The geology of the region shows evidence for the formation of a series of rift basins and local ocean lithosphere that was subsequently incorporated in the Variscan orogen (mountain-chain). The orogen was generated by the convergence of Africa and Europe.

Following collision and continental shortening and thickening, the continental lithosphere was extended once again immediately prior to granite emplacement.



After Alexander, 1995.




During the Lower to Mid Devonian, the region was affected by a period of rifting with the formation of sedimentary basins and deposition of deep marine mudstones and sandstones (turbidites). Significant basaltic magmatism (the generation and emplacement of magma and its solidification to igneous rock known locally as greenstones) also occurred. It was during this period that the oceanic floor, now preserved on the Lizard, was created. Changes in plate motion during the Mid- to Late Devonian brought about convergence between mainland Europe and Southern Britain. By the Late Carboniferous the Culm Basin in the north of the region was closed. The Carboniferous Period was marked by the development of major thrust faults and low-grade regional metamorphism of the Devonian rocks as they were incorporated into the Variscan mountain chain. Mudstones (pelites) were converted to schists and phyllites (slates). This produced at least one generation of folding and slately cleavage with quartz veins. The basaltic lavas were also metamorphosed into metabasites.

Basalt pillow lava

Quartz veins

Towards the end of the Variscan orogenic episode, the previously thickened continental lithosphere underwent a period of NNW-SSE extension due to the reactivation of thrust faults, and the formation of ENE-WSW trending faults and fractures. As the crust thinned this resulted in the partial melting of the mantle generating lamprophyres, and the lithosphere generating granite.

Lode structure

During the Lower Permian ENE-WSW faults and joints were generated in both the granites and metasediments by extension. These fractures acted as a plumbing system for mineralizing fluids to exploit to form mineral bearing lodes. The mineralizing fluids had been generated by variable mixing between hydrothermal fluids exsolved from the granite melts and those in the contemporary groundwater system in country rocks, and to a lesser extent later radiogenic heat from radioactive elements in the granite, producing hydrothermal convection systems.


Galena (lead ore)
Sphalerite (zinc ore)
Torbernite (uranium ore)
Barite (barium ore)

From the Permian, alluvial sedimentation took place in basins as the subsidence was controlled by the same extensional regime that controlled the granite generation and mineralization. During the Triassic to Cretaceous, episodes of E-W and N-S extension took place with rifting. As a consequence of this fluids from the basins (basinal brine fluids) were expelled and the mineral bearing waters formed crosscourse mineralization of mainly quartz, but also lead, zinc, barium, uranium, nickel, cobalt, silver, minor gold and rare palladium mineralization which cross-cut the tin-copper-tungsten veins.

Erythrite (cobalt ore)

Just prior to and during the Tertiary, the area was subjected to uplift of up to 1-1.5 km due to the thermal effects associated with the North Atlantic opening and possibly Alpine convergence. Any Mesozoic cover would have been lost during this event. During the Tertiary there was reactivation of the major NNW-SSE high angle faults and the development of Eocene and Oligocene pull-apart basins such as those at Bovey Tracey.



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