The dependence of the Fe2+-Mg cation-partitioning between olivine and basaltic liquid on pressure, temperature and composition

1989 ◽  
Vol 101 (3) ◽  
pp. 261-273 ◽  
Author(s):  
Peter Ulmer
Keyword(s):  
Basaltic Liquid

Supercooling and the crystallization of plagioclase from a basaltic magma

1974 ◽  
Vol 39 (306) ◽  
pp. 641-653 ◽  
Author(s):  
Fergus G. F. Gibb
Keyword(s):  
Liquidus Temperature ◽  
Basaltic Magma ◽  
Equilibrium Phase ◽  
Phase Relations ◽  
Lava Flows ◽  
Cooling Rates ◽  
Time Space ◽  
Columbia River Basalt ◽  
Temperature Time ◽  
Basaltic Liquid

SummaryThe liquidus temperature (1198 °C) and equilibrium phase relations of a sample of Columbia River basalt from the Picture Gorge section have been determined at I atmosphere by heating in a controlled atmosphere. When this basalt is cooled from above its liquidus temperature the liquidus phase (plagioclase) may fail to crystallize depending on the degree of undercooling and the duration of the experiment. A field in temperature-time space in which plagioclase fails to crystallize on cooling is separated from another in which plagioclase always crystallizes by a third in which the nucleation of plagioclase is unpredictable in terms of temperature and time. The extent to which this basaltic liquid can be supercooled without the crystallization of plagioclase is independent of the time it is held above the liquidus or the temperature in excess of the liquidus to which it is heated.The exceptionally long times required to ensure the nucleation of plagioclase at or near the liquidus temperature suggest that many so-called ‘equilibrium’ phase relations determined from experiments of a few hours' duration could be in serious error if the ‘equilibration’ involves a nucleation process.It is demonstrated that, over a range of cooling rates, the temperature at which plagioclase begins to crystallize on cooling varies markedly and the temperature and times required for both possible and certain nucleation of plagioclase are calculated for a range of constant cooling rates. The range of cooling rates over which the nucleation temperature of plagioclase varies is likely to occur in nature only in certain lava flows and small minor intrusions. In such cases this could lead to changes in the order in which the minerals appear on cooling and other petrologically significant effects.

Dolerites Associated with the Karroo System, South Africa

1930 ◽  
Vol 67 (3) ◽  
pp. 97-110 ◽  
Author(s):  
Reginald A. Daly ◽  
Tom F. W. Barth
Keyword(s):  
South Africa ◽  
Great Britain ◽  
Fractional Crystallization ◽  
Parental Magma ◽  
Magmatic Differentiation ◽  
Plateau Basalt ◽  
Homogeneous Crystal ◽  
High Degree ◽  
Vast Area ◽  
Basaltic Liquid

Summary—The field impression of a high degree of uniformity in the composition of the intrusive Karroo dolerites over a vast area is confirmed by new chemical and microscopical studies. The pyroxene characteristic of the dolerites is a typical pigeonite, which, however, does not display any twinning on (100). The plagioclase is potash-free, usually a labradorite, but it has been observed that a homogeneous crystal of plagioclase may be in twin position to another homogeneous crystal of a very differently composed plagioclase. The close resemblance of the doleritic liquid to the artificial liquid taken by Bowen to represent basaltic liquid is noted, and his conclusion that pyroxene and feldspar should crystallize simultaneously in natural basaltic liquid is confirmed.Conceivably the doleritic liquid was quite original and not a differentiate of any earlier liquid. However, analogies like those with the tholeiites and similar hypabyssal rocks of Great Britain suggest that in South Africa, as in Great Britain, the liquids of these hypabyssal rocks were derived from the slightly more femic plateau-basalt.On that assumption the question of the mode of differentiation arises. The fractional crystallization of plateau-basalt, as now described by Bowen and other leaders, does not appear competent to explain the abnormally low soda of one of the analyzed dolerites, nor the excess of soda and total alkalies in plateau-basalt respectively over the soda and total alkalies of the Karroo dolerite. Further, the settling-out of early olivine does not explain the excess of (total) FeO in plateau-basalt over the (total) FeO in the Karroo dolerite. The actual relations indicate the need of renewed examination of the theory of magmatic differentiation by crystal-fractionation. In any case many more data are required before it is possible to decide upon the precise relation of the Karroo dolerite to a parental magma. Possibly such additions to knowledge may annul present difficulties in the way of accounting for the composition of the dolerite.

scholarly journals Effects of pH2O, pH2 and fO2 on the diffusion of H-bearing species in lunar basaltic liquid and an iron-free basaltic analog at 1 atm

2019 ◽  
Vol 259 ◽  
pp. 316-343 ◽  
Author(s):  
M.E. Newcombe ◽  
J.R. Beckett ◽  
M.B. Baker ◽  
S. Newman ◽  
Y. Guan ◽  
...  
Keyword(s):  
Basaltic Liquid

scholarly journals Magma mixing enhanced by bubble segregation

2015 ◽  
Vol 7 (2) ◽  
pp. 1469-1515
Author(s):  
S. Wiesmaier ◽  
D. Morgavi ◽  
C. Renggli ◽  
D. Perugini ◽  
C. P. De Campos ◽  
...  
Keyword(s):  
Magma Mixing ◽  
Single Pulse ◽  
Concentration Variance ◽  
Diffusion Analysis ◽  
Rheological Modelling ◽  
Multiple Bubbles ◽  
Analogue Experiments ◽  
Microct Imaging ◽  
First Time ◽  
Basaltic Liquid

Abstract. That rising bubbles may significantly affect magma mixing paths has already been demon strated by analogue experiments. Here, for the first time, bubble-advection experiments are performed employing volcanic melts at magmatic temperatures. Cylinders of basaltic glass were placed below cylinders of rhyolite glass. Upon melting, interstitial air formed bubbles that rose into the rhyolite melt, thereby entraining tails of basaltic liquid. The formation of plume-like filaments of advected basalt within the rhyolite was characterized by microCT and subsequent high-resolution EMP analyses. Melt entrainment by bubble ascent appears to be an efficient mechanism for mingling volcanic melts of highly contrasting compositions and properties. MicroCT imaging reveals bubbles trailing each other and multiple filaments coalescing into bigger ones. Rheological modelling of the filaments yields viscosities of up to 2 orders of magnitude lower than for the surrounding rhyolitic liquid. Such a viscosity contrast implies that bubbles rising successively are likely to follow this pathway of low resistance that previously ascending bubbles have generated. Filaments formed by multiple bubbles would thus experience episodic replenishment with mafic material. Inevitable implications for the concept of bubble advection in magma mixing include thereby both an acceleration of mixing because of decreased viscous resistance for bubbles inside filaments and non-conventional diffusion systematics because of intermittent supply of mafic material (instead of a single pulse) inside a material. Inside the filaments, the mafic material was variably hybridised to andesitic through rhyolitic composition. Compositional profiles alone are ambiguous, however, to determine whether single or multiple bubbles were involved during formation of a filament. Statistical analysis, employing concentration variance as measure of homogenisation, demonstrates that also filaments appearing as single-bubble filaments are likely to have experienced multiple bubbles passages. In cases where bubbles have been essential for magma mixing, standard diffusion analysis may thus be inadequate for constraining timescales. However, data analysis employing concentration variance relaxation permits the distinction of conventional single-pulse filaments from multiple bubble ascent advection in natural samples, demonstrating yet another powerful application of this novel petrological tool.

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