Magmatic Evolution of Azufre Volcano, Central Andes of Northern Chile.
Abstract
Azufre is a stratovolcano located within the Altiplano-Puna Volcanic Complex (APVC; 21-24S), in the Central Andean Volcanic Zone. This zone is characterized by a thick continental crust (>60 km, [1]), and the presence of a partially molten upper crustal layer, the Altiplano-Puna Magma Body [APMB; 2]. Whole rock major and trace element composition, Sr- and Nd- isotope ratios, and 18O values of quartz phenocrysts were measured in selected lavas from Azufre volcano. The silica content of the erupted lavas of this volcano range between andesite (~60 wt.%) and dacite (~67 wt.%) compositions. These lavas have 87Sr/86Sr ratios varying from 0.7066 to 0.7074, 143Nd/144Nd ratios between 0.51229 and 0.51239, and quartz 18O values ranging from 7.9 to 9.6 . The 87Sr/86Sr ratios show a negative correlation with 144Nd/143Nd ratios. Samples can be grouped on the basis of magma 18O values assuming that qz-melt fractionation value is -0.5 [e.g., 3, 4]) plotted against 87Sr/86Sr and 144Nd/143Nd ratios: i) a first group with an almost flat trend, with no significant change in 18O (7.5 7.8 ) with changing radiogenic isotope content; ii) a group of increasing 18O (8.4 - 9.2 ), with increasing 87Sr/86Sr and decreasing 144Nd/143Nd ratios of magmas, and iii) a group of decreasing 18O (8.2 7.3 ) with increasing Sr and decreasing Nd radiogenic compositions. Considering the isotopic content of sub-arc parental magmas within the APVC province (87Sr/86Sr ~0.7060; 144Nd/143Nd ~0.51245; 18O ~6.0; [5]) composition of analyzed lavas from Azufre volcano are higher. Thus, these preliminary results indicate that contamination is an important evolutionary magmatic process for this volcano. The different groups indicate variation in the composition of assimilated material and could be associated to mixing/assimilation of sub-arc magmas with highly Sr and O isotopic upper crust and low-18O hydrothermally altered material, as observed for other volcanoes of the APVC [e.g., 6]. [1] Beck et al., 1996. Geology, 24(5), 407-410. [2] Ward et al., 2014. Earth Planet Sc Lett, 404, 43-53 [3] Bindeman & Valley, 2003. Geol Soc Am Bull, 115(5), 581-595. [4] Budd et al., 2017. Sci Rep, 7(1), 1-11. [5] Gonzalez-Maurel et al., 2020. Sci Rep, 10(1), 1-10. [6] Feeley & Sharp, 1994. Earth Planet Sc Lett, 133(3-4), 239-254
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2021
- Bibcode:
- 2021AGUFM.V25C0115G