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21.
Pinarelli Laura Gioncada Anna Capaccioni Bruno Vaselli Orlando Downes Hilary 《Mineralogy and Petrology》2019,113(1):39-60
Mineralogy and Petrology - Vulcano is part of the Aeolian volcanic arc in the southern Tyrrhenian Sea. Its products were emplaced through multiple episodes of edifice building and collapse since... 相似文献
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23.
Ardiansyah Koeshidayatullah Hilary Corlett Jack Stacey Peter K. Swart Adrian Boyce Hamish Robertson Fiona Whitaker Cathy Hollis 《Sedimentology》2020,67(6):2945-2973
Fault-controlled hydrothermal dolomitization in tectonically complex basins can occur at any depth and from different fluid compositions, including ‘deep-seated’, ‘crustal’ or ‘basinal’ brines. Nevertheless, many studies have failed to identify the actual source of these fluids, resulting in a gap in our knowledge on the likely source of magnesium of hydrothermal dolomitization. With development of new concepts in hydrothermal dolomitization, the study aims in particular to test the hypothesis that dolomitizing fluids were sourced from either seawater, ultramafic carbonation or a mixture between the two by utilizing the Cambrian Mount Whyte Formation as an example. Here, the large-scale dolostone bodies are fabric-destructive with a range of crystal fabrics, including euhedral replacement (RD1) and anhedral replacement (RD2). Since dolomite is cross-cut by low amplitude stylolites, dolomitization is interpreted to have occurred shortly after deposition, at a very shallow depth (<1 km). At this time, there would have been sufficient porosity in the mudstones for extensive dolomitization to occur, and the necessary high heat flows and faulting associated with Cambrian rifting to transfer hot brines into the near surface. While the δ18Owater and 87Sr/86Sr ratios values of RD1 are comparable with Cambrian seawater, RD2 shows higher values in both parameters. Therefore, although aspects of the fluid geochemistry are consistent with dolomitization from seawater, very high fluid temperature and salinity could be suggestive of mixing with another, hydrothermal fluid. The very hot temperature, positive Eu anomaly, enriched metal concentrations, and cogenetic relation with quartz could indicate that hot brines were at least partially sourced from ultramafic rocks, potentially as a result of interaction between the underlying Proterozoic serpentinites and CO2-rich fluids. This study highlights that large-scale hydrothermal dolostone bodies can form at shallow burial depths via mixing during fluid pulses, providing a potential explanation for the mass balance problem often associated with their genesis. 相似文献
24.
Cyrena Anne Goodrich Hilary Downes Richard Greenwood Aidan J. Ross Anna Maria Fioretti Louise Alexander Noriko T. Kita Jon Butler Michael J. Jercinovic Peter Jenniskens Muawia H. Shaddad 《Meteoritics & planetary science》2024,59(4):719-753
The anomalous polymict ureilite Almahata Sitta (AhS) fell in 2008 when asteroid 2008 TC3 disintegrated over Sudan and formed a strewn field of disaggregated clasts of various ureilitic and chondritic types. We studied the petrology and oxygen isotope compositions of enstatite meteorite samples from the University of Khartoum (UoK) collection of AhS. In addition, we describe the first bona fide (3.5 mm-sized) clast of an enstatite chondrite (EC) in a typical polymict ureilite, Northwest Africa (NWA) 10657. We evaluate whether 2008 TC3 and typical polymict ureilites have a common origin, and examine implications for the history of enstatite meteorite asteroids in the solar system. Based on mineralogy, mineral compositions, and textures, the seven AhS EC clasts studied comprise one EHa3 (S151), one ELb3 (AhS 1002), two EHb4-5 (AhS 2012, AhS 26), two EHb5-6 or possibly impact melt rocks (AhS 609, AhS 41), and one ELb6-7 (AhS 17), while the EC clast in NWA 10657 is EHa3. Oxygen isotope compositions analyzed for five of these are similar to those of EC from non-UoK collections of AhS, and within the range of individual EC meteorites. There are no correlations of oxygen isotope composition with chemical group or subgroup. The EC clasts from the UoK collection show the same large range of types as those from non-UoK collections of AhS. The enstatite achondrite, AhS 60, is a unique type (not known as an individual meteorite) that has also been found among non-UoK AhS samples. EC are the most abundant non-ureilitic clasts in AhS but previously were thought to be absent in typical polymict ureilites, necessitating a distinct origin for AhS. The discovery of an EC in NWA 10657 changes this. We argue that the types of materials in AhS and typical polymict ureilites are essentially similar, indicating a common origin. We elaborate on a model in which AhS and typical polymict ureilites formed in the same regolith on a ureilitic daughter body. Most non-ureilitic clasts are remnants of impactors implanted at ~50–60 Myr after CAI. Differences in abundances can be explained by the stochastic nature of impactor addition. There is no significant difference between the chemical/petrologic types of EC in polymict ureilites and individual EC meteorites. This implies that fragments of the same populations of EC parent bodies were available as impactors at ~50–60 Myr after CAI and recently. This can be explained if materials excavated from various depths on EC bodies at ~50–60 Myr after CAI were reassembled into mixed layers, leaving relatively large bodies intact to survive 4 billion years. Polymict ureilites record a critical timestep in the collisional and dynamical evolution of the solar system, showing that asteroids that may have accreted at distant locations had migrated to within proximity of one another by 50–60 Myr after CAI, and providing constraints on the dynamical processes that could have caused such migrations. 相似文献
25.
Integrated method of RS and GPR for monitoring the changes in the soil moisture and groundwater environment due to underground coal mining 总被引:3,自引:0,他引:3
Zhengfu Bian Shaogang Lei Hilary I. Inyang Luqun Chang Richen Zhang Chengjun Zhou Xiao He 《Environmental Geology》2009,57(1):131-142
Mining affects the environment in different ways depending on the physical context in which the mining occurs. In mining areas
with an arid environment, mining affects plants’ growth by changing the amount of available water. This paper discusses the
effects of mining on two important determinants of plant growth—soil moisture and groundwater table (GWT)—which were investigated
using an integrated approach involving a field sampling investigation with remote sensing (RS) and ground-penetrating radar
(GPR). To calculate and map the distribution of soil moisture for a target area, we initially analyzed four models for regression
analysis between soil moisture and apparent thermal inertia and finally selected a linear model for modeling the soil moisture
at a depth 10 cm; the relative error of the modeled soil moisture was about 6.3% and correlation coefficient 0.7794. A comparison
of mined and unmined areas based on the results of limited field sampling tests or RS monitoring of Landsat 5-thermatic mapping
(TM) data indicated that soil moisture did not undergo remarkable changes following mining. This result indicates that mining
does not have an effect on soil moisture in the Shendong coal mining area. The coverage of vegetation in 2005 was compared
with that in 1995 by means of the normalized difference vegetation index (NDVI) deduced from TM data, and the results showed
that the coverage of vegetation in Shendong coal mining area has improved greatly since 1995 because of policy input RMB¥0.4
per ton coal production by Shendong Coal Mining Company. The factor most affected by coal mining was GWT, which dropped from
a depth of 35.41 m before mining to a depth of 43.38 m after mining at the Bulianta Coal Mine based on water well measurements.
Ground-penetrating radar at frequencies of 25 and 50 MHz revealed that the deepest GWT was at about 43.4 m. There was a weak
water linkage between the unsaturated zone and groundwater, and the decline of water table primarily resulted from the well
pumping for mining safety rather than the movement of cracking strata. This result is in agreement with the measurements of
the water wells. The roots of nine typical plants in the study area were investigated. Populus was found to have the deepest
root system with a depth of about 26 m. Based on an assessment of plant growth demands and the effect of mining on environmental
factors, we concluded that mining will have less of an effect on plant growth at those sites where the primary GWT depth before
mining was deep enough to be unavailable to plants. If the primary GWT was available for plant growth before mining, especially
to those plants with deeper roots, mining will have a significant effect on the growth of plants and the mechanism of this
effect will include the loss of water to roots and damage to the root system. 相似文献
26.
The comparative limnology of some New Zealand lakes 总被引:1,自引:1,他引:0
V. Hilary Jolly 《新西兰海洋与淡水研究杂志》2013,47(2):214-259
The morphometry, environmental conditions, and some physical and chemical data are given for twenty‐four New Zealand lakes: seven are in the southern part of the South Island, the others, excluding Lakes Waikaremoana and Waikareiti, are in the “thermal region” of the central North Island. These lakes form two separate groups and include the largest and deepest lakes in both islands. The lakes in which stratification was established were found to belong to the class known as warm monomictic Two lakes, Rotorua and Rotoehu, were found to be homothermous throughout the year. Open water surface temperatures did not exceed 23°c in the North Island lakes or 19°c in the South Island, and minimum temperatures recorded were 7°c in the northern lakes and 5°c in the southern. In deep lakes the range of temperature was much less: Wakutipu had a range of 16–8.85°c. The disappearance level of a Secchi disc varied from 18 m (Lake Taupo) to 0.8 m (Lake Rotongaio). The transparency of the water in the glacial and volcanic lakes was comparable to that of similar lakes in other parts of the world. It was found that total ions, measured by the ion‐exchange resins reached high concentrations in lakes fed by thermal waters: Rotomahana 14.32m.e./l. By contrast Tikitapu, a seepage lake, had the low concentration of. 0.28m.e./l, and Wakatipu, a glacial fed lake, a concentration of O.58m.e./1. The pH range was 8.1–5.8, the lowest value being in Tikitapu, a volcanic lake. Slightly lower pH values were recorded in the bottom waters of lakes when stratified. Lakes were usually supersaturated with oxygen at the surface, and only a few small lakes showed a hypolimnial deficiency. Silica and phosphate were found in high concentrations in some thermal lakes but nitrogen in the forms measured, was found to be low. 相似文献
27.
Benchmarking observational uncertainties for hydrology: rainfall,river discharge and water quality 总被引:2,自引:0,他引:2
This review and commentary sets out the need for authoritative and concise information on the expected error distributions and magnitudes in observational data. We discuss the necessary components of a benchmark of dominant data uncertainties and the recent developments in hydrology which increase the need for such guidance. We initiate the creation of a catalogue of accessible information on characteristics of data uncertainty for the key hydrological variables of rainfall, river discharge and water quality (suspended solids, phosphorus and nitrogen). This includes demonstration of how uncertainties can be quantified, summarizing current knowledge and the standard quantitative results available. In particular, synthesis of results from multiple studies allows conclusions to be drawn on factors which control the magnitude of data uncertainty and hence improves provision of prior guidance on those uncertainties. Rainfall uncertainties were found to be driven by spatial scale, whereas river discharge uncertainty was dominated by flow condition and gauging method. Water quality variables presented a more complex picture with many component errors. For all variables, it was easy to find examples where relative error magnitudes exceeded 40%. We consider how data uncertainties impact on the interpretation of catchment dynamics, model regionalization and model evaluation. In closing the review, we make recommendations for future research priorities in quantifying data uncertainty and highlight the need for an improved ‘culture of engagement’ with observational uncertainties. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
28.
Hilary McMillan Alberto Montanari Christophe Cudennec Hubert Savenije Heidi Kreibich Tobias Krueger 《水文科学杂志》2013,58(7):1174-1191
ABSTRACTIn 2013, the International Association of Hydrological Sciences (IAHS) launched the hydrological decade 2013–2022 with the theme “Panta Rhei: Change in Hydrology and Society”. The decade recognizes the urgency of hydrological research to understand and predict the interactions of society and water, to support sustainable water resource use under changing climatic and environmental conditions. This paper reports on the first Panta Rhei biennium 2013–2015, providing a comprehensive resource that describes the scope and direction of Panta Rhei. We bring together the knowledge of all the Panta Rhei working groups, to summarize the most pressing research questions and how the hydrological community is progressing towards those goals. We draw out interconnections between different strands of research, and reflect on the need to take a global view on hydrology in the current era of human impacts and environmental change. Finally, we look back to the six driving science questions identified at the outset of Panta Rhei, to quantify progress towards those aims.
Editor D. Koutsoyiannis; Associate editor not assigned 相似文献
29.
Hilary A. Dugan Tom Gleeson Scott F. Lamoureux Kent Novakowski 《Environmental Earth Sciences》2012,66(5):1385-1392
In the High Arctic, groundwater fluxes are limited by the presence of continuous permafrost, although it has been hypothesized that there may be localized groundwater flow and hydraulic connectivity beneath large lakes, due to the presence of taliks, or large regions of unfrozen ground. However, due to the logistical difficulty of employing seepage meters and piezometers in deep, ice-covered lakes, relatively little is known about groundwater discharge to polar lakes. One method of assessing groundwater discharge is through the use of geochemical tracers. We conducted a pilot study to quantify groundwater discharge into a High Arctic lake using dissolved radon gas as a geochemical tracer. Lake water was collected in 15 L polyvinyl chloride (PVC) bags with minimal atmospheric interaction from a 25-m deep lake near Shellabear Point, Melville Island, Northwest Territories, Canada. Sample bags were aerated through a closed water loop for 60 min to allow sufficient radon to equilibrate in a coupled air circuit. Radon in air concentrations were measured on a Durridge RAD7 portable alpha spectrometer. The field trial in a remote setting and separate tests with groundwater samples collected from a temperate site demonstrate the utility of the methodology. The limited results suggest that radon levels in the lower water column are elevated above background levels following nival melt in the surrounding watershed. Although these results are insufficient to quantify groundwater discharge, the results suggest subsurface flow may exist, and further study is warranted. 相似文献
30.
Aquatic macrophyte vegetation development in Kråkenes Lake, western Norway, during the late-glacial and early-Holocene 总被引:1,自引:0,他引:1
Hilary H. Birks 《Journal of Paleolimnology》2000,23(1):7-19
Macrofossil analyses were carried out on the late-glacial and early-Holocene sediments of the radiocarbon-dated master core at Kråkenes Lake, western Norway, to investigate the aquatic vegetation changes. Ranunculus sect. Batrachium and Nitella were the earliest pioneers after deglaciation ca. 12,300 14C yr BP. The Allerød vegetational succession was very slow during ca. 1000 14C yrs in a cool climate and conditions that were similar to those above tree-line in Norway today. The rapid cooling at the start of the Younger Dryas stadial caused extensive disturbance, and with the development of an active cirque glacier in the catchment, plants and animals were almost exterminated from the lake by inflow of permanently cold and turbid water. Rising temperatures caused the glacier to melt at the end of the Younger Dryas. The biotic response to the rapid warming was immediate, with pioneer Ranunculus sect. Batrachium and Nitella expanding within 1-3 decades, closely followed by other elodeids. The lake witnessed a remarkable isoetid succession, with phases dominated by Limosella aquatica, Subularia aquatica, Elatine hydropiper, Isoetes echinospora, and, later, I. lacustris. About 800 yrs into the Holocene most of the macrophytes declined. The short-lived isoetids became extinct, but other taxa probably survived vegetatively. The reasons for this decline are unknown, but are probably related to nutrient depletion in combination with other factors. About 550 yrs later, I. lacustris and Nymphaea colonised, and a stable flora and vegetation developed. This study illustrates the large and rapid changes that occurred over the first 1400 yrs of the Holocene in the macrophyte flora and vegetation in Kråkenes Lake before stability was attained, pointing to the value of a palaeoecological study in tracing aquatic successions over time, and highlighting our lack of knowledge of the underlying ecological factors responsible for such rapid and marked changes. 相似文献