Magma addition and flux calculations of incrementally constructed magma chambers in continental margin arcs: Combined field, geochronologic, and thermal modeling studies

Abstract

Incrementally constructed magma systems have been recognized from studies of the resulting plutons for more than three decades. However, magma addition rates, fl uxes, growth durations, sizes of increments, and sizes and durations of the resulting magma chambers have been diffi cult to ascertain, emphasizing the need for a better understanding of how magmatic systems evolve. Our results from studies of plutons and arc sections in the North American Cordillera indicate that a large range exists in all of these values. Although arc sections and individual plutons clearly have dramatic temporal changes in volumetric magma additions, true volumetric fl ux calculations are particularly diffi cult to determine. Thus, although subduction beneath arcs may have active durations of hundreds of millions of years, volumetrically most magmatism is emplaced during magmatic fl are-ups of ~10-30 m.y. duration. Individual plutons and batholiths in these arcs can grow in <0.5 m.y. to 10 m.y. Pulse sizes moving through these magma plumbing systems vary from small dike-like to large diapir-like pulses, both of which may form from earlier amalgamation of poorly defi ned pulses. Our thermal modeling, using a range of incremental growth scenarios, concludes that focused incremental growth with greater than a certain volumetric fl ux results in magma chambers that are much larger than individual pulses but less than the size of the fi nal batholith, and with hypersolidus durations of hundreds of thousands to millions of years. The volumetric magma fl ux and the spatial distribution of volumetric addition rates of magma, rather than size or shape of individual pulses, are the dominant controlling factors on growth scenarios and chamber sizes and durations.

Estimates of Volume and Magma Input in Crustal Magmatic Systems from Zircon Geochronology: The Effect of Modeling Assumptions and System Variables

“…Field studies, petrography, petrology, geochemistry, and thermal modeling support this model and additionally provide evidences for the periodic transfer of magma to the shallower portions of magmatic systems (Hildreth, 1981;de Saint-Blanquat et al, 2001Coleman et al, 2004;Glazner et al, 2004;Annen et al, 2006;Connolly et al, 2009;Schaltegger et al, 2009;Bouilhol et al, 2011;Paterson et al, 2011;Schoene et al, 2012;Solano et al, 2012Solano et al, , 2014Havlin et al, 2013;Caricchi et al, 2014;Jagoutz, 2014). In periodically replenished magmatic reservoirs, the relative volume of magma and residual melt of various compositions change over hundreds of thousands to millions of years as a function of the average rate of magma injection, the thermal properties and chemistry of the wall rocks and the topology of the pertinent phase diagrams for magmas contained within the magmatic system (Spera and Bohrson, 2001;Annen et al, 2006;Glazner, 2007;Solano et al, 2012Solano et al, , 2014Melekhova et al, 2013;Caricchi et al, 2014;Nandedkar et al, 2014;Caricchi and Blundy, 2015a).…”

A Late Jurassic to Early Cretaceous record of orogenic wedge evolution in the Western Interior basin, USA and Canada

“…Jurassic plutons are present in the Western Coast Plutonic Complex, Sierra Nevada Batholith, and the Omineca Belt of interior British Columbia (Fig. 5) (Archibald et al, 1983;Hyndman, 1983;Armstrong, 1988;Ducea, 2001;Gaschnig et al, 2009;Gehrels et al, 2009;Paterson et al, 2011). Similar segments of the Cordillera were active in the Early Cretaceous.…”

The rise and fall of continental arcs: Interplays between magmatism, uplift, weathering, and climate

“…We motivate our model with the Cretaceous Sierra Nevada and Peninsular Ranges batholiths in California, USA (Fig. 4), which flared up most recently between ∼120 and ∼85 Mya (My ago) based on a compilation of U-Pb zircon ages in sediments and plutons (Ducea and Barton, 2007;Ducea et al, 2015;Paterson et al, , 2011 (Fig. 5A).…”