Melt Generation and Fluid Flow in the Thermal Aureole of the Bushveld Complex

Granite sheets emplaced into the migmatite zone of the easterncontact aureole of the Bushveld Complex resulted from fluid-enhanced,incongruent biotite melting of the underlying Silverton Formationshales during prograde metamorphism. Ba concentrations are extremein both the sheets (>1000 ppm) and the hornfels (>800ppm) into which they have been emplaced. We conclude that aBa-rich, hydrothermal fluid induced melting in the aureole,and that fluid transport of Ba²⁺, and to a lesser extent, Sr²⁺and Eu²⁺, persisted in the melt zones under subsolidus conditions.Sr-isotope systematics from high-Ba localities define an errorchronof 2161 ± 106 Ma with an initial (⁸⁷Sr/⁸⁶Sr) ratio of0·705 ± 0·001. Metasedimentary rocks unaffectedby fluid infiltration were homogenized at the same time butwith an increased initial ratio, suggesting that whereas isotopehomogenization was achieved between outcrops permeated by fluids,there is no evidence of regional homogenization. Oxygen-isotopecompositions of psammitic metasediments in the aureole are uncorrelatedwith distance from the contact, suggesting the infiltratingfluid equilibrated isotopically with the metasediments. Theirelevated     

Crystal-Mush Compaction and the Origin of Pegmatitic Segregation Sheets in a Thick Flood-Basalt Flow in the Mesozoic Hartford Basin, Connecticut

Where the Holyoke flood-basalt flow in the Mesozoic HartfordBasin in Connecticut is thick and contains coarse-grained, horizontalsegregation sheets in its central part, the lower part of theflow is strongly depleted in incompatible elements; where theflow is thin and contains no segregation sheets it is homogeneousthroughout. This chemical variation can be explained only throughcompaction of the partly crystallized basalt. The compositionof the segregation sheets shows that they separated from thebasalt following only 33% crystallization. The segregation sheets,however, are clearly intrusive into the basalt, which must thereforehave already formed a crystal mush with finite strength at thislow degree of crystallinity. The incompatible element concentrationsindicate that the partly crystallized basalt underwent as muchas 28% compaction in the lowest 60 m of the flow. Between 60and 130 m above the base of the flow, the crystal mush becamedilated, and eventually ruptured with formation of the segregationsheets. No segregation sheet has a composition indicating separationafter more than 33% crystallization of the basalt. This is interpretedto indicate that compaction ceased at this stage because ofthe increasing strength of the mush and the increasing densityof the fractionating interstitial liquid KEY WORDS: crystal-mush compaction; segregation shtets; flood basalt; tholeiitie; Connecticut ^*e-mail: philpotts{at}geol.uconn.edu     

The Panafrican Stratoid Granites of Madagascar: Alkaline Magmatism in a Post-Collisional Extensional Setting

A major alkali province of late Panafrican age occupies centralMadagascar and takes the form of a thick sequence of ‘stratoid’(sheet-like)granites emplaced in a mid-crustal gneissic basement This alkalinemagmatism has been interpreted as a consequence of extensionaltectonics accompanying the collapse of the Mozambique belt.The rocks belong to three petrographic types: subsolvus granites,hypersolvus alkaline granites and syenites. Major and traceelement analyses have typical A-type characteristics. Two distinctmagmatic suites are recognized: a mildly alkaline suite includingall the subsolvus granites and a strongly alkaline suite includingthe hypersolvus alkaline granites and the syenites. We proposethat the mildly alkaline suite was derived from a granodioriticcrustal protolith. Some of the strongly alkaline granites andthe quartz syenites display low ¹⁸O isotopic signatures of around+6.The parental magmas for this suite are most probably of mantlederivation. The more evolved compositions are consistent withcrystal fractionation processes. Contemporaneous alkaline silicicplutonismoccurs in many parts of the Panafrican belt of Eastern Africa;however, sheet-like intrusions have rarely been described. Asa large-scale province, the nearest analogues of the stratoidgranites of Madagascar are the rapakivi granites of earlierProterozoic age in Scandinavia and Greenland. KEY WORDS: alkaline granite; Madagascar; Panafrican; pastcollisional magmatism ^*Corresponding author     

基于神经网络的单元自动机CA及真实和忧化的城市模拟

提出了一种基于神经网络的单元自动机（ＣＡ）。ＣＡ已被越来越多地应用在城市及其它地理现象的模拟中。ＣＡ模拟所碰到的最大问题是如何确定模型的结构和参数。模拟真实的城市涉及到使用许多空间变量和参数。当模型较复杂时，很难确定模型的参数值。本模型的结构较简单，模型的参数能通过对神经网络的训练来自动获取。分析表明，所提出的方法能获得更高的模拟精度，并能大大缩短寻找参数所需要的时间。通过筛选训练数据，本模型还可以进行优化的城市模拟，为城市规划提供参考依据。     

运用社交网络分析淹水空间信息之关联性

随着社交网络的普遍发展,大量的讯息透过智能手机发布在个人的微博或其他社交网站。台湾地区的社交网站以脸书(Facebook)的使用量最大,平均每天有近千万笔的讯息量,大多数的讯息多以食衣住行或个人讯息为主,但从本研究所撷取自2010年至2015年的数据中显示,公众在社交网站所分享的信息中具有降雨、淹水或相关灾情的讯息,而这些讯息具有极高比例的正确性。由于社交网站无法提供私人讯息,故本研究将从社交信息中,以地点为单位撷取大量的数据信息再辅以语意关键词萃取出有关可作为淹水预判的讯息数据。为检核资料的可性度,本研究透过历史台风数据FLO-2D仿真重建淹水之空间信息进行检核。从研究比对分析中发现,经萃取后的公众信息其与灾害的关联性及正确性相当显着,故透过社交网站中大量的非结构讯息,透过语意及空间的转换,可萃取转化为防灾信息,对广域的都市治理而言,此一讯息将可作为预判区域淹水或防救灾情报之有效参考。     

Faceted garnets from sandstones of the Munising Formation (Cambrian), northern Michigan: petrographic evidence for their origin by intrastratal dissolution

Imbricate wedge marks (facets) on garnets in sandstones of the Cambrian Munising Formation of northern Michigan are associated with mouldic secondary porosity developed at the expense of garnet. Mouldic pores surrounding faceted garnets indicate that garnets in these sandstones have been affected by intrastratal dissolution (retreat of the mineral surface from its original boundaries) rather than by grain enlargement, which would be expected if garnet overgrowths had formed. The association of garnet facets with textural evidence of garnet dissolution proves that garnet facets form by intrastratal dissolution. These results confirm similar findings in other recent studies, and extend the geographic and stratigraphic range of proven occurrences of facet formation by intrastratal dissolution.     

休耕水稻田蓄水对土壤肥力影响试验

主要探讨水稻田休耕期间蓄水对休耕后土壤肥力之影响。选择两块水稻田区,在水稻收割后,将田区翻耕一次。一田区以人工连续灌溉,蓄存水量于田区;另一田区则为天然蓄水。在每一田区四边及中央处,以10cm为一层采取土样,取至60cm。再将每一层土样气干后,通过0.42mm筛网土样混合,分析田区同一层在不同时段与不同深度下之pH值、电导度值、有机质、全氮、有效磷、钙离子、镁离子、钾离子及钠离子之变化。试验结果显示:休耕后水稻根系腐化,造成土壤有机质以及有效磷显著的增加。蓄水后天然蓄水田区有机质和有效磷分别增加51%及88%,连续蓄水田区分别增加13%和69%。而天然蓄水田区镁、钾、钠分别降低35%、24%和47%,连续蓄水田区分别降低29%、14%及41%。