RT Journal Article
T1 Clay mineral genesis and chemicalevolution in the Miocene sediments ofSomosaguas, Madrid Basin, Spain
A1 Fesharaki, Omid
A1 García Romero, Emilia
A1 Cuevas González, Jaime
A1 López Martínez, María Nieves
AB A mineralogical and microtextural study of Somosaguas Miocene deposits, locatedin the Madrid Basin (western Madrid, Spain), was carried out using X-ray diffraction, scanningelectron microscopy, transmission electron microscopy and optical microscopy, whereas crystalchemistry data were obtained by analytical electron microscopy-transmission electron microscopyand electron icroprobe analysis. Four stratigraphic sections were studied, compising detrital rocksrepresenting intermediate and distal facies from alluvial fan deposits. The predominant source area ofthese sediments was the granitic rocks of the Spanish Central System with a lesser contribution ofmetamorphic rocks. Clayey arkoses are the most abundant rocks of these sections, typical of granitealteration under warm, semi-arid climates. The mineralogy is characterized by phyllosilicates,followed by feldspars and quartz. The data obtained reveal mineral mixtures of detrital (quartz,feldspars, kaolinite, micas and chlorite), transformed (illite and beidellite) and neoformed(montmorillonite) origin. Clay minerals resulted from interactions between detrital minerals andmeteoric waters. Two trends of degradation of micas are detected. The first shows a transition frommuscovites and dioctahedral illites, to beidellites. The other trend is defined by the biotitedegradation to beidellites with different layer charge and octahedral Fe content. Montmorilloniteswere neoformed from the hydrolysis and weathering of primary minerals (feldspars and muscovite).Magnesian clay minerals such as sepiolite, palygorskite and trioctahedral smectites, extremelyabundant in the centre of the basin, were not detected in Somosaguas sediments.
PB Blackwell Scientific publications
SN 0009-8558
YR 2007
FD 2007
LK https://hdl.handle.net/20.500.14352/50682
UL https://hdl.handle.net/20.500.14352/50682
LA eng
DS Docta Complutense
RD 20 may 2026