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WITHDRAWN -Barometers Behaving Badlier: How well does resolve transcrustal magma systems?

Adam Kent 1, Penny Wieser2, Christy Till3, Geoff Abers4, Guanning Pang4

  • Affiliations: 1Oregon State University; 2University of California at Berkeley; 3Arizona State University; 4Cornell University

  • Presentation type: Poster

  • Presentation time: Friday 16:30 - 18:00, Room Poster Hall

  • Poster Board Number: 10

  • Programme No: 1.5.17

  • Theme 1 > Session 5

Abstract

Volcanoes are underlain by magma transport and storage systems of transcrustal extent, and the nature of these systems strongly influence key parameters such as eruption rates, styles, and volumes, and erupted compositions. Petrological methods are widely used to infer the nature of crustal magma systems, but techniques that estimate pressure -- essential for establishing the geometry of magmatic systems -- are limited by uncertainties, and by methodological and sampling biases. Recent work shows that the uncertainties associated with common barometry techniques (± 1 standard error) are relatively large: 5-8 km for mineral and mineral-liquid equilibria, and ~20% for fluid and melt inclusions. We have developed a probabilistic forward modelling approach to study the efficacy of petrological techniques for resolving the geometry of crustal magma systems. To do this we generate a synthetic mineral population based on a defined magma system geometry, and estimated probabilities for mineral formation, survival, and sampling. The synthetic population is then bootstrap resampled to simulate natural data sets, and results are dispersed to reflect uncertainties. Results show that while the larger scale features of crustal magmatic systems can generally be resolved, finer structure -- including that needed to test conceptual models -- are not resolvable. Small data sets (n < 50) also mean that reproducibility is poor, and may produce false positives and continuous PT "pseudoarrays" from discrete magma storage regions. The latter closely resemble arrays in the literature which are commonly interpreted to represent broadly continuous or transcrustal distributions of magma within the crust.