Trace element mobility in tourmalinite veins and surrounding metapelites from the Crummock Water aureole (Lake District, England)

摘要

The Crummock Water aureole consists of Ordovician slates which have undergone retrogressive metamorphism and contains several fractures displaying tourmalinite wallrock alteration zones, which range in thickness from about a centimetre to a few metres. Several larger tourmalinite veins often occur together in anastomosing vein systems, continuing over several hundreds of m. Both rock types display low field strength element depletions which in the host rocks decrease on decimetre scale with increasing distance from the veins. REE, especially the LREE, display different degrees of mobility due to tourmalinisation, both in tourmalinites and host rocks close to the veins. For the tourmalinites, differences in REE mobility are possibly related to the position of the rock on the fluid circulation path along the fractures.