Monazite occurrence, chemistry and chronology in the granitoid rocks of the Lachlan Fold Belt, Australia: An electron microprobe study

Aaron B Kelts, University of Texas at El Paso

Abstract

In-situ microprobe dating of monazite holds the promise of being an effective technique for obtaining chronologic data. Our research focuses on I- and S-type granitoids of the Lachlan Fold Belt, Australia, for which petrology and zircon chronology have been thoroughly characterized. This study documents the textural relationships, morphology, zoning, and ages of monazite in these granitic rocks. Whole section X-ray mapping has revealed that monazite occurs less often in the I-type granitic rocks, while it is ubiquitous in S-type rocks. The I-type granitoids which lack monazite usually contain other mineral phases enriched in rare earth elements. High resolution X-ray maps of individual monazites have revealed complex zonation patterns. This zoning probably represents a history of magmatic precipitation and/or post-magmatic re-equilibration of the mineral. The textural relationship of monazite with other accessory mineral phases was found to vary considerably between individual samples. Dates obtained from monazite in the I- and S-type granitoids record a spectrum of premagmatic, magmatic and postmagmatic crystal growth. (Abstract shortened by UMI.) ^

Subject Area

Geology|Geochemistry

Recommended Citation

Kelts, Aaron B, "Monazite occurrence, chemistry and chronology in the granitoid rocks of the Lachlan Fold Belt, Australia: An electron microprobe study" (2005). ETD Collection for University of Texas, El Paso. AAI1427692.
http://digitalcommons.utep.edu/dissertations/AAI1427692

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