Magmatism in the Carolina terrane: Isotopic evidence for a Grenville-age source for Late Proterozoic volcanics and a mantle source for Silurian Concord syenite

Conference · Wed Jan 01 00:00:00 EST 1992 · Geological Society of America, Abstracts with Programs; (United States)

OSTI ID:5809473

Kozuch, M; Heatherington, A L; Mueller, P A ^[1]; Offield, T W; Koeppen, R P; Klein, T L ^[2]

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1. Univ. of Florida, Gainesville, FL (United States). Dept. of Geology
2. Geological Survey, Reston, VA (United States)

Rhyolitic to andesitic volcanic rocks from the central portion of the Carolina slate belt in North Carolina were analyzed for Sr and Nd isotopic composition and dated by U-Pb zircon geochronology. Samples were from the greenschist-facies Late Proterozoic Albemarle Group, Uwharrie Formation, and the informal Virginia sequence. A rhyolite from the Cid Formation of the Albemarle Group dated by U-Pb zircon geochronology yielded a Pb-207/Pb-206 age of 575 [+-] 7.6 Ma, consistent with its position below strata containing the Late Proterozoic trace fossil Pteridinium and above rocks previously dated at 586 [+-] 10 Ma. Rb-Sr isotopic analyses of late Proterozoic rocks showed average initial Sr-87/Sr-86 ratios of approximately 0.704, indicating a moderately depleted source for these samples. E[sub ND] values at 600 Ma are moderately positive (+0.7 [minus] +2.3) and T(DM) values range from 1.19--1.04 Ga. These isotopic data, along with major and trace element data, suggest that andesites and rhyolites of the Carolina slate belt may have formed by partial melting of attenuated, Grenville-aged continental lithosphere during a 600 Ma episode of arc volcanism. In contrast, Sr and Nd data for the younger ([approximately]400 Ma) Concord pluton indicate it was derived from a depleted mantle source (Sr-87/Sr-86 = 0.7021 and E[sub ND] = +0.4 at 400 Ma) without significant involvement of older lithosphere (T(DM) = 370 Ma).

• OSTI ID: 5809473
• Report Number(s): CONF-921058-; CODEN: GAAPBC
• Journal Information: Geological Society of America, Abstracts with Programs; (United States), Vol. 24:7; Conference: 1992 annual meeting of the Geological Society of America (GSA), Cincinnati, OH (United States), 26-29 Oct 1992; ISSN 0016-7592
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
NORTH CAROLINA
VOLCANIC REGIONS
AGE ESTIMATION
ANDESITES
GEOCHEMISTRY
ISOTOPE RATIO
LEAD
MAGMATISM
NEODYMIUM
PRECAMBRIAN ERA
RHYOLITES
RUBIDIUM
SILURIAN PERIOD
STRONTIUM
URANIUM
ACTINIDES
ALKALI METALS
ALKALINE EARTH METALS
CHEMISTRY
DEVELOPED COUNTRIES
ELEMENTS
GEOLOGIC AGES
IGNEOUS ROCKS
METALS
NORTH AMERICA
PALEOZOIC ERA
RARE EARTHS
ROCKS
USA
VOLCANIC ROCKS
580000* - Geosciences