scholarly journals Volcanic plumbing filters on ocean-island basalt geochemistry

Geology ◽  
2021 ◽  
Author(s):  
Teresa Ubide ◽  
Patricia Larrea ◽  
Laura Becerril ◽  
Carlos Galé
Keyword(s):  
Melt Inclusions ◽  
Geochemical Data ◽  
Ocean Island ◽  
El Hierro ◽  
Low Viscosity ◽  
Plumbing Systems ◽  
Basalt Geochemistry ◽  
Filtering Effect ◽  
Crystal Accumulation ◽  
Parental Melts

Ocean-island basalts (OIBs) are considered to be messengers from the deep mantle, yet the filtering effect of the plumbing systems that bring OIB melts to the surface remains poorly assessed. We investigated volcanic products from El Hierro island (Canary Islands) from textural and chemical perspectives. The majority of geochemical data cluster at relatively fractionated basaltic compositions of 5 wt% MgO. Compositions ≥10 wt% MgO are porphyritic whole rocks that accumulate mafic minerals. Near-primary melts do not erupt. Instead, we show that carrier melts (crystal-free whole rocks, glasses, and melt inclusions) are consistently buffered to low-MgO compositions during passage through the plumbing system. We tested our model of melt fractionation and crystal accumulation on a global compilation of OIBs. Similar to El Hierro, the majority of data cluster at evolved compositions of 5 wt% MgO (alkaline) to 7 wt% MgO (tholeiitic). Modeling the fractionation of OIB parental melts, we show that with 50% crystallization, OIB melts reach 5 wt% MgO with reduced density, increased volatile content, and overall low viscosity, becoming positively buoyant relative to wall rocks and highly eruptible when reaching volatile saturation at depths around the crust-mantle boundary. Under these conditions, 5 wt% MgO OIB “sweet spot” melts are propelled to the surface and erupt carrying an assortment of recycled crystals. This mechanism is consistent with the petrography and chemistry of erupted products and suggests OIB volcanoes are dominated by low-MgO basaltic melts.

scholarly journals Mantle Melting and Magmatic Processes Under La Picada Stratovolcano (CSVZ, Chile)

2019 ◽  
Vol 60 (5) ◽  
pp. 907-944 ◽  
Author(s):  
Jacqueline Vander Auwera ◽  
Olivier Namur ◽  
Adeline Dutrieux ◽  
Camilla Maya Wilkinson ◽  
Morgan Ganerød ◽  
...  
Keyword(s):  
Fractional Crystallization ◽  
Geochemical Data ◽  
Upper Crust ◽  
Volcanic Zone ◽  
Nazca Plate ◽  
Southern Volcanic Zone ◽  
Magmatic Processes ◽  
Crystal Accumulation ◽  
Primary Magmas ◽  
Differentiation Trend

Abstract Where and how arc magmas are generated and differentiated are still debated and these questions are investigated in the context of part of the Andean arc (Chilean Southern Volcanic Zone) where the continental crust is thin. Results are presented for the La Picada stratovolcano (41°S) that belongs to the Central Southern Volcanic Zone (CSVZ) (38°S–41·5°S, Chile) which results from the subduction of the Nazca plate beneath the western margin of the South American continent. Forty-seven representative samples collected from different units of the volcano define a differentiation trend from basalt to basaltic andesite and dacite (50·9 to 65·6 wt % SiO2). This trend straddles the tholeiitic and calc-alkaline fields and displays a conspicuous compositional Daly Gap between 57·0 and 62·7 wt % SiO2. Interstitial, mostly dacitic, glass pockets extend the trend to 76·0 wt % SiO2. Mineral compositions and geochemical data indicate that differentiation from the basaltic parent magmas to the dacites occurred in the upper crust (∼0·2 GPa) with no sign of an intermediate fractionation stage in the lower crust. However, we have currently no precise constraint on the depth of differentiation from the primary magmas to the basaltic parent magmas. Stalling of the basaltic parent magmas in the upper crust could have been controlled by the occurrence of a major crustal discontinuity, by vapor saturation that induced volatile exsolution resulting in an increase of melt viscosity, or by both processes acting concomitantly. The observed Daly Gap thus results from upper crustal magmatic processes. Samples from both sides of the Daly Gap show contrasting textures: basalts and basaltic andesites, found as lavas, are rich in macrocrysts, whereas dacites, only observed in crosscutting dykes, are very poor in macrocrysts. Moreover, modelling of the fractional crystallization process indicates a total fractionation of 43% to reach the most evolved basaltic andesites. The Daly Gap is thus interpreted as resulting from critical crystallinity that was reached in the basaltic andesites within the main storage region, precluding eruption of more evolved lavas. Some interstitial dacitic melt was extracted from the crystal mush and emplaced as dykes, possibly connected to small dacitic domes, now eroded away. In addition to the overall differentiation trend, the basalts to basaltic andesites display variable MgO, Cr and Ni contents at a given SiO2. Crystal accumulation and high pressure fractionation fail to predict this geochemical variability which is interpreted as resulting from variable extents of fractional crystallization. Geothermobarometry using recalculated primary magmas indicates last equilibration at about 1·3–1·5 GPa and at a temperature higher than the anhydrous peridotite solidus, pointing to a potential role of decompression melting. However, because the basalts are enriched in slab components and H2O compared to N-MORB, wet melting is highly likely.

Lead isotope signatures of Kerguelen plume-derived olivine-hosted melt inclusions: Constraints on the ocean island basalt petrogenesis

Lithos ◽  
2014 ◽  
Vol 198-199 ◽  
pp. 153-171 ◽  
Author(s):  
Anastassia Y. Borisova ◽  
François Faure ◽  
Etienne Deloule ◽  
Michel Grégoire ◽  
Frédéric Béjina ◽  
...  
Keyword(s):  
Lead Isotope ◽  
Melt Inclusions ◽  
Ocean Island Basalt ◽  
Ocean Island ◽  
Kerguelen Plume ◽  
Island Basalt

Composition and conditions of formation of the parental melts of Jurassic dolerites of southwestern Crimea: Evidence from melt inclusions in olivine phenocrysts

Petrology ◽  
2017 ◽  
Vol 25 (3) ◽  
pp. 272-303 ◽  
Author(s):  
D. V. Popov ◽  
N. Nekrylov ◽  
P. Yu. Plechov ◽  
V. D. Shcherbakov ◽  
M. V. Portnyagin ◽  
...  
Keyword(s):  
Melt Inclusions ◽  
Southwestern Crimea ◽  
Parental Melts

scholarly journals Magmatic architecture below the Okataina Volcanic Centre, Taupō Volcanic Zone, Aotearoa New Zealand, inferred from basalt geochemistry

2021 ◽  
Author(s):  
Ery Hughes ◽  
Sally Law ◽  
Geoff Kilgour ◽  
Jon Blundy ◽  
Heidy Mader
Keyword(s):  
New Zealand ◽  
Melt Inclusions ◽  
Basaltic Magma ◽  
Taupo Volcanic Zone ◽  
Volcanic Centre ◽  
Volcanic Zone ◽  
Magma Evolution ◽  
Aotearoa New Zealand ◽  
Basalt Geochemistry ◽  
Rhyolitic Volcanism

The Okataina Volcanic Centre (OVC) is the most recently active rhyolitic volcanic centre in the Taupō Volcanic Zone, Aotearoa New Zealand. Although best known for its high rates of explosive rhyolitic volcanism, there are numerous examples of basaltic to basaltic-andesite contributions to OVC eruptions, ranging from minor involvement of basalt in rhyolitic eruptions to the exclusively basaltic 1886 C.E. Plinian eruption of Tarawera. To explore the basaltic component supplying this dominantly rhyolitic area, we analyse the textures and compositions (minerals and melt inclusions) of four basaltic eruptions within the OVC that have similar whole rock chemistry, namely: Terrace Rd, Rotomakariri, Rotokawau, and Tarawera. Data from these basaltic deposits provide constraints on the conditions of magma evolution and ascent in the crust prior to eruption, revealing that at least five different magma types (two basalts, two dacites, one rhyolite) are sampled during basaltic eruptions. The most abundant basaltic magma type is generated by cooling-induced crystallisation of a common, oxidised, basaltic melt at various depths throughout the crust. The volatile content of this melt was increased by protracted fluid-undersaturated crystallisation. All eruptions display abundant evidence for syn-eruptive mixing of the different magma types. Rotomakariri, consisting of a mafic crystal cargo mixed into a dacitic magma is the most extreme example of this process. Despite similar bulk compositions, comparable to other basaltic deposits in the region, these four OVC eruptions are texturally distinct as a consequence of their wide variation in eruption style.

scholarly journals Supplemental Material: Volcanic plumbing filters on ocean-island basalt geochemistry

2021 ◽  
Author(s):  
Teresa Ubide ◽  
et al.
Keyword(s):  
Ocean Island Basalt ◽  
Ocean Island ◽  
Basalt Geochemistry ◽  
Data Tables ◽  
Island Basalt

Data (Tables S1–S8), methods, and Figures S1–S3.<br>

scholarly journals Investigating ocean island mantle source heterogeneity with boron isotopes in melt inclusions

2019 ◽  
Vol 508 ◽  
pp. 97-108 ◽  
Author(s):  
K.J. Walowski ◽  
L.A. Kirstein ◽  
J.C.M. De Hoog ◽  
T.R. Elliott ◽  
I.P. Savov ◽  
...  
Keyword(s):  
Mantle Source ◽  
Melt Inclusions ◽  
Boron Isotopes ◽  
Ocean Island ◽  
Source Heterogeneity

4D RESERVOIR GEOCHEMISTRY AS AN AID TO INTERPRETING PRODUCTION DYNAMICS, LEGENDRE FIELD, EASTERN DAMPIER SUB-BASIN

2005 ◽  
Vol 45 (1) ◽  
pp. 117 ◽  
Author(s):  
R.C. Davis ◽  
K.R. Leischner ◽  
A.P. Murray ◽  
P.G. Ryles
Keyword(s):  
Gas Chromatography ◽  
Low Cost ◽  
Isotope Analysis ◽  
Development Planning ◽  
Geochemical Data ◽  
Fluid Composition ◽  
Operational Parameters ◽  
Compositional Gradient ◽  
Field Development ◽  
Low Viscosity

Reservoir geochemistry is a low cost, field development/appraisal tool resting on the principle that fluids isolated by flow barriers show slight compositional and/or isotopic differences. Such differences reflect subtle variations in charge history related to the location of the source kitchen and the source rock maturity at the time of expulsion, as well as post fill processes such as water washing and leakage. High resolution gas chromatography (HRGC), multi-dimensional gas chromatography (MDGC) and compound specific liquid and gas isotope analysis (CSIA) were performed on a time series of fluids, comprising stored oil from two drill stem tests, and produced fluids from six points in the Legendre field, Dampier Sub-basin, to investigate changes in fluid composition as production proceeded. The Legendre field contains high gravity (46° API), low viscosity oil, hosted in two culminations (North and South) in a thin, high quality clastic reservoir of Berriasian age. Fluids from different wells within the Northern accumulation are indistinguishable, indicating the oil is in communication and no compositional gradient exists. By contrast, compositional and isotopic differences between fluids from the Northern and Southern accumulations demonstrate that these pools are not in communication, and should therefore be treated separately from a development planning perspective.The differences in initial fluid compositions have been successfully used in conjunction with operational parameters to explain the increase in gas/oil ratio (GOR) of oil from Legendre South–2H that occurred after only 13 months of production. Comparison of pristine, preproduction separator samples with fluids collected after the observed increase in GOR, revealed that solution gas injected at Legendre West–1 has migrated rapidly into the southern part of the field. Integration of geochemical data with regional petroleum system concepts and a full 3D charge model has greatly assisted our understanding of these observations.

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