The effect of cooling rate on immiscible silicate liquid microstructure: an example from the Palaeogene dykes of Northeast England

Honour, Victoria; Holness, Marian B.; Stock, Michael J.

doi:10.1180/mgm.2019.71

Cited by 8 publications

(4 citation statements)

References 61 publications

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“…The size of the Fe-rich droplet near the pseudopillow fracture of the Entablature is so small that it deviates from the range of this regression curve, but extrapolation of the regression curve gives a cooling rate of 642°C/h. It should be noted that the Genbudo lava is a little richer in SiO 2 than the intrusive rocks studied by Honour et al (2019). However, there is no doubt that there was a large contrast in cooling rates at the colonnade-entablature boundary.…”

Section: − 3 Cooling Rate Of Entablaturementioning

confidence: 82%

“…6). Honour et al (2019) observed immiscible Fe-rich droplets in experiments using natural ferrobasalt as starting material, and found that the onset of unmixing is localized due to compositional inhomogeneity in the interstitial melt caused by the compositional boundary layer formed during crystallization. They observed that Fe-rich droplets can distribute adjacent to plagioclase, but Fe-rich droplet free zones are formed around pyroxene and magnetite.…”

Section: − 3 Cooling Rate Of Entablaturementioning

confidence: 99%

“…These suggest that the Fe-rich droplets observed near the pseudopillow fracture were caused by silicate liquid immiscibility. Honour et al (2019) showed that the relationship between the average of the ve largest diameter Fe-rich droplets in basaltic intrusive bodies and the cooling rate calculated by a one-dimensional conduction cooling model can be approximated by a power-law regression curve. According to the relationship, the cooling rate of the colonnade near the colonnade-entablature boundary of the Genbudo lava is estimated to be about 49°C/h (Fig.…”

Section: − 3 Cooling Rate Of Entablaturementioning

confidence: 99%

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Brecciation and fracturing by water ingress into a basaltic andesitic lava flow, Iwate volcano, northeastern Japan

Hoshide,

Ishibashi,

Iwahashi

2023

Preprint

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The Genbudo lava in the southwestern part of Iwate Volcano is a 70 m thick columnar jointed lava flow and divided into three parts from the bottom: the colonnade, the entablature, and the uppermost part. Two main types of fractures develop in the entablature: pseudopillow fractures that develop in a network-like pattern throughout entablature, and sheet fractures with curved surfaces that are nearly parallel to each other. At the uppermost part of the lava flow, finger-like structures of lava extending upward from the coherent lava is distributed, and cogenetic pyroclastic rocks are deposited between the fingers. The occurrence suggests that hyaloclastites generated at the uppermost part. The texture of lava near the pseudopillow fracture of the entablature is commonly hypocrystalline, while the other parts exhibit holocrystalline. There are two types of pyroxene microlites, large prismatic (average size ~ 30 µm) and dendritic (< 10 µm in length) crystals in the lava near the pseudopillow fracture. These suggest that the cooling rate of the lava became greatest in the vicinity of the pseudopillow fractures. Networks of palagonite-filled micro-fractures (less than 10 µm in width) are found in this part, and many bubbles are generated along the fractures. This is irrefutable evidence that the rapid cooling of the lava was caused by water infiltration through the pseudopillow fractures. By the measurement of the Fe-rich droplet sizes due to liquid immiscibility, we could estimate the cooling rates of the colonnade and entablature about 49°C/h and 642°C/h, respectively.

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Section: − 3 Cooling Rate Of Entablaturementioning

confidence: 82%

Section: − 3 Cooling Rate Of Entablaturementioning

confidence: 99%

Section: − 3 Cooling Rate Of Entablaturementioning

confidence: 99%

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Brecciation and fracturing by water ingress into a basaltic andesitic lava flow, Iwate volcano, northeastern Japan

Hoshide,

Ishibashi,

Iwahashi

2023

Preprint

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“…For this study, we review published studies of microstructures in dolerite sills, the prehistoric Makaopuhi lava lake, and the Holyoke flood basalt (Holness et al, 2014;2017a;Holness & Vernon, 2015;Nicoli et al, 2018;Honour et al, 2019), together with newly acquired data from a number of other bodies. Some of the sills under discussion, together with the Makaopuhi lava lake, contain a significant cargo of olivine crystals.…”

Section: Choice Of Samples and Analytical Methodsmentioning

confidence: 99%

The Microstructural Record of Emplacement, Inflation and Convection of Sills, Lava Flows and Lakes

Holness

Neufeld

2022

Journal of Petrology

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The stratigraphic variation of plagioclase grain shape in the marginal regions of tabular bodies of magma provides a record of the balance of heat loss into the surroundings and heat brought into the body by magma flow during inflation and propagation. This record has the potential to constrain the amount of magma flow past any point in a sill, enabling mapping the construction of any extensive sill network. The variation of plagioclase grain shape in lava lakes may preserve a detailed history of lake filling, whereas the history of inflation of a thick ponded flood basalt flow is likely to be lost by melt-back of any early formed chill during prolonged flow at the base. Convection sufficiently vigorous to entrain crystals from the marginal solidification fronts is recorded by stratigraphic invariance of plagioclase grain shape and is not generally found in sills: instead, plagioclase grain shape varies with stratigraphic height, attesting to a predominance of in situ plagioclase nucleation and growth at the intrusion margins. While the stratigraphic variation of plagioclase grain shape in sills thinner than ~100 m is symmetrical, that in thicker sills varies in an asymmetric way with stratigraphic height, suggestive of a slower rate of inwards propagation of the roof solidification front compared to the floor, most likely indicative of moderately vigorous convection. Sills are generally finer-grained than dykes of the same thickness, regardless of whether the spatial variation of plagioclase shape is consistent with convection during solidification: this is likely to be a consequence of a greater extent of Ostwald ripening of suspended grains during long-lived convection in vertically extensive dykes.

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Brecciation and fracturing by water ingress into the Genbudo basaltic andesitic lava flow, Iwate volcano, northeastern Japan

Hoshide,

Ishibashi,

Iwahashi

2024

Bull Volcanol

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The Genbudo lava, the late Pleistocene basaltic-andesitic lava flow in the southwestern part of Iwate Volcano, Japan, is a 70 m thick columnar jointed flow that can be divided into three parts from bottom to top: the colonnade, the entablature, and the partly-brecciated uppermost part. Two main types of fractures developed in the entablature: pseudopillow fractures that formed in a branching network-like pattern throughout the entablature, and sheet fractures with curved surfaces that are nearly parallel to each other. At the uppermost part of the flow, finger-like structures of lava extend upward from the coherent lava, and cogenetic autoclastic rocks form between the fingers. This occurrence suggests that hyaloclastites were generated during emplacement in the uppermost part of the flow, apparently when water from a dammed river valley covered the flow. The texture of the lava near the pseudopillow fractures in the entablature is commonly hypocrystalline, while the texture in other parts is holocrystalline. There are two types of pyroxene microlites, large prismatic (average size ~ 30 µm) and dendritic (< 10 µm in length) crystals in the lava near the pseudopillow fractures. These suggest that the cooling rate of the lava was greatest in the vicinity of the pseudopillow fractures. Networks of palagonite-filled micro-fractures (less than 10 µm in width) are found in this part of the flow, and many bubbles are observed along the fractures. This is clear evidence that the rapid cooling of the lava was caused by water infiltration through the pseudopillow fractures. From the measurement of Fe-rich droplet sizes that formed due to liquid immiscibility within the lava, we estimate the cooling rate within the colonnade as about 49 °C/h and within the entablature as 642 °C/h, consistent with much more rapid cooling by water infiltration from above.

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The effect of cooling rate on immiscible silicate liquid microstructure: an example from the Palaeogene dykes of Northeast England

Cited by 8 publications

References 61 publications

Brecciation and fracturing by water ingress into a basaltic andesitic lava flow, Iwate volcano, northeastern Japan

Brecciation and fracturing by water ingress into a basaltic andesitic lava flow, Iwate volcano, northeastern Japan

The Microstructural Record of Emplacement, Inflation and Convection of Sills, Lava Flows and Lakes

Brecciation and fracturing by water ingress into the Genbudo basaltic andesitic lava flow, Iwate volcano, northeastern Japan

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