A dorozsmai márvány (Tiszai-főegység) kőzettani újravizsgálata: deformáció és fluidum hatása a mikroszerkezet fejlődésére

Abstract

Detailed petrographic studies on marbles are rare in the Hungarian geological literature. Determination of the mineral phases and their grain size, examination of the grain boundaries as well as deformation microstructures, however, can provide a comprehensive information about the metamorphic evolution and the deformation history of a marble unit.The metamorphic basement block near the village of Dorozsma contains a few-meter-thick marble zone within the Békés-Codru Zone. A petrographic study of archive thin sections representing this marble zone was carried out from the boreholes Dorozsma-4, Dorozsma-7 and Dorozsma-54.The fine-grained marble samples show heteroblastic texture with a composition of carbonate + quartz + muscovite + Mg-chlorite ± talc. The carbonate crystal boundaries are dominantly sutured, embayed and rarely curved. All the morpho logical types of deformation twins appear in the samples, but dominantly twin types II and IV are present. The characteristic features of the samples are small dissolution cavities filled with fine crystalline carbonate, blocky quartz and, in some cases, with saddle dolomite. In the samples from the borehole Dorozsma-4 small inclusion free carbonate grains substitute the deformation twins of the large carbonate crystals. In addition, small carbonate neoblasts and Mgchlorite flakes can be found among the large carbonate crystals. Characteristic microstructures of the samples from the well Dorozsma-7 are large sigmoid carbonate clasts in a very fine-grained matrix. The deformation twins of the carbonate clasts can be easily identified and show the signs of recrystallization. These samples beside the carbonate clasts also contain irregularly shaped polycrystalline quartz grains with dissolved edges, undulose extinction and signs of incipient dynamic recrystallization.The microstructures presented above suggest a polyphase deformation. The D 1 deformation event took place above 250 °C based on the relict microstructures. The subsequent D 2 ductile deformation event was a low-temperature dynamic recrystallization with a simple shear component, which could be the result of a hydrolitic weakening effect of hydrothermal fluids during deformation of the Dorozsma marble.Keywords: Dorozsma, marble, petrography, ductile deformation, metasomatism Összefoglalás A márványok petrográfiai vizsgálata napjainkig alárendelt szerepet kapott a hazai földtani szakirodalomban. A már -ványt felépítő ásványfázisok, valamint azok szemcsemérete és a szemcsehatár jellegének meghatározása (kőzetszövet), illetve a deformációs bélyegek feltárása és értelmezése révén azonban átfogó képet kaphatunk a kőzet metamorf fejlő dé -séről és deformációtörténetéről, ami független bizonyítékokkal szolgálhat a befoglaló metamorf kőzettest korreláció -jához.A Békés-Codrui-egységen belül elhelyezkedő, Dorozsma környéki kristályos aljzatban egy maximum néhányszor tíz mé ter vastagságú, markáns töréses deformációt szenvedett márványzóna található. Tanulmányunkban az e zónát mintázó Dorozsma-4, -7 és -54 fúrá...

Pervasive early diagenetic dolomitization, subsequent hydrothermal alteration, and late stage hydrocarbon accumulation in a Middle Triassic carbonate sequence (Szeged Basin, SE Hungary)

“…Furthermore, several studies highlighted the significance of the Late Cretaceous overthrust zones as fluid migration pathways (e.g., M. Tóth, 2008;Papp et al, 2017). Additionally, corresponding to the increased secondary porosity of the fractured basement zones, their hydrocarbon storage capacity is also remarkable in the SE Pannonian Basin (Juhász et al, 2002;Schubert et al, 2007;M.…”

“…Additionally, corresponding to the increased secondary porosity of the fractured basement zones, their hydrocarbon storage capacity is also remarkable in the SE Pannonian Basin (Juhász et al, 2002;Schubert et al, 2007;M. Tóth, 2008;Molnár et al, 2015;Papp et al, 2017).…”

“…14). This marble might be formed by the Late Cretaceous prograde metamorphism of the Mesozoic formations (M. Tóth et al, 2017;Papp et al, 2017). Furthermore, it must be noted that the marble body shows signs of post-metamorphic hydrothermal alterations such as sulphide-mineralization and pore-filling saddle dolomite (M. Tóth et al, 2017;Papp et al, 2017).…”

Az Alföld metamorf aljzata: a köztes tömegtől a tarka mozaikig

“…A Dorozsma kutatási területen mélyült fúrások petrográ fiai feldolgozásának eredményeként , M. TÓTH 2008, PAPP et al 2017 TÓTH & VAR GÁ -NÉ TÓTH 2020) alapvetően három fő kőzettípus (és ezek számos altípusa) azono sít ható. Ezek térbeli kapcso lat rendsze rét számos fúrás igazolja, de legjobban a végig maggal fúrt Do-54 tárta fel.…”

Paleofluid Fingerprint as an Independent Paleogeographic Correlation Tool: An Example from Pennsylvanian Sandstones and Neighboring Crystalline Rocks (Tisia Composite Terrane, S Hungary)

“…Both the fractured metamorphic basement rocks and the overlying Triassic sequences are hydrothermally altered, containing veinlets and dissolution vugs partially filled by saddle dolomite [49][50][51]. Under cathodoluminescence microscope, saddle dolomite crystals exhibit a marked zonation, whereas fluorescence microscopy reveals that significant part of the saddle dolomite crystals contains primary petroleumbearing aqueous inclusion assemblages.…”