Pre-Acadian copper mineralization in the English Lake District

Abstract

The Ordovician sedimentary and igneous rocks of the English Lake District host a widespread suite of epigenetic metalliferous veins dominated by copper sulphides with abundant arsenopyrite, pyrite and accessory galena and sphalerite. New field and microstructural evidence from examples of this suite at Coniston, Wasdale, Honister, Newlands and Borrowdale shows that the veins were strongly cleaved during the Early Devonian (Emsian) Acadian orogenic event. The principal evidence includes the continuity of wall-rock cleavage fabrics with pressure solution seams in the veins and consistently orientated cleavage through enclosed, rotated wall-rock fragments and chloritic mats. There is also widespread complex intracrystalline deformation in quartz, cataclasis of arsenopyrite and pyrite, fracturing and/or buckling of bladed hematite, and growth of quartz or mica-fibre strain fringes. Chalcopyrite was partially or totally remobilized, enabling it to migrate along quartz crystal boundaries, and invade brecciated pyrite. Previous K-Ar Early Devonian age determinations for the mineralization are considered to have been reset. The pre-Acadian age of this mineralization, its style and relationship to the volcanic rocks permits a genetic link with the final phases of Caradoc magmatism.

The applicability of G-BASE stream sediment geochemistry as a combined geological mapping, and prospective exploration tool for As-Co-Cu-Ni mineralisation across Cumbria, UK.

“…Therefore, shallower batholith topography was considered an indicator of more prospective sites. Regional and local scale faults are also associated with As-Co-Cu-Ni mineralisation (Solferino et al 2021) as the faults act as a conduit for fluid migration, and possibly metal scavenging during transport (Millward et al 1999). Lastly, historic mining sites were considered an exploration indicator as these can provide access to deeper rock units, spoil heap samples, and mineralisation from available samples or reports.…”

Radon concentrations in abandoned mines, Cumbria, UK: safety implications for industrial archaeologists

“…1, 2, 3) lie in a region of hard volcanic rhyolite and andesitic lava interbedded with hardened and cleaved tuffs/ashes. Mitchell (1940) and Millward et al (1999) have shown that the mineral veins that occur in faults and fissures are wide and productive within acid wall rocks, but are poor in andesite, andesitic tuff and volcaniclastic sandstone. South of Levers Water, these mineral veins trend southeast.…”