Growth and destruction of Bathonian silica nodules in the Western Pyrenees (France)

James, Valéry; Canérot, J.; Meyer, Aurelien G.; Biteau, Jean-Jacques

doi:10.1016/s0037-0738(99)00121-9

Cited by 7 publications

(3 citation statements)

References 5 publications

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“…After the death of organisms, the increasing pH controlled by decaying ectoderms facilitated the dissolution of metastable opaline spicules (cf. James et al 2000). Initial dissolution of the sponge spicules took place in the topmost metres of the sediment and continued during shallow burial, probably to a depth of about 200-250 m (cf.…”

Section: Discussionmentioning

confidence: 99%

Epigenetic silicification of the Upper Oxfordian limestones in the Sokole Hills (Kraków-Częstochowa Upland): relationship to facies development and tectonics

Matyszkiewicz¹,

Kochman²,

Rzepa³

et al. 2015

Acta Geologica Polonica

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ABSTRACT:Matyszkiewicz, J., Kochman, A., Rzepa, G., Gołębiowska, B., Krajewski, M., Gajdzik, K. and Żaba, J. 2015. Epigenetic silicification of the Upper Oxfordian limestones in the Sokole Hills (Kraków-Częstochowa Upland): relationship to facies development and tectonics. Acta Geologica Polonica, 65 (2), 181-203. Warszawa.A spectacular epigenetic silicification was encountered in the Oxfordian bedded limestones exposed in the Sokole Hills situated in the Kraków-Częstochowa Upland. The main epigenetic mineral is microcrystalline quartz accompanied by minor goethite, hematite, barite, galena and sphalerite. Locally, the mineralized limestones reveal Pb and Cu contents exceeding over 150 times the background values of these metals in unmineralized limestones.The epigenetic mineralization of the bedded limestones was probably a two-stage process. During the first, Early Cretaceous stage, silicified limestones formed at the erosional surface of a denuded carbonate complex. Such silicification greatly limited the progress of the first karstification phase of the Upper Jurassic carbonates initiated in the Hauterivian. The sources of silica accumulated in the limestones were descending solutions enriched in silica derived from the weathering zone. This silicification affected the topmost part of the Upper Jurassic massive limestones and the deeper portions of the bedded limestones along the fracture systems and stylolites.Early Cretaceous tectonic activity generated new dislocations and re-opened the existing faults, which were subsequently filled with permeable Albian quartz sands. These openings became the migration pathways for ascending, warm, relict, sulphide-carrying hydrothermal solutions at the second formation stage of the epigenetic mineralization. The newly supplied silica from the Albian sands precipitated on the silicified limestones and, as concentric rims, on brecciated, early diagenetic cherts. The second-stage mineralization proceeded under phreatic conditions, presumably close to a fluctuating mixing zone of ascending, warm hydrothermal solutions and descending cold groundwaters. The brecciated cherts acting as silica crystallization nuclei indicate that the last mineralization stage probably followed the final phase of Cenozoic faulting.

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Section: Discussionmentioning

confidence: 99%

Epigenetic silicification of the Upper Oxfordian limestones in the Sokole Hills (Kraków-Częstochowa Upland): relationship to facies development and tectonics

Matyszkiewicz¹,

Kochman²,

Rzepa³

et al. 2015

Acta Geologica Polonica

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“…Spherical nodules reflect silica supplied by diffusion, while elongated ones are evolved when silica is supplied by advection (McBride, Picard, & Folk, 1994). The great majority of the previous works revealed that the cherts were formed diagenetically by the replacement of their host limestones (e.g., Abd El-Hameed et al, 1997; Bustillo et al, 2009;Genedi, 1998;James, Canerot, Meyer, & Biteau, 2000;Knauth, 1994;Kwiatkowski, 2005;Lawrence, 1994;Madsen & Stemmerik, 2010;Maliva & Siever, 1989a;McBride et al, 1999;Shaaban, 2004;Snavely et al, 1979). A few workers concluded that cherts are of syngenetic origin (e.g., Keheila, 2000;Lindgreen & Jakobsen, 2012).…”

Section: Mode Of Emplacement (Syngenetic Versus Diagenetic)mentioning

confidence: 99%

Origin of chert within the Turonian carbonates of Abu Roash Formation, Abu Roash area, Egypt: Field, petrographic, and geochemical perspectives

Hussein

El‐Rahman

2019

Geological Journal

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This paper tries to elucidate the origin of the siliceous rocks (cherts) within the Turonian flint‐bearing chalky limestone member of Abu Roash Formation, Abu Roash area, north Western Desert, Egypt. Understanding the formation mechanism of the studied chert was gained through field and petrographic investigations, supplemented by geochemical analyses of both cherts and host Turonian carbonates. The field observations reveal that the chert is found in two forms: banded and nodular. The microscopic investigation determined that the cherts exhibit two types of silica: replacive silica (cryptocrystalline and microcrystalline quartz) and silica cement (length‐fast chalcedony and megaquartz). The chert texture corroborates that the examined authigenic silica was formed diagenetically by the replacement and void‐filling of the host carbonate rocks. The silica was most likely derived from the biogenic opal‐A of the siliceous radiolarian tests. The silica‐phase transformation started with the dissolution of the biogenic opal‐A and precipitation of opal‐CT. Subsequently, opal‐CT was recrystallized into crypto‐ and microquartz at low pH and high temperature. The length‐fast chalcedony and megaquartz occur later as infill to the cavities and pore spaces. The formation of chert is interpreted to be a result of mixing marine–meteoric waters. The effect of the freshwater diagenesis on carbonates is manifested by the dissolution of the allochems, precipitation of granular, drusy, and blocky calcite (meteoric cements), aggrading neomorphism of matrix, and calcitization of the skeletal particles. Geochemical analyses of the host carbonates indicate nearly flat REE patterns and absence of a negative Ce anomaly. This confirms the deviation from the typical seawater and supports the effect of phreatic meteoric water in the chert formation. The paragenetic relationships reveal that the chertification process was performed after dolomitization and before the carbonate meteoric cementation.

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“…Os teorés de CaO e MgO são baixos, indicando que não há influência de carbonatos na cimentação destes duripãs, como ocorre em regiões com outras condições climáticas em diversos países (Blank et al,1998;Eash & Sandor, 1995;James et al, 2000;Nash & Shaw, 1998;Sullivan & Koppi, 1995) e até mesmo no semi-árido brasileiro (Brasil, 1972;Brasil, 1973a;Brasil, 1973b;Silva et al, 1993).…”

Section: Análise Por Fluorescência De Raios-xunclassified

Gênese e degradação de duripãs em uma toposseqüência dos tabuleiros costeiros, Conde-BA

Romero

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Aos meus pais, Sebastião e Anazira, que prosseguiram me apoiando; OFEREÇO À minha esposa, Solange, que com seu constante incentivo e apoio foi fundamental para o desenvolvimento deste trabalho; Aos meus descendentes, Thaís e Ricardo Filho, que são motivos de alegria e de força para avançarmos nas atividades, DEDICO. AGRADECIMENTOS À Universidade Federal do Ceará, pela liberação concedida para participação no curso; Ao professor Celso Augusto Clemente, pela orientação e sugestões; À Coordenação de Aperfeiçoamento de Nível Superior (CAPES-PICDT), pela concessão da bolsa de estudo; À Fund ação d e Amparo à Pesquisa d o Estad o d e São Paulo (F APESP), pelo apoio financeiro ao projeto de pesquisa; Aos professores Luced ino, Célia, Melfi, Bertold o e Álvaro, pelas críticas e sugestões; Aos funcionários Sérgio, Bete, Luciano e Flávia, pelo apoi0 nas atividades desenvolvidas; Aos colegas Herdjânia, Márcio, Cláudia, Tiago, Vânia e Tairone, pelo auxílio e amizade;A todos que de algum modo contribuíram para a realização deste trabalho.

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Growth and destruction of Bathonian silica nodules in the Western Pyrenees (France)

Cited by 7 publications

References 5 publications

Epigenetic silicification of the Upper Oxfordian limestones in the Sokole Hills (Kraków-Częstochowa Upland): relationship to facies development and tectonics

Epigenetic silicification of the Upper Oxfordian limestones in the Sokole Hills (Kraków-Częstochowa Upland): relationship to facies development and tectonics

Origin of chert within the Turonian carbonates of Abu Roash Formation, Abu Roash area, Egypt: Field, petrographic, and geochemical perspectives

Gênese e degradação de duripãs em uma toposseqüência dos tabuleiros costeiros, Conde-BA

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