Composition and Crystallization Temperatures of Primary Melts from Hole 896A Basalts: Evidence from Melt Inclusion Studies

McNeill, Andrew W.; Danyushevsky, L. V.

doi:10.2973/odp.proc.sr.148.106.1996

Cited by 13 publications

(12 citation statements)

References 33 publications

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“…The criteria outlined above are satisfied by MORB samples from ODP Hole 896A (McNeill and Danyushevsky, 1996). Samples from this hole underwent no plagioclase accumulation (Fig.…”

Section: Some Examples Of Poorly Understood Reequilibration Processesmentioning

confidence: 83%

“…8. Compositions of pillow-rim glasses from ODP Hole 896A (McNeill and Danyushevsky, 1996). Glasses from samples used in the melt inclusion study are identified on the lower plot.…”

Section: Some Examples Of Poorly Understood Reequilibration Processesmentioning

confidence: 99%

“…However, it is important to consider if the studied melt inclusion compositions are representative of the melt composition at the time of trapping. We can address this problem by studying melt inclusions with compositions within the range covered by pillow-rim glasses (McNeill and Danyushevsky, 1996). In a suitable suite of samples, the compositions of pillow-rim glasses must form a well-defined liquid line of descent (to enable comparison with melt inclusion compositions), and the samples must not have undergone extensive plagioclase accumulation.…”

Section: Some Examples Of Poorly Understood Reequilibration Processesmentioning

confidence: 99%

“…9) and yielded homogenisation temperatures in the range 1195 -1215°C (see McNeill andDanyushevsky, 1996 andMcNeill, 1997 for a detailed description of experimental procedures and results). As the H 2 O contents of these glasses are known (McNeill and Danyushevsky, 1996), their crystallisation temperature can be accurately estimated assuming olivine and plagioclase saturation (Danyushevsky, in press). Calculated olivine-and plagioclase-melt equilibrium temperatures, for the most evolved and most primitive glasses range from 1182 to 1213°C and from 1179 to 1217°C, respectively, consistent with the range of experimental homogenisation temperatures.…”

Section: Some Examples Of Poorly Understood Reequilibration Processesmentioning

confidence: 99%

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Experimental and petrological studies of melt inclusions in phenocrysts from mantle-derived magmas: an overview of techniques, advantages and complications

2002

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Melt inclusions in phenocrysts are a potentially powerful tool in petrological research that can provide the only direct information available on the physical parameters ( P, T and melt composition) of crystallisation at various stages in the evolution of magmatic systems. However, melt inclusions also differ in principle from other parts of the magmatic system in that their composition, after trapping, may be controlled by the composition of the host phenocryst and therefore the direct application of our understanding of macro-scale magmatic processes to the interpretation of melt inclusion data can lead to erroneous conclusions. Our results indicate that the compositions of melt inclusions in early formed phenocrysts (olivine, pyroxene, plagioclase and spinel), often of most interest in petrological studies, can be affected by processes such as volatile dissociation, oxidation and/or partial re-equilibration with their host, both during natural cooling and homogenisation experiments. In particular, melt inclusions in all minerals are prone to hydrogen diffusion into or out of the inclusions after trapping and prior to eruption, and during homogenisation experiments. If not taken into account, this can significantly affect the crystallisation temperatures derived from the homogenisation experiments. Melt inclusions in highmagnesian olivine phenocrysts commonly have lower Fe contents compared to the initially trapped composition due to reequilibration with the host at lower temperatures. This often leads to the appearance of sulphide globules and in some cases high-magnesian clinopyroxene daughter crystals, and may cause an increase in the oxidation state of the inclusions. Homogenised melt inclusions in plagioclase phenocrysts in MORB usually have lower Ti and Fe, and higher Si contents compared to the melt composition at the moment of trapping. However, homogenisation experiments can provide reliable estimates of trapping temperature and the MgO, Al 2 O 3 , CaO, Na 2 O, and K 2 O contents of the host magma at the moment of trapping. Some of these processes can be identified by observing the behaviour of melt inclusions during homogenisation experiments using low-inertia visually controlled heating stages, and their effects can be minimised by using appropriate experimental conditions as determined by kinetic experiments, ideally completed for each phenocryst type in every sample. We also discuss general aspects of melt inclusion studies aimed at recovering H 2 O content of primary mantle-derived magmas and demonstrate that, in cases of low-pressure crystallisation, it is important to identify the 0009-2541/02/$ -see front matter D 2002 Elsevier Science B.V. All rights reserved. PII: S 0 0 0 9 -2 5 4 1 ( 0 1 ) 0 0 3 6 9 -2

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“…The criteria outlined above are satisfied by MORB samples from ODP Hole 896A (McNeill and Danyushevsky, 1996). Samples from this hole underwent no plagioclase accumulation (Fig.…”

Section: Some Examples Of Poorly Understood Reequilibration Processesmentioning

confidence: 83%

“…8. Compositions of pillow-rim glasses from ODP Hole 896A (McNeill and Danyushevsky, 1996). Glasses from samples used in the melt inclusion study are identified on the lower plot.…”

Section: Some Examples Of Poorly Understood Reequilibration Processesmentioning

confidence: 99%

Section: Some Examples Of Poorly Understood Reequilibration Processesmentioning

confidence: 99%

Section: Some Examples Of Poorly Understood Reequilibration Processesmentioning

confidence: 99%

See 2 more Smart Citations

Experimental and petrological studies of melt inclusions in phenocrysts from mantle-derived magmas: an overview of techniques, advantages and complications

2002

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“…Half of these samples come from a section of the Mid-Atlantic Ridge that was affected by Azores magmatism (enriched MORB samples in Table 2 of Green et al [2001]), and these are not representative of normal MORB [e.g., Langmuir et al, 1992]. Two samples with high FeO contents from Ocean Drilling Prograpm Site 896, east of the both the Galapagos archipelago and the Galapagos Rift, contain olivines with Fo 91.6 [McNeill and Danyushevsky, 1996]; these are samples 148-896A-27R-1,15 and 148-896A-3R-1,4 and, although they might have been influenced by the Galapagos plume, we initially consider these as NMORB. Two other samples come from a normal ridge.…”

Section: Morbmentioning

confidence: 99%

Temperatures in ambient mantle and plumes: Constraints from basalts, picrites, and komatiites

Herzberg

Asimow

Arndt

et al. 2007

Geochem Geophys Geosyst

639

449

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International audienceSeveral methods have been developed to assess the thermal state of the mantle below oceanic ridges, islands, and plateaus, on the basis of the petrology and geochemistry of erupted lavas. One leads to the conclusion that mantle potential temperature (i.e., TP) of ambient mantle below oceanic ridges is 1430°C, the same as Hawaii. Another has ridges with a large range in ambient mantle potential temperature (i.e., TP = 1300–1570°C), comparable in some cases to hot spots (Klein and Langmuir, 1987; Langmuir et al., 1992). A third has uniformly low temperatures for ambient mantle below ridges, ∼1300°C, with localized 250°C anomalies associated with mantle plumes. All methods involve assumptions and uncertainties that we critically evaluate. A new evaluation is made of parental magma compositions that would crystallize olivines with the maximum forsterite contents observed in lava flows. These are generally in good agreement with primary magma compositions calculated using the mass balance method of Herzberg and O'Hara (2002), and differences reflect the well-known effects of fractional crystallization. Results of primary magma compositions we obtain for mid-ocean ridge basalts and various oceanic islands and plateaus generally favor the third type of model but with ambient mantle potential temperatures in the range 1280–1400°C and thermal anomalies that can be 200–300°C above this background. Our results are consistent with the plume model

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The time scales of magma mixing and mingling involving primitive melts and melt–mush interaction at mid-ocean ridges

Costa

Coogan

Chakraborty

2009

Contrib Mineral Petrol

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Composition and Crystallization Temperatures of Primary Melts from Hole 896A Basalts: Evidence from Melt Inclusion Studies

Cited by 13 publications

References 33 publications

Experimental and petrological studies of melt inclusions in phenocrysts from mantle-derived magmas: an overview of techniques, advantages and complications

Experimental and petrological studies of melt inclusions in phenocrysts from mantle-derived magmas: an overview of techniques, advantages and complications

Temperatures in ambient mantle and plumes: Constraints from basalts, picrites, and komatiites

The time scales of magma mixing and mingling involving primitive melts and melt–mush interaction at mid-ocean ridges

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