Publication: Fault-Hosted Palygorskite from the Serrata de Nijar deformation zone (SE Spain)
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Publication Date
2006
Authors
Súarez Barrios, Mercedes
Oyarzun, Roberto
Regueiro, M.
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Clay Minerals Society
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Abstract
Palygorskite fibers growing along fault planes in the outcrops of a large fault zone in SE Spain
(Carboneras Fault Zone: CFZ; Serrata de NõÂjar) were studied by X-ray diffraction, scanning electron
microscopy-energy dispersive X-ray analysis, and transmission electron microscopy-analytical electron
microscopy. The structural formulae, calculated per half unit-cell, is: Si7.95Al0.05O20(Al1.93Fe0.08Mg1.92)
(OH)2(OH2)4Na0.09K0.01Ca0.034(H2O). The samples have minor tetrahedral substitutions, with Mg/Al
ratios close to one, and contain very small amounts of Fe3+. The number of octahedral cations per half unit-
cell is 3.93. The fault-hosted palygorskite shows macroscopic ductile features including incipient foliation.
Based on field and laboratory observations, as well as on regional geological evidence indicating the
existence of widespread hydrothermal processes along the Serrata de NõÂjar and surrounding areas, we
suggest that palygorskite may have formed during ongoing deformation in the CFZ, as a precipitate from
Mg-rich hydrothermal fluids.