A telltale signature of Archean lithospheric mantle in the Paraná continental flood basalts genesis

Tracking the Transition From a Gondwana LIP to the South Atlantic Ocean With Geochronological and Geochemical Indicators

“…Sr and Nd ratios are plotted in Figure 3a along with South Atlantic MORB and E‐MORB compositions (Gale et al., 2013; and references therein), low‐Ti Paraná‐Etendeka Ribeira and Esmeralda basalts (Marques et al., 1999; Peate, 1997; Rocha‐Júnior et al., 2013, 2020; and references therein), and petrogenetic mixing curves that will be further described and discussed in Section 5.2.3.…”

“…However, given the large similarities between Ribeira-type dykes and Ribeira basalts, the petrogenetic approach proposed by Rocha-Júnior et al ( 2020) must be taken into consideration. The Ribeira basalts occur in very specific areas of Northwest and East Paraná-Etendeka Province where ancient ocean closures took place, and exhibit unradiogenic 187 Os/ 188 Os signatures that preclude significant crustal assimilation (Rocha-Júnior et al, 2020;and references therein). The authors suggested that subduction of Archean slabs in restricted regions of the SCLM resulted in 87 Sr/ 86 Sr enrichment and 187 Os/ 188 Os depletion.…”

A record of the transition between Gondwana and South Atlantic crust in the tholeiitic intrusive magmatism of Cabo Frio Tectonic Domain, Southeast Brazil

“…20.6; 1.2 ≤ La/Nb ≤ 1.4; 3.5 ≤ La/Hf ≤ 5.5) are similar to the Paraná-Etendeka low-Ti Ribeira basalts (e.g.,Rocha-Júnior et al, 2020). These similarities are evident in other trace element diagrams (Fig.S4of supporting information).Rare earth element (REE) patterns of MORB-and Ribeira-type dykes were normalized to CI chondrite(McDonough & Sun, 1995; Figs.…”

“…The LTi mafic dykes, the main focus of this investigation, can be grouped into two distinct magma suites: the first one, more primitive, shares many geochemical affinities with South Atlantic N-MORB and E-MORB rocks (normal/enriched mid-ocean ridge basalts; Bennio et al, 2003;Gale et al, 2013;Almeida et al, 2021); the second one, more enriched, is similar to LTi basalts from the Northern Paraná-Etendeka provinces (Bennio et al, 2003;Carvas, 2016;Rocha-Júnior et al, 2020). Analogously to recent rifts, such as the Red Sea (e.g., Ligi et al, 2018;Niu, 2021), MORB magma ascent from the asthenosphere was likely promoted by a local shallow Moho discontinuity (~38 km; Assumpção et al, 2002) resulting from a complex tectonic history (e.g., Fernandes et al, 2015;Schmitt et al, 2008Schmitt et al, , 2016.…”

“…) and calculated mixing curves between DMM-pyroxenite compositions (representative of ancient mantle edges within the SCLM) and a 87 Sr-rich Archean SCLM. Mafic alkaline rocks from the northeastern Paraná-Etendeka province mostly derived from mantle sources affected by metasomatism of recycled Paleoproterozoic/Archean slabs(Araújo et al, 2001;Rocha-Júnior et al, 2020; and references therein), and their compositions were used to estimate the 87 Sr-rich component. A 1-3% Archean SCLM contribution applied to a 100-96% DMM -0-4% pyroxenite mantle component (metasomatized lithospheric mantle) successfully models the signatures of Ribeira-type dykes (Fig.3.3A).The involvement of metasomatized lithospheric magmas in the Ribeira-type magmatism at the Cabo Frio Tectonic Domain is consistent with the negative Nb and Ta anomalies and most of the REE behavior (Figs.…”