Minerals of the Montebrasite-Ambligonite Series of the El Quemado District.

ISBN-13: 9786207480524 / Angielski / Miękka / 2025 / 60 str.

Vanina Lucrecia López; María de las Mercedes Ortega Pérez

Opis

The pegmatites from Mina Santa Elena (Salta, Argentina) belong to the LCT family, rare element class, beryl type, beryl-columbite-phosphate subtype. The pegmatitic stage paragenesis includes Li-Al-F-OH (montebrasite), Li-Mn-Fe (lithiophyllite), Ca-Mn-Fe-OH, Ca-F-Oh-Cl (apatite), Mn-Fe-Mg-Ca (triplite) and Al-Fe-Mg-OH (scorzalite) phosphates; oxides of Nb-Ta (coltan), U (uraninite), Zr (zircon) and Zn (gahnite); Li silicates (Li-muscovite, lepidolite, elbaite, spodumene); beryl, muscovite, chorl, garnet, feldspars (albite, microcline) and quartz. The montebrasite contains F between <1 wt.% and 2.3 wt.%, and Li2O from 7.47-9.86 wt.%. The melt, enriched in P, F and H2O, promoted the crystallization of montebrasite rather than spodumene, at temperatures below 400°C. The mineral phases in paragenesis competed for various chemical elements, of which F was preferentially consumed by micas and Mn by coltan. The remobilization of Li, Ca, Mn and Fe during the hydrothermal stage contributed to the development of triplite (II), apatite (III), lithiophyllite and souzalite veinlets, and to the emplacement of a replacement zone with lepidolite.