Combined U-Pb and Lu-Hf isotope analyses by laser ablation MC-ICP-MS: methodology and applications

Anais da Academia Brasileira de Ciências

Massimo Matteini²  Elton L. Dantas¹  Marcio M. Pimentel¹  Bernhard Bühn¹ 

[1] ,Universidade de Brasília Instituto de Geociências Brasília DF ,Brasil

关键词: LA-MC-ICP-MS;    Lu-Hf;    U-Pb;    zircon;    Borborema Province;    LA-MC-ICP-MS;    Lu-Hf;    U-Pb;    zircão;    Província de Borborema;   

DOI  :  10.1590/S0001-37652010000200023

来源: SciELO

【 摘 要 】

The Lutetium-Hafnium isotopic system represents one of the most innovative and powerful tools for geochronology and isotopic studies. Combined U-Pb and Lu-Hf in situ analyses on zircon by LA-MC-ICP-MS permit to characterize isotopically the host magma from which it crystallized furnishing significant information for sediment provenance and crustal evolution studies. In this paper e describe the Lu-Hf systematic by LA-MC-ICP-MS developed in the laboratory of Geochronology of the University of Brasilia and report the results obtained by repeated analyses of 176Hf/177Hf isotopic ratio of three zircon standards: GJ-1 = 0.282022 ± 11 (n=56), Temora 2 = 0.282693 ± 14 (n=25) and UQZ = 0.282127 ± 33 (n=11). The 176Hf/177Hf ratio (0.282352 ± 22, n=14) of gem quality zircon used as in-house standard have been also characterized. As a geological application, we analyzed two complex zircons selected from a migmatitic rocks from the Borborema Province, NE Brazil. On the basis of U-Pb and Lu-Hf data, two main crystallization events have been identified in both studied zircons. An older event at ca. 2.05 Ga recognized in the inherited cores represents a well-characterized paleoproterozoic magmatic event that affected the whole Borborema Province. A second crystallization event at ~ 575 Ma, recognized at the rims, represents a Neoproterozoic (Brazilian) high grade metamorphic-magmatic event.

【 授权许可】

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