Volume 24, Issue No. 1, 1999

Mario Aigner-Torres* and Friedrich Koller** 

Institute of Petrology, University of Vienna, A -1190 Vienna, Austria, * Present address: Institute of Mineralogy and Petrography, ETH-Zentrum, CH - 8092 Zurich, Switzerland (email: mario@erdw.ethz.ch), ** Present address: Department of Geological Sciences, University of Cape Town, Rondebosch 7701, South Africa (email: friedrich.koller@univie.ac.at)

Keywords: basalts, gabbros, Szarvaskš Complex. BŸkk Mountains, Hungary

ABSTRACT

The Szarvaskš complex exposes a rare fragment of Jurassic mafic and ultramafic igneous rocks that have been described as a dismembered portion of a Mesozoic ophiolitic sequence, formed in a setting related to the opening of a narrow basin of the Vardar ocean. These magmatic rocks are mainly extrusive pillow basalts, along with gabbroic sills intruded into terrigenous shales, and minor ultramafic and plagiogranite bodies. The basalts and some of the gabbros have fractionated N-MORB-like trace element patterns, but low e_Nd values, indicating a possible enriched source component as well. Other gabbros as well as the ultramafic rocks have the lowest REE patterns and are regarded as cumulates. The plagiogranites on the other hand, show inverse patterns with overall high trace element contents, and remarkable Eu anomalies. This suite of samples cannot be related solely by fractional crystallization to a common parental magma. Rather, they represent a combination of processes where the originally N-MORB-like magmas fractionated variable amounts of olivine+plagioclase+clinopyroxene±chromite and then assimilated terrigenous sediments abundantly present in the area. There is no reliable evidence for a subduction-related component in these rocks.