Improved Preproduction Conceptual-Numerical Model of the Roosevelt Geothermal Field using Geological,Geochemical and Structural Information

The Roosevelt Hot Springs Known Geothermal Resource Area (KGRA) is a Basin and Range-type geothermal resource, which is located in southwestern Utah. The integrated multicomponent geothermometry (IMG) approach is used to estimate the reservoir temperature at the Roosevelt Hot Springs KGRA. Geothermometric modeling results indicate the deep reservoir temperature is approximately 284.6°C. A conceptual model of the Roosevelt Hot Spring KGRA is provided through integrating the various pieces of exploration information, including the geological data, geothermometric results, temperature well log and field evidence. A two-dimensional cross-sectional model was thus built to quantitatively investigate the coupled thermal-hydraulic processes in the Roosevelt geothermal field. By matching the preproduction temperature log data of deep wells, parameters controlling flow and heat transport are identified. The method and model presented here may be useful for other geothermal fields with similar conditions.     

The evolution of the Cappadocia Geothermal Province,Anatolia (Turkey): geochemical and geochronological evidence

Cappadocia Geothermal Province (CGP), central Turkey, consists of nine individual geothermal regions controlled by active regional fault systems. This paper examines the age dating of alteration minerals and the geochemistry (trace elements and isotopes) of the alteration minerals and geothermal waters, to assess the evolution of CGP in relation to regional tectonics. Ar–Ar age data of jarosite and alunite show that the host rocks were exposed to oxidizing conditions near the Earth’s surface at about 5.30 Ma. Based on the δ¹⁸O–δD relationhip, water samples had a high altitude meteoric origin. The δ³⁴S values of jarosite and alunite indicate that water samples from the southern part of the study area reached the surface after circulation through volcanic rocks, while northern samples had traveled to the surface after interacting with evaporates at greater depths. REY (rare earth elements and yttrium) diagrams of alteration minerals (especially illite, jarosite and alunite) from rock samples, taken from the same locations as the water samples, display a similar REY pattern to water samples. This suggests that thermal fluids, which reached the surface along a fault zone and caused the mineral alteration in the past, had similar chemical composition to the current geothermal water. The geothermal conceptual model, which defines a volcanically heated reservoir and cap rocks, suggests there are no structural drawbacks to the use of the CGP geothermal system as a resource. However, fluid is insufficient to drive the geothermal system as a result of scanty supply of meteoric water due to evaporation significantly exceeding rainfall.     

Natural attenuation of geothermal arsenic from Yangbajain power plant discharge in the Zangbo River,Tibet, China

The Yangbajain geothermal field located in central Tibet is characterized by the highest measured reservoir temperature among all hydrothermal systems in China. The high-temperature geothermal fluid extracted from Yangbajain has been used for electricity generation for over 30 years. The geothermal wastewater generated by the Yangbajain power plants, with arsenic (As) concentrations up to 3.18 mg/L, drains directly into the Zangbo River, the major surface water at Yangbajain, which has elevated arsenic concentrations in the segments downstream of wastewater discharges. However, along the flow direction of the river, the arsenic concentration decreases sharply. Further inspection reveals that the concentrations of weakly bound arsenic, strongly adsorbed arsenic and total arsenic in riverbed sediment were affected by the drainage of geothermal wastewater, indicating that the sediment serves as a sink for geothermal arsenic. A logarithmic relationship between the integrated attenuation coefficients (IAC) for three river segments and the corresponding adsorption distribution coefficients of riverbed sediment samples also suggests that besides the dilution of geothermal arsenic in the Zangbo River, natural attenuation of arsenic may be caused by sorption to riverbed sediment, thereby reducing its health threat to local residents using the Zangbo River as a drinking water source.     

Environmental Monitoring and Peat Assessment Using Multivariate Analysis of Regional-Scale Geochemical Data

A compositional multivariate approach was used to analyse regional-scale soil geochemical data obtained as part of the Tellus Project generated by the Geological Survey of Northern Ireland. The multi-element total concentration data presented comprise X-ray fluorescence (XRF) analyses of 6862 rural soil samples collected at 20-cm depth on a non-aligned grid at one site per \(2\,\hbox {km}^{2}\). Censored data were imputed using published detection limits. Each soil sample site was assigned to the regional geology map, resulting in spatial data for one categorical variable and 35 continuous variables comprised of individual and amalgamated elements. This paper examines the extent to which soil geochemistry reflects the underlying geology or superficial deposits. Since the soil geochemistry is compositional, log-ratios were computed to adequately evaluate the data using multivariate statistical methods. Principal component analysis (PCA) and minimum/maximum autocorrelation factors (MAF) were used to carry out linear discriminant analysis (LDA) as a means to discover and validate processes related to the geologic assemblages coded as age bracket. Peat cover was introduced as an additional category to measure the ability to predict and monitor fragile ecosystems. Overall prediction accuracies for the age bracket categories were 68.4 % using PCA and 74.7 % using MAF. With inclusion of peat, the accuracy for LDA classification decreased to 65.0 and 69.9 %, respectively. The increase in misclassification due to the presence of peat may reflect degradation of peat-covered areas since the creation of superficial deposit classification.     

漳州地热普查区地球化学异常的讨论

本文以漳州热田为例,通过对该区的地质及构造特征、地下热水分布、水化学特征及土壤地球化学异常的分析对照,论证了化探工作在地热勘查中的应用效果。同时,对热田的化探异常成因进行了初浅的探讨。     

Comparison of stream sediment and soil sampling for regional exploration in the eastern Alps,Austria

Tests in three different areas of the Austrian Alps showed that in mountainous areas, soil samples taken at the break of slope are an alternative sampling medium to stream sediments for regional geochemical exploration even if taken at the unusually low density of 1 sample/km². B-horizon soil samples from the nearest break of slope were collected in conjunction with stream sediment orientation studies. The minus 0.2 mm fraction of all samples was routinely analyzed for the total contents of 36 elements. The results for the indicator elements in the three test areas (Area 1: Cu; Area 2: Ag, As, Cu, Pb, Sb, Sn, Zn; Area 3: As, Cu) showed that break-of-slope soil samples more clearly indicate known mineralization than drainage geochemistry. In the soils, almost all elements showed a higher natural variability of the data with considerably higher metal contents. In mountaineous regions, each soil sample will have a clearly defined area of influence. The break of slope represents a site where clastically and hydromorphically dispersed elements are concentrated. It is concluded that soil samples can be used for regional exploration using low sampling densities in mountaineous areas. At the same time they will provide valuable information for other fields of science (e.g. agriculture, forestry, environmental sciences) and are thus superior to stream sediments.     

南京及周边地区土壤地球化学特征及基础地质应用探讨

南京及周边地区区域多目标地球化学调查与评价对调查区表、深层土壤采样分析了54项指标。提供了南京地区54项指标的表、深层土壤背景值,对比分析了背景值特点,讨论了元素地球化学区域分布特征,探讨了基础地质研究中地球化学在地层岩性、岩相划分方面的应用。     

双道氢化物原子荧光法同时测定地球化学样品中的微量砷和锑

已有大量研究工作表明砷是各种类型金矿床的极有效的探途元素,它也是许多热液多金属矿床的通用指示元素。锑作为指示元素做的工作比砷少,但是根据已有资料,它也是锑矿床、金矿床及多金属矿床的指示元素。我国最近发表的《苗龙金矿的发现》一文中很好地说明了砷及锑对找金矿的指示作用。     

惰性气体同位素确定地热流体循环深度

地热系统惰性气体同位素地球化学是地热成因研究的重要手段。许多惰性气体同位素都可用于地热系统的研究中,主要目的为揭示热田的热源性质、深-浅层地热流体的内在联系和循环深度等。本文从惰性气体理化特点、样品采集、测试技术及数据等若干方面介绍了惰性气体研究方法,重点探讨了在自由气和溶解气两种形态下,热泉、喷气孔、热水井不同环境下的惰性气体采样方法,还介绍了成熟的惰性气体同位素的测试方法,即利用磁偏转静态真空质谱计分析测试方法,最后基于世界各地典型地热系统的惰性气体测试数据,讨论地热系统的气体来源判别,不同气源的混合比例计算等,进而确定地热流体循环深度。     

原子荧光光谱法测定土壤和水系沉积物国家标准物质中砷

用王水浸提法和硝酸-高氯酸-氢氟酸混合酸消解法处理样品,原子荧光光度光谱法测定土壤和水系沉积物国家标准物质样品中的砷。方法检出限为0.02 mg/kg。两种前处理方法砷的测定值与标准值相符,均可以满足土壤和水系沉积物样品中砷含量的测定要求。单纯测定样品中砷含量时,王水浸提法更好;如果在测定砷同时还要测定其他元素,则可以选用混合酸消解法。     

Geochemical anomaly structure of South Mining District of Fenghuangshan Copper Mine

To study the geochemical anomaly structure of multi-element associations in the South Mining District of the Fenghuangshan Copper Mine,samples were collected and analyzed for their trace element contents.Multi-element anomaly associations were divided according to the correlations between Cu and each of the other elements,and the distribution characteristics of multi-element anomaly associations were also described.Among them,the anomaly distribution of metallogenic element Cu indicates the environment of mineralization.This study provided the basis for research on the metallogenic prediction and geochemistry of the Fenghuangshan Copper Mine.     

雄安新区地热地质模型探究：来自地球物理的证据

雄安新区内地热资源丰富，区内有牛驼镇地热田、容城地热田和高阳地热田，地热资源开发利用较早，但是对其深部热源机制仍未形成统一观点。为了研究雄安新区内地热田深部热源机制，在新区及外围进行了深反射地震和长周期大地电磁探测，对取得的同剖面的深反射地震和大地电磁数据进行处理和综合解释，探明了研究区从地表至莫霍面范围内地质构造和电性结构。下地壳结构在深反射地震剖面与大地电磁剖面上有很好的对应关系。电阻率低值区对应着在深反射地震剖面上存在一系列反射同相轴，且同相轴可以延续到莫霍面，电阻率高值区对应着在深反射地震剖面上无明显连续反射同相轴，尤其是在莫霍面之上呈现地震反射近似"空白区"。结合区域地热资料构建了研究区深部地热地质模型，对新区内深部地热机制进行了解释。该模型为"二元"生热模型，其热源包含两个部分，深部地幔热源和地壳放射性元素衰变生热。放射性元素衰变生热占地表热流的接近30%，而幔源热流在地表热流中的占比可达约70%。在牛驼镇下方，莫霍面以上，由于地幔热物质上涌造成下地壳上隆，幔源岩浆底侵作用于下地壳形成了局部热异常，该热异常具有低速高导的地球物理特征，认为是牛驼镇地热田和容城地热田的深部热源；以区域断裂为热通道，大地热流由深部向上传导、扩散到牛驼镇凸起和容城凸起顶部，对碳酸盐岩储水层进行加热，形成地热储层；上覆新近系沉积地层是良好的热盖层。     

Arsenic in geothermal sources at the north-central Andean region of Ecuador: concentrations and mechanisms of mobility

The arsenic content of geothermal hot springs and their sediments in the north-central Andean region of Ecuador has been investigated. The area of study is located between parallels 1°11′N and 1°30′S and includes five provinces. The area is rich in geothermal surface manifestations that are mainly used for medicinal baths in recreational complexes. Unfortunately, water residuals without treatment are released from the recreational facilities to surrounding water bodies. The results indicate that total arsenic in geothermal waters in this region has a range of 2–969 μg As/L, and sediments contain arsenic ranging from 1.6 to 717.6 mg/kg. Chemical analyses of sediment samples show the presence of sulfur, iron, aluminum and calcium. A high concentration of natural organic matter was also found in some samples (20–29.5%); thus sorption and coprecipitation can be the main mechanisms of As immobilization on mineral phases and natural organic matter.     

关中盆地地温场划分及其地质影响因素

具有无污染、可再生、分布广、储量大以及可就近利用等诸多优势的地热能是一种洁净能源,应用前景广阔。地热能的开发利用与区域地温场划分紧密相关,关于关中盆地整体地温场划分的研究鲜有报道。根据关中盆地的工程地质、水文地质、环境地质条件等因素,总结了岩体类和砂土类的热物性质特征。通过灰色关联分析方法,分析了岩土体热物性参数的影响因素,认为干燥重度对导热系数的影响程度最大,含水率、天然重度、孔隙率三者影响程度相近;干燥重度对比热容影响程度最大,天然重度次之,含水率和孔隙率影响最弱。利用盆地内多个地温常观孔,绘制了地温变化曲线和地温梯度等值线,认为关中盆地常温带位于15~20 m埋深处,地温梯度总体呈中部高、东西低,固市凹陷、西安凹陷、蒲城凸起、断裂及断裂汇合区域地温梯度较大,宝鸡凸起、咸礼凸起以及临蓝凸起地温梯度较小,产生差异的原因包括地质构造、地下水活动、岩土体热物性参数等三方面。利用热物性参数和地温梯度值,计算了盆地内浅层和深层的大地热流值,并分析了两者差异的成因,经对比全国区域地热资料,认为关中盆地是一个复杂的坳陷型中低温地热田,地热资源潜力巨大,居全国上游。该文旨在系统地分析关中盆地地温场特征,为地热能的勘查评价提供基础数据支持,促进关中盆地地热开发利用,为构建环境友好型社会服务。     

淮南煤田现今地温场特征

在系统分析淮南煤田大量地面钻孔井温测井数据和井下巷道围岩温度测试数据的基础上,结合58块岩石样品的热导率测试结果,全面阐述了该区现今地温梯度和大地热流的分布特征。研究表明,淮南煤田现今地温梯度的众值介于2.50~3.50℃/hm之间,平均地温梯度为2.9℃/hm;大地热流值变化范围为31.87~83.9 m W/m2,平均热流值为63.69 m W/m2,地温梯度和热流值区均高于淮北煤田;大地热流受地温梯度控制明显,其变化特征和地温梯度分布较为相似,整体表现为中东部高,西部其次,东南部最小的特征。分析揭示,区内现今地温场和热流分布主要受区域地质背景和区内构造格局的控制。     

淮北煤田现今地温场特征及大地热流分布

淮北煤田的高温热害问题愈发突出,但目前对该区系统的地温场特征及大地热流分布研究非常稀少.在系统分析淮北煤田大量地面钻孔井温测井数据和井下巷道围岩温度测试数据的基础上,结合72块岩石样品的热导率测试结果,全面阐述了该区现今地温梯度和大地热流的分布特征.研究表明:淮北煤田现今地温梯度众值介于1.80~2.80 ℃/100 m之间,平均地温梯度为2.42 ℃/100 m;大地热流值变化范围为39.52~74.12 mW/m2,平均热流值为55.72 mW/m2,地温梯度和热流值均低于同处华北板块的其他盆地以及南部的淮南煤田;大地热流受地温梯度控制明显,两者分布较为相似,整体表现为南高北低、西高东低的特点.结果表明,区内现今地温场和热流分布主要受区域地质背景和区内构造格局的控制.      

南京市浅层地温场监测方案和地温分布特点研究

浅层地温能作为可再生能源,已经引起广泛关注。为了有效地监测南京市浅层地温场的时空演化,针对4种温度传感器：DTS、FBG、Pt100和iButton,通过野外和室内试验进行分析对比,从测温精度、适用范围、工作特性等方面展开研究。结合试验结果和目前的实际应用情况,总结出四种传感器在浅层地温场监测方面的优缺点和特性,并制定出一套较为完善的监测方案,为浅层地温场的长期时空监测提供参考：在所有钻孔中埋设分布式测温光纤,并根据地温钻孔的土层分布和所获取的地温分布数据,选取两个较为典型的地温钻孔布设FBG测温串;在所有钻孔点距地表5 cm处布设iButton,并使用Pt100监测地表以下25 m内的精确地温。根据已获得的监测数据,可总结出南京地区浅层地温在垂向上的大体分布规律,发现其分布在空间上具有差异性,浅地表地温与地表覆盖层、大气及太阳辐射有关,深部地温受地质构造和水文地质条件等因素控制。     

Dealing with outliers and censored values in multi-element geochemical data – a visualization approach using XmdvTool

Dealing with geochemical data also means coping with their underlying limitations that are related to sampling, analytical techniques, and other characteristics of the data. This paper discusses the issue of data cleaning, using a regional geochemical dataset of 6 heavy metals in glacial till. Interactive data manipulation techniques provided in the freeware visualization system XmdvTool were used for exploring both metal concentrations reported as under the detection limit, and high or extreme values (outliers) in the dataset. The proposed integrated visual evaluation (IVE) approach for selective removal of outliers outperformed simple removal of the highest concentrations of metals, showing that existing spatial multi-element fingerprints in data could be recognized and preserved by IVE. The uniqueness of visualization is in simultaneous display of both multivariate and spatial information. Being simple and interactive, integrated visual evaluation can be recommended as a valuable complementary tool in cleaning and analysing multi-element geochemical data.     

Arsenic in soil, vegetation and water of a contaminated region

Arsenic concentrations of surface waters, soils and plants were surveyed in three contaminated villages of Bijar County. Total arsenic in water samples (4.5 to 280 μg/L) was correlated with electrical conductivity, total dissolved solid, total hardness, alkalinity, chloride, sulphate, bicarbonate, calcium and sodium (p<0.001). Total arsenic in the soils ranged from 105.4 to 1500 mg/kg. Some of the soil factors play an important role in soil arsenic content and its bioavailability for organisms. In general, the arsenic concentrations in plants were low, especially in the most common wild species. Among 13 plant species, the highest mean arsenic concentration was found in leaves of Mentha Longifolia (79.4 mg/kg). Arsenic levels in soils and plants were positively correlated, while the ability of the plants to accumulate the element, expressed by their biological accumulation coefficients and arsenic transfer factors, was independent of the soil arsenic concentration. Relationships between the arsenic concentrations in plants, soils and surface water and the environmental aspects of these relationships have been discussed in comparison with literature data. The accumulation of arsenic in environmental samples (soil, sediment, water, plant, etc.) poses a potential risk to human health due to the transfer of this element in aquatic media, their uptake by plants and subsequent introduction into the food chain.     

A soil geochemistry orientation survey for uranium at Koongarra, Northern Territory

A soil geochemistry orientation survey for U at Koongarra was designed to determine optimum conditions for future U exploration in the area. Soil samples were collected at various depths from auger holes drilled along two traverses over the Koongarra No. 1 orebody, along a single traverse over suspected mineralization at nearby Anomaly A, and at three background localities. Rock samples collected from surface outcrop, costeans, and drill core were used to investigate any elemental associations with the ore or primary dispersion which could then be traced in the overlying soils.The results showed that Cu and Pb are potentially suitable pathfinder elements, where U data are not definitive, while Co, Ni and Be also provide significant information. The optimum sample depth was 1.2 m. For a Koongarra-sized target the maximum sample spacing should be 30 m on lines 200 m apart, provided every anomalous sample is followed up with closer spaced sampling around it. Anomalies detected in alluvial soil deeper than 1.2 m were due to hydromorphic dispersion. Some of the general distribution patterns for individual elements may be related to soil-type variations.