Geochemistry and provenance of the metasedimentary rocks surrounding the Santa Quiteria magmatic arc, NE Brazil: Tectonic and paleogeographic implications for the assembly of West Gondwana

Author(s)

Mendes, Luiza de Carvalho ^[1] ; Saraiva dos Santos, Ticiano Jose ^[1] ; Gomes, Nadia Borges ^[1]

Affiliation

^[1] Univ Estadual Campinas, Geosci Inst, BR-13083855 Campinas - Brazil

• Document type: Journal article
• Source: Precambrian Research; v. 356, MAY 2021.
• Web of Science Citations: 0

Abstract

Western Gondwana resulted from the closure of the Pharusian-Goianides Ocean, a process that culminated in the formation of magmatic arcs, high and ultra-high-pressure (HP-UHP) belts, and sedimentary basins. These tectonic units occur in the NW part of the Borborema Province (Northeastern Brazil), which encloses the Neoproterozoic Santa Quiteria magmatic arc (SQMA). Metasedimentary rocks (sillimanite-, garnet- and biotite-bearing gneiss, quartzite, and schist) that constitute the Caninde Complex and the Independencia Unit surround the western and eastern margins of this arc. According to A/CNK and N/K ratios and the Chemical Index of Alteration calculated for each rock type, the protolith of these rocks correspond to moderately weathered pelites, greywacke, and lithic-arenite. Trace element distributions (LITE, HFSE and REE) indicate that the Caninde Complex rocks are depleted in Sc, V, Cr, Co, Ni and LILE and are formed by mature and stable minerals such as quartz, muscovite and K-feldspar, similarly to passive margin sediments. In contrast, the Independencia rocks present higher concentrations of transition trace elements, constituted by unstable-system minerals (iron-magnesium minerals) and immature sediments, typical of active margin settings. In general, these rocks present felsic-source components, with ample fractionation between LREE over HREE (La-N/Yb-N = 26.2 to 4.16) and with a slight to strong negative Eu anomaly (Eu/Eu{*} = 1.26 to 0.33). Isotopic Hf data identified a mixture of crustaland mantle-derived sources. According to tectonic setting discrimination diagrams (Co-Th-Zr/10 and Sc-Th-Zr/10) and the concentrations of characteristic trace elements and ratios (e.g., Th, V, Co, La, Ce, La-N/Yb-N), these rocks were interpreted as being deposited in basins formed in active and passive margin settings associated with continental and intraoceanic arcs. U-Pb zircon data indicates source rocks from the Archean (3.0 to 2.6 Ga) to the Neoproterozoic (820 to 541 Ma). According to our results, the Caninde and Independencia supracrustal rocks were deposited in basins affected by different tectonic regimes, controlled by the installation of the Santa Quiteria Magmatic Arc (SQMA), starting with a passive margin or intracratonic basins that evolved into an active margin setting on the western SQMA margin (Caninde Complex) and a predominantly passive margin setting on the eastern SQMA margin (Independencia Unit), leading to the formation of forearc and backarc basins. (AU)

• FAPESP's process: 16/08289-8 - EAST BORDER OF THE SANTA QUITÉRIA MAGMATIC ARC: A NEW ULTRA-HIGH PRESSURE BELT IN THE CEARÁ CENTRAL DOMAIN?
• Grantee: Ticiano José Saraiva dos Santos
• Support Opportunities: Regular Research Grants
• FAPESP's process: 17/09206-1 - Thermobarometric evolution (P-T) of the volcano sedimentary rocks of the eastern edge of the Magmatic Arc of Santa Quitéria, Ceará
• Grantee: Nádia Borges Gomes
• Support Opportunities: Scholarships in Brazil - Master