Origin and evolution of the Steamboat Springs siliceous sinter deposit, Nevada, U.S.A.

Siliceous hot spring deposits from Steamboat Springs, Nevada, U.S.A., record a complex interplay of multiple, changing, primary environmental conditions, fluid overprinting and diagenesis. Consequently these deposits reflect dynamic geologic and geothermal processes. Two surface sinters were examined—the high terrace, and the distal apron-slope, as well as 13.11 m (43 ft) of core material from drill hole SNLG 87-29. The high terrace sinter consists of vitreous and massive-mottled silica horizons, while the distal deposit and core comprise dominantly porous, indurated fragmental sinters. Collectively, the three sinter deposits archive a complete sequence of silica phase diagenetic minerals from opal-A to quartz. X-ray powder diffraction analyses and infrared spectroscopy of the sinters indicate that the distal apron-slope consists of opal-A and opal-A/CT mineralogy; the core yielded opal-A/CT and opal-CT with minor opal-A; and the high terrace constitutes opal-C, moganite, and quartz. Mineralogical maturation of the deposit produced alternating nano–micro–nano-sized silica particle changes. Based on filament diameters of microbial fossils preserved within the sinter, discharging thermal outflows fluctuated between low-temperatures (< 35 °C, coarse filaments) and mid-temperatures ( 35–60 °C, fine filaments). Despite transformation to quartz, primary coarse and fine filaments were preserved in the high terrace sinter. AMS ¹⁴C dating of pollen from three horizons within core SNLG 87-29, from depths of 8.13 to 8.21 m (26′8″ to 26′11″), 10.13 to 10.21 m (33′3″ to 33′6″), and 14.81 to 14.88 m (48′7″ to 48′10″), yielded dates of 8684 ± 64 years, 11,493 ± 70 years and 6283 ±60 years, respectively. In the upper section of the core, the stratigraphically out-of-sequence age likely reflects physical mixing of younger sinter with quartzose sinter fragments derived from the high terrace. Within single horizons, mineralogical and morphological components of the sinter matrix were spatially patchy. Overall, the deposit was modified by sub-surface flow of alkali-chloride thermal fluids depositing a second generation of silica, and periodically, by acidic steam condensate formed during periods when the water table was low. Local faulting produced considerable fracturing of the sinter. Hence, the Steamboat Springs sinter experienced a complex history of primary and secondary hydrothermal, geologic and diagenetic events, and their inter-relationships and effects are locked within the physical, chemical and biological signatures of the deposit.     

中国火山温泉气体地球化学特征及其在火山监测中的应用

中国火山温泉主要分布在吉林长白山、云南腾冲和黑龙江五大连池等火山区。这些火山虽然处于休眠状态,但大面积的温泉分布指示着岩浆房存在的可能性。本文总结了前人研究成果,分析了中国主要火山区温泉气体地球化学特征,并探讨了温泉气体在火山监测中的应用。长白山、腾冲和五大连池火山区温泉气体地球化学性质类似,都以CO₂为主要气体,含量在80%以上,最高可达99%以上,其它气体组分包括CH₄、N₂、O₂、SO₂、H₂S、He和H₂等。长白山火山温泉气体中氦同位素比值（3He/4He）最高,约为4—6R_A,CO₂中碳同位素比值（δ13C）为-7.9‰—-1.3‰,CH₄中碳同位素为-48.0‰—-28.7‰;腾冲火山温泉气体氦同位素比值为3—5.5R_A,CO₂中的碳同位素为-6.49‰—-2.07‰,CH₄中碳同位素为-23.5‰—-9.3‰;五大连池火山温泉气体氦同位素比值约为3R_A,CO₂中的碳同位素比值为-9.6‰—-3.1‰,CH₄中碳同位素为-47.2‰—-44.4‰。3个火山区的温泉气体均显示地幔来源的岩浆气体特征,并在上升运移过程中受地壳或古俯冲物质的影响。     

Isotope hydrology of a tropical coffee agroforestry watershed: Seasonal and event‐based analyses

Stable isotope variations are extremely useful for flow partitioning within the hydrologic cycle but remain poorly understood throughout the tropics, particularly in watersheds with rapidly infiltrating soils, such as Andisols in Central America. This study examines the fluctuations of stable isotope ratios (δ¹⁸O and δ²H) in the hydrologic components of a tropical coffee agroforestry watershed (~1 km²) with Andisol soils in Costa Rica. Samples were collected in precipitation, groundwater, springs, and stream water over 2 years. The local meteoric water line for the study site was δ²H = 8.5 δ¹⁸O + 18.02 (r² = 0.97, n = 198). The isotope ratios in precipitation exhibited an enriched trend during the dry season and a notable depletion at the beginning of the wet season. The δ¹⁸O compositions in groundwater (average = ?6.4‰, σ = 0.7) and stream water (average = ?6.7‰, σ = 0.6) were relatively stable over time, and both components exhibited more enriched values in 2013, which was the drier year. No strong correlation was observed between the isotope ratios and the precipitation amount at the event or daily time‐step, but a correlation was observed on a monthly scale. Stream water and base flow hydrograph separations based on isotope end‐member estimations showed that pre‐event water originating from base flow was prevalent. However, isotope data indicate that event water originating from springs appears to have been the primary driver of initial rises in stream flow and peak flows. These results indicate that isotope sampling improves the understanding of water balance components, even in a tropical humid location, where significant variations in rainfall challenge current modelling efforts. Further research using fine‐scale hydrometric and isotopic data would enhance understanding the processes driving spring flow generation in watersheds.     

Hydrogeology of desert springs in the Panamint Range,California, USA: Geologic controls on the geochemical kinetics,flowpaths, and mean residence times of springs

Over 180 springs emerge in the Panamint Range near Death Valley National Park, CA, yet, these springs have received very little hydrogeological attention despite their cultural, historical, and ecological importance. Here, we address the following questions: (1) which rock units support groundwater flow to springs in the Panamint Range, (2) what are the geochemical kinetics of these aquifers, and (3) and what are the residence times of these springs? All springs are at least partly supported by recharge in and flow through dolomitic units, namely, the Noonday Dolomite, Kingston Peak Formation, and Johnnie Formation. Thus, the geochemical composition of springs can largely be explained by dedolomitization: the dissolution of dolomite and gypsum with concurrent precipitation of calcite. However, interactions with hydrothermal deposits have likely influenced the geochemical composition of Thorndike Spring, Uppermost Spring, Hanaupah Canyon springs, and Trail Canyon springs. Faults are important controls on spring emergence. Seventeen of twenty-one sampled springs emerge at faults (13 emerge at low-angle detachment faults). On the eastern side of the Panamint Range, springs emerge where low-angle faults intersect nearly vertical Late Proterozoic, Cambrian, and Ordovician sedimentary units. These geologic units are not present on the western side of the Panamint Range. Instead, springs on the west side emerge where low-angle faults intersect Cenozoic breccias and fanglomerates. Mean residence times of springs range from 33 (±30) to 1,829 (±613) years. A total of 11 springs have relatively short mean residence times less than 500 years, whereas seven springs have mean residence times greater than 1,000 years. We infer that the Panamint Range springs are extremely vulnerable to climate change due to their dependence on local recharge, disconnection from regional groundwater flow (Death Valley Regional Flow System - DVRFS), and relatively short mean residence times as compared with springs that are supported by the DVRFS (e.g., springs in Ash Meadows National Wildlife Refuge). In fact, four springs were not flowing during this campaign, yet they were flowing in the 1990s and 2000s.     

Discovery of the Avon – Solent Fracture Zone and its relationship to Bath hot springs

 The hot springs of Bristol and Bath and two geothermal wells at Southampton are located on a 155-km-long Avon–Solent Fracture Zone extending in a NW–SE direction from the Severn Estuary to the English Channel. Initiated during the Variscan earth movements and reactivated in Miocene times, the structure, which extends across the English Channel to France, is still active. With this discovery, it should now be possible to throw fresh light on the origin and movement of the thermal water at Bath and thus to protect the hot springs from derogation by limestone quarrying. Received: 16 October 1995 · Accepted: 13 February 1996     

自喷生产井深层卤水的动态分析

本文以四川盆地中部的P_1井为例,分析自喷型深层卤水生产钻井的开采动态特征,建立生产指标之间的统计关系,并预测钻井自喷阶段的总产量。     

Modelling discharge through artesian springs based on a high‐resolution piezometric network

Artesian springs are localized aquifer outlets that originate when pressurized ground water is allowed to rise to the surface. Computing artesian discharge directly is often subject to practical difficulties such as restricted accessibility, abundant vegetation or slow flow rates. These circumstances call for indirect approaches to quantify flow. This paper presents a method to estimate ground water discharge through an upwelling spring by means of a three‐layer steady‐state groundwater flow model. Model inputs include on‐site measurements of vertical sediment permeability, sediment temperatures and hydraulic gradients. About 70 spring bed piezometers were used to carry out permeability tests within the spring sediments, as well as to quantify the hydraulic head at different depths below the discharge point. Sediment temperatures were measured at different depths and correlated to permeabilities in order to demonstrate the potential of temperature as a substitute for cumbersome slug tests. Results show that the spatial distribution of discharge through the spring bottom is highly heterogeneous, as sediment permeability varies by several orders of magnitude within centimetres. Sensitivity analyses imply that geostatistical interpolation is irrelevant to the results if field datasets come from a sufficiently high resolution of piezometric records. Copyright © 2013 John Wiley & Sons, Ltd.     

即墨温泉地热水水质的动态变化特征

即墨温泉是一种含多种化学元素的高矿化度热水资源,在深部地下热水沿断裂带上涌的过程中可能与浅部冷水发生不同程度的混合,使开采获得的地热水水质也发生了相应的变化。对即墨温泉地热资源核心开采区2口开采深度不同的地热井进行了为期1个水文年的水质变化监测,地热水水质参数上半年比下半年高,水质参数发生急剧变化的时间相对于气候的季节性变化有2～3个月的滞后,且氯度、矿化度和电导率的季节性变化幅度在开采深度较浅的水井中较大,表明开采条件和区域性气候条件的变化共同控制了地热水水质变化。     

山东大学齐鲁医院综合楼工程对济南泉水的影响分析

通过对山东大学齐鲁医院门诊保健综合楼工程建设对泉水是否影响的论证,认为场区内第四系碎屑岩孔隙裂隙水与奥陶系裂隙岩溶水为2个不同的含水系统。拟建工程在开挖深度内未揭穿第四系砾岩层,保留部分砾岩层作为基底持力层,并保持了下伏黏土的天然隔水性能,不会阻挡地下水径流补给通道,对泉水不会造成影响。