@article{fdi:010077439,
  title = {{U}p to 1% {P}b isotope disequilibrium between minerals hosted in dacites from the {G}uagua {P}ichincha volcano, {E}cuador : implication for tracing the source and crustal history of continental arc magmas},
  author = {{A}ncellin, {M}. {A}. and {V}lastelic, {I}. and {S}amaniego, {P}ablo and {N}auret, {F}. and {G}announ, {A}. and {H}idalgo, {S}.},
  editor = {},
  language = {{ENG}},
  abstract = {{C}ontinental arc lavas display geochemical signatures that reflect both mantle metasomatism by slab fluids or melts and extensive differentiation of magmas within crustal reservoirs. {T}he relative effect of source and crustal processes are difficult to disentangle based on whole-rock compositions. {T}his issue is critical in {E}cuador where volcanism occurs through a thick continental crust (> 50 km). {T}his study reconstructs the history of melts feeding the {G}uagua {P}ichincha volcano, {W}estern {C}ordillera, by analysing the {P}b isotope composition and major-trace element content of individual minerals (33 amphiboles, 4 orthopyroxenes and 18 plagioclases) hosted in two dacite samples. {I}t uses a low-blank wet-chemistry method for precise analysis of {P}b amounts as low as 150 pg. {E}arly crystallized, high-{A}l amphiboles with {A}l2{O}3 >= 9.8 wt% and {E}u/{E}u* > 0.7 have the lowest and most heterogeneous {P}b-206/{P}b-204 (18.816-18.999), whereas plagioclases have the highest and most homogeneous {P}b-206/{P}b-204 (19.003-19.023). {L}ow-{A}l amphiboles and orthopyroxenes display intermediate compositions and variability (18.934-19.007). {T}he {P}b-206/{P}b-204 ratio correlates negatively with {E}u/{E}u* in amphiboles and orthopyroxenes, which indicates that the {G}uagua {P}ichincha magmas assimilate radiogenic {P}b within the stability field of plagioclase (i.e. in the upper crust). {T}he radiogenic ankaramites of the {G}uaranda unit, an accreted ocean terrain making the basement of the {W}estern {C}ordillera, are the most suitable contaminant. {I}f this is correct, the {P}b-206/{P}b-204 increase from the two most primitive amphiboles to their respective host rocks requires ca. 20% crustal assimilation, which is higher than previous estimates in the {N}orthern {V}olcanic {Z}one but similar to those inferred for {C}entral {A}ndean mafic lavas. {T}he two most primitive amphiboles with no significant {E}u anomaly record the composition of melts before plagioclase crystallization. {T}hese deep melts have contrasted {P}b-206/{P}b-204 ratios (18.816-18.879) and contents of fluid mobile elements ({L}i, {C}u, {R}b, {P}b) that probably reflect the input of different slab components to the mantle wedge. {M}elts in equilibrium with the two most primitive amphiboles of the {G}uagua {P}ichincha volcano are enriched in incompatible elements, but depleted in fluid mobile elements compared to the olivine-hosted melt inclusions of the older {R}ucu {P}ichincha volcano. {T}his supports previous inferences based on whole-rock data that the mantle source of the {P}ichincha {V}olcanic {C}omplex has changed through time.},
  keywords = {{S}ingle mineral {P}b isotopes ; {C}rustal evolution of magmas ; {P}rimitive melt ; {E}cuador ; {P}ichincha volcano ; {EQUATEUR} ; {GUAGUA} {PICHINCHA} {VOLCAN}},
  booktitle = {},
  journal = {{C}hemical {G}eology},
  volume = {525},
  numero = {},
  pages = {177--189},
  ISSN = {0009-2541},
  year = {2019},
  DOI = {10.1016/j.chemgeo.2019.07.016},
  URL = {https://www.documentation.ird.fr/hor/fdi:010077439},
}