GEOSCAN, résultats de la recherche

Menu GEOSCAN


TitreAlbitisation of detrital feldspars in the Scotian Basin: implications for the thermal evolution of the basin
TéléchargerTéléchargements
AuteurPe-Piper, G; Yang, X
SourceCommission géologique du Canada, Dossier public 7117, 2014, 496 pages, https://doi.org/10.4095/293609 (Accès ouvert)
Image
Année2014
ÉditeurRessources naturelles Canada
Documentdossier public
Lang.anglais
DOIhttps://doi.org/10.4095/293609
Mediaen ligne; numérique
Formatspdf
ProvinceRégion extracotière de l'est
Lat/Long OENS -64.0000 -53.0000 45.0000 43.0000
Sujetsgrès; lithologie; pétrographie; pétrologie du sediment; minéraux détritiques; albite; albitisation; débris; potassium; feldspath; plagioclase; altération thermique; antecedents thermiques; diagenèse; paragenèse; Crétacé inférieur; microscopie électronique à balayage; analyses par microscope électronique; faciès sédimentaires; lithostratigraphie; Puit Louisbourg J-47 ; Puit Kegeshook G-67 ; pétrologie ignée et métamorphique; géologie marine; sédimentologie; Mésozoïque; Crétacé
Illustrationslocation maps; photomicrographs; stratigraphic columns; tables
ProgrammeAnalyse de bassin et ressources géoscientifiques, Géoscience en mer
Diffusé2014 02 14
Résumé(disponible en anglais seulement)
Diagenesis of K-feldspar and plagioclase are among the most significant changes occurring in sandstones during burial diagenesis. Sixteen representative samples at various depths from eight exploratory wells in the Scotian Basin were selected for detailed study of the diagenesis of the detrital feldspars, to evaluate the roles played by sedimentary facies (which influence porosity and permeability), geographic location (controlling the type of detrital supply), burial depth, temperature and salinity as recorded by fluid inclusions, and the structural setting of the sandstones. K-feldspar authigenesis starts at ~1900 m depth as K-feldspar overgrowths on detrital K-feldspars, or as cement that fills fractures in fractured K-feldspars, and continue to 3000 m. Albitization of Kfeldspar also starts at ~1900 m, with diagenetic albite following weakness paths and at greater depths, K-feldspar disappears through dissolution and/or replacement by ferroan calcite ± ankerite. K-feldspars disappear between 3,800 and 4,500 m. Detrital plagioclase is either oligoclase or albite. Early patches of diagenetic albite in detrital albite grains give way with depth to albite pseudomorphs or partially dissolved albite grains, containing large pores. Albite pseudomorphs predate late ankerite cement. Detrital oligoclase is first replaced at depths >3,700 m by diagenetic albite as overgrowths or irregular patches with straight crystal outlines. Diagenetic albite is much more abundant in thick sandstone units than in thin sandstone beds with interbedded mudstone, probably because such sandstones were pathways for flux of basinal fluids. It is more abundant, in the same facies and depth, in the Thebaud-Glenelg fields, where fluid inclusions in silica and carbonate cements are ~21% NaCl compared with the eastern part of the basin where fluid inclusions are ~10% NaCl and probably a little cooler. Dissolution of K-feldspar seems predominantly controlled by burial depth, but is most severe in permeable thick sandstone units.
Résumé(Résumé en langage clair et simple, non publié)
Le rapport décrit en détail la formation de porosité secondaire dans le bassin Scotian observable grâce à l'altération des feldspaths. On profite de la présence de feldspaths dans les grains de roches volcaniques. Il est ainsi possible d'interpréter l'effet de la température, de la pression et de l'écoulement des fluides sur la transformation des feldspaths. Un article scientifique connexe explorera plus à fond les implications de ces données.
GEOSCAN ID293609