Putiš M., Yang Y.-H., Koppa M., Dyda M. & Šmál P., 2015: U/Pb vek metamorfno-metasomatického perovskitu zo serpentinizovaného harzburgitu meliatskej jednotky pri Dobšinej metódou LA-ICP-MS: časový indikátor interakcie horniny a fluida v akrečnej prizme. Acta Geologica Slovaca, 7, 1, 63–71. (in English)

U/Pb LA–ICP–MS age of metamorphic–metasomatic perovskite from serpentinized harzburgite in the Meliata Unit at Dobšiná, Slovakia: Time constraint of fluid-rock interaction in an accretionary wedge

U/Pb vek metamorfno-metasomatického perovskitu zo serpentinizovaného harzburgitu meliatskej jednotky pri Dobšinej metódou LA-ICP-MS: časový indikátor interakcie horniny a fluida v akrečnej prizme

Marián Putiš¹, Yue-Heng Yang², Matúš Koppa¹, Marian Dyda¹ & Peter Šmál¹

¹Department of Mineralogy and Petrology, Faculty of Natural Sciences, Comenius University in Bratislava, Mlynská dolina, Ilkovičova 6, 842 15 Bratislava, Slovakia; putis@fns.uniba.sk
²State Key Laboratory of Lithospheric Evolution, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China

Abstract

Perovskite-bearing harzburgites were discovered in a blueschist-bearing mélange complex in the Slovak Inner Western Carpathian Meliata tectonic unit at Dobšiná. Perovskite (1) exclusively occurs in serpentinized parts of harzburgite blocks, while perovskite (2) was found in rodingite veins crosscutting serpentinites. We separated metamorphic–metasomatic perovskite (1) from serpentinized orthopyroxene porphyroclasts of a harzburgite serpentinite in order to date fluid–rock interactions during serpentinization and/or rodingitization by in situ U/Pb LA–ICP–MS, and to compare its age with published ages (from 137±1 Ma to 135±1 Ma, with a mean age of 135.6±0.58 Ma) by U/Pb SIMS from the same locality. Perovskite (1) age at ~135±2.0 Ma was determined in the serpentinized zone of the harzburgite by LA–ICP–MS. Perovskite (2) from a rodingite vein was unsuitable for dating by this method because of its very low U content and general high common lead content. The perovskite (1) age is interpreted to record the interaction of metamorphic fluids with harzburgite fragments in the Neotethyan Meliatic accretionary wedge. Since perovskite (1) is younger than the high-pressure metamorphism of this wedge dated at 160–150 Ma, it constrains the exhumation period of the harzburgite fragments at ca. 135 Ma that is compatible with ages of ~137–135 Ma by U/Pb SIMS.

Key words: perovskite U/Pb LA–ICP–MS dating, serpentinization, rodingitization, Meliatic accretionary wedge, Inner Western Carpathians, Slovakia

Manuskript doručený: 2014-07-18

Manuskript revidovaný: 2015-01-23