Cathodoluminescence, fluid inclusion and stable C–O isotope study of tectonic breccias from thrusting plane of a thin-skinned calcareous nappe

Abstract

Basal hydraulic breccias of alpine thin-skinned Muráň nappe were investigated by means of cathodoluminescence petrography, stable isotope geochemistry and fluid inclusions analysis. Our study reveals an unusual dynamic fluid regime along basal thrust plane during final episode of the nappe emplacement over its metamorphic substratum. Basal thrusting fluids enriched in 18 O, silica, alumina, alkalies and phosphates were generated in the underlying metamorphosed basement at epizonal conditions corresponding to the temperatures of 400-450°C. The fluids fluxed the tectonized nappe base, leached evaporitebearing formations in hangingwall, whereby becoming oversaturated with sulphates and chlorides. The fluids further modified their composition by dedolomitization and isotopic exchange with the host carbonatic cataclasites.Newly formed mineral assemblage of quartz, phlogopite, albite, potassium feldspar, apatite, dravite tourmaline and anhydrite precipitated from these fluids on cooling down to 180-200°C. Finally, the cataclastic mush was cemented by calcite at ambient anchizonal conditions. Recurrent fluid injections as described above probably enhanced the final motion of the Muráň nappe.

Continuity and Episodicity in the Early Alpine Tectonic Evolution of the Western Carpathians: How Large‐Scale Processes Are Expressed by the Orogenic Architecture and Rock Record Data

“…Tectonics v. Since the low-angle normal fault stepped upward into the Silicic nappe units as the uppermost element of the nappe pile, it brought in a direct contact the exhumed Veporic metamorphic complexes with the overlying unmetamorphosed Triassic shales and carbonates of the Silicic Muráň Nappe in the central part of the Veporic dome ( Figure 3). This contact is accompanied by a layer of overpressurized carbonate cataclasites (Milovský et al, 2003(Milovský et al, , 2012 and reveals a conspicuous structural and metamorphic gap indicating omission of at least 10 km of crustal section. vi.…”

Geological and geochemical studies of the Shujiadian porphyry Cu deposit, Anhui Province, Eastern China: Implications for ore genesis

“…As an example, Hurai et al (2002) and Milovský et al (2012) determined the pressure at the temperature of halite dissolution by determining the intersection of the metastable P-T path followed by fluid inclusions in the liquid field with the measured halite dissolution temperature. The method of Hurai et al (2002) can be applied to inclusions that can be cooled after homogenization to re-nucleate the bubble without nucleating halite, and which can then be reheated to the temperature of metastable vapor dissolution in the absence of halite.…”

A numerical model to estimate trapping conditions of fluid inclusions that homogenize by halite disappearance

“…As an example, Hurai et al (2002) and Milovský et al (2012) determined the pressure at the temperature of halite dissolution by determining the intersection of the metastable PT path followed by the fluid inclusion in the liquid field with the measured halite dissolution temperature. The method of Hurai et al (2002) can be applied to inclusions that can be cooled after homogenization to re-nucleate the bubble without nucleating halite, and which can then be reheated to the temperature of metastable vapor dissolution in the absence of halite.…”