The link between metamorphism, volcanism and geotectonic setting during the evolution of the Andes

Abstract

Summary A low-grade, non-deformational, regional metamorphism ranging from burial to ocean-floor type characterizes the Andean range. Longitudinal variations exist, coinciding with changes in the chemistry of the volcanic suites involved, both trends being controlled by the geotectonic setting. The study of Cretaceous volcanic rocks in Colombia, Peru and Chile indicates that: (i) ocean-floor metamorphism (high- T gradients) correlates with tholeiitic volcanism in marginal basins where the continental crust was eliminated or extremely attenuated; (ii) burial metamorphism (low- to moderate- T gradients) correlates with calc-alkaline to shoshonitic volcanism in ensialic, aborted, marginal basins with moderate thinning of the continental crust. The metamorphism in the Andes, which is characterized by a counter-clockwise P-T-t path, started during the initial stages of basin formation and preceded the orogenic activity, contrary to the development in compressional geotectonic settings.

Geology, Geochronology, and Hf and Pb Isotope Data of the Raul-Condestable Iron Oxide-Copper-Gold Deposit, Central Coast of Peru

“…5). This is incompatible with the aborted back-arc setting proposed by previous authors (e.g., Cobbing and Pitcher, 1983;Atherton and Webb, 1989;Atherton and Aguirre, 1992;Aguirre et al, 1989;Cobbing, 1998). The concentrations of high field strength elements (Nb, Zr, Ti, Y) in pre-and postmineralization basaltic rocks (i.e., early leucogabbro and late Patap Gabbro and dolerite, respectively) could be interpreted to indicate that the basement of the volcanic arc is oceanic crust in this part of the Peruvian coast.…”

“…These facts have led to a debate on the tectonic setting of both the western Peruvian trough and the Peruvian Coastal batholith, with two main theories being proposed. , Aguirre et al (1989), Atherton and Webb (1989), Atherton and Aguirre (1992), and Cobbing (1998) favor an aborted back-arc setting. They explain the tholeiitic affinity of some of the rocks and the existence of the dense structure below the western Peruvian trough as evidence of mantle doming, coeval with crustal thinning, subsidence, and the western Peruvian trough volcanism.…”

The tectonic regime along the Andes: Present‐day and Mesozoic regimes

“…The initial volcanics were more tholeiitic, changing to a more calcalkaline character in the younger rocks. The source of the magmas became more depleted with time due to an increase in degree of partial melting, and their compositions were modified by subduction-related fluids and contamination with a progressively thinner and younger crust (Levi 1973;Aguirre et al 1989;Levi et al 1989). The extension and subsidence resulted in low-relief topography close to sea level, in contrast with the present-day convergent Andeantype volcanism at the same latitude.…”

Prehnite-pumpellyite facies metamorphism in the Cenozoic Abanico Formation, Andes of central Chile (33°50'S): chemical and scale controls on mineral assemblages, reaction progress and the equilibrium state

“…The Andean Cordillera presents a widespread development of secondary mineral assemblages representative of sub-greenschist facies which have been recognized as products of burial metamorphism since early studies (Levi, 1969(Levi, , 1970Aguirre et al, 1978Aguirre et al, , 1989Offler et al, 1980;Levi et al, 1989;Atherton and Aguirre, 1992). This is particularly the case in central Chilean Andes where numerous studies have addressed the lowgrade metamorphism affecting the ca.…”

“…12 km thick Meso-Cenozoic succession exposed there (Levi, 1969(Levi, , 1970Aguirre et al, 1978Aguirre et al, , 1989Levi et al, 1989;Belmar, 2000;Robinson et al, 2004). The early studies were primarily based on petrographic descriptions (Levi, 1969(Levi, , 1970Aguirre et al, 1978Aguirre et al, , 1989Levi et al, 1989), and the incorporation of studies based on mineral chemistry in the last decade has greatly enhance our knowledge and understanding of this process in this area (Aguirre et al, 2000;Belmar, 2000;Robinson et al, 2004;Fuentes, 2004). However, there is still a lack of chemical studies addressing in detail the individual lithostratigraphic formations comprising the Meso-Cenozoic succession, even though some have been carried out at a few localities (Aguirre et al, 2000;Belmar, 2000;Fuentes, 2004).…”