Rb-Sr, K-Ar, and /sup 40/Ar//sup 39/Ar systematics in Paleozoic glauconite from Mississippi Valley-type localities, and the dating of events during sediment diagenesis
Rb-Sr, conventional K-Ar, and /sup 40/Ar//sup 39/Ar systematics of Paleozoic glauconite in the Cincinnati arch area of Ohio-Indiana (Brassfield Formation), S.E. Missouri Lead District (Bonneterre and Davis Formations), and from glauconite subject to cation-exchange experiments were investigated in an attempt to understand the circumstances which lead to the anomalously young Rb-Sr and K-Ar ages from these glauconite occurrences. Rb-Sr systematics in Lower Silurian Brassfield Formation glauconite samples from the Cincinnati arch area (depositional age about 430 Myr.) have been completely reset by an event about 370 +/- 11 Myr. ago. The similarity between the glauconite isochron initial /sup 87/Sr//sup 86/Sr ratio (0.7096 +/- 3) and the /sup 87/Sr//sup 86/Sr ratio of gangue vug-filling calcite (0.7098 +/- 3) directly associated with glauconitic horizons, suggests that the fluids which precipitated the calcite were also responsible for resetting the Rb-Sr glauconite age. The mechanism involved was probably cation-exchange involving Sr in the fluid and in the glauconite. These fluids may have been Mississippi Valley-type ore fluids. Rb-Sr ages of Upper Cambrian glauconite pellets from the Viburnum Trend area (Davis Formation) in S.E. Missouri also may have been reset by Mississippi Valley-type ore fluids about 387 +/- 21 Myr. ago. All glauconite samples measured by the /sup 40/Ar//sup 39/Ar method have sustained /sup 39/Ar loss due to recoil during neutron irradiation.
- OSTI ID:
- 5926724
- Resource Relation:
- Other Information: Thesis (Ph. D.)
- Country of Publication:
- United States
- Language:
- English
Similar Records
Isotopic compositions of gangue versus ore minerals in the Upper Mississippi Valley zinc-lead district
The significance of Rb-Sr glauconite ages, Bonneterre Formation, Missouri: Late Devonian-Early Mississippian brine migration in the midcontinent: A discussion
Related Subjects
INDIANA
SEDIMENTS
MISSOURI
OHIO
AGE ESTIMATION
DIAGENESIS
GEOLOGIC DEPOSITS
ISOTOPE RATIO
PALEOZOIC ERA
RUBIDIUM
STRONTIUM
ARGON
POTASSIUM
ARGON 39
ARGON 40
ALKALI METALS
ALKALINE EARTH METALS
ARGON ISOTOPES
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
ELEMENTS
EVEN-EVEN NUCLEI
EVEN-ODD NUCLEI
FEDERAL REGION V
FEDERAL REGION VII
FLUIDS
GASES
GEOLOGIC AGES
ISOTOPES
LIGHT NUCLEI
METALS
NONMETALS
NORTH AMERICA
NUCLEI
RADIOISOTOPES
RARE GASES
STABLE ISOTOPES
USA
YEARS LIVING RADIOISOTOPES
580100* - Geology & Hydrology- (-1989)