Calculating pressure with elastic geobarometry: A comparison of different elastic solutions with application to a calc-silicate gneiss from the Rhodope Metamorphic Province

Moulas, Evangelos and Kostopoulos, Dimitrios and Podladchikov, Yuri and Chatzitheodoridis, Elias and Schenker, Filippo and Zingerman, Konstantin M. and Panagiotis, Pomonis and Tajcmanova, Lucie (2020) Calculating pressure with elastic geobarometry: A comparison of different elastic solutions with application to a calc-silicate gneiss from the Rhodope Metamorphic Province. Lithos. ISSN 0024-4937

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Abstract

Raman elastic geobarometry has increasingly been used complementary to metamorphic phase equilibria to estimate the conditions of recrystallization in metamorphic rocks. The procedure of applying Raman elastic barometry to host-inclusion mineral systems requires several steps that involve various assumptions. One of the most essential assumptions is that themineral host-inclusion systembehaves in an elastic and reversiblemanner. We discuss the discrepant results obtained by different authors employing different analytical solutions for elasticity and explore the assumptions lying behind each method. Furthermore, we evaluate numerically linear and nonlinear elastic solutions and showtheir discrepancies. Both formulations are tested against recently published experiments on quartz inclusions in garnet (QuiG) at pressures up to 3 GPa, and we find a very good agreement between calculated and experimental pressure values (within 10% relative error).We subsequently apply our new elastic geobarometer to a calc-silicate gneiss fromthe RhodopeMetamorphic Province (N. Greece). The results of Raman elastic barometry combined with garnet clinopyroxene geothermometry yield eclogite-facies conditions(~720±40 °C, ~1.5±0.2 GPa). These results are comparable to a high-temperature metamorphic overprint deduced from phase equilibriamodeling in surrounding lithologies (730±40 °C, ~1.2±0.1 GPa). Our findings indicate that the estimated pressure from Raman elastic barometry is consistent with a significant viscous relaxation at high temperatures. We conclude that although Raman elastic barometry is a powerful tool for pressure estimation in metamorphic rocks, its pressure estimates do not necessarily correspond to entrapment conditions. Our results are consequential for the estimates of reaction overstepping in high-grade metamorphic rocks.

Item Type:	Scientific journal article, Newspaper article or Magazine article
Subjects:	Physical sciences > Geology Physical sciences > Geology > Earth science
Department/unit:	Dipartimento ambiente costruzioni e design > Istituto scienze della Terra
Depositing User:	Filippo Schenker
Date Deposited:	09 Nov 2020 15:11
Last Modified:	09 Nov 2020 15:11
URI:	http://repository.supsi.ch/id/eprint/12082

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