Granites related to tin mineralization at Mt. Pleasant, New Brunswick, Canada: subvolcanic analogues of topaz rhyolites
Two type of fluorine-rich (>2000 ppm F) high-silica (>74 wt. % SiO/sub 2/) granite are present in the environs of the Mt. Pleasant Tungsten Mine. Both are subvolcanic in character and Devono-Carboniferous in age. An older fine-grained granite contains biotite (+/-chlorite) and is associated with the earlier W-Mo stockwork/breccia ore bodies. It is intruded by topaz- and fluorite-bearing granite porphyry/porphyritic granite to which later Sn-polymetallic base metal mineralization appears to be related. Major element characteristics (SiO/sub 2/ > 75 wt. %; Na/sub 2/O > 3.2 wt. %; K/sub 2/O/Na/sub 2/O > 1; TiO/sub 2/ < 0.2 wt. %; CaO < 0.7 wt. %; MgO < 0.2 wt. %; P/sub 2/O/sub 5/ < 0.05 wt. %) identify both phases as anorogenic granites. Trace element contents however permit their separation and identify the later granites with Rb > 800 ppm, Li > 100 ppm, Cs > 20 ppm, Ta > 15 ppm, F > 4000 ppm, and distinctive flat REE patterns with large negative Eu anomalies as the intrusive equivalents of topaz rhyolites. Such unique REE distributions suggest that melt depolymerization resulting from the enhanced solubility of fluorine may play a pivotal role in the evolution of these felsic magmas.
- Research Organization:
- Carleton Univ., Ontario (Canada)
- OSTI ID:
- 6070177
- Report Number(s):
- CONF-8510489-
- Journal Information:
- Geol. Soc. Am., Abstr. Programs; (United States), Vol. 17; Conference: 98. annual meeting of the Geological Society of America, Orlando, FL, USA, 28 Oct 1985
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
GRANITES
CHEMICAL COMPOSITION
PETROGENESIS
NEW BRUNSWICK
TIN ORES
MINERALIZATION
BIOTITE
CHEMICAL REACTION KINETICS
DEPOLYMERIZATION
FLUORINE COMPOUNDS
GEOCHEMISTRY
MINERALOGY
RARE EARTHS
RHYOLITES
SOLUBILITY
CANADA
CHEMICAL REACTIONS
CHEMISTRY
DECOMPOSITION
ELEMENTS
HALOGEN COMPOUNDS
IGNEOUS ROCKS
KINETICS
METALS
MICA
MINERALS
NORTH AMERICA
ORES
PLUTONIC ROCKS
REACTION KINETICS
ROCKS
SILICATE MINERALS
VOLCANIC ROCKS
580300* - Mineralogy
Petrology
& Rock Mechanics- (-1989)
580400 - Geochemistry- (-1989)