秘鲁西北部早白垩世Oyotún组火山岩层序、年代学及地球化学特征——对古Farallon板块俯冲作用细节的揭示

Oyotún组火山岩为中安第斯西北缘中生代出露范围最广的一套火山岩,对研究中安第斯早白垩世壳幔相互作用具有重要意义。研究区西部Oyotún组火山岩出露面积小,厚度薄,岩性单一,而东部出露范围大,厚度厚,岩性复杂。LA-ICP-MS锆石U-Pb定年表明,Oyotún组火山岩时代集中在139.7~131.0Ma之间。主量元素SiO_2含量介于54.44%~72.33%之间,中等富MgO(0.56%~1.55%),偏铝-强过铝,A/CNK=0.98~3.51,富集Cs、Rb、Th、U、Pb和轻稀土元素,无明显Eu异常,亏损Nb、Ta、Ti、P等,具明显的火山弧特征。Oyotún组火山岩εHf(t)值在3.37~8.42之间,且底部εHf(t)值显著低于顶部,指示其可能形成于活动陆缘弧后伸展背景下,由亏损地幔衍生的新生玄武质下地壳,经板片流体作用而产生的低程度部分熔融过程,并受到太古宙古老陆壳物质的混染,其混染程度随时代变新而逐渐减小。     

Assessment of potential sediment contamination using screening methods (XRF,TGA/MS) taking into account principles of green chemistry,Eastern Slovakia

Mining and milling of metal ores coupled with industries have bequeathed many countries the legacy of wide distribution of metal contaminants in sediments. The aim of this study was to assess potential sediment contamination via useful screening methods (XRF, CHNS, TGA/MS). The sediments were collected from the water reservoir Krompachy Eastern Slovakia in April 2015. Within the frame of evaluation it was found that the concentrations of the study elements (Cu, Zn, As, Pb, Cr, Ni, Cd) exceeded some of the MPC, TV and IV values. Sample c was the most polluted by metals, which evident according to it’s the highest CHNS proportion as well as the highest clay and silt proportion. In the samples studied the best correlation was confirmed between weight losses in the temperature range (400–620 °C) and the following metal concentrations: Cu (r = 0.89), Zn (r = 0.88), As (r = 0.93), Hg (r = 0.83), Pb (r = 0.87). The greatest proportions of m/z 44, m/z 18 were detected at temperatures (400–620 °C) associated with decomposition of minerals such as siderite, barite, and exothermic loss of more refractory aromatic C took also place.     

Soil compaction under different management practices in a Croatian vineyard

The use of machinery in vineyards is increasing soil compaction and erosion. However, there is a lack of information about the impacts of different management practices on soil conditions of vineyards. Therefore, the aim of this study was to assess soil compaction in Croatian vineyards under four different management systems: no-tillage (NT) system, conventional tillage (CT), yearly inversed grass covered (INV-GC) and tillage managed (INV-T) treatments. Four key top-soil (0–20 cm) parameters were assessed in the different land uses: bulk density (BD), penetration resistance (PR), soil water content (SWC) and carbon dioxide (CO₂) fluxes. Tractor traffic increased the BD and PR in all treatments, with exception of CT treatment, as consequence of tillage. SWC showed higher values in INV-GC treatment during the dry period; meanwhile, it was similar during the wet season in every management type. Lower CO₂ fluxes were found in INV-GC and NT than in the CT and INV-T treatments.     

Osmium isotope and highly siderophile element systematics of the lunar crust

Coupled ¹⁸⁷Os/¹⁸⁸Os and highly siderophile element (HSE: Os, Ir, Ru, Pt, Pd, and Re) abundance data are reported for pristine lunar crustal rocks 60025, 62255, 65315 (ferroan anorthosites, FAN) and 76535, 78235, 77215 and a norite clast in 15455 (magnesian-suite rocks, MGS). Osmium isotopes permit more refined discrimination than previously possible of samples that have been contaminated by meteoritic additions and the new results show that some rocks, previously identified as pristine, contain meteorite-derived HSE. Low HSE abundances in FAN and MGS rocks are consistent with derivation from a strongly HSE-depleted lunar mantle. At the time of formation, the lunar floatation crust, represented by FAN, had 1.4 ± 0.3 pg g^? 1 Os, 1.5 ± 0.6 pg g^? 1 Ir, 6.8 ± 2.7 pg g^? 1 Ru, 16 ± 15 pg g^? 1 Pt, 33 ± 30 pg g^? 1 Pd and 0.29 ± 0.10 pg g^? 1 Re (～ 0.00002 × CI) and Re/Os ratios that were modestly elevated (¹⁸⁷Re/¹⁸⁸Os = 0.6 to 1.7) relative to CI chondrites. MGS samples are, on average, characterised by more elevated HSE abundances (～ 0.00007 × CI) compared with FAN. This either reflects contrasting mantle-source HSE characteristics of FAN and MGS rocks, or different mantle–crust HSE fractionation behaviour during production of these lithologies. Previous studies of lunar impact-melt rocks have identified possible elevated Ru and Pd in lunar crustal target rocks. The new results provide no supporting evidence for such enrichments.If maximum estimates for HSE in the lunar mantle are compared with FAN and MGS averages, crust–mantle concentration ratios (D-values) must be ≤ 0.3. Such D-values are broadly similar to those estimated for partitioning between the terrestrial crust and upper mantle, with the notable exception of Re. Given the presumably completely different mode of origin for the primary lunar floatation crust and tertiary terrestrial continental crust, the potential similarities in crust–mantle HSE partitioning for the Earth and Moon are somewhat surprising. Low HSE abundances in the lunar crust, coupled with estimates of HSE concentrations in the lunar mantle implies there may be a ‘missing component’ of late-accreted materials (as much as 95%) to the Moon if the Earth/Moon mass-flux estimates are correct and terrestrial mantle HSE abundances were established by late accretion.     

Estimating sediment transport from acoustic measurements in the Venice Lagoon inlets

This paper presents the results of a 3-year-long (November 2004–November 2007) study based on the use of acoustic Doppler current profilers (ADCPs) to estimate the solid transport through the three inlets of Venice lagoon. In each of the three inlets instruments were mounted both on survey boats and deployed on the channel bed. The three bottom-mounted ADCPs were positioned in the central part of the inlets, continuously monitoring vertical profiles in the water column. Periodic transects along the investigated sections were collected by the boat-mounted ADCP. Both installations measured current speed and acoustic backscatter intensity. The latter expresses the attenuation of acoustic energy due to material in the water column.     

Moveout approximation for horizontal transversely isotropic and vertical transversely isotropic layered medium. Part II: effective model‡

We use residual moveouts measured along continuous full azimuth reflection angle gathers, in order to obtain effective horizontal transversely isotropic model parameters. The angle gathers are generated through a special angle domain imaging system, for a wide range of reflection angles and full range of phase velocity azimuths. The estimation of the effective model parameters is performed in two stages. First, the background horizontal transversely isotropic (HTI)/vertical transversely isotropic (VTI) layered model is used, along with the values of reflection angles, for converting the measured residual moveouts (or traveltime errors) into azimuthally dependent normal moveout (NMO) velocities. Then we apply a digital Fourier transform to convert the NMO velocities into azimuthal wavenumber domain, in order to obtain the effective HTI model parameters: vertical time, vertical compression velocity, Thomsen parameter delta and the azimuth of the medium axis of symmetry. The method also provides a reliability criterion of the HTI assumption. The criterion shows whether the medium possesses the HTI type of symmetry, or whether the azimuthal dependence of the residual traveltime indicates to a more complex azimuthal anisotropy. The effective model used in this approach is defined for a 1D structure with a set of HTI, VTI and isotropic layers (with at least one HTI layer). We describe and analyse the reduction of a multi‐layer structure into an equivalent effective HTI model. The equivalent model yields the same NMO velocity and the same offset azimuth on the Earth's surface as the original layered structure, for any azimuth of the phase velocity. The effective model approximates the kinematics of an HTI/VTI layered structure using only a few parameters. Under the hyperbolic approximation, the proposed effective model is exact.     

The effect of wind on the residual current velocities in the inlets of Venice lagoon

The residual flow in the inlets of Venice lagoon subject to Bora and Sirocco winds has been studied. Current velocities have been monitored since 2001 using Acoustic Doppler Current Profilers (ADCP) installed on the beds of the inlets that connect the lagoon to the Adriatic Sea; these inlets are Lido, Malamocco and Chioggia. Wind velocity data have also been continuously measured at an oceanographic platform 14.8 km offshore from the lagoon; these data were subsequently decomposed into Principal Components, which are associated with Bora and Sirocco wind directions. Analyses show that the inflow in Lido inlet is strongly related to the Bora wind. The outflow in Chioggia inlet occurs during Bora events but shows a slightly weaker correlation with the wind speed, while Malamocco inlet shows little or no influence of Bora winds on flow patterns. A net residual inflow through Lido and Malamocco inlet was found, while outflow prevails in Chioggia inlet. During Bora events, the average residual inflow increased three-fold in Lido inlet, whereas the outflow in Chioggia inlet doubled. The current velocities in Lido and Chioggia inlets are best described by an exponential function of wind velocity with exponents of −0.1187 and −0.0924, respectively. The response to Sirocco events was evident mainly in Chioggia inlet. Specifically, there was a slow down of the outflow in linear proportion to wind speed. In excess of 10 m/s a complete current reversal was observed. Lido and Malamocco inlets showed little or no response to Sirocco winds, except during rare cases when wind speeds exceeded 15 m/s.     

An analytical model of a deformable cantilever structure rocking on a rigid surface: development and verification

This paper extends previously developed models to account for the influence of the column and the foundation masses on the behavior of top‐heavy deformable elastic cantilever columns rocking on a rigid support surface. Several models for energy dissipation at impact are examined and compared. A novel Vertical Velocity Energy Loss model is introduced. Rocking uplift and overturning spectra for the deformable elastic cantilever model excited by sinusoidal ground motions are constructed. The effects of non‐dimensional model parameter variations on the rocking spectra and the overturning stability of the model are presented. It is shown that the remarkable overturning stability of dynamically excited large cantilever columns is not jeopardized by their deformability. Copyright © 2015 John Wiley & Sons, Ltd.     

An analytical model of a deformable cantilever structure rocking on a rigid surface: experimental validation

This paper describes an experimental program to examine the dynamic response of deformable cantilevers rocking on a rigid surface. The primary goal of the tests is to verify and validate a dynamic rocking model that describes the behavior of these structures. The benchmark response data was obtained from shaking‐table tests on deformable rocking specimens with different natural vibration frequencies and different aspect ratios excited by analytical pulses and recorded ground motions. The responses computed using the model are found to be in good agreement with the benchmark test results. Widely used impact, restitution and damping assumptions are revisited based on the experiment results and the analytical model findings. Copyright © 2015 John Wiley & Sons, Ltd.