Genesis of Syntectonic Hydrothermal Veins in the Igneous Rock of Teschenite Association (Outer Western Carpathians, Czech Republic): Growth Mechanism and Origin of Fluids

Abstract

Hydrothermal mineralization hosted by the Lower Cretaceous igneous rock of the teschenite association at Jasenice (Silesian Unit, Flysch Belt, Outer Western Carpathians) occurs in two morphological types -irregular vein filled by granular calcite and regular composite vein formed by both fibrous and granular calcite and minor chlorite, quartz, and pyrite. Crosscutting evidence indicates that the granular veins are younger than the composite vein. The composite vein was formed by two mechanisms at different times. The arrangement of solid inclusions in the marginal fibrous zone suggests an episodic growth by the crack-seal mechanism during syntectonic deformation which was at least partially driven by tectonic suction pump during some stages of the Alpine Orogeny. Both the central part of the composite vein and monomineral veins developed in a brittle regime. In these cases, the textures of vein suggest the flow of fluids along an open fracture. The parent fluids of both types of vein are characterized by low temperatures (Th =66-163 °C), low salinities (0.4 to 3.4 wt. % NaCl eq.), low content of strong REE-complexing ligands, and δ 18 O and δ 13 C ranges of + 0.2/+12.5 ‰ SMOW and -11.8/-14.1 ‰ PDB, respectively. The parent fluids are interpreted as the results of mixing of residual seawater and diagenetic waters produced by dewatering of clay minerals in the associated flysch sediments. The flow of fluids was controlled by tectonic deformation of the host rock.

Genetic aspects of barite mineralization related to rocks of the teschenite association in the Silesian Unit, Outer Western Carpathians, Czech Republic

“…Such a trend is very characteristic for low-temperature post-magmatic hydrothermal mineralizations hosted by teschenites in the Silesian Unit (e.g., Dolníček et al 2010 a,b;Urubek et al 2014). …”

“…In addition, cementation of fissures and vesicles by hydrothermal minerals gave rise to abundant hydrothermal veins and amygdules. Recent studies (Dolníček et al 2010 a,b;Dolníček et al 2012;Urubek et al 2014;Kropáč et al 2015) revealed that multiple stages of hydrothermal activity occurred in this rock environment. The most important event was early post-magmatic alteration, which took place immediately after solidification of the host rock, when fluid circulation was allowed due to heat flow associated with the host intrusion (e.g., Dolníček et al 2010 a,b).…”

“…One of the specific features of teschenites is intense hydrothermal alteration of primary rock-forming minerals to a mixture of zeolites (analcime), phyllosilicates, and carbonates (Pacák 1926;Smulikowski 1930;Šmíd 1978;Dolníček et al 2010aDolníček et al ,b, 2012Urubek et al 2014;Kropáč et al 2015). In addition, cementation of fissures and vesicles by hydrothermal minerals gave rise to abundant hydrothermal veins and amygdules.…”

“…The most important event was early post-magmatic alteration, which took place immediately after solidification of the host rock, when fluid circulation was allowed due to heat flow associated with the host intrusion (e.g., Dolníček et al 2010 a,b). Later alteration events occurred during subsequent deeper burial (Dolníček et al 2012;Kropáč et al 2015) and thrusting during the Alpine Orogeny (Dolníček et al 2010 a;Urubek et al 2014).…”

“…Magmatic, marine, and diagenetic fluid sources have been suggested by previous works in this area (cf. Pacák 1926;Šmíd 1978;Dolníček et al 2010Dolníček et al a,b, 2012Urubek et al 2014). …”