Geology and geochemistry of Late Quaternary volcanism in northern Harrat Rahat, Kingdom of Saudi Arabia: implications for eruption dynamics, regional stratigraphy and magma evolution

Abstract

Harrat Rahat (<10 Ma) is one of the largest volcanic fields on western Arabia. In the north of the field, some of the youngest volcanic centres evolved through either point-like, complex or multiple aligned vents (i.e. along fissures), and have pyroclastic cones, lapilli fall deposits and/or lava flows associated with them. The products reflect dominantly Hawaiian eruptions, and only one centre experienced phreatomagmatism. Results from new 3He surface-exposure dating provide constraints on stratigraphy of the youngest (<0.3 Ma) products.The rocks are compositionally alkali-basalt and hawaiite, with intra-plate basalt (prevalent mantle (PREMA)) affinity. Each eruption displays a distinct whole-rock composition in an overall linear trend. We suggest that the magma source for each centre is similar, and that composition of the products is different due to different degrees of fractionation. In a single eruption, the magma that reaches the surface first is the least evolved, with the most evolved magma erupting last. We also found that the most primitive magmas erupt less explosively. We think that the degree of magma evolution might correlate with ascent times, assuming that the more evolved magma spent more time en route. We suggest that magma ascent time is likely to be longer than that of other more primitive intra-plate basalts.Supplementary material: Whole-rock chemistry results, mineral chemistry results and fractional crystallization modeling data are available at https://doi.org/10.6084/m9.figshare.c.3488988

Campo Volcánico Monogenético Villamaría-Termales, Cordillera Central, Andes colombianos (Parte II): Características composicionales

“…Bacon et al, 1981;Schonwalder, 2015), así como también permanecer con características composicionales muy similares (e.g. Murcia et al, 2016). En campos volcánicos asociados a ambientes de subducción, el rango de composición tiende a ser relativamente más amplio (e.g.…”

“…Tal condición posiblemente se debe a que en estos últimos, la ausencia de cámaras magmáticas y el ascenso rápido del magma, restringen los procesos de cristalización fraccionada, contaminación cortical y/o mezcla de magmas, haciendo que los productos reflejen características composicionales similares a las del fundido primario (e.g. Murcia et al, 2016). En los campos volcánicos monogenéticos asociados a ambientes de subducción, los magmas usualmente evolucionados sugieren estancamiento en cámaras magmáticas que podrían estar asociadas con la generación de volcanes poligenéticos (e.g.…”

Volcanic history of the northernmost part of the Harrat Rahat volcanic field, Saudi Arabia

“…In addition, many of these volcanic fields remain poorly studied, but growing populations and infrastructure across the region increase the risks from potential future activity (e.g., Lindsay and Moufti, 2014). As a result, the timing, composition, and magmatic processes controlling and influencing activity within these late Cenozoic volcanic fields are being investigated (e.g., Shaw et al, 2003;Moufti et al, 2012Moufti et al, , 2013Duncan and Al-Amri, 2013;Murcia et al, 2015Murcia et al, , 2017Abdelwahed et al, 2016;Duncan et al, 2016;Konrad et al, 2016).…”

“…2), near the city of Al-Madinah Al-Munawarah (hereafter referred to as . Only a few individual eruptions from Harrat Rahat have been studied in detail, with particular emphasis on the youngest appearing scoria cones and lava flows within the volcanic field's more northerly confines close to Al-Madinah (e.g., Camp et al, 1987;Murcia et al, 2015Murcia et al, , 2017. All remaining studies have dealt with this volcanic field in its entirety and have primarily focused on magmatic processes (e.g., Camp and Roobol, 1989;Moufti et al, 2012Moufti et al, , 2013.…”

Lunar Crater volcanic field (Reveille and Pancake Ranges, Basin and Range Province, Nevada, USA)

“…Intraplate volcanism has long been a topic of research focused on basalt petrogenesis and upper mantle composition and structure, due to relatively low degrees of crustal overprinting on geochemical signatures and, in many cases, abundant mantle xenoliths (e.g., Wörner et al, 1986;Farmer et al, 1989; Valentine et al | Lunar Crater volcanic field GEOSPHERE | Volume 13 | Number 2 Lum et al, 1989;Menzies, 1989;Luhr et al, 1995;Witt-Eickschen and Kramm, 1998;Gazel et al, 2012;Cousens et al, 2013;McGee and Smith, 2016). A growing body of literature in the past decade has also focused on physical processes of intraplate volcanoes, including magma ascent, relationships with crustal structure, and eruption (see reviews by Valentine and Gregg, 2008;Németh, 2010;Le Corvec et al, 2013a, 2013b; integrated case studies by Le Corvec et al, 2013c;Murcia et al, 2016). Recent work has been partly aimed at assessing the potential hazards associated with eruptions in monogenetic volcanic fields (e.g., Ort et al, 2008;Valentine and Perry, 2009;Houghton et al, 2006;Németh et al, 2012), but also has been driven by the increasing recognition of the complexity of these small volcanoes, which were traditionally thought to be simple and well understood (e.g., Houghton and Schmincke, 1986;Ort and Carrasco-Nuñez, 2009;Genareau et al, 2010;Martí et al, 2011;Bolós et al, 2012;van Otterloo et al, 2013;Pedrazzi et al, 2016).…”