scholarly journals Establishing genetic relationships between the Takidani pluton and two large silicic eruptions in the Northern Japan Alps

2021 ◽  
Author(s):  
Eva Hartung ◽  
Luca Caricchi ◽  
David Floess ◽  
Simon Wallis ◽  
Satoru Harayama
Keyword(s):  
Genetic Relationships ◽  
Volcanic Eruptions ◽  
Substantial Contribution ◽  
Plumbing System ◽  
Pyroclastic Deposits ◽  
Trace Element Chemistry ◽  
Magmatic Reservoir ◽  
Progressive Growth ◽  
Caldera Floor ◽  
Magmatic Plumbing System

Abstract The Takidani pluton (1.1-1.6 Ma) represents a shallow magmatic reservoir at the base of an exhumed caldera floor. The deposits of two large caldera-forming eruptions including the Nyukawa Pyroclastic Flow Deposit (1.76 Ma; crystal-rich dacite) and the Chayano Tuff and Ebisutoge Pyroclastic Deposits (1.75 Ma; a sequence of crystal-poor rhyolite) are distributed concentrically around the pluton. We use major and trace element chemistry of whole-rock, glass and minerals to show (1) that the crystal-rich dacite (>400 km3 DRE; dense rock equivalent) is the erupted portion of a shallow mush zone constituting the Takidani pluton and (2) that the crystal-poor rhyolite (>100 km3 DRE) was extracted from a deeper part of this vertically extended magmatic plumbing system. Whole-rock geochemistry indicates that the Nyukawa and Takidani compositions were produced dominantly through crystal fractionation of amphibole, pyroxene and plagioclase in the mid-to-lower crust and subsequently emplaced in the upper crust prior to eruption and solidification, respectively. The crystal-poor Chayano-Ebisutoge rhyolite (>100 km3 DRE) is compositionally distinct from the Nyukawa and Takidani magmas and its generation is associated with a substantial contribution of crustal melts. Yet, plagioclase and orthopyroxene textures and chemistry provide strong evidence that the ascending rhyolite percolated through the upper Takidani-Nyukawa mush zone prior to eruption. Overgrowth of “rhyolitic plagioclase” on “xenocrystic dacitic plagioclase” typical of the Takidani-Nyukawa magmas indicates that the extraction and accumulation of the rhyolitic melts could have occurred in less than 10 kyr (i.e. time between eruptions) prior to eruption providing maximum timescales for pre-eruption storage. Overall, our findings show a progressive growth and thermal maturation of a vertically extended magmatic plumbing system over hundreds of thousands of years and imply that large volcanic eruptions can occur in relatively short succession without dramatic changes in the plumbing system, thus, complicating the identification of signs of an impending large eruption.

scholarly journals Statistical analysis of crystal populations and links to volcano deformation for more robust estimates of magma replenishment volumes

Geology ◽  
2019 ◽  
Vol 47 (12) ◽  
pp. 1171-1175
Author(s):  
Lilu Cheng ◽  
Fidel Costa
Keyword(s):  
Statistical Approach ◽  
Population Analysis ◽  
Volcanic Eruptions ◽  
Plumbing System ◽  
Volcano Deformation ◽  
Merapi Volcano ◽  
Robust Estimates ◽  
Minimum Estimate ◽  
Proper Interpretation ◽  
Magma Replenishment

Abstract Forecasting the timing and size of volcanic eruptions requires a proper interpretation of multiparametric monitoring signals. Studies of the erupted rocks can provide critical information on the processes and volcano plumbing system that is needed to decode the monitoring signals. Here we present the results of a petrological study of plagioclase phenocrysts using a new statistical approach that allows us to estimate the amount of intruded magma before eruption. Our crystal population analysis of the 2006 and 2010 CE Merapi volcano (Indonesia) eruptions shows that ∼60 ± 20 vol% of the 2010 magma was left over from the 2006 magma, and thus ∼40 ± 20 vol% was newly intruded magma. Using the published values of the 2010 erupted magma volume, this corresponds to >8 to 20 (±7) × 106 m3 of new magma. This is a minimum estimate and is similar to the inferred pre-eruptive deformation volume (18 ×106 m3), although given the uncertainties, several million cubic meters of magma intruded in 2010 could still be in the Merapi plumbing system. Our approach could be used at other volcanoes to quantify the volume of intruded magma and thus help in better understanding the unrest signals that anticipate eruptions.

scholarly journals Anatomy of the magmatic plumbing system of Los Humeros Caldera (Mexico): implications for geothermal systems

2019 ◽  
Author(s):  
Federico Lucci ◽  
Gerardo Carrasco-Núñez ◽  
Federico Rossetti ◽  
Thomas Theye ◽  
John C. White ◽  
...  
Keyword(s):  
Volcanic Belt ◽  
Mineral Chemistry ◽  
Volcanic Complex ◽  
Geothermal Systems ◽  
Plumbing System ◽  
Geothermal Exploration ◽  
Geothermal Fields ◽  
Mexican Volcanic Belt ◽  
Plumbing Systems ◽  
Magmatic Plumbing System

Abstract. Understanding the anatomy of magma plumbing systems of active volcanoes is essential not only for unraveling magma dynamics and eruptive behaviors, but also to define the geometry, depth and temperature of the heat sources for geothermal exploration. The Pleistocene-Holocene Los Humeros volcanic complex is part of the Eastern Trans-Mexican Volcanic Belt (Central Mexico) and it represents one of the most important exploited geothermal fields in Mexico with ca. 90 MW of produced electricity. A field-based petrologic and thermobarometric study of lavas erupted during the Holocene (post-Caldera stage) has been performed with the aim to decipher the anatomy of the magmatic plumbing system existing beneath the caldera. New petrographical, whole rock major element data and mineral chemistry were integrated within a suite of inverse thermobarometric models. Compared with previous studies where a single voluminous melt-controlled magma chamber (or "Standard Model") at shallow depths was proposed, our results support a more complex and realistic scenario characterized by a heterogeneous multilayered system comprising a deep (ca. 30 km) basaltic reservoir feeding progressively shallower and smaller distinct stagnation layers, pockets and batches up to very shallow conditions (1 kbar, ca. 3 km). Evolution of melts in the feeding system is mainly controlled by differentiation processes via fractional crystallization, as recorded by polybaric crystallization of clinopyroxenes and orthopyroxenes. Moreover, this study attempts to emphasize the importance to integrate field-petrography, texture observations and mineral chemistry of primary minerals to unravel the pre-eruptive dynamics and therefore the anatomy of the plumbing system beneath an active volcanic complex, which notwithstanding the numerous existing works is still far to be well understood. A better knowledge of the heat source feeding geothermal systems is very important to improve geothermal exploration strategies.

scholarly journals Pityusa Patera, Mars: Structural analyses suggest a mega-caldera above a magma chamber at the crust-mantle interface

Geology ◽  
2021 ◽  
Author(s):  
Hannes Bernhardt ◽  
David A. Williams
Keyword(s):  
Finite Element ◽  
Solar System ◽  
Finite Element Model ◽  
Magma Chamber ◽  
Element Model ◽  
Mantle Material ◽  
Pyroclastic Deposits ◽  
Caldera Floor ◽  
Prime Target ◽  
Central Plug

Pityusa Patera is the southernmost of four paterae in the 1.2 × 106 km2 wrinkle-ridged plains-dominated Malea Planum region of Mars. Based on their texture, morphology, and uniqueness to Pityusa Patera, we interpret layered, folded massifs as pyroclastic deposits emplaced during patera formation as a collapse caldera. Such deposits would not be expected in a previously suggested scenario of patera formation by subsidence from lithospheric loading. Our structural measurements and modeling indicate that the folding and high relief of the massifs resulted from ~1.3%–6.9% of shortening, which we show to be a reasonable value for a central plug sagging down into an assumed piston-type caldera. According to a previously published axisymmetric finite-element model, the extent of shortening structures on a caldera floor relative to its total diameter is controlled by the roof depth of the collapsed magma chamber beneath it, which would imply Pityusa Patera formed above a chamber at 57.5–69 km depth. We interpret this value to indicate a magma chamber at the crust-mantle interface, which is in agreement with crust-penetrating ring fractures and mantle flows expected from the formation of the Hellas basin. As such, the folded massifs in Pityusa Patera, which are partially superposed by ca. 3.8 Ga wrinkle-ridged plains, should consist of primordial mantle material, a theory that might be assessed by future hyperspectral observations. In conclusion, we do not favor a formation by load-induced lithospheric subsidence but suggest Pityusa Patera to be one of the oldest extant volcanic landforms on Mars and one of the largest calderas in the solar system, which makes the folded, likely mantle-derived deposits on its floor a prime target for future exploration.

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