GEOCHEMISTRY OF K-FELDSPAR AND MUSCOVITE IN RARE-ELEMENT PEGMATITES AND GRANITES FROM THE TOTORAL PEGMATITE FIELD, SAN LUIS, ARGENTINA

J. C. OYARZÁBAL, M. A. GALLISKI AND E. PERINO

Resource Geology

Blackwell Publishing

Lugar: Tokyo; Año: 2009 vol. 59 p. 315 - 329

1344-1698

The geochemistry of K-feldspar for K, P, Sr, Ba, Rb, Cs, Ga, and ofmuscovite for the same elements plus Nb and Ta, was used for proving the parentalrelationships of S-type granites and LCT (Li, Cs, Ta) rare-element pegmatites in thesouthernmost pegmatitic field of the Pampean pegmatitic province in Argentina. Thevariation of K/Rb-Cs, K/Cs-Rb, K/Rb-Rb/Sr, K/Rb-Ba in K-feldspar from the granitesand pegmatites show that they form an association with the evolutional sequence:granites-barren- to transitional pegmatites-beryl type, beryl-columbite-phosphatepegmatites-complex type of spodumente subtype pegmatites-albite-spodumente type-albite type pegmatites. This sequence reflects the regional distribution of the differentmagmatic units. The Ta-Cs diagram for muscovite reveals that none of the studiedpegmatites exceed the threshold established in previous studies for being consideredwith important tantalum oxide mineralization.The granites and pegmatites form a rare-element pegmatitic field in whichdifferent magmatic units are petrogenetically linked forming a continuous fractionationtrend, extended from the less evolved granitic facies to the most geochemicallyspecialized pegmatites.