Evolution Of Volcanic Arcs Research Articles

Spatiotemporal distribution of seamount volume along the Kyushu-Palau Ridge: Implications for rejuvenated volcanism

• Accurate quantification of seamount volcanism reveals multiphase volcanism along the Kyushu–Palau Ridge. • The proximity of Pre-Oligocene lithospheric weak zones to high concentrations of seamount volume indicate tectonic inheritance facilitated magma migration. • Rejuvenated volcanism related to the propagated back-arc spreading during Oligocene contributed to the development of the Kyushu-Palau Ridge. The Kyushu-Palau Ridge (KPR) is a remnant arc that initially formed with the subduction of the Pacific plate beneath the West Philippine Sea. The KPR split from the proto-Izu-Bonin-Mariana (IBM) arc with the back-arc spreading at ∼ 30 Ma. Even though most of the seamounts have been dated, the factors that drive the volcanic arc evolution along the KPR remain unknown. In this study, we quantify the spatiotemporal distribution of the seamount volume along the KPR, representing a quantitative indicator of erupted volcanism. A spatial filtering method based on the White Top-Hat Transform is used to identify seamounts from the bathymetry. Combining seismic data interpretation and gravity data inversion, we estimate the seamount volume distribution along the KPR. Results show that high concentrations of the seamount volume are in proximity to pre-Oligocene lithospheric weak zones, indicating that tectonic inheritance has facilitated magma migration during the early-stage volcanic arc generation. Subsequently, the younger than 30 Ma age of the majority of the seamounts suggests a late-stage rejuvenated volcanism in the Oligocene. In addition, the spatiotemporal variations of the seamount volume in the northern and central segments are synchronous with the propagated spreading of the Perce Vela and Shikoku basins, further indicating that the rejuvenated volcanism was driven by the propagated back-arc spreading. Rejuvenated volcanism can thus be an important contributive factor to remnant volcanic arc formation.

Feedback of Slab Distortion on Volcanic Arc Evolution: Geochemical Perspective From Late Cenozoic Volcanism in SW Japan

AbstractSouthwest Japan is an island arc formed by subduction of the Philippine Sea (PHS) plate. The Quaternary magmatism in this region is characterized by eruptions of high‐Sr andesites and dacites, considered to have been derived by melting of the PHS plate. The loci of these volcanoes spatially coincide with seismic discontinuities of the subducted PHS plate. Thus, the magmatism is interpreted as the result of slab melting at the plate tears. However, the processes that promote slab tearing remain unclear. In this study, we applied geochronological and geochemical analyses to late Cenozoic volcanic rocks in southwest Japan as tracers of slab morphology. Two different magma types, ocean‐island basalt (OIB) and island‐arc basalt (IAB), have occurred over 12 million years (Myr). These two magmas are attributed to different integrations of melts extracted from an originally fertile mantle; the OIBs from high temperature melt (1,300–1,400°C) were extracted at a depth of 40–80 km, whereas the IABs were extracted from a shallower, lower temperature region (30–60 km, 1,200–1,350°C). Secular change in Sr enrichment of IAB likely arose due to a transition of slab‐derived fluids, incorporated into magmas as they formed, from water‐ to melt‐dominant one. Progressive shallowing of the subducted PHS plate is responsible for secular change in the properties of slab‐derived fluids as well as rollback of OIB volcanoes. Production of chemically variable magmas in the Chugoku district is the surface expression of distorting slab morphology by interaction between mantle and the subducting plate.

Complex evolution of volcanic arcs: The lithofacies and palaeogeography of the Cambrian Stavely Arc, Delamerian Fold Belt, Western Victoria

The Mount Stavely Volcanic Complex is a Cambrian greenstone belt in western Victoria (Australia), which formed as a continental arc during subduction of the proto-Pacific plate under Gondwana. While the MSVC has been broadly described in literature, its lithofacies and palaeogeography remains unconstrained. The lithofacies that occur throughout the MSVC were characterised using field work, and diamond drill core from the Geological Survey of Victoria. The majority of the MSVC consists of fragmental facies that were deposited in a deep-marine environment. These deposits were subsequently intruded by melts, which formed the coherent facies; some became either shallow-intrusive or even extrusive. The volcanic processes that formed the Mount Stavely Volcanic Complex are similar to those currently occurring in the present-day Kermadec Arc. Furthermore the submarine nature of these volcanic facies is similar to the Cambrian Mount Read Volcanics in Tasmania.. However, in timing and cause of volcanic activity, not all of these ancient volcanic terranes are related. These findings help constrain the depositional environment in which the Mount Stavely Volcanic Complex was emplaced, which in turn provides important constraints for the tectonic reconstruction of Gondwana.

Volcanism and tectonism in the southern Central Andes: Tempo, styles, and relationships

An important objective of volcanic research is to establish a cause-and-effect relationship between the age of fault kinematics and volcanic arc evolution based on structural and stratigraphic evidence. The predominant hyperarid climate in the Central Andes since Miocene times makes it a world-class area for investigating the evolution of a volcanic arc. This region records the complete development of the late Cenozoic Andean volcanic arc. This study focuses on the interpretation of volcanism in the context of recently dated tectonic structures along the southern Central Andes Volcanic Zone between 24.5° and 27° S. This segment of the arc has had a complex evolution and consists of hundreds of volcanoes, including constructional (monogenetic and polygenetic) and caldera volcanoes. By reviewing and reevaluating the geological maps in the literature, we are able to better constrain the temporal evolution of the central Chilean volcanic arc, including timing and kinematics of regional faults. Recognition of 15 Oligocene to Pleistocene ignimbrites and their sources has allowed us to define 11 caldera systems contemporaneous with effusive constructional volcanoes. The extent of the ignimbrite deposits allows them to be correlated between isolated outcrops that preserve different stratigraphic sequences, enabling the construction of a more complete and accurate volcanic stratigraphy. Two main NE-SW– and N-S–oriented thrust systems dominate the structural architecture of this segment of the arc. The first, located in the Precordillera, was active between 25 and 14 Ma and extends over 200 km to the northeast through the Pedernales-Arizaro thrust fault. Parallel to this thrust, the east-vergent Antofalla thrust fault system developed during Oligocene–Miocene times. The second system, located within the volcanic arc, includes sinuous N-S contractional structures that developed in pulses between the middle and late Miocene. There appears to be a cause-and-effect relationship between tectonic pulses and the development of volcanism, whereby changes in the upper crustal stress field lead to the generation of extensional domains. These conditions favor magma storage at upper crustal levels, thus promoting a suction-pump effect. The coexistence of both dominantly effusive constructional volcanism and explosive caldera volcanism results from the same tectonic conditions that produced shortening, as a consequence of the maximum compressive stress and conjugated extensions. In this paper, we suggest a new model that integrates the coexistence and contemporaneity of compressive structures and the widespread development of effusive constructional volcanism and explosive caldera volcanism along the Andean Oligo-Miocene volcanic arc.

Magmatic control along a strike-slip volcanic arc: The central Aeolian arc (Italy)

The regional stress field in volcanic areas may be overprinted by that produced by magmatic activity, promoting volcanism and faulting. In particular, in strike-slip settings, the definition of the relationships between the regional stress field and magmatic activity remains elusive. To better understand these relationships, we collected stratigraphic, volcanic, and structural field data along the strike-slip central Aeolian arc (Italy): here the islands of Lipari and Vulcano separate the extensional portion of the arc (to the east) from the contractional one (to the west). We collected >500 measurements of faults, extension fractures, and dikes at 40 sites. Most structures are NNE-SSW to NNW-SSE oriented, eastward dipping, and show almost pure dip-slip motion, consistent with an E-W extension direction, with minor dextral and sinistral shear. Our data highlight six eruptive periods during the last 55 ka, which allow considering both islands as a single magmatic system, in which tectonic and magmatic activities steadily migrated eastward and currently focus on a 10 km long × 2 km wide active segment. Faulting appears to mostly occur in temporal and spatial relation with magmatic events, supporting that most of the observable deformation derives from transient magmatic activity (shorter term, days to months), rather than from steady longer-term regional tectonics (102–104 years). More in general, the central Aeolian case shows how magmatic activity may affect the structure and evolution of volcanic arcs, overprinting any strike-slip motion with magma-induced extension at the surface.

Simulation of late Cenozoic South American flat-slab subduction using geodynamic models with data assimilation

The formation mechanisms of flat slabs in South America remain unclear. To quantitatively evaluate the earlier proposed mechanisms, we simulate the post-100 Ma subduction history below South America using 4-D geodynamic models by progressively incorporating plate kinematics, seafloor ages and key tectonic features including the buoyant oceanic crust, continental cratons, oceanic plateaus (i.e. the inferred Inca plateau, subducting Nazca Ridge and Juan Fernandez Ridge), as well as deformable trench profiles according to recent geological reconstructions. We find that, in the absence of an overriding plate and subducting buoyancy features, the seafloor age affects slab dip angle by controlling the slab's mechanical strength (i.e., the resistance to bending) and negative buoyancy (integrated positive density anomaly that enhances bending). Our models show that slab strength dominates its buoyancy at age >30 Ma and the opposite for younger ages. The existence of a thick overriding plate reduces the slab dip by increasing dynamic suction, and individual cratonic roots further lead to along-trench variations of dip angle reduction. While dynamic suction from the overriding plate generates a permanent reduction of the long-wavelength slab dip angle, it is the final addition of subducting oceanic plateau and aseismic ridges that produces the transient and localized flat-slabs as observed. These results suggest that all mechanisms except the buoyancy features affect the slab dip only at large spatial scales. Our best-fit model with all the above tectonic features included provides a good match to both the upper mantle Benioff zones and the temporal evolution of volcanic arcs since the mid-Miocene. The imperfect match of the Peruvian flat-slab is likely associated with the uncertain 3-D configuration of the Amazonian craton.

Subduction zone evolution and low viscosity wedges and channels

Dehydration of subducting lithosphere likely transports fluid into the mantle wedge where the viscosity is decreased. Such a decrease in viscosity could form a low viscosity wedge (LVW) or a low viscosity channel (LVC) on top of the subducting slab. Using numerical models, we investigate the influence of low viscosity wedges and channels on subduction zone structure. Slab dip changes substantially with the viscosity reduction within the LVWs and LVCs. For models with or without trench rollback, overthickening of slabs is greatly reduced by LVWs or LVCs. Two divergent evolutionary pathways have been found depending on the maximum depth extent of the LVW and wedge viscosity. Assuming a viscosity contrast of 0.1 with background asthenosphere, models with a LVW that extends down to 400 km depth show a steeply dipping slab, while models with an LVW that extends to much shallower depth, such as 200 km, can produce slabs that are flat lying beneath the overriding plate. There is a narrow range of mantle viscosities that produces flat slabs (5 to10 × 10 19 Pa s) and the slab flattening process is enhanced by trench rollback. Slab can be decoupled from the overriding plate with a LVC if the thickness is at least a few 10 s of km, the viscosity reduction is at least a factor of two and the depth extent of the LVC is several hundred km. These models have important implications for the geochemical and spatial evolution of volcanic arcs and the state of stress within the overriding plate. The models explain the poor correlation between traditional geodynamic controls, subducting plate age and convergence rates, on slab dip. We predict that when volcanic arcs change their distance from the trench, they could be preceded by changes in arc chemistry. We predict that there could be a larger volatile input into the wedge when arcs migrate toward the trench and visa-versa. The transition of a subduction zone into the flat-lying regime could be preceded by changes in the volatile budget such that the dehydration front moves to shallower depths. Our flat-slab models shed some light on puzzling flat subduction systems, like in Central Mexico, where there is no deformation within the overriding plate above the flat segment. The lack of in-plane compression in Central Mexico suggests the presence of a low viscosity shear zone above the flat slab.

Ophiolites of the Eastern Peninsulas zone (Eastern Kamchatka): Age, composition, and geodynamic diversity

Abstract The geological, geochemical and mineralogical data of dismembered ophiolites of various ages and genesis occurring in accretionary piles of the Eastern Peninsulas of Kamchatka enables us to discriminate three ophiolite complexes: (i) Aptian–Cenomanian complex: a fragment of ancient oceanic crust, composed of tholeiite basalts, pelagic sediments, and gabbroic rocks, presently occurring in a single tectonic slices (Afrika complex) and in olistoplaques in Pikezh complex of the Kamchatsky Mys Peninsula and probably in the mélange of the Kronotsky Peninsula; (ii) Upper Cretaceous complex, composed of highly depleted peridotite, gabbro and plagiogranite, associated with island arc tholeiite, boninite, and high‐alumina tholeiitic basalt of supra‐subduction origin; and (iii) Paleocene–Early Eocene complex of intra‐island arc or back‐arc origin, composed of gabbros, dolerites (sheeted dykes) and basalts produced from oceanic tholeiite melts, and back‐arc basin‐like dolerites. Formation of the various ophiolite complexes is related to the Kronotskaya intra‐oceanic volcanic arc evolution. The first ophiolite complex is a fragment of ancient Aptian–Cenomanian oceanic crust on which the Kronotskaya arc originated. Ophiolites of the supra‐subduction zone affinity were formed as a result of repeated partial melting of peridotites in the mantle wedge up to the subduction zone. This is accompanied by production of tholeiite basalts and boninites in the Kamchatsky Mys segment and plagioclase‐bearing tholeiites in the Kronotsky segment of the Kronotskaya paleoarc. The ophiolite complex with intra‐arc and mid‐oceanic ridge basalt geochemical characteristics was formed in an extension regime during the last stage of Kronotskaya volcanic arc evolution.

Initiation of Iapetus subduction under Irish Avalonia

The Dowery Hill Member of metamorphosed basalt, dolerite and siltstone is here recognized as the oldest exposed volcanic unit of the Lower Ordovician Ribband Group, with a minimum age of early Arenig. Peperites and resedimented hydroclastic breccia demonstrate a volcanic origin for the basalts. The igneous rocks are tholeiitic, with a trace element geochemistry indicative of a subduction-modified fertile mantle source, which we interpret as recording an early stage of volcanic arc evolution. The member is therefore the oldest known component of the volcanic arc generated by subduction of Iapetus oceanic lithosphere under southeastern Ireland. Subduction started earlier than predicted by current plate tectonic models, and these should be re-evaluated.

Revised interpretations of Mesozoic palaeogeography and volcanic arc evolution in the northern Antarctic Peninsula region

Terrestrial sedimentary rocks at Hope Bay, northern Graham Land are well known for their diverse but poorly-preserved fossil flora, previously assigned ages ranging from Early Jurassic-Early Cretaceous. The beds form part of the Botany Bay Group, which comprises several outcrops of terrestrial sediments in northern Graham Land and the South Orkney Islands. A latest Jurassic or earliest Cretaceous age for the Hope Bay plant bearing sequence (and by extension for the rest of the Botany Bay Group) has been adopted in most recent publications dealing with Mesozoic volcanic arc evolution and palaeogeography of the northern Antarctic Peninsula region. New evidence, based upon the study of extensive collections of previously undescribed fossil plants from Hope Bay and nearby Botany Bay, indicates that they should be assigned an Early Jurassic age. The new palaeobotanical findings, combined with recently-published radiometric data from overlying volcanic sequences, show that a Cretaceous age is no longer tenable for these floras nor, therefore, for the Botany Bay Group in Graham Land. Interpretations of Mesozoic volcanic arc evolution and palaeogeography in this region are revised accordingly.

Geochronology of mercury, tin, and fluorite mineralization in northern Mexico

This study was undertaken to obtain reconnaissance isotopic ages on tin, mercury, fluorine, and antimony mineralization in northern Mexico and to determine their temporal relation to the metallogenic evolution of the continental volcanic arc in this region. Deposits were dated using conventional K-Ar and 40 Ar/ 39 Ar analyses of whole rocks and phenocryst separates for altered and unaltered pre- and postore samples. Ore-related rhyolites in three tin deposits (Sombrerete, La Ochoa, and Cerro de los Remedios) formed at 30 to 31 m.y. ago and mineralization probably took place at the same time. The Guadalcazar stock, which hosts disseminated cassiterite, formed at about 28 m.y. ago. Mineralization in the Canoas mercury district formed at 26 to 27 m.y., although mineralization in the other two districts studied (Sain Alto and El Cuarenta) could be limited only to post-37 m.y. and post-40 m.y., respectively. Fluorite deposits hosted by limestone in the Zaragoza and Rio Verde districts formed at 30 to 31 m.y., and smaller, volcanic-hosted deposits in the Inde district could have formed as early as 38 m.y. The only radiometric age related to an antimony district obtained in this study was 36 m.y. for the granodiorite stock at Santa Maria de la Paz, north of the Wadley district. These ages demonstrate that the Sn-Hg-F-Sb mineralization was essentially contemporaneous with the latest phases of base and precious metal mineralization in northern Mexico and suggest that formation of deposits containing these metals is a special stage in the metallogenic evolution of volcanic arcs, which requires a relatively thick crust that is conducive to extensive magmatic differentiation and silicic volcanism.