page_title: Cornubian batholith
section_title: Granite
hierarchical_section_title: Cornubian batholith / Mineralogy and chemistry of the granite and other rocks / Granite
caption_attribution_description: English: Field photographs of Cornubian Batholith granites. A — Typical G1a granite with orthoclase phenocrysts (&lt; 25 mm) from the Carnmenellis Granite. B — Enclave of G1c granite within G1a granite, St. Agnes, Isles of Scilly Granite. C — Cligga G2 Granite with sheeted W greisen veins. D — Coarse-grained porphyritic G3a granite with abundant orthoclase phenocrysts (&gt; 25 mm) from the Dartmoor Granite. E — Globular quartz G4b granite from Carn Dean Quarry, Land's End Granite. F — Pegmatitic pocket dominantly comprising tourmaline, orthoclase and quartz within G3a granite, Land's End Granite. G — Typical topaz (G5) granite texture, equigranular with abundant Li mica, Tregonning Granite. Mineral name abbreviations: Kfs = potassium feldspar, Bt= biotite, Msc = muscovite, Qtz = quartz, Tur = tourmaline, Mca = mica. From: Simons, B.; Andersen, J. C.Ø.; Shail, R.K.; Jenner, F.E. (2017) "Fractionation of Li, Be, Ga, Nb, Ta, In, Sn, Sb, W and Bi in the peraluminous Early Permian Variscan granites of the Cornubian Batholith: Precursor processes to magmatic-hydrothermal mineralisation", Lithos, Volumes 278–281, Pages 491–512, Figure 2. https://doi.org/10.1016/j.lithos.2017.02.007
context_page_description: The Cornubian batholith is a large mass of granite rock, formed about 280 million years ago, which lies beneath much of the south-western peninsula of Great Britain. The main exposed masses of granite are seen at Dartmoor, Bodmin Moor, St Austell, Carnmenellis, Land's End and the Isles of Scilly. The intrusion is associated with significant quantities of minerals particularly cassiterite, an ore of tin which has been mined since about 2000 BC. Other minerals include china clay and ores of copper, lead, zinc and tungsten.
  It takes its name from Cornubia, the Medieval Latin name for Cornwall.
context_section_description: The main rock forming the batholith is granite, which formed when magma cooled slowly, covered by 2–3,000 metres of slate and sandstone. The slow cooling gave time for crystals to form in the granite which are large enough to see with the naked eye, giving it a granular appearance. These grains are mainly of quartz, feldspar and biotite. The granite is generally coarse grained and in some places very coarse-grained, or pegmatitic (grains larger than 3 cm). Large phenocrysts, several centimetres long, of K-feldspar, are a distinctive feature.
  The chemistry and mineralogy of the granites vary from one location to another, but they are all classified on the Chappell & White classification as being S-type, which means that they are ultimately derived from sedimentary rock protolith.
caption: Field photographs of Cornubian Batholith granites. A — Typical G1a granite with orthoclase phenocrysts (< 25 mm) from the Carnmenellis Granite. B — Enclave of G1c granite within G1a granite, St. Agnes, Isles of Scilly Granite. C — Cligga G2 Granite with sheeted W greisen veins. D — Coarse-grained porphyritic G3a granite with abundant orthoclase phenocrysts (> 25 mm) from the Dartmoor Granite. E — Globular quartz G4b granite from Carn Dean Quarry, Land's End Granite. F — Pegmatitic pocket dominantly comprising tourmaline, orthoclase and quartz within G3a granite, Land's End Granite. G — Typical topaz (G5) granite texture, equigranular with abundant Li mica, Tregonning Granite. Mineral name abbreviations: Kfs = potassium feldspar, Bt= biotite, Msc = muscovite, Qtz = quartz, Tur = tourmaline, Mca = mica.
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