Journal
LITHOS
Volume 394, Issue -, Pages -Publisher
ELSEVIER
DOI: 10.1016/j.lithos.2021.106184
Keywords
P-T path; Metamorphic sole; Ophiolite; Amphibolite; Kelyphite; Dinarides
Categories
Funding
- Croatian Science Foundation
- Hrvatska Zaklada za Znanost (HRZZ) [IP-2014-09-9541]
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The metamorphic sole of the Jurassic Krivaja-Konjuh ultramafic massif in central Bosnia and Herzegovina consists mainly of garnet amphibolites and pargasite amphibolites, with different P-T paths indicating distinct formation histories. The rocks formed during intra-oceanic subduction, with pargasite amphibolites cooling by subducting oceanic crust and garnet amphibolites exhumed in a subduction channel before coming in contact with the former.
The Inner Dinarides, a part of the Alpine-Dinaride mountain chain in south-eastern Europe, are known for extended ophiolite-derived ultramafic massifs. The sampled rocks from the metamorphic sole of such a massif, the Jurassic Krivaja-Konjuh ultramafic massif in central Bosnia and Herzegovina, are mainly garnet amphibolites, with large grains of pyrope-almandine garnet commonly surrounded by kelyphite coronae, and pargasite amphibolites. The bulk-rock geochemistry points to mantle peridotite as the protolith for pargasite amphibolite and N-MORB for garnet amphibolite. Pressure-temperature (P-T) pseudosections were constructed in the MnNCKFMASHTO system and contoured by isopleths for the modal and chemical composition of minerals. On this basis, a counterclockwise P-T path with maximum P-T conditions of 1.2 GPa and 960 degrees C was deduced for pargasite amphibolite as a bottom part of an overriding plate. This part was cooled by subducting oceanic crust. In addition, the Jurassic intra-oceanic subduction enabled infiltration of hydrous fluid necessary to form the pargasite amphibolites. A clockwise P-T path with maximum pressure conditions at ca. 2.1 GPa (ca. 65-70 km depth) and temperatures of 810 degrees C was reconstructed for garnet amphibolite from an upper part of the subducting plate which was exhumed in a subduction channel and came in contact with the pargasite amphibolite. Thus, these amphibolites formed before they were involved in a metamorphic sole at the interface between continental crust and obducting ophiolite. (c) 2021 Elsevier B.V. All rights reserved.
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