scholarly journals Accumulation of magnetite by flotation on bubbles during decompression of silicate magma

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Jaayke L. Knipping ◽  
James D. Webster ◽  
Adam C. Simon ◽  
François Holtz
Keyword(s):  
Silicate Magma

Re-evaluation of magma compositions and processes in the uppermost Critical Zone of the Bushveld Complex

1996 ◽  
Vol 60 (398) ◽  
pp. 131-148 ◽  
Author(s):  
R. Grant Cawthorn
Keyword(s):  
Bushveld Complex ◽  
Hanging Wall ◽  
Experimental Studies ◽  
Critical Zone ◽  
Element Abundances ◽  
Merensky Reef ◽  
Low Viscosity ◽  
Silicate Magma ◽  
Geochemical Study ◽  
Restricted Mobility

AbstractA detailed geochemical study is presented of the uppermost Critical Zone, especially of the footwall and hanging wall to the Merensky Reef, at Impala Platinum Mines in the Bushveld Complex. The approximately 100 m-thick sequence below the Merensky Reef consists of 13 distinct layers which have sharp boundaries. They are adcumulates with varying proportions of cumulus plagioclase, orthopyroxene and chromite.Experimental studies on the composition of coexisting orthopyroxene liquid indicate that the magma which produced this sequence contained between 4 and 6% MgO. The magma from which the Merensky Reef formed was more evolved than the footwall magma.Significant variations exist for both the En content of orthopyroxene and mg# number of whole-rock analyses in short vertical sections. Pyroxenite and norite always have higher values than anorthosite. Extremely sharp breaks in these values correlate with changes in modal proportions, and argue against both significant fractionation within the studied interval, and infiltration metasomatism. Quantitative modelling shows that the entire footwall section could have contained pyroxene with a uniform primary composition of En82, and that all the variation now observed reflects the effect of reaction with trapped magma.Two independent methods for determining the proportion of trapped liquid are presented, based on mg# number and incompatible element abundances. Both yield a uniform proportion in all samples of approximately 10%. Immiscible sulphide liquid from the Merensky Reef can be shown to have infiltrated downwards for <5 m, despite its high density contrast with silicate magma, very low viscosity and low crystallization temperature. Residual silicate magma would have had even more restricted mobility. The migration of residual liquid or fluid through pothole structures in the floor of the Merensky Reef is not supported by the present data.

Unravelling carbonatite–silicate magma interaction dynamics: A case study from the Velay province (Massif Central, France)

Lithos ◽  
2010 ◽  
Vol 116 (1-2) ◽  
pp. 53-64 ◽  
Author(s):  
Luca Valentini ◽  
Kathryn Ruth Moore ◽  
Gilles Chazot
Keyword(s):  
Massif Central ◽  
Interaction Dynamics ◽  
Silicate Magma

Geochemical temporal evolution of Brava Island magmatism: Constraints on the variability of Cape Verde mantle sources and on carbonatite–silicate magma link

2012 ◽  
Vol 334 ◽  
pp. 44-61 ◽  
Author(s):  
Cyntia Mourão ◽  
João Mata ◽  
Régis Doucelance ◽  
José Madeira ◽  
Marc-Alban Millet ◽  
...  
Keyword(s):  
Temporal Evolution ◽  
Cape Verde ◽  
Silicate Magma ◽  
Mantle Sources

scholarly journals Io’s Volcanos: Latest Results from Galileo and from the Earth

2002 ◽  
Vol 12 ◽  
pp. 611-613
Author(s):  
John Spencer
Keyword(s):  
Hubble Space Telescope ◽  
Lava Flows ◽  
Space Telescope ◽  
The Earth ◽  
Silicate Magma ◽  
Magma Compositions

AbstractThree recent close flybys of Io by the Galileo spacecraft, and new observations from the Hubble Space Telescope and ground-based telescopes, have greatly advanced our understanding of Jupiter’s volcanic moon Io. Io’s volcanos are much hotter than previously suspected, perhaps requiring exotic silicate magma compositions. Despite much new data, Io’s largest volcano, Loki, is still poorly understood. New data on Io’s plumes suggest the existence of two types of plumes: primary plumes, relatively rich in S2gas, which are emitted where magma first reaches the surface, and secondary plumes, more SO2rich, which result from interaction of lava flows with a volatile-rich substrate.

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