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High-resolution geochronology is essential for determining the growth rate of volcanoes, which is one of the key factors for establishing the periodicity of volcanic eruptions. However, there are less high-resolution eruptive histories (106 years) determined for long-lived submarine arc volcanic complexes than for subaerial complexes, since submarine volcanoes are far more difficult to observe than subaerial ones. In this study, high-resolution geochronology and major-element data are presented for the Milos volcanic field (VF) in the South Aegean Volcanic Arc, Greece. The Milos VF has been active for over 3 Myr, and the first 2106 years of its eruptive history occurred in a submarine setting that has been emerged above sea level. The long submarine volcanic history of the Milos VF makes it an excellent natural laboratory to study the growth rate of a long-lived submarine arc volcanic complex. This study reports 21 new high-precision 40Ar=39Ar ages and majorelement compositions for 11 volcanic units of the Milos VF. This allows us to divide the Milos volcanic history into at least three periods of different long-Term volumetric volcanic output rate (Qe). Periods I (submarine, 3.3-2.13 Ma) and III (subaerial, 1.48 Ma-present) have a low Qe of 0.90.510-5 and 0.250.0510-5 km3 yr-1, respectively. Period II (submarine, 2.13-1.48 Ma) has a 3-12 times higher Qe of 3.01.710-5 km3 yr-1. The Qe of the Milos VF is 2-3 orders of magnitude lower than the average for rhyolitic systems and continental arcs.

The Himalayan syntaxes, characterized by extreme rates of rock exhumation co-located with major trans-orogenic rivers, figure prominently in the debate on tectonic versus erosional forcing of exhumation. Both the mechanism and timing of rapid exhumation of the Namche Barwa massif in the eastern syntaxis remain controversial. It has been argued that coupling between crustal rock advection and surface erosion initiated in the late Miocene (8–10 Ma). Recent studies, in contrast, suggest a Quaternary onset of rapid exhumation linked to a purely tectonic mechanism. We report new multisystem detrital thermochronology data from the most proximal Neogene clastic sediments downstream of Namche Barwa and use a thermo-kinematic model constrained by new and published data to explore its exhumation history. Modeling results show that exhumation accelerated to ∼4 km/m.y. at ca. 8 Ma and to ∼9 km/m.y. after ca. 2 Ma. This three-stage history reconciles apparently contradictory evidence for early and late onset of rapid exhumation and suggests efficient coupling between tectonics and erosion since the late Miocene. Quaternary acceleration of exhumation is consistent with river-profile evolution and may be linked to a Quaternary river-capture event.

Coesite- and microdiamond- bearing ultra-high pressure (UHP) eclogites in the North Qinling terrane have been widely retrogressed to amphibolites. Previous geochronological studies on these UHP rocks mainly focused on the timing of peak eclogite facies metamorphism. The Kanfenggou UHP metamorphic domain is one of the best-preserved coesite-bearing eclogite occurrences in the North Qinling terrane. In this study, mafic amphibolites and host schists from this domain were collected for 40Ar/39Ar dating to constrain their retrograde evolution. Two generations of amphibole are recognized based on their mineral parageneses and 40Ar/39Ar ages. A first generation of amphibole from garnet amphibolites yielded irregularly-shaped age spectra with anomalously old apparent ages. Isochron ages of 484–473 Ma and initial 40Ar/36Ar ratios of 3695–774 are obtained from this generation of amphibole, indicating incorporation of excess argon. Second generation amphibole occurs in epidote amphibolites yielded flat age spectra with plateau ages of 464–462 Ma without evidence for excess argon. These ages suggest that the amphibolite-facies metamorphism has taken place as early as 484 Ma and lasted until 462 Ma for the North Qinling UHP metamorphic rocks. Phengite from the country-rock schists yielded 40Ar/39Ar plateau ages of 426–396 Ma, with higher phengite Si contents associated with the older the plateau ages. Based on our new 40Ar/39Ar ages and previous zircon U[sbnd]Pb geochronological data, we construct a new detailed pressure-temperature-time (P-T-t) path illustrating the retrograde metamorphism and exhumation rate of the North Qinling eclogites and host schists. The P-T-t path suggests that these UHP metamorphic rocks experienced initial medium-to-high exhumation rates (ca. 8.7 mm/yr) during the Early Ordovician (489–484 Ma), which was mainly derived from buoyancy forces

The location and crustal structure of hotspot tracks in the South Atlantic reflectwhere melts related to sluggishly flowing plume material can reach the plate surface. This raises the paradox of how long-lived, age progressive hotspot tracks can arise in the absence of closely spaced, narrow mantle plumes. Here we show that young hotspot trails in the southern South Atlantic are located above bands of seismically slowmaterial in the asthenosphere, which we interpret as channels of fast-flowing asthenosphere fed by a large scale plume upwelling from the African LLSVP. A broad region of seismically slow asthenosphere in the vicinity of Paraná continental flood basalts may be indicative of a long-lived, large scale plume under the South American plate. We propose that hotspot tracks developed above fast flow channels in the asthenosphere that evolved between these largescale plumes as they migrated apart with the African and South American plates, respectively. A progression fromcontinental flood basalts to broad aseismic ridges (e.g.,Walvis Ridge-Rio Grande Rise), to lowvolume intraplate hotspot tracks (e.g., Tristan-Gough; Discovery; Shona and Bouvet) reflects the interplay between tectonic setting and asthenosphere flow channels driven by waning pulsations from these diverging LLSVP plumes. We link the splitting of the Walvis Ridge into isotopically distinct, age-progressive intraplate sub-tracks about 72 Ma to the first sampling of material rising from the African LLSVP plume, perhaps as weak shallow longlived plumes. Faster flowing asthenosphere enables melts related to LLSVP plumes to reach the plate surface via spreading and tectonic boundaries, and as low-volume intraplate hotspot (sub)tracks. The concept that asthenosphere flowchannels and hotspot tracks evolve together between pulsating deep-seated plumes under Africa and South America suggests that LLSVPs might be a significant force in driving continental rifting and (absolute) plate motion.

The Hindu Kush-Kohistan-Karakoram region is critical to understanding the long-term accretion history of the south Asian margin pre- and post-India-Asia collision and the impact of these collisions on the development of high topography. However, knowledge about this region remains incomplete due to sparse studies. Here, we present a study comprising detrital zircon U-Pb geochronology, detrital muscovite 40Ar/39Ar thermochronology, and numerical modeling on 40Ar/39Ar dates. The study identifies zircon U-Pb age peaks at 200 Ma, 110–130 Ma, 60–80 Ma, and 28–40 Ma, supporting the polyphase collisions and crustal growth in the south Asian margin. Modeling study reveals fast cooling/erosion at 115–129 Ma, 69–71 Ma, 27–35 Ma, and <8 Ma, which are synchronous with collision related crustal growth, indicating the significant impact of accretion both prior to and post India-Asia collision. This study, along with studies in eastern Karakoram, reveals along-strike variations in erosion and exhumation with young (since late Miocene) intense erosion focusing on the east-central Karakoram. We suggest that this east-west spatial variation in exhumation may have been associated with more intense crustal shortening, and thus the greater crustal thickness, topographic relief and altitude observed in the eastern, compared to western, Karakoram.