Lithological and Structural Controls on Regional 3-D Fluid Flow Patterns during Greenschist Facies Metamorphism of the Dalradian of the SW Scottish Highlands   总被引：3，自引：0，他引：3  

SKELTON  ALASDAIR D. L.; GRAHAM  COLIN M.; BICKLE  MIKE J. 《Journal of Petrology》1995,36(2):563-586

Greenschist facies metabasite sills enclosed within phyllitesand psammites of the Dalradian Supergroup of the SW ScottishHighlands have been used as quantitative sensors of fluid flow,from which ‘fossil’ fluid flow-paths have been mapped.Infiltration of H₂O–CO₂ fluid caused carbonation of themetabasite assemblage. Consequently, metabasite sills have developeda characteristic asymmetric zonation of reacted (carbonate-bearing)margins and unreacted (carbonate-absent) interiors. Reactionfront advection theory has been used to constrain the time-integratedfluid flux and flow direction in one dimension, for each sill,from the widths of the reacted margins. Three-dimensional fluxesand flow directions have been constrained from one-dimensionalfluxes by geometrical computation, and regional fluid flow patternshave been deduced. On a regional scale, fluid flow was channelled through phyllitesand focused towards the axial zone of major antiformal foldstructures. Fluid flow was channelled through the 6 km thickArdrishaig Phyllites, within which fluid fluxes were found toincrease exponentially with proximity to the axial surface ofthe Ardrishaig Anticline. Fluid flow through the psammites waslimited to narrow zones of intense deformation associated withmetabasic or phyllitic intercalations. Although time-integratedfluid fluxes were locally high (4 10² m³/m²), average fluxes(100 m¹/m²) are compatible with availability of fluid from underlyingdevolatilizing rocks. Complete isotopic homogenization of phyllites,psammites and metabasites within the axial region of the ArdrishaigAnticline is predicted by these high measured fluxes. KEY WORDS: 3-D flow; Dalradian; SW Scotland; greenschist facies; metabasites ^*Corresponding author. Telephone: 0131-650-5885 Fax: 0131-668-3184 E-mail: askelton{at}glg.ed.ac.uk  相似文献   

Temperatures of Granulite-facies Metamorphism: Constraints from Experimental Phase Equilibria and Thermobarometry Corrected for Retrograde Exchange   总被引：17，自引：7，他引：17  

PATTISON  DAVID R. M.; CHACKO  THOMAS; FARQUHAR  JAMES; MCFARLANE  CHRISTOPHER R. M. 《Journal of Petrology》2003,44(5):867-900

This study assesses temperatures of formation of common granulitesby combining experimental constraints on the P–T stabilityof granulite-facies mineral associations with a garnet–orthopyroxene(Grt–Opx) thermobarometry scheme based on Al-solubilityin Opx, corrected for late Fe–Mg exchange. We appliedthis scheme to 414 granulites of mafic, intermediate and aluminousbulk compositions. Our findings suggest that granulites aremuch hotter than traditionally assumed and that the P–Tconditions of the amphibolite–granulite transition portrayedin current petrology textbooks are significant underestimatesby over 100°C. For aluminous and intermediate granulites,mean corrected temperatures based on our method are 890 ±17 and 841 ± 11°C, respectively (uncertainties reportedas 95% confidence limits on the mean), consistent with minimumtemperatures for orthopyroxene production by fluid-absent partialmelting in these bulk compositions. In contrast, mean temperaturesbased on Grt–Opx Fe–Mg exchange equilibria, usingthe same thermodynamic data, are 732 ± 22 and 723 ±11°C, respectively, well below the minimum temperaturesfor Opx stability. For mafic granulites, the mean correctedtemperature using our method is 816 ± 12°C, similarto the mean temperature of 793 ± 13°C from Fe–Mgexchange. Reasons for the differences between the mafic granulitesand aluminous–intermediate granulites are unclear butmay be due to the lower Al concentrations in Opx in the maficrocks and possible deficiencies in the thermodynamic modellingof these low concentrations. We discuss a number of well-knowngranulite terrains in the context of our findings, includingthe Adirondacks, the Acadian granulites of New England, theincipient charnockites of southern India and Sri Lanka, andthe Kerala Khondalite Belt. Our findings carry implicationsfor thermotectonic models of granulite formation. A computerprogram to perform our thermobarometry calculations, RCLC, isavailable from the Journal of Petrology website at http://www.petrology.oupjournals.orgor from the authors at http://www.geo.ucalgary.ca/~pattison/drm_pattison-rclc.htm. KEY WORDS: granulite-facies metamorphism; thermobarometry; garnet; orthopyroxene  相似文献   

Indian Ocean tsunamis: environmental and socio-economic impacts in Langkawi, Malaysia     

MICHAEL BIRD  SUSAN COWIE  REA HAWKES†  BEN HORTON†  COLIN MACGREGOR  JIN EONG ONG‡  AILEEN TAN SHAU HWAI§  TEH TIONG SA¶  ZULFIGAR YASIN§ 《The Geographical journal》2007,173(2):103-117

We report the results of a study of the physical characteristics and socio-economic impacts of the Indian Ocean Tsunami of 26 December 2004 on the tourist island of Langkawi, Malaysia. In comparison with many other locations struck by the tsunami, the immediate physical and socio-economic impacts in Langkawi were relatively minor. A detailed survey of the watermark and ground elevations was undertaken in the worst affected area between Sungei Kuala Teriang and Sungei Kuala Melaka. Here, the tsunami reached a maximum elevation of 4.29 m as it crossed the coast, with a maximum flow depth of 2.0 m and a very consistent run-up elevation relative to mean sea level of 300 ± 10 cm. The tsunami inundated inshore areas for 300 m and penetrated inland along creeks for 500–1000 m. Structural damage to buildings was confined to within 50–150 m of the shoreline where about 10% of the houses were completely destroyed and 60–70% suffered significant structural damage. Damage was particularly severe in areas where there was no engineered coastal protection, but while coastal revetments did provide enhanced protection for houses at the waterfront, the coastline in the study area appeared to be more heavily impacted than elsewhere in Langkawi because wave energy was focused on the area by offshore breakwaters built to protect the Langkawi port and airport. Emergency response after the tsunami was rapid and efficient but would have been improved if the local police station had not been rendered inoperative by the first wave, and if a mechanism had been in place to ensure that informal advance warnings transmitted between Phuket (Thailand), Langkawi and Penang (Malaysia) by tourist operators could have been more widely disseminated.  相似文献   

Rhizoliths in terrestrial carbonates: classification, recognition, genesis and significance   总被引：13，自引：0，他引：13  

COLIN F. KLAPPA 《Sedimentology》1980,27(6):613-629

Rhizoliths are defined as organosedimentary structures resulting in the preservation of roots of higher plants, or remains thereof, in mineral matter. They are abundant and characteristic features of Quaternary terrestrial carbonates (calcretes and aeolianites) from coastal regions of the western Mediterranean. Field and petrographic observations indicate that five basic types of rhizoliths can be recognized: (1) root moulds, which are tubular voids that outline positions of former, now decayed roots; (2) root casts, which are sediment- and/or cement-filled root moulds; (3) root tubules, which are cemented cylinders around root moulds; (4) rhizocretions s.s., which are pedodiagenetic mineral accumulations (here low magnesian calcite) around living or dead plant roots; and (5) root petrifactions, which are mineral impregnations or mineral replacements of organic matter whereby anatomical features of roots have been preserved partially or totally. Apart from rhizoliths themselves, roots of higher plants are responsible for the formation of numerous and characteristic features of pedogenetically affected terrestrial carbonates. Plant roots are responsible for, or contribute to, the formation of alveolar textures, in situ brecciation (rhizobrecciation) textures, horizontal sheet cracks, vertically elongate glaebules (concretionary soil structures) and micritization (rhizomicritization) within terrestrial carbonates. Rhizoliths, together with the above features, are products of pedodiagenesis. More significantly, rhizoliths and related features are indicators of palaeosols and hence of subaerial vadose environments in ancient (post-Silurian) successions.  相似文献   

Paleoclimate and Paleoenvironment of Gonghe Basin, Qinghai-Tibet Plateau, During the Lastdeglacial: Weathering, Erosion and Vegetation Cover Affect Clay Mineral Formation     

SUN Qingfeng  Christophe COLIN 《《地质学报》英文版》2014,88(2):647-660

With the analysis of the sources and formation mechanism of the clay minerals in the sediment core from the Dalianhai lake in the Gonghe Basin,northeastern Tibet-Qinghai Plateau,clay mineral composition proxies,grain-size and carbonate contents have been employed for high-resolution study in order to reconstruct East Asian Summer Monsoon （EASM） over the northeastern Tibet-Qinghai Plateau during the lastdeglacial.The study also extended to establish a relationship between vegetation cover changes and erosion during the last 14.5 ka with pollen record and clay mineral proxies.Smectite/kaolinite and smectite/（illite＋chlorite） ratios allow us to assess hydrolysis conditions in lowlands and/or physical erosion process in highlands of the Gonghe Basin.Before 12.9 Cal ka BP,both mineralogical ratios show low values indicative of strong physical erosion in the basin with a dominant cold and dry phase.After 12.9 Cal ka BP,an increase in both mineralogical ratios indicates enhanced chemical weathering in the basin associated with a warm and humid climate.The beginning of Holocene is characterized by high smectite/（illite＋chlorite） and smectite/kaolinite ratios that is synchronous as with deposition of many peat laminae,implying the best warm and humid conditions specifically between 8.0 to 5.5 Cal ka BP.The time interval after 5.0 Cai ka BP is characterized by a return to high physical erosion and low chemical weathering with dry climate conditions in the basin.Comparing variations of clay mineral assemblages with previous pollen results,we observe a rapid response in terms of chemical weathering and physical erosion intensity to a modification of the vegetation cover in the basin.  相似文献   

Thermal resonance of the atmosphere to SST anomalies. Implications for the Antarctic circumpolar wave     

A. COLIN DE VERDIÈRE  M. L. BLANC 《地球，A辑:动力气象学与海洋学》2001,53(3):403-424

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The Great Barrier Reef: a 700 000 year diagenetic history     

COLIN J. R. BRAITHWAITE  LUCIEN F. MONTAGGIONI† 《Sedimentology》2009,56(6):1591-1622

A deep borehole through Ribbon Reef 5 in the Great Barrier Reef off north‐eastern Australia has identified a variety of cements, including epitaxial, radial prismatic and spherular aragonite, together with blocky, prismatic and fibrous calcite. These cements are discontinuously arranged within the sequence that consists predominantly of grainstones but locally includes clotted muddy and filamentous textures that may be of microbial origin. Calcite cements vary in morphology with groups of crystals that include acute scalenohedral, rhombohedral and flattened concordant terminations; these show varying densities of inclusions that locally define growth zones and in some terminations divide in the manner of ‘split crystals’ to form fibrous fringes. Morphological changes in calcite are inferred to reflect changes in water chemistry and crystal growth rates at the time of growth, allied to their relationship to the palaeo‐water table, and linked in turn to changes in sea‐level. Neomorphism and dissolution are widespread and variations in the severity of both imply response to the degree of undersaturation of pore waters that at times were probably balanced within very narrow limits. A total of 10 depositional units are identified. Those units at the base of the borehole reflect deposition and diagenesis within a marine environment. The influence of meteoric waters, indicated by stable isotopes, is first apparent at the top of Unit 1 and in Unit 2 (184 to 155 m below sea floor). Petrographic evidence of vadose conditions appears at the tops of Unit 3 (131 to 99 m below sea floor). Units 4 to 8, all deposited under marine conditions, provide isotopic evidence of meteoric or mixing‐zone waters and petrographic indicators of vadose conditions, typically at the top of the units. Evidence indicates that in Unit 5 the water table was mobile and Units 6a, 6b, 7 and 8, all characterized by ultraviolet fluorescent cements, are capped by sub‐aerial erosion surfaces. Unit 9 (the Holocene) reflects the recent re‐establishment of marine conditions. The extent of alteration of the entire sequence reflects the substantial and pervasive influence of meteoric waters. This effect is interpreted as a result of a greater rainfall and river flow from the mainland during early and late stages of interstadial periods. The study reflects progress in the ability to recognize the diagenetic signal generated by sea‐level change. However, whereas the isotopic results reflect the changing relationships between vadose and phreatic zones in groundwater systems beneath successive emergent surfaces, their correspondence with petrographic features is expressed only weakly and commonly lacks the systematic sequential overprinting implied by the distribution of cathodoluminescent zones of cements in many ancient limestones.  相似文献   

¹⁰Be chronology of the last deglaciation of County Donegal, northwestern Ireland     

JORIE CLARK  A. MARSHALL McCABE  CHRISTOPH SCHNABEL  PETER U. CLARK  STEWART FREEMAN  COLIN MADEN  SHENG XU 《Boreas: An International Journal of Quaternary Research》2009,38(1):111-118

A well-preserved moraine on the northern coast of County Donegal, Ireland, has played a critical role in our understanding of the glacial history of this sector of the Irish Ice Sheet (IIS). Because of a lack of numerical dating of the moraine, however, previous interpretations of its age and significance to the glacial history of this region have varied widely. Here we report eight in situ cosmogenic ¹⁰Be ages on boulders sampled from the moraine. Two of these ages are outliers, with the remaining six ranging from 18.8±1.0 ¹⁰Be kyr to 20.9±1.3 ¹⁰Be kyr, with an uncertainty-weighted mean age of 19.4±0.3 ¹⁰Be kyr (19.4±1.2 kyr accounting for production rate uncertainty). Our results confirm one previous ¹⁰Be age obtained from the moraine, with the combined data ( n =7) constraining the age of initial deglaciation of the IIS from its LGM position on the continental shelf to be 19.3±0.3 ¹⁰Be kyr (19.3±1.2 kyr accounting for production rate uncertainty). These ages are in excellent agreement with calibrated ¹⁴C ages that constrain retreat of the IIS margin from the continental shelf elsewhere in northwestern and western Ireland and the Irish Sea Basin associated with the start of the Cooley Point Interstadial (≥20–≤18.2 cal. kyr BP), suggesting widespread deglaciation of the IIS ∼19.5–20 kyr ago.  相似文献   

A Mark 1 Geographical Analysis Machine for the automated analysis of point data sets     

STAN OPENSHAW  MARTIN CHARLTON  COLIN WYMER  ALAN CRAFT 《International journal of geographical information science》2013,27(4):335-358

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Mineralogical, petrological, and petrogenetic analysis of felsic intrusive rocks at the Sisson Brook W-Mo-Cu deposit, west-central New Brunswick     

ZHANG Wei  Christopher R.M. MCFARLANE  Dave LENTZ 《《地质学报》英文版》2013,87(Z1):831-834

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