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271.
Cabral Alexandre Raphael Ließmann Wilfried Jian Wei Lehmann Bernd 《International Journal of Earth Sciences》2017,106(7):2359-2369
International Journal of Earth Sciences - Carbonate veinlets at Roter Bär, a former underground mine in the polymetallic St. Andreasberg vein district of the Harz Mountains, Germany, host... 相似文献
272.
<正>The Ailao Shan-Red River fault zone is the boundary between the Yangtze block to the northeast and the Indochina block to the southwest.It is an important tectonic zone due to its role in the southeastward extrusion of the Indochina block during and subsequent to the Indian-Eurasian collision.Diancang Shan(DCS) high-grade metamorphic complex,located at the northwest extension along the Ailao Shan-Red River(ASRR) shear zone,is a representative metamorphic complex of the ASRR tectonic belt.Structural and microstructural analysis of sheared rocks in the high-grade metamorphic rocks reveals that they are coherent with solid-state high-temperature ductile deformation,which is attributed to left-lateral shearing along the ASRR shear zone.New LA-ICP-MS zircon U-Pb geochronological and microstructural studies of the post-kinematic granitic plutons provide a straightforward time constraint on the termination ductile left-lateral shearing and exhumation of the metamorphic massif in the ASRR shear zone.It is suggested that the left-lateral shearing along the ASRR shear zone ended at ca.21 Ma at relative lower-temperature or decreasing temperature conditions.During or after the emplacement of the young dikes at ca.21 Ma,rapid brittle deformation event occurred,which makes the DCS massif start fast uplift/exhumation and cooling to a shallow crustal level. 相似文献
273.
274.
Diesel transport monitoring in simulated unconfined aquifers using miniature resistivity arrays 总被引:2,自引:0,他引:2
The principal aim of this study is to assess the scope of monitoring diesel plume migration in a scaled aquifer model with
a miniaturised electrical resistivity array. Respectively 1000 and 500 ml of diesel were injected in both the unsaturated
and water-saturated zones of a sand body overlying a clay aquitard, and diesel migration was monitored with a miniature electrode
array and an off-the-shelf resistivity meter. Inverted time-lapse electrical resistivity tomography (ERT) data reflect downward
and lateral spreading of the diesel plume away from the injection point in the unsaturated zone. Diesel was also imaged to
spread upwards and laterally away from the injection point in the saturated zone, as controlled by capillary rise. In both
cases later-time ERT images reflected preferential pooling of diesel on the water table, as well as vertical smearing of pooled
diesel in response to simulated water-table fluctuations. Repeat fluid electrical conductivity (EC) and dissolved oxygen (DO)
measurements validate the observed changes in bulk resistivity caused by both diesel injections. Artefacts introduced by 2D
inversion of 3D contaminant transport were abound. Time-lapse ERT imaging of diesel transport is therefore inferred to be
feasible and well-suited to complementing conventional techniques of intrusive site investigation, although time-lapse 3D
or 4D ERT imaging is strongly advocated. 相似文献
275.
Jiabin Zhou Tieguan Wang Yanping Zhang Ningning Zhong Patricia M. Medeiros Bernd R.T. Simoneit 《Atmospheric Research》2009,93(4):849-861
The solvent-extractable organic compounds of atmospheric PM10 samples, collected over two years beginning in 2003 at urban and suburban sites of Beijing, were characterized using gas chromatography–mass spectrometry (GC–MS). The elemental carbon (EC) contents were determined and ranged from 4.3 to 42 μg m− 3. Organic compounds in total extracts were identified and included unresolved complex mixture (UCM) and series of n-alkanes, n-alkanols, n-alkanoic acids, polycyclic aromatic hydrocarbons (PAHs); saccharides, alkanedioic acids, steroids, and other biomarkers and source tracers. The seasonal variations of their relative abundances are discussed. The abundance order for the major molecular classes in the particulate organic matter (POM) was the following: UCM > saccharides > n-alkanoic acids >n-alkanes > n-alkanols > PAHs > hydroxy-PAHs > other biomarker tracers. Based on the genetic significance of the molecular tracers, the dominant sources of POM are proposed for the two sampling sites. The emissions from fossil fuel use (both coal and petroleum products), biomass combustion, other pyrolysis sources, higher plant wax, and secondary products contribute > 98.0% of the POM mass. The fossil fuel use (average = 65% of POM) is the largest contributor and derives mainly from vehicular traffic. 相似文献
276.
277.
Temperature-dependent isotopic fractionation of lithium between clinopyroxene and high-pressure hydrous fluids 总被引:2,自引:1,他引:2
Bernd Wunder Anette Meixner Rolf L. Romer Wilhelm Heinrich 《Contributions to Mineralogy and Petrology》2006,151(1):112-120
The fractionation of lithium isotopes between synthetic spodumene as representative of Li-bearing clinopyroxene and Cl- and
OH-bearing aqueous fluids was experimentally determined between 500 and 900°C at 2.0 GPa. In all the experiments, 7Li was preferentially partitioned into the fluid. The fractionation is temperature dependent and approximated by the equation
Δ7Li(clinopyroxene–fluid)=−4.61×(1,000/T [K]) + 2.48; R
2=0.86. Significant Li isotopic fractionation of about 1.0‰ exists even at high temperatures of 900°C. Using neutral and weakly
basic fluids revealed that the amount of fractionation is not different. The Li isotopic fractionation between altered basalt
and hot spring water (350°C) in natural samples is in good agreement with our experimentally determined fractionation curve.
The data confirm earlier speculations drawn from the Li isotopic record of dehydrated metamorphic rocks that fluids expelled
from a dehydrating slab carry heavier Li into the mantle wedge, and that a light Li component is introduced into the deeper
mantle. Li and Li isotopes are redistributed among wedge minerals as fluids travel across the wedge into hotter regions of
arc magma production. This modifies the Li isotopic characteristics of slab-derived fluids erasing their source memory, and
explains the absence of cross-arc variations of Li isotopes in arc basalts. 相似文献
278.
279.
Jingwen Mao Yitian Wang Bernd Lehmann Jinjie Yu Andao Du Yanxiong Mei Yongfeng Li Wenshuan Zang Holly J. Stein Taofa Zhou 《Ore Geology Reviews》2006,29(3-4):307-324
The area of the Middle–Lower Yangtze River valley, Eastern China, extending from Wuhan (Hubei province) to western Zhenjiang (Jiangsu province), hosts an important belt of Cu–Au–Mo and Fe deposits. There are two styles of mineralization, i.e., skarn/porphyry/stratabound Cu–Au–Mo–(Fe) deposits and magnetite porphyry deposits in several NNE-trending Cretaceous fault-bound volcanic basins. The origin of both deposit systems is much debated. We dated 11 molybdenite samples from five skarn/porphyry Cu–Au–Mo deposits and 5 molybdenite samples from the Datuanshan stratabound Cu–Au–Mo deposit by ICP-MS Re–Os isotope analysis. Nine samples from the same set were additionally analyzed by NTIMS on Re–Os. Results from the two methods are almost identical. The Re–Os model ages of 16 molybdenite samples range from 134.7 ± 2.3 to 143.7 ± 1.6 Ma (2σ). The model ages of the five samples from the Datuanshan stratabound deposit vary from 138.0 ± 3.2 to 140.8 ± 2.0 Ma, with a mean of 139.3 ± 2.6 Ma; their isochron age is 139.1 ± 2.7 Ma with an initial Os ratio of 0.7 ± 8.1 (MSWD = 0.29). These data indicate that the porphyry/skarn systems and the stratabound deposits have the same age and suggest an origin within the same metallogenic system. Albite 40Ar/39Ar dating of the magnetite porphyry deposits indicates that they formed at 123 to 125 Ma, i.e., 10–20 Ma later. Both mineralization styles characterize transitional geodynamic regimes, i.e., the period around 140 Ma when the main NS-trending compressional regime changed to an EW-trending lithospheric extensional regime, and the period of 125–115 Ma of dramatic EW-trending lithospheric extension. 相似文献
280.
European whitefish (Coregonus lavaretus) is a dominant zooplanktivorous fish in many praealpine lakes and of great commercial interest. Estimation of prey consumed by European whitefish is essential for the prediction of top down effects in the pelagic zone. Whitefish is known to feed selectively on cladocerans. Quantitative estimates of prey consumed by whitefish are often not easy to get because stomachs frequently contain only degraded fragments of already digested prey. In this study stomach contents of European whitefish which were composed of digested, degraded prey were analyzed. Daphnid prey could be quantified by the number of mandibles divided by two, the number of head capsules and abdomina present. Predatory cladocerans could be quantified by the number of mandibles divided by two and the number of tail appendages present. For stomachs which contained heavily digested fragments counting the mandibles proved to be a useful and sometimes the only applicable means to quantify prey items. Other body parts, like structured legs which were broken into many pieces, were unsuited to quantify prey items. 相似文献