Monazite Petrochronology

Monazite – allanite- fluorapatite symplectite in an Adirondack IOA deposit

Monazite is a LREE – bearing orthophosphate mineral that can be used as a geochronometer.  Given its affinity for Th, it can be dated with non-isotopic techniques, like Electron probe microanalysis, at very high spatial resolution (ca. 1 micron). Due to monazite’s compositional variability, it responds to, and can thus monitor the growth and consumption of major and accessory phases during metamorphism, helping decipher complex and convoluted metamorphic histories in polydeformed terranes.


Understanding the relationship between fluid evolution and monazite composition

intergrown monazite, allanite, and fluorapatite in an Iron-oxide Apatite (IOA) REE deposit in the eastern Adirondack Highlands

Age and origin of monazite symplectite, Adirondack Mountains

Using textural relationships to directly link geochronology to penetrative deformation

Regan et al., 2017a

Petrochronologic results from a complex migmatite

Using in-situ U-Th-total Pb geochronology to date shear zones

Regan et al., 2014

Y maps of monazite located within a full-section Mg map from the Yukon-Tanana terrane, eastern AK

In-situ monazite petrochronology to unravel melting processes in migmatitic paragneisses

Williams et al., 2019

Regan et al., 2017a

Useful Links

UMass electron microprobe facility