周宁芹溪银铅锌矿床成矿作用与找矿方向

周宁芹溪银铅锌矿床位于寿山早白垩世火山喷发盆地北东缘,矿体受火山构造、区域北西—北北西向断裂构造控制,贮存于南园组第三段流纹质晶玻屑凝灰岩中,呈脉状、透镜状产出,属浅成中低温火山-次火山热液银铅锌矿床。     

青藏高原东北缘地震断层的研究

青藏高原东北缘新构造运动强烈,地震活动频繁。调查资料表明,伴随每次大地震的发生,都将产生规模不等的地震断层。本文研究了该区地震断层的分布规律、类型以及与先存断裂的关系等,同时对研究区不同地段的地壳稳定性进行了初步评价。      

水化学和钙华碳氧稳定同位素在古环境重建中的应用--以贵州荔波小七孔景区响水河为例

文章报道了响水河河水的现场监测结果,得到响水河河水的Ca²+和HCO^-₃非常低,这明显与河床中大规模钙华的存在和景区内发育的茂密植被不匹配;并仔细观察发现,钙华表面有被侵蚀的痕迹,如溶蚀槽和溶蚀坑等,这说明目前所见钙华可能是过去环境条件下的产物。根据钙华碳氧稳定同位素组成特征的分析得出:近4000年来,该地区总的气候环境变化趋势是4000～3400aB.P.为相对温暖湿润期,植被生长好,为良性生态期;3400～2000aB.P.前期仍比较温暖但干燥,后期到2000aB.P.左右变得比较凉爽,从这一冷期到大致900aB.P.前后,气候有些波动,但幅度较小,夹有冷暖干湿的交替;而900aB.P.至今,钙华碳氧稳定同位素值的急剧增加,反映出气候的冷干和源区人类活动加剧造成的水土流失增加,岩溶石漠化加重,生态朝恶化方向发展     

福建漳浦山门石英砂矿地质特征及成因探讨

山门石英砂矿主要贮存于长乐组海积层中,矿体近水平层状产出,主要受物质来源、地貌和水动力与新构造运动等条件控制,矿床成因类型属滨海堆积。区内石英砂资源量大且质优,成矿地质条件好。     

Electrical conductivity of alkali feldspar solid solutions at high temperatures and high pressures

The electrical conductivities of alkali feldspar solid solutions ranging in chemical composition from albite (NaAlSi₃O₈) to K-feldspar (KAlSi₃O₈) were measured at 1.0 GPa and temperatures of 873–1,173 K in a multi-anvil apparatus. The complex impedance was determined by the AC impedance spectroscopy technique in the frequency range of 0.1–10⁶ Hz. Our experimental results revealed that the electrical conductivities of alkali feldspar solid solutions increase with increasing temperature, and the linear relationship between electrical conductivity and temperature fits the Arrhenius formula. The electrical conductivities of solid solutions increase with the increasing Na content at constant temperature. At 1.0 GPa, the activation enthalpy of solid solution series shows strong dependency on the composition, and there is an abrupt increase from the composition of Or₄₀Ab₆₀ to Or₆₀Ab₄₀, where it reaches a value of 0.96 eV. According to these results in this study, it is proposed that the dominant conduction mechanism in alkali feldspar solid solutions under high temperature and high pressure is ionic conduction. Furthermore, since the activation enthalpy is less than 1.0 eV for the alkali feldspar solid solutions, it is suggested to be a model where Na⁺ and K⁺ transport involves an interstitial mechanism for electrical conduction. The change of main charge carriers can be responsible for the abrupt increase in the activation energy for Or₆₀Ab₄₀. All electrical conductivity data were fitted by a general formula in order to show the dependence of activation enthalpy and pre-exponential factor on chemical composition. Combining our experimental results with the effective medium theory, we theoretically calculated the electrical conductivity of alkali feldspar granite, alkali feldspar quartz syenite, and alkali feldspar syenite with different mineral content and variable chemical composition of alkali feldspar at high temperatures at 1.0 GPa, and the calculated results are almost in agreement with previous experimental studies on silicate rocks.     

华北地台晚古生代海侵模式雏议

本对华北地台的山西太原西山上石炭统太原组的7、8和11号煤层及其顶板灰岩的地球化学特征、煤核和生物化石进行了系统分析，发现煤层形成过程中有海水的影响，煤层上覆石灰岩形成过程中亦有淡水参与，说明煤层及其顶板灰岩在相序上是连续的，其海侵模式并不是突发型海便。而为渐进型海侵。本还应用层序地层学原理论述了海平面变化与聚煤作用的关系。     

陕西北秦岭地区构造作用与成矿初探

陕西北秦岭地区具有多旋回构造发展史及多旋四成矿作用。主要表现:断裂构造作用的多期性,板块多次俯冲碰撞,构造带多次由北向南迁移以及多期次岩浆活动和变质作用等方面。其结果使得该区显示出由北向南的构造发展规律,并形成了最终的构造格局。根据该区多旋回的构造发展历史,可将该区铀及其有关矿产分为五个矿化旋回期:太古代,元古代、早古生代、晚古-中生代和新生代。其中早古生代、晚古-中生代和新生代,是区内三个主要矿化旋回期。深大断裂带系统在成岩成矿中占有相当重要的地位,它们不但控制了区内内生矿化的形成,而且是控制变质怍用与矿化的重要因素。断裂作用破坏了地壳岩石的完整性,使处于封闭状态的铀及其它成矿元素得以活化转移,从而形成了矿化作用的有利条件。燕山-喜山期构造和岩浆活化作用,对原有地质构造和矿化进行了强烈的改造。形成了新的矿化排列组合及新类型矿化。铀矿化则以淋积型为主。该区有利的找矿方向是:地台边缘冒地槽区,深大断裂带通过富铀建造的地区,北东向隆起一沉降过渡区。     

GIS-based geo-environmental evaluation for urban land-use planning: a case study

A geo-environmental evaluation for urban land-use planning often requires a large amount of spatial information. Geographic information systems (GIS) are capable of managing large amounts of spatially related information, providing the ability to integrate multiple layers of information and to derive additional information. A GIS-aid to the geo-environmental evaluation for urban land-use planning is illustrated for the urban area of Lanzhou City and its vicinity in Northwest China. This evaluation incorporates topography, surficial and bedrock geology, groundwater conditions, and historic geologic hazards. Urban land-use is categorized according to the types of land-use and projects planned, such as high-rise building, multi-storey building, low-rise building, waste disposal, and natural conservation. Multi-criteria analysis is performed to evaluate development suitability of the geo-environment for each category, according to appropriately measured and weighted factors. A suitability map for each category is developed using an algorithm that combines factors in weighted linear combinations. It is demonstrated that the GIS methodology has high functionality for geo-environmental assessment.     

http://www.sciencedirect.com/science/article/pii/S1674987111000478

Convective heat transfer associated with the circulation of pore-fluid in porous rocks and fractures within the upper crust of the Earth is substantial when the temperature gradient is sufficiently high.In order to understand the process of Sn-polymetallic mineralization in the Dachang ore district of Guangxi,a finite element method has been used in this study to simulate both pore-fluid flow and heat transfer in this district.On the basis of related geological,tectonic and geophysical constraints,a computational model was established.It enables a computational simulation and sensitivity analysis to be carried out for investigating ore-forming pore-fluid flow and other key factors that may affect hydrothermal ore genesis in the district.The related simulation results have indicated that:(1) permeable fault zones in the Dachang ore district can serve as preferential pathways for pore-fluid flow on a regional-scale;and(2) the pore-fluid flow can affect the salinity distribution.This latter factor is part of the reason why Sn-polymetallic mineralization has taken place in this district.     

广西钦州地区那丽花岗岩LA-ICP-MS锆石U-Pb定年及其地质意义

位于广西南部钦州地区的那丽岩体是华南地区(除海南岛外)报道的、具精确同位素年龄的海西期花岗岩岩体,LA-ICP-MS锆石U-Pb定年结果显示其形成时代为262Ma。二叠纪时期,羌塘-中缅Sibumasu地块与印支地块碰撞拼合,导致华南陆块俯冲于印支陆块之下,那丽花岗岩可能形成于这种俯冲作用的较晚阶段——弧后伸展环境。