Geochemistry of feldspars and muscovite in granitic pegmatite from the Cap de Creus Field, Catalonia, Spain

The Cap de Creus pegmatites in NE Spain show a well-defined zonation: 1) barren K-feldspar-rich, 2) beryl-columbite-subtype, 3) beryl-columbite-phosphate-subtype and 4) albite-type. There is an increase in the albite/K-feldspar ratio with increasing pegmatite evolution. The K/Rb value in K-feldspar decreased progressively from type (1) to type (3) pegmatites: there is also a progressive enrichment in P, Rb, Cs, Y, Sr, Ga, Ce, W and Sn from types (1) to (4). Amounts of Pb and Zr decrease in K-feldspar from types (1) to (3); the cap de Creus K-feldspars are richer in Ba, Rb, Cs, Nb, Y, Sn, V and Cr than the albite. The latter is richer in Sr, Zr, Cu, As and Ce. The muscovite shows similar geochemical evolution to K-feldspar. The high P content of feldspars, P (sub 2) O (sub 5) < or = 1.67 wt.% in K-feldspar and 1.75 wt.% in albite, indicates a buildup in P from the earliest stages of pegmatite crystallization. The P content of albite is suggested as a useful guide to Nb-Ta mineralization.