RT Journal Article
T1 Occurrence of Fe–Mg-rich smectites and corrensite in the Morrón de Mateobentonite deposit (Cabo de Gata region, Spain): A natural analogueof the bentonite barrier in a radwaste repository
A1 Pelayo Bayón, Marta
A1 García Romero, Emilia
A1 Labajo Rodillana, Miguel A.
A1 Pérez del Villar Guillén, L.
AB The Morrón de Mateo bentonite deposit is being studied as a natural analogue of the thermal and geochemicaleffects on a bentonite barrier in a deep geological repository of high level radioactive wastes.This bentonite deposit and its host rocks were intruded by a rhyodacitic volcanic dome that induced ahydrothermal metasomatic process affecting the biocalcarenite beds close to the dome. In this work,the mineralogical and chemical features of the clay minerals of the hydrothermally altered pyroclastic(white tuffs) and epiclastic rocks (mass flow), located in the NE sector of the Morrón de Mateo depositare described. White tuffs have a high content of phyllosilicates, mainly composed of dioctahedral smectites,while mass flow have a higher proportion of inherited minerals, the neoformed phyllosilicates aredioctahedral smectites and an interlayer chlorite/smectite mineral of corrensite type. The chemical compositionof smectites reflects the different nature of the parent rocks, in such a way that smectites fromwhite tuffs have a quite homogeneous chemical composition and their structural formulae correspond tomontmorillonite type, while smectites from mass flow show more chemical variability, higher Fe and Mgcontents and a mean structural formulae corresponding to Fe–Mg-rich beidellite and/or to an intermediatesmectite member between beidellite and saponite. In addition, chemical composition and texturalfeatures of corrensite-like clay minerals in relation to Fe–Mg-rich smectites in the samples have also beenstudied, suggesting that the former seems to be formed from Fe–Mg-rich smectites. The presence of corrensitein the epiclastic rocks suggests that in the Morrón de Mateo area a hydrothermal alteration processoccurred after bentonite formation, which transformed Fe–Mg-rich smectites into corrensite. Thistransformation was probably favoured by the intrusion of the Morrón de Mateo volcanic dome, whichproduced a temperature increase in the geological media and a supply of Fe–Mg-rich solutions. Thesephysicochemical conditions were also responsible for the metasomatic transformations observed inthe biocalcarenite beds located on the top of the bentonite deposit. All these data suggest that the Morrónde Mateo natural system could be a good natural analogue of both thermal and chemical effects on a bentonitebarrier related to the radioactive decay of fission products and the interaction between the corrosionproducts of steel over-packs and the bentonite. These circumstances would favour thetransformation of the candidate Al-rich smectites into Fe–Mg-rich smectites and corrensite, as steps priorto formation of chlorite. In this case, all the physicochemical and mechanical properties of Al-rich smectiteswould disappear and the clayey barrier would fail.
PB Elsevier
SN 0883-2927
YR 2011
FD 2011
LK https://hdl.handle.net/20.500.14352/41992
UL https://hdl.handle.net/20.500.14352/41992
LA eng
DS Docta Complutense
RD 6 abr 2025