Sedimentation and volcanism in the Panamanian Cretaceous intra-oceanic arc and fore-arc: New insights from the Azuero peninsula (SW Panama)

Abstract

The Azuero Peninsula, located in SW Panama, is a region characterized by a long-lived intra-oceanic subduction zone. Volcanism began in Late Cretaceous time, as the result of subduction of the Farallon plate beneath the Caribbean plate. Usually, ancient volcanic arcs related to intra-oceanic subduction zones are not preserved, because they are in areas with difficult access or covered by modern volcanic arc material. However, on the Azuero peninsula, a complete section of the volcanic arc together with arc basement rocks provides the opportunity to study the sedimentation and volcanism in the initial stages of volcanic arc development. The lithostratigraphic unit which records fore-arc evolution is the “Río Quema” Formation (RQF), a volcanic apron composed of volcanic and volcaniclastic sedimentary rocks interbedded with hemipelagic limestones, submarine dacite lava domes, and intruded by basaltic-andesitic dikes. The “Río Quema” Formation, interpreted as a fore-arc basin infilling sequence, lies discordantly on top of arc basement rocks. The exceptionally well exposed arc basement, fore-arc basin, volcanic arc rocks and arc-related intrusive rocks provide an unusual opportunity to study the relationship between volcanism, sedimentation and magmatism during the arc development, with the objective to reconstruct its evolution. The “Río Quema” Formation can be divided into three groups: 1) proximal apron, a sequence dominated by lava flows, interbedded with breccias, mass flows and channel fill, all intruded by basaltic dikes. The rocks represent the nearest materials to the volcanic source, reflecting a coarse sediment supply. This depositional environment is similar to gravel-rich fan deltas and submarine ramps; 2) medial apron, characterized by a volcanosedimentary succession dominated by andesitic lava flows, polymictic volcanic conglomerates and crystal-rich sandstones with minor pelagic sediments and turbidites. These rocks were deposited from high-density turbidity currents and debris flows, directly derived from erupted material and gravitational collapse of an unstable volcanic edifice or volcaniclastic apron; 3) distal apron, a thick succession of sandy to muddy volcaniclastic rocks, interbedded with pelagic limestones and minor andesitic lavas, intruded by dacite domes and by basaltic to andesitic dikes. Bedforms and fossils suggest a quiet, relatively deep-water environment characterized by settling of clay and silt (claystone, siltstone) and by dilute turbidity currents of reworked volcaniclastic detritus. The timing of the initial stages of the volcanic arc has been constrained through a biostratigraphic study, using planktonic foraminifera and radiolarian species. The fossil assemblage indicates that the age of the “Río Quema” Formation ranges from Late Campanian to Maastrichtian, providing a good constraint for the development of the volcanic arc and volcaniclastic apron, during the initial stages of an intra-oceanic subduction zone.

Trace-metal content of the Cerro Quema Au-Cu deposit (Azuero Peninsula, Panama): Implications for exploration

“…As described in Buchs et al (2010Buchs et al ( , 2011 and Corral et al (2011Corral et al ( , 2013, the Azuero Arc Group (late Cretaceous to Eocene) overlies the Azuero Igneous Basement (Conacian to Santonian) and is discordantly overlapped by the Tonosí Formation (Eo-cene to Miocene). The Río Quema Formation is a volcanosedimentary sequence that represents the earliest calc-alkaline volcanism of the Azuero Arc Group.…”

“…The Cerro Quema high-sulfidation epithermal Au-Cu deposit covers an area of ~20 km 2 in the center of the Azuero Peninsula (Figure 1). The mineralization is hosted in the dacite dome complex of the Río Quema Formation (late Campanian to Maastrichtian; Corral et al, 2013Corral et al, , 2016. Peninsula and location of the Cerro Quema Au-Cu deposit (after Corral et al, 2013Corral et al, , 2016.…”

The source is in the sink: Deep‐water deposition by a submarine volcanic arc, Taranaki Basin, New Zealand

“…However, submarine volcanic apron facies documented elsewhere are characterized by common dyke intrusions and lava flows that are interbedded or in close lateral association with re‐sedimented volcanogenic deposits (e.g. Gamberi, ; Allen et al ., ; Corral et al ., ). Primary volcanic deposits and intrusions are absent from the Mohakatino Formation in the study area.…”

Rapid vertical motions and formation of volcanic arc gaps: Plateau collision recorded in the forearc geological evolution (Costa Rica margin)

“…Indeed, we assume that the present-day configuration of the margin is similar to the one that existed during the Late Cretaceous, since no significant block rotations were measured in northwestern Costa Rica and southwestern Nicaragua (Di Marco, Baumgartner, & Chanell, 1995;Elming, Layer, & Ubieta, 2001). (Calvo & Bolz, 1994;Flores et al, 2003a) hints at prolonged deposition on the slope of an island arc, implying distances to the source shorter than 100 km (see examples in: Carey, 2000;Allen & Freundt, 2006;Allen, Hayward, & Mathews, 2007;Manville, N emeth, & Kano, 2009;Corral, Gomez-Gras, Griera, Corbella, & Cardellach, 2013; Guerrera, Mart ın-Mart ın, Raffaelli, & Tramontana, 2015; Figure 8a). Moreover, the stacked, proximal to distal, ash-rich Berrugate facies of the Loma Chumico Fm.…”

“…Moreover, the stacked, proximal to distal, ash-rich Berrugate facies of the Loma Chumico Fm. (Calvo & Bolz, 1994;Flores et al, 2003a) hints at prolonged deposition on the slope of an island arc, implying distances to the source shorter than 100 km (see examples in: Carey, 2000;Allen & Freundt, 2006;Allen, Hayward, & Mathews, 2007;Manville, N emeth, & Kano, 2009;Corral, Gomez-Gras, Griera, Corbella, & Cardellach, 2013; Guerrera, Mart ın-Mart ın, Raffaelli, & Tramontana, 2015; Figure 8a). Hence, these different considerations are compatible with the hypothesis that the Berrugate Arc may have encroached on the Manzanillo Terrane during the Coniacian-Santonian.…”