Hydrogeochemical characteristics of spring water in the Harz Mountains,Germany

Spring water samples of the Harz Mountains were taken in several seasons of 2010, 2011, and 2012. The samples have been analysed for main components (Na⁺, K⁺, Ca²⁺, Mg²⁺, SO₄²⁻, Cl⁻, HCO₃⁻ and NO₃⁻), trace elements (Fe, Cu, Pb, Zn, Y and REE), DOC, δ¹⁸O and δ²H of water. Meteoric water is indicated as the main source of the springs sampled. High precipitation rates lead to a dilution of the measured elemental concentrations. Furthermore, regional differences of rock and water interactions were found. REE concentrations and patterns of the spring waters vary between the distinct geological units and reflect the geochemical characteristics of the surrounding rocks. The actual data compared to measured data from the seventies and nineties of the last century indicate a decrease of the sulphate concentrations in the spring waters which is typical of many European mountain catchments.     

Use of principal component analysis for identification of Rockland and Trego Hot Springs tephras in the Hat Creek Graben,northeastern California,USA

Discontinuous tephra layers were discovered at Burney Spring Mountain, northern California. Stratigraphic relationships suggest that they are two distinct tephras. Binary plots and standard similarity coefficients of electron probe microanalysis data have been supplemented with principal component analysis to correlate the two tephra layers to known regional tephras. Using principal component analysis, we are furthermore able to bound our uncertainty in the correlation of the two tephra layers. After removal of outliers, within the 95% prediction interval, we can say that one tephra layer is likely the Rockland tephra, aged 565–610 ka, and the second layer is likely from Mt. Mazama, the Trego Hot Springs tephra, aged ~ 29 ka. In the case of the Rockland tephra, the new findings suggest that dispersal to the north was highly restricted. For Trego Hot Springs ash, the new findings extend the distribution to the southwest, with a rapid thinning in that direction. Coupled with considerations of regular tephra dispersal patterns, the results suggest that the primary dispersal direction for both tephras was to the south, and that occurrences in other directions are unlikely or otherwise anomalous.     

Alice Springs age shear zones from the southeastern Reynolds Range,central Australia

The southeast Reynolds Range, central Australia, is cut by steep northwest‐trending shear zones that are up to hundreds of metres wide and several kilometres long. Amphibolite‐facies shear zones cut metapelites, while greenschist‐facies shear zones cut metagranites. Rb–Sr and ⁴⁰Ar–³⁹Ar data suggest that both sets of shear zones formed in the 400–300 Ma Alice Springs Orogeny, with the sheared granites yielding well‐constrained ⁴⁰Ar–³⁹Ar ages of ca 334 Ma. These data imply that the shear zones represent a distinct tectonic episode in this terrain, and were not formed during cooling from the ca 1.6 Ga regional metamorphism. A general correlation between regional metamorphic grade and the grade of Alice Springs structures implies a similar distribution of heat sources for the two events. This may be most consistent with both phases of metamorphism being caused by the burial of anomalously radiogenic heat‐producing granites. The sheared rocks commonly have undergone metasomatism implying that the shear zones were conduits of fluid flow during Alice Springs times.     

Geochemistry of a spring-dense karst watershed located in a complex structural setting, Appalachian Great Valley, West Virginia, USA

The distribution and chemistry of the springs in the Tuscarora Creek watershed is controlled by both geologic structure and karst dissolution. The watershed is located in eastern West Virginia in the structurally complex Great Valley of the Appalachian Valley and Ridge province. The upper portion of the stream parallels strike along a mapped fault zone and is bordered by clastic rocks that comprise North Mountain. The lower reaches of the stream flow cross-strike through Cambro-Ordovician carbonates. The controlling chemical signature in the spring water is carbonate dissolution. Little evidence was seen for the recharge from adjacent clastic rocks although differences in the Ca/Mg molar ratio between springs indicated the presence of localized spring basins in headwater reaches. Na, Cl and Ca generally increased from upstream to downstream in the cross-strike reaches. Comparison of stream and cumulative spring discharge was consistent with significant groundwater base-flow contribution directly to the creek, particularly in the strike-parallel region. The largest spring in the watershed (>162 L/s) was sampled during and after a large storm event along with the adjacent creek. The creek displayed a typical dilution response with each flood pulse, whereas the spring had only a limited or delayed response. The overall chemical and thermal stability of the spring, relative to the creek, indicated the lack of significant direct hydraulic connection between the two. The conceptual model for the area includes localized flowpaths in the headwater region where the stream flow is parallel to strike and a thrust fault. In addition to the shallow localized flowpaths, a deeper, more regional flowpath likely exists for a large spring further downstream.     

Ground-based hyperspectral remote sensing of hydrocarbon-induced rock alterations at cement,Oklahoma

Hydrocarbon seepages bring oil and gas from petroleum reservoirs to the surface, these hydrocarbons can generate various kinds of rock alterations, including bleaching of red beds and mineralogical changes. Satellite and airborne remote sensing techniques have been utilized in the detection of rock alterations and hydrocarbon seepages; however, they have limited resolutions and are unable to map vertical outcrops. Ground-based remote sensing techniques hold great potential to characterize rocks with great precisions and resolutions. This study used ground-based Specim hyperspectral data to detect hydrocarbon-induced rock alterations of the Rush Springs sandstone at the Cement field in southeast Anadarko basin, Oklahoma. Hyperspectral data of outcrops and hand specimens were examined, and spectral angle mapper technique was used to compare spectral similarity between image pixels and reference spectra. Laboratory spectroscopy was used to assist with mineral identification and image classification. Remote sensing data detected bleaching of red beds and carbonate cementation. Combining lithological, spectroscopic, remote sensing and geochemical data, this study built a model for petroleum seepage and related rock alterations, and provided a workflow for employing remote sensing techniques in resource exploration.     

Simulating effect of anthropogenic activities and climate variation on Liulin Springs discharge depletion by using the ARIMAX model

Based on the groundwater development process, and regional economic and social developing history, we divided the spring hydrological process of the Liulin Springs Basin into two periods: pre‐1973 and post‐1974. In the first period (i.e. 1957–1973), the spring discharge was affected by climate variation alone, and in the second period (i.e. 1974–2009), the spring discharge charge was influenced by both climate variation and human activities. A piecewise analysis strategy was used to differentiate the contribution of anthropogenic activities from climate variation on karst spring discharge depletion in the second period. Then, the ARIMAX model was applied to spring flow time series of the first period to develop a model for the effects of climate variation only. Using this model, we estimated the spring discharge in the second period solely under the influence of climate variation. Based on the water budget, we subtracted observed spring discharge from the estimated spring discharge and acquired the contribution of human activities on spring discharge depletion for the second period. The results of the analysis indicated that the contribution of climate variation to the spring discharge depletion is?0.20 m³/s from 1970s to 2000s. The contribution of anthropogenic activities to the spring flow depletion was ?2.56 m³/s in 2000s, which was about 13 times more than that of climate variation. Our analysis further indicates that groundwater exploitation only accounts for 29% of the spring flow depletion due to the effects of human activities. The remaining 71% of the depletion is likely to be caused by other human activities, including dam building, dewatering during coal mining, and deforestation. Copyright © 2012 John Wiley & Sons, Ltd.     

Exhumation of the lower crust during crustal shortening: an Alice Springs (380 Ma) age for a prograde amphibolite facies shear zone in the Strangways Metamorphic Complex (central Australia)

Foliated garnet-bearing amphibolites occur within the West Bore Shear Zone, cutting through granulite facies gneisses of the Strangways Metamorphic Complex. In the amphibolites, large euhedral garnet (up to 3 cm) occurs within fine-grained recrystallized leucocratic diffusion haloes of plagioclase–quartz. The garnet and their haloes include a well-developed vertical foliation, also present in the matrix. This foliation is the same as that cutting through the unconformably overlying Neoproterozoic Heavitree Quartzite. The textures indicate syn- to late kinematic growth of the amphibolite facies mineral assemblages.
All mineral assemblages record an arrested prograde reaction history. Noteworthy is the growth of garnet at the expense of hornblende and plagioclase, and the breakdown of staurolite–hornblende to give plagioclase–gedrite. These dehydration reactions indicate increasing P – T  conditions during metamorphism, and suggest heating towards the end of a period of intense deformation. Temperature estimates for the garnet–amphibolite and related staurolite–hornblende assemblages from the shear zone are about 600 °C. Pressure is estimated at about 5 kbar.
An Sm–Nd isochron gives an age of 381±7 Ma for the peak metamorphism and associated deformation. This age determination confirms that amphibolite facies conditions prevailed during shear zone development within the Strangways Metamorphic Complex during the Alice Springs Orogeny. These temperature conditions are significantly higher than those expected at this depth assuming a normal geothermal gradient. The Alice Springs Orogeny was associated with significant crustal thickening, allowing exhumation of the granulite facies, Palaeoproterozoic, lower crust. Along-strike variations of the tectonic style suggest a larger amount of crustal shortening in the eastern part of the Alice Springs Orogeny.     

胶东温泉地热水水化学及同位素特征研究

对胶东半岛出露的14处温泉的水化学特征、同位素特征进行了分析,得出胶东半岛温泉水的来源主要为大气降水补给、海水补给,年龄以现代水为主。胶东半岛温泉水与围岩矿物未达到完全平衡,不适宜用Na,K,Mg地热温标,玉髓的地热温标显示胶东半岛温泉热储温度在81．26～108．93℃之间。对下一步胶东半岛的温泉地热勘查、开发利用具有指导意义。     

胶东温泉地热水水化学及同位素特征研究

对胶东半岛出露的14处温泉的水化学特征、同位素特征进行了分析,得出胶东半岛温泉水的来源主要为大气降水补给、海水补给,年龄以现代水为主。胶东半岛温泉水与围岩矿物未达到完全平衡,不适宜用Na,K,Mg地热温标,玉髓的地热温标显示胶东半岛温泉热储温度在81．26～108．93℃之间。对下一步胶东半岛的温泉地热勘查、开发利用具有指导意义。     

Distribution and occurrence of some naturally‐occurring polytypes of molybdenite in Australia and Papua New Guinea

156 samples of naturally‐occurring molybdenite from 87 localities in Australia have been examined to determine the distribution of the hexagonal (2H₁) and rhombohedral (3R) polytypes. 90% of the specimens examined are 2H₁ polytypes, the remainder being 3R and mixtures of 2H₁ and 3R polytypes. The 3R and mixed polytypes are more abundant in porphyry copper deposits or as disseminations, in veins, and in garnet‐quartz pipes in granite. 2H₁ polytypes are the sole modification observed in pegmatites, quart‐pegmatite pipes, simple quartz veins, and skarns.

The highest average concentrations of rhenium are in molybdenite from porphyry copper deposits, quartz porphyry pipes, skarn deposits, garnet‐quartz pipes, and pegmatites. Low concentrations occur in molybdenite which is disseminated or in quartz veins in granite and in quartz or pegmatitic pipes. Molybdenites in which the 2H₁ polytype is dominant have a lower average rhenium content than those with dominant 3R polytype.