Spatiotemporally heterogeneous deformation, indirect tectonomagmatic links, and lithospheric evolution during orogenic activity coeval with an arc flare-up

Abstract

Broad overlap between deformation and magmatism in active margins has spurred the development of a conceptual framework of direct tectonomagmatic links in both active and ancient arcs. Although widespread and highly influential, such models have only rarely been critically evaluated. Rigorously linking tectonism, geodynamics, lithospheric evolution, and arc activity requires detailed reconstructions of the spatiotemporal patterns of magmatism and deformation across both a sufficiently wide area and a range of observational scales. Herein, new constraints on the timing, extent, and characteristics of deformation during mid-Cretaceous tectonism in the central Sierra Nevada (eastern California, USA) are synthesized with published geologic mapping, structural studies, and geochronology to create an updated reconstruction of one of the type examples of a hot, magma-rich orogen. Tilted strata, tectonic fabrics, and shear zones with variable geometries, kinematics, intensity, and timing reveal a significantly revised record of ~25 m.y. of heterogeneous deformation ca. 105–80 Ma. Deformation and magmatism show distinct and unrelated spatiotemporal patterns throughout this orogenic episode. Contrary to previous models of direct tectonomagmatic links, many of which were developed in the central Sierra Nevada, arc activity did not control the location, intensity, or kinematics of intra-arc deformation, nor did shear zones control the location of magmatism. Furthermore, arc lithosphere appears to have strengthened, rather than weakened, as the arc-orogenic flare-up proceeded. In addition to changing plate-scale boundary conditions, lithospheric-scale rheological evolution likely played a key role in the patterns of Late Cretaceous deformation observed across strike of the entire Cordilleran margin.

A Complex Interplay Between Pluton Emplacement, Tectonic Deformation, and Plate Kinematics in the Cretaceous Sierra Nevada Magmatic Arc, California

“…In an attempt to resolve the above issue, we compiled field structural, AMS, and geochronological data from plutons of the central Sierra Nevada (Table S6 in Supporting Information S2). The compilation only includes those plutons, the structural record of which was interpreted by the authors as reflecting regional tectonic strains (see also Attia et al., 2022). The structural and geochronology data shows that a mean orientation of magmatic and magnetic foliations in the ∼107–86 Ma plutons does not reveal a systematic rotation trend in time that would fit a potential switch in the transpressional kinematic regime (Figure 12b).…”

“…The studied area of the eastern portion of the TIC includes a pluton/host rock contact that is parallel to the synemplacement Cascade Lake Shear Zone, a ductile dextral shear zone that in places heterogeneously affects a few tens to hundreds meters of the TIC granodiorites and the adjacent host rock (Attia et al, 2022;Greene & Schweickert, 1995;Hartman et al, 2018;Tikoff & Greene, 1997;Tikoff et al, 2005). Tikoff et al (2005) sampled a transect in the Cathedral Peak granodiorite across this shear zone in the Steelhead Lake area.…”

“…However, the new AMS data from the shear zone has no impact on our general tectonic interpretations as only the fabric parameters from the Tioga Pass area were used for fabric modeling. In addition, two stations in the Kuna Crest granodiorite from the Tioga Pass area near the Granite lakes (JZ1060 and JZ1054) were also sampled in an area affected by the Cascade Lake Shear Zone (see also Attia et al., 2022; Hartman et al., 2018). These AMS data have an insignificant impact on the group statistics of the Kuna Crest used in the fabric modeling (see below).…”

“…The models for its emplacement and magmatic evolution are hotly debated and vary considerably, essentially between short‐lived chamber(s) assembled via dikes/sills and long‐lived chamber(s) assembled via multiple large magma batches (Bartley et al., 2008, 2018; Chambers et al., 2020; Coleman et al., 2004, 2012; Glazner et al., 2004; Memeti et al., 2010; Paterson & Vernon, 1995; Paterson et al., 2016; Žák & Paterson, 2005; Žák et al., 2009). Yet, the significance of its synmagmatic deformation is not fully understood, especially in its relation to past plate motions (Ardill, Paterson, et al., 2020; Attia et al., 2022; Burton‐Johnson et al., 2022; Cao et al., 2015).…”

“…For instance, the Mesozoic Sierra Nevada magmatic arc in California, one of the typical examples of Cordilleran batholiths, recorded synmagmatic deformation that was interpreted as transpressional (Cao et al., 2015; de Saint Blanquat & Tikoff, 1997; Tikoff & de Saint Blanquat, 1997; Tobisch & Cruden, 1995; Tobisch et al., 2000), neutral (Tobisch et al., 1995), or even extensional (Bateman, 1992; Tobisch et al., 1986, 1993). Recent studies thus logically argue that the deformation was more complex and likely partitioned across the arc (e.g., Attia et al., 2022).…”