Viscosity of flux-rich pegmatitic melts

Bartels, Alexander; Vetere, Francesco; Holtz, François; Behrens, Harald; Linnen, Robert L.

doi:10.1007/s00410-010-0582-3

Cited by 62 publications

(41 citation statements)

References 31 publications

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“…This observation has important implications for pegmatite petrogenesis; pegmatite-forming melts that remain supersaturated in Li at lower temperatures without any Li-aluminosilicate minerals crystallizing have substantially lower viscosities relative to common granitic melts Dingwell et al 1996;Romano et al 2001;Bartels et al 2011) and can become very mobile, forming Li-rich pegmatites several kilometers away from the parent granite (cf. Baker 1998).…”

Section: Supersaturation Of Li-aluminosilicates In Pegmatite-forming mentioning

confidence: 95%

Evidence for lithium-aluminosilicate supersaturation of pegmatite-forming melts

Maneta

Baker

Minarik

2015

Contrib Mineral Petrol

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Section: Supersaturation Of Li-aluminosilicates In Pegmatite-forming mentioning

confidence: 95%

Evidence for lithium-aluminosilicate supersaturation of pegmatite-forming melts

Maneta

Baker

Minarik

2015

Contrib Mineral Petrol

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“…Generally, the influence of P on the viscosity and water solubility is significantly lower than that of H 2 O, F, B, and alkalis (Johannes and Holtz 1996;Sowerby and Keppler 2002;Bartels et al 2011Bartels et al , 2013 and by itself cannot reduce the viscosity down to values of c. 10 2 Pa.s at 700 °C which are considered to be the threshold values for the separation of residual melt (McKenzie 1985) except at very high concentrations. Although P is often significantly enriched in intergranular melts, and has been considered a possible fluxing element, it appears to be of less importance than F or B. water-and boron-rich melt systems moving in part as supercritical fluid through the parental granite ).…”

Section: Phosphorus Content Of Melt Inclusionsmentioning

confidence: 99%

“…Thus, primary melt and fluid inclusions trapped in magmatic minerals during magma crystallization provide almost the only method of estimating true original melt volatile concentrations. Melt and fluid studies are not without their difficulties, as is the interpretation of their results (for example see Roedder 1984;Lowenstern 1995), but these techniques are very rarely taken into account by the experimental petrologists (e.g., Johannes and Holtz 1996;London 2008;Bartels et al 2011Bartels et al , 2013.…”

Section: Melt Extraction -The Granite-pegmatite Linkmentioning

confidence: 99%

The missing link between granites and granitic pegmatites

Thomas¹,

Davidson²

2013

Jour. Geosci.

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In this contribution we provide evidence for the extraction of volatile and incompatible element enriched melts from common granites. This provides a mechanism showing that at least a large proportion of granitic pegmatites could be genetically directly connected to a main granite body. In granites there are often two principal types of melt inclusions: (i) those that represent the bulk chemistry of the granite and (ii) those with very different compositions. In the Variscan Erzgebirge granites, the second type is characterized by the abundance of fluorine. However, in other geodynamic settings inclusions in granites can contain high concentrations of other elements which may take over the function of fluorine. From textural relationships the second inclusion type represents intergranular melts enriched in all elements incompatible with the ideal haplogranite system. Due to the high volatile content of such melts, the viscosity can be several orders of magnitude lower than the quasi-solid bulk system and can therefore move rapidly through the partially or totally crystallized host, and flow together into a separate system forming pegmatite bodies inside or outside the granite body. Another important effect of the high volatile content is the phase separation resulting from the speciation changes OH -→ H 2 O or CO 3 2-→ CO 2 due to temperature and/or pressure changes at different locations within the granite-intergranular melt system. Since melt inclusions provide a means of conserving original un-degassed compositions, they yield important evidence for closing the gap between granites and granitic pegmatites. The paper is dedicated to two Czech colleagues -Petr Černý and Milan Novák -who have devoted their lives to the study of granitic pegmatites.

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“…Network-forming cations (Al and Si) and U, Th, REE and other HFSE would diffuse during viscous stress relaxation in melts, which typically occurs with the addition of volatiles (e.g., Bagdassarov et al 1993;Mungall 2002). Experimental studies of volatile-rich pegmatite melts (Bartels et al 2011(Bartels et al , 2012 have also shown the effectiveness of the of U, Th, and REE diffusion related to the changes in residual melt composition, either as a result of fractionation or volatiles loss. We have proposed that the separation of a SCF and infiltration of a volatile phase through crystallized portions of the pegmatite (and eventually the host rocks) would facilitate metasomatic transfer, i.e., assist in the diffusion and advection of elements, such as rare alkalis and HFSE from the melt.…”

Section: Geochemical Aspects Of the Pegmatitesmentioning

confidence: 99%

“…It would facilitate the metasomatic transfer, i.e., assisted in the diffusion and advection of elements, such as rare alkalis and HFSE from the melt. Progressive changes in the residual melt compositions, either due to fractionation or loss of SCF to the walk rock, would additionally influence the melt viscosity (i.e., degree of melt polymerization) and affect the diffusivities of U, Th, and REE (Bartels et al 2011). High concentrations of F and/or P in the hydrous melt or the pegmatite-derived SCF would result in formation of complexes with HFSE and thus aid their progressive enrichment.…”

Section: A Proposed Model For the Origin Of The Wollaston Pegmatitesmentioning

confidence: 99%

Geology and evolution of pegmatite-hosted U-Th ± REE-Y-Nb Mineralization, Kulyk, Eagle, and Karin Lakes region, Wollaston Domain, northern Saskatchewan, Canada: examples of the dual role of extreme fractionation and hybridization processes

McKeough¹,

Lentz²,

McFarlane³

et al. 2013

J. Geosci.

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In northern Saskatchewan, granitic pegmatites intruded Early Paleoproterozoic Wollaston Group metasedimentary rocks and interfolded granitoids that unconformably overlie Late Archean gneisses, all of which have been subjected to deformation during the protracted 1.86 to 1.77 Ga Trans-Hudson Orogeny. The U-Th ± REE-Y-Nb pegmatite intrusions and fracture-controlled U mineralization characterize the occurrences at Kulyk Lake, Eagle Lake, and Karin Lake properties in the Wollaston Domain. The pegmatites are moderately to highly evolved, ranging from mineralogically simple to complex types. These are rare-earth element class, NYF pegmatites (Nb-Y-F), and are interpreted to have formed in a late syn-to post-collisional tectonic setting. The complex-type pegmatites are hybridized, due to metasomatic interaction with the host rocks and therefore are locally crudely zoned. Saturation of U-Th ± REE-Y-Nb occurred at the margins (predominately the border and wall zones) of the hybridized pegmatites. Partial melts were generated at depth, and then coalesced as they intruded to higher structural levels during exhumation of this orogen. This agrees with U-Pb geochronology of these granitic pegmatites, which constrains them between peak-and late-metamorphic events of the Trans-Hudson Orogeny. The age constraints and relatively high-T partial melting conditions (~750 °C) confine the pegmatite melt-forming conditions to an early deformational event (1835-1805 Ma) that was overprinted by high-T retrograde metamorphism at c. 1770 Ma. Field relationships, textures and geochemical variations provide strong evidence that the U, Th, REE ± Y-Nb phases in the studied pegmatites were progressively enriched through extreme fractionation effects of which are evident throughout multiple pegmatite injections. In addition, volatiles and other fluxing components further enriched U, Th, REE ± Y-Nb during complex hybridization reactions between pegmatite melt and wallrock, up to the final stages of pegmatite emplacement.

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Viscosity of flux-rich pegmatitic melts

Cited by 62 publications

References 31 publications

Evidence for lithium-aluminosilicate supersaturation of pegmatite-forming melts

Evidence for lithium-aluminosilicate supersaturation of pegmatite-forming melts

The missing link between granites and granitic pegmatites

Geology and evolution of pegmatite-hosted U-Th ± REE-Y-Nb Mineralization, Kulyk, Eagle, and Karin Lakes region, Wollaston Domain, northern Saskatchewan, Canada: examples of the dual role of extreme fractionation and hybridization processes

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Viscosity of flux-rich pegmatitic melts

Cited by 62 publications

References 31 publications

Evidence for lithium-aluminosilicate supersaturation of pegmatite-forming melts

Evidence for lithium-aluminosilicate supersaturation of pegmatite-forming melts

The missing link between granites and granitic pegmatites

Geology and evolution of pegmatite-hosted U-Th &plusmn; REE-Y-Nb Mineralization, Kulyk, Eagle, and Karin Lakes region, Wollaston Domain, northern Saskatchewan, Canada: examples of the dual role of extreme fractionation and hybridization processes

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Geology and evolution of pegmatite-hosted U-Th ± REE-Y-Nb Mineralization, Kulyk, Eagle, and Karin Lakes region, Wollaston Domain, northern Saskatchewan, Canada: examples of the dual role of extreme fractionation and hybridization processes