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Diagenesis of a mixed siliciclastic/evaporitic sequence of the Middle Muschelkalk (Middle Triassic), the Catalan Coastal Range, NE Spain
Author(s) -
MORAD S.,
ALAASM I. S.,
LONGSTAFFE F. J.,
MARFIL R.,
ROS L. F. DE,
JOHANSEN H.,
MARZO M.
Publication year - 1995
Publication title -
sedimentology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.494
H-Index - 108
eISSN - 1365-3091
pISSN - 0037-0746
DOI - 10.1111/j.1365-3091.1995.tb00407.x
Subject(s) - geology , anhydrite , geochemistry , sabkha , facies , dolomite , evaporite , diagenesis , calcite , carbonate , feldspar , meteoric water , illite , halite , gypsum , sedimentary rock , clay minerals , quartz , geomorphology , paleontology , structural basin , hydrothermal circulation , metallurgy , materials science
The Middle Muschelkalk (Middle Triassic) of the Catalan Coastal Range (north‐east Spain) comprises sandstone, mudstone, anhydrite and minor carbonate layers. Interbedded sandstones and mudstones which are dominant in the north‐eastern parts of the basin are terminal alluvial fan deposits. South‐westward in the basin, the rocks become dominated by interbedded evaporites and mudstones deposited in sabkha/mudflat environments. The diagenetic and pore water evolution patterns of the Middle Muschelkalk suggest a strong facies control. During eodiagenesis, formation of microdolomite, anhydrite, baryte, magnesite, K‐feldspar and mixed‐layer chlorite/smectite was favoured within and adjacent to the sabkha/mudflat facies, whereas calcite, haematite, mixed‐layer illite/smectite and quartz formed mainly in the alluvial facies. Low δ 18 O SMOW values for microdolomite (+23.7 to +28.4%) and K‐feldspar overgrowths (+17.3 to +17.7%) suggest either low‐temperature, isotopic disequilibrium or precipitation from low‐ 18 O porewaters. Low‐ 18 O waters might have developed, at least in part, during low‐temperature alteration of volcanic rock fragments. During mesodiagenesis, precipitation of quartz overgrowths and coarse dolomite occurred in the alluvial sandstones, whereas recrystallization of microdolomite was dominant in the sabkha/mudflat facies. The isotopic compositions of these mesogenetic phases reflect increasing temperature during burial. Upon uplift and erosion, telogenetic calcite and trace haematite precipitated in fractures and replaced dolomite. The isotopic composition of the calcite (δ 18 O SMOW =+21.5 to +25.6%o; δ 13 C= 7.7 to ‐ 5.6%o) and presence of haematite indicate infiltration of meteoric waters.