Oxygen isotope speedometry in granulite facies garnet recording fluid/melt–rock interaction (Sør Rondane Mountains, East Antarctica). (6th June 2019)

• Record Type: Journal Article
• Authors: Higashino, Fumiko; Rubatto, Daniela; Kawakami, Tetsuo; Bouvier, Anne‐Sophie; Baumgartner, Lukas P.
• Is Part Of: Journal of metamorphic geology. Volume 37:Number 7(2019)
• Page Start: 1037
• Page End: 1048
• Publication Date: 2019-06-06
• Subjects: diffusion -- fluid -- garnet -- oxygen isotopes -- SIMS; Metamorphism (Geology) -- Periodicals; 552.4
• DOI: 10.1111/jmg.12490
• Languages: English
• ISSNs: 0263-4929

Abstract

Abstract: In situ analysis of a garnet porphyroblast from a granulite facies gneiss from Sør Rondane Mountains, East Antarctica, reveals discontinuous step‐wise zoning in phosphorus and large δ 18 O variations from the phosphorus‐rich core to the phosphorus‐poor rim. The gradually decreasing profile of oxygen isotope from the core (δ 18 O = ~15‰) to the rim (δ 18 O = ~11‰) suggests that the 18 O/ 16 O zoning was originally step‐wise, and modified by diffusion after the garnet rim formation at ~800°C and 0.8 GPa. Fitting of the 18 O/ 16 O data to the diffusion equation constrains a duration of the high‐ T event (~800°C) to c . 0.5–40 Ma after the garnet rim formation. The low δ 18 O value of the garnet rim, together with the previously reported low δ 18 O values in metacarbonates, indicates regional infiltration, probably along a detachment fault, of low δ 18 O fluid/melt possibly derived from meta‐mafic to ultramafic rocks.