10.6084/m9.figshare.3454184.v1
Rolf L. Romer
Rolf L.
Romer
Jochen Rötzler
Jochen
Rötzler
Effect of metamorphic reaction history on the U-Pb dating of titanite
Geological Society of London
2016
reaction history
peak metamorphism
radiogenic signatures
Dating titanite
prograde metamorphism
Saxon Granulite Massif
cases approach
bulk chemistry
core samples
X F
reaction progress
reference sample
Al contents
age variation
mineral assemblages
1 contents
reaction products
precursor minerals
precursor mineral
Geology
2016-06-21 11:57:28
Dataset
https://geolsoc.figshare.com/articles/dataset/Effect_of_metamorphic_reaction_history_on_the_U-Pb_dating_of_titanite/3454184
<p>Drill core samples of garnet-clinopyroxene granulite at Tirschheim and a reference sample at Waldheim (Saxon Granulite Massif,
Germany) endured the same P-T conditions, but developed variable mineral assemblages due to differences in bulk chemistry,
reaction progress, deformation and retrogression. Titanite formed during peak-metamorphic conditions of 22–24 kbar and 1020–1050
°C. Dating titanite from the various samples should yield the same age for all. The observed age variation, which exceeds
the duration of the entire metamorphic cycle, originates from the contrasting preservation of isotopic inheritance during
peak metamorphism and from post-peak re-equilibration. (1) Pb inheritance observed in some peak-metamorphic titanite demonstrates
that geochronologically relevant elements are redistributed among remaining reactants and reaction products during prograde
metamorphism and that the sequence of metamorphic reactions does not result in isotopic homogenization. Instead, metamorphic
minerals inherit the radiogenic signatures of the precursor minerals and may in extreme cases approach the age of the precursor
mineral. (2) Titanite that formed at peak-metamorphic conditions is characterized by high A1 contents and X<sub>F</sub> ≈ 0.8−1. Texturally comparable titanite that re-equilibrated during cooling (reduced Al contents and X<sub>F</sub>) yields too young U-Pb ages. The age of such re-equilibrated titanite does not correspond to the age of the event indicated
by the texture.
</p>