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Clay diagenesis and low-grade metamorphism of Tithonian and Berriasian sediments in the Cameros Basin (Spain)

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Fernández Barrenechea, José María and Rodas, Magdalena and Frey, Martín and Alonso Azcárate, Jacinto and Mas Mayoral, José Ramón (2011) Clay diagenesis and low-grade metamorphism of Tithonian and Berriasian sediments in the Cameros Basin (Spain). Clay minerals, 36 . pp. 325-333. ISSN 0009-8558

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Official URL: http://www.minersoc.org/pages/e_journals/clay.html



Abstract

The clay mineral assemblages of the Tithonian and Berriasian sediments (Tera and
Oncala Groups) in the eastern part of the Cameros basin are investigated at seven localities. The
lowest-grade assemblage, located on the southern border of the basin, contains calcite + quartz +
hematite + kaolinite + mixed-layer illite-smectite (R = 1, 6585% illite layers) + discrete illite (IC
= 0.50.65D82y). Systematic increases in the illite and chlorite crystallinities suggest increasing
metamorphic grade from the northwest part of the basin to the southeast. This trend does not follow
the pattern previously described for the overlying late Berriasian–early Aptian sediments (Urbio´n and
Enciso Groups), which exhibit a higher metamorphic grade. This may result from local variations in
sedimentary facies, as well as the circulation of hot migratory fluids. Tertiary compression occurring
long after the main metamorphic event is considered to be responsible for the enhanced illite and
chlorite crystallinities measured in the SE extreme of the basin.


Item Type:Article
Uncontrolled Keywords:Diagenesis, Low-grade metamorphism, Clay minerals, Illite crystallinity, Chlorite crystallinity
Subjects:Sciences > Geology > Mineralogy
ID Code:17595
Deposited On:09 Jan 2013 11:44
Last Modified:11 Dec 2018 08:46

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