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1.
Oxygen and strontium isotope ratios have been used to characterize source regions for granitic magmas for a transect across the northern Appalachian orogen in central and eastern Maine. The northwestern plutons (Katahdin and Seboeis) have δ18O values of 10.3–13.3 and initial 87Sr/86Sr ratios of 0.7083 and 0.7066, respectively. The central plutons (Bottle Lake and Center Pond) have lower δ18O values (8.2–9.9) and initial 87Sr/86Sr ratios (0.7043–0.7055). The southeastern plutons (Lucerne and Deblois) have δ18O values (9.0–11.0) but initial 87Sr/86Sr ratios (0.7077 and 0.7041, respectively) which are intermediate between the northwestern and central plutons.Source models derived from these results and other petrological and geochemical data reflect the juxtaposition of discrete source regions by transcurrent faulting, which may be related to oblique plate motions. This model illustrates the importance of microplate accretion in the Palaeozoic history of the northern Appalachian orogen. 相似文献
2.
Janaína N. vila Trevor R. Ireland Peter Holden Peter Lanc Andrew Latimore Norm Schram John Foster Ian S. Williams Liane Loiselle Bin Fu 《Geostandards and Geoanalytical Research》2020,44(1):85-102
Analytical protocols for SHRIMP‐SI oxygen isotope analysis (δ18O) of a suite of zircon reference materials (RMs) are presented. Data reduction involved a robust estimate of uncertainties associated with the individual spot as well as for groups where the spot data are combined. The repeatability of δ18O measurements is dependent on both the analytical conditions and the choice of the primary reference material. Under optimised conditions, repeatability was often better than 0.4‰ (2s) allowing sample uncertainties to be obtained to better than 0.2‰ (at 95% confidence limit). Single spot uncertainty combined the within‐spot precision with the scatter associated with repeated measurements of the primary zircon reference material during a measurement session. The uncertainty for individual spots measured under optimised conditions was between 0.3 and 0.4‰ (at 95% confidence). The analytical protocols described were used to assess a variety of zircon RMs that have been used for geochronology and for which laser fluorination oxygen isotope data are available (Temora 2, FC1, R33, QGNG and Ple?ovice), as well as zircons that have been used as RMs for trace element or other types of determination (Mud Tank, Monastery, 91500, AS57, AS3, KIM‐5, OG1, SL13, CZ3 and several other Sri Lankan zircons). Repeated analyses over nine sessions and seven different mounts show agreement within analytical uncertainty for Temora 2, FC1, R33, QGNG, Ple?ovice and 91500, when normalised to Mud Tank. For existing ion microprobe mounts with these materials, an appropriate δ18O can be determined. However, care should be taken when using zircons from the Duluth Complex (i.e., FC1, AS57 and AS3) as reference materials as our data indicated an excess scatter on δ18O values associated with low‐U zircon grains. 相似文献
3.
Luca Bracchini Antonio Tognazzi Arduino Massimo Dattilo Franco Decembrini Claudio Rossi Steven Arthur Loiselle 《Aquatic Sciences - Research Across Boundaries》2010,72(4):485-498
In the past two decades, optical properties of chromophoric dissolved organic matter (CDOM) in marine environments have been
extensively studied. Many of these studies report CDOM properties for the offshore environment where this complex mixture
of optically active compounds is strongly diluted. Nevertheless, autochthonous and allochthonous sources have been identified
and sinks related to photodegradation and bacterial activity have been demonstrated. The calculation of the spectral slope
of the CDOM absorption curve has been proven to be useful and is often reported. However, a rigorous uncertainty analysis
of the slope calculation is rarely reported. In this paper, we propose a method to evaluate the uncertainty of CDOM spectral
slope calculated between 270 and 400 nm, using both naturally sampled and artificial solutions. We use these results to study
the ultra-oligotrophic waters of the Mediterranean Sea (central eastern basin), where little is known about CDOM spatial distribution.
We show that dilutions of both artificial and natural samples produce a Gaussian distribution of spectral slopes, indicating
that consistent values may be determined, with a typical uncertainty of ±0.0004 nm−1 when absorption at 300 nm was greater then 0.1 m−1 (0.1 m pathlength). Comparing the distribution of spectral slopes from central eastern basin samples to a Gaussian distribution,
we show differences between measurements that were significantly different. These values allow us to distinguish possible
sources (algal derived CDOM), sinks (e.g. photo-bleaching) at different depths. We propose a subdivision of CDOM compounds
into refractory and semilabile/refractory pools and evaluate the CDOM spectral slope of algal derived CDOM released at or
near deep chlorophyll maximum. 相似文献
4.
NK Arkert A-R Childs MC Parkinson AC Winkler E Butler S Mannheim 《African Journal of Marine Science》2018,40(3):235-244
Fisheries managers are increasingly promoting catch-and-release (C&R) to manage recreationally angled fish stocks. Despite this, there is a scarcity of information on the effects of C&R on estuarine-dependent species. Cape stumpnose Rhabdosargus holubi dominates the recreational fisheries catch and provides an important source of food for subsistence fishers in some temperate South African estuaries. The health and survival of R. holubi exposed to a C&R event was investigated by examining their physiological stress response (blood glucose and lactate), reflex impairment (reflex action mortality predictors [RAMP]) and short-term (12-hour) survival. Fish were captured and exposed to one of three air-exposure treatments: 0 s, 30 s or 90 s. Stress and health were measured either immediately (immediate) or one hour after (delayed) the C&R event. There was no significant difference in blood glucose between air-exposure treatments, but there was a significant difference between the mean immediate and delayed glucose levels within each treatment (F(2,143) = 81.8, p < 0.01). In contrast, blood lactate level was significantly higher in the 90-s treatment (p < 0.05). Immediate blood lactate levels were significantly lower than the delayed samples for each treatment (F = 4.29, p = 0.02; n = 169). Although all fish exhibited at least one reflex impairment, the RAMP score was significantly higher in the 90-s air-exposure treatment (H(2,86) = 9.73, p = 0.007). Also, RAMP scores were significantly lower in the delayed samples (p < 0.01). Although short-term mortality was relatively low (2.3%) for this species, it was highest in the 90-s treatment (7%). These results suggest that physiological stress is higher when R. holubi are exposed to longer periods of air exposure and that the physiological stress of fish subject to a C&R event is best measured after a delay. 相似文献
5.
Possibilities of soil spectroscopy for the classification of contaminated areas in river floodplains
Lammert Kooistra Ron Wehrens Lutgarde MC Buydens Rob S. E. W. Leuven Piet H Nienhuis 《International Journal of Applied Earth Observation and Geoinformation》2001,3(4):337
During the past decades, large amounts of diffuse contaminated soil material have been deposited in the floodplains of the river Rhine in the Netherlands. The dynamic character of this river causes a large spatial variability in the contamination level of its floodplain soils. Characterisation of the spatial variability exclusively based on soil sampling and analysis is often insufficient and expensive. Hyperspectral images can provide additional spatial information for a proper characterisation of the contamination situation of river floodplains. This paper describes the possible application of soil spectroscopy to estimate metal concentration levels in river floodplains. Soil reflectance spectra in the visible-near infrared region (VNIR) were measured in the laboratory for soil samples taken from two river floodplains along the river Waal, the main tributary of the river Rhine in the Netherlands. A multivariate calibration procedure using partial least squares (PLS) regression was applied to establish a relationship between reflectance spectra in the visible-near infrared (VNIR) region and spectrally active soil characteristics (organic matter and clay content) that are intercorrelated with concentration levels of Cd and Zn. Results of the analysis of two river floodplains are summarised and the influence of scale-level and sub soil material on the prediction capability is discussed. 相似文献
6.
MATTHIAS F. COMERFORD ROBERT H. MC CORKELL SAMUEL W. TISHLER 《Meteoritics & planetary science》1968,4(1):7-21
Abstract Examination of an iron meteorite found in South Africa discloses it to be a coarse octahedrite containing 6.90 weight-percent nickel. The meteorite body contains several inclusions of troilite, or troilite plus graphite, and at least one of pure graphite veined with kamacite. Kamacite, cohenite, and phosphides are the other major constituents of the structure. 相似文献
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8.
中国铂矿资源严重不足,主要分布在中国西部,根据原生矿床特征可划分为4类：①硫化物型;②铬铁矿型;③辉石岩型;④层控型。寻找铂矿新类型和富铂(岩石)资源,应成为解决中国铂矿资源紧缺的重要任务。铂矿找矿方向：地台与地槽接合部位,特别是围绕着基性、超基性岩内外接触带,铂的预富集岩带与层控型铂矿带,另外还有砂铂型铂矿发育区有望扩大找铂前景。 相似文献
9.
Stefania Mazzuoli Steven Loiselle Vincent Hull Luca Bracchini Claudio Rossi 《洁净——土壤、空气、水》2003,31(6):461-468
The spatial and temporal distribution of humic substances in aquatic ecosystems can have important effects on ecosystem productivity, negatively impacting primary productivity while positively impacting secondary productivity. In the present investigation, a large shallow lake ecosystem was studied to determine the spatial and seasonal variation of the composition and concentration of humic substances. Concentrations of total dissolved organic matter, humic acid, and fulvic acid were found to display significant spatial distributions (1.3…13.5 mg/L, DOM; 0.1…5.4 mg/L, HA). The distribution is described by using mapping techniques and the analysis of the spatial distribution of the lake. An analysis of the seasonal variations also indicated the dependence of the occurrence of these compounds on meteorological and hydrological conditions. To identify the potential sources of these organic materials, an analysis was made of the ratio of humic and fulvic acid fractions and total DOM. It was found that areas of high DOM concentration coincided with the areas of highest HA percentage of total DOM. Furthermore using the ratio of the normalised concentrations of HA, FA, and residual DOM (< 5000 g/mol) it was found that areas dominated by each are spatially distinct. This confirms the hypothesis that in these shallow lakes, photodegradation and bacterioplankton activity will create a residence time dependent zonation of each component of the total DOM. 相似文献
10.
Fracture Density Distributions and Well Yields in Coastal Maine 总被引：1，自引：0，他引：1
Understanding the distribution of water-bearing fractures in crystalline rock is an important component in evaluating the availability and vulnerability of water resources throughout the northeastern U.S. The State of Maine requests well drillers to report estimates of fracture depths and fracture yields for all bedrock wells drilled in the state. Using these data we analyze fracture-depth and fracture-yield data from 227 bedrock wells in coastal Maine in order to understand how fracture locations and yields are distributed with depth. Numerical simulations and statistical tests show that it is not possible to infer how fractures are distributed with depth: fracture depths are consistent with several distributions, including uniform fracture density with depth. In order to understand how fracture yield varies with depth, we group yield data into 50 foot depth intervals and compare distributions in each interval using nonparametric statistical tests. These tests show that the distribution of fracture yield in different depth intervals are statistically equivalent. These results imply that there is no empirical justification for limiting well depth when drilling for water resources in fractured bedrock in coastal Maine. 相似文献