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Titolo:
The melilite-bearing high-temperature skarns of the Apuseni Mountains, Carpathians, Romania
Autore:
Pascal, ML; Fonteilles, M; Verkaeren, J; Piret, R; Marincea, S;
Indirizzi:
CNRS, Inst Sci Terre Orleans, F-45071 Orleans 02, France CNRS Orleans France 02 nst Sci Terre Orleans, F-45071 Orleans 02, France Univ Paris 06, Lab Petr, F-75252 Paris, France Univ Paris 06 Paris France F-75252 s 06, Lab Petr, F-75252 Paris, France Catholic Univ Louvain, Unite Geol, B-1348 Louvain, Belgium Catholic Univ Louvain Louvain Belgium B-1348 ol, B-1348 Louvain, Belgium Geol Inst Romania, RO-78344 Bucharest, Romania Geol Inst Romania Bucharest Romania RO-78344 RO-78344 Bucharest, Romania
Titolo Testata:
CANADIAN MINERALOGIST
, volume: 39, anno: 2001,
parte:, 5
pagine: 1405 - 1434
SICI:
0008-4476(200110)39:<1405:TMHSOT>2.0.ZU;2-N
Fonte:
ISI
Lingua:
ENG
Soggetto:
MULTICOMPONENT PYROXENES; CONTACT-METAMORPHISM; ALKALI FELDSPAR; OSLO RIFT; THERMODYNAMICS; EQUILIBRIA; MINERALS;
Keywords:
skarns; melilite; spurrite; tilleyite; titanian garnet; metasomatism; Apuseni Mountains; Romania;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Physical, Chemical & Earth Sciences
Citazioni:
42
Recensione:
Indirizzi per estratti:
Indirizzo: Pascal, ML CNRS, Inst Sci Terre Orleans, 1A Rue Ferollerie, F-45071 Orleans 02, France CNRS 1A Rue Ferollerie Orleans France 02 71 Orleans 02, France
Citazione:
M.L. Pascal et al., "The melilite-bearing high-temperature skarns of the Apuseni Mountains, Carpathians, Romania", CAN MINERAL, 39, 2001, pp. 1405-1434

Abstract

The melilite-bearing skarns of Cornet Hill (CH) and Upper Cerboaia Valley (UCV), in the Apuseni Mountains of Romania, occur at the contact between monzodiorite bodies of Ypresian age (Paleocene) and Neojurassic calcitic marbles. Typical wollastonite - grossular - diopside endoskarns are separated from exoskarns (tilleyite and spurrite or wollastonite at CH. wollastonite only at UCV), at most places, by a melilite-rich rock, in which veins and vein-like zones of recrystallization are composed only of idiomorphic melilite crystals reaching 15 cm across. Titanian garnet and wollastonite are the principal minerals associated with melilite (and also monticellite, perovskite, vesuvianite, cuspidine. spurrite, tilleyite, calcite, hydroxylellestadite, hydrogrossular and other minor alteration-induced minerals). A different association that includes aluminian diopside and grossular occurs (1) asveinlets in the marble close to the skarns and (2) as relict inclusions inendoskarns. From the geometrical relationships of the zone sequences and the veins, the textural features of the mineral associations and the inferred conditions of fluid-mineral equilibrium, these mineralogical peculiarities are interpreted as resulting from the superposition of two main stages. Firstly, there was circulation of a comparatively CO2-rich fluid formed the early aluminian diopside - grossular endoskarns, with depletion in Si (and Fe, Na, K) and inert behavior of Mg, Al, Ti. Then. a high-temperature (750 degreesC) fluid circulated on both sides of the contact between marble and endoskarns, and developed the melilite-rich, titanian-garnet-bearing rocks partly at the expense of previously formed endoskarns, and spurrite or wollastonite (CH) or wollastonite (UCV) exoskarns at the expense of marble. Thepressure of CO2 was very low, less than 26 bars at UCV and 16 bars at CH, with a H2O pressure less than 750 bars. Not only Si and Ca were mobilized, but also Mg, Al and Ti, leached from the endoskarns and deposited in the veins and the nearby part of exoskarns. This stage, which occurred in the temperature range corresponding to the end of the crystallization of plagioclase in the monzodiorite, has pegmatitic chemical and textural features. The main flow of fluid ended with the development of tilleyite partly at the expense of spurrite and wollastonite at CH, and local high-temperature (about710 degreesC) recrystallization of the zonation, mostly in veins, especially in the endoskarn-exoskarn boundary, but also within the endoskarns. A monticellite - gehlenite association appeared in the melilite-rich rocks, later followed by vesuvianite, whereas in the endoskarn, vesuvianite developedtogether with coarse-grained wollastonite and grossular.

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Documento generato il 09/07/20 alle ore 20:56:08