Superposed parageneses in the spurrite-, tilleyite- and gehlenite-bearing skarns from Cornet Hill, Apuseni Mountains, Romania

We describe the occurrence of high-temperature, spurrite-, tilleyite- and g ehlenite-bearing skarns from Cornet Hill, part of the Metaliferi Massif, Ap useni Mountains, Romania, and the main mineral species developed in these r ocks. The host skarns are developed at the contact between a quartz monzoni tic - monzodioritic body of Paleocene - Ypresian age and Tithonian limeston es. The primary mineral assemblage mainly consists of tilleyite, spurrite a nd gehlenite, with various amounts of garnet and wollastonite: perovskite, monticellite and hydroxylellestadite are present but scarce. The skarns hav e clearly undergone a late metasomatic event. which produced, for example, diopside veins cross-cutting tilleyite, spurrite, and gehlenite. and small masses and veins of vesuvianite replacing gehlenite. Subsequent hydrotherma l and weathering overprints on the primary assemblages resulted in the form ation of three secondary parageneses: (1) an early hydrothermal one that in cludes scawtite, xonotlite and hibschite, (2) a late hydrothermal one that includes 11 Angstrom tobermorite, riversideite, thomsonite. gismondine, ara gonite, and calcite, and (3) a weathering paragenesis that includes plombie rite. portlandite, and allophane. The main properties of these mineral spec ies, as revealed using chemical. optical and X-ray powder analyses, are rep orted here, We document the first occurrence of plombierite, tobermorite, r iversideite, portlandite and allophane in Romania.