Superposed Parageneses in the Spurrite-, Tilleyite-and Gehlenite-Bearing Skarns From Cornet Hill, Apuseni Mountains, Romania

Abstract

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 Å tobermorite, riversideite, thomsonite, gismondine, aragonite, and calcite, and (3) a weathering paragenesis that includes plombièrite, 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 plombièrite, tobermorite, riversideite, portlandite and allophane in Romania.

The reaction of carbonates in contact with laser‐generated, superheated silicate melts: Constraining impact metamorphism of carbonate‐bearing target rocks

“…Spurrite, Ca 5 (SiO 4 ) 2 (CO 3 ), a nesosilicate typical of high‐temperature contact metamorphism of siliceous limestones (e.g., Tilley ; Tilley and Harwood ; Walter ; Joesten ; Marineca et al. ; Pascal et al. ), occurs frequently in the carbonate‐rich material of both basalt–carbonate experiments.…”

Modular Microporous Minerals: Cancrinite-Davyne Group and C-S-H Phases

“…Of this type was the well-known fi nding of tobermorite phases at Crestmore, Riverside County, California, in a crystalline limestone at the contact with granodiorite (Eakle 1917), where also riversideite has been identifi ed. Tobermorite minerals also occur in vugs of larnite rocks at the dolerite-chalk contact at Ballycraigy, Larne, County Antrim, Ireland, together with scawtite (McConnell 1954); at Fuka, Okayama, Japan, in a vein (10 mm width) of the altered rock at the contact between limestones and intrusive igneous rocks (Maeshima et al 2003); in the Wessels mine (north of the town of Kuruman in the Kalahari Manganese Field, South Africa), where tobermorite was found near a dike and had crystallized in altered portions of the wall rock that had been in contact with the intrusion (Gutzmer and Cairncross 1993); in skarns at Cornet Hill, Apuseni Mountains, Romania (Marincea et al 2001), which have undergone a late metasomatic event and subsequent hydrothermal events, the late of which resulted in the formation of 11 Å tobermorite, riversideite, as well as thomsonite, gismondine, aragonite and calcite, while the subsequent weathering gave plombierite, portlandite and allophane. Tobermorite 11 Å occurs in garnet-pyroxene skarns at Okur-tau, Uzbekistan, and in garnet-wollastonite skarns at Arimao-Norte, Cuba, with plombierite, riversideite, scawtite (Zadov et al 1995); in xenoliths of calcite-bearing rocks in basic magmatic rocks, as at Vechec, Eastern Slovakia, and at Ozersky massif, near Baikal lake, together with calcite, plombierite, kilchoanite.…”

The role of aqueous silica concentration in controlling the mineralogy during high temperature contact metamorphism: A case study from Fuka contact aureole, Okayama, Japan

“…The petrogenetic grids used to deduce the observed assemblages were explained using reactions involving quartz, calcite and the minerals in the sequence. However, at Fuka (and elsewhere in Apuseni mountains, Pascal et al, 2001;Marincea et al, 2001) mineralogy and textural features of the skarn does not suggest a progressive sequence of reactions involving quartz. The formation of spurrite and tilleyite is suggestive of its formation with out early wollastonite.…”

“…However, spurrite gehlenite skarn has only limited occurrence in the world, e.g. Kilchoan, Scotland (Agrell, 1965), Christmas Mountains, North America (Joesten, 1974;1976), Fuka, Japan (Kusachi, 1975;Kusachi et al, 1978) and Apuseni Mountains, Romania Marincea et al, 2001). By the rarity of natural occurrence, studies on high temperature skarn has not much progressed, although the CaO SiO 2 vapour system triggers the transport of elements by means of decarbonation dehydration reactions in the crust.…”