is accurate in determining the rotation center and horizontal bearing capacity. 相似文献