Crystal chemical controls on rare earth element partitioning between epidote-group minerals and melts: an experimental and theoretical study

We have experimentally determined the partitioning of REE (rare earth elements) between zoisite and hydrous silicate melt at 1,100 °C and 3 GPa. All REE behave moderately compatible in zoisite with respect to the melt and all show a smooth parabolic dependence on ionic radius. The partitioning parabola peaks at Nd , and the compatibility slightly decreases towards La and decreases by half an order of magnitude towards Yb . Application of the elastic strain model of Blundy and Wood (1994) to the available zoisite and allanite REE mineral/melt partitioning data and comparison with partitioning pattern calculated from a combination of structural and physical data (taken from the literature) with the elastic strain model suggest that in zoisite REE prefer the A1-site and that only La and Ce are incorporated into the A2-site in significant amounts. In contrast, in allanite, all REE are preferentially incorporated into the large and highly co-ordinated A2 site. As a result, zoisite fractionates the MREE effectively from the HREE and moderately from the LREE, while allanite fractionates the LREE very effectively from the MREE and HREE. Consequently, the presence of either zoisite or allanite during slab melting will lead to quite different REE pattern in the produced melt.Editorial responsibility: J. Hoefs     

Experimental peridotite–melt reaction at one atmosphere: a textural and chemical study

Sieve-textured clinopyroxene and spinel are common in mantle xenoliths and have been interpreted to be the result of partial melting, mantle metasomatism and host magma–xenolith reaction during transport. In this paper, we test the latter hypothesis with a series of reduced and oxidized experiments at 1,200 and 1,156°C at one atmosphere using a synthetic leucitite melt and discs of natural peridotite. Our results show that sieve texture development on clinopyroxene and spinel in mantle xenoliths is the result of a multistage reaction process. In the first step, orthopyroxene undergoes incongruent dissolution to produce a silica and alkali-rich melt together with olivine. As this melt migrates along grain boundaries it causes incongruent dissolution of clinopyroxene and spinel. The incongruent dissolution mechanism involves complete dissolution of the clinopyroxene or spinel followed by nucleation and growth of a secondary clinopyroxene or spinel once the reacting melt is saturated. The reaction of orthopyroxene, clinopyroxene and spinel with infiltrated host magma results in a range of melt compositions that are very similar to those interpreted to be due to very small degrees of partial melting. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

High-technology industries in Korea: Spatial linkages and policy implications

This study seeks to analyze spatial linkages of high-technology (high-tech) firms in Korea and to suggest directions for high-tech industrial development policies for regional economic development. The data were derived from questionnaire and interview surveys conducted in high-tech firms throughout Korea. Patterns of spatial linkages and the intensity of local linkages of input materials, output sales, business services, and high-tech labor forces were analyzed. Characteristics of regions and high-tech firms are identified as significant dimensions in determining the intensity of local linkages of input and output materials. Four types of possible high-tech clusters, self-supporting, redeveloping, assembling, and dependent, are also identified based on the characteristics of regions and high-tech firms. Policy implications for successful high-tech industrial development in Korea are suggested from a consideration of the four types of high-tech cluster.     

Estimating groundwater inflow and leakage outflow for an intermontane lake with a structurally complex geology: Georgetown Lake in Montana,USA

Stable isotopes of the water molecule (δ¹⁸O and δD) for groundwater, lake water, streams, and precipitation were coupled with physical flux measurements to investigate groundwater–lake interactions and to establish a water balance for a structurally complex lake. Georgetown Lake, a shallow high-latitude high-elevation lake, is located in southwestern Montana, USA. The lake is situated between two mountain ranges with highlands primarily to the east and south of the lake and a lower valley to the west. An annual water balance and (δ¹⁸O and δD) isotope balance were used to quantify annual groundwater inflows of 2.5?×?10⁷ m³/year and lake leakage outflows of 1.6?×?10⁷ m³/year. Roughly, 57% of total inflow to the lake is from groundwater, and 37% of total outflow at Georgetown Lake is groundwater. Stable isotopes of groundwater and springs around the lake and surrounding region show that the east side of the lake contains meteoric water recharged annually from higher mountain sources, and groundwater discharge to the lake occurs through this region. However, springs located in the lower western valley and some of the surrounding domestic wells west of the lake show isotopic enrichment indicative of strong to moderate evaporation similar to Georgetown Lake water. This indicates that some outflowing lake water recharges groundwater through the underlying west-dipping bedrock in the region.     

The Effect of Wedge Structure on Displacement Subduction of Piedmont Thrust Structure: A Case Study of the Southern Margin of Junggar Basin

介于复活的天山造山带与稳定的准噶尔克拉通之间的准噶尔盆地南缘前陆冲断带,是印度板块与欧亚大陆碰撞的远距离效应产物,也是新近纪以来青藏高原隆升并向北推挤的直接结果.前陆冲断带吸收了来自造山带的水平缩短构造位移量后,克拉通一侧构造趋于稳定.准噶尔盆地南缘与世界上多数前陆冲断带构造地质特征相似,通过区域地震剖面的精细构造几何学和运动学解析,发现其中的楔形构造非常典型,是前陆冲断带内部冲断构造位移量消减的主要方式之一,控制着前陆冲断带分布范围和变形方式.准噶尔盆地南缘构造变形主要由南侧的天山造山带向北逆掩冲断,但是大部分冲断构造位移量是通过楔形构造反向传递后消减.紧邻天山北麓的齐古-喀拉扎-昌吉等构造带,山前深部的楔形体沿侏罗系西山窑组煤层向北扩展过程中,部分位移量沿构造楔顶部的反冲断层向南消减,并切割上覆地层形成第一排背斜带,另一部分位移量则继续向北传递,在断坡位置引发褶皱变形,形成霍-玛-吐第二排构造带和安集海-呼图壁第三排背斜带.准噶尔盆地南缘第二、三排构造带中-新生界内部发育多个小型的构造楔型体,这些互相叠置的楔型构造横向延伸不大,加大了构造变形的复杂性和构造圈闭识别的难度.     

A Space-Time GIS Approach to Exploring Large Individual-based Spatiotemporal Datasets

The increasing number of large individual-based spatiotemporal datasets in various research fields has challenged the GIS community to develop analysis tools that can efficiently help researchers explore the datasets in order to uncover useful information. Rooted in Hägerstrand's time geography, this study presents a generalized space-time path (GSTP) approach to facilitating visualization and exploration of spatiotemporal changes among individuals in a large dataset. The fundamental idea of this approach is to derive a small number of representative space-time paths (i.e. GSTPs) from the raw dataset by identifying spatial cluster centers of observed individuals at different time periods and connecting them according to their temporal sequence. A space-time GIS environment is developed to implement the GSTP concept. Different methods of handling temporal data aggregation and the creation of GSTPs are discussed in this article. Using a large individual-based migration history dataset, this study successfully develops an operational space-time GIS prototype in ESRI's ArcScene and ArcMap to provide a proof-of-concept study of this approach. This space-time GIS system demonstrates that the proposed GSTP approach can provide a useful exploratory analysis and geovisualization environment to help researchers effectively search for hidden patterns and trends in such datasets.     

Life cycle of chokka-squid Loligo reynaudii in South African waters

This short note summarises past and current knowledge of the life cycle of chokka-squid Loligo reynaudii d’Orbigny, 1845, in South African waters. Prior to approximately 2010, the chokka-squid stock was considered simple and uniform, with one paralarval pool, the drift of paralarvae westwards, one main nursery area and one main, long spawning migration of adult squid eastwards, back to the main spawning grounds. Based on new information, this life-history scheme has been revised. Genetically, the stock is uniform; however, morphologically, it comprises three main geographic groups. It is proposed that the differences between the groups originate from many different paralarval events and that short (not long) migrations dominate the life cycle.     

Identification of shocked quartz by scanning cathodoluminescence imaging

Abstract— Quartz grains subjected to high‐strain‐rate shock waves owing to meteorite or cometary impact on Earth's surface commonly display shock lamellae. These lamellae appear as remarkably straight, thin, planar features (microstructures) in sets within which lamellae are essentially parallel to each other and spaced ≤ 20 μm apart. Two or more intersecting sets are typically present. Shock lamellae are commonly recognized and identified by optical methods, by use of the transmission electron microscope (TEM), and by etching polished sections and subsequent examination with a scanning electron microscope (SEM) operated in the secondary electron mode. We present here a method for observing planar microstructures in shocked quartz by using a cathodoluminescence (CL) detector attached to a SEM. The method relies on the fact that planar microstructures in quartz arising as a result of shock display no CL whatever; thus, they show up as distinct, thin, black lines on otherwise luminescent quartz grains. We used scanning CL imaging to study shocked quartz from the Ries Crater, Germany, a well‐known impact crater of Miocene age. We demonstrate that shock‐produced planar microstructures are clearly displayed in SEM‐CL images and can be distinguished from microfractures generated by tectonism, and subsequently filled with quartz, and other similar features not related to impact events. The SEM‐CL method provides a powerful supplement to other methods of identifying shocked quartz. It commonly provides better spatial resolution than does standard optical methods, and does not require etching of quartz grains. Further, it is easier and faster to use than are TEM methods, although it is not capable of the fine‐scale defect analysis possible with TEM.     

Murky water: Analyzing risk perception and stakeholder vulnerability related to sewage impacts in mangroves of East Africa

Coastal cities in East Africa are growing rapidly and consequently there is a rapid increase in urban sewage production, putting added pressure on already strained treatment systems. As a result, peri-urban mangroves are receiving extensive amounts of sewage but very little is know as to the ecological and societal consequences of this. However, UNEP among others advocate the use of low-cost, natural sewage treatment technology whenever possible and mangroves have been suggested as useful second stage biofilters. Because of the high resource dependency in many peri-urban coastal communities in East Africa, it is imperative to investigate potential societal impacts on local communities using sewage impacted peri-urban mangroves. Consequently this paper aims to characterize stakeholder groups currently affected by sewage impacted mangroves and thus also map vulnerabilities across local users in relation to future initiatives to use mangroves as biofilters along the East African coast. As risk perception is an important part of vulnerability, and risk perception related to sewage and pollution in an African setting has been little studied, we also aim to contribute baseline data on risk perception related to pollution across peri-urban populations in Kenya, Tanzania and Mozambique.     

The accretion powered spin-up of GRO J1750−27

The timing properties of the 4.45 s pulsar in the Be X-ray binary system GRO J1750−27 are examined using hard X-ray data from INTEGRAL and Swift during a type II outburst observed during 2008. The orbital parameters of the system are measured and agree well with those found during the last known outburst of the system in 1995. Correcting the effects of the Doppler shifting of the period, due to the orbital motion of the pulsar, leads to the detection of an intrinsic spin-up that is well described by a simple model including     and     terms of  −7.5 × 10⁻¹⁰ s s⁻¹  and  1 × 10⁻¹⁶ s s⁻²  , respectively. The model is then used to compare the time-resolved variation of the X-ray flux and intrinsic spin-up against the accretion torque model of Ghosh & Lamb; this finds that GRO J1750−27 is likely located 12–22 kpc distant and that the surface magnetic field of the neutron star is  ∼2 × 10¹²  G. The shape of the pulse and the pulsed fraction shows different behaviour above and below 20 keV, indicating that the observed pulsations are the convolution of many complex components.