@article{fdi:010060705,
  title = {{M}etamorphic and geochronogical study of the {T}riassic {E}l {O}ro metamorphic complex, {E}cuador : implications for high-temperature metamorphism in a forearc zone},
  author = {{R}iel, {N}. and {G}uillot, {S}. and {J}aillard, {E}tienne and {M}artelat, {J}. {E}. and {P}aquette, {J}. {L}. and {S}chwartz, {S}. and {G}oncalves, {P}. and {D}uclaux, {G}. and {T}hebaud, {N}. and {L}anari, {P}. and {J}anots, {E}. and {Y}uquilema, {J}.},
  editor = {},
  language = {{ENG}},
  abstract = {{I}n the forearc of the {A}ndean active margin in southwest {E}cuador, the {E}l {O}ro metamorphic complex exhibits a well exposed tilted forearc section partially migmatized. {W}e used {R}aman spectroscopy on carbonaceous matter ({RSCM}) thermometry and pseudosections coupled with mineralogical and textural studies to constrain the pressure-temperature ({P}-{T}) evolution of the {E}l {O}ro metamorphic complex during {T}riassic times. {O}ur results show that anatexis of the continental crust occurred by white-mica and biotite dehydration melting along a 10 km thick crustal domain (from 4.5 to 8 kbar) with increasing temperature from 650 to 700 degrees {C}. {I}n the biotite dehydration melting zone, temperature was buffered at 750-820 degrees {C} in a 5 km thick layer. {T}he estimated average thermal gradient during peak metamorphism is of 30 degrees {C}/km within the migmatitic domain can be partitioned into two apparent gradients parts. {T}he upper part from surface to 7 km depth records a 40-45 degrees {C}/km gradient. {T}he lower part records a quasi-adiabatic geotherm with a 10 degrees {C}/km gradient consistent with an isothermal melting zone. {M}igmatites {U}-{T}h-{P}b geochronology yielded zircon and monazite ages of 229.3 +/- 2.1 {M}a and 224.5 +/- 2.3 {M}a, respectively. {T}his thermal event generated {S}-type magmatism (the {M}arcabeli granitoid) and was immediately followed by underplating of the high-pressure low-temperature ({HP}-{LT}) {A}renillas-{P}anupali unit at 225.8 +/- 1.8 {M}a. {T}he association of high-temperature low-pressure ({HT}-{LP}) migmatites with {HP}-{LT} unit constitutes a new example of a paired metamorphic belt along the {S}outh {A}merican margin. {W}e propose that in addition to crustal thinning, underplating of the {P}iedras gabbroic unit before 230 {M}a provided the heat source necessary to foster crustal anatexis. {F}urthermore, its {MORB} signature shows that the asthenosphere was involved as the source of the heat anomaly. {S}-type felsic magmatism is widespread during this time and suggests that a large-scale thermal anomaly affected a large part of the {S}outh {A}merican margin during the late {T}riassic. {W}e propose that crustal anatexis is related to an anomaly that arose during subduction of the {P}anthalassa ocean under the {S}outh {A}merican margin. {S}lab verticalization or slab break-off can be invoked as the origin of the upwelling of the asthenosphere.},
  keywords = {{M}igmatites ; {U}/{P}b geochronology ; {H}igh-temperature low-pressure metamorphism ; {P}seudosections ; {P}aired-metamorphic belt ; {E}cuador ; {EQUATEUR}},
  booktitle = {},
  journal = {{L}ithos},
  volume = {156},
  numero = {},
  pages = {41--68},
  ISSN = {0024-4937},
  year = {2013},
  DOI = {10.1016/j.lithos.2012.10.005},
  URL = {https://www.documentation.ird.fr/hor/fdi:010060705},
}