Metasomatic Hornfelses of the Land's End Aureole at Tater-du, Cornwall

At Tater-du, in the south of the Penwith peninsula, Cornwall,occurs a small isolated part of the Land's End aureole whichhas not been described in detail before. The aureole rocks hereare mostly banded amphibolitic hornfelses, some of which areof metasomatic origin. The metasomatic hornfelses can be divided into (1) Fe-Mg hornfelsescontaining anthophyllite, cummingtonite, and cordierite; (2)Ca hornfelses containing diopside, grossularite, epidote minerals,and axinite; and (3) K hornfelses containing a very high proportionof biotite. All three types are considered to have been derivedfrom hornblende hornfelses (‘greenstone-hornfelses’)of basic intrusive origin. Data are presented indicating their originally intrusive natureand similarity to other metasomatic hornfelses in the aureoleat Kenidjack and Botallack (Tilley, 1935). The Fe-Mg and Cahornfelses are considered to have resulted from the internalmigration of the Ca ion during metamorphism and the K hornfelsesfrom the allochemical addition of K from the granite.