Volcanic–plutonic links, plutons as magma chambers and crust–mantle interaction: a lithospheric scale view of magma systems

Abstract

The northern Colorado River extensional corridor (NCREC, USA) provides an excellent record of coeval volcanic and mid-to upper-crustal (<13 km) plutonic suites. The NCREC is a 50-100-km-wide zone that records late Tertiary lithospheric extension, volcanism, continental sedimentation and plutonism. Compilation of published studies of NCREC magmatic rocks permits an assessment of volcanic-plutonic links, magma sources and magmatic processes. The volcanic sections provide an excellent record of magma compositions (basalt, trachyandesite, trachyte and rhyolite) which span a 9-million-year period in the Miocene age (20-11 Ma).Contemporaneous Miocene plutons span a similar compositional range (gabbro, diorite, quartz monzonite and granite) and were emplaced during a 4·5-million-year interval from 17 to 12·5 Ma. Geochemical and isotopic compositions and compositional trends allow direct correlation between plutonic and volcanic suites across the entire compositional range. Petrogenetic models demonstrate that intermediate magmas formed by a combination of magma mixing and fractional crystallisation involving mantle-derived mafic with crustal-derived felsic end-member magmas. Plutons exhibit a variety of features which suggest magma chamber processes, including (1) mafic cumulate sequences, (2) felsic cumulate sequences, and (3) magma mingling and advanced stages of magma mixing. Thus, the NCREC plutonic-volcanic record provides a link between magmatic processes recorded in pluton magma chambers and magmatic products in the form of extrusive igneous rocks. The NCREC plutons represent upper crustal magma chambers which connected volcanic eruptive centres to deeper-level magma chambers, and ultimately, to zones of mantle and crustal melting.

Evidence for Cyclical Fractional Crystallization, Recharge, and Assimilation in Basalts of the Kimama Drill Core, Central Snake River Plain, Idaho: 5.5-Million-Years of Petrogenesis in a Mid-crustal Sill Complex

“…The petrologic and chemical evolution of volcanic provinces and the formation of continental crustal plutonic complexes are typically studied in isolation from one another, yet each of these topics has implications for the other related to magmatic flux, intrusion geometries, fractionation mechanisms, and the effects of partial melting and assimilation (Annen et al, 2015). Previous efforts to understand linkages between pluton construction and eruptive processes have focused largely on silicic systems: the assembly of granitic batholiths and rhyolite ignimbrite eruptions (e.g., Lipman, 1984;Metcalf, 2004;Annen et al, 2006). Although large mafic layered intrusions have been studied extensively (e.g., Irvine, 1970) and the effect of basalt intrusions on crustal heat flux has been modeled (Annen and Sparks, 2002), there are few studies that infer mafic plutonic evolution from basalt compositions in long-lived mafic volcanic provinces (e.g., Shervais et al, 2006).…”

Ignimbrites to batholiths: Integrating perspectives from geological, geophysical, and geochronological data

“…Building on twentieth-century discussions (such as Daly, 1914;Kennedy and Anderson, 1938;Buddington, 1959;Smith, 1979;Lipman, 1984;Macdonald and Smith, 1988), these results have promoted renewed controversy concerning connections between volcanic and intrusive processes, especially how magma reservoirs for large ignimbrite eruptions are related to the emplacement of granitic plutons and the crustal depths at which silicic compositions are generated Metcalf, 2005;Bachmann et al, 2007b;Lipman, 2007;Miller et al, 2011;Davis et al, 2012;de Silva and Gregg, 2014;Frazer et al, 2014;among others). For example, geochronologic data and chemical patterns of volcanic and shallow plutonic rocks have been interpreted by some as indicating melt generation in the deep crust with minimal differentiation at shallow crustal levels, leading to pluton assembly in small increments that crystallized rapidly, with temporal and geometric disconnects between ignimbrite eruption and intrusion growth Bartley et al, 2005;Annen, 2009;Coleman et al, 2012;Zimmerer and McIntosh, 2012a;Mills and Coleman, 2013).…”

Genesis and health risk implications of an unusual occurrence of fibrous NaFe3+-amphibole

“…structure consists of a sequence of pre-and syn-extensional mafic to silicic volcanic rocks intercalated with continental sediments. Coeval with the volcanic sequence is a suite of plutons (17-12 Ma) that are predominantly quartz monzonite, but include some more mafic rocks, and are commonly cut by aphanitic dikes (Larsen and Smith, 1990;Metcalf, 2004). All these rocks have been severely tilted by the extensional faulting.…”

“…In contrast, Miocene NCREC plutonic complexes, including Wilson Ridge, evolved by fractional crystallization of lithospheric mantle-derived alkali basalt combined with open-system mixing of large volumes of crustal-derived subalkaline felsic magma (Larsen and Smith, 1990;Metcalf, 2004). Miocene NCREC plutonic suites are metaluminous in composition (Fig.…”