Zr-rich Non Metamict Perrierite-(Ce) from Holocrystalline Ejecta in the Sabatini Volcanic Complex (Latium, Italy)

G. C. Parodi, G. Della Ventura, A. Mottana and M. Raudsepp

Museo di Mineralogia, Università di Roma ‘La Sapienza’, Piazzale Aldo Moro 5, 1-00185, Roma, Italy
Dip. Scienze Geologiche, Terza Università di Roma, Via Ostiense 169, I-00151, Roma, Italy
Dept. of Geological Sciences, University of U.B.C., 6339 Stores Road, V6T 1Z4, Vancouver, Canada

Abstract: This paper reports the first in-situ finding of perrierite-(Ce) in Latium. The mineral occurs as brownish-red, transparent, well-developed, euhedral, prismatic crystals inside the miarolitic cavities of a holocrystalline ejectum from La Mola, Monti dell'Anguillara district, Sabatini volcanic complex.

The cell parameters (from Gandolfi film) are (in Å): a = 13.629(9), b = 5.727(1), c = 11.715(6), β(°) = 113.74(2), V(Å³) = 835.5(9). The crystal-chemical formula, based on microprobe analysis of one grain, is: (Ca1.882Th0.124REE2.021Y0.024)(Fe0.9282+Mg0.072)(Ti0.735Al0.632Zr0.484Nb0.019Mn0.033Mg0.045)Ti2(Si3.911Al0.089)O22.

This perrierite is the most Zr-rich described so far. The entry of Zr in the C site of the structure is related to the substitution of large amounts of Ca in the A site, according to the charge balancing relationship: CaA2++(Ti4+,Zr4+)C=REEA3+

The genesis of perrierite-(Ce) from La Mola is linked to late pneumatolitic-pegmatitic hypabyssal stages of the regional volcanic activity.