INDIRECT TECTONOMAGMATIC LINKS IN THE CRETACEOUS SIERRA NEVADA ARC (Invited Presentation)

Updated syntheses of new and existing map, field, structural, geochemical, and geochronological data from the central Sierra Nevada batholith (CA, USA) allow assessment of a wide range of models about the interplay between arc activity, tectonism, lithospheric evolution, and geodynamics. These models propose relationships between flare-ups, arc migration, and strain partitioning as well as the smaller scale spatiotemporal patterns of magmatism and deformation within the arc. Focusing on the Cretaceous age Sierra Nevada arc, voluminous flare-up magmatism occurred before, throughout, and after intra-arc orogenesis with plutons emplaced far from, adjacent to, and coincident with coeval ductile shear zones. Application of geometric probability methods reveals that ca. 125-85 Ma intrusions intersect broadly coeval shear zones no more often than would be expected by random chance and are thus uncorrelated. Even where the transpressional northern Sierra Crest shear zone and the margin of the Tuolumne Intrusive Suite appear to be coincident, proximity analysis on seamless 1:10,000-scale map data reveals that the core of the shear zone is too distant from intrusive contacts to have accommodated Tuolumne Intrusive Suite emplacement. Thus, shear zones did not control the location of pluton emplacement nor did eastward migration of magmatism control the location or style of intra-arc deformation. Instead, the Cretaceous age arc exemplifies indirect links between magmatism, tectonism, and broader geodynamics. Distinct lithospheric signatures of the pre-batholithic framework terranes exert first-order control on the radiogenic isotope compositions of the migrating arc, which are further modulated by magmatic system processes. An estimated ~20% of intra-arc shortening ca. 105-96 Ma is consistent with coeval increases in crustal thickness. Order of magnitude variation in mantle magma production over 10’s of millions of years is uncorrelated with geodynamic parameters, which stands in contrast with proposed orogenic cyclicity models or subduction rate-magma production relationships. Counterintuitively, the thermal and mechanical impacts of magmatism do not localize deformation in direct proximity to plutons on shorter spatiotemporal scales or at broader scales into the arc itself, rather than the across-strike foreland or forearc regions.