Gold production history of the United States

Gold has played an important role in the settlement and economics of the United States. Commercial production from 24 states totaled more than 420 million troy ounces (13,000 metric tons) from 1804 through 1995. There were, no doubt, early undocumented discoveries by Native Americans, but the first records are those from the mid-1600's in the east and from the 1770's in the west. Commercial production began in 1804 in North Carolina and spread among several Appalachian states in the 1820's and 1830's as placer deposits were discovered and exploited. After peaking in the 1830's and 1840's, Appalachian production began to decline as deposits were worked out and as miners moved westward in response to the news of the discoveries in California in 1848. Appalachian production virtually ceased with the Civil War while production from California and adjacent states remained at several millions of ounces per year. As the California Gold Rush waned, new discoveries brought the Rocky Mountain states, South Dakota, and Alaska into prominence. Local, state and total production responded to time of discovery, extent of placers, labor availability, technology, government mandates and, of course, the price of gold. By 1900, the major gold rushes had occurred and most of the major producing districts were defined; however, the fixed price of gold (since 1837) provided a decreasingly attractive incentive for more exploration and exploitation. The rise in the price of gold, during the Depression provided a powerful incentive to increase gold production, but one that was cut short by War Production Board Order L-208 which closed the gold mines in 1942. In the post-war period, the fixed price, combined with the prohibition of American gold ownership, again proved to be a disincentive and gold production dropped. The era of free gold price that began in 1968, followed by the permission for Americans to again own gold, brought new interest in gold with prices rising briefly in 1980 to US$850 per ounce and remaining above US$350 per ounce through 1995. This higher price, combined with the technology for bulk mining and processing of low grade ores, provided incentive for new exploration and exploitation. Consequently, gold production soared above 10 million ounces per year in the early 1990's with 65% coming from Nevada. There has been a general decrease in the grade of gold ores since the early 1900's and significant changes in the methods of recovery. Despite the decreasing grade, the reserves of recoverable gold have more than doubled since the early 1970's.     

当阳地区地震地质特征浅析

本区构造发展存在三个不同阶段，印支期为初始褶皱阶段；燕山期为逆冲推覆定型阶段；喜马拉雅期为改造与破坏阶段。其地质结构明显具有双重构造，构造反转和推覆滑税三大特征。区内地震反射特征与岩性组合有一定对应关系，本文首次尝试利用地震反射信息特征对沉积环境进行分析。     

香格里拉陆家村银金多金属矿矿化特征及找矿标志

研究区浅部以断裂破碎带控制的热液脉型Cu、Au、Pb、Ag矿床为主,深部形成斑岩型Cu、Mo矿床。矿体受地层及断裂构造双重控制。硅化、黄(褐)铁矿化与矿化关系最为密切,是主要的围岩蚀变,亦为主要的找矿标志。     

贵州威宁长坪子铅锌矿区地质特征及控矿因素浅析

贵州威宁长坪子铅锌矿区位于北西向的江子山背斜铅锌成矿带中段,矿床的形成和分布受江子山背斜构造的控制。而矿体受主干构造及其压性纵断层的下盘或层间破碎带控制,或北西与北东向断裂共同控制;矿体主要呈似层状、透镜状;矿体的产出主要受地层、构造条件共同控制。系统地研究了区内的导矿、配矿、容矿构造特征,提出了地质构造是控制矿床形成和分布的主导因素,以便为区内地质找矿理清思路,指明方向。     

Surface roughness and geological mapping at subhectometer scale from the High Resolution Stereo Camera onboard Mars Express

The quantitative measurement of surface roughness of planetary surfaces at all scales provides insights into geological processes. A characterization of roughness variations at the scale of a few tens of meters is proposed that complements the analysis of local topographic data of the martian surface at kilometer scale, as achieved from the Mars Orbiter Laser Altimeter (MOLA) data, and at the subcentimeter scale using photometric properties derived from multi-angular observations. Relying on a Gabor filtering process, an algorithm developed in the context of image classification for the purpose of texture analysis has been adapted to handle data from the High Resolution Stereo Camera (HRSC). The derivation of roughness within a wavelength range of tens of meters, combined with analyses at even longer wavelengths, gives an original view of the martian surface. The potential of this approach is evaluated for different examples for which the geological processes are identified and the geological units are mapped and characterized in terms of roughness.     

柴达木盐湖化工科学研究联合基金实施概况

对2014~2017年国家自然科学基金委员会—青海省人民政府柴达木盐湖化工科学研究联合基金申报与资助项目进行分析,重点研究联合基金实施概况,指出实施成效及存在的问题,并提出解决相关问题的发展建议,通过对联合基金资助和实施结果进行探讨,不断总结经验,优化模式,更好地为柴达木盐湖化工科学研究联合基金创新发展提供制度保障和参考依据。     

地质领域机器学习、深度学习及实现语言

地质大数据正在以指数形式增长。只有发展智能数据处理方法才有可能追上大数据的超常增长。机器学习是人工智能的核心,是使计算机具有智能的根本途径。机器学习已成为地质大数据研究的前沿热点,它将让地质大数据插上翅膀,并因此改变地质。机器学习是一个源于数据的模型的训练过程,最终给出一个面向某种性能度量的决策。深度学习是机器学习研究中的一个重要子类,它通过构建具有很多隐层的机器学习模型和海量的训练数据,来学习更有用的特征,从而最终提升分类或预测的准确性。卷积神经网络算法是最为常用的一种深度学习算法之一,它广泛用于图像识别和语音分析等。Python语言在科学领域的地位占据着越来越重要。其下的Scikit-Learn是一个机器学习相关的库,提供有数据预处理、分类、回归、聚类、预测、模型分析等算法。Keras是一个基于Theano/Tensorflow的深度学习库,可以应用来搭建简洁的人工神经网络。     

RELIGIOUS AFFILIATION AND ALCOHOL CONSUMPTION IN THE UNITED STATES*

ABSTRACT. Levels of alcohol consumption are a major public health issue. This study aims to gain a better understanding of how geographical patterns of religious affiliation in the United States relate to geographical patterns of alcohol consumption. We explored state‐level correlations between alcohol consumption and religious adherence. Although we found no statistically significant correlation between overall religious adherence rates and current or binge drinking rates, states with higher adherence rates were significantly more likely to have high proportions of binge drinking among current drinkers. Yet, regionally, we found a strong inverse correlation in the Southeast and a strong positive correlation in the Midwest and Northeast between adherence rates and current and binge drinking rates. These geographical differences were largely explained after stratifying by major religious denominational groupings. States with high Catholic adherence rates tended to have higher drinking rates, whereas states with high Evangelical Protestant adherence rates tended to have lower drinking rates. These findings suggest that the relationship between religion and alcohol may be denomination‐specific and challenge the lay perception that religious adherence per se is associated with less alcohol consumption and less excessive drinking among those who drink.     

甘肃省地质勘查基金项目勘查成果综述

甘肃省地质勘查基金设立于2009年,至今共设置勘查项目259个,总经费34.2亿元。勘查项目主要部署在甘肃北山、阿尔金—祁连山、西秦岭及陇东地区等主要成矿区带,勘查矿种主要有能源矿产(煤炭、地热、页岩气、铀)、金属矿产(铁、锰、钒、钛、铜铅锌、钨钼、金银、铌钽)、非金属矿产(萤石、石膏、晶质石墨、硅灰石、水泥灰岩、重晶石、花岗岩饰面石材)。其主要目的是增强矿产资源对甘肃经济社会可持续发展的保障能力,提高政府对矿产资源的调控水平,规范矿业权市场。通过省地矿局、省有色地勘局、省煤田地质局、省核工业地质局等单位的组织实施,煤炭、页岩气、铁、铜、金、晶质石墨等矿种勘查取得了较大的突破。其中,以大会战的方式,相继开展了环县、正宁县南部、宁县中南部等大型煤田勘查,创造了地质找矿的"陇东模式",累计查明煤炭资源量204.6亿吨。为陇东能源基地建设奠定了资源基础。在陇东、武威、敦煌盆地开展了页岩气资源调查评价工作,其中敦煌盆地页岩气调查取得突破性进展。在镜铁山外围卡瓦一带开展的铁矿勘查累计提交铁矿石资源量达5.3亿吨,是甘肃又一处在全国具有宏观影响的铁矿勘查重大成果。白银铜矿深部勘查是老矿山深部探边摸底找矿突破的典型事例,新增铜铅锌金属量51.93万吨,对延长白银铜矿山寿命具有重要意义。金矿勘查也取得了重要进展,累计探求金金属资源量43.07 t。晶质石墨作为新兴战略性矿产,连续找矿突破,初步探求资源量达490万吨。上述勘查成果显示,在矿业市场持续低迷的环境下,省地勘基金对全省地质找矿和矿业开发起到了显著的促进作用,对全省经济社会发展具有重要意义。     

浅谈地质预报与监测在某水电站边坡塌方中发挥的作用

该洞口进口段及边坡有多条岩脉在此交汇,工程地质条件较差,在开挖过程中由于支护不及时,发生了冒顶,但在冒顶前,多点位移计等监测仪器监测到了不同程度的突变,地质预报也根据开挖情况及时进行预了围岩类别的预测及安全提示,对指导施工及人员安全发挥了预测及提醒作用。