Nanoscale resetting of the Th/Pb system in an isotopically-closed monazite grain: A combined atom probe and transmission electron microscopy study

Atom Probe Tomography: Development and Application to the Geosciences

“…For these reasons, TEM and APT are extremely complementary and the integration of these two techniques has the potential to revolutionise our understanding of the role of defects in controlling the compositional modification of minerals. TEM can be conducted on a separate specimen taken from close to the site of atom probe specimen preparation (Krakauer and Seidman , Gin et al , Montalvo et al , Seydoux‐Guillaume et al ). In such cases, care has to be taken with the extrapolation of observations by the individual techniques.…”

“…); (h) monazite specimen showing S (blue) exsolution in discrete clusters (Seydoux‐Guillaume et al . ); (i) mineral–organic interface in calcite from mussel shells. The atom map shows all atoms ranged in the data set (Pérez‐Huerta and Laiginhas ); (j) recrystallised feldspar from meteorite NWA6342.…”

“…In this specific example, the amount of common Pb is small. Nevertheless, APT is able to identify nanoscale segregated Pb domains of distinct isotopic composition (Fougerouse et al , Seydoux‐Guillaume et al ).…”

“…As outlined earlier, Pb associated with nano‐inclusions of apatite in monazite (Figure b) have been interpreted to reflect partitioning of Pb into apatite during unmixing of phosphate end‐member compositions immediately after growth (Fougerouse et al ). However, APT and TEM data from high‐temperature monazite grains from Rogaland, Norway, contain CaSO 4 nanoclusters that appear to be linked to Pb mobility associated with cluster formation during a younger, high‐temperature metamorphic event (Laurent et al , Seydoux‐Guillaume et al ). Lead clusters in pyrite have also been reported to form at the intersection of deformation‐related, non‐parallel dislocations (Fougerouse et al ).…”

“…Benchmarking of atom probe analysis of U isotopes in certified U 3 O 8 reference materials has shown that major isotopic ratios agree with known compositional values (Fahey et al ) and there are comparative thermal ion mass spectrometry (TIMS) and atom probe studies that show that Re‐Os analysis by atom probe may yield similar, though less precise, ages to more traditional TIMS analyses (Daly et al ). A number of studies have also investigated the mechanisms that can affect the distribution of radiogenic 207 Pb/ 206 Pb ratios in zircon (Figure ; Valley et al , , Peterman et al , Blum et al ), baddeleyite (White et al , Moser et al ) and monazite (Fougerouse et al , Seydoux‐Guillaume et al ). The nanoscale distribution of common Pb associated with deformation‐related defects has also been studied in titanite (Kirkland et al ) and pyrite (Fougerouse et al ).…”