Movement and mineralization in the Tyndrum Fault Zone, Scotland and its regional significance

Abstract

Major and minor fracture analysis of the Tyndrum Fault Zone, Scotland, reveals a late Silurian history of transtensional deformation with opening across the zone as well as left-lateral strike-slip movements. The extensional phases are characterized by hydrothermal quartz veins and breccias associated with the early stages of precious-metal mineralization. The strike-slip movements are characterized by cataclastic textures and are associated with the later stages of the precious-metal mineralization. Further transtensional deformation in the Carboniferous is indicated by right-lateral strike-slip movements, associated with fractures throughout the zone containing both cataclastic and extensional hydrothermal quartz veins: the quartz veins are associated with base-metal mineralization. The pre-Devonian, WSW-ENE-directed, transtensional deformation of the zone is extrapolated to the whole Dalradian Terrane, the driving force being the gravitational collapse of the orogenic welt parallel to the tectonic trend. The necessary area increase is signified by the intrusion of the end-Caledonian granitic magmas and quartz-veins. The Carboniferous right-lateral movements resulting from N-S extension are related to similar movements, also transtensional, on the Great Glen Fault Zone and in the Midland Valley; the associated mineralization is related to a broader Dinantian base-metal mineralizing event.

A black shale protolith for gold-tellurium mineralisation in the Dalradian Supergroup (Neoproterozoic) of Britain and Ireland

“…The pyrite in the Dalradian Supergroup exhibits overgrowths that are, accordingly, attributed to metamorphism. Regional metamorphism is dated at late Cambrian to Ordovician (Friedrich et al 1999;Oliver et al 2000;Bird et al 2013), in advance of the gold mineralisation dated between Ordovician and Devonian (Treagus et al 1999;Rice et al 2016). …”

How the Neoproterozoic S-isotope record illuminates the genesis of vein gold systems: an example from the Dalradian Supergroup in Scotland

“…3; Treagus et al 1999;Tanner 2012). The sulphide assemblage is dominated by pyrite, chalcopyrite and galena; gold, as electrum, is associated with galena in fractured pyrite (Earls et al 1992).…”

“…The sulphide assemblage is dominated by pyrite, chalcopyrite and galena; gold, as electrum, is associated with galena in fractured pyrite (Earls et al 1992). Previous Ar -Ar and K -Ar dating suggests that mineralization occurred at 410 + 14 Ma (Treagus et al 1999), significantly after peak metamorphism and overlapping with granite magmatism, but with very large uncertainties. Recent geochronological work also suggests the age of mineralization is close to 410 Ma (Rice et al 2012).…”

Atypical Gold Mineralization in an Orogenic Setting--The Bohaun Deposit, Western Irish Caledonides

“…Elsewhere in the Caledonides of the British Isles, base metal mineralization occurs in Lower Palaeozoic and Dalradian rocks (Samson and Banks, 1988;Pattrick and Russell, 1989;Treagus et al, 1999). Notably at some of these localities gold and base metal mineralization are spatially associated e.g.…”

“…fluids at 140 to 200°C (Curtis et al, 1993). It is proposed that the base metal mineralization is associated with an Early Carboniferous mineralising event (Treagus et al, 1999). The Carboniferous base metal mineralization described above is thought to be genetically related and coeval with the carbonate-hosted Zn-Pb deposits of central Ireland (Patrick and Russell, 1989).…”