Volcanogenic Quartz-Magnetite-Hematite Veins, Snowdon, North Wales

T. B. Colman and A.-K. Appleby
Applied Geochemistry Group, British Geological Survey, Keyworth, Nottingham NG12 5GG, U.K.
Placer Pacific, 5-7 Eyre Street, Belmont 6104, Western Australia

Abstract: In the Ordovician Snowdon Volcanic Group caldera quartz-magnetite-hematite-pyrite assemblages occur in a breccia vein in rhyolitic tuff and vein swarms in basalt. The veins developed pre-cleavage. Elevated levels of tin and tungsten in the veins, and of fluorine in the wall rocks, suggest a magmatic contribution to the mineralising fluids. The chemistry of the veins differs from that of the base-metal sulphide veins found elsewhere in the caldera.

Keywords: quartz • magnetite • hematite • Snowdon • Wales • volcanic rocks

Mineralogical Magazine; June 1991 v. 55; no. 379; p. 257-262; DOI: 10.1180/minmag.1991.055.379.14
© 1991, The Mineralogical Society
Mineralogical Society (www.minersoc.org)