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| Coquimbo Complex | |
|---|---|
| Name | Coquimbo Complex |
| Type | Metamorphic and igneous terrane |
| Period | Neoproterozoic–Mesozoic (complex) |
| Primary lithology | Schist, gneiss, phyllite, amphibolite, granitoid |
| Other lithology | Migmatite, marble, metavolcanic rocks, metasediment |
| Named for | Coquimbo Region |
| Region | Coquimbo Region, Chile; adjacent regions |
| Country | Chile |
Coquimbo Complex The Coquimbo Complex is a composite metamorphic and igneous terrane exposed in the north-central Chilean Andes and Coastal Cordillera that records Proterozoic to Mesozoic tectonothermal events. The unit crops out across the Coquimbo Region and adjacent provinces, preserving high-grade metamorphism, multiple episodes of magmatism, and a diverse fossil and mineral record that has implications for regional plate reconstructions. Studies integrate field mapping, geochronology, geochemistry, and paleontological evidence used by institutions such as the Universidad de Chile, Servicio Nacional de Geología y Minería (SERNAGEOMIN), and international research groups.
The Coquimbo Complex comprises an assemblage of metamorphic rocks and intrusive bodies that forms a key part of the basement architecture of the northern Chilean margin. Early descriptions by Chilean geologists emphasized its metamorphic fabrics and igneous intrusions; subsequent work tied the complex to tectonic episodes recognized in the Andes, Atacama Fault Zone, and correlated basement outcrops in Argentina and Peru. The complex is significant for understanding accretionary processes linked to the breakup of Rodinia and the evolution of the Gondwana margin, as well as younger Andean orogenesis associated with the Nazca Plate subduction.
The complex is positioned within the Coastal Cordillera and western foothills of the Andes, bounded by Mesozoic and Cenozoic basins including the Punta de Choros Basin and the Elqui Basin. Tectonically it interfingers with Permian–Triassic sequences and is overlain in places by Jurassic and Cretaceous volcanic and sedimentary units correlated with the regional magmatic arc that affected the Andean Orogeny. Regional structures include high-angle faults linked to the Atacama Fault System and west-vergent thrusts comparable to structures in the Chilean Precordillera and the Eastern Cordillera of Argentina. Metamorphic and intrusive events in the complex are temporally associated with terrane accretion episodes documented in southwestern Gondwana reconstructions.
Lithological constituents are dominated by aluminous and mafic schists, gneisses, phyllites, amphibolites, and intercalated metasedimentary successions including quartzite and marble. The complex hosts variably migmatized paragneisses and orthogneisses intruded by granitoids and dioritic bodies. Key stratigraphic relationships show fault-bounded slices and tectonostratigraphic assemblages akin to terranes described in the Chilean Coastal Range and correlate with crystalline basements such as the Cura-Mallín and Elqui units. Metavolcanic horizons within the complex share affinities with island-arc sequences recognized elsewhere along the Pacific Ring of Fire.
Detrital zircon U–Pb ages, whole-rock isotopes, and SHRIMP analyses indicate a complex, polyphase age spectrum encompassing Neoproterozoic inheritance, widespread early Paleozoic metamorphism, and Mesoproterozoic-to-Mesozoic magmatic events. Radiometric constraints place key high-grade metamorphism and migmatization episodes in the late Paleozoic to early Mesozoic, contemporaneous with Permian–Triassic tectonothermal episodes recorded across South America. Intrusive granitoids yield U–Pb ages that tie magmatism to Jurassic–Cretaceous arc activity associated with Nazca–South America convergence and crustal growth processes akin to those documented in the Central Volcanic Zone.
Although predominantly metamorphic, the complex contains metasedimentary horizons with reworked fossiliferous detritus and rare low-grade fossiliferous lenses preserving fragments comparable to Neoproterozoic microfossils and early Paleozoic assemblages reported from coeval basins. Biostratigraphic indicators are sparse; however, fossil fragments used for provenance studies have been compared to assemblages from the Famatinian belt, the Puncoviscana Formation, and Permian faunas of the Karoo Basin. Paleontological material plays a supporting role in provenance reconstruction and correlation with terranes hosting documented trilobites, brachiopods, and microfossils in adjacent regions.
Provenance studies integrating detrital zircon populations, geochemical proxies, and sedimentary fabric analyses interpret the original depositional environments as alternating shallow marine shelf, deep marine turbiditic, and volcanic-arc settings prior to regional metamorphism. Depositional histories reflect phases of basin development, arc magmatism, and sediment influx during Gondwana assembly and later reworking during Andean compression. Metamorphic mineral assemblages indicate amphibolite- to greenschist-facies overprints and localized granulite-facies conditions during thermal peaks comparable to those described for collisional belts in southwestern Gondwana reconstructions.
The Coquimbo Complex hosts mineral occurrences and resources important to regional exploration including metamorphosed base-metal mineralization, skarn-associated deposits, and orogenic gold occurrences genetically linked to structural corridors such as the Atacama Fault. Granitoid bodies are potential sources for tin–tungsten–molybdenum mineralization analogous to porphyry systems in the El Teniente and Escondida districts, while metamorphic marbles and schists locally supply dimension stone and aggregate. Regional mapping by SERNAGEOMIN and academic surveys by Universidad de Concepción and international teams continue to refine resource models and exploration targets.
Category:Geology of Chile Category:Metamorphic complexes Category:Coquimbo Region