Publication: Rutilos ricos en Zr incluidos en granates de xenolitos granulíticos
de la corteza inferior del Sistema Central Español: implicaciones
geodinámicas
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Publication Date
2008
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Sociedad Geológica de España
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Abstract
Two petrographic types of rutile are observed in the peraluminous felsic meta-igneous granulites, the most
common type of the lower crustal xenolith suite of the Spanish Central System (SCS). Rutile-1 (Rt-1)
corresponds to small crystals (mainly < 80 mm) only preserved as micro-inclusions within garnet, whereas
rutile-2 (Rt-2) is commonly found as big idiomorfic crystals forming the granulite granoblastic matrix.
Chemical analyses by EMP show a higher Zr content in Rt-1 (up to 7800 ppm) than in Rt-2 (up to 5200
ppm) of the same granulite. Applying Zr-in-rutile thermometry, Rt-1 gives 50-60 ºC higher for rutile
crystallization (950-1015 ºC) when compared to Rt-2 thermometry (940-955 ºC). These ultra-high
temperatures (UHT) are likely attained at Moho depths without external heat sources (e.g. mantle input)
as supported by the high heat production estimated for the crustal section of the SCS. The granulitegranite
petrogenetic link suggests that these HT-UHT granulites were generated by intra-crustal reworking
during Hercynian continental thickening.