Petrogenesis of highly fractionated I-type peraluminous granites: La Pedriza pluton (Spanish Central System)

作者：Perez Soba Cecilia^*; Villaseca Carlos

来源：Geologica Acta, 2010, 8(2): 131-149.

DOI：10.1344/105.000001527

• Hercynian-Variscan orogeny
• Peraluminous I-type granites
• High field strength elements
• Multiple intrusions

The La Pedriza pluton stands out as the most extensively fractionated granite (Rb < 629; Sr < 2 and Ba < 2 ppm) of the Spanish Central System Batholith. These granites show a strong enrichment in some rare metal contents (Nb = 44, Y = 136, Yb = 10.7, U = 17, Ta = 7, Sc = 15 ppm). The petrography and geochemistry (including Sr-Nd isotopes) reveal that the pluton is composed of at least four units. These are classified as I-type peraluminous leucogranites (A/CNK=1.03-1.17), P-poor (P(2)O(5)<0.2 wt%) and Na(2)O-rich (<4.24 wt%) exhibiting differences in their HFSE and REE contents and epsilon Nd compositions. Moreover, the units of the La Pedriza granite display different trends of fractional crystallization. REE spectra of the two most fractionated units suggest the involvement of a fluorine-rich melt in the last stages favouring the crystallization of xenotime and niobotantalates. Intermediate meta-igneous granulite protoliths are proposed as source rocks. The most evolved units of the La Pedriza pluton show chemical features convergent to A-type granites; these are explained by extensive fractional crystallization of a P-poor, I-type granite magma.

• 出版日期2010-6