Current models for elastic geobarometry have been developed with the assumption that the host and/or inclusion minerals are elastically isotropic. This assumption has limited applications of elastic thermobarometry to mineral inclusions contained in cubic quasi‐isotropic host minerals (e.g., garnet). Here, we report a new elastic model that takes into account the anisotropic elastic properties and relative crystallographic orientation (RCO) of a host‐inclusion system where both minerals are noncubic. This anisotropic elastic model can be used for host‐inclusion elastic thermobarometric calculations provided that the RCO and elastic properties of both the host and inclusion are known. We then used this anisotropic elastic model to numerically evaluate the effects of elastic anisotropy and RCO on the strains and stresses developed in a quartz inclusion entrapped in a zircon host after exhumation from known entrapment
- Award ID(s):
- 1918488
- PAR ID:
- 10447188
- Date Published:
- Journal Name:
- Annual Review of Earth and Planetary Sciences
- Volume:
- 51
- Issue:
- 1
- ISSN:
- 0084-6597
- Page Range / eLocation ID:
- 331 to 366
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Abstract P ‐T conditions to roomP ‐T conditions. We conclude that the anisotropic quartz‐in‐zircon elastic model is suitable for elastic thermobarometry and may be widely applicable to crustal rocks. Our results demonstrate that isotropic elastic models cannot be used to determine the entire strain state of an elastically anisotropic inclusion contained in an elastically anisotropic host mineral, and therefore may lead to errors on estimated remnant inclusion pressures. -
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Abstract Quartz crystals with zircon inclusions were synthesized using a piston-cylinder apparatus to experimentally evaluate the use of inclusions in “soft” host minerals for elastic thermobarometry. Synthesized zircon inclusion strains and, therefore, pressures (
P inc) were measured using Raman spectroscopy and then compared with the expected inclusion strains and pressures calculated from elastic models. Measured inclusion strains and inclusion pressures are systematically more tensile than the expected values and, thus, re-calculated entrapment pressures are overestimated. These discrepancies are not caused by analytical biases or assumptions in the elastic models and strain calculations. Analysis shows that inclusion strain discrepancies progressively decrease with decreasing experimental temperature in the α-quartz field. This behavior is consistent with inelastic deformation of the host–inclusion pairs induced by the development of large differential stresses during experimental cooling. Therefore, inclusion strains are more reliable for inclusions trapped at lower temperature conditions in the α-quartz field where there is less inelastic deformation of the host–inclusion systems. On the other hand, entrapment isomekes of zircon inclusions entrapped in the β-quartz stability field plot along the α–β quartz phase boundary, suggesting that the inclusion strains were mechanically reset at the phase boundary during experimental cooling and decompression. Therefore, inclusions contained in soft host minerals can be used for elastic thermobarometry and inclusions contained in β-quartz may provide constraints on theP –T at which the host–inclusion system crossed the phase boundary during exhumation. -
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Abstract Mineral inclusions are ubiquitous in metamorphic rocks and elastic models for host‐inclusion pairs have become frequently used tools for investigating pressure–temperature (
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1146/annurev-earth-031621-112720
