Fault-Hosted Palygorskite from the Serrata De Níjar Deformation Zone (SE Spain)

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