A Mesoproterozoic to Jurassic history of continental eclogites from the Guatemala Suture Zone–implications for a peri-Amazonian ancestry

Abstract

Cretaceous continental eclogites of the Chuacús Complex (Guatemala Suture Zone) contain an extensive record spanning more than 1.1 Ga. In this study, we combine U-Pb zircon geochronology, Sm-Nd and Lu-Hf isotope systematics, and geochemistry with field observations to determine the origin of eclogite protoliths. Mafic precursors are multiple comprising Ectasian to Middle Jurassic rocks originated in convergent, within-plate, and continental rift settings. Eclogites with estimated ca. 1.3 Ga protolith ages display chemical and isotopic features suggesting that mafic precursors formed in an extensional arc setting. These rocks are part of a complexly folded gneiss sequence (El Chol unit) that underwent pervasive perturbation of the zircon U-Pb system during a polymetamorphic evolution. One generation of OIB-like protoliths yield crystallization ages of 1.1–1.0 Ga, were derived from an enriched mantle source, and belong to a bimodal igneous assemblage (Cubulco unit) related to intraplate magmatism. An additional eclogite with OIB characteristics is part of a considerably younger bimodal suite (Agua Caliente unit) emplaced at ca. 228 Ma during a renewed pulse of within-plate activity. The youngest eclogite protoliths crystallized at ca. 168–162 Ma and represent E-MORB-type metabasites derived from a depleted mantle source and contaminated with variable amounts of crustal material. Hence, the geological record of the Chuacús eclogites includes evidence for: (1) extensional magmatism in a pre-Rodinian continental arc setting, (2) Stenian intraplate magmatism compatible with global large igneous province activity around Rodinia, (3) the initial breakup of western equatorial Pangea during the Late Triassic, and (4) the consequent Middle Jurassic rifting of Middle America terranes from the northwestern Gondwana margin. These data imply that the internal continental massif of the Guatemala Suture Zone may have evolved from a peri-Amazonian crust in the same way as other basement inliers of Mexico and the Northern Andes formerly adjoined within Pangea.