@article{PAR00003253,
  title = {{T}he contribution of the young {C}retaceous {C}aribbean {O}ceanic {P}lateau to the genesis of late {C}retaceous arc magmatism in the {C}ordillera {O}ccidental of {E}cuador},
  author = {{A}llibon, {J}. and {M}onjoie, {P}. and {L}apierre, {H}. and {J}aillard, {E}tienne and {B}ussy, {F}. and {B}osch, {D}. and {S}enebier, {F}.},
  editor = {},
  language = {{ENG}},
  abstract = {{T}he eastern part of the {C}ordillera {O}ccidental of {E}cuador comprises thick buoyant oceanic plateaus associated with island-arc tholeiites and subduction-related calc-alkaline series, accreted to the {E}cuadorian {C}ontinental {M}argin from {L}ate {C}retaceous to {E}ocene times. {O}ne of these plateau sequences, the {G}uaranda {O}ceanic {P}lateau is considered as remnant of the {C}aribbean-{C}olombian {O}ceanic {P}rovince ({CCOP}) accreted to the {E}cuadorian {M}argin in the {M}aastrichtien. {S}amples studied in this paper were taken from four cross-sections through two arc-sequences in the northern part of the {C}ordillera {O}ccidental of {E}cuador, dated as ({R}io {C}ala) or ascribed to ({M}acuchi) the {L}ate {C}retaceous and one arc-like sequence in the {C}hogon-{C}olonche {C}ordillera ({L}as {O}rquideas). {T}hese three island-arcs can clearly be identified and rest conformably on the {CCOP}. {I}n all four localities, basalts with abundant large clinopyroxene phenocrysts can be found, mimicking a picritic or ankaramitic facies. {T}his mineralogical particularity, although not uncommon in island arc lavas, hints at a contribution of the {CCOP} in the genesis of these island arc rocks. {T}he complete petrological and geochemical study of these rocks reveals that some have a primitive island-arc nature ({M}g{O} values range from 6 to 11 wt.%). {S}tudied samples display marked {N}b, {T}a and {T}i negative anomalies relative to the adjacent elements in the spidergrams characteristic of subductionrelated magmatism. {T}hese rocks are {LREE}-enriched and their clinopyroxenes show a tholeiitic affinity ({F}e{O}1-{T}i{O}2 enrichment and {C}a{O} depletion from core to rim within a single crystal). {T}he four sampled cross-sections through the island-arc sequences display homogeneous initial {N}d, and {P}b isotope ratios that suggest a unique mantellic source for these rocks resulting from the mixing of three components: an {E}ast-{P}acific {MORB} end-member, an enriched pelagic sediment component, and a {HIMU} component carried by the {CCOP}. {I}ndeed, the ankaramite and {M}g-basalt sequences that form part of the {C}aribbean-{C}olombian {O}ceanic {P}lateau are radiogenically enriched in {P}b-206/{P}b-204 and {P}b-207/{P}b-204 and contain a {HIMU} component similar to that observed in the {G}orgona basalts and {G}alapagos lavas. {T}he subduction zone that generated the {L}ate {C}retaceous arcs occurred far from the continental margin, in an oceanic environment. {T}his implies that no terrigenous detrital sediments interacted with the source at this period. {T}hus, the enriched component can only result from the melting of subducted pelagic sediments. {W}e have thus defined the {E}ast-{P}acific {MORB}, enriched (cherts, pelagic sediments) and {HIMU} components in an attempt to constrain and model the genesis of the studied island-arc magmatism, using a compilation of carefully selected isotopic data from literature according to rock age and paleogeographic location at the time of arc edification. {T}ripolar mixing models reveal that proportions of 12-15 wt.% of the {HIMU} component, 7-15 wt.% of the pelagic sediment end-member and 70-75 wt.% of an {E}ast-pacific {MORB} end-member are needed to explain the measured isotope ratios. {T}hese surprisingly high proportions of the {HIMU}/{CCOP} component could be explained by the young age of the oceanic plateau (5-15 {M}a) during the {L}ate {C}retaceous arc emplacement. {T}he {CCOP}, basement of these arc sequences, was probably still hot and easily assimilated at the island-arc lava source.},
  keywords = {{E}cuador ; {C}retaceous island arcs ; {O}ceanic plateau ; {G}eochemistry ; {I}sotopes ; {M}odelling},
  booktitle = {},
  journal = {{J}ournal of {S}outh {A}merican {E}arth {S}ciences},
  volume = {26},
  numero = {4},
  pages = {355--368},
  ISSN = {0895-9811},
  year = {2008},
  DOI = {10.1016/j.jsames.2008.06.003},
  URL = {https://www.documentation.ird.fr/hor/{PAR}00003253},
}