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 gehlenite-bearing skarns from Cornet Hill, part of the Metaliferi Massif, Apuseni Mountains, Romania, and the main mineral species developed in these rocks. The host skarns are developed at the contact between a quartz monzonitic - monzodioritic body of Paleocene - Ypresian age and Tithonian limestones. The primary mineral assemblage mainly consists of tilleyite, spurrite and gehlenite, with various amounts of garnet and wollastonite: perovskite, monticellite and hydroxylellestadite are present but scarce. The skarns have 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 hydrothermal and weathering overprints on the primary assemblages resulted in the formation of three secondary parageneses: (1) an early hydrothermal one that includes scawtite, xonotlite and hibschite, (2) a late hydrothermal one that includes 11 Angstrom tobermorite, riversideite, thomsonite. gismondine, aragonite, and calcite, and (3) a weathering paragenesis that includes plombierite. portlandite, and allophane. The main properties of these mineral species, as revealed using chemical. optical and X-ray powder analyses, are reported here, We document the first occurrence of plombierite, tobermorite, riversideite, portlandite and allophane in Romania.