Interactive visualization of 3D mantle convection

The current availability of thousands of processors at many high performance computing centers has made it feasible to carry out, in near real time, interactive visualization of 3D mantle convection temperature fields, using grid configurations having 10–100 million unknowns. We will describe the technical details involved in carrying out this endeavor, using the facilities available at the Laboratory of Computational Science and Engineering (LCSE) at the University of Minnesota. These technical details involve the modification of a parallel mantle convection program, ACuTEMan; the usage of client–server socket based programs to transfer upwards of a terabyte of time series scientific model data using a local network; a rendering system containing multiple nodes; a high resolution PowerWall display, and the interactive visualization software, DSCVR. We have found that working in an interactive visualizastion mode allows for fast and efficient analysis of mantle convection results. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Magma plumbing systems in large igneous provinces: Inferences from cyclical variations in Palaeogene East Greenland basalts

We present compositional data on a 1,250-m-thick sequence of sparsely porphyritic lavas that comprise the Geikie Plateau Formation, part of the ~55-Ma break-up-related flood basalts in East Greenland. Major element compositions are relatively restricted (6.3–7.6 wt% MgO; 2.2–2.4 wt% TiO₂), with two excursions to more evolved compositions (2.4–3.4 wt% TiO₂) that are similar to the inferred parental magma of the nearby Skaergaard Intrusion. Major and trace element calculations show that fractional crystallisation is the principal control on magma compositions, and the cyclical sequential variations imply regular magma chamber replenishment events. Isotopic data indicate minor crustal assimilation, but with different contaminants for the main group (amphibolitic gneiss) and evolved cycles (granulitic gneiss). Rifting episodes may have allowed more primitive magmas to ascend to shallow crustal levels and subsequently fractionate to more evolved compositions in a separate chamber, which was perhaps similar to the source of the Skaergaard Intrusion.Electronic Supplementary Material Supplementary material is available in the online version of this article at Editorial responsibility: I. Parsons     

An unsupervised multi-scale segmentation method based on automated parameterization

The continuous improvement of the launched satellites’ spatial and spectral resolutions has brought new challenges for remote sensing image segmentation technology. The traditional supervised methods greatly depend on artificial interpretation and reduce the degree of automation and robustness of image segmentation. Therefore, the article proposes a novel unsupervised multi-scale segmentation method for high-resolution remote sensing images based on automated parameterization and it mainly includes three steps, adaptive selection of scale parameter (SP) based on local area homogeneity index J-value, multi-scale segmentation based on the inter-scales boundaries constraint strategy, and region merging based on multi-features. The article makes experiments by multi-group high-resolution remote sensing images of different launched satellites and compares the proposed method with the well-known commercial software eCognition and a traditional supervised method. The results show that the proposed method can locate the object edges more accurately and extract the object outlines more completely, and needs no human intervention in segmentation process, so it can provide a generic and effective unsupervised solution for high-resolution remote sensing image segmentation.     

An integrated microtextural and chemical approach to zircon geochronology: refining the Archaean history of the Napier Complex,east Antarctica

Integrated textural and chemical characterisation of zircon is used to refine the U–Pb geochronology of the Archaean, ultra-high temperature Napier Complex, east Antarctica. Scanning electron microscope characterisation of zircon and the rare earth element compositions of zircon, garnet and orthopyroxene are integrated to place zircon growth in an assemblage context, thereby providing tighter constraints on the timing of magmatic and metamorphic events. Data indicate that magmatism occurred in the central and northern Napier Complex at ca. 2,990 Ma. A regional, relatively low-pressure metamorphic event occurred at ca. 2,850–2,840 Ma. Mineral REE data from garnet-bearing orthogneiss indicate that ca. 2,490–2,485 Ma U–Pb zircon ages provide an absolute minimum age for the ultrahigh temperature (UHT) foliation preserved in this rock. Internal zircon zoning relationships and estimated zircon-garnet D_REE values from paragneiss suggest that an absolute minimum age of ultra-high temperature metamorphism is ca. 2,510 Ma, but that it is more likely to be older than ca. 2,545 Ma. We suggest that the high proportion of published zircon U–Pb data with ages between ca. 2,490–2,450 Ma reflects late, post-peak zircon growth and does not date the timing of peak UHT metamorphism.Electronic Supplementary Material Supplementary material is available for this article at     

Groundwater quality and its monitoring in the Baltic States

In the Baltic countries — Estonia, Latvia and Lithuania — groundwater is the principal and only source of clean drinking water. Its safe yield is rather large — 6.7 mln m³/d. At present, consumption does not reach half of this amount. Therefore, the resources available will be sufficient for a rather remote future, provided that groundwater is not polluted. Under Soviet rule, insufficient attention was paid to ecological problems in the Baltic States. As a result, due to constantly increasing surface pollution, groundwater quality is decreasing. The topmost, unconfined aquifer is unfit for use, especially in many urbanized areas. Moreover, pollutants, especially organics, are starting to enter the lower, artesian aquifers. To determine and forecast groundwater quality, a monitoring system has been worked out. However, in order to protect groundwater, besides monitoring, new laws, regulations, and guarantees for their implementation are necessary.     

Effects of human population growth on the Fraser and Okanagan River systems,Canada: a comparative inquiry

Perhaps nowhere in Canada, if indeed in North America, could two adjacent watershed basins be selected which show such remarkable differences in their historical and recent response to human population growth effects. One — the Fraser — covers some 234,000 km² (about one quarter of the province of British Columbia) and houses nearly two-thirds of its total population. The other — the Okanagan — forms a small part (some 14,000 km²) of the upper Columbia River drainage in Canada. Native Indian populations at maximum before European contact in the late 1700s were about 50,000 in the Fraser basin and probably less than a fifth of that in the Okanagan. Present total resident populations of the Fraser and Okanagan basins, about 2 million and 1\4 million respectively, have greatly different distributions and thereby effects within the watersheds they occupy. In addition seasonal tourist populations have important and differential impacts within the two watersheds. Expression of these effects on water, fisheries and other aquatic resources of the two basins are explored along with possibilities and suggestions for their sustainable development. The latter, despite some glimmers of hope, will not be tenable without major changes in public attitude, in government policy at all levels, and in other measures which to many may seem impossible.     

基于多尺度循环注意力网络的遥感影像场景分类方法

高分辨率遥感影像场景分类一直是遥感领域的研究热点.针对遥感场景对尺度的需求具有多样性的问题,提出了一种基于多尺度循环注意力网络的遥感影像场景分类方法.首先,通过Resnet50提取遥感影像多个尺度的特征,采用注意力机制得到影像不同尺度下的关注区域,对关注区域进行裁剪和缩放并输入到网络.然后,融合原始影像不同尺度的特征及其关注区域的影像特征,输入到全连接层完成分类预测.此分类方法在UC Merced Land-Use和NWPU-RESISC45公开数据集上进行了验证,平均分类精度较基础模型Resnet50分别提升了1.89%和2.70%.结果表明,多尺度循环注意力网络可以进一步提升遥感影像场景分类的精度.      

SHRIMPDB: a new geoanalytical database for U-Th-Pb geochronological data from SHRIMP measurements

This paper introduces a novel web-based database, SHRIMPDB, to support the efficient reutilization of U-Th-Pb geochronological data from sensitive high-resolution ion microprobe (SHRIMP) measurements. In order to provide complete data content that can be reutilized by Earth scientists, a new data model containing analytical data and relevant sample metadata is proposed according to analyses of measurement procedures and the data characteristics of SHRIMP. Vivid data visualization, real-time data query interfaces (including a novel and intuitive polygonal region search), and a pragmatic data management module are designed and implemented using web-based and cloud GIS-based technologies, which provide a platform for Earth scientists to efficiently curate and share SHRIMP data on the internet. An incentive that encourages geochronologists to contribute data is suggested through cooperation between SHRIMPDB and the Beijing SHRIMP center. The database is currently under evaluation at the Beijing SHRIMP center. SHRIMPDB is globally available online at http://202.198.17.27/shrimpdb/home.     

Rear-arc vs. arc-front volcanoes in the Katmai reach of the Alaska Peninsula: a critical appraisal of across-arc compositional variation

Physical and compositional data and K-Ar ages are reported for 14 rear-arc volcanoes that lie 11–22 km behind the narrowly linear volcanic front defined by the Mount Katmai-to-Devils Desk chain on the Alaska Peninsula. One is a 30-km³ stratocone (Mount Griggs; 51–63% SiO₂) active intermittently from 292 ka to Holocene. The others are monogenetic cones, domes, lava flows, plugs, and maars, of which 12 were previously unnamed and unstudied; they include seven basalts (48–52% SiO₂), four mafic andesites (53–55% SiO₂), and three andesite-dacite units. Six erupted in the interval 500–88 ka, one historically in 1977, and five in the interval 3–2 Ma. No migration of the volcanic front is discernible since the late Miocene, so even the older units erupted well behind the front. Discussion explores the significance of the volcanic front and the processes that influence compositional overlaps and differences among mafic products of the rear-arc volcanoes and of the several arc-front edifices nearby. The latter have together erupted a magma volume of about 200 km³, at least four times that of all rear-arc products combined. Correlation of Sr-isotope ratios with indices of fractionation indicates crustal contributions in volcanic-front magmas (0.7033–0.7038), but lack of such trends among the rear-arc units (0.70298–0.70356) suggests weaker and less systematic crustal influence. Slab contributions and mantle partial-melt fractions both appear to decline behind the front, but neither trend is crisp and unambiguous. No intraplate mantle contribution is recognized nor is any systematic across-arc difference in intrinsic mantle-wedge source fertility discerned. Both rear-arc and arc-front basalts apparently issued from fluxing of typically fertile NMORB-source mantle beneath the Peninsular terrane, which docked here in the Mesozoic.Electronic Supplementary Material Supplementary material is available for this article if you access the article at . A link in the frame on the left on that page takes you directly to the supplementary material.Editorial responsibility: T.L. Grove     

Structure and tectonics of the Achankovil Shear Zone, southern India

An integrated approach to resolve the kinematics of the controversial Achankovil Shear Zone (AKSZ) has been attempted involving remote sensing data, shaded relief topo-maps, ground details of lithology and mesoscopic structures. An excellent correlation of structural trends exists on all scales of observation. The AKSZ is distinctly defined by NW–SE trending foliation fabrics with steep dips to southwest. The adjacent Madurai block and Trivandrum block show contrasting lithological and structural characteristics as shown in structural cross-sections.The mesoscopic structural studies reveal the presence of sub-horizontal stretching lineations, asymmetric structures like S–C′ fabrics, porphyroclasts, ‘S’ shaped folds and shear bands confirming the strike-slip component of shear along AKSZ. The deformation undergone by the AKSZ could be described in terms of an initial dextral deformation — D₁, reactivated and superimposed by sinistral kinematics — D₂, which is also supported by megascopic structural interpretation of remote sensing data. The megascopic structural interpretation of AKSZ displays en-echelon pattern of lineaments with right overstepping arrangement, which can be interpreted as an evidence of the latest sinistral transpressional deformation.     

Ubiquitous interactive visualization of 3D mantle convection using a web-portal with Java and Ajax framework

We have developed a new strategy and espouse a novel paradigm for large-scale computing and real-time interactive visualization. This philosophy calls for intense interactive sessions for a couple of hours at a time at the expense of storing data on many disk drives during regular or heroic runs on massively parallel systems. We have already carried out successfully real-time volume-rendering visualization by employing hundreds of processors for a grid with over 25 million unknowns. Both Cartesian and spherical 3D mantle convection are visualized. The volume-rendered images are viewed on a large display device, with many panels holding around 13 million pixels. We will employ a software strategy involving an hierarchical rendering service, which will have as software an Ajax interface for interactive visualization of large data sets on many different platforms from desktop PC’s to hand-held devices, such as the OQO and the Nokia N-800. An option for stereo viewing is also implemented. We have installed a user interface as web application, using Java and Ajax framework in order to achieve over the Internet reasonable accessibility to our ongoing runs. Our goal is to expand the array of interactive devices, which will make it feasible to carry out ubiquitous visualization and monitoring of large-scale simulations or onsite events and to allow for collaborations across oceans.     

Urban development and urban geography in Romania: The contribution of Vintila Mihailescu

Urban development has been a dramatic consequence of modernisation in Romania over the last hundred years. Although there are some differences between the periods of capitalism and socialism — notably the socialist emphasis on the central planning of industrial growth rather than the development of a well-rounded urban society — the population resident in towns has increased inexorably from 2.08 million in 1912 (16.3% of the total population to the country) to 3.71 million (23.4%) in 1948 and 10.49 million (47.3%) in 1980. The scope of Romanian geography has plainly altered in response to the shift in the rural-urban balance, all the more so in view of the long-standing concentration of effort on domestic issues. The paper examines the relationship between urban development and urban geography during this century: urban geography has become an integral part of the discipline whereas in 1900 interest was negligible. The transition has not been entirely smooth but considerable coherence arises from the work of Vintila Mihailescu (1890–1978) : a complete geographer but one who always emphasised the importance of urban geography. Since his death new leaders have emerged to ensure a continued commitment to what is now a fundamental element of Romanian geography.     

Globalisation, information technology and the emergence of niche transnational cities: the growth of the call centre sector in Dublin

The development of information and communications technologies (ICT) has facilitated the emergence of a complex global urban system in which many formerly lower-order cities have been carving out “niche” specialist functions serving urban fields of transnational dimension. This is illustrated in the case of Dublin, which in recent years has been transcending its traditional role as Ireland’s national metropolis through the development of a range of functions servicing mainly European markets. One such function comprises pan-European telephone call centre operations. The development and characteristics of this newly-emerging sector are described. It is argued that the growth of the sector confirms Dublin’s — and Ireland’s — dependent position in the international division of labour, and that its long-term sustainability is open to question.     

西北边境地区冰冻圈遥感调查与监测(2013—2015年)主要进展

2013—2015年由中国国土资源航空物探遥感中心牵头开展了中国地质调查局地质调查项目“西北边境地区国土资源遥感综合调查”,我国西北边境高寒、高海拔地区的冰冻圈遥感调查是其中一项重要内容。冰冻圈遥感调查的主要进展有: 基于地形地貌、地温分布和坡度坡向特征等综合信息完成了藏北等地区的多年冻土范围调查; 利用高分1号(GF-1)宽幅数据和Landsat数据,对2013年1月—2014年12月期间阿里西部地区近10 000 km²的积雪覆盖情况进行了连续19个期次的动态监测; 基于1999—2013年间的Landsat多期影像,对班公湖和斯潘古尔湖冷季6个月份的湖冰覆盖情况进行了动态调查。     

High-pressure/ultrahigh-pressure eclogites from the Hong’an Block,East-Central China: geochemical characterization,isotope disequilibrium and geochronological controversy

The Hongan Block (western Dabieshan) exposes a series of HP/UHP metamorphic rocks, with a S-to-N distribution from blueschist–greenschist, kyanite-free, to kyanite- and coesite-bearing eclogites. The available age data are inconclusive that hinder our understanding of the tectonic evolution of the Block. The metamorphic temperatures in the Hongan Block (T_meta 700 to 500°C) are lower by 50–150°C than that of the Dabie and Sulu terranes. In this work, we undertook new trace element and Sr–Nd–O isotopic analyses on minerals in order to gain more insight into the geochronological problems. The results are as follows: (1) Trace element distribution patterns suggest that garnet and omphacite in many cases are out of chemical equilibrium; and the presence of high-temperature LREE-rich mineral inclusions (e.g., epidote) in garnet and omphacite has contributed to isotope disequilibrium. (2) Sm–Nd isotope analyses yielded no isochron ages for the Hongan eclogites. (3) Rb–Sr isotope analyses gave mixed results; in some cases, coexisting minerals are completely out of isotope equilibrium, and in others, isochron relationship is established, yielding ages from 210 Ma to 225 Ma. The pattern of Rb–Sr isotope disequilibrium appears to be independent of the petrological and O-isotope temperatures. (4) In contrast to the unequilibrated Sm–Nd isotopic systems, oxygen isotopes of the eclogite minerals seem to have attained isotope equilibrium or near-equilibrium. Oxygen isotope temperatures are comparable with petrological temperatures. However, this is an apparent feature due to mass balance constraints. (5) Whole-rock ¹⁸O values show a large variation from +10 to –8, suggesting that their protoliths have undergone very different processes of water–rock interaction. In view of the overall geochronological information, we conclude that the HP/UHP metamorphism in the Hongan Block took place in the Triassic at about 220–230 Ma, as observed in the Dabie and Sulu terranes. The significance of published Paleozoic dates (450–300 Ma) for the Xiongdian eclogite is not clear. However, any hypotheses advocating two periods of UHP metamorphic events for the same tectonic unit or in the same locality are not constrained by the geochronological data.Electronic Supplementary Material Supplementary material is available for this article at     

Melt extraction pathways and stagnation depths beneath the Madeira and Desertas rift zones (NE Atlantic) inferred from barometric studies

The Madeira and Desertas Islands (eastern North Atlantic) show well-developed rift zones which intersect near the eastern tip of Madeira (São Lourenço peninsula). We applied fluid inclusion barometry and clinopyroxene-melt thermobarometry to reconstruct levels of magma stagnation beneath the two adjacent rifts and to examine a possible genetic relationship during their evolution. Densities of CO₂-dominated fluid inclusions in basanitic to basaltic samples from São Lourenço yielded frequency maxima at pressures of 0.57–0.87 GPa (23–29 km depth) and 0.25–0.32 GPa (8–10 km), whereas basanites, basalts and xenoliths from the Desertas indicate 0.3–0.72 GPa (10–24 km) and 0.07–0.12 GPa (2–3 km). Clinopyroxene-melt thermobarometry applied to Ti-augite phenocryst rim and glass/groundmass compositions indicates pressures of 0.45–1.06 GPa (15–35 km; São Lourenço) and 0.53–0.89 GPa (17–28 km; Desertas Islands) which partly overlap with pressures indicated by fluid inclusions. We interpret our data to suggest a multi-stage magma ascent beneath the Madeira Archipelago: main fractionation occurs at multiple levels within the mantle (>15 km depth) and is followed by temporary stagnation within the crust prior to eruption. Depths of crustal magma stagnation beneath São Lourenço and the Desertas differ significantly, and there is no evidence for a common shallow magma reservoir feeding both rift arms. We discuss two models to explain the relations between the two adjacent rift systems: Madeira and the Desertas may represent either a two-armed rift system or two volcanic centres with separate magma supply systems. For petrological and volcanological reasons, we favour the second model and suggest that Madeira and the Desertas root in distinct regions of melt extraction. Magma focusing into the Desertas system off the hotspot axis may result from lithospheric bending caused by the load of the Madeira and Porto Santo shields, combined with regional variations in melt production due to an irregularly shaped plume.Electronic Supplementary Material Supplementary material is available for this article if you access the article at . A link in the frame on the left on that page takes you directly to the supplementary material.Editorial responsibility: J. Hoefs     

Lithospheric mantle beneath the south-eastern Siberian craton: petrology of peridotite xenoliths in basalts from the Tokinsky Stanovik

We provide petrographic, major and trace element data for over 30 spinel peridotite xenoliths from the Tokinsky Stanovik (Tok) volcanic field on the Aldan shield to characterize the lithospheric mantle beneath the south-eastern margin of the Siberian craton, which formed in the Mesoproterozoic. High equilibration temperatures (870–1,010°C) of the xenoliths and the absence of garnet-bearing peridotites indicate a much thinner lithosphere than in the central craton. Most common among the xenoliths are clinopyroxene-poor lherzolites and harzburgites with Al₂O₃ and CaO contents nearly as low as in refractory xenoliths from kimberlite pipes (Mir, Udachnaya) in the central and northern Siberian craton. By contrast, the Tok peridotites have higher FeO, lower Mg-numbers and lower modal orthopyroxene and are apparently formed by shallow partial melting (3 GPa). Nearly all Tok xenoliths yield petrographic and chemical evidence for metasomatism: accessory phlogopite, amphibole, phosphates, feldspar and Ti-rich oxides, very high Na₂O (2–3.1%) in clinopyroxene, LREE enrichments in whole-rocks.Electronic Supplementary Material Supplementary material is available for this article at     

Petrogenetic and metallogenetic responses to Miocene slab flattening: new constraints from the El Indio-Pascua Au–Ag–Cu belt,Chile/Argentina

The Eocene–Miocene volcanic and hypabyssal rocks of the El Indio-Pascua Au–Ag–-Cu belt in the southern central Andean flat-slab region are medium–high-K calc-alkaline arc suites, ranging in composition from andesite to rhyolite. A significant transition in magmatic trace element chemistry, coinciding with a pronounced reduction in magma output, occurred in the late-Middle Miocene as documented by ⁴⁰Ar–³⁹Ar geochronology. The upper Eocene–lower-Middle Miocene rocks exhibit low Sr/Y ratios (<50), minor heavy REE fractionation with Sm/Yb ratios not exceeding 3.5 and, in some cases, minor negative Eu anomalies. In contrast, the largely dacitic rocks erupted after ca. 13 Ma are depleted in Y (10 ppm), have generally high, but variable Sr/Y ratios (30–200), exhibit moderate middle and heavy REE fractionation (Sm/Yb: 3.7–5.9) and lack negative Eu anomalies. The latter features are characteristic of adakitic suites (i.e. slab-melts), but the regional temporal and spatial distribution of arc magmatism precludes a major magma source in the downgoing slab. This evolution is interpreted as reflecting a progressive increase in pressure and the availability of water in the lower-crustal site of magma generation, establishing both garnet and hornblende as major stable phases in the residuum. The pressure in the lower crust increased in response to episodic crustal thickening related to the shallowing of the slab, a process recorded by the incision of three regional pediplains over the period 17–6 Ma. Elimination of the subarc asthenospheric mantle and much of the lithospheric mantle by ca. 10 Ma permitted direct incursion of slab-derived, highly oxidised metal- and volatile-rich supercritical fluids into the lower crust, stimulating melting of mafic, garnet amphibolitic and eclogitic assemblages.The igneous suites emplaced from 36–11 Ma were associated with widespread, and locally intense, epizonal hydrothermal activity, but this was barren of base and precious metals. The shallow-crustal availability of abundant water highlighted in earlier models was therefore not a metallogenetic determinant. Moreover, economic Au–Ag–Cu mineralization, associated with small volumes of dacitic magma, was restricted to the interval 9.5–5 Ma, and was not initiated until at least 3.5 my after the inception of high-pressure magma generation. In contrast to previous metallogenetic studies, we therefore suggest that this petrochemical transition was not inherently favourable for ore formation. We propose that the incursion of highly oxidized supercritical fluids from the slab into the lower crust was ultimately responsible for the brief Late Miocene metallogenetic episode.Electronic Supplementary Material Supplementary material is available in the online version of this article at Editorial handling: V. Bouchot