Rb-Sr and Sm-Nd isotopic study of the Glen Mountains layered complex: initiation of rifting within the southern Oklahoma aulacogen

Journal Article · Fri Jan 01 00:00:00 EST 1988 · Geology; (United States)

DOI:https://doi.org/10.1130/0091-7613(1988)016<0013:RSASNI>2.3.CO;2· OSTI ID:5334915

Lambert, D D; Unruh, D M; Gilbert, M C

Rb-Sr and Sm-Nd isotopic data for rocks and minerals of the Glen Mountains layered complex (GMLC), a midcontinent mafic layered intrusion in the Wichita Mountains of southwestern Oklahoma, constrain the time of initiation of rifting within the southern Oklahoma aulacogen and provide information on the chemistry of the early Paleozoic mantle. Four whole-rock samples define a Rb-Sr isochron corresponding to a maximum crystallization age of 577 +/- 165 Ma and an initial Sr isotopic composition of 0.70359 +/- 2. A three-point Sm-Nd mineral-whole-rock (internal) isochron for an anorthositic gabbro provides a crystallization age of 528 +/- 29 Ma. These data suggest that the GMLC was emplaced into the southern Oklahoma aulacogen during the initial phase of rifting along the southern margin of the North American craton in the early Paleozoic. This Sm-Nd internal isochron age is within analytical uncertainty of U-Pb zircon ages for granites and rhyolites from the Wichita Mountains; therefore, mafic and felsic magmatism may have been contemporaneous within the rift during the early stages of development. Hybrid rocks and composite dikes in the Wichita Mountains provide field evidence for contemporaneous mafic and felsic magmas. Initial Sr and Nd isotopic data suggest that magmas parental to the GMLC were derived from a depleted mantle source. However, Nd isotopic data for the GMLC plot distinctly below data for the depleted mantle source cited by DePaolo and thus suggest that the parental magmas of the GMLC were either contaminated by Proterozoic crust of the southern midcontinent or were derived from a heterogenous mantle source region that had variable initial Nd isotopic compositions.

• Research Organization: Texas Christian Univ., Fort Worth (USA)
• OSTI ID: 5334915
• Journal Information: Geology; (United States), Vol. 16:1
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
MOUNTAINS
AGE ESTIMATION
OKLAHOMA
COMPARATIVE EVALUATIONS
DIKES
GEOCHEMISTRY
GEOLOGIC FAULTS
GEOLOGIC HISTORY
ISOTOPE DATING
ISOTOPE RATIO
LEAD
MAGMATISM
NEODYMIUM
RUBIDIUM
SAMARIUM
STRONTIUM
URANIUM
ACTINIDES
ALKALI METALS
ALKALINE EARTH METALS
CHEMISTRY
ELEMENTS
FEDERAL REGION VI
GEOLOGIC FRACTURES
GEOLOGIC STRUCTURES
METALS
NORTH AMERICA
RARE EARTHS
USA
580100* - Geology &amp; Hydrology- (-1989)