Magma flow regimes in sills deduced from Ar isotope systematics of host rocks

Scaled analogue experiments were conducted to explore the effect of magma flow regimes, characterised by the Reynolds number (Re), on the transit of magma through the lithosphere via fractures. An elastic, transparent gelatine solid (the crust analogue) was injected by a fluid (magma analogue) to create a thin, vertical, and penny-shaped crack that is analogous to a magma-filled crack (dyke). A vertical laser sheet fluoresced passive-tracer particles suspended in the injected fluid, and particle image velocity (PIV) was used to map the location, magnitude, and direction of flow within the growing dyke from its inception to its surface rupture. Experiments were conducted using water, hydroxyethyl cellulose (HEC) or xanthan gum (XG) as the magma analogue. The results suggest that Re has significant impact on the direction of fluid flow within propagating dykes: Re > 0.1 (jet-flow) is characterised by a rapid central rising fluid jet and downflow at the dyke margin, whereas Re < 0.1 (creeping flow) is characterised by broadly uniform velocities across the dyke plane. Re may be underestimated by up to two orders of magnitude if tip velocity rather than internal fluid velocity is used. In nature, these different flow regimes would affect the petrological, geochemical, geophysical, and geodetic measurements of magma movement, key information upon which reconstructions of volcanic plumbing system architectures and their growth are based.

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Geochemical characteristics and lead isotope systematics of highly fractionated Li–F-enriched amazonite granites and related host rocks of the Orlovka–Spokoinoe mining district, Eastern Transbaikalia (Russia)

Applied Earth Science ◽

10.1179/037174504225004420 ◽

2004 ◽

Vol 113 (1) ◽

pp. 83-99 ◽

Cited By ~ 6

Author(s):

Alla Dolgopolova ◽

Reimar Seltmann ◽

Bernd Kober ◽

Dominik Weiss ◽

Chris Stanley ◽

...

Keyword(s):

Lead Isotope ◽

Geochemical Characteristics ◽

Mining District ◽

Eastern Transbaikalia ◽

Host Rocks ◽

Isotope Systematics

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The age and origin of the North Shore Plutons in the Rae Province, Goldfields area, Saskatchewan

Canadian Journal of Earth Sciences ◽

10.1139/e94-123 ◽

1994 ◽

Vol 31 (9) ◽

pp. 1397-1406 ◽

Cited By ~ 5

Author(s):

David S. O'Hanley ◽

T. Kurtis Kyser ◽

Thomas I. I. Sibbald

Keyword(s):

Detrital Zircons ◽

Nd Isotope ◽

Metasedimentary Rocks ◽

North Shore ◽

The North ◽

Evaporation Technique ◽

Single Zircon ◽

Archean Crust ◽

Host Rocks ◽

Isotope Systematics

The North Shore Plutons are peraluminous granitoids emplaced within the Murmac Bay Group supracrustals exposed on the north shore of Lake Athabasca, Saskatchewan. 207Pb/206Pb ages obtained using the single-zircon Pb-evaporation technique indicate emplacement at 1952 ± 18 Ma, coeval with Taltson magmatism that occurred during the 1.9–2.0 Ga Thelon orogeny, which influenced the Rae Province. The granitoids inherited zircons from Archean source terranes dated at approximately 2.5 and 3.0 Ga. Detrital zircons from the younger source terrane were also identified in the Murmac Bay Group, thus constraining the maximum age of the group to the Paleoproterozoic.Rare earth element and incompatible element data and Rb–Sr and Sm–Nd isotope systematics from the North Shore Plutons and adjacent host rocks indicate that the plutons are crustal melts generated from melting of Murmac Bay Group rocks and Archean crust at deeper levels. Granitic gneisses described as "Older" Granites represent mixtures of variable amounts of magmatic fluids similar to those that formed the North Shore plutons and the Murmac Bay Group metasedimentary rocks.

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Emplacement and Segment Geometry of Large, High-Viscosity Magmatic Sheets

Minerals ◽

10.3390/min11101113 ◽

2021 ◽

Vol 11 (10) ◽

pp. 1113

Author(s):

Tobias Schmiedel ◽

Steffi Burchardt ◽

Tobias Mattsson ◽

Frank Guldstrand ◽

Olivier Galland ◽

...

Keyword(s):

Microstructural Analysis ◽

High Viscosity ◽

Igneous Petrology ◽

Magma Flow ◽

Great Dyke ◽

Low Viscosity ◽

Data Compilation ◽

Current Usage ◽

Depth Study ◽

Host Rocks

Understanding magma transport in sheet intrusions is crucial to interpreting volcanic unrest. Studies of dyke emplacement and geometry focus predominantly on low-viscosity, mafic dykes. Here, we present an in-depth study of two high-viscosity dykes (106 Pa·s) in the Chachahuén volcano, Argentina, the Great Dyke and the Sosa Dyke. To quantify dyke geometries, magma flow indicators, and magma viscosity, we combine photogrammetry, microstructural analysis, igneous petrology, Fourier-Transform-Infrared-Spectroscopy, and Anisotropy of Magnetic Susceptibility (AMS). Our results show that the dykes consist of 3 to 8 mappable segments up to 2 km long. Segments often end in a bifurcation, and segment tips are predominantly oval, but elliptical tips occur in the outermost segments of the Great Dyke. Furthermore, variations in host rocks have no observable impact on dyke geometry. AMS fabrics and other flow indicators in the Sosa Dyke show lateral magma flow in contrast to the vertical flow suggested by the segment geometries. A comparison with segment geometries of low-viscosity dykes shows that our high-viscosity dykes follow the same geometrical trend. In fact, the data compilation supports that dyke segment and tip geometries reflect different stages in dyke emplacement, questioning the current usage for final sheet geometries as proxies for emplacement mechanism.

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