Mineralogy and geochemistry of hydrothermal kaolins from the Adelita Mine, Patagonia(Argentina)

GRECCO, LAURA; MARFIL, SILVINA; MAIZA,PEDRO

CLAY MINERALS (PRINT)

MINERALOGICAL SOC

Lugar: Middlesex; Año: 2012 vol. 47 p. 131 - 146

0009-8558

The kaolin deposit Adelita mine, located in the province of Río Negro(Patagonia, Argentina), was studied. Petrographic studies on thin sections and chemical analyses of major, minor and trace elements on bulk samples were carried out. The kaolin content in the rock ranges from 31% to 65%. The mineralogy of the working face, which is about 45 m thick, varies from the upper zone, where the rock is strongly silicified, stained with iron oxides and carbonated, grades downwards to a kaolinized zone, with a quartz-kaolinite-dickite assemblage with relict lithic particles and a smaller amount of iron oxides, to end in the deepest zone where dickite, alunite, diaspore, quartz and scarce associated kaolinite occur. Kaolin mineralogy was determined by SEM, XRD, DTA-TG, IR and 18O and D isotope analyses. Trace element content, the relationships Zr vs. Ti, Cr + Nb vs. Ti + Fe, and Ce + Y + La vs. Ba + Sr, chondrite-normalized rare earth element diagrams showing a marked enrichment in LREE relative to HREE, with negative europium anomalies and d18O and dD between 3.8%0 and 7.7%0 and -123%0 and -103 %0, respectively, suggest that kaolin formed from the hydrothermal alteration of rhyolitic tuffs.