Geochemistry and age of mafic rocks from the Votuverava Group, southern Ribeira Belt, Brazil: evidence for 1490Ma oceanic back-arc magmatism

Campanha, G. A. C., Faleiros, F. M., Basei, M. A. S., Tassinari, C. C. G., Nutman, A. P. and Vasconcelos, P. M. (2015) Geochemistry and age of mafic rocks from the Votuverava Group, southern Ribeira Belt, Brazil: evidence for 1490Ma oceanic back-arc magmatism. Precambrian Research, 266 530-550. doi:10.1016/j.precamres.2015.05.026


Author Campanha, G. A. C.
Faleiros, F. M.
Basei, M. A. S.
Tassinari, C. C. G.
Nutman, A. P.
Vasconcelos, P. M.
Title Geochemistry and age of mafic rocks from the Votuverava Group, southern Ribeira Belt, Brazil: evidence for 1490Ma oceanic back-arc magmatism
Journal name Precambrian Research   Check publisher's open access policy
ISSN 0301-9268
1872-7433
Publication date 2015-09-01
Year available 2015
Sub-type Article (original research)
DOI 10.1016/j.precamres.2015.05.026
Open Access Status Not yet assessed
Volume 266
Start page 530
End page 550
Total pages 21
Place of publication Amsterdam, Netherlands
Publisher Elsevier
Language eng
Subject 1907 Geology
1906 Geochemistry and Petrology
Abstract This paper presents new SHRIMP U-Pb zircon and 40Ar-39Ar hornblende ages as well as elemental and Sr-Nd isotopic data for greenschist to amphibolite facies meta-mafic rocks from the Votuverava Group (Ribeira Belt, Brazil). These mafic rocks appear to be mostly subvolcanic and volcanic rocks and, in part, intrusions coeval with the host sedimentary succession. Magmatic zircons have a U-Pb age of 1488±4Ma. An 40Ar-39Ar hornblende age of 1390±20Ma suggests cooling after a thermal event. The mafic rocks have chemical compositions of basalt and basaltic andesite (SiO2 of 45-55wt.%) of the tholeiitic series. Chemical data indicate the coexistence of rocks with BABB and E-MORB signatures. BABB-like rocks with a Ti/V of 9-20 show depletion in HFSE relative to MORB values and slightly fractionated REE patterns (Lacn/Ybcn of 0.8-1.8), while those with a Ti/V of 22-30 have HFSE contents similar to MORB and slightly more fractionated REE patterns (Lacn/Ybcn of 1.1-2.8). E-MORB-like rocks display a Ti/V of 27-41 and moderately fractionated REE patterns (Lacn/Ybcn of 3.6-5.3). The Nd(t) values ranged from -3.02 to +3.55. Whole rock Sm-Nd isotopic data yielded a regression with a slope of 1225±68Ma, which can be interpreted as a mixing line of no age significance that is related to different source components of the metabasic rocks. Elemental and Nd isotopic signatures suggest that the Votuverava metabasites originated from a MORB-type mantle source heterogeneously metasomatized by subduction processes. The data are consistent with magmatic activity in a back-arc basin environment. The 1490Ma mafic magmatism is associated with a 500-km-long and 60-km-wide Calymmian belt interpreted as an accretionary orogen. Available thermochronological data suggest that this accretionary orogen could have evolved into a collisional orogen in the period 1280-1100Ma, possibly related to the assembly of Rodinia. During the Brasiliano-Pan African cycle (650-550Ma), related to amalgamation of West Gondwana, this Calymmian belt represented by the Votuverava Group was dispersed as an exotic terrane along the Ribeira Belt.
Formatted abstract
This paper presents new SHRIMP U–Pb zircon and 40Ar–39Ar hornblende ages as well as elemental and Sr–Nd isotopic data for greenschist to amphibolite facies meta-mafic rocks from the Votuverava Group (Ribeira Belt, Brazil). These mafic rocks appear to be mostly subvolcanic and volcanic rocks and, in part, intrusions coeval with the host sedimentary succession. Magmatic zircons have a U–Pb age of 1488 ± 4 Ma. An 40Ar–39Ar hornblende age of 1390 ± 20 Ma suggests cooling after a thermal event. The mafic rocks have chemical compositions of basalt and basaltic andesite (SiO2 of 45–55 wt.%) of the tholeiitic series. Chemical data indicate the coexistence of rocks with BABB and E-MORB signatures. BABB-like rocks with a Ti/V of 9–20 show depletion in HFSE relative to MORB values and slightly fractionated REE patterns (Lacn/Ybcn of 0.8–1.8), while those with a Ti/V of 22–30 have HFSE contents similar to MORB and slightly more fractionated REE patterns (Lacn/Ybcn of 1.1–2.8). E-MORB-like rocks display a Ti/V of 27–41 and moderately fractionated REE patterns (Lacn/Ybcn of 3.6–5.3). The ɛNd(t) values ranged from −3.02 to +3.55. Whole rock Sm–Nd isotopic data yielded a regression with a slope of 1225 ± 68 Ma, which can be interpreted as a mixing line of no age significance that is related to different source components of the metabasic rocks. Elemental and Nd isotopic signatures suggest that the Votuverava metabasites originated from a MORB-type mantle source heterogeneously metasomatized by subduction processes. The data are consistent with magmatic activity in a back-arc basin environment. The 1490 Ma mafic magmatism is associated with a 500-km-long and 60-km-wide Calymmian belt interpreted as an accretionary orogen. Available thermochronological data suggest that this accretionary orogen could have evolved into a collisional orogen in the period 1280–1100 Ma, possibly related to the assembly of Rodinia. During the Brasiliano–Pan African cycle (650–550 Ma), related to amalgamation of West Gondwana, this Calymmian belt represented by the Votuverava Group was dispersed as an exotic terrane along the Ribeira Belt.
Keyword Ribeira Belt
Votuverava Group
Calymmian magmatism
Basic magmatism
Back-arc basin
Geochronology
Q-Index Code C1
Q-Index Status Confirmed Code
Grant ID 2001/13457-1 | 1996/05648-1 | 2006/01327-0
Institutional Status UQ

Document type: Journal Article
Sub-type: Article (original research)
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