Nd, Sr, and O isotopic variations in metaluminous ash-flow tuffs and related volcanic rocks at the Timber Mountain/Oasis Valley Caldera, Complex, SW Nevada: implications for the origin and evolution of large-volume silicic magma bodies

1991 ◽  
Vol 109 (1) ◽  
pp. 53-68 ◽  
Author(s):  
G. Lang Farmer ◽  
David E. Broxton ◽  
Richard G. Warren ◽  
William Pickthorn
Keyword(s):  
Large Volume ◽  
Volcanic Rocks ◽  
Silicic Magma ◽  
Origin And Evolution ◽  
Isotopic Variations

The Origin and Evolution of Large-Volume Silicic Magma Systems: Long Valley Caldera

1997 ◽  
Vol 39 (11) ◽  
pp. 1033-1052 ◽  
Author(s):  
Kurt M. Knesel ◽  
Jon P. Davidson
Keyword(s):  
Large Volume ◽  
Silicic Magma ◽  
Long Valley Caldera ◽  
Origin And Evolution ◽  
Long Valley

Highly siderophile element and Os isotope systematics of the Cenozoic volcanic rocks from the Eastern Pontides, NE Turkey: Constraints on the origin and evolution of subcontinental mantle-derived magmas

Lithos ◽  
2021 ◽  
pp. 106575
Author(s):  
Mehmet Arslan ◽  
İrfan Temizel ◽  
Lukáš Ackerman ◽  
Cem Yücel ◽  
Emel Abdioğlu Yazar
Keyword(s):  
Volcanic Rocks ◽  
Eastern Pontides ◽  
Origin And Evolution ◽  
Isotope Systematics ◽  
Os Isotope

Helium isotopic variations in volcanic rocks from Loihi Seamount and the Island of Hawaii

1983 ◽  
Vol 66 ◽  
pp. 388-406 ◽  
Author(s):  
Mark D. Kurz ◽  
William J. Jenkins ◽  
Stanley R. Hart ◽  
David Clague
Keyword(s):  
Volcanic Rocks ◽  
Isotopic Variations

A hydro-thermo-haline numerical approach of the groundwater flow to explain the extreme Li-enrichment in the Salar de Atacama (NE Chile)

2020 ◽  
Author(s):  
Miguel Angel Marazuela ◽  
Carlos Ayora ◽  
Enric Vázquez Suñé ◽  
Sebastià Olivella Pastallé ◽  
Alejandro García Gil
Keyword(s):  
Land Surface ◽  
Volcanic Rocks ◽  
Numerical Approach ◽  
Origin And Evolution ◽  
Rare Elements ◽  
Salt Flat ◽  
Major Cations ◽  
Salt Flats ◽  
Strong Evaporation ◽  
Hydrogeological Systems

<p>Salt flats (<em>salars</em>) are endorheic hydrogeological systems associated with arid to hyperarid climates. The brines of salt flats account the 80 % of the world’s reserves of Li highly demanded by modern industry. About 40 % of the worldwide Li is extracted from the brine that fills the pores and cavities of the Salar de Atacama. However, the origin of the extreme Li-enrichment of these brines is still unknown.</p><p>The thick accumulation of salts and brines in salt flats results from the groundwater discharge (phreatic evaporation) near the land surface for thousands to millions of years. The strong evaporation contributes the enrichment in major cations and anions as well as other rare elements (e.g. Li, B, Ba, Sr, Br, I and F) which are very attractive for mining exploitation. However, only evaporation cannot explain by itself the extreme concentrations of some of these elements and the strong decoupling between the most evaporated brines and the most Li-enriched brines in the Salar de Atacama. Several hypotheses have been proposed to explain the extreme Li-enrichment of the salt flat brines: (a) concentrated brines leaking down from salt flats located in the Andean Plateau, (b) leaching of hypothetical ancient salt flats buried among volcanic rocks, and (c) rising of hydrothermal brines from deep reservoirs through faults. However, none of them has been able probed neither validated by a numerical model till the date.</p><p>The objective of this work is to discuss the feasibility of the different hypotheses proposed until now to explain the formation of the world's largest lithium reserve. To achieve this objective, two sets of numerical simulations of a 2D vertical cross-section of the entire Salar de Atacama basin are carried out to define (1) the origin and evolution of a salt flat and how climate cycles can affect the location of the most Li-concentrated brines by evaporation and (2) the establishment of the hydro-thermo-haline circulation of a mature salt flat basin.</p>

Contrasting processes in silicic magma chambers: evidence from very large volume ignimbrites

2005 ◽  
Vol 142 (6) ◽  
pp. 669-681 ◽  
Author(s):  
ERIC H. CHRISTIANSEN
Keyword(s):  
Great Basin ◽  
Fractional Crystallization ◽  
Large Volume ◽  
Silicic Magma ◽  
Quasi Equilibrium ◽  
Low Oxygen ◽  
Magma Chambers ◽  
Vertical Zonation ◽  
Liquid Separation ◽  
Mineral Assemblages

Very large volume (>1000 km3 of magma) crystal-rich dacitic ignimbrites that lack pronounced evidence of fractional crystallization or vertical zonation erupt in some continental magmatic arcs (e.g. the Lund Tuff of the Great Basin and the Fish Canyon Tuff of Colorado in western USA). Apparently, their magma chambers were only modestly heterogeneous and not systematically zoned from top to bottom. These ignimbrites have 40 to 50% phenocrysts set in a high-silica rhyolite glass. Mineral assemblages and mineral compositions suggest pre-eruption temperatures were 730 to 820°C and water and oxygen fugacities were relatively high. We have speculated that these very large volume ignimbrites are unzoned because crystallization and convection in slab-shaped magma chambers inhibited separation of crystals from liquids and resulted in a chamber filled with compositionally heterogeneous magma that lacked systematic chemical zonation or strong fractionation. However, many other very large volume silicic ignimbrites are strongly fractionated and may be vertically zoned (e.g. tuffs related to the Yellowstone hotspot). These rhyolitic tuffs typically have few phenocrysts, anhydrous mineral assemblages, low oxygen fugacities, crystallization temperatures of 830 to 1050°C, and a strong imprint of fractional crystallization. Yet these Yellowstone-type rhyolites are derived from chambers 40 to 70 km across which have sill-like shapes (depth/diameter ratios much less than 1). Thus, factors other than chamber shape must be important for establishing the degree of evolution and nature of zonation in silicic magma chambers. Here, the role of crystallinity-dependent viscosity on the evolution of these two types of contrasting magmas is explored. Calculated magma viscosities for the hot, dry, crystal-poor rhyolites are significantly lower than for the cooler, wetter, crystal-rich dacites. Perhaps these hot rhyolites had low enough crystal contents and viscosities to allow efficient crystal–liquid separation, probably by a combination of unhindered crystal-settling, floor crystallization (including compaction), and crystallization on the walls of large chambers. Clean separation of melt from residual solids at their sources may have been promoted by their high temperatures and low viscosities (<104.5 Pa s). In contrast, monotonous dacitic magmas may never have been crystal-free near-liquidus magmas. Their large magma chambers may have developed by progressive growth at a shallow level with repeated input of intermediate to silicic magma. Crystallization of the water-enriched dacitic magmas occurred at lower temperatures (<800 °C) where crystallinity and hence magma viscosity (>106.5 Pa s) were significantly higher. These characteristics inhibited all forms of crystal–liquid separation, hindered development of systematic vertical zonation, and promoted quasi-equilibrium crystallization in small domains within large heterogeneous magma chambers. Eruptions of these crystal-rich dacites may only occur if the roof fails over a growing magma chamber that is becoming increasingly molten.

Fe-Cu-S rich melts in the subcontinental lithospheric mantle: insight from the Lower Silesian (SW Poland) xenoliths

2020 ◽  
Author(s):  
Hubert Mazurek ◽  
Jakub Ciążela ◽  
Magdalena Matusiak-Małek ◽  
Jacek Puziewicz ◽  
Theodoros Ntaflos
Keyword(s):  
Lithospheric Mantle ◽  
Volcanic Rocks ◽  
Oceanic Lithosphere ◽  
Mantle Xenoliths ◽  
Subcontinental Lithospheric Mantle ◽  
Origin And Evolution ◽  
Depleted Mantle ◽  
Group A ◽  
Sw Poland ◽  
Group B

&lt;p&gt;Migration of strategic metals through the lithospheric mantle can be tracked by sulfides in mantle xenoliths. Cenozoic mafic volcanic rocks from the SW Poland (Lower Silesia, Bohemian Massif) host a variety of subcontinental lithospheric mantle (SCLM) xenoliths. To understand metal migration in the SCLM we studied metal budget of peridotites from the Wilcza G&amp;#243;ra basanite and their metasomatic history.&lt;/p&gt;&lt;p&gt;The Wilcza G&amp;#243;ra xenoliths are especially appropriate to study metasomatic processes as they consist of 1) peridotites with Ol&lt;sub&gt;Fo=89.1-91.5 &lt;/sub&gt;representing depleted mantle (group A); 2) peridotites with Ol&lt;sub&gt;Fo=84.2-89.2&lt;/sub&gt; representing melt-metasomatized mantle (group B), as well as 3) hornblende-clinopyroxenites and websterites with Ol&lt;sub&gt;Fo=77.2-82.5&lt;/sub&gt; representing former melt&amp;#160; channels (group C; Matusiak-Ma&amp;#322;ek et al., 2017). The inherent sulfides are either interstitial or enclosed in the silicates. High-temperature exsolutions of pyrrhotite (Po), pentlandite (Pn) and chalcopyrite (Ccp) indicate magmatic origin of the sulfides.&lt;/p&gt;&lt;p&gt;The three peridotitic groups differ by sulfide mode and composition. The sulfide modes are enhanced in group C (0.022-0.963 vol.&amp;#8240;) and group B (&lt;0.028 vol. &amp;#8240;) with respect to group A (&lt;0.002 vol.&amp;#8240;). The sulfides of group C are Ni-poor and Fe-Cu-rich as reflected in their mineral composition (Po&lt;sub&gt;55-74&lt;/sub&gt;Ccp&lt;sub&gt;1-2&lt;/sub&gt;Pn&lt;sub&gt;24-44&lt;/sub&gt; in group A, Po&lt;sub&gt;67-85&lt;/sub&gt;Ccp&lt;sub&gt;1-6&lt;/sub&gt;Pn&lt;sub&gt;14-33&lt;/sub&gt;, in group B and Po&lt;sub&gt;80-97&lt;/sub&gt;Ccp&lt;sub&gt;1-7&lt;/sub&gt;Pn&lt;sub&gt;2-20 &lt;/sub&gt;in group C) and major element chemical composition. Ni/(Ni+Fe) of pentlandite is the lowest in group C (~0.25) and the highest in group A (0.54-0.61). Cu/(Cu+Fe) of chalcopyrite is 0.32-0.49 in group C contrasting to~0.50 in groups A and B.&amp;#160;&lt;/p&gt;&lt;p&gt;The sulfide-rich xenoliths of group C indicate an important role of pyroxenitic veins in transporting Fe-Cu-S-rich melts from the upper mantle to the crust. However, the moderately enhanced sulfide modes in melt-mantle reaction zones represented by xenoliths of group B demonstrate that the upper continental mantle is refertilized with these melts during their ascent. Hence, significant portion of S and metals remains in the mantle never reaching the crust, as has been previously observed in the oceanic lithosphere (Ciazela et al., 2018).&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;&lt;p&gt;&lt;strong&gt;Acknowledgments:&lt;/strong&gt; This study was supported by the NCN project no. UMO-2014/15/B/ST10/00095. The EPMA analyses were funded from the Polish-Austrian project WTZ PL 08/2018.&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;&lt;p&gt;&lt;strong&gt;References:&lt;/strong&gt;&lt;/p&gt;&lt;p&gt;Ciazela, J., Koepke, J., Dick, H. J. B., Botcharnikov, R., Muszynski, A., Lazarov, M., Schuth, S., Pieterek, B. &amp; Kuhn, T. (2018). Sulfide enrichment at an oceanic crust-mantle transition zone: Kane Megamullion (23 N, MAR). Geochimica et Cosmochimica Acta, 230, 155-189&lt;/p&gt;&lt;p&gt;Matusiak-Ma&amp;#322;ek, M., Puziewicz, J., Ntaflos, T., Gr&amp;#233;goire, M., Kuku&amp;#322;a, A. &amp; Wojtulek P.&amp;#160;&amp;#160; M. (2017). Origin and evolution of rare amphibole-bearing mantle peridotites from Wilcza G&amp;#243;ra (SW Poland), Central Europe. Lithos 286&amp;#8211;287, 302&amp;#8211;323.&lt;/p&gt;

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