Rubidium-strontium age determinations of muscovites and biotites from pegmatites of the Blue Ridge and Piedmont
Journal Article
·
· Journal of Geophysical Research
Eighteen mica specimens from pegmatites of the Blue Ridge and Piedmont provinces yield Rb/Sr apparent ages of 250 to 510 million years (m.y.). Muscovites from the Piedmont generally appear to be younger (avg. about 285 m.y.) than those from the Blue Ridge (avg. about 315 m.y.). Highly discordant ages were found for coexisting biotite and muscovite from two Blue Ridge pegmatites; the biotite ages are about 275 m.y. while the muscovites both yield ages of 510 m.y. Loss of radiogenic Sr87 from the biotite seems the most likely explanation of the differences; some of this may have been gained by the muscovite, thereby raising its age. Some possible causes of discordance seem excluded; these include different crystallization times for biotite and muscovite, preferential loss of rubidium from the muscovite, original Sr87 abundances in the pegmatitic fluids markedly higher than 7.02%, and assimilation by the crystallizing pegmatites of country rock with an anomalously high Sr87 abundance. In general, previous suggestion by others that widespread metamorphism and pegmatite emplacement took place in the Blue Ridge in two periods, about 500 and 350 m.y. ago was supported; however, the ages found for the eight Piedmont samples range from 255 to 330 m.y. and do not support the idea of a single 250-m.y. event in this region.
- Research Organization:
- Pennsylvania State Univ., University Park
- Sponsoring Organization:
- USDOE
- NSA Number:
- NSA-16-019165
- OSTI ID:
- 4830317
- Journal Information:
- Journal of Geophysical Research, Journal Name: Journal of Geophysical Research Journal Issue: 5 Vol. 67; ISSN 0148-0227
- Publisher:
- American Geophysical Union
- Country of Publication:
- Country unknown/Code not available
- Language:
- English
Similar Records
AGES OF PEGMATITE AND VEIN MINERALS OF SOUTHERN KIVU (EASTERN CONGO). PRELIMINARY INDICATION ON AGES OF SUCCESSIVE PEGMATITE PHASES
Rare earth element patterns in biotite, muscovite and tourmaline minerals
Rb-Sr AND U-Pb AGE DETERMINATIONS ON THE PEGMATITE OF I MONDEI (PENNINIC CAMUGHERA-MONCUCCO-COMPLEX, ITALIAN ALPS AND SOME GNEISSES FROM THE NEIGHBORHOOD)
Journal Article
·
Sun Dec 31 23:00:00 EST 1961
· Bulletin de la Societe Belge de Geologie, de Paleontologie et d'Hydrologie (Belgium)
·
OSTI ID:4724261
Rare earth element patterns in biotite, muscovite and tourmaline minerals
Conference
·
Sun Apr 20 23:00:00 EST 1986
·
OSTI ID:5216629
Rb-Sr AND U-Pb AGE DETERMINATIONS ON THE PEGMATITE OF I MONDEI (PENNINIC CAMUGHERA-MONCUCCO-COMPLEX, ITALIAN ALPS AND SOME GNEISSES FROM THE NEIGHBORHOOD)
Journal Article
·
Fri Nov 30 23:00:00 EST 1962
· Eclogae Geologicae Helvetiae (Switzerland)
·
OSTI ID:4160377