Nd-model ages calculated with respect to a depleted mantle source (T(DM)) have been widely applied to granitoids in order to date events of mantle-crust differentiation, often referred as "crustal residence ages". The basic assumption for a Nd-model age to represent a crustal residence age is that intracrustal processes such as interactions with fluids, partial melting and fractional crystallization cause little or no fractionation of the Sm - Nd pair. The present study reports on the geochemistry and Sm - Nd isotopes of leucogranites from the Budduso' intrusion, belonging to the Hercynian orogeny in Northern Sardinia (Italy). It is shown that fractionation of a LREE-rich mineral phase as allanite causes a significant variation of the Sm/Nd ratio in the residual melt, thus inducing biased Nd-model ages which have no direct meaning of crustal residence ages.

BIASED ND-MODEL AGES IN HIGHLY EVOLVED GRANITES - AN EXAMPLE FROM THE BUDDUSO INTRUSION (NE SARDINIA, ITALY) / Castorina, Francesca; R., Petrini. - In: NEUES JAHRBUCH FUR MINERALOGIE MONATSHEFTE. - ISSN 0028-3649. - STAMPA. - 6:(1992), pp. 277-288.

BIASED ND-MODEL AGES IN HIGHLY EVOLVED GRANITES - AN EXAMPLE FROM THE BUDDUSO INTRUSION (NE SARDINIA, ITALY)

CASTORINA, Francesca;
1992

Abstract

Nd-model ages calculated with respect to a depleted mantle source (T(DM)) have been widely applied to granitoids in order to date events of mantle-crust differentiation, often referred as "crustal residence ages". The basic assumption for a Nd-model age to represent a crustal residence age is that intracrustal processes such as interactions with fluids, partial melting and fractional crystallization cause little or no fractionation of the Sm - Nd pair. The present study reports on the geochemistry and Sm - Nd isotopes of leucogranites from the Budduso' intrusion, belonging to the Hercynian orogeny in Northern Sardinia (Italy). It is shown that fractionation of a LREE-rich mineral phase as allanite causes a significant variation of the Sm/Nd ratio in the residual melt, thus inducing biased Nd-model ages which have no direct meaning of crustal residence ages.
fractional crystallization; hercynian leukogranites; nd-model ages
01 Pubblicazione su rivista::01a Articolo in rivista
BIASED ND-MODEL AGES IN HIGHLY EVOLVED GRANITES - AN EXAMPLE FROM THE BUDDUSO INTRUSION (NE SARDINIA, ITALY) / Castorina, Francesca; R., Petrini. - In: NEUES JAHRBUCH FUR MINERALOGIE MONATSHEFTE. - ISSN 0028-3649. - STAMPA. - 6:(1992), pp. 277-288.
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11573/67199
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