The Tonian Embu Complex in the Ribeira Belt (Brazil): revision, depositional age and setting in Rodinia and West Gondwana

Autor(es)

Campanha, G. A. C. ^[1] ; Faleiros, F. M. ^[1] ; Cawood, P. A. ^{[2, 3]} ; Cabrita, D. I. G. ^[1] ; Ribeiro, V, B. ; Basei, M. A. S. ^[4]

Afiliação do(s) autor(es)

^[1] Univ Sao Paulo, Inst Geociencias, Sao Paulo - Brazil

^[2] Monash Univ, Sch Earth Atmosphere & Environm, Melbourne, Vic 3800 - Australia

^[3] Univ St Andrews, Dept Earth Sci, St Andrews KY16 9AL, Fife - Scotland

^[4] Ribeiro, B., V, Univ Sao Paulo, Inst Geociencias, Sao Paulo - Brazil

• Tipo de documento: Artigo Científico
• Fonte: Precambrian Research; v. 320, p. 31-45, JAN 2019.
• Citações Web of Science: 5

Resumo

The Embu Complex in the Neoproterozoic Ribeira Belt of Brazil provides a record of sedimentation associated with the Rodinia supercontinent and its subsequent deformation and metamorphism during assembly of West Gondwana. It is composed of a succession of variably migmatized pelitic schists and paragneisses, as well as minor calcsilicate rocks with quartzite intercalations, and orthogneiss. Detrital zircon U-Pb (LA-ICP-MS and SHRIMP) determinations for key samples of the Embu Complex in its type-area (West and Southwest of Sao Paulo City), and samples from neighboring units (Votuverava and Sao Roque groups) indicate distinct provenance histories and in combination with other data, discrete times of sediment accumulation. Detrital zircons from the Embu Complex are characterized by ages in the range 1500-1000 Ma and 2000-1700 Ma, with a very minor number of older ages. The youngest detrital grain is dated at 974 +/- 12 Ma. Metamorphic zircon overgrowths range from 850 to 570 Ma with age peaks at ca. 820-790 and 650-570 Ma. Thus, the depositional age of the Embu Complex is constrained to 970-850 Ma. The detrital zircons of the Votuverava and Sao Roque groups are dominated by ages in the range 2200-2000 Ma, along with minor Paleoproterozoic and Archean ages. The youngest detrital grains are similar to 1400 Ma (Votuverava Group) and similar to 1750 Ma (Sao Roque Group). Metamafic rocks from the Votuverava Group have crystallization ages of ca. 1300 Ma, with a higher metamorphic grade amphibolite showing a range of discordant ages with upper and lower intercepts of 1300 Ma and similar to 800 Ma, respectively. These results demonstrate that the Embu Complex was probably accreted to the Apiai Terrane during a Tonian (820-790 Ma) orogenic event, prior to final development of the Ediacaran Ribeira belt arc-related magmatism and a transcurrent shear zone system. The main source area for detrital zircons of the Embu Complex is likely to be the Grenville-Sveconorwegian-Sunsas orogen or time-equivalent regions rather than the central portions of the neighboring cratons. The Embu Complex geological context is consistent with accumulation on the margin of the Rodinia supercontinent. (AU)

• Processo FAPESP: 15/04487-7 - Metamorfismo e evolução tectônica do Cinturão Ribeira meridional: relações entre os terrenos Embu, Apiaí e Curitiba
• Beneficiário: Frederico Meira Faleiros
• Modalidade de apoio: Auxílio à Pesquisa - Regular