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The dolphinfish (Coryphaena hippurus) is a globally distributed marine predator that supports one of the most important coastal fisheries along the Eastern Tropical Pacific (ETP), but its spatial movements in this area are poorly understood. Stable isotope values (δ13C and δ15N) of white muscle from dolphinfish (n = 220) captured at different locations across the ETP (i.e., Mexico, Costa Rica, Ecuador, Peru and oceanic areas) were normalized to copepod baseline stable isotope values to estimate dolphinfish trophic position, movements and population dispersal. Movement or residence patterns were inferred from the difference in δ15N values (Δ15Ndolphinfish‐copepod‰) between copepods and dolphinfish muscle. Baseline corrected isotope values (δ13Cdolphinfish‐copepod and δ15Ndolphinfish‐copepod) of dolphinfish muscle were used to estimate isotopic niche metrics and infer population dispersal across isoscapes. Values of δ13C and δ15N differed between juvenile and adult dolphinfish and across the ETP. Trophic position estimates ranged from 3.1 to 6.0 with a mean of 4.6. Adults and juveniles had similar trophic position estimates, whereas isotopic niche areas (SEA ‰2) of adults were greater relative to juveniles in every location. Adult dolphinfish showed "moderate movement by some individuals" in all locations based on Δ15Ndolphinfish‐copepod values, except for Costa Rica where adults were classified with "high degree of movement by some individuals" whereas juveniles showed "limited movement" in all areas except Mexico. Population dispersal based on Δ15Ndolphinfish‐copepod values showed "moderate" and "high" dispersal for adults and "no dispersal" for most juveniles, except for Mexico. This study provides insight into potential dolphinfish spatial mobility across an area of interest for multiple nations, which can help to improve stock assessments and management of the species. [ABSTRACT FROM AUTHOR]

The Western Cordillera and forearc of the Northern Andes (north of 5° S) are constructed from allochthonous terranes floored by oceanic crust. A paucity of accurate geochronological data from the ultramafic and mafic basement sequences of the Western Cordillera and Coastal region of Ecuador has lead to distinct differences in published tectonic models, with different allochthonous units and contrasting timelines of accretion and collision. We present new zircon U Pb and groundmass 40Ar/39Ar dates of the basement units, which have been combined with new whole rock geochemical and isotopic data to constrain their tectonic histories prior to and during their accretion to South America. Ultramafic and mafic rocks with oceanic plateau affinities can be divided into two plateau sequences, where an inboard, younger plateau (85–92 Ma; Pallatanga Block) is sutured against South America, and was modified by a pre-accretionary intra-oceanic arc (Pilatón-Pujilí arc) that was terminated by the accretionary process. An older, outboard oceanic plateau sequence (∼120 Ma) forms the basement to a series of coastal blocks within the present forearc (Piñon, San Lorenzo, Pedernales and probably the Esmeraldas blocks). The outer plateau also hosts a pre-accretionary intra-oceanic arc (Pascuales – San Lorenzo arc), which remained active during and post-accretion (San Lorenzo – Rio Cala arc). Coeval changes in palaeomagnetic declination, the onset of rapid exhumation (>1 km/My) of the Early Cretaecous continental margin and sedimentation within the newly formed retro-arc foreland basin and foreland region supports a model where both oceanic plateau sequences accreted to South America in a single accretion event at 75–70 Ma. Thus, it is likely that the accreted oceanic plateau was composite, and included both the younger and older plateau sequences prior to accretion. We test an alternative model where the inner (younger) and outer (older) oceanic plateaus accrete in sequence, although this fails to account for the timing of block rotations in the forearc. • New zircon U Pb and 40Ar/39Ar dates define two oceanic plateau sequences in Ecuador. • Oceanic plateaus crystallised during 85–92 Ma and at approximately 120 Ma. • Pre-accretionary intra-oceanic arcs modified both oceanic plateaus. • All oceanic plateau sequences accreted to Ecuador in a single accretionary event. [ABSTRACT FROM AUTHOR]

Tectonic models of the Early Cretaceous Andean margin in Ecuador are hindered by a paucity of accurate crystallisation ages of igneous rocks. The Alao Arc, situated on the western flank of the Cordillera Real in Ecuador, is mainly composed of submarine altered basalts to andesites, and the most deformed areas are frequently modified by greenschist metamorphism. To improve our knowledge of the evolution of the northern Andes prior to the accretion of the Caribbean Large Igneous Province we attempt to constrain the tectonic origin and crystallisation age of the arc's volcanic rocks, using whole-rock geochemistry and isotopic tracing, combined with 40Ar/39Ar geochronology. Major oxides and trace element abundances and Sr-Nd-Pb compositions show that the Alao Arc comprises two separate assemblages, namely, typical arc-like volcanic rocks and E -MORB-like basalts. These have been interpreted to have formed in a continental arc above thinned continental crust in an extensional setting, and the E -MORB-type basalts are considered to have formed in an intra-arc rift. As the Alao Arc's volcanic rocks are devoid of zircon and baddeleyite we attempted to date the time of their crystallisation using 40Ar/39Ar analyses of whole-rock groundmass and plagioclase. However, as the igneous rocks are modified by varying degrees of alteration with the formation of secondary K- and Ca-bearing phases, none of the ∼75 Ma to ∼16 Ma 40Ar/39Ar dates record the age of their crystallisation. The plateau and weighted mean 40Ar/39Ar date populations define peaks at ∼75–60 Ma and ∼ 45–30 Ma that coincide with previously recognised tectonic events that drove fluid circulation, modifying the Ar isotopic compositions. Based on the maximum depositional ages of intercalated sedimentary rocks, the degree of deformation, geochemical and isotopic trends of the Jurassic arc in Ecuador, and correlations with the Early Cretaceous Quebradagrande Arc of Colombia, we propose that the Alao Arc formed during ∼140–110 Ma. • The Alao Arc formed on thinned continental crust in an extensional tectonic setting. • E -MORB-type basalts formed in an intra-arc rift within the Alao Arc. • Trace elements and Sr-Nd-Pb isotopes indicate crustal contamination. • 40Ar/39Ar dates were modified by later fluid alteration events at ∼75–60 and ∼ 45–30 Ma. • It is proposed that the Alao Arc formed during ∼140–110 Ma. [ABSTRACT FROM AUTHOR]

Porphyry systems supply most copper and significant gold to our economy. Recent studies indicate that they are frequently associated with high Sr/Y magmatic rocks, but the meaning of this association remains elusive. Understanding the association between high Sr/Y magmatic rocks and porphyry-type deposits is essential to develop genetic models that can be used for exploration purposes. Here we present results on a Pleistocene volcano of Ecuador that highlight the behaviour of copper in magmas with variable (but generally high) Sr/Y values. We provide indirect evidence for Cu partitioning into a fluid phase exsolved at depths of ~15 km from high Sr/Y (>70) andesitic magmas before sulphide saturation. This lends support to the hypothesis that large amounts of Cu- and S-bearing fluids can be accumulated into and released from a long-lived high Sr/Y deep andesitic reservoir to a shallower magmatic-hydrothermal system with the potential of generating large porphyry-type deposits.