兰坪金顶蜂子山铅锌矿床的构造控矿:来自三维空间数据分析的证据

滇西金顶超大型铅锌矿床的热液成矿和构造控矿特点突出,对其主要容矿岩石和断层耦合控矿机制仍不清楚.利用三维空间数据分析方法,对代表性的蜂子山铅锌矿床开展了矿化结构及其空间展布特征的综合研究.结果 表明:Pb和Zn矿化中心呈现出东西向分带及差异性分段富集的特点,空间上并与黄铁矿、天青石(—重晶石)和石膏矿体共置;成矿流体的运聚受近SN向逆冲断层和近EW向走滑断层的共同控制,为其提供通道和沉淀空间;而金顶群(N1j)的湖相氧化性含矿卤水在两组方向断层的联合驱动下,在三合洞组上段(T3S3)地层中与其赋存的还原性流体幕式混合成矿,是该矿床发育的重要机制.尤其是,近SN向逆冲断层和近EW向走滑断层联合控矿特征的发现,为深入理解金顶超大型铅锌矿床成矿作用及指导找矿勘查提供了新的依据.     

A variable source area for groundwater evapotranspiration: impacts on modeling stream flow

Evapotranspiration (ET) plays a crucial role in catchment water budgets, typically accounting for more than 50% of annual precipitation falling within temperate deciduous forests. Groundwater ET is a portion of total ET that occurs where plant roots extend to the capillary fringe above the phreatic surface or induce upward movement of water from the water table by hydraulic redistribution. Groundwater ET is spatially restricted to riparian zones or other areas where the groundwater is accessible to plants. Due to the difficulty in measuring groundwater ET, it is rarely incorporated explicitly into hydrological models. In this study, we calibrated Topographic Model (TOPMODEL) using a 14‐year hydrograph record and added a groundwater ET pathway to derive a new model, Groundwater Evapotranspiration TOPMODEL (GETTOP). We inspected groundwater elevations and stream flow hydrographs for evidence of groundwater ET, examined the relationship between groundwater ET and topography, and delineated the area where groundwater ET is likely to take place. The total groundwater ET flux was estimated using a hydrological model. Groundwater ET was larger where the topography was flat and the groundwater table was shallow, occurring within about 10% of the area in a headwater catchment and accounting for 6 to 18% of total annual ET. The addition of groundwater ET to GETTOP improved the simulation of stream discharge and more closely balanced the watershed water budget. Copyright © 2013 John Wiley & Sons, Ltd.     

The Khao Que-Tam Tao gabbro-granite massif, Northern Vietnam: A petrological indicator of the Emeishan plume

New data obtained on the Khao Que-Tam Tao gabbro-granite pluton (Northern Vietnam) are discussed. It was established that this pluton was formed at the Permian-Triassic boundary (250.5 ± 3.2 Ma, ⁴⁰Ar/³⁹Ar isotopic age). Morphologically, it represents a hypabyssal fracture intrusion. The first stage was marked by the intrusion of the picrobasaltic melt, the differentiation of which resulted in the formation of the layered peridotite-gabbro series and the quartz-bearing monzodiorites and granophyres in its endocontact at the final stage. At the second stage, the Khao Que peridotite-gabbro massif was broken in its central part by a fault, along which the Tam Tao granodiorite-granite massif was localized. Numerical simulation using the COMAGMAT program for the basic system and geochemical estimates for the granite system allow the statement that the mafic and granitic melts evolved independently, and their final products were quartz-bearing monzodiorite and granophyre, on the one hand, and aplites and pegmatites, on the other hand. The compositional correlation of the Permian-Triassic magmatic associations in Northern Vietnam (the Nui Chua gabbro pluton and the Khao Que-Tam Tao gabbro-granite and Pia Bioc granite plutons) and in Southeast China (flood basalts) allows these complexes to be regarded as a part of a single large igneous province produced by the Emeishan plume activity.     

Investigation of the accelerated carbonation of a MgO-based binder used to treat contaminated sediment

A MgO-based binder developed to simultaneously solidify/stabilize contaminated sediment and store CO₂ has been described previously. The objectives of the study presented here were to investigate the kinetics of the carbonation reactions of the binder and the extent to which carbonation occurred and to identify the optimal conditions for using the binder. The carbonation reaction was clearly faster and the degree of carbonation higher at CO₂ concentrations of 50 and 100% than in the ambient atmosphere (which contains 0.04% CO₂). A modified unreactive core model adequately described the kinetics. The rate constants were 0.0217–0.319 h^?1 and were proportional to the degree of carbonation. A high degree of carbonation, 93.8%, was achieved at a CO₂ concentration of 100%. The water to sediment ratio strongly affected carbonation, the optimal ratio being around 0.7. The relative humidity did not strongly affect the carbonation performance. The carbonation products were magnesite (MgCO₃) and nesquehonite (MgCO₃·3H₂O). X-ray diffraction analysis showed that brucite (Mg(OH)₂) was not present, suggesting that brucite was very quickly transformed into magnesium carbonates, the presence of which was confirmed by thermal gravimetric analysis. The results indicated that, in 7 d, 1 kg of binder could sequester up to 0.507 kg of CO₂ in a 100% CO₂ atmosphere. The results indicate that the MgO-based binder has great potential to be used to sequester CO₂ under accelerated carbonation conditions.     

High Plains groundwater isotopic composition in northeastern New Mexico (USA): relationship to recharge and hydrogeologic setting

Hydrogeology Journal - In the High Plains (HP) region of northeastern New Mexico (NE NM), USA, underlying bedrock aquifers are utilized where the High Plains Aquifer is thin, absent, or...     

GPS multipath mitigation: a nonlinear regression approach

Under the assumption that the surrounding environment remains unchanged, multipath contamination of GPS measurements can be formulated as a function of the sidereal repeatable geometry of the satellite with respect to the fixed receiver. Hence, multipath error estimation amounts to a regression problem. We present a method for estimating code multipath error of GPS ground fixed stations. By formulating the multipath estimation as a regression problem, we construct a nonlinear continuous model for estimating multipath error based on well-known sparse kernel regression, for example, support vector regression. We will empirically show that the proposed method achieves state-of-the-art performance on code multipath mitigation with 79 % reduction on average in terms of standard deviation of multipath error. Furthermore, by simulation, we will also show that the method is robust to other coexisting signals of phenomena, such as seismic signals.     

A fractal model for streaming potential coefficient in porous media

Streaming potential is the result of coupling between a fluid flow and an electric current in porous rocks. The modified Helmholtz–Smoluchowski equation derived for capillary tubes is mostly used to determine the streaming potential coefficient of porous media. However, to the best of our knowledge, the fractal geometry theory is not yet applied to analyse the streaming potential in porous media. In this article, a fractal model for the streaming potential coefficient in porous media is developed based on the fractal theory of porous media and on the streaming potential in a capillary. The proposed model is expressed in terms of the zeta potential at the solid?liquid interface, the minimum and maximum pore/capillary radii, the fractal dimension, and the porosity of porous media. The model is also examined by using another capillary size distribution available in published articles. The results obtained from the model using two different capillary size distributions are in good agreement with each other. The model predictions are then compared with experimental data in the literature and those based on the modified Helmholtz–Smoluchowski equation. It is shown that the predictions from the proposed fractal model are in good agreement with experimental data. In addition, the proposed model is able to reproduce the same result as the Helmholtz–Smoluchowski equation, particularly for high fluid conductivity or large grain diameters. Other factors influencing the streaming potential coefficient in porous media are also analysed.     

Natural occurrence of higher thiadiamondoids and diamondoidthiols in a deep petroleum reservoir in the Mobile Bay gas field

A series of higher thiadiamondoids and diamondoidthiols, including thiatetramantanes, tetramantanethiols, thiapentamantanes, pentamantanethiols, thiahexamantanes, hexamantanethiols and thiacylcohexamantane, was discovered in a gas condensate produced from a very deep (6274 m, 20,585 ft) petroleum reservoir in the Bon Secour Bay in the Mobile Bay gas field, located offshore Alabama in the northern Gulf of Mexico, USA. This appears to be the first reported natural occurrence of these compounds. Several isomers of higher thiadiamondoids and diamondoidthiols were identified using full scan gas chromatography-mass spectrometry (GC-MS) coupled with GC-sulfur chemiluminescence detection (GC-SCD) and GC × GC-time of flight mass spectrometry (GC × GC-TOFMS). These higher thiadiamondoids and diamondoidthiols are associated with abundant lower homologs including thiaadamantanes, thiadiamantanes, thiatriamantanes and their thiol groups. The origin of these compounds in petroleum has not been reported. It is speculated that similar to lower thiadiamondoids and diamondoidthiols, higher ones are possibly formed from the sulfurization of their precursor diamondoids during TSR, a conclusion supported by the occurrence of open-cage higher diamondoidthiols and sulfur isotopic data of higher thiadiamondoids and diamondoidthiols isolated from the Mobile Bay condensate. The presence of higher thiadiamondoids and diamondoidthiols is indicative of the occurrence of TSR and can be used to predict sour gas production.