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111.
Marian Munteanu Allan H. Wilson Yong Yao Gordon Chunnett Yaonan Luo 《Mineralium Deposita》2010,45(6):517-529
The Lengshuiqing area contains several small intrusions made up of peridotite ± quartz diorite ± granite spatially associated
with the Gaojiacun pluton (gabbroids + peridotite + diorite). Ni–Cu sulfide ore occur at Lengshuiqing, hosted in peridotite.
SHRIMP U–Pb zircon dating produced the ages of 803 ± 4.2 Ma (peridotite), 807 ± 2.6 Ma (oikocrystic hornblende gabbro), 809 ± 4.3 Ma
(hornblende gabbronorites) for the Gaojiacun pluton and 807 ± 3.8 Ma (diorite, intrusion I), 817 ± 6.3 Ma (quartz diorite,
intrusion II) and 817 ± 5 Ma (peridotite, intrusion 101) for Lengshuiqing. These ages suggest the emplacement of the Gaojiacun
pluton later than the intrusions from Lengshuiqing. The olivine from Lengshuiqing does not contain sulfide inclusions and
is relatively Ni-rich (1,150–1,550 ppm Ni), suggesting its crystallisation before the sulfide saturation that generated the
Ni–Cu deposits. The olivine of the gabbros in the Gaojiacun pluton is Ni-poor (250–800 ppm), which indicates crystallisation
from a severely metal-depleted magma after a sulfide saturation event. The olivine in the peridotites from the Gaojiacun pluton
has 800–1,150 ppm Ni and contains sulfide inclusions. Moreover, geological evidence suggests the genesis of the peridotites
from Gaojiacun in conduits that were ascending through the gabbroids. A sequence of at least three stages of magma emplacement
is proposed: (1) Lengshuiqing; (2) gabbroids from Gaojiacun; (3) peridotites from Gaojiacun. Given the age differences, the
intrusions at Lengshuiqing and the Gaojiacun pluton might have been produced by different magmatic events. 相似文献
112.
Lucien von Gunten Christian Kamenik Marian Fujak Roberto Urrutia 《Journal of Paleolimnology》2012,47(4):583-600
Lake sediment records are underrepresented in comprehensive, quantitative, high-resolution (sub-decadal), multi-proxy climate
reconstructions for the past millennium. This is largely a consequence of the difficulty of calibrating biogeochemical lake
sediment proxies to meteorological time series (calibration-in-time). Thanks to recent methodological advances, it is now
possible. This paper outlines a step-by-step, specifically tailored methodology, with practical suggestions for calibrating
and validating biogeochemical proxies from lake sediments to meteorological data. This approach includes: (1) regional climate
data; (2) site selection; (3) coring and core selection; (4) core chronology; (5) data acquisition; and (6) data analysis
and statistical methods. We present three case studies that used non-varved lake sediments from remote areas in the Central
Chilean Andes, where little a priori information was available on the local climate and lakes, or their responses to climate
variability. These case studies illustrate the potential value and application of a calibration-in-time approach to non-varved
lake sediments for developing quantitative, high-resolution climate reconstructions. 相似文献
113.
The scientific and operational aims of the Czech-made Hard X-Ray Spectrometer (HXRS) launched onboard the U.S. Department
of Energy Multispectral Thermal Imager satellite (MTI), on 12 March 2000 are discussed. The principal operating characteristics
of the instrument such as the temporal resolution, energy band selection, spectral sensitivity, and the in-flight calibration
procedure are described as well as the technical details of the spectrometer including detectors, shielding (against charged
particles) and electronic design. The MTI host satellite and its orbit are briefly described. Recent observations by the 3 GHz
Ondřejov radiometer are compared with HXRS data to demonstrate one example of the HXRS data utilization: the temporal relation
between hard X-rays and radio emission. These results show relatively long time delays (2–14 s) of the GHz broadband radio
pulses relative to the hard X-ray emission peaks. Access to the HXRS data base via the Internet is provided. 相似文献
114.
Marian J. Furst 《Geochimica et cosmochimica acta》1981,45(1):1-13
The 10B(n, α)7Li nuclear reaction has been used with alpha-sensitive plastic track detectors to determine boron concentrations in siliceous live-collected and fossil sponge spicules. This radiographic technique allows B determinations with 5–6% uncertainties on objects 20–25 μm in diameter and for concentrations as low as 0.5 ppm. Boron concentrations in spicules from different specimens from the same location agreed to within 10% when the spicules were not: (1) smaller than 20 μm in diameter, (2) from dictyonine skeletons, (3) the extremely large root-like spicules found in some soft substrate hexactinellids, or (4) microscleres. These criteria also applied to spicules found in sediment samples. Spicules from live-collected sponges exhibited a taxonomy-independent correlation of B concentrations with water salinity for samples from regions of low water temperature and high productivity. Measured concentrations ranged from nearly 0 ppm B (freshwater sponges) to 500–700 ppm (marine sponges), with intermediate values for brackish-water specimens. However, spicules from tropical, low-productivity marine locations contained markedly less boron than spicules from temperate, high-productivity regions. Thus, water temperature and/or food supply also seem to influence B concentrations. Pleistocene spicules from deep-sea cores contained less boron than was expected in comparison with live-collected spicules based on present water temperatures and nutrient supplies, but B concentrations did not vary with depth in the cores. Infrared spectroscopy, electron microprobe analysis and visual inspection revealed no evidence for chemical or mineralogic alteration. It is not clear whether the lower B concentrations of the Pleistocene samples are the result of diagenetic processes or the as yet undefined effects of differences in food supply and/or environmental conditions. 相似文献
115.
116.
117.
Marian Klasztorny 《地震工程与结构动力学》1995,24(8):1155-1172
In the paper the problem of reduction of the steady-state response of a lightly damped structure to periodic excitation is considered. The primary structure, which has arbitrary distributions of mass, stiffness and damping, is subjected to periodic load with the fundamental frequency varying in a wide range that may include several resonant peaks of the amplitude-frequency response. A number of passive absorbers are applied simultaneously to the main structure. A general formulation of the dynamic absorber design methodology is presented, based on independent design of conventional absorbers, taking into account the selected modal systems of the original structure and the selected harmonic components of the excitation. In order to cover the losses in the vibration reduction, resulting from the couplings in the primary structure–the set of absorbers system and from the remaining harmonic components of the excitation, the mass of modal dynamic absorbers is increased properly. The methodology developed was verified on several numerical examples; one of them is presented in the study. 相似文献
118.
A time series analysis of a pulsation event in solar radio emission provides an evolution from a regular doubly periodic phase to an irregular behaviour. Applying some techniques developed in the theory of nonlinear dynamic systems to this irregular stage suggests that there exists a low-dimensional attractor. Estimates of the maximum Lyapunov exponent give some evidence to deterministic chaos. The sudden transition from a regular to a chaotic structure is identified as a part of the Ruelle-Takens-Newhouse route to chaos which is typical in nonlinear systems. It is checked whether this pulsation event may be interpreted in terms of known pulsation models. Consequences for models, which are suitable to describe such an evolution, are discussed. 相似文献
119.
For radio emission at the frequency corresponding to the second harmonic of the local plasma frequency, the optical thickness in the solar atmosphere is calculated. Three types of models are assumed: the model with radio emission from the narrow transition region, and models with radio emission from a cool and dense plasma filament embedded in hotter plasma at the transition region and in the corona. The optical thickness is computed by integration of the collisional (free–free) absorption along a radio-ray path radial in the solar atmosphere. In all models considered the optical thickness can be sufficiently low for appropriate parameters. For example, in the narrow (<100 km) transition region where the density scale height is much less than that of the pressure one, the optical thickness can be lower than 1. Furthermore, the optical thickness can be decreased if the radio emission is generated in the cool and dense plasma filament surrounded by hotter and thinner plasma. But the models differ in density scale heights and thus in distances between plasma emission levels. This difference is essential for the interpretation of high-frequency type III radio bursts. 相似文献
120.
During March 20, 1993, from 12:00 to 16:00 UT, repeated radio burst activity was observed in the 0.8–1.2 GHz frequency range. Periods in intervals 0.1–0.5, 0.7–1.0, 2.8–3.9, 75–170 s, and 15–25 min were recognized. This long-lasting narrowband activity consisted mainly of pulsations and continua. In some intervals it was accompanied not only by spikes, broadband pulsations, and fibers in the 1–2 GHz frequency range, but also by type III and U burst activity at lower frequencies as well as by hard X-ray bursts. From several radio bursts, two characterized by different fine structures were selected and compared. The observed differences are explained by different distribution functions of superthermal electrons. The position of the 0.8–1.2 GHz radio source above the photosphere and the magnetic field in the fiber burst source were estimated to be 66 000–75 000 km and 120–135 G, respectively.Presented at te CESRA-Workshop on Coronal Magnetic Energy Release at Caputh near Potsdam in May 1994. 相似文献