Garnet–monazite rare earth element relationships in sub-solidus metapelites: a case study from Bhutan

Warren, Clare J.; Greenwood, Lucy V.; Argles, Tom W.; Roberts, Nick M. W.; Parrish, Randall R. and Harris, Nigel B. W. (2019). Garnet–monazite rare earth element relationships in sub-solidus metapelites: a case study from Bhutan. Geological Society, London, Special Publications, 478(1) SP478.1.

DOI: https://doi.org/10.1144/SP478.1

Abstract

A key aim of modern metamorphic geochronology is to constrain precise and accurate rates and timescales of tectonic processes. One promising approach in amphibolite and granulite-facies rocks links the geochronological information recorded in zoned accessory phases such as monazite to the pressure–temperature information recorded in zoned major rock-forming minerals such as garnet. Both phases incorporate rare earth elements (REE) as they crystallize and their equilibrium partitioning behaviour potentially provides a useful way of linking time to temperature. We report REE data from sub-solidus amphibolite-facies metapelites from Bhutan, where overlapping ages, inclusion relationships and Gd/Lu ratios suggest that garnet and monazite co-crystallized. The garnet–monazite REE relationships in these samples show a steeper pattern across the heavy (H)REE than previously reported. The difference between our dataset and the previously reported data may be due to a temperature-dependence on the partition coefficients, disequilibrium in either dataset, differences in monazite chemistry or the presence or absence of a third phase that competed for the available REE during growth. We urge caution against using empirically-derived partition coefficients from natural samples as evidence for, or against, equilibrium of REE-bearing phases until monazite–garnet partitioning behaviour is better constrained.

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• Item ORO ID
• 54600
• Item Type
• Journal Item
• ISSN
• 0305-8719
• Project Funding Details

• Funded Project Name	Project ID	Funding Body
  From Subduction to sand: Quantifying the balance between tectonic and surface processes during early continental collision and UHP rock exhumation. (SE-09-133-CW)	NE/H016279/1	NERC (Natural Environment Research Council)
  Studentship: Resolving conflicting models for the tectonic assembly of the Eastern Himalaya (SE-08-183-NH)	2K09E017/BUFI S168	Geological Society
  Not Set	IP-1177-0510	NERC (Natural Environment Research Council)

• Academic Unit or School
• Faculty of Science, Technology, Engineering and Mathematics (STEM) > Environment, Earth and Ecosystem Sciences
  Faculty of Science, Technology, Engineering and Mathematics (STEM)
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• © 2018 The Author(s)
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