Determination of magnetic anisotropy and a ca 1.2 Ga palaeomagnetic pole from the Bremer Bay area,Albany Mobile Belt,Western Australia

Granulite facies tonalitic gneiss, mafic granulite and late metadolerite dykes from Bremer Bay in the Mesoproterozoic Albany Mobile Belt yield palaeomagnetic remanence that were acquired between ca 1.2 Ga and 1.1 Ga. A well‐constrained pole (66.6°N, 303.7°E) fits the ca 1.2 Ga part of the Precambrian Australian apparent polar wander path. This pole is in agreement with the high‐latitude position of Australia at ca 1.2–1.1 Ga shown on some Rodinia reconstructions. More data are required before any significance can be attributed to a second, poorly defined pole (41.8°S, 243.7°E) that falls at some distance from the ca 0.8 Ga part of the Australian apparent polar wander path. Magnetic anisotropy measurements from all samples except late granite dykes indicate northeast‐southwest elongation (i.e. parallel to the local trend of the orogenic belt) and northwest‐southeast contraction. This is in agreement with the orientation of principal strain axes deduced from structures formed during late stages of ductile deformation. The mean magnetic fabric lineation (long axis of the strain ellipsoid) is subparallel to a mineral elongation lineation and the axes of late upright to inclined folds. Short axes of the strain ellipsoid determined from magnetic fabric measurements are in a similar orientation to poles to the axial surfaces of these folds and to the associated cleavage. This mean shortening axis bisects late conjugate ductile shear zones that overprint the folds. This study has shown that structurally complex high‐grade gneisses and intrusive rocks with variable timing relationships may yield meaningful palaeomagnetic results for late stages of metamorphism. Magnetic anisotropy analysis is also seen to be a valuable tool in providing principal strain directions for late ductile deformation.     

Relationality/territoriality: Toward a conceptualization of cities in the world

The paper contributes to the conceptualization of cities in the world by first outlining the conceptual and empirical challenges of theorizing the urban/global nexus in both relational and territorial terms. It argues that the most useful and appropriate approach to understanding contemporary urban governance in global context is to develop a conceptualization that is equally sensitive to the role of relational and territorial geographies, of fixity and flow, of global contexts and place-specificities (and vice versa), of structural imperatives and embodied practices, in the production of cities. In order to illustrate the benefits of this conceptualization, the paper will apply it to the case of how downtown development is governed in many contemporary cities. The role of the Business Improvement District (BID) program and New Urbanist planning models in shaping downtowns will be examined in terms of: (1) how and by whom these models are developed in a global-relational context and are set in motion through scaled circuits of policy knowledge and (2) how the mobilization of these models are conditioned by their territorialization in specific spatial and political economic contexts. The paper emphasizes that the ‘local globalness’ of policy models like BIDs and New Urbanism and their consequences for cities can best be understood through a combined focus on relationality and territoriality.     

The nature and extent of organisms in vessel sea-chests: A protected mechanism for marine bioinvasions

A total of 150 different organisms, including one plant species and 12 animal phyla were identified from sea-chests of 42 vessels visiting or operating in New Zealand between May 2000 and November 2004. Forty-nine percent of organisms were sessile, 42% mobile adults and the remaining 9% sedentary. Decapods were the most represented group with 19 species present among 79% of vessels. Forty percent of organisms were indigenous to New Zealand, 15% introduced, 10% non-indigenous, and 35% of unknown origin. Sea-chests have the potential to (1) transfer non-indigenous organisms between countries across oceanic boundaries; and (2) disperse both indigenous and introduced organisms domestically. The occurrence of adult mobile organisms is particularly significant and indicates that sea-chests may be of greater importance than ballast water or hull fouling for dispersing certain marine species. These findings emphasise the need to assess and manage biosecurity risks for entire vessels rather than different mechanisms (i.e., ballast water, hull fouling, sea-chests, etc.) in isolation.     

W–Au skarns in the Neo-Proterozoic Seridó Mobile Belt,Borborema Province in northeastern Brazil: an overview with emphasis on the Bonfim deposit

The Seridó Mobile Belt (SMB) is located in the Borborema Province in northeastern Brazil and consists of a gneiss basement (Archean to Paleo-Proterozoic), a metasedimentary sequence (marble, quartzites, and schists), and the Brasiliano igneous suite (both of Neo-Proterozoic age). In this region, skarns occur within marble and at the marble–schist contact in the metasedimentary sequence. Most of the skarn deposits have been discovered in the early 1940s, and since then, they have been exploited for tungsten and locally gold. Recently, the discovery of gold in the Bonfim tungsten skarn has resulted in a better understanding of the skarn mineralization in this region. The main characteristics of the SMB skarns are that they are dominantly oxidized tungsten skarns, with the exception of the Itajubatiba and Bonfim gold-bearing skarns, which are reduced based on pyrrhotite as the dominant sulfide, garnet with high almandine and spessartine component, and elevated gold contents. In the Bonfim deposit, pressure estimates indicate that the skarns formed at 10- to 15-km depth. The mineralized skarns present the prograde stage with almandine, diopside, anorthite, and actinolite-magnesio-hornblende, and titanite, apatite, allanite, zircon, and monazite as accessory minerals. The retrograde stage is characterized by alkali feldspar, clinozoisite–zoisite–sericite, calcite, and quartz. Scheelite occurs in four ore-shoots distributed within the marble and at the marble–schist contact. The main ore body is 5–120 cm wide and contains an average of 4.8-wt.% WO₃, which occurs in the basal marble–schist contact. Fold hinges appear to control the location of high-grade scheelite. The late-stage gold mineralization contains bismite (Bi₂O₃), fluorine-bearing bismite, native bismuth, bismuthinite (Bi₂S₃), and joseite [Bi₄(Te,S)₃], and also chlorite, epidote, prehnite, chalcopyrite, and sphalerite. This gold–bismuth–tellurium mineralization exhibits a typical late character and occurs as a black fine-grained mineral assemblage controlled by conjugate brittle-ductile faults (and extensional fractures) that crosscut not only the banding in prograde skarn but also the retrograde alkali feldspar and clinozoisite–zoisite–sericite assemblage. The Au–Bi–Te-bearing minerals are intergrown with retrograde epidote, prehnite, chlorite, chalcopyrite, and sphalerite, indicating that gold mineralization at Bonfim is linked to a late-stage skarn event. The polymetallic nature of the Bonfim deposit can be used as an important guide for the exploration of this type of skarn deposit in the Borborema Province, which potentially contains significant new, undiscovered gold and polymetallic deposits.     

基于Windows Mobile的移动GIS研究

移动GIS能够弥补传统静态GIS的某些不足,因而正成为地理信息科学领域新的研究热点,而Windows Mobile作为微软进军移动设备领域的主要品牌,受到了人们越来越多的关注。介绍了Windows Mobile操作系统和移动GIS的有关概念,对在Windows Mobile系统上进行移动GIS开发需要解决的几个关键技术,特别是对空间数据建立分块分级索引的技术进行了研究和探讨,最后对系统实现做了有益的尝试。     

北祁连~河西地区重力变化特征分析

通过对北祁连～河西地区重力变化的分析，认为重力变化由缓慢下降发展为快速下降，并形成重力变化高梯度带，同时大面积地形变和断层水准变化显示为由急剧上升转变为缓慢下降，表明该地区已进入应力积累的中期阶段，应密切监视其发展变化     

泾阳4.8级地震前后泾阳地震台形变观测资料的异常分析

分析了泾阳地震台跨断层短水准及流动形变观测资料在 1998年 1月 5日泾阳MS4 .8地震前后的异常变化 .结果表明 ,该次地震前后泾阳台的形变资料出现了明显的短期异常及震后效应 .     

车载微波辐射计移动大气走航观测实验及初步应用

地基多通道微波辐射计能够实现大气温湿度廓线参数的实时观测与反演,在大气探测中已经得到了广泛的应用。但是,受到观测方式和数据反演算法的限制,目前主要应用于地面固定站点上空的大气参数遥感探测,无法实现大气参数的移动观测。因此,尝试将自主研制的地基多通道微波辐射计进行改进并安装在车载平台上,对车载微波辐射计移动大气观测可行性进行了验证。实验结果表明车载微波辐射计移动观测是可行的。此外,利用车载移动走航观测数据,对西安城市热岛效应和对流有效位能（CAPE）进行了分析。结果显示,移动走航观测能够用于观测城市热岛效应,西安中心区域比郊区温度高出约1.0℃左右,城市中心的大气对流有效位能也比郊区高出1000～2000J/kg。通过这次实验为微波辐射计的车载移动观测和应用进一步奠定了基础。     

利用不规则载荷模型分析马家岭流动水准异常

通过环境调查等手段,收集整理马家岭水准观测场地周边环境变化参数及岩土力学参数,运用不规则二维载荷模型计算荷载引起的水准高差变化。结果显示,霍山大峡谷漂流场地停车场的建设对马家岭水准观测有一定影响,影响量约为0.77mm,与实际观测高差0.70mm接近,研究结果从定量模拟的角度证实了马家岭流动水准异常为环境荷载变化引起的地面高差变化。     

A comparative analysis of enzyme leach and mobile metal ion selective extractions; case studies from glaciated terrain, northern Ontario

The enzyme leach and MMI (mobile metal ion) selective digestions are rapidly gaining popularity in the exploration community because of their successful track record in non-glaciated, arid and tropical climatic regions. Few successful case studies from high-latitude, temperate regions have been published to date. Also lacking is a comprehensive discussion of the constraints and limitations of these geochemical methods and how they affect the successful interpretation of selective-leach survey results in glaciated regions. This paper evaluates each method using specific examples from four case studies undertaken in the glaciated region of northern Ontario. The case studies clearly demonstrate that both the MMI and enzyme leach selective digestions provide the explorationist with useful information, which, when used in conjunction with other exploration tools, can assist with the identification of potential diamond drill targets. Notwithstanding this, the techniques do not appear to work well as ‘stand alone' methods. The importance of following strict sampling protocols and obtaining high-quality observational information on the sampling site and media collected cannot be overstressed. It is only by filtering out the many variables that arise in any sampling program that a sound interpretation of the data can be made. The case studies have drawn attention to some of the apparent shortfalls of the techniques. Of these, issues such as the ability to reproduce survey results from year to year and the recognition of anomalous element associations which specifically target blind mineralisation are probably those which require significant follow-up work. Clearly, additional case studies are required from the glaciated regions of the world to assist with the optimisation of geochemical response of MMI and enzyme leach selective extractions. The mechanisms responsible for the formation of surface geochemical anomalies over deeply buried mineralisation are not well understood. The observed patterns of geochemical response in surface soils and both shallow and deep ground waters over concealed mineralisation should assist with the development of new dispersion models.