Schlieren-Bound Magmatic Structures Record Crystal Flow-Sorting in Dynamic Upper-Crustal Magma-Mush Chambers

Abstract

Multi-Scale Magma Flow-Sorting formed from the amalgamation of intruding magma pulses, and precludes dike, sill, or laccolith emplacement models. We conclude that schlieren-bound structures are faithful recorders of the multi-scale, hypersolidus evolution of upper-crustal magma bodies, and represent useful tools for studying plutonic systems.

Coupled magmatic and host rock processes during the initiation of the Tuolumne Intrusive Complex, Sierra Nevada, California, USA: A transition from ephemeral sheets to long-lived, active magma mushes

“…In the Kuna Crest lobe, we have documented that early sheeting evolved within a few hundred thousand years, to larger, interacting crystal mush systems that represent active magma chambers. When U/Pb ages from our more extensive geochronologic study for the entire TIC are contoured (Memeti et al 2014;Paterson et al, 2016;Ardill et al, 2020b), broad regions (>hundreds of km 2 ) have similar ages and gradational internal contacts between distinct units, implying that it is quite permissible for these to represent magma chambers, a conclusion supported by thermal modeling (Yoshinobu et al, 1998;Paterson et al 2011;Karakas et al, 2017).…”

“…Tobisch et al (2000) concluded that in the Ritter Range area "downward flow" of the host rocks occurred in the plutonic aureoles during emplacement. Several authors (e.g., Bateman and Chappell, 1979;Paterson, 2005, 2010;Paterson et al 2016;Ardill et al, 2020b) present evidence of internal emplacement processes of one pulse into another and document evidence of erosion and recycling of older units into younger pulses and downward flow of magma.…”

“…A number of other studies have documented similar evidence for magma interaction across the TIC providing ample evidence of active mush systems. Petrologic relationships indicate mixing of compositionally distinct magmas and their mineral cargo at the whole rock and mineral scales as shown at the transition of the KC lobe to the TIC and other parts of the intrusion (Kistler et al, 1986;Wallace and Bergantz, 2002;Chambers et al, 2020;Oppenheim et al, 2021), internal magmatic erosion and recycling (Bate-man and Chappell, 1979;Paterson, 2005, 2010;Paterson et al, 2016), widespread formation of schlieren-defined magmatic structures and fabrics (Reid et al, 1993;Žák et al, 2007;Paterson, 2009;Ardill et al 2020b), and enclave formation and dispersal (Barbarin, 2005;Barnes et al 2021).…”

“…(C) Vertical dike complex or magmatically folded sill stack. A vertical sheeted dike model requires regional E-W extension (Bartley et al, 2018), which is incompatible with regional magmatic structures preserved consistently throughout the TIC (Žák et al, 2007;Ardill et al, 2020b) and Cretaceous dextral transpression host rock structures preserved across the entire Sierra Nevada batholith (see summary in Cao et al, 2015, 2016, andreferences therein). An E-W emplacement model also requires E-W striking shear zones at both N-and S-ends of the TIC and associated offset of stratigraphy and other host rock markers, none of which have been recognized at any scale of mapping (e.g., Huber et al, 1989;Memeti et al, 2014).The Coleman et al (2012) stacked-sill-model and subsequent E-W folding of the stack might be generally compatible with the regional transpressive regime.…”

Modeling water exsolution from a growing and solidifying felsic magma body

“…High proportion of water results in the fragmentation and fluidization of the rock even at low melt fraction (Fowler and Spera, 2008). We speculate that it might play a role in the formation of schlieren structures (Ardill et al, 2020). In case of chamber failure and eruption, the entrainment of those fragmented layers from the roof could explain the common presence of older crystals and the evidence for cold storage in volcanic product (Cooper and Kent, 2014;Rubin et al, 2017).…”