Genetic Aspects of Albite Deposits From Central Sardinia: Mineralogical and Geochemical Evidence

Abstract The Na-feldspar orebodies in Sardinia occur along structures belonging to a regional ENE-WSW system that developed during the late stages of the Hercynian orogeny, and that was reactived during the Alpine orogeny. The main petrographic facies include granitoids, albitized granitoids, albitites (more or less rich in quartz), and albitites containing Mg minerals. Field observations and petrological and geochemical data point toward a metasomatic origin for the albitite orebodies.
Albitization involved depletion of K from K-feldspar and biotite, dissolution of free quartz, and a
lowering of Sr/Na2O and CaO/Na2O ratios in the protolith, under conditions of a positive thermal
gradient. The absence of later K-metasomatism implies that, during a subsequent decline in temperature, the composition of the albitizing fluids was modified by an influx of meteoric or other waters.
Keywords: Albite deposits, Mineralogical evidence, Geochemical evidence, Na-feldspar orebodies, albitizing fluids
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Summary: The Geological Society has its own quarterly journal called Exploration
and Mining Geology, for the publication of Canadian and international papers on
applied aspects of mineral exploration and exploitation, including mineral
deposit geology, geochemistry, and geophysics, mining geology, mineral resource
appraisal and estimation methods, environmental geology, and case histories. The
editor of the journal is Jeremy P. Richards
Publication: Exploration & Mining Geology
Issue: 1
Volume: 5
Year: 1996
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Summary: The East Sullivan Stock (ESS) is a small, composite felsic alkaline pluton of presumed late Archean age in the Val d’Or mining district. Three main facies have been distinguished: monzonite
sensu stricto, porphyritic monzonite, and green trachytic porphyry. This monzonitic group of
rocks is of relatively homogeneous composition with high abundances of Na2O, K2O, Ba, Sr, Rb, Zr,
Mo and LREE. The alkaline ESS is distinguished from other igneous units in the Val d’Or mining
district, such as the...
Publication: Exploration & Mining Geology
Author(s): MEHMET F. TANER
Keywords: East Sullivan Stock, Gold-Copper, exploration, Hydrothermal solution
Issue: 1
Volume: 5
Year: 1996
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Summary: Oxide-facies banded iron formation in the Third Portage Lake area is hosted by ultrama?c and calc-alkaline volcanic rocks and related sedimentary rocks of the Archean (2.8 Ga) Woodburn Lake Group, 80 km north of Baker Lake. These rocks record at least two phases of metamorphism/metasomatism. Greenschist facies metamorphism, in the temperature range of 370°C to 520°C and at pressures above 2.3 kbar, has affected all rocks on a regional scale. Later mineralization and alteration of banded iron...
Publication: Exploration & Mining Geology
Author(s): A.E. ARMITAGE, R.S. JAMES
Keywords: Mineralization, Gold mineralization, Northwest Territories, Portage Lake, Metamorphism.
Issue: 1
Volume: 5
Year: 1996
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Summary: The Ni-rich Epidote Zone of the Fraser Mine at Sudbury is characterized by alteration assemblages rich in epidote, actinolite and magnetite which are roughly concentrically zoned and up to hundreds of meters in length. These zones form discrete areas within the igneous Footwall Breccia below the Sudbury Igneous Complex. The assemblages grade from epidotized Footwall Breccia matrix, through actinolite-bearing rocks with few vestiges of original Footwall Breccia textures, into the most...
Publication: Exploration & Mining Geology
Author(s): CATHARINE E.G. FARROW
Keywords: Geochemistry, Geochemical evolution, Frasier Mine.
Issue: 1
Volume: 5
Year: 1996
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