Geochemistry and C, O, and Sr isotope composition of the Föderata Group metacarbonates (southern Veporicum, Western Carpathians, Slovakia): constraints on the nature of protolith and its depositional environment

Authors: MAREK VDACNY, PETER RUZICKA, ANNA VOZAROVA

Abstract: Major, trace, and rare earth element as well as C, O, and Sr isotope geochemistry is used to provide new insights into the characteristics and depositional environment of the protolith of the Föderata Group metacarbonates in the southern Veporicum cover sequence (Western Carpathians, Slovakia). The metacarbonates are characterized by high LOI and CaO and by small contents of various insoluble components. Among the trace elements investigated, only As, Ba, Co, Cu, Hg, Nb, Ni, Pb, Rb, Sb, Sr, Th, U, Y, Zn, and Zr display concentrations beyond their detection limits. The metacarbonates are strongly depleted in Rb, Ba, Th, Nb, Hf, Zr, and Y and enriched in U and Sr relative to the UCC. Chondrite-normalized rare earth element patterns of the metacarbonates show a moderate to strong fractionation in light rare earth elements over heavy rare earth elements and distinct negative Ce and Eu anomalies. Variation plots reveal several geochemical interrelationships, among which SiO₂ - Al₂O₃ - K₂O - TiO₂ - Ba - Nb - Rb - Zr are associated with the rock's silicate fraction. The carbonate fraction comprise CaO, MgO, and Sr. The overall geochemical and C-, O-, and Sr-isotopic signatures indicate that the metacarbonates developed from sedimentary carbonate materials that were deposited in a saline, shallow-marine, low-energy environment. The negative Ce anomaly (Ce/Ce* = 0.15-0.93) and the δ¹³C (2.36%o to -3.34%o) values indicate warmer climatic conditions during deposition. The consistency of the rock's chemical properties could be attributed to the relative stability experienced during the parent sedimentary material's deposition.

Keywords: Metacarbonates, geochemistry, C-isotopes, O-isotopes, Sr-isotopes, depositional environment, southern Veporicum

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