Boudinage arrangement tracking of hydrothermal veins in the shear zone: example from the argentiferous Strieborna vein (Western Carpathians)

Abstract

Argentiferous Strieborna vein of the Rožňava ore field occurs at the southwestern margin of the Gemeric Unit (Slovakia). The hydrothermal mineralization of the vein closely related to the Early Cretaceous tectonometamorphic shortening of the Western Carpathians. For their emplacement, the vein used the steeply dipping, fan-like cleavage and dislocation set of the Alpine regional structure. Successively the vein was integrated into the sinistral transpressional regime of the Transgemeric shear zone. A polyphase vein filling comprises Variscan metasomatic siderite remnants and the Early Cretaceous syntectonic hydrothermal mineralization, the latter consisting of two mineralization phases, quartz-siderite and quartz-sulphidic. During Cretaceous shear zone transpressional events, the vein was segmented into five individual bodies and redistributed to kinematically and geometrically different tensional and compressional boudins. The vein asymmetry increase, different vertical mineralization content and spatial distribution of mineral phases representing individual mineralization periods directly relate to a rheological contrast between the vein and surrounding rocks stress and pressure shadows distribution. The actual form and distribution of the Strieborna vein segments is the product of four boudin evolution stages: (1) pre-deformation, (2) initial, (3) boudin-forming and (4) boudin-differentiation stage that controlled vertical mineralization distribution. The sulphidic mineralization is dominated by two generations of argentiferous tetrahedrite and two youngest sulphosalts associations enriched by Sb and Bi. The youngest sulphosalts of the stibnite phase at the Strieborna vein resemble contemporaneous mineral associations at the nearby Čučma stibnite vein lode. Both vein occurrences located within the Transgemeric shear zone belong to the Rožňava ore field and they are cut by the same diagonal strike-slip fault. These analogies indicate a similar genesis of terminal associations at both these vein deposits. Results of the Strieborna vein sulphosalts spatial analysis confirm their vertical zonation. The Sb and Ag contents decrease, while Bi contents increase, with depth and conserve boudin evolution stages created in distinct rheological environments. The vertical boudin arrangement concentrates economically most prospective parts into asymmetric boudin tension shadows.

Boudin Types, Their Morphology and Significance in Interpreting Deformational History in Proterozoic Rocks of North Delhi Fold Belt, North Western India

“…The suite of boudin types developed during different deformational episodes, and indeed between different study areas, is often distinct. Hence, boudins may prove useful as indicators of flow regime during different deformational episodes and in characterizing different terrenes [50] [51]. Though it may not be very easy to unfold the deformational history based on boudin structures especially if they are not oriented, symmetrical boudins like in the present case.…”

Critical Tectonic Limits for Geothermal Aquifer Use: Case Study from the East Slovakian Basin Rim

“…Especially a thick dolomite layer posses very good conditions for water infiltration and groundwater circulation. Paleozoic rock complexes (mostly phyllites) of the Gemeric unit [31] form the main part of the depression footwall on the southwest. Their low water-saturation capacity is largely restricted to surface joints and weathering zone.…”

Critical Tectonic Limits for Geothermal Aquifer Use: Case Study from the East Slovakian Basin Rim

“…Especially a thick dolomite layer posses very good conditions for water infiltration and groundwater circulation. Paleozoic rock complexes (mostly phyllites) of the Gemeric unit [24] form the main part of the depression footwall on the southwest. Their low water-saturation capacity is largely restricted to surface joints and weathering zone.…”