21 Frontiers in Geochronology: Advances and Applications in the Geosciences
This session highlights cutting-edge geochronologic advances and applications that illuminate Earth’s dynamic history. We welcome contributions spanning new analytical techniques, integrative studies, and innovative case examples demonstrating the essential role of time in geosciences.
Tuesday, 10 March 2026
10:00 AM - 12:00 PM
RCC, 104
Prolonged Magma Storage Conditions at Lastarria Volcanic Area, Andean Central Volcanic Zone, Chile
Paper number: 21-2
Program: Technical Sessions
Time: 10:30 AM – 10:45 AM
Authors
Abstract
Understanding the thermal evolution of large-volume magma reservoirs determines their size and their ability to sustain shallower volcanic systems. While the spatial distribution and homogeneity of volcanoes associated with large-volume reservoirs reveal information on eruption dynamics, quantitative analysis of mineral crystallization ages, such as zircon, provides insight into the timing and magnitude of thermal and chemical variation throughout a reservoir's lifespan. The Lazufre Volcanic Area in north-central Chile is characterized by a large-scale ellipsoidal surface deformation pattern associated with magma migration into the mid-crust and several Holocene volcanic complexes. Lastarria is the northernmost composite volcano in the Lazufre Volcanic Area, with as many as 10 stages of volcanic activity from 400 ka to the present. This study presents high-precision U-Th and U-Pb zircon crystallization ages, δ18O values, and trace-element geochemistry for a suite of samples from the Lastarria composite cone and one sample from a young lava flow to the south of Lastarria. These data are combined with whole-rock trace-element geochemistry and Sr, Nd, and Pb isotope ratios. Whole-rock Sr isotope ratios decrease over time, ranging from 0.707232 at 388 ka to 0.706211 by 42 ka. Zircon δ18O values fall into two groups that correlate with age. The younger group ranges from 5.4-6.07‰ (n=12), and the older group from 6.37-6.84‰ (n=9). This dataset documents the protracted growth and evolution of a voluminous, mid-crustal silicic magma reservoir. Zircon ages and trace-element compositions reveal that new magma intruded episodically into a progressively more homogeneous magma reservoir over time.
Geological Society of America Abstracts with Programs. Vol. 58, No. 1
doi: 10.1130/abs/2026SE-411738
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