The effect of lithium on the viscosity of pegmatite forming liquids

Bartels, Alexander; Behrens, Harald; Holtz, François; Schmidt, Burkhard

doi:10.1016/j.chemgeo.2015.05.011

Cited by 25 publications

(4 citation statements)

References 38 publications

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“…Unzoned pegmatites, however, can be distinguished from their host rock by abundant epidotization and scapolitization, implying that H 2 O-and Cl-bearing fluids were required for the formation of the pegmatitic texture (Heckmann et al, 2022). This is consistent with the prevailing hypothesis proposed for the formation of pegmatitic textures that suggests an important role of volatiles in pegmatite-forming processes (Bartels et al, 2015(Bartels et al, , 2013(Bartels et al, , 2011Jahns and Burnham, 1969;London, 1984;Thomas et al, 2003;Nabelek et al, 2010). Fluxing components, such as H 2 O, can lower crystallization temperatures, nucleation rates, melt polymerization, and melt viscosity while increasing diffusion rates (Fenn, 1977;Mysen and Richet, 2005;Shaw, 1963;Watson and Baker, 1991), and they may thus be the critical factor causing coarse grain size or directional growth habits.…”

Section: Introductionsupporting

confidence: 87%

An experimental study of the effect of water and chlorine on plagioclase nucleation and growth in mafic magmas: application to mafic pegmatites

Heckmann,

Iacono-Marziano,

Strmić Palinkaš

2023

Eur. J. Mineral.

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Abstract. In this study, the effects of H2O and Cl on the grain size and nucleation delay of plagioclase in basaltic magma were investigated using dynamic and equilibrium experiments at 1150 ∘C, 300 MPa, and oxygen fugacity between FMQ − 1.65 and FMQ + 0.05 (fayalite–magnetite–quartz). Each experiment consisted of five samples of basaltic composition (from the Hamn intrusion in Northern Norway) containing varying amounts of H2O (up to 2 wt %) and Cl (up to 1 wt %). The equilibrium experiments were used as a reference frame for the phase assemblage, geochemical composition, and liquidus temperatures and were compared to thermodynamic models using MELTS software. Experimental phase abundances and plagioclase compositions are in good agreement with the predictions of MELTS. The dynamic experiments were initially heated above the liquidus temperature to destroy crystal nuclei and then kept at 1150 ∘C for 100, 250, or 1800 min. These experiments show that as the concentration of H2O in the melt increases, plagioclase nucleation is delayed, plagioclase abundance decreases, but its size increases. Therefore, the addition of H2O seems to favor plagioclase growth at the expense of nucleation. Thermodynamic and kinetic calculations corroborate an increase in the nucleation delay of plagioclase with increasing H2O content dissolved in the melt, suggesting that H2O decreases the undercooling of the silicate melt. The addition of Cl also seems to delay plagioclase nucleation, although this is not supported by kinetic calculations. Increasing the Cl content decreases plagioclase abundance but does not significantly affect its size. The homogeneous pegmatitic pockets of the mafic–ultramafic Hamn intrusion exhibit several petrological and geochemical features, suggesting that H2O and Cl enrichment in the silicate melt was the origin of the pegmatitic texture. The experimental results presented here indicate that H2O, rather than Cl, may have played an important role in the formation of the pegmatitic texture.

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Section: Introductionsupporting

confidence: 87%

An experimental study of the effect of water and chlorine on plagioclase nucleation and growth in mafic magmas: application to mafic pegmatites

Heckmann,

Iacono-Marziano,

Strmić Palinkaš

2023

Eur. J. Mineral.

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“…The Rayleigh fractionation models suggest that with extensive crystallisation the Li content of the last remaining melt can be significantly increased. This is similar to extensive fractionation of granitic melts where the final pegmatitic liquids often produce Li-bearing mineral phases at sub-magmatic temperatures 45 , 46 . In the welded ignimbrites of the Snake River Plain, the contacts between the glassy vitrophyres and the microcrystalline interiors are typically sharp (Fig.…”

Section: Discussionmentioning

confidence: 52%

Post-eruptive mobility of lithium in volcanic rocks

et al. 2018

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To reflect magmatic conditions, volcanic rocks must retain their compositions through eruption and post-eruptive cooling. Mostly, this is the case. However, welded ignimbrites from the Yellowstone–Snake River Plain magmatic province reveal systematic modification of the lithium (Li) inventory by post-eruptive processes. Here we show that phenocrysts from slowly cooled microcrystalline ignimbrite interiors consistently have significantly more Li than their rapidly quenched, glassy, counterparts. The strong association with host lithology and the invariance of other trace elements indicate that Li remains mobile long after eruption and readily passes into phenocrysts via diffusion as groundmass crystallisation increases the Li contents of the last remaining melts. Li isotopic measurements reveal that this diffusion during cooling combined with efficient degassing on the surface may significantly affect the Li inventory and isotopic compositions of volcanic rocks. Utilisation of Li for petrogenetic studies is therefore crucially dependent on the ability to ‘see through’ such post-eruptive processes.

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“…and their solubility in silicate melts, which are critical for the formation of rare metal ores. Notably, melts with high Li contents exhibit low viscosity, favoring large crystal growth and influencing rare metal mineral solubility [1,2]. Volatile components within the melt (such as F, B, and P) exhibit a significant affinity for rare metal elements such as Li.…”

Section: Introductionmentioning

confidence: 99%

Petrogenetic Implications of the Lithium-Rich Tongtianmiao Granite Pluton, South China: Evidence from Geochemistry and Geochronology

Yu,

Zhou,

Cao

et al. 2024

Minerals

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The South China Block, a region renowned for its extensive granite distribution and rich metal deposits, serves as a natural laboratory for the study of granite-related mineralization. This research focuses on the Tongtianmiao granite pluton, which is located at the intersection of the Qin-Hang and Nanling metallogenic belts and has been confirmed as a significant lithium mineral resource. Despite its discovery and ongoing development, the lithium-rich Tongtianmiao pluton has been understudied, particularly concerning its petrogenesis, which has only recently come to the forefront of scientific inquiry. By integrating an array of petrogeochemical data with geochronological studies derived from zircon and monazite dating, this study provides insights into the magmatic processes related to lithium enrichment in the Tongtianmiao granites. The Tongtianmiao granites are classified as A-type granites characterized by high SiO2 contents (69.18–78.20 wt.%, average = 74.08 wt.%), K2O + Na2O contents (4.59–8.34 wt.%, average = 6.86 wt.%), A/CNK > 1.2, and low concentrations of Ca, Mg, and Fe. These granites are enriched in alkali metals such as Li, Rb, and Cs but are significantly depleted in Ba, Sr, and Eu. They show no significant fractionation of light or heavy rare-earth elements but present characteristic tetrad effects. A finding of this study is the identification of multiple ages from in situ zircon U–Pb dating, which implies a prolonged history of magmatic activity. However, given the high uranium content in zircons, which could render U–Pb ages unreliable, emphasis is placed on the monazite U–Pb ages. These ages cluster at approximately 172.1 ± 1.1 Ma and 167.9 ± 1.6 Ma, indicating a Middle Jurassic period of granite formation. This timing correlates with the retreat of the Pacific subduction plate and the associated NE-trending extensional fault activity, which likely provided favorable conditions for lithium enrichment. The study concluded that the Tongtianmiao granites were formed through partial melting of crustal materials and subsequent underplating by mantle-derived materials, and were contaminated by strata materials. This process resulted in the formation of highly differentiated granite through magmatic differentiation and external forces. These findings have significant implications for understanding the petrogenesis of lithium-rich granites and are expected to inform future exploration endeavors in the Tongtianmiao pluton.

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The effect of lithium on the viscosity of pegmatite forming liquids

Cited by 25 publications

References 38 publications

An experimental study of the effect of water and chlorine on plagioclase nucleation and growth in mafic magmas: application to mafic pegmatites

An experimental study of the effect of water and chlorine on plagioclase nucleation and growth in mafic magmas: application to mafic pegmatites

Post-eruptive mobility of lithium in volcanic rocks

Petrogenetic Implications of the Lithium-Rich Tongtianmiao Granite Pluton, South China: Evidence from Geochemistry and Geochronology

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