A paleoproterozoic intra-arc basin associated with a juvenile source in the Southern Brasilia Orogen: Application of U–Pb and Hf–Nd isotopic analyses to provenance studies of complex areas

Abstract Extension within a continental back‐arc basin initiates within continental rather than oceanic lithosphere, and the geochemical characteristics of magmatic rocks within continental back‐arcs are poorly understood relative to their intraoceanic counterparts. Here, we compile published geochemical data from five exemplar modern continental back‐arc basins—the Okinawa Trough, Bransfield Strait, Tyrrhenian Sea, Patagonia plateau, and Aegean Sea/Western Anatolia—to establish a geochemical framework for continental back‐arc magmatism. This analysis shows that continental back‐arcs yield geochemical signatures more similar to arc magmatism than intraoceanic back‐arcs do. We apply this framework to published data for Triassic‐Jurassic magmatic rocks from the Caucasus arc system, which includes a relict continental back‐arc, the Caucasus Basin, that opened during the Jurassic and for which the causal mechanism of formation remains debated. Our analysis of 40 Ar/ 39 Ar and U‐Pb ages indicates Permian‐Triassic arc magmatism from ∼260 to 220 Ma due to subduction beneath the Greater Caucasus and Scythian Platform. Late Triassic (∼220–210 Ma) collision of the Iranian block with Laurasia likely induced trench retreat in the Caucasus region and led to migration of the Caucasus arc and opening of the Caucasus Basin. This activity was followed by Jurassic arc magmatism in the Lesser Caucasus from ∼180 to 140 Ma and back‐arc spreading in the Caucasus Basin from ∼180 to 160 Ma. Trace element and Sr‐Nd isotopic data for magmatic rocks indicate that Caucasus Basin magmatism is comparable to modern continental back‐arcs and that the source to the Lesser Caucasus arc became more enriched at ∼160 Ma, likely from the cessation of back‐arc spreading.

Back-arc basin

Continental arc

Continental Margin

Tethys Ocean

continental collision

Island arc

10.1029/2020gc009490

Cite

Citations (18)

Stromatolitic bioherms and microphytolites from the late proterozoic draken conglomerate formation, spitsbergen

Precambrian Research (1985)

Keene Swett Andrew H. Knoll

Siliciclastic

Conglomerate

Microbial mat

10.1016/0301-9268(85)90037-3

Cite

Citations (49)

Isotopic and geochemical record of the active to passive margin transition in NW Iberia during the Cambrian-Ordovician: vestiges of a waning continental arc

Journal of Iberian Geology (2021)

Pilar Andonaegui Rubén Díez Fernández Jacobo Abati

Continental arc

Back-arc basin

Continental Margin

Passive margin

Allochthon

10.1007/s41513-020-00155-8

Cite

Citations (4)

Coeval high Ba-Sr arc-related and OIB Neoproterozoic rocks linking pre-collisional magmatism of the Ribeira and Araçuaí orogenic belts, SE-Brazil

Precambrian Research (2019)

Felipe Corrales Ivo Dussin Mônica Heilbron Henrique Bruno Samuel Moreira Bersan

Continental arc

Back-arc basin

Lile

Felsic

Continental Margin

Island arc

Adakite

10.1016/j.precamres.2019.105476

Cite

Citations (29)

Incorporation of sedimentary rocks into the deep levels of continental magmatic arcs: Links between the North Cascades arc and surrounding sedimentary terranes

Geological Society of America eBooks (2018)

Stacia M. Gordon Robert B. Miller Kirsten Sauer

The incorporation of metasedimentary rocks into the mid- to deep crust of continental magmatic arcs has significant mechanical and geochemical consequences for arc systems. The Late Cretaceous–Eocene North Cascades arc is one of the few continental magmatic arcs in the world that exposes a large amount of exhumed deep-crustal metasedimentary rocks. Here, we investigate a range of processes that may have been important in transferring sediment into the arc by combining field mapping with bulk-rock Nd analyses, U-Pb and Hf-isotopic study of detrital zircons, and U-Pb dating of zircon and monazite to determine the timing of metamorphism and melt crystallization from metasedimentary samples collected in two deep-crustal domains of the North Cascades (the Skagit Gneiss and Swakane Gneiss). We also use these data to examine provenance links between the metasedimentary rocks and potential sediment sources in the accretionary wedge (western mélange belt), the forearc (Nooksack Formation), and the present-day backarc (Methow terrane) to the North Cascades arc.

Forearc

Accretionary wedge

Back-arc basin

Continental arc

Continental Margin

Island arc

10.1130/2017.0049(06)

Cite

Citations (5)

Palaeoenvironmental Reconstruction of the Early Proterozoic Kolhan Siliciclastic Rocks, Keonjhar District, Orissa, India

Journal of the Geological Society of India (1990)

Sumit Ghosh B. Chatterjee