In situ isotopic analyses of U and Pb in zircon by remotely operated SHRIMP II, and Hf by LA-ICP-MS: an example of dating and genetic evolution of zircon by 176Hf/177Hf from the Ita quarry in the Atuba Complex, SE Brazil

Authors

  • Kei Sato Universidade de São Paulo; Instituto de Geociências; Centro de Pesquisas Geocronológicas
  • Oswaldo Siga Jr Universidade de São Paulo; Instituto de Geociências; Centro de Pesquisas Geocronológicas
  • Josiane Aline da Silva Universidade de São Paulo; Instituto de Geociências; Programa de Pós-graduação em Geoquímica e Geotectônica
  • Ian McReath Universidade de São Paulo; Instituto de Geociências; Centro de Pesquisas Geocronológicas
  • Liu Dunyi Beijing SHRIMP Center; Institute of Geology
  • Tsuyoshi Iizuka Tokyo Institute of Technology
  • Shuji Rino Tokyo Institute of Technology
  • Takafumi Hirata Tokyo Institute of Technology
  • Walter Sproesser Universidade de São Paulo; Instituto de Geociências; Centro de Pesquisas Geocronológicas
  • Miguel Angelo Stipp Basei Universidade de São Paulo; Instituto de Geociências; Centro de Pesquisas Geocronológicas

DOI:

https://doi.org/10.5327/Z1519-874x2009000300004

Keywords:

Remotely-controlled SHRIMP II, Zircon dating, LA-ICP-MS, Hf isotopic composition, Atuba Complex, SE Brazil

Abstract

Remotely-operated SHRIMP dating of zircon is an interesting alternative for dating of zircon crystals. Although it does not represent any technical progress of the geochronological method using the U-Pb system in zircon it is a very useful and cheap facility. The procedure was first used for mass spectrometric analyses involving two international laboratories in São Paulo, Brazil and Beijing, China. It was applied to samples of three gneiss-migmatitic rocks from the Ita quarry in the Atuba Complex (located between the Luis Alves and the Apiaí Domain) to test previous controversial hypotheses about its evolution. The presence of important archean and paleoproterozoic components in the complex is confirmed by analyses of zircon found in probably neoproterozoic leucosomes. Diorite intrusion also occurred during the neoproterozoic, associated with the 0.6Ga continental collisions involved in the assembly of Gondwana. The determination of Hf isotope ratios by LA-ICP/MS represents a new option for checking the relative importance of mantle (εHf >; 0) and crustal contributions (εHf < 0) during the growth of the zircon crystals. While the archean component in the complex was derived from the mantle (εHf +1.5 to +8.7) the paleoproterozoic component had a crustal contribution (εHf-9.1 to -10.1).

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Published

2009-10-01

Issue

Vol. 9 No. 3 (2009)

Section

Articles

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How to Cite

Sato, K., Siga Jr, O., Silva, J. A. da, McReath, I., Dunyi, L., Iizuka, T., Rino, S., Hirata, T., Sproesser, W., & Basei, M. A. S. (2009). In situ isotopic analyses of U and Pb in zircon by remotely operated SHRIMP II, and Hf by LA-ICP-MS: an example of dating and genetic evolution of zircon by 176Hf/177Hf from the Ita quarry in the Atuba Complex, SE Brazil . Geologia USP. Série Científica, 9(3), 61-69. https://doi.org/10.5327/Z1519-874x2009000300004