Transmission electron microscopy applied to fluid inclusion investigations

Viti, Cecilia; Frezzotti, Maria Luce

doi:10.1016/s0024-4937(00)00042-6

Cited by 49 publications

(13 citation statements)

References 11 publications

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“…A rectangular-shaped void, $60 nm in length, is present in the upper right corner of the view and is shown enlarged on the right. This feature is consistent in both size and shape to negative crystals imaged by TEM (Viti and Frezzotti, 2001). (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this paper.)…”

Section: 'Posterboy' Section 2 and 'Texas' Sections 1 Andsupporting

confidence: 78%

Origins of magnetite nanocrystals in Martian meteorite ALH84001

Thomas‐Keprta

Clemett

McKay

et al. 2009

Geochimica et Cosmochimica Acta

108

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The Martian meteorite ALH84001 preserves evidence of interaction with aqueous fluids while on Mars in the form of microscopic carbonate disks. These carbonate disks are believed to have precipitated 3.9 Ga ago at beginning of the Noachian epoch on Mars during which both the oldest extant Martian surfaces were formed, and perhaps the earliest global oceans. Intimately associated within and throughout these carbonate disks are nanocrystal magnetites (Fe 3 O 4 ) with unusual chemical and physical properties, whose origins have become the source of considerable debate. One group of hypotheses argues that these magnetites are the product of partial thermal decomposition of the host carbonate. Alternatively, the origins of magnetite and carbonate may be unrelated; that is, from the perspective of the carbonate the magnetite is allochthonous. For example, the magnetites might have already been present in the aqueous fluids from which the carbonates were believed to have been deposited. We have sought to resolve between these hypotheses through the detailed characterization of the compositional and structural relationships of the carbonate disks and associated magnetites with the orthopyroxene matrix in which they are embedded. Extensive use of focused ion beam milling techniques has been utilized for sample preparation. We then compared our observations with those from experimental thermal decomposition studies of sideritic carbonates under a range of plausible geological heating scenarios. We conclude that the vast majority of the nanocrystal magnetites present in the carbonate disks could not have formed by any of the currently proposed thermal decomposition scenarios. Instead, we find there is considerable evidence in support of an alternative allochthonous origin for the magnetite unrelated to any shock or thermal processing of the carbonates.

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Section: 'Posterboy' Section 2 and 'Texas' Sections 1 Andsupporting

confidence: 78%

Origins of magnetite nanocrystals in Martian meteorite ALH84001

Thomas‐Keprta

Clemett

McKay

et al. 2009

Geochimica et Cosmochimica Acta

108

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“…The consequent result is the appearance of liquid bubbles just as shown in figure 1(b) and (c). This is in good favor of the assumption that the formation of negative crystal may be related to the liquid inclusions [14,15].…”

Section: Resultsmentioning

confidence: 99%

Experimental study of bubble generation during β‐BaB₂O₄ single crystal growth

Pan

Jin

et al. 2007

Cryst. Res. Technol.

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The generation of bubble-inclusions during BaB 2 O 4 (BBO) crystal growth from high temperature solution has been optically observed by an in situ observation technique. It was found that bubbles are formed from the peripheries of some hexagonal defects in the (0001) plane of the growing crystal, which may be caused by the evaporation of the air-opened interface at the high temperature. In addition, atomic force microscope (AFM) was used to investigate the distribution of bubbles. Results revealed that the bubble generation and distribution depend strongly on the microscopic structure of the interface: on a rough interface, bubbles are easily formed and grow rapidly; however, they are greatly suppressed by step trains on a vicinal interface. In the latter case, the height value of a bubble is close to that of the step, which is in the order of several tens of nanometers.

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“…Qin et al 1992;Portnyagin et al 2008;Bucholz et al 2013;Hartley et al 2015), volatile behaviour in plagioclase-hosted melt inclusions is less well understood. Whilst the high H 2 O content of melt inclusions precludes CO 2 loss during the final stages of eruption, it is not currently possible to evaluate how CO 2 may be transferred between inclusions and the external melt through plagioclase hosts, though diffusion along lattice defects and cleavage planes is likely to play a role (Viti and Frezzotti 2001;Kress and Ghiorso 2004). Nevertheless, once experimentally quantified, volatile exchange through plagioclase macrocrysts has the chronometric potential to reveal rates of immediately pre-eruptive processes.…”

Section: Magma Storage Depths and Barometric Inconsistenciesmentioning

confidence: 99%

The evolution and storage of primitive melts in the Eastern Volcanic Zone of Iceland: the 10 ka Grímsvötn tephra series (i.e. the Saksunarvatn ash)

Neave

Maclennan

Thordarson

et al. 2015

Contrib Mineral Petrol

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evolved assemblage is close to being in equilibrium with the matrix glass, trace element disequilibrium between primitive and evolved assemblages indicates that they were derived from different distributions of mantle melt compositions. Juxtaposition of disequilibrium assemblages probably occurred during disaggregation of incompatible trace element-depleted mushes (mean La/Yb melt = 2.1) into aphyric and incompatible trace element-enriched liquids (La/Yb melt = 3.6) shortly before the growth of the evolved macrocryst assemblage. Post-entrapment modification of plagioclase-hosted melt inclusions has been minimal and high-Mg# inclusions record differentiation and mixing of compositionally variable mantle melts that are amongst the most primitive liquids known from the EVZ. Coupled highfield strength element (HFSE) depletion and incompatible trace element enrichment in a subset of primitive plagioclase-hosted melt inclusions can be accounted for by inclusion formation following plagioclase dissolution driven by interaction with plagioclase-undersaturated melts. Thermobarometric calculations indicate that final crystal-melt equilibration within the evolved assemblage occurred at ~1140 °C and 0.0-1.5 kbar. Considering the large volume of the erupted tephra and textural evidence for rapid crystallisation of the evolved assemblage, 0.0-1.5 kbar is considered unlikely to represent a pressure of long-term magma accumulation and storage. Multiple thermometers indicate that the primitive assemblage crystallised at high temperatures of 1240-1300 °C. Different barometers, however, return markedly different crystallisation depth estimates. Raw clinopyroxene-melt pressures of 5.5-7.5 kbar conflict with apparent melt inclusion entrapment pressures of 1.4 kbar. After applying a correction derived from published experimental data, clinopyroxene-melt equilibria return mid-crustal pressures of 4 ± 1.5 kbar, which are consistent with pressures estimated from the major element Abstract Major, trace and volatile elements were measured in a suite of primitive macrocrysts and melt inclusions from the thickest layer of the 10 ka Grímsvötn tephra series (i.e. Saksunarvatn ash) at Lake Hvítárvatn in central Iceland. In the absence of primitive tholeiitic eruptions (MgO > 7 wt%) within the Eastern Volcanic Zone (EVZ) of Iceland, these crystal and inclusion compositions provide an important insight into magmatic processes in this volcanically productive region. Matrix glass compositions show strong similarities with glass compositions from the AD 1783-1784 Laki eruption, confirming the affinity of the tephra series with the Grímsvötn volcanic system. content of primitive melt inclusions. Long-term storage of primitive magmas in the mid-crust implies that low CO 2 concentrations measured in primitive plagioclase-hosted inclusions (262-800 ppm) result from post-entrapment CO 2 loss during transport through the shallow crust. In order to reconstruct basaltic plumbing system geometries from petrological data with greater confidence, mineral-mel...

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Transmission electron microscopy applied to fluid inclusion investigations

Cited by 49 publications

References 11 publications

Origins of magnetite nanocrystals in Martian meteorite ALH84001

Origins of magnetite nanocrystals in Martian meteorite ALH84001

Experimental study of bubble generation during β‐BaB₂O₄ single crystal growth

The evolution and storage of primitive melts in the Eastern Volcanic Zone of Iceland: the 10 ka Grímsvötn tephra series (i.e. the Saksunarvatn ash)

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Transmission electron microscopy applied to fluid inclusion investigations

Cited by 49 publications

References 11 publications

Origins of magnetite nanocrystals in Martian meteorite ALH84001

Origins of magnetite nanocrystals in Martian meteorite ALH84001

Experimental study of bubble generation during β‐BaB2O4 single crystal growth

The evolution and storage of primitive melts in the Eastern Volcanic Zone of Iceland: the 10 ka Grímsvötn tephra series (i.e. the Saksunarvatn ash)

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Experimental study of bubble generation during β‐BaB₂O₄ single crystal growth