Constraints on the Origin and Evolution of Magmas in the Payún Matrú Volcanic Field, Quaternary Andean Back-arc of Western Argentina

Abstract

The Payu¤ n Matru¤ Volcanic Field (Pleistocene^Holocene) is located in the Andean back-arc of the Southern Volcanic Zone, western Argentina, and is contemporaneous with the Andean volcanic arc at the same latitude. It includes two polygenetic, mostly trachytic volcanoes: Payu¤ n Matru¤ (with a summit caldera 8 km wide) and Payu¤ n Liso (a smaller stratovolcano). The volcanic field includes about 200 scoria cones and alkali basaltic and trachybasaltic lava flows, forming two basaltic fields around Payu¤ n Matru¤. New 40 Ar^3 9 Ar ages extend the activity of Payu¤ n Matru¤ up to 700 ka. The major and trace element and Sr^Nd isotopic compositions of the basaltic lavas and Payu¤ n Matru¤ rocks indicate that the trachytes of Payu¤ n Matru¤ are the result of fractional crystallization of basaltic parent magmas without significant upper crustal contamination, and that the basalts have a geochemical similarity to ocean island basalt (La/Nb ¼ 0•8^1•5, La/Ba ¼ 0•05^0•08). The Sr^Nd isotopic compositions of the basaltic to trachytic rocks range between 0•703813 and 0•703841 (87 Sr/ 86 Sr) and 0•512743 and 0•512834 (143 Nd/ 144 Nd). Mass-balance and Rayleigh fractionation models support the proposed origin of the trachytes, and an assimilation^fractional crystallization model indicates a low degree of upper crustal contamination in the youngest trachytes. Magnesium numbers (45^55) and contents of Ni (5 20^90 ppm) and Cr (30^180 ppm) in the lavas in the basaltic fields indicate that these are not primary magmas. The data also suggest that the basaltic lavas originated in the asthenospheric mantle, probably within the spinel stability field and beneath an attenuated continental lithosphere in the back-arc area. The lack of a slab-fluid signature in the Payu¤ n Matru¤ Volcanic Field rocks, along with unpublished and published geophysical results (mantle tomography and electrical conductivity anomalies) suggest that magmas were generated by decompression-induced melting of upwelling mantle.

The Volcanic Evolution of Cerro Uturuncu: A High-K, Composite Volcano in the Back-Arc of the Central Andes of SW Bolivia

“…These granites are petrographically similar to the xenolith observed in this study. We contaminate two primitive basalt compositions with lower and upper crustal contaminants: one from Davidson and de Silva [13] for basalts from the central Altiplano, and a second from Hernando et al [42] for pre-caldera basalts from the Payún Matrú volcanic field in western Argentina's Southern Volcanic Zone. Table 3 presents concentrations and isotopic ratios of the contaminants and basalts.…”

Late Cretaceous lithospheric extension in SE China: Constraints from volcanic rocks in Hainan Island

“…In this regard, the required metasomatic agent would have higher Th, LREE and Hf contents than that proposed by experimental fluid/rock partition studies (e.g., Davidson et al, 2013;Johnson, 1998;Nelson and Davidson, 1993;Salters and Longhi, 1999). Numerous studies have shown that many geochemical features of arc-related rocks, such as enrichment in Hf isotopic composition or the depletion in Nb and Ta, can be attributed to slab-derived melts (e.g., Hernando et al, 2014;Pearce and Stern, 2006;Shao et al, 2014). In combination with geochemical and petrological features of the Liuluocun volcanic rocks, especially they show different characteristics of trace elements (Fig.…”

Stress Controls of Monogenetic Volcanism: A Review

“…This is clearly indicated by the petrology and geochemistry of magmas from monogenetic eruptions, which evidence certain degree of differentiation in most cases and occasional assimilation of crustal rocks that occurred at different depths (Thirlwall et al, 2000;Klügel et al, 2005;Stroncik et al, 2009;Valentine and Hirano, 2010;Brenna et al, 2011;Rowe et al, 2011;Hernando et al, 2014;Albert et al, 2015Albert et al, , 2016Klugel et al, 2015). These intermediate reservoir zones, which will normally be located at rheological or structural discontinuities inside the lithosphere, do not need to be stable or permanent along the whole history of the volcanic field.…”