The 2011 Tohoku-Oki earthquake's influence on the Asian plates and Korean geodetic network

本研究分析了2011年3月11日发生的Mw9.0日本东北地区太平洋近海地震对亚洲地区和韩国国内GPS卫星常年跟踪站的位移影响.为此,利用了日本东北地区太平洋近海地震发生前后两周(2011年3月4日到3月18日)的GPS站点数据,包括震中附近地区(韩国,中国,中国台湾地区,日本和俄罗斯)55个GPS卫星常年跟踪站和284个IGS全球跟踪站,并采用GAMIT/GL,OBK软件进行处理和平差,估算出所有GPS站点的同震形变.结果显示,日本东北地区太平洋近海地震引起的同震形变影响在亚洲地区比较明显,包括日本和附近国家,距离震中2702 km的中国武汉(WUHN)站也观测到同震形变.为精确分析日本东北地区太平洋近海地震对韩国国家大地控制网的影响.通过GAMIT/GLLOBK软件计算出韩国GPS卫星常年跟踪站之间的基线长度变形,并分析出弹性变形量.结果表明:大部分GPS站点均向震中方向膨胀,且向震中的垂直方向收缩,由日本东北地区太平洋近海地震导致的最大剪应变达到韩国国家大地控制网年均变形率的约7倍,对韩国的地壳产生14.5～57.7 mm的水平位移,并导致韩国国家大地控制网产生弹性变形,因此,在不及时更新维护韩国国家大地控制网的情况下,GPS测量成果将会发生最大20 mm的位置误差.     

XANES evidence for sulphur speciation in Mn-, Ni- and W-bearing silicate melts

S K-edge XANES and Mn-, W- and Ni-XANES and EXAFS spectra of silicate glasses synthesised at 1400 °C and 1 bar with compositions in the CaO-MgO-Al₂O₃-SiO₂-S plus MnO, NiO, or WO₃ systems were used to investigate sulphur speciation in silicate glasses.S K-edge spectra comprised a composite peak with an edge between 2470 and 2471.4 eV, which was attributed to S²⁻, and a peak of variable height with an edge at 2480.2-2480.8 eV, which is consistent with the presence of S⁶⁺. The latter peak was attributed to sample oxidation during sample storage. W-rich samples produced an additional lower energy peak at 2469.8 eV that is tentatively attributed to the existence of S 3p orbitals hybridised with the W 5d states.Deconvolution of the composite peak reveals that the composite peak for Mn-bearing samples fits well to a model that combines three Lorentzians at 2473.1, 2474.9 and 2476.2 eV with an arctan edge step. The composite peak for W-bearing samples fits well to the same combination plus an additional Lorentzian at 2469.8 eV. The ratio of the proportions of the signal accounted for by peaks at 2473.1 and 2476.2 eV correlates with Mn:Ca molar ratios, but not with W:Ca ratios. Spectra from Ni-bearing samples were qualitatively similar but S levels were too low to allow robust quantification of peak components. Some part of the signal accounted for by the 2473.1 eV peak was therefore taken to record the formation of Mn-S melt species, while the 2469.8 peak is interpreted to record the formation of W-S melt species. The 2474.9 and 2476.2 eV peaks were taken to be dominated by Ca-S and Mg-S interactions. However, a 1:1 relationship between peak components and specific energy transitions is not proposed. This interpretation is consistent with known features of the lower parts of the conduction band in monosulphide minerals and indicates a similarity between sulphur species in the melts and the monosulphides. S-XANES spectra cannot be reproduced by a combination of the spectra of the component element monosulphides.Mn-, W- and Ni-XANES and EXAFS for synthetic glasses without sulphide exsolution did not show any sensitivity to the presence of sulphur, which is unsurprising as S:O ratios were sufficiently low that metals would be mostly co-ordinated by O. Mn EXAFS spectra were consistent with divalent Mn in 5 co-ordinated Mn-O melt species. W spectra were consistent with tetrahedrally co-ordinated hexavalent W, most likely in scheelite-like melt species, and Ni spectra were consistent with [4] co-ordinated divalent Ni. These results indicate lower co-ordinations for both W and Ni than those inferred by some previous workers. Cation co-ordination may reflect the proportion of non-bridging oxygens, which is lower in the Ca-rich and Al-poor samples investigated here than for previous studies.     

Platelet development in cuboid diamonds: insights from micro-FTIR mapping

Fourier transform infrared mapping of diamonds can reveal detailed information on impurities, with a spatial context. We apply this technique, combined with in situ isotopic analysis of carbon, to the study of cuboid diamond growth in a sample that exhibits some mixed-habit growth. While there has been some uncertainty in the literature regarding sectoral differences in nitrogen aggregation and subsequent platelet development, the data from this study appear far more conclusive. We show that despite nitrogen being concentrated in octahedral sectors, there is no detectable difference in the concentration-adjusted rate of nitrogen aggregation within octahedral and cuboid sectors. However, the resultant platelet development is significantly reduced in cuboid sectors compared to contemporaneously formed octahedral sectors. This finding has significant implications for the classification of diamonds using the relationship between their platelet intensity and the absorption caused by B centres. It means that cuboid diamonds naturally fall below the linear relationship that has been termed regular, which would lead to them being incorrectly interpreted as having experienced heating or deformation. The data also support earlier suggestions that large hydrogen concentrations in the diamond-forming fluid may be required for cuboid growth. We further suggest that high nitrogen and hydrogen concentrations are required for mixed-habit diamond growth, which might be the product of specific fluid chemistries that occur in reducing mantle environments.     

Titanium solubility in olivine in the system TiO<Subscript>2</Subscript>–MgO–SiO<Subscript>2</Subscript>: no evidence for an ultra-deep origin of Ti-bearing olivine

The finding of ilmenite rods in olivine from orogenic peridotites has sparked a discussion about the processes of incorporation and exsolution of titanium in olivine. We have experimentally investigated the solubility of Ti in olivine as a function of composition, temperature and pressure in the synthetic TiO₂–MgO–SiO₂ system. Experiments at atmospheric pressure in the temperature range 1,200–1,500°C showed that the highest concentration of TiO₂ is obtained when olivine coexists with spinel (Mg₂TiO₄). The amount of TiO₂ in olivine in the assemblages olivine + spinel + periclase and olivine + spinel + ilmenite at 1,500°C was 1.25 wt.%. Changes in the coexisting phases and decreasing temperature result in a significant reduction of the Ti solubility. Olivine coexisting with pseudobrookite (MgTi₂O₅) and a Ti–Si-rich melt at 1,500°C displays a fourfold lower TiO₂ content than when buffered with spinel. A similar decrease in solubility is obtained by a decrease in temperature to 1,200°C. There is a negative correlation between Ti and Si and no correlation between Ti and Mg in Ti-bearing olivine. Together with the established phase relations this suggests that there is a direct substitution of Ti for Si at these temperatures, such that the substituting component has the stoichiometry Mg₂TiO₄. The unit cell volume of olivine increases systematically with increasing TiO₂ content demonstrating that the measured TiO₂ contents in olivine are not caused by micro-inclusions but by incorporation of Ti in the olivine structure. Least squares fitting of 20 olivine unit cell volumes against the Ti content yield the relation: V (ų)=290.12(1) + 23.67(85) N_Ti. The partial molar volume of end-member Mg₂TiO₄ olivine (N_Ti=1) is thus 47.24±0.13 cm³. The change of the Ti solubilty in olivine coexistent with rutile and orthopyroxene with pressure was investigated by piston cylinder experiments at 1,400°C from 15 to 55 kbar. There is no increase in TiO₂ contents with pressure and in all the experiments olivine contains ~0.2 wt.% TiO₂. Moreover, a thermodynamic analysis indicates that Ti contents of olivine coexisting with rutile and orthopyroxene should decrease rather than increase with increasing pressure. These data indicate that the ilmenite exsolution observed in some natural olivine does not signify an ultra-deep origin of peridotite massifs.     

Staying cool in a changing climate: Reaching vulnerable populations during heat events

The frequency and intensity of hot weather events are expected to increase globally, threatening human health, especially among the elderly, poor, and chronically ill. Current literature indicates that emergency preparedness plans, heat health warning systems, and related interventions may not be reaching or supporting behavior change among those most vulnerable in heat events. Using a qualitative multiple case study design, we comprehensively examined practices of these populations to stay cool during hot weather (“cooling behaviors”) in four U.S. cities with documented racial/ethnic and socio-economic disparities and diverse heat preparedness strategies: Phoenix, Arizona; Detroit, Michigan; New York City, New York; and Philadelphia, Pennsylvania. Based on semi-structured in-depth interviews we conducted with 173 community members and organizational leaders during 2009–2010, we assessed why vulnerable populations do or do not participate in health-promoting behaviors at home or in their community during heat events, inquiring about perceptions of heat-related threats and vulnerability and the role of social support. While vulnerable populations often recognize heat's potential health threats, many overlook or disassociate from risk factors or rely on experiences living in or visiting warmer climates as a protective factor. Many adopt basic cooling behaviors, but unknowingly harmful behaviors such as improper use of fans and heating and cooling systems are also adopted. Decision-making related to commonly promoted behaviors such as air conditioner use and cooling center attendance is complex, and these resources are often inaccessible financially, physically, or culturally. Interviewees expressed how interpersonal, intergenerational relationships are generally but not always protective, where peer relationships are a valuable mechanism for facilitating cooling behaviors among the elderly during heat events. To prevent disparities in heat morbidity and mortality in an increasingly changing climate, we note the implications of local context, and we broadly inform heat preparedness plans, interventions, and messages by sharing the perspectives and words of community members representing vulnerable populations and leaders who work most closely with them.     

Effects of streamflow isotope sampling strategies on the calibration of a tracer-aided rainfall-runoff model

Isotopes are increasingly used in rainfall-runoff models to constrain conceptualisations of internal catchment functioning and reduce model uncertainty. However, there is little guidance on how much tracer data is required to adequately do this, and different studies use data from different sampling strategies. Here, we used a 7-year time series of daily stable water isotope samples of precipitation and streamflow to derive a range of typical stream sampling regimes and investigate how this impacts calibration of a semi-distributed tracer-aided model in terms of flow, deuterium and flux age simulations. Over the 7 years weekly sampling facilitated an almost identical model performance as daily, and there were only slight deteriorations in performance for fortnightly sampling. Monthly sampling resulted in poorer deuterium simulations and greater uncertainty in the derived parameter sets ability to accurately represent catchment functioning, evidenced by unrealistic reductions in the volumes of water available for mixing in the saturation area causing simulated water age decreases. Reducing sampling effort and restricting data collection to 3 years caused reductions in the accuracy of deuterium simulation, though the deterioration did not occur if sampling continued for 5 years. Analysis was also undertaken to consider the effects of reduced sampling effort over the driest and wettest hydrological years to evaluate effects of more extreme conditions. This showed that the model was particularly sensitive to changes in sampling during dry conditions, when the catchment hydrological response is most non-linear. Across all dataset durations, sampling in relation to flow conditions, rather than time, revealed that samples collected at flows >Q50 could provide calibration results comparable to daily sampling. Targeting only extreme high flows resulted in poor deuterium and low flow simulations. This study suggests sufficient characterization of catchment functioning can be obtained through reduced sampling effort over longer timescales and the targeting of flows >Q50.     

Intrusion and contamination of high-temperature dunitic magma: the Nordre Bumandsfjord pluton, Seiland, Arctic Norway

The Caledonian Nappe Complex of Arctic Norway provides rare insights into the interaction between mafic–ultramafic magmas and the deep continental crust. The Kalak Nappe Complex contains >25,000 km³ of mafic igneous rocks, mostly layered gabbros, making up the 570–560 Ma Seiland Igneous Complex. The complex has been intruded by a series of ultramafic magmatic rocks, including the Nordre Bumandsfjord pluton. Field relationships in this pluton show that extremely fluid, dry, relatively Fe-rich (Fo₈₁) dunite magmas intruded a pile of cumulate gabbros, with block stopping and intrusive brecciation. Diking on scales from mm to metres and extensive melting and assimilation of the gabbros attest to high temperatures, consistent with a 2-km-wide granulite-facies contact aureole. Major- and trace-element trends show that the dunites were progressively contaminated by a cpx-rich partial melt of the gabbros, producing a range of lithologies from dunite through lherzolites to wehrlite. Experimental studies of natural samples at 0.8–1 GPa define the dunite solidus at 1,650–1,700 °C. In the average peridotite, contamination has produced a crystallisation interval of ca 400 °C (1,600–1,200 °C); this would provide large amounts of heat for melting and metamorphism and would maintain the fluidity of the magmas to relatively low T, consistent with field relationships. Thermochemical and dynamic modelling demonstrates that the dunitic primary magmas may represent the last melting of a rapidly ascending diapir of previously depleted subducted oceanic lithosphere. The mafic rocks of the Seiland Complex may already have been extracted from this diapir, and the late dikes of the province may reflect melting of the asthenosphere as the diapir spread out beneath the lithosphere. Ultramafic magmas, abundant in the Archean, may still be more common than usually assumed. However, they would only penetrate to the shallow crust under unusually extensional conditions, where ascent could outpace assimilation.