Timing of subduction and exhumation in a subduction channel: Evidence from slab melts from La Corea Mélange (eastern Cuba)

• Published in: Lithos Vol. 127; no. 1-2; pp. 86 - 100
• Main Authors: Blanco-Quintero, I.F., Rojas-Agramonte, Y., García-Casco, A., Kröner, A., Mertz, D.F., Lázaro, C., Blanco-Moreno, J., Renne, P.R.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.11.2011
• Subjects: Ar–Ar; La Corea mélange; SHRIMP zircon dating; Slow exhumation; Tonalite; Young lithosphere; ASW, Caribbean Sea, Greater Antilles, Cuba; SHRIMP zircon dating; Tonalite; Young lithosphere; La Corea mélange; Ar–Ar; Slow exhumation
• ISSN: 0024-4937; 1872-6143
• DOI: 10.1016/j.lithos.2011.08.009

High pressure igneous rocks (tonalites), generated by partial melting of subducted basaltic rocks accreted to the mantle wedge, are present in the La Corea serpentinite-matrix mélange (eastern Cuba) as centimeter- to meter-sized blocks and as concordant to crosscutting veins within high-pressure parent amphibolite blocks. The slab melts have adakitic signatures, in agreement with formation after partial melting of metabasite. Thermobarometric calculations indicate 620–680°C and 13–15kbar during crystallization of tonalites and down to 250–300°C, 6kbar during retrogression, indicating counter-clockwise P–T paths (hot subduction-cool exhumation). Free water required for melting of amphibolite at moderate temperature (700–750°C) and moderate pressure (13–16kbar) close to the wet basaltic solidus is inferred to have been provided after dehydration of sediments, altered basaltic crust and serpentinite of the subducting Proto-Caribbean lithosphere. Single zircon (SHRIMP) and phengite 40Ar/39Ar age data constrain the P–T–t evolution of the mélange from the timing of crystallization of melts at ~110–105Ma to cooling at ~87–84Ma, ca. 350°C, ca. 9kbar. These figures are consistent with subduction of an oblique ridge, shortly before 115Ma. Furthermore, our data indicate very slow exhumation (ca. 1mm/yr) in the subduction channel during the oceanic convergence stage (120–70Ma) until final fast exhumation to the surface occurred at 70–65Ma during a regional arc-platform collision event. ► We study tonalite rocks formed by partial melting of the slab. ► Thermobarometric calculations indicate counter-clockwise P–T paths. ► Zircon (SHRIMP) data give the timing of crystallization of melts at ~110–105Ma. ► Phengite 40Ar/39Ar ages provide the cooling at ~87–84Ma. ► These data indicate very slow syn-subduction/exhumation (1mm/a).