Un simple gros cristal automorphe de tantalite provenant d'un assemblage d'albite-quartz-spodumène a présenté des âges U-Pb concordants se situant entre 365 et 395 Ma (tous ± 1-2 Ma).
En revanche, la molybdénite du quartzite adjacent à la pegmatite a accusé un âge Re-Os de 353 ± 2,5 Ma. The application of experimental petrology to the genesis and crystallization of granitic pegmatites.
These data are interpreted to indicate that the time of pegmatite crystallization occurred at 395 Ma with the younger U-Pb tantalite ages (i.e., youngest ~ 365 Ma), the 353 Ma Re-Os molybdenite age, and the oldest Ar age (i.e., 347 Ma) recording hydrothermal activity related to later magmatic events in this part of the Meguma terrane (e.g., 357 Ma Wedgeport Pluton). Geochemistry of Alkalis and Alkaline Earths in Ore-Forming Granites, Pegmatites, and Rhyolites.
The muscovite ages record resetting and cooling related to the ca.
Metamorphic grade varies from greenschist- to amphibolite-facies, with the higher grade rocks localized to the contact areas between the White Rock and Goldenville formations on the margins of the Yarmouth syncline (Mac Donald, 2000; Mac Donald 2002).
Peak meta-morphic conditions were estimated at 4 kbars and 550– 600°C by Moynihan (2003).
Within the amphibolite, small (≤1 cm), elongate lenses of plagioclase have a vertical plunge. New constraints on the age and origin of the Dunbrack Pb-Cu-Zn-Ag deposit, Musquodoboit Batholith, southern Nova Scotia.
Although the pegmatite is generally iso-tropic and the megacrysts of K-feldspar and spodumene in fact have the long axes of crystals oriented perpendicular to the wall rock fabric, the pegmatite locally contains a fabric, as manifest by : (1) small shears through muscovite-rich zones (Fig.
RÉSUMÉLa pegmatite du lac Brazil dans le Sud-Ouest de la Nouvelle-Écosse constitue la seule pegmatite de type Li-Cs-Ta (LCT) reconnue dans le terrane de Meguma en Nouvelle-Écosse. Transactions of the Royal Society of Edinburgh: Earth Sciences, 87, pp.
2c, d); (2) ﬂattened quartz megacrysts with 10– 20:1 aspect ratios (Fig.
2e, f); (3) a penetrative micro-fabric in the albitic aplite zones (Fig.
The quartzite adjacent to the pegmatite lenses is mainly buff, but locally the buff color gives way to white which may in part be an exomorphic alteration (i.e., siliciﬁcation) related to pegmatite emplacement (D. In addition, thin (cm-scale) white seams of very pure quartzite (perhaps representing re-crystallized quartz veins? The BLP consists of two separate pegmatite lens, each with a subcrop extent of a few hundred m length and ≤20– 25 m width, that strike northeasterly with near vertical to steeply southeast dips (Fig. The pegmatite lenses have complex internal zonation and are dominated by areas of megacrystic (i.e., 1– 2 m) blocky K-feldspar and spodumene with an inter-granular matrix with variable proportions of quartz-feldsparspodumene-muscovite. U/Pb and Re-Os dating of the South Mountain and Musquodoboit batholiths, Nova Scotia: evidence for protracted magmatichydrothermal events.
Formation of secondary albite after K-feldspar is manifest as either ﬁne-grained sacchroidal albite or euhedral platy cleavelandite. Joint Meeting Northeastern Section Geological Society of America-Atlantic Geoscience Society, Program with Abstracts.