Detrital zircon record of Phanerozoic magmatism in the southern Central Andes

Abstract

The spatial and temporal distribution of arc magmatism and associated isotopic variations provide insights into the Phanerozoic history of the western margin of South America during major shifts in Andean and pre-Andean plate interactions. We integrated detrital zircon U-Th-Pb and Hf isotopic results across continental magmatic arc systems of Chile and western Argentina (28°S–33°S) with igneous bedrock geochronologic and zircon Hf isotope results to define isotopic signatures linked to changes in continental margin processes. Key tectonic phases included: Paleozoic terrane accretion and Carboniferous subduction initiation during Gondwanide orogenesis, Permian–Triassic extensional collapse, Jurassic–Paleogene continental arc magmatism, and Neogene flat slab subduction during Andean shortening. The ~550 m.y. record of magmatic activity records spatial trends in magma composition associated with terrane boundaries. East of 69°W, radiogenic isotopic signatures indicate reworked continental lithosphere with enriched (evolved) εHf values and low (<0.65) zircon Th/U ratios during phases of early Paleozoic and Miocene shortening and lithospheric thickening. In contrast, the magmatic record west of 69°W displays depleted (juvenile) εHf values and high (>0.7) zircon Th/U values consistent with increased asthenospheric contributions during lithospheric thinning. Spatial constraints on Mesozoic to Cenozoic arc width provide a rough approximation of relative subduction angle, such that an increase in arc width reflects shallower slab dip. Comparisons among slab dip calculations with time-averaged εHf and Th/U zircon results exhibit a clear trend of decreasing (enriched) magma compositions with increasing arc width and decreasing slab dip. Collectively, these data sets demonstrate the influence of subduction angle on the position of upper-plate magmatism (including inboard arc advance and outboard arc retreat), changes in isotopic signatures, and overall composition of crustal and mantle material along the western edge of South America.

Sedimentary Record of the middle Cretaceous uplift across the Gangdese magmatic arc system in Southern Tibet

“…Topography of the arc massif played a considerable role in Cenozoic climate change of the interior Tibetan Plateau by enhancing the monsoonal climate system and acting as an orographic barrier to Neo‐Tethys Ocean moisture sources to the south (DeCelles et al., 2007; Ding et al., 2014; Spicer, 2017; Spicer et al., 2021; Xu et al., 2022). In ancient active‐margin settings, the sedimentary records within forearc and retroarc strata are excellent proxies for arc magmatism, paleotopography of the arc, and regional drainage patterns between the arc and associated basins (Barth et al., 2013; Capaldi et al., 2021; de Silva et al., 2015; DeGraaff‐Surpless & Graham, 2002; Malkowski, Schwartz, et al., 2017; Schwartz et al., 2021; Sharman et al., 2015). In the following, we compare a compilation of detrital and igneous zircon U‐Pb ages and zircon Lu‐Hf isotopic signatures from Central Lhasa, the Gangdese arc (Figure 10a,b), and the associated Xigaze forearc basin and Linzhou retroarc foreland basin (Figure 10c).…”

“…Sedimentary basins adjacent to subduction‐related continental arcs record the intricate history of convergent plate margins (Figure 1; Ingersoll, 1988; Dickinson, 1995; Einsele, 2000). Subduction related basins can (1) act as archives for the magmatic, tectonic, and topographic evolution of the arc (Barth et al., 2013; Capaldi et al., 2021; de Silva et al., 2015; Ingersoll, 1979; Wu et al., 2010; Zhu et al., 2023), (2) inform paleogeographic reconstructions and regional drainage patterns between the arc and forearc/retroarc basin (Finzel et al., 2016; Hao et al., 2022; Sharman et al., 2015), and (3) make up for the lack of records in the arc area caused by topographic uplift and denudation, or the destruction of records by younger magmatism and metamorphism (Dobbs et al., 2021; Schwartz et al., 2021; Surpless, 2015). Furthermore, active marginal settings are commonly characterized by narrow shelves that effectively transport sediments to deep‐water forearc basins (Sømme et al., 2009).…”

Andean retroarc-basin dune fields and Pampean Sand Sea (Argentina): Provenance and drainage changes driven by tectonics and climate

“…The Sierras Pampeanas are a series of mainly eastward-tilted blocks bounded by steeply dipping and 114 N-S-striking reverse faults that started to be uplifted within the retroarc region in the late Miocene, 115 after a long period of peneplanation and limited burial (Jordan et al, 1989;Goddard and Carrapa, 116 2018;. The geological history documented by these blocks includes the intrusion 117 of granitoid batholiths above an eastward-dipping subduction zone during the Famatinian cycle 118 (Ramos et al, 1986;Capaldi et al, 2021). Minor Devonian to Carboniferous plutonism was followed 119 by accumulation of up to 5 km-thick Carboniferous-Triassic fluvial clastic sediments (Dahlquist et 120 al., 2021).…”

Transcontinental retroarc sediment routing controlled by subduction geometry and climate change (Central and Southern Andes, Argentina)

“…Relationships among subduction geometry, magmatic activity and sediment composition. (a) The Pampean flat‐slab segment corresponds to a magmatic gap, highest structural elevation and exposure of deeper‐seated tectono‐stratigraphic basement levels of the Andean orogen (slab depth after Capaldi et al., 2021). (b) Abundance of quartz (Q), K‐feldspar (KF), sedimentary to low‐rank metasedimentary rock fragments (Lsm) and amphibole (Amp) all reach maximum in coincidence with the magmatic gap and decrease southwards, where volcanic to low‐rank metavolcanic rock fragments (Lvm), plagioclase (P) and pyroxene derived from the Southern Volcanic Zone progressively increase.…”