Origin and geodynamic significance of the Siuna Serpentinite Mélange, Northeast Nicaragua: Insights from the large-scale structure, petrology and geochemistry of the ultramafic blocks

Sedimentary Record of Arc‐Continent Collision Along Mesozoic SW North America (Siuna Belt, Nicaragua)

“…In this paper we present new sedimentary constraints on the early evolution of the only known exposure of the suture zone that separates two of the largest terranes in Central America, that is, the Siuna Intraoceanic Arc and the continental Chortis Block. This paper complements our recent study of the evolution of the Siuna Serpentinite Mélange (SSM; Escuder‐Viruete et al, ) and provides new constraints on the exhumation timing of the mélange along the suture zone between the two blocks, as well as the postcollisional evolution of the convergent margin. We also propose a model for the Early Cretaceous evolution of the margins of SW North America and the western proto‐Caribbean, some key steps of which may be explained by the collision of the Siuna Intraoceanic Arc.…”

“…The red rectangle represents the area covered by the geological map in Figure b. (b) Chronostratigraphic chart of the Siuna Belt (column 1, modified from: Venable, ; Baumgartner et al, ; Flores, ; Flores et al, ; Escuder‐Viruete et al, ) and the Chortis Block (columns 2 and 3, modified from: Gordon, ; Scott & Finch, ; Rogers, Mann, & Emmet, , Rogers, Mann, Emmet, & Venable, b, Rogers, Mann, Scott, & Patino, c). Note the chronostratigraphy of the Mixteca Terrane (SW Mexico) for comparison (modified from Sierra‐Rojas et al, ; Molina Garza et al, ).…”

“…To the southeast, the Eastern Chortis Terrane is bordered by an accreted intraoceanic arc assemblage of Jurassic‐Early Cretaceous age, called the Siuna Terrane (Rogers, Mann, & Emmet, ; Rogers, Mann, Emmet, & Venable, ; Venable, ) or the Mesquito Composite Oceanic Terrane (Baumgartner et al, ; Flores et al, ; Figures and ). Besides evidence built on field, geological, petrological, and geochemical data (Baumgartner et al, ; Escuder‐Viruete et al, ; Flores et al, ), the distinction between the Chortis continental terrane and the Siuna Intraoceanic Arc terrane is further based on their conspicuously different Pb isotope and gravity signatures (Rogers, Mann, & Emmet, ; Sundblad et al, ; Venable, ). The recognition of the exotic Siuna Intraoceanic Arc relies on the geology of the Siuna Belt, which was exposed due to Cenozoic strike‐slip fault activity (Escuder‐Viruete et al, ; Flores et al, ).…”

“…Besides evidence built on field, geological, petrological, and geochemical data (Baumgartner et al, ; Escuder‐Viruete et al, ; Flores et al, ), the distinction between the Chortis continental terrane and the Siuna Intraoceanic Arc terrane is further based on their conspicuously different Pb isotope and gravity signatures (Rogers, Mann, & Emmet, ; Sundblad et al, ; Venable, ). The recognition of the exotic Siuna Intraoceanic Arc relies on the geology of the Siuna Belt, which was exposed due to Cenozoic strike‐slip fault activity (Escuder‐Viruete et al, ; Flores et al, ). The bulk of the Siuna Intraoceanic Arc is covered by younger sedimentary and volcanic deposits elsewhere (Baumgartner et al, ), including offshore eastern Nicaragua (Carvajal‐Arenas & Mann, ; Sanchez et al, ).…”

“…The Siuna Belt consists of a serpentinite‐matrix mélange, the SSM, that is unconformably or tectonically overlain by a Hauterivian to Albian sedimentary‐volcanic succession (Venable, ; Baumgartner et al, ; Flores et al, ; Escuder‐Viruete et al, ; Figures and ). The belt is bounded by thrust faults on its western and eastern sides and flanked by Late Cretaceous to Eocene volcanic and volcaniclastic rocks.…”