Contrasting magmatic structures between small plutons and batholiths emplaced at shallow crustal level (Sierras de Córdoba, Argentina)

Incremental growth of an upper crustal, A-type pluton, Argentina: Evidence of a re-used magma pathway

“…The concentric fabrics in SBU and HU together with flattened type 4 (also measured in the felsic enclaves), indicate that these composite fabrics formed by superposition of two different strain increments (e.g., Paterson et al, 2003;Žák et al, 2007;Pinotti et al, 2016). …”

“…Magmatic foliations of both units locally change into sub parallelism near the contact. Additionally, relatively straight and subparallel schlieren and schlieren troughs (i.e., Paterson, 2009;Pinotti et al, 2016) occur in the SBU close to the contact. Aplite and pegmatite dikes are common in the SBU, which in places cut across the contact extending only a few meters into the AU.…”

Magmatically folded and faulted schlieren zones formed by magma avalanching in the Sonora Pass Intrusive Suite, Sierra Nevada, California

“…We envisage that most of the causes described for the development of large-scale (10 2 -10 3 -m-wide) magma avalanches in peripheral mush zones occur in large, long-lived magma-mush chambers that mechanically mingle and mix, rather than small, isolated magma bodies (e.g., Solgadi and Sawyer, 2008;Pinotti et al, 2016). A long-lived, thermally mature magmatic plumbing system allows potentially multiple magma chambers to form at shallow crustal levels (e.g., Alasino et al, 2017).…”

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

“…Schlieren are commonly found in planar form (e.g., Bateman, 1992;Žák and Klomínský, 2007;Burgess and Miller, 2008;Pinotti et al, 2016), but also delineate curved boundaries of structures such as: channel-shaped magmatic troughs (e.g., Wahrhaftig, 1979;Barrière, 1981;Solgadi and Sawyer, 2008;Žák and Paterson, 2010;Alasino et al, 2019; see also Wager and Brown, 1968;Vukmanovic et al, 2018 for mafic systems), stationary and migrating tubes, also called ladder dikes (e.g., Reid et al, 1993;Weinberg et al, 2001;Wiebe et al, 2007;Dietl et al, 2010;Clarke et al, 2013), meter-scale diapirs and plume heads (e.g., Weinberg et al, 2001;Paterson, 2009), and mafic ellipsoids (e.g., Memeti et al, 2014). In general, studies of schlieren-bound magmatic structures aim to address two related questions: (1) under what magmatic conditions and by which process(es) do schlieren form ( Figure 1A) and (2) how do these processes influence, or contribute to, the variety of schlieren-bound structures of different geometries and characteristics ( Figure 1B)?…”

“…Several processes may have operated in the TIC. The intrusion of new pulses, or upwards migration of volatiles, could lead to mobilization and convection of the mush (e.g., Bachmann and Bergantz, 2006;Burgisser and Bergantz, 2011;Pinotti et al, 2016; Figure 12A). In computational models, the heterogeneous distribution of particle force chains maps transient high and low stress zones in the mush, that has implications for pore-pressure variability, and overall mush porosity (e.g., Estep and Dufek, 2012;Bergantz et al, 2017).…”