Integration of elemental and isotope data supports a Neoproterozoic Adamastor Ocean realm

Abstract

A robust elemental and isotopic dataset from Neoproterozoic igneous rocks discloses protracted consumption of oceanic lithosphere in the 3,000 km long orogenic system of southeastern South America. Time dependent isotopic variation trends suggest that Tonian-Cryogenian magmatic rocks formed in intra-oceanic supra-subduction settings, followed by Ediacaran magmatic arc building along Andean-type continental margins. Tectonic slices of basic-ultrabasic rocks associated with deep sea and exhalative rocks are interpreted as remnants of obducted oceanic lithosphere. Protracted closure of the oceanic realm resulted in a Himalayas-sized orogenic belt during Ediacaran-Cambrian collision, as recorded by voluminous aluminum-rich syn-collisional granites followed by post-collisional intrusions. The duration and rates of crust forming processes in island arc, continental margins and collisional settings imply that a vast Adamastor oceanic realm was consumed to form western Gondwana.

Goldilocks at the dawn of complex life: mountains might have damaged Ediacaran–Cambrian ecosystems and prompted an early Cambrian greenhouse world

“…3 ). This matches the time interval between closure of the Goiás-Pharusian and Adamastor oceans 11 , 12 , 18 (Fig. 5 ) and roughly coincides with the onset of the regional Gaskiers glaciation, recognized in parts of South America 40 .…”

“…15 Myr, syn-collisional crustal anatexis and peak metamorphic conditions were attained in the Araçuaí-Ribeira Orogen to the east of the São Francisco paleocontinent, marked by widespread 585–530 Ma aluminous granites and high-grade rocks 19 . This orogen was formed through closure of the V-shaped Adamastor ocean 12 , with collision of the Paranapanema/Rio de La Plata, São Francisco-Congo and Kalahari paleocontinents (Figs. 5 , 6 c).…”

“…Provenance of the Marinoan glacial diamictite and related units reflects the erosion of mainly cratonic sources, with the main Neoproterozoic detrital zircon peak at ca. 900 Ma and sparse crystals with a youngest peak at 670 Ma 56 , 57 that might have been transported in volcanic ash clouds derived from surrounding island arcs 12 (Fig. 6 a,d).…”

“…Although plate tectonics under regimes of shallower and hotter subduction might have operated since the Mesoarchean (“Proterozoic-style plate tectonics” 4 ), a change to modern-style plate tectonics characterized by deep subduction and colder thermal gradients apparently occurred in the Neoproterozoic, as suggested by the global distribution of ophiolites, blueschists and UHP (Ultra-High Pressure) rocks 4 , 5 , especially in the Pan-African/Brasiliano orogens that formed during the amalgamation of Gondwana 7 , 8 , 11 , 12 . This is a consequence of secular cooling of the mantle, which by the end of the Neoproterozoic might have cooled sufficiently to allow widespread cold and dense lithosphere slabs to collapse into the underlying asthenosphere without loosing its coherence.…”

Tectono‐Metamorphic Evolution of the Northern Dom Feliciano Belt Foreland, Santa Catarina, Brazil: Implications for Models of Subduction‐Driven Orogenesis

“…600 Ma, have dominated much of the research surrounding formation of the SANOS (Basei et al., 2000, 2018; Heilbron et al., 2020; Heilbron & Machado, 2003). The primary evidence used to support this argument is a linear series of granitic batholiths intruding the western hinterland of the orogenic system, which are interpreted as the exhumed roots of magmatic arcs (Basei et al., 2000, 2018; Caxito et al., 2021; Heilbron & Machado, 2003; Pedrosa‐Soares et al., 2001; Tedeschi et al., 2016). These include the Granite Belt in the Dom Feliciano Belt (sensu Basei et al., 2000), the Rio Doce arc in the Araçuaí Belt (Tedeschi et al., 2016), and various magmatic complexes in the Ribeira Belt (Heilbron et al., 2020).…”