Provenance, age constraints and metamorphism of Ediacaran metasedimentary rocks from the El Triunfo Complex (SE Chiapas, México): evidence for Rodinia breakup and Iapetus active margin

Metasedimentary rocks from the El Triunfo Complex (Jocote Unit) in the southern Chiapas Massif (SE México) are constituted mainly by sillimanite-rich micaschist, locally intercalated with marble and calc-silicate rocks. Mafic rocks (now amphibolite) intruded the sequence prior to deformation and folding. Peak metamorphic conditions are estimated by geothermobaromerty at ~6.0 kbar and ~650ºC. The timing of the metamorphic event is dated by LA-MC-ICPMS analysis on zircon rims at 438⁺²³/_–12 Ma. Furthermore, detrital zircon grains yield mainly Stenian–Tonian and minor early Mesoproterozoic ages, indicating provenance from Grenville-type orogens (such as Oaxaquia) and some older cratonic sources. The ⁸⁷Sr/⁸⁶Sr values of 0.70775–0.70777 and the δ¹³C values from +1.9‰ to +2.7‰ in associated calcite marble define the time of deposition between 600 and 580 Ma. Geochemical markers from metapelite samples (such as La/Th &gt; 3.94, La/Sc &gt; 3.72, Th/U &gt; 8.19, Th/Co &gt; 0.42 and CIA = 74 to 83), as well as Sm–Nd isotope data (<i>ε</i>Nd_<i>i</i> = −8.1 to −4.0, TDM_(Nd) = 1.65–1.32 Ga) suggest weathering of Mesoproterozoic felsic rocks during temperate to warm climate. Furthermore, Zr/Sc values (9.1–21.0), chondrite-normalized REE patterns [La/Yb]_<i>N</i> = 10.3–23.3, Eu/Eu*