Probable provenance of Precambrian zircons extracted from an Ordovician sandstone from the Suwannee Basin

Conference · Mon Mar 01 00:00:00 EST 1993 · Geological Society of America, Abstracts with Programs; (United States)

OSTI ID:6078236

Mueller, P; Heatherington, A ^[1]; Nutman, A; Williams, I ^[2]; Wooden, J ^[3]

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1. Univ. of Florida, Gainesville, FL (United States). Dept. of Geology
2. Australian National Univ., Canberra (Australia). Research School of Earth Sciences
3. Geological Survey, Menlo Park, CA (United States)

Zircons separated from a core extracted from an Ordovician sandstone beneath Alachua County, Florida, were analyzed for U, Th, and Pb elemental and isotopic composition using the SHRIMP II ion microprobe. Forty separate grains were analyzed and ranged in age from [approximately]2.7 to 0.5 Ga. Fifty percent of the grains yielded ages of 0.52 to 0.64 Ga. In general, these ages correspond to the Pan-African (Africa) or Brasiliano (South America) orogenic cycles. The second largest group ([approximately]30%) yielded ages in the range 2.06 to 2.46 Ga, which generally corresponds to the Birimian (Africa) and trans-Amazonian (South America) orogenic cycles. Lesser populations yielded ages that were Middle Proterozoic ([approximately]1.7 Ga, 5%), Archean ([approximately]2.7 Ga, 5%), or too discordant for reliable interpretation ([approximately]10%). The zircons all have U and Th abundances indicative of a magmatic rather than metamorphic origin. The average age for all zircons is 1.33 Ga, comparable to the whole-rock Sm-Nd depleted mantle model age of 1.25 Ga. These data clearly indicate that the Suwannee Basin was receiving detritus from a long-lived Precambrian shield area that contained significant quantities of both Neoproterozoic and Early proterozoic magmatic rocks. Co-occurrences of 2.0--2.4 Ga and 0.5--0.65 Ga rocks are non existant in Laurentia. Among the Gondwanan continents, prominent occurrences are limited to western Africa and northeastern South America. It seems likely, therefore, that the pre-Paleozoic rocks of the Florida peninsula evolved in close proximity to these cratonic areas which were joined prior to the breakup of Gondwanaland. Peri-Gondwanan'' arcs and Antarctic derivations of the peninsula are improbable.

• OSTI ID: 6078236
• Report Number(s): CONF-9304188-; CODEN: GAAPBC
• Journal Information: Geological Society of America, Abstracts with Programs; (United States), Vol. 25:4; Conference: 42. annual Geological Society of America (GSA) Southeastern Section meeting, Tallahassee, FL (United States), 1-2 Apr 1993; ISSN 0016-7592
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
FLORIDA
SEDIMENTARY BASINS
GEOCHEMISTRY
ZIRCON
ORIGIN
AGE ESTIMATION
ELEMENT ABUNDANCE
GEOLOGIC HISTORY
ION MICROPROBE ANALYSIS
LEAD
THORIUM
URANIUM
ABUNDANCE
ACTINIDES
CHEMICAL ANALYSIS
CHEMISTRY
DEVELOPED COUNTRIES
ELEMENTS
GEOLOGIC STRUCTURES
METALS
MICROANALYSIS
MINERALS
NONDESTRUCTIVE ANALYSIS
NORTH AMERICA
SILICATE MINERALS
USA
580000* - Geosciences