A numerical method for retrieving high oxygen isotope temperatures from plutonic igneous rocks: An example from the Laramie Anorthosite Complex, Wyoming, USA
- Univ. of Alberta, Edmonton (Canada). Dept. of Geology
- Univ. of Wyoming, Laramie, WY (United States)
The Sybille Pit is a late-stage magnetite-ilmenite-plagioclase-bearing differentiate of the Laramie Anorthosite with a wide range of grain sizes and modal mineralogy. This variability makes Sybille an ideal locality in which to study the factors that affect isotopic thermometry in plutonic environments. The authors have developed a numerical model based on isotope exchange trajectories that retrieves close to magmatic temperatures for samples from Sybille. This method is based on the premise that hand sample-scale sub-systems close to exchange with each other at temperatures that exceed those of the constituent minerals. The temperature of hand-sample scale closure is retrieved by back calculating the isotope exchange trajectories to the temperature at which two samples with widely different model compositions are in isotopic equilibrium. Application of these methods to samples from Sybille provides promising results. Whereas conventional isotopic thermometry of individual samples yields a wide range of temperatures ([approximately]600 to > 1000 C) depending on the mineral-pair chosen, application of this numerical model to multiple samples yields temperatures of 1,070 [+-] 100 C which corresponds closely to the inferred solidus for these rocks.
- OSTI ID:
- 5590158
- 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
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