Urban geology: Glasgow's hidden industrial heritage     

MICHAEL A. E. BROWNE  REW A. McMILLAN  IAN H. FORSYTH 《Geology Today》1986,2(3):74-78

The growth of Glasgow from a small town into a heavily industrialised conurbation depended greatly on its local geological riches. Extensive mining and quarrying of a range of minerals took place from the 18th century onwards. The early underground stoop and room (pillar and stall) workings, and the backfilled quarries, together with variably consolidated natural superficial deposits, have bequeathed to the city a heritage of unwanted engineering problems which cannot easily be quantified. Recent work by the British Geological Survey (BGS) illustrates the scale of both geological and man-made problems.  相似文献   

''Cosmogenic ¹⁰Be ages on the Pomeranian Moraine, Poland'': Comments     

MICHAEL HOUMARK-NIELSEN  SVANTE BJÖRCK  BARBARA WOHLFARTH 《Boreas: An International Journal of Quaternary Research》2006,35(3):600-604

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Fayalitic olivine in matrix of the Krymka LL3.1 chondrite: Vapor-solid growth in the solar nebula     

MICHAEL K. WEISBERG  MICHAEL E. ZOLENSKY  MARTIN PRINZ 《Meteoritics & planetary science》1997,32(6):791-801

Abstract— Fayalitic olivine (Fa_54–94) is a ubiquitous component in the matrix of Krymka (LL3.1) as well as in other highly unequilibrated chondrites (ordinary and carbonaceous). In Krymka, the fayalitic olivine has an unusual anisotropic platy morphology that occurs in at least five types of textural settings that can be characterized as: (1) isolated platelets, (2) clusters of platelets, (3) euhedral to subhedral crystals, (4) overgrowths of platelets on forsteritic olivine, and (5) fluffy (porous) aggregates. From transmission electron microscope (TEM) investigation, the direction of elongation of the platy olivine overgrowths on forsteritic olivine substrates is along the c axis and in most cases it corresponds with the c axis of the substrate olivine, which suggests that the fayalitic olivine grew in this unusual morphology and is not a replacement product of preexisting material. The fayalitic olivine in the matrix of Krymka is compositionally similar to olivine with platy morphology in the matrix of some CV3 chondrites and both have similar Fe/Mn ratios, but important morphological differences indicate that their relationship needs to be explored further. Textural and compositional data indicate that the fayalitic olivine in the matrix of Krymka, as well as in some other unequilibrated ordinary chondrites, formed prior to final lithification of the meteorite and probably prior to parent body accretion. We find that formation of the fayalitic olivine by vapor-solid growth provides the best explanation for our observations and data and is the only feasible mechanism for the formation of fayalitic olivine in the matrix of Krymka. We propose that the fayalitic olivine formed by vaporization and recondensation of olivine rich-dust, during a period of enhanced dust/gas ratio in the nebula.  相似文献   

Aerosol optical depth at ALOMAR Observatory (Andøya, Norway) in summer 2002 and 2003     

CARLOS TOLEDANO  VICTORIA CACHORRO  ALBERTO BERJÓN  MAR SORRIBAS  RICARDO VERGAZ  ÁNGEL DE FRUTOS  MANUEL ANTÓN  MICHAEL GAUSA 《Tellus. Series B, Chemical and physical meteorology》2006,58(3):218-228

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Melt Generation and Fluid Flow in the Thermal Aureole of the Bushveld Complex   总被引：2，自引：0，他引：2  

HARRIS  NIGEL; McMILLAN  ANDY; HOLNESS  MARIAN; UKEN  RON; WATKEYS  MIKE; ROGERS  NICK; FALLICK  ANTHONY 《Journal of Petrology》2003,44(6):1031-1054

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  相似文献   

The Lower Permian Wasp Head Formation,Sydney Basin: high‐latitude,shallow marine sedimentation following the late Asselian to early Sakmarian glacial event in eastern Australia     

MICHAEL C. RYGEL  CHRISTOPHER R. FIELDING  KERRIE L. BANN  TRACY D. FRANK  LAUREN BIRGENHEIER  STUART C. TYE 《Sedimentology》2008,55(5):1517-1540

The Lower Permian Wasp Head Formation (early to middle Sakmarian) is a ～95 m thick unit that was deposited during the transition to a non‐glacial period following the late Asselian to early Sakmarian glacial event in eastern Australia. This shallow marine, sandstone‐dominated unit can be subdivided into six facies associations. (i) The marine sediment gravity flow facies association consists of breccias and conglomerates deposited in upper shoreface water depths. (ii) Upper shoreface deposits consist of cross‐stratified, conglomeratic sandstones with an impoverished expression of the Skolithos Ichnofacies. (iii) Middle shoreface deposits consist of hummocky cross‐stratified sandstones with a trace fossil assemblage that represents the Skolithos Ichnofacies. (iv) Lower shoreface deposits are similar to middle shoreface deposits, but contain more pervasive bioturbation and a distal expression of the Skolithos Ichnofacies to a proximal expression of the Cruziana Ichnofacies. (v) Delta‐influenced, lower shoreface‐offshore transition deposits are distinguished by sparsely bioturbated carbonaceous mudstone drapes within a variety of shoreface and offshore deposits. Trace fossil assemblages represent distal expressions of the Skolithos Ichnofacies to stressed, proximal expressions of the Cruziana Ichnofacies. Impoverished trace fossil assemblages record variable and episodic environmental stresses possibly caused by fluctuations in sedimentation rates, substrate consistencies, salinity, oxygen levels, turbidity and other physio‐chemical stresses characteristic of deltaic conditions. (vi) The offshore transition‐offshore facies association consists of mudstone and admixed sandstone and mudstone with pervasive bioturbation and an archetypal to distal expression of the Cruziana Ichnofacies. The lowermost ～50 m of the formation consists of a single deepening upward cycle formed as the basin transitioned from glacioisostatic rebound following the Asselian to early Sakmarian glacial to a regime dominated by regional extensional subsidence without significant glacial influence. The upper ～45 m of the formation can be subdivided into three shallowing upward cycles (parasequences) that formed in the aftermath of rapid, possibly glacioeustatic, rises in relative sea‐level or due to autocyclic progradation patterns. The shift to a parasequence‐dominated architecture and progressive decrease in ice‐rafted debris upwards through the succession records the release from glacioisostatic rebound and amelioration of climate that accompanied the transition to broadly non‐glacial conditions.  相似文献   

Ensembles of global ocean analyses for seasonal climate prediction: impact of temperature assimilation     

PHILIPPE ROGEL  ANTHONY T. WEAVER  NICOLAS DAGET  SOPHIE RICCI  ERIC MACHU † 《地球，A辑:动力气象学与海洋学》2005,57(3):375-386

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Crystal-Mush Compaction and the Origin of Pegmatitic Segregation Sheets in a Thick Flood-Basalt Flow in the Mesozoic Hartford Basin, Connecticut   总被引：9，自引：4，他引：5  

PHILPOTTS  ANTHONY R.; CARROLL  MAUREEN; HILL  JAMES M. 《Journal of Petrology》1996,37(4):811-836

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  相似文献   

REE-Depleted Leucogranites, Black Hills, South Dakota: a Consequence of Disequilibrium Melting of Monazite-Bearing Schists   总被引：4，自引：1，他引：3  

NABELEK  PETER. I.; GLASCOCK  MICHAEL. D. 《Journal of Petrology》1995,36(4):1055-1071

Two isotopically distinct but otherwise chemically similar leucogranitesuites in the Proterozoic Horney Peak Granite, Black Hills,South Dakota, have contrasting light rare earth element (LREE)concentrations. Most samples of a relatively ¹⁸O-depleted suitehave LREE- enriched, chondrite-normalized patterns, typicalof melts derived from metasedimentary protoliths, whereas allsamples of the regionally significant, relatively ¹⁸O-enrichedsuite have LREE-depleted patterns. The latter patterns are interpretedto have resulted from disequilibrium melting of schists. Monaziteand perhaps other accessory minerals remained armored by biotiteand garnet which did not partake in the muscovite dehydration-meltingreaction that produced LREE-depleted melts. The REE concentrationsin the LREE-depleted samples are below saturation levels formonazite at reasonable melting temperatures and melt water contents,whereas the REE concentrations in the LREE-enriched samplesyield 700–800C monazite saturation temperatures, reasonablefor biotite dehydration-melting reactions. LREE depletions,analogous to those in the LREE-depleted granites, are also foundin leucosomes of partially molten schists, thought to be theprotolith for the granite. In contrast, the melanosomes holdthe accessory minerals and bulk of the LREEs. KEY WORDS: accessory minerals; leucogranites; Black Hills; monazite; partial melting ^*Corresponding author at Department of Geological Sciences, University of Missouri. Telephone: 314-884-6463. Fax: 314-882-5458. e-mail: geolpin{at}showme.missouri.edu.  相似文献   

The Panafrican Stratoid Granites of Madagascar: Alkaline Magmatism in a Post-Collisional Extensional Setting   总被引：6，自引：0，他引：6  

NDLEC  ANNE; STEPHENS  EDRYD W.; FALLICK  ANTHONY E. 《Journal of Petrology》1995,36(5):1367-1391

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  相似文献