Segregation Vesicles, Gas Filter-Pressing, and Igneous Differentiation

Anderson, A. T.; Swihart, George H.; Artioli, Gilberto; Geiger, Charles A.

doi:10.1086/628834

Cited by 150 publications

(84 citation statements)

References 16 publications

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“…We interpret the silicate caps as the result of fractionated interstitial silicate melt being driven into residual porosity during late stages of solidification and crystal overgrowth of the primocrysts by the gas-filter pressing mechanism (20), which has also been invoked to explain the occurrence of segregation vesicles in basalts. In this mechanism, crystallization of the intercumulus residual melt causes nucleation and growth of numerous These maps were produced using the data collected with the Maia detector array on the XRF microscopy beamline, at the Australian Synchrotron in Melbourne.…”

Section: Capped Globular Sulfidesmentioning

confidence: 90%

Role of degassing of the Noril’sk nickel deposits in the Permian–Triassic mass extinction event

Vaillant

Mungall

2017

Proc. Natl. Acad. Sci. U.S.A.

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The largest mass extinction event in Earth's history marks the boundary between the Permian and Triassic Periods at circa 252 Ma and has been linked with the eruption of the basaltic Siberian Traps large igneous province (SLIP). One of the kill mechanisms that has been suggested is a biogenic methane burst triggered by the release of vast amounts of nickel into the atmosphere. A proposed Ni source lies within the huge Noril’sk nickel ore deposits, which formed in magmatic conduits widely believed to have fed the eruption of the SLIP basalts. However, nickel is a nonvolatile element, assumed to be largely sequestered at depth in dense sulfide liquids that formed the orebodies, preventing its release into the atmosphere and oceans. Flotation of sulfide liquid droplets by surface attachment to gas bubbles has been suggested as a mechanism to overcome this problem and allow introduction of Ni into the atmosphere during eruption of the SLIP lavas. Here we use 2D and 3D X-ray imagery on Noril’sk nickel sulfide, combined with simple thermodynamic models, to show that the Noril’sk ores were degassing while they were forming. Consequent “bubble riding” by sulfide droplets, followed by degassing of the shallow, sulfide-saturated, and exceptionally volatile and Cl-rich SLIP lavas, permitted a massive release of nickel-rich volcanic gas and subsequent global dispersal of nickel released from this gas as aerosol particles.

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Section: Capped Globular Sulfidesmentioning

confidence: 90%

Role of degassing of the Noril’sk nickel deposits in the Permian–Triassic mass extinction event

Vaillant

Mungall

2017

Proc. Natl. Acad. Sci. U.S.A.

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“…Such a process of retrograde or secondary boiling is a common consequence of crystallization-dominated differentiation of magmas (Sisson and Bacon, 1999). The exsolution of gas can trigger gas-driven filter pressing, causing an effective separation of melts from crystals (Anderson et al, 1984). Sisson and Bacon (1999) have shown that gas-driven filter pressing occurs in vapor saturated silicic magmas at depth Ͻ10 km.…”

Section: Petrogenetic Modelmentioning

confidence: 99%

Crystallization history of rhyolites at Long Valley, California, inferred from combined U-series and Rb-Sr isotope systematics

Heumann

Davies

Elliott

2002

Geochimica et Cosmochimica Acta

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Abstract-In this study, we present 87 Rb/ 86 Sr and 230 Th/ 238 U isotope analyses of glasses and phenocrysts from postcaldera rhyolites erupted between 150 to 100 ka from the Long Valley magmatic system. Both isotope systems indicate complex magma evolution with preeruptive mineral crystallization and magma fractionation, followed by extended storage in a silicic magma reservoir. Glass analyses yield a Rb-Sr isochron of 257 Ϯ 39 ka, which can be explained by a feldspar-fractionation event ϳ150 ky before eruption. Individual feldspar-glass pairs confirm this age result. A mineral 230 Th-238 U isochron in a low-silica rhyolite from the Deer Mountain Dome defines an age of 236 Ϯ 1 ka, but the glass and whole rock do not lie on the isochron. U-Th fractionation of the rocks is controlled by the accessory minerals zircon and probably allanite, which crystallized at 250 Ϯ 3 ka and 187 Ϯ 9 ka, respectively. All major mineral phases contain accessory mineral phases; therefore, the mineral isochron represents a mixture of zircon and allanite populations. A precision of Ϯ1 ka for the mixing array implies that the minor phases must have crystallized within this timescale. Longer periods of crystal growth would cause the mixing array to be less well defined. U-series data from other lowand high-silica rhyolites indicate younger accessory mineral crystallization events at ϳ200 and 140 ka, probably related to the thermal evolution of the magma reservoir. These crystallization events are, however, only documented by the accessory minerals and had no further influence on bulk magma compositions. We interpret the indistinguishable age results from both isotope systems (ϳ250 ka) to record the fractionation of small magma batches by filter pressing from a much larger underlying magma volume, followed by physical isolation and extended storage at the top of the magma reservoir for up to 150 ky.

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“…The abundance of clinopyroxene, the scarcity of olivine, and the absence of spinel as phenocryst are unusual for MORBs and suggest evolved magmas. The evolved nature of the magma is also suggested by the occurrence of segregation vesicles (Anderson et al, 1984;Sato, 1978). The segregated magma is of Fe-Ti basalt composition, and is now composed of quench crystals of ilmenite, Fe-Ti augite, and plagioclase (Plate l, Fig.…”

Section: Petrographic Characteristics Of the Basaltic Rocksmentioning

confidence: 96%

Petrology, Geochemistry, and Mineralogy of the Early Cretaceous Evolved N-MORB from Sites 765 and 766, Eastern Indian Ocean

Ishiwatari¹

1992

Proceedings of the Ocean Drilling Program

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The Early Cretaceous basaltic rocks obtained from Sites 765 and 766 in the eastern Indian Ocean floor were mostly iron-rich normal mid-ocean ridge basalts (N-MORB), which were derived from a depleted mantle source having strongly light rare earth element (LREE)-depleted rare-earth patterns and a high titanium/zirconium (Ti/Zr) ratio. Basaltic rocks in the upper part of the Site 765 basement section include megacrysts and gabbroic fragments of widely varying mineral chemistry. These megacrysts range from An 90 plagioclase, including highly magnesian basaltic glass coexisting with augite of Mg# (= 100 Mg/[Fe+Mg]) at 85, to An 50 plagioclase coexisting with hypersthene. This varying mineralogy of megacrysts and gabbroic fragments indicates that a considerable degree of fractional crystallization took place in the magma chamber. The unusual negative correlation between incompatible elements (e.g., TiO 2 ) and FeO*/MgO observed among Site 765 basement basalts and fresh volcanic glasses suggest source-mantle heterogeneity in terms of FeO*/MgO. Strontium isotope ratios ( 87 Sr/ 86 Sr) of the basaltic rocks from both sites are between 0.7027 and 0.7033 and are comparable to those of mid-Indian Ocean ridge basalts (MIORB).The basalt pebbles encountered in the sedimentary section may have been transported from the basement highs nearer the Australian continent and include basaltic compositions ranging from primitive N-MORBs to evolved enriched(E)-MORBs. Their mantle source was not as depleted as that of the basement basalts. These rocks may be the products of earlier volcanism that took place during the rifting of the Australian continent.

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Segregation Vesicles, Gas Filter-Pressing, and Igneous Differentiation

Cited by 150 publications

References 16 publications

Role of degassing of the Noril’sk nickel deposits in the Permian–Triassic mass extinction event

Role of degassing of the Noril’sk nickel deposits in the Permian–Triassic mass extinction event

Crystallization history of rhyolites at Long Valley, California, inferred from combined U-series and Rb-Sr isotope systematics

Petrology, Geochemistry, and Mineralogy of the Early Cretaceous Evolved N-MORB from Sites 765 and 766, Eastern Indian Ocean

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