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Plot of DNb as a function of run temperature under water-saturated run conditions at 4, 2, and 0.5 kbars.
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Experiments have been conducted with H 2O and H 2O+CO 2-bearing fluids and melts of a Cl-, F-, and lithophile trace element-enriched vitrophyre associated with topaz rhyolite from Spor Mountain, Utah. The partitioning of Li, Rb, Sr, Y, Nb, Cs, and Ce between aqueous fluids and melts of topaz rhyolite composition depends strongly on temperature and...
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Context 1
... P decreases from 4 to 0.5 kbars at water-satu- rated conditions and 950°C, the partition coefficient for Nb increases significantly. At 4 kbars Nb partitions strongly in favor of the melt and partitioning is ap- parently independent of T. At 2 kbars Nb partitions in favor of the fluid for T > 850°C and DNb increases with T (Fig. 5). At 0.5 kbars Nb partitions in favor of the fluid for T ~ 875°C and partitioning of Nb into the fluid increases with T (Fig. ...
Context 2
... Nb increases significantly. At 4 kbars Nb partitions strongly in favor of the melt and partitioning is ap- parently independent of T. At 2 kbars Nb partitions in favor of the fluid for T > 850°C and DNb increases with T (Fig. 5). At 0.5 kbars Nb partitions in favor of the fluid for T ~ 875°C and partitioning of Nb into the fluid increases with T (Fig. ...
Similar publications
Slab-derived supercritical liquids separate into aqueous fluids and hydrous melts during their migration. Separated aqueous fluids further release melt components that cannot be dissolved during ascent. During these processes, elemental partitioning occurs, which may contribute to the geochemical evolution of subduction-zone fluids. Here, we report...
Citations
... In order to quantitatively analyze the lithium isotope fractionation behavior between Li-rich and Li-poor pegmatites during melt-fluid immiscibility, Rayleigh fractionation model was used for evaluation. Previous studies have found that the partition coefficient of lithium between the melt and fluid will increase with increasing temperature and Cl content in the fluid (Webster et al., 1989). Meanwhile, it is observed that the salinity of fluid inclusions in Li-rich pegmatites is generally higher than that in Li-poor pegmatites (Table 1, Fig. 6), and type-1 inclusions are only found in Li-rich pegmatites. ...
The Chakabeishan (CKBS) deposit is a newly discovered pegmatite-type lithium-beryllium deposit in the northern Qaidam tectonic belt of the northern Tibet Plateau. In recent years, some studies have discussed the genesis of the deposit, but the topic remains unclear. This study constrains the genesis of CKBS deposit based on detailed field observations and mineralogical studies, and presents fluid inclusion data and Li isotopic compositions of Li-rich pegmatites and Li-poor pegmatites. The mineralization characteristics of CKBS deposit shows a trend from weak Be mineralization to Li mineralization in the south to north direction, which shows the magmatic differentiation feature. Four types of fluid inclusions are identified: (1) triphase crystal-bearing inclusions (type-1), (2) biphase CO2-rich inclusions (type-2), (3) biphase aqueous inclusions (type-3), and (4) monophase liquid inclusions (type-4). The Li-rich pegmatites mainly contain type-1 inclusions and type-2 inclusions, while Li-poor pegmatites contain type-3 inclusions and some type-4 inclusions. Microthermometric and Laser Raman spectroscopy analyses show that Li-rich pegmatites formed in a low to medium temperature (210.5 ∼ 381.3 ℃), low to medium salinity (5.23 ∼ 17.82 % NaCl equiv.) NaCl-H2O-CO2 system, whereas Li-poor pegmatites formed in a low to medium temperature (206.4 ∼ 413.4 ℃), low to medium salinity (1.05 ∼ 10.49 % NaCl equiv.) NaCl-H2O system, which indicates a fluid immiscibility between them. In addition, lithium is greatly enriched in Li-rich pegmatites under the positive effects of CO2. The Li-rich pegmatites display high Li content (8362.4 ∼ 15509.6 ppm) but low δ7Li values (1.61 ∼ 1.80 ‰). In contrast, the Li-poor pegmatites display low Li content (23.9 ∼ 231.9) but high δ7Li values (0.79 ∼ 12.32 ‰). This means that the lithium isotopic fractionation is produced by the melt-fluid immiscibility in CKBS deposit, in which a Li-rich system with rich water and poor silicate and a Li-poor system with poor water and rich silicate were formed during the process. Therefore, the CKBS deposit may have formed under the combined effects of magmatic differentiation, melt-fluid immiscibility, and fluid immiscibility.
... The transport and precipitation of mineralized minerals are significantly aided by hydrothermal fluids (Hulsbosch et al., 2016), and the amount of Li in apatite may be used to gauge the intensity of the magma that has been exposed to these fluids. Li is more likely to enter the fluid than the magma melt (Webster et al., 1989). Apatite with lower Li content usually represents magmas that were more strongly fluidized at the time of their crystallization (Webster et al., 1989). ...
... Li is more likely to enter the fluid than the magma melt (Webster et al., 1989). Apatite with lower Li content usually represents magmas that were more strongly fluidized at the time of their crystallization (Webster et al., 1989). This study found a substantial association between the change of the Li Sun and McDonough (1989). ...
... The size and shape of boundary layer profiles depend on specific values of K d , D, and v. Enrichments and depletions scale inversely with K d , and a factor of 2 decrease in K d for Li in feldspar and quartz (0.025 rather than 0.05) would lead to greater enrichments by a factor of 2. A lower K d for H 2 O in quartz and feldspar would likely lead to aqueous phase separation. If this phase is not saline, it will not be enriched in Li (Webster et al., 1989) and will not affect our calculations. Further implications of aqueous phases and salinities are discussed in section 4.4. ...
... 50 bars/km) on timescales sufficiently short to prevent Li homogenization. Formation of a Li-enriched aqueous phase (Ellis et al., 2022;Fan et al., 2020), although not supported experimentally unless extremely saline (Webster et al., 1989; see section 4.3), would readily separate by lithostatic vs. aqueous pressure gradients alone. Assuming Li partitions into hydrous melt (and not into aqueous fluid), tectonic context provides a simple explanation for melt extraction. ...
... In principle, an immiscible aqueous phase could form and separate during late stages of magma crystallization, depending on assumed K d for H 2 O and water content of the initial melt (e.g., London, 2014;Sirbescu et al., 2017). If the aqueous phase has NaCl contents <~5 wt%, it will not concentrate Li preferentially compared to melt (Webster et al., 1989), so would not be effective for forming Li-pegmatites. Only when salinities exceed 11 wt% can aqueous solutions preferentially concentrate Li (Webster et al., 1989;Zajacz et al., 2008). ...
... Consequently, one would expect the Li concentration to increase from Early through Mainstage to Late amphibole, in contrast to the analytical data that show an inverse trend (Fig. 7a). However, it is important to note that Li preferentially enters an aqueous fluid when present (Webster et al., 1989). Thus, the decrease in Li concentration observed can be explained by the progressive exsolution of magmatic fluid during the decompression process, leading to mobilization of Li from the magma and a decrease in its concentration in the amphibole. ...
... In nature, Li mostly concentrates in brines (due to Li solubility in water as salts with inorganic anions and hydroxides as LiOH; Munk et al., 2016), clays, and enriched granitic pegmatites. Li concentration in felsic rocks is a direct consequence of Li incompatibility in minerals that crystallize from mafic to silicic melts (Mahood and Hildreth, 1983), resulting in enrichment of residual melts formed during extreme fractional crystallization (Webster et al., 1989;Hofstra et al., 2013). Li has thus been used to constrain the patterns and timescales of various magmatic processes. ...
... However, in subduction zones, the Li-enriched slab can metasomatize mantle rocks when dehydrating (Marschall et al., 2017). In felsic lavas, Li typically range~5-35 ppm (Kent et al., 2007;Tomascak et al., 2016;Ellis et al., 2018;Gion et al., 2022), although specific rhyolites are naturally enriched in Li, with contents up to~140 ppm in topaz rhyolites (Webster et al., 1989;Mercer et al., 2015) and >1,000 ppm in the Macusani rhyolite (London et al., 1988;Pichavant et al., 1988). Li enrichment in crust may depend on its thickness and the extent of differentiation processes, such as in arc context (Chen et al., 2020). ...
... Both studies suggest that Li partitions into the rhyolitic melt over the aqueous fluid. Starting with Li-rich topaz-rhyolites, Webster et al. (1989) ...
Volcanic eruptions are unpredictable phenomena that pose a challenge to crisis management, owing to the fact that contrasted eruptive styles (explosive versus effusive) exhibited at the surface depend on unobservable deep processes occurring in the reservoir and the volcanic conduit. Constricting the behaviour of magma during ascent, and the degassing in particular, allows for a clearer understanding of the relationships between petrological and volcano monitoring signals, and hence a better description of the volcanic hazard. To this aim, lithium (Li) has been used to track magmatic and post-eruptive processes, as a geospeedometer for processes operating on short time scales due to its high mobility in silicate melts and crystals. Yet, the accurate use of Li to assess syn- and post-eruptive processes still lack complete dataset. We propose a review of our current knowledge on Li behavior, with an emphasis on felsic (andesitic to rhyolitic) magmas whose explosive behavior during volcanic eruptions is still poorly understood. We present current knowledge regarding the Li concentration and isotopic compositions, intracrystalline diffusion, and crystal-melt-fluid partition coefficients discovered in felsic magmas and primary crystals. We describe difficulties in interpreting Li data to investigate the differentiation, degassing, ascent rate, volatile fluxing, and cooling of magmas. Finally, we suggest future directions for expanding our understanding of Li behavior.
... The green box represents L-type fluid inclusions of stage II, and green triangle represents C-type fluid inclusions of stage II. The blue box represents L-type fluid inclusions of stage III, and blue triangle represents C-type fluid inclusions of stage III of Li into aqueous fluids over granitic melts at the condition of equilibrium is accompanied with small Li isotope fractionation (< 4‰) (Webster et al. 1989). Teng et al. (2006b) conducted research on the S-type Harney Peak granite and associated Tin Mountain pegmatite and proposed that the δ 7 Li values of magmatic fluids were approximately 4‰ higher than in the parental magma. ...
Carlin-type gold deposits are among the most important gold-bearing hydrothermal ore systems and are mainly located in Nevada, USA, and southwestern China. However, the source and evolution of the ore-forming fluids for these deposits remain controversial, especially those found within China. In this study, lithium and oxygen isotopic analyses of quartz-hosted fluid inclusions are used to elucidate the source and evolution of the giant Shuiyindong Carlin-type gold deposit. Fluid inclusions trapped in quartz of three distinct genetic stages have low salinity (0.8–6.3wt% NaCl equiv.) and moderate temperature (154–343 °C), but display variable Li and O isotope signatures. The Li and O isotopes of stage I fluids (δ⁷Li values from + 5.1 to + 9.1‰; δ¹⁸O values from + 6.3 to + 10.0‰) indicate predominantly a magmatic source for the initial ore-forming fluids. The large variations of Li and O isotopes of stage II fluids (δ⁷Li values from + 9.3 to + 16.0‰; δ¹⁸O values from + 0.1 to + 7.7‰) suggest that the fluids are controlled by mixing of magmatic fluids and meteoric water, which in turn triggered the precipitation of gold-bearing sulfides. The isotopic compositions of stage III fluids (δ⁷Li values from + 15.5 to + 22.8‰; δ¹⁸O values from − 5.4 to − 2.8‰) confirm that the final fluids are dominated by meteoric water. Furthermore, this work demonstrates that the combined Li–O isotopic analysis of fluid inclusions is a powerful tracer to decode the source and evolution of ore-forming fluids in hydrothermal mineralizing systems.
... Although the resurgence-related hydrothermal fluids were initially moderately enriched in Li (7), as is commonly observed in post-caldera magmas in other F-rich caldera systems (53)(54)(55)(56)(57), most of the Li enrichment in the altering fluids likely occurred in the epithermal environment (58). As the initially hot (>300°C) mineralizing fluids cooled and ascended into the volcaniclastic intracaldera sedimentary section, they interacted with lacustrine-derived fluids and leached Li from Li-rich sediments proximal to the center of resurgence (Fig. 4). ...
... Hot and dry intracontinental peralkaline magmas are more likely to retain Li during magmatic differentiation (7) compared to hydrous and calc-alkaline equivalents such as the Caetano Caldera, Nevada and other Oligocene centers in the basin and range (71). This is because dry peralkaline magmas tend to contain less vapor and phenocrystic biotite into which Li may preferentially partition (D Li vapor/melt ≈ 10; D Li biotite/melt = 0.8 to 1.7) (57,72) and fractionate from the magma, resulting in relatively lower Li concentrations in the residual magma. A high initial Li concentration of the magma is essential to form a caldera-hosted Li deposit because in an eruption, as much as 45% of the Li could be lost to the surficial environment during and immediately following an eruption (7,73). ...
Developing a sustainable supply chain for the global proliferation of lithium ion batteries in electric vehicles and grid storage necessitates the extraction of lithium resources that minimize local environmental impacts. Volcano sedimentary lithium resources have the potential to meet this requirement, as they tend to be shallow, high-tonnage deposits with low waste:ore strip ratios. Illite-bearing Miocene lacustrine sediments within the southern portion of McDermitt caldera (USA) at Thacker Pass contain extremely high lithium grades (up to ~1 weight % of Li), more than double the whole-rock concentration of lithium in smectite-rich claystones in the caldera and other known claystone lithium resources globally (<0.4 weight % of Li). Illite concentrations measured in situ range from ~1.3 to 2.4 weight % of Li within fluorine-rich illitic claystones. The unique lithium enrichment of illite at Thacker Pass resulted from secondary lithium- and fluorine-bearing hydrothermal alteration of primary neoformed smectite-bearing sediments, a phenomenon not previously identified.
... Previous studies identified that during partial melting or crystal fractionation processes Li will preferentially partition into the melt (e.g., Seitz and Woodland, 2000;Ottolini et al., 2009) and that partition coefficients between melts and coexisting mantle mineral phases mostly range between 0.1 and 1.0 (Ryan and Langmuir, 1987;Brenan et al., 1998aBrenan et al., , 1998bSeitz and Woodland, 2000;Seitz et al., 2004, Tomascak et al., 2016Neukampf et al., 2019). For silica-rich and alkaline compositions, however, partitioning of Li remains comparatively under-explored (Webster et al., 1989;Iveson et al., 2018;. ...
... Figure 5 compares the K/Cs ratios of K-feldspar crystallized from the supercritical aqueous fluid in experiments with the modeled K/Cs ratios of K-feldspars crystallized from the aqueous fluid in a fluid-saturated melt. The distribution coefficients D aq/melt Cs and D aq/Kfs Cs used in the Rayleigh model are from Webster et al. (1989) and Volfinger (1969), respectively. The results show that the K/Cs ratios for the first crystals of K-feldspar to form (i.e., ,0.2 fraction of melt consumed) in the HDAC experiments are orders of magnitude lower than that predicted for K-feldspar using the Rayleigh fractionation model of London (2022). ...
A review of K-feldspar compositions from miarolitic pegmatites shows that in most pegmatites the pocket K-feldspars are enriched in Rb and Cs relative to exopocket K-feldspar within the same body. Rayleigh modeling of simultaneous crystallization of K-feldspar from a melt and coexisting aqueous solution predicts that the Cs content of K-feldspar falls to nil, which implies that rare-alkali enriched (up to 2190 ppm Cs) pocket K-feldspar must have crystallized from a fluid-undersaturated pegmatite melt. However, most petrologists contend that miarolitic cavities develop after exsolution of an aqueous phase from a pegmatite melt. To investigate the process responsible for the high uptake of Cs and Rb in pocket K-feldspar we determined the rare-alkali content of synthetic K-feldspars that crystallized at 500 °C from a supercritical aqueous fluid in a granitic melt + fluid system. The K/Cs ratio of the synthetic K-feldspar was compared to modeled K/Cs ratios for K-feldspars formed from a water-saturated melt in which the initial Cs concentration (Co) of the melt was identical to the starting glass used in experiments. Our results show that the K/Cs ratios of synthetic K-feldspar are orders of magnitude lower than that predicted using the Rayleigh fractionation model. We attribute the high uptake of Rb and Cs in K-feldspar to kinetic effects associated with rapid crystal growth in an undercooled water-saturated melt. Therefore, we propose that Rb- and Cs-rich K-feldspars that line the pockets of natural miarolitic pegmatites are the products rapid growth in an aqueous fluid that coexists with a highly fractionated residual melt.
... Fractionation of 6 Li and 7 Li could occur by degassing of magmas during their emplacements (Neukampf et al., 2022;Schiavi et al., 2010). During degassing of felsic melts, Li is partitioned into a vapor (fluid) phase (Webster et al., 1989). Fractionation of 6 Li and 7 Li via degassing also results in the depletion of 7 Li in a residual melt, and thus the [Li] and δ 7 Li values of co-magmatic samples show a positive correlation (e.g., Neukampf et al., 2022). ...
Dehydration of subducting oceanic lithosphere (slab) induces Li‐isotope fractionation between the fluid and the slab, suggested by the δ⁷Li variation (∼10‰) in exhumed subduction complexes. Given that arc magmas represent melt of the supraslab mantle, a large δ⁷Li variation is anticipated for arc volcanic rocks. However, the δ⁷Li values in these rocks are mostly homogeneous within the range of mid‐ocean ridge basalts (+1.6 to +5.6‰). The lack of a subduction‐related δ⁷Li signature has been explained by (a) homogenization by mixing of different magma sources, (b) loss of Li from the slab via dehydration, or (c) homogenization by diffusive exchange of slab‐derived Li and the mantle. The Chugoku district in SW Japan is an ideal place to study the process responsible for Li‐isotope variation in arc magmas, since the Chugoku volcanic rocks show large δ⁷Li variation (−1.9 to +7.4‰). High δ⁷Li values (+6.3 to +7.4‰) are found in some high‐Sr andesites and dacites (adakites) whereas low δ⁷Li values (−1.0 to −0.1‰) are found in high‐Mg andesites. The parental magmas of these rocks have been sourced from subducted oceanic crust and sediments, respectively, with various extents of the interaction with wedge mantle. The limited extents of Li isotope modification are indicated by the similarity of the δ⁷Li values of these rocks and their supposed sources. The models for a slab dehydration and a diffusive exchange between slab‐derived melt and mantle demonstrate that the δ⁷Li signatures of the sources can be preserved in the adakites if they ascent rapidly in mantle.
