Rapid oxygen diffusion during high temperature alteration of zircon
Nick M W Roberts1, Qiong-Yan Yang2, M Santosh2,3,4
1NERC Isotope Geosciences Laboratory, British Geological Survey, Nottingham, NG12 5GG, UK. nirob@bgs.ac.uk.
Scientific Reports
|February 28, 2018
Summary
Zircon
Area of Science:
- Geochemistry
- Isotope Geology
- Mineralogy
Background:
- Zircon's isotopic signatures are crucial for understanding Earth's continental crust evolution.
- Distinguishing primary from secondary zircon compositions is vital for accurate geological interpretations.
Purpose of the Study:
- To investigate fluid-assisted alteration in zircons from Indian metasedimentary rocks.
- To analyze the impact of alteration on oxygen isotope signatures in zircon.
Main Methods:
- Utilized combined U-Pb-Hf-O and trace element analysis of zircon grains.
- Examined metasedimentary rocks from high-grade shear zones in the Southern Granulite Belt, India.
Main Results:
- Identified anomalously high and homogeneous oxygen isotope signatures indicating isotopic system disturbance.
- Postulated fluid-assisted alteration led to complete resetting of oxygen isotope signatures.
- Observed potential for fast oxygen diffusion under hydrous conditions in natural settings.
Conclusions:
- Fluid-assisted alteration can reset oxygen isotope signatures in zircon, potentially occurring more frequently than reported.
- Altered zircons may not be clearly classified as metamorphic, necessitating caution when using detrital zircon data.
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