Fracturing and near-surface diagenesis of a silicified miocene deltaic sequence : the montjuïc hill (Barcelona)
Cantarero, Irene (Universitat de Barcelona. Departament de Mineralogia, Petrologia i Geologia Aplicada)
Parcerisa i Duocastella, David (Universitat Politècnica de Catalunya. Departament d'Enginyeria Minera, Industrial i TIC)
Plata, Maria Alexandra (Universitat de Barcelona. Departament de Mineralogia, Petrologia i Geologia Aplicada)
Gómez-Gras, David (Universitat Autònoma de Barcelona. Departament de Geologia)
Gomez-Rivas, Enrique (Universitat de Barcelona. Departament de Mineralogia, Petrologia i Geologia Aplicada)
Martín-Martín, Juan Diego (Universitat de Barcelona. Departament de Mineralogia, Petrologia i Geologia Aplicada)
Travé i Herrero, Anna (Universitat de Barcelona. Departament de Mineralogia, Petrologia i Geologia Aplicada)

Date:	2020
Abstract:	Near-surface diagenesis has been studied in the Langhian siliciclastic rocks of the Montjuïc Hill (Barcelona Plain) by means of petrographical (optical and cathodoluminescence) and geochemical (electron microprobe, δO, δC, δS andSr/Sr) analyses. In the hill, these rocks are affected by strong silicification, but the same unit remains non-silicified at depth. The results reveal that fracturing took place after lithification and during uplift. Fracture cementation is clearly controlled by the previous diagenesis of the host rock. In non-silicified areas, cementation is dominated by calcite, which precipitated from meteoric waters. In silicified areas, fractures show multiepisodic cementation produced firstly by barite and secondly by silica, following the sequence opal, lussatite, chalcedony, and quartz. Barite precipitated only in fractures from the mixing of upflowing seawater and percolating meteoric fluids. The presence of silica stalactites, illuviation, and geopetal structures, and δO values indicate that silica precipitation occurred in the vadose regime from low-temperature percolating meteoric fluids, probably during a glacial period. Moreover, the presence of alunite suggests that silica cement formed under acidic conditions. Karst features (vugs and caverns), formed by arenisation, reveal that silica was derived from the dissolution of surrounding silicified host rocks.
Grants:	Ministerio de Economía y Competitividad CGL2015-66335-C2-1-R Agencia Estatal de Investigación PGC-2018-093903-B-C22 Agència de Gestió d'Ajuts Universitaris i de Recerca 2017/SGR-824
Rights:	Aquest document està subjecte a una llicència d'ús Creative Commons. Es permet la reproducció total o parcial, la distribució, la comunicació pública de l'obra i la creació d'obres derivades, fins i tot amb finalitats comercials, sempre i quan es reconegui l'autoria de l'obra original.
Language:	Anglès
Document:	Article ; recerca ; Versió publicada
Subject:	Silicification ; Meteoric diagenesis ; Fractures ; Deltaic sequence ; Karst ; Glacial period
Published in:	Minerals, Vol. 10, Issue 2 (February 2020) , art. 135, ISSN 2075-163X

DOI: 10.3390/min10020135

22 p, 5.3 MB

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