The early history of the Neotethys archived in the ophiolitic mélange of northwestern Croatia

Abstract

Ophiolite exposures in NW Croatia have been attributed to the Western Vardar Ophiolitic Unit and interpreted as derived from the Meliata-Maliac-Vardar branch of the Neotethys. Blocks within the ophiolitic mélange on Mt. Ivanščica were investigated for petrological and geochemical characteristics of effusive rocks and radiolarian dating of associated pelagic sedimentary rocks. Analysed effusive basic rocks represent chemographically uniform sub-alkaline high-Ti massive tholeiitic basalts characterized by an enriched composition typical of E-MORB. These basalts are compatible with approximately 9 to 11% of partial melting of an enriched mantle source transitional between primitive and depleted MORB-type mantle and are formed in the non-subduction geotectonic setting of E-MORB-type. This reflects an initial succession of oceanic protocrust formation and the onset of ocean spreading. Radiolarians from chert and shale succession associated with basalts indicate a Late Anisian to Early Ladinian age of the initial ocean floor spreading, which continued into the Langobardian. Obtained data are correlative with reported blocks interpreted as remnants of the Triassic Neotethys crust from the ophiolitic mélange of the Western Vardar Ophiolitic Unit and further reaffirm common origin from a single ocean basin located east of the Adria microplate. Thematic collection: This article is part of the Ophiolites, melanges and blueschists collection available at: https://www.lyellcollection.org/topic/collections/ophiolites-melanges-and-blueschists

Unravelling the Tectonic Evolution of the Dinarides – Alps – Pannonian Basin Transition Zone: Insights from Structural Analysis and Low-Temperature Thermochronology from Ivanščica Mt., NW Croatia

“…2). This ophiolitic mélange is composed of centimeter to hundred meters sized blocks of sandstone, chert, basalt and gabbro chaotically embedded within a shaly-silty matrix (Babić et al, 2002;Slovenec et al, 2011;Kukoč et al, 2024). It is interpreted as formed during the Middle Jurassic supra-subduction in the northern branch of Neotethys Ocean and subsequent Late Jurassic to earliest Cretaceous obduction of ophiolites of this oceanic realm on the eastern Adriatic margin (Babić et al, 2002;Kukoč et al, 2024).…”

“…were relatively scarce (Babić et al, 2002;Goričan et al 2005;Lužar-Oberiter et al, 2009, until a series of recently published studies released by the GOST project (https://projectgost.wordpress.com). These studies provide new data set on stratigraphy (Slovenec et al 2020; Kukoč et al, 2023Kukoč et al, , 2024, petrology Slovenec et al, 2023;Šegvić et al, 2022) and lithostratigraphy of the Adriatic passive margin successions (Vukovski et al, 2023) tectonically assembled into the structural architecture of this mountain. As a supplement to published studies of the GOST project, this paper aims to present new and more detailed data on spatial arrangement, kinematics and age of deformational structures in Mesozoic and Cenozoic rocks of Ivanščica Mt.…”