Investigation of long-term geochemical variations and magmatic processes at Mount St. Helens

Geofluids ◽  
2013 ◽  
Vol 13 (4) ◽  
pp. 440-452 ◽  
Author(s):  
M. J. Severs ◽  
K. J. Gryger ◽  
S. A. Makin ◽  
R. J. Bodnar ◽  
W. B. Bradford
Keyword(s):  
Magmatic Processes ◽  
Geochemical Variations ◽  
Mount St Helens

scholarly journals Analysis of Hydrothermal Systems Beneath Tayukeng through Long-Term Geochemical Signals of Hydrothermal Fluids in Tatun Volcano Group, Taiwan

2021 ◽  
Vol 18 (14) ◽  
pp. 7411
Author(s):  
Hsin-Fu Yeh ◽  
Hung-Hsiang Hsu
Keyword(s):  
Surface Temperature ◽  
Hydrothermal System ◽  
Hydrothermal Fluid ◽  
Thermal Water ◽  
Hydrothermal Systems ◽  
Hydrothermal Fluids ◽  
Geochemical Variations ◽  
Northern Taiwan

The Tatun Volcano Group (TVG) is located in northern Taiwan and consists of many springs and fumaroles. The Tayukeng (TYK) area is the most active fumarole site in the TVG. In this study, we analyzed the long-term geochemical variations of hydrothermal fluids and proposed a mechanism responsible for the variation in TYK. There are two different aquifers beneath the TYK area: a shallow SO42−-rich aquifer and a deeper aquifer rich in Cl−. TYK thermal water was mainly supplied by the shallow SO42−-rich aquifer; therefore, the thermal water showed high SO42− concentrations. After 2015, the inflow of deep thermal water increased, causing the Cl− concentrations of the TYK to increase. Notably, the inferred reservoir temperatures based on quartz geothermometry increased; however, the surface temperature of the spring decreased. We inferred that the enthalpy was lost during transportation to the surface. Therefore, the surface temperature of the spring does not increase with an increased inflow of deep hydrothermal fluid. The results can serve as a reference for understanding the complex evolution of the magma-hydrothermal system in the TVG.

scholarly journals Diffusion Timescales of Magmatic Processes in the Moinui Lava Eruption at Mauna Loa, Hawai`i, as Inferred from Bimodal Olivine Populations

2020 ◽  
Vol 61 (7) ◽  
Author(s):  
F K Couperthwaite ◽  
T Thordarson ◽  
D J Morgan ◽  
J Harvey ◽  
M Wilson
Keyword(s):  
Lava Flow ◽  
Storage Conditions ◽  
Magma Storage ◽  
Mauna Loa ◽  
Low Viscosity ◽  
Lava Flow Field ◽  
Magmatic Processes ◽  
Geochemical Variations ◽  
And Storage ◽  
Time Information

Abstract The 2·1 ka Moinui lava flow field, erupted from the southwest rift zone of Mauna Loa, Hawai`i, exhibits striking textural and geochemical variations, that can be used to interpret magma processes pre-, syn- and post-eruption. From this lava flow, the duration of magma storage and storage conditions, the timescales over which magma is transported to the surface, and flow emplacement mechanisms at Mauna Loa are determined. Electron microprobe analysis (EMPA) and diffusion chronometry of olivine crystals identify two distinct crystal populations: a primitive, polyhedral olivine population with core compositions of Fo90–88 and a more evolved, platy olivine population with core compositions of Fo83–82. Fe–Mg diffusion modelling of these olivine populations gives distinct timescales for each population; platy olivines yield timescales of days up to a few weeks, while polyhedral olivines yield timescales of months to years. Despite the nature of a well-insulated pāhoehoe flow, meaning that post-emplacement diffusion continues for some time, a wealth of time information can be retrieved concerning pre-eruptive magmatic processes as well as the processes associated with the lava extrusion. The short timescales obtained from the platy olivine crystals and the observed equilibrium between its cores and ambient melt suggest late-stage nucleation and crystal growth in the shallow conduit and during lava emplacement. Conversely, the longer timescales and olivine-melt disequilibrium of the polyhedral olivine crystals suggests accumulation from a deeper source and subsequent transportation to shallow magma storage beneath the summit of Mauna Loa months, or even years before eruption. The chemical and textural details of the Moinui lava reflect the mode of flow emplacement and may have implications for the interpretation of the distribution of spinifex and cumulate olivine within komatiites; high-temperature, low-viscosity lavas, common in the Archean.

scholarly journals Magmatic Processes at La Soufrière de Guadeloupe: Insights From Crystal Studies and Diffusion Timescales for Eruption Onset

2021 ◽  
Vol 9 ◽  
Author(s):  
Abigail Metcalfe ◽  
Séverine Moune ◽  
Jean-Christophe Komorowski ◽  
Geoff Kilgour ◽  
David E. Jessop ◽  
...  
Keyword(s):  
Large Scale ◽  
Probability Distributions ◽  
Crisis Response ◽  
Data Set ◽  
Eruption Style ◽  
Magmatic Processes ◽  
Backscattered Electron ◽  
And Diffusion ◽  
Magmatic Timescales

Signals of volcanic unrest do not usually provide insights into the timing, size and style of future eruptions, but detailed analysis of past eruptions may uncover patterns that can be used to understand future eruptive behavior. Here, we examine basaltic-andesitic to andesitic eruption deposits from La Soufrière de Guadeloupe, covering a range of eruption styles, ages and magnitudes. Our work is timely given unrest at La Soufrière de Guadeloupe has increased over the last 25 years. We constrain the timescales of magmatic processes preceding four eruptions: 1657 Cal. CE (Vulcanian), 1010 Cal. CE (Plinian), ∼341 Cal. CE (Strombolian) and 5680 Cal. BCE (La Soufrière de Guadeloupe’s first known Plinian eruption). Using crystal-specific analyses of diffusion in orthopyroxenes, we calculate the timescale occurring between the last recharge/mixing event in the magma reservoir and the eruption. We use backscattered electron images, coupled with EMPA of the outermost crystal rim, to derive magmatic timescales. We model the timescale populations as random processes whose probability distributions provide expected (“mean”) timescales and the associated standard errors for each eruption. This provides a new statistical method for comparing magmatic timescales between disparate eruptions. From this, we obtain timescales of magma storage at La Soufrière de Guadeloupe ranging from 34.8 ± 0.4 days to 847 ± 0.4 days, with no clear distinction between eruption style/size and timescales observed. Based on these data, magmatic interaction timescales are a poor predictor of eruption style/size. This study shows that magmatic processes prior to eruption can occur on relatively short timescales at La Soufrière de Guadeloupe. Further to this basaltic-andesitic to andesitic volcanoes can rapidly produce large-scale eruptions on short timescales. These relatively short timescales calculated for volcanic processes at this system constitute a critical new data set and warrant an urgency in enhancing modeling and interpretation capabilities for near-real time monitoring data. These integrated efforts will improve early warning, eruption forecasting and crisis response management for different scenarios, as well as planning for long-term risk reduction.

Combining (U-Th-Sm)/He dating and geochemical budget to understand laterite formation

2020 ◽  
Author(s):  
Claire Ansart ◽  
Damien Calmels ◽  
Cécile Gautheron ◽  
Gaël Monvoisin ◽  
Pierre Agrinier ◽  
...  
Keyword(s):  
Environmental Conditions ◽  
Chemical Weathering ◽  
Equatorial Position ◽  
Secondary Minerals ◽  
Weathering Processes ◽  
Fe Oxides ◽  
Tropical Conditions ◽  
Geochemical Variations ◽  
Climate Evolution

<p>Laterite formations are deep regoliths, up to one hundred of meters thick, that represent about 80% of the global soil volume. Formed under tropical conditions, laterites result from successive chemical weathering reactions over long periods up to tens of millions of years. Laterites can thus be seen as both an actor of the long-term carbon cycle, through CO<sub>2</sub> consumption by silicate weathering and witness of the long-term climate evolution. Indeed, secondary minerals found nowadays in lateritic profiles may have recorded past environmental conditions that prevailed at the time of their formation. Despite the large distribution of lateritic formations around the world, their timing and processes of formations as well as their preservation over long period of time remain unclear.</p><p>Here, we investigate an entire weathering profile developed on the Guiana Shield, in Brownsberg mountains, Suriname. The sampling region has remained in equatorial position for the last 100 Myr and has seen lateritic development since early Tertiary [1]. Such latitudinal stability offers the possibility to look at links between long-term climate evolution or climatic events and long-term chemical weathering processes.</p><p>The lateritic profile shows a strong loss in both alkali and alkaline-earth elements as well as a desilication, and an enrichment in Fe, particularly in the duricrust. The study of trace elements and rare earth elements highlights various geochemical processes behind the development of a lateritic – bauxitic profile.</p><p> (U-Th-Sm)/He ages of iron oxides from the duricrust show the presence of multiple generations of Fe oxides, demonstrating that the Brownsberg profile underwent multiple dissolution and recrystallization phases since its formation, at least 19.9 ± 1.8 Ma ago. These successive weathering processes may have led to the particular enrichment in the profile such as the one observed for Fe and V in the duricrust. Measurement of d18O – dD on secondary minerals, i.e. kaolinite and Fe-oxides s.l., will help to connect mineralogical and geochemical variations with the environmental conditions that prevailed at the time of their formation [2].</p><p>[1] Theveniaut and Freyssinet, 2002. Pal. Pal. Pal., 178, 91-117</p><p>[2] Girard et al., 2000. GCA, 64 n°3, 409 – 426</p>

Recovery of net primary production in subalpine meadows of Mount St. Helens following the 1980 eruption

1988 ◽  
Vol 66 (5) ◽  
pp. 989-997 ◽  
Author(s):  
William A. Pfitsch ◽  
L. C. Bliss
Keyword(s):  
Primary Production ◽  
Net Primary Production ◽  
Summer Precipitation ◽  
Individual Species ◽  
Community Members ◽  
Nutrient Pools ◽  
Subalpine Meadows ◽  
Weather Patterns ◽  
Mount St Helens

The deposition of 5–10 cm of tephra from the 1980 eruption of Mount St. Helens had no more effect than subsequent yearly weather fluctuations on the net primary production of subalpine meadows. The net primary production of areas subject to cold mudflows slowly increased as surviving plants resprouted through the eroded surface and has remained below that of tephra deposition areas. The net primary production of tephra deposition areas fluctuated dramatically (coefficient of variation = 40%) in the seven summers following the eruption. An inverse relationship between net primary production and nutrient concentration of individual species contributed to stability in aboveground nutrient pools from year to year. The dominant community members responded similarly to differences among years in summer precipitation, with little evidence of compensatory growth that would help stabilize community production. Tephra greatly inhibited seedling establishment. Species density (number of species per square metre) and diversity (H′) declined in a community having species that rely on sexual reproduction for persistence and also in experimental tephra addition plots in a more species-rich community. These results indicate that although the short-term effect of tephra deposition on net primary production was minor, the long-term consequence will be of community simplification, which will contribute to fluctuation in net primary production in response to yearly weather patterns.

scholarly journals Excess argon in Mount St. Helens plagioclase as a recorder of magmatic processes

2001 ◽  
Vol 28 (22) ◽  
pp. 4279-4282 ◽  
Author(s):  
Paul W. Layer ◽  
James E. Gardner
Keyword(s):  
Excess Argon ◽  
Magmatic Processes ◽  
Mount St Helens

scholarly journals How do the grain size characteristics of a tephra deposit change over time?

2021 ◽  
Vol 83 (7) ◽  
Author(s):  
Nick A. Cutler ◽  
R. T. Streeter ◽  
A. J. Dugmore ◽  
E. R. Sear
Keyword(s):  
Grain Size ◽  
Size Distributions ◽  
Tephra Layer ◽  
Distinctive Features ◽  
Tephra Deposit ◽  
Grain Size Distributions ◽  
Tephra Layers ◽  
Over Time ◽  
Mount St Helens

AbstractVolcanologists frequently use grain size distributions (GSDs) in tephra layers to infer eruption parameters. However, for long-past eruptions, the accuracy of the reconstruction depends upon the correspondence between the initial tephra deposit and preserved tephra layer on which inferences are based. We ask: how closely does the GSD of a decades-old tephra layer resemble the deposit from which it originated? We addressed this question with a study of the tephra layer produced by the eruption of Mount St Helens, USA, in May 1980. We compared grain size distributions from the fresh, undisturbed tephra with grain size measurements from the surviving tephra layer. We found that the overall grain size characteristics of the tephra layer were similar to the original deposit, and that distinctive features identified by earlier authors had been preserved. However, detailed analysis of our samples showed qualitative differences, specifically a loss of fine material (which we attributed to ‘winnowing’). Understanding how tephra deposits are transformed over time is critical to efforts to reconstruct past eruptions, but inherently difficult to study. We propose long-term, tephra application experiments as a potential way forward.

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