High‐pressure metamorphic evolution of eclogite and associated metapelite from the Chuacús complex (Guatemala Suture Zone): Constraints from phase equilibria modelling coupled with Lu‐Hf and U‐Pb geochronology

Abstract

As is common in suture zones, widespread high‐pressure rocks in the Caribbean region reached eclogite facies conditions close to ultrahigh‐pressure metamorphism. Besides eclogite lenses, abundant metapelitic rocks in the Chuacús complex (Guatemala Suture Zone) also preserve evidence for high‐pressure metamorphism. A comprehensive petrological and geochronological study was undertaken to constrain the tectonometamorphic evolution of eclogite and associated metapelite from this area in central Guatemala. The integration of field and petrological data allows the reconstruction of a previously unknown segment of the prograde P–T path and shows that these contrasting rock types share a common high‐pressure evolution. An early stage of high‐pressure/low‐temperature metamorphism at 18–20 kbar and 530–580°C is indicated by garnet core compositions as well as the nature and composition of mineral inclusions in garnet, including kyanite–jadeite–paragonite in an eclogite, and chloritoid–paragonite–rutile in a pelitic schist. Peak high‐pressure conditions are constrained at 23–25 kbar and 620–690°C by combining mineral assemblages, isopleth thermobarometry and Zr‐in‐rutile thermometry. A garnet/whole‐rock Lu‐Hf date of 101.8 ± 3.1 Ma in the kyanite‐bearing eclogite indicates the timing of final garnet growth at eclogite facies conditions, while a Lu‐Hf date of 95.5 ± 2.1 Ma in the pelitic schist reflects the average age of garnet growth spanning from an early eclogite facies evolution to a final amphibolite facies stage. Concordant U‐Pb LA‐ICP‐MS zircon data from the pelitic schist, in contrast, yield a mean age of 74.0 ± 0.5 Ma, which is equivalent to a U‐Pb monazite lower‐intercept age of 73.6 ± 2.0 Ma in the same sample, and comparable within errors with a less precise U‐Pb lower‐intercept age of 80 ± 13 Ma obtained in post‐eclogitic titanite from the kyanite‐bearing eclogite. These U‐Pb metamorphic ages are interpreted as dating an amphibolite facies overprint. Protolith U‐Pb zircon ages of 167.1 ± 4.2 Ma and 424.6 ± 5.0 Ma from two eclogite samples reveal that mafic precursors in the Chuacús complex originated in multiple tectonotemporal settings from the Silurian to Jurassic. The integration of petrological and geochronological data suggests that subduction of the continental margin of the North American plate (Chuacús complex) beneath the Greater Antilles arc occurred during an Albian‐Cenomanian pre‐collisional stage, and that a subsequent Campanian collisional stage is probably responsible of the amphibolite facies overprint and late syncollisional exhumation.

Integrating X‐ray mapping and microtomography of garnet with thermobarometry to define the P–T evolution of the (near) UHP Międzygórze eclogite, Sudetes, SW Poland

“…Depletion of grossular in the garnet rims is interpreted to be an effect of the zoisite‐in reaction along the retrograde part of the P–T path. A similar pattern has been observed in kyanite‐eclogites elsewhere, for example, in the Tromsdalstind eclogite of the Scandinavian Caledonides (Janák, Ravna, & Kullerud, ) and in the Chuacús complex of the Guatemala Suture Zone (Maldonaldo, Weber, Ortega‐Gutierréz, & Solari, ). This second generation of zoisite commonly overgrows omphacite and occurs in contact with the garnet rims.…”

Multi‐episodic formation of baddeleyite and zircon in polymetamorphic anorthosite and rutile‐bearing ilmenitite from the Chiapas Massif Complex, Mexico

“…While Cretaceous metamorphism has been reported for the eastern segment of the Polochic‐Motagua fault system, the data presented here are potentially the first record of this event in the western segment. The closest locality with a similar Cretaceous age is therefore ~200 km to the east along the Polochic Fault within the high‐pressure metamorphic Chuacús Complex of Guatemala (see Figure 1b; Maldonado, Weber, et al, 2018; Martens et al, 2012; Ratschbacher et al, 2009). The timing of eclogite facies metamorphism in the Chuacús Complex has been dated with the Lu‐Hf method on garnet and whole‐rock aliquots from eclogite at 101 ± 3 and 95 ± 2 Ma, whereas zircon, monazite and titanite U–Pb ages indicate later‐stage events at c. 80–74 Ma (Maldonado, Weber, et al, 2018).…”

“…The closest locality with a similar Cretaceous age is therefore ~200 km to the east along the Polochic Fault within the high‐pressure metamorphic Chuacús Complex of Guatemala (see Figure 1b; Maldonado, Weber, et al, 2018; Martens et al, 2012; Ratschbacher et al, 2009). The timing of eclogite facies metamorphism in the Chuacús Complex has been dated with the Lu‐Hf method on garnet and whole‐rock aliquots from eclogite at 101 ± 3 and 95 ± 2 Ma, whereas zircon, monazite and titanite U–Pb ages indicate later‐stage events at c. 80–74 Ma (Maldonado, Weber, et al, 2018). Zircon dating of meta‐granitoids associated with eclogites showed protolith ages of c. 1.1–1.0 Ga and c. 224 Ma (Maldonado, Ortega‐Gutiérrez et al, 2018; Solari et al, 2011).…”

“…Zircon dating of meta‐granitoids associated with eclogites showed protolith ages of c. 1.1–1.0 Ga and c. 224 Ma (Maldonado, Ortega‐Gutiérrez et al, 2018; Solari et al, 2011). Tectonic reconstructions for the Cretaceous period suggest proximity between the southern CMC and the Chuacús Complex during the evolution of the Caribbean region, as both comprised the southern portion of the Maya Block (Maldonado, Ortega‐Gutiérrez, et al, 2018; Maldonado, Weber, et al, 2018; Martens et al, 2017). We argue that our new geochronological evidence from rutile and zircon may reflect the timing of a high‐pressure and relatively low‐temperature tectonothermal disruption, which may be supported by the occurrence of phengitic mica in the anorthosites (Si [apfu] = 3.26 to 3.33; see Dataset S1).…”

Sedimentary Record of Arc‐Continent Collision Along Mesozoic SW North America (Siuna Belt, Nicaragua)

“…Onset of back‐arc closure could have initiated as early as the Barremian (Bandini et al, ), as suggested by the formation of the North Motagua Mélange (Harlow et al, ; Brueckner et al, ; Flores et al, ; Figures c and c). At the junction between the Arperos and proto‐Caribbean basins, back‐arc closure led to the subduction of the Maya Block (Bandini et al, ; Flores et al, ) thus forming the Chuacús Complex (approximately 100‐Ma metamorphic peak; Maldonado et al, ; Figures d and d). The restriction of metamorphic events to the southern part of the back‐arc suggests that the basin was significantly wider in its southern segment, possibly due to the proximity of the spreading proto‐Caribbean oceanic floor, thus allowing for further shortening to occur during subsequent back‐arc closure (Figures and ).…”