scholarly journals Redox state of southern Tibetan upper mantle and ultrapotassic magmas

Geology ◽  
2020 ◽  
Vol 48 (7) ◽  
pp. 733-736 ◽  
Author(s):  
Weikai Li ◽  
Zhiming Yang ◽  
Massimo Chiaradia ◽  
Yong Lai ◽  
Chao Yu ◽  
...  
Keyword(s):  
Upper Mantle ◽  
Lithospheric Mantle ◽  
Redox State ◽  
Volcanic Rocks ◽  
Mantle Xenoliths ◽  
Continental Plate ◽  
Cratonic Mantle ◽  
Tectonic Settings ◽  
Mantle Condition ◽  
Typical Range

Abstract The redox state of Earth’s upper mantle in several tectonic settings, such as cratonic mantle, oceanic mantle, and mantle wedges beneath magmatic arcs, has been well documented. In contrast, oxygen fugacity () data of upper mantle under orogens worldwide are rare, and the mechanism responsible for the mantle condition under orogens is not well constrained. In this study, we investigated the of mantle xenoliths derived from the southern Tibetan lithospheric mantle beneath the Himalayan orogen, and that of postcollisional ultrapotassic volcanic rocks hosting the xenoliths. The of mantle xenoliths ranges from ΔFMQ = +0.5 to +1.2 (where ΔFMQ is the deviation of log from the fayalite-magnetite-quartz buffer), indicating that the southern Tibetan lithospheric mantle is more oxidized than cratonic and oceanic mantle, and it falls within the typical range of mantle wedge values. Mineralogical evidence suggests that water-rich fluids and sediment melts liberated from both the subducting Neo-Tethyan oceanic slab and perhaps the Indian continental plate could have oxidized the southern Tibetan lithospheric mantle. The conditions of ultrapotassic magmas show a shift toward more oxidized conditions during ascent (from ΔFMQ = +0.8 to +3.0). Crustal evolution processes (e.g., fractionation) could influence magmatic , and thus the redox state of mantle-derived magma may not simply represent its mantle source.

Ultramafic mantle xenoliths in the Late Cenozoic Volcanic rocks of the Antarctic Peninsula and Jones Mountains, West Antarctica

2021 ◽  
pp. M56-2019-44
Author(s):  
Philip T. Leat ◽  
Aidan J. Ross ◽  
Sally A. Gibson
Keyword(s):  
Antarctic Peninsula ◽  
Upper Mantle ◽  
Lithospheric Mantle ◽  
Volcanic Rocks ◽  
Oceanic Lithosphere ◽  
Incompatible Trace Element ◽  
Mantle Xenoliths ◽  
South Shetland Islands ◽  
West Antarctica ◽  
Gondwana Margin

AbstractAbundant mantle-derived ultramafic xenoliths occur in Cenozoic (7.7-1.5 Ma) mafic alkaline volcanic rocks along the former active margin of West Antarctica, that extends from the northern Antarctic Peninsula to Jones Mountains. The xenoliths are restricted to post-subduction volcanic rocks that were emplaced in fore-arc or back-arc positions relative to the Mesozoic-Cenozoic Antarctic Peninsula volcanic arc. The xenoliths are spinel-bearing, include harzburgites, lherzolites, wehrlites and pyroxenites, and provide the only direct evidence of the composition of the lithospheric mantle underlying most of the margin. The harzburgites may be residues of melt extraction from the upper mantle (in a mid-ocean ridge type setting), that accreted to form oceanic lithosphere, which was then subsequently tectonically emplaced along the active Gondwana margin. An exposed highly-depleted dunite-serpentinite upper mantle complex on Gibbs Island, South Shetland Islands, supports this interpretation. In contrast, pyroxenites, wehrlites and lherzolites reflect percolation of mafic alkaline melts through the lithospheric mantle. Volatile and incompatible trace element compositions imply that these interacting melts were related to the post-subduction magmatism which hosts the xenoliths. The scattered distribution of such magmatism and the history of accretion suggest that the dominant composition of sub-Antarctic Peninsula lithospheric mantle is likely to be harzburgitic.

scholarly journals Secular oxidation of Archean upper mantle caused by increasing crustal recycling

2021 ◽  
Author(s):  
Lei Gao ◽  
Shuwen Liu ◽  
Peter Cawood ◽  
Jintuan Wang ◽  
Guozheng Sun ◽  
...  
Keyword(s):  
Upper Mantle ◽  
Redox State ◽  
Incompatible Element ◽  
Volcanic Rocks ◽  
Crustal Recycling ◽  
Incompatible Elements ◽  
Mid Ocean Ridge ◽  
Redox Evolution ◽  
Ocean Ridge ◽  
Plate Subduction

Abstract The redox evolution of Archean mantle impacted Earth differentiation, mantle melting and the nature of chemical equilibrium between mantle, ocean and atmosphere of the early Earth. However, how and why it varies with time remain controversial. Archean mantle-derived volcanic rocks, especially basalts are ideal lithologies for reconstructing the mantle redox state. Here we show that the ~3.8-2.5 Ga basalts from fourteen cratons are subdivided geochemically into two groups, B-1, showing incompatible element depleted and modern mid-ocean ridge basalt-like features ((Nb/La)PM ≥ 0.75) and B-2 ((Nb/La)PM < 0.75), characterized by modern island arc basalt-like features. Our updated V-Ti redox proxy indicates the Archean upper mantle was more reducing than today, and that there was a significant redox heterogeneity between ambient and modified mantle presumably related to crustal recycling, perhaps via plate subduction, as shown by B-1 and B-2 magmas, respectively. The oxygen fugacity of modified mantle exhibits a ~1.5-2.0 log units increase over ~3.8-2.5 Ga, whereas the ambient mantle becomes more and more heterogeneous with respect to redox, apart from a significant increase at ~2.7 Ga. These findings are coincident with the increase in the proportions of crustal recycling-related lithologies with associated enrichment of associated incompatible elements (e.g., Th/Nb), indicating that increasing recycling played a crucial role on the secular oxidation of Archean upper mantle.

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;

scholarly journals Geochemical Characterization of Intraplate Magmatism from Quaternary Alkaline Volcanic Rocks on Jeju Island, South Korea

2021 ◽  
Vol 11 (15) ◽  
pp. 7030
Author(s):  
Cheolhong Kim ◽  
Naing Aung Khant ◽  
Yongmun Jeon ◽  
Heejung Kim ◽  
Chungwan Lim
Keyword(s):  
Fractional Crystallization ◽  
Upper Mantle ◽  
Volcanic Rocks ◽  
Pacific Plate ◽  
Mantle Xenoliths ◽  
Jeju Island ◽  
Eurasian Plate ◽  
Intraplate Magmatism ◽  
The Pacific ◽  
Host Basalt

The major and trace elements of Quaternary alkaline volcanic rocks on Jeju Island were analyzed to determine their origin and formation mechanism. The samples included tephrite, trachybasalts, basaltic trachyandesites, tephriphonolites, trachytes, and mantle xenoliths in the host basalt. Although the samples exhibited diversity in SiO2 contents, the relations of Zr vs. Nb and La vs. Nb indicated that the rocks were formed from the fractional crystallization of a single parent magma with slight continental crustal contamination (r: 0–0.3 by AFC modeling), rather than by the mixing of different magma sources. The volcanic rocks had an enriched-mantle-2-like ocean island basalt signature and the basalt was formed by partial melting of the upper mantle, represented by the xenolith samples of our study. The upper mantle of Jeju was affected by arc magmatism, associated with the subduction of the Pacific Plate beneath the Eurasian Plate. Therefore, we inferred that two separate magmatic events occurred on Jeju Island: one associated with the subduction of the Pacific Plate beneath the Eurasian Plate (represented by xenoliths), and another associated with a divergent setting when intraplate magmatism occurred (represented by the host rocks). With AFC modeling, it can be proposed that the Jeju volcanic rocks were formed by the fractional crystallization of the upper mantle combined with assimilation of the continental crust. The xenoliths in this study had different geochemical patterns from previously reported xenoliths, warranting further investigations.

scholarly journals Crystal preferred orientation of olivine in mantle xenoliths from Catalonia (NE Spain) Orientación cristalina preferente del olivino en xenolitos mantélicos de Cataluña (NE de España)

2018 ◽  
Vol 36 (36) ◽  
pp. 119
Author(s):  
M. Fernández-Roig ◽  
G. Galán ◽  
E. Mariani
Keyword(s):  
Lithospheric Mantle ◽  
Fiber Type ◽  
Volcanic Rocks ◽  
Preferred Orientation ◽  
Mantle Xenoliths ◽  
Fiber Types ◽  
Electron Backscattered Diffraction ◽  
Crystal Preferred Orientation ◽  
Diffraction Patterns ◽  
Península Ibérica

Abstract: Mantle xenoliths in Neogene-Quaternary alkaline volcanic rocks from the Catalan Volcanic Zone indicate that ≪anhydrous≫ spinel lherzolites, harzburgites and much subordinate olivine websterites form the lithospheric mantle of NE Iberian Peninsula. Olivine crystal preferred orientation, determined by indexation of electron-backscattered diffraction patterns, provides three types of deformation fabric: a dominant [010]-fiber type in peridotites and websterites equilibrated at high temperature, and subordinate orthorhombic and [100]-fiber types, which appear mostly in porphyroclas tic and equigranular lherzolites equilibrated at lower temperature.Keywords: Lithospheric mantle, lherzolites, harzburgites, websterites, olivine, deformation fabric.Resumen: Los xenolitos mantelitos en lavas alcalinas neógeno-cuaternarias de la Zona Volcánica de Cataluña indican que lherzolitas y harzburgitas ≪ anhidras≫  y con espinela son las rocas predominantes en el manto litosférico del NE de la Península Ibérica, con presencia también subordinada de websteritas olivínicas. Las orientaciones cristalográficas preferentes del olivino, determinadas por indexación de los espectros de difracción de electrones retrodispersados, muestran tres tipos de fábrica de deformación: una dominante, tipo axial [010], en peridotitas y websteritas equilibradas a alta temperatura, y otras subordinadas, de tipo ortorrómbico y axial [100], que aparecen en lherzolitas porfidoclásticas y equigranulares equilibradas a menor temperatura.Palabras clave: Manto litosférico, lherzolitas, harzburgitas, websterita, olivino, fábricas de deformación

Decoupled water and iron enrichments in the cratonic mantle: A study on peridotite xenoliths from Tok, SE Siberian Craton

2020 ◽  
Vol 105 (6) ◽  
pp. 803-819
Author(s):  
Luc S. Doucet ◽  
Yongjiang Xu ◽  
Delphine Klaessens ◽  
Hejiu Hui ◽  
Dmitri A. Ionov ◽  
...  
Keyword(s):  
Water Content ◽  
Siberian Craton ◽  
Lithospheric Mantle ◽  
Large Scale ◽  
Basaltic Magma ◽  
Mantle Xenoliths ◽  
Spinel Peridotite ◽  
Peridotite Xenoliths ◽  
Cratonic Mantle ◽  
Water Contents

Abstract Water and iron are believed to be key constituents controlling the strength and density of the lithosphere and, therefore, play a crucial role in the long-term stability of cratons. On the other hand, metasomatism can modify the water and iron abundances in the mantle and possibly triggers thermo-mechanical erosion of cratonic keels. Whether local or large scale processes control water distribution in cratonic mantle remains unclear, calling for further investigation. Spinel peridotite xenoliths in alkali basalts of the Cenozoic Tok volcanic field sampled the lithospheric mantle beneath the southeastern margin of the Siberian Craton. The absence of garnet-bearing peridotite among the xenoliths, together with voluminous eruptions of basaltic magma, suggests that the craton margin, in contrast to the central part, lost its deep keel. The Tok peridotites experienced extensive and complex metasomatic reworking by evolved, Ca-Fe-rich liquids that transformed refractory harzburgite to lherzolite and wehrlite. We used polarized Fourier transform infrared spectroscopy (FTIR) to obtain water content in olivine, orthopyroxene (Opx), and clinopyroxene (Cpx) of 14 Tok xenoliths. Olivine, with a water content of 0–3 ppm H2O, was severely degassed, probably during emplacement and cooling of the host lava flow. Orthopyroxene (49–106 ppm H2O) and clinopyroxene (97–300 ppm H2O) are in equilibrium. The cores of the pyroxene grains, unlike olivine, experienced no water loss due to dehydration or addition attributable to interaction with the host magma. The water contents of Opx and Cpx are similar to those from the Kaapvaal, Tanzania, and North China cratons, but the Tok Opx has less water than previously studied Opx from the central Siberian craton (Udachnaya, 28–301 ppm; average 138 ppm). Melting models suggest that the water contents of Tok peridotites are higher than in melting residues, and argue for a post-melting (metasomatic) origin. Moreover, the water contents in Opx and Cpx of Tok peridotites are decoupled from iron enrichments or other indicators of melt metasomatism (e.g., CaO and P2O5). Such decoupling is not seen in the Udachnaya and Kaapvaal peridotites but is similar to observations on Tanzanian peridotites. Our data suggest that iron enrichments in the southeastern Siberian craton mantle preceded water enrichment. Pervasive and large-scale, iron enrichment in the lithospheric mantle may strongly increase its density and initiate a thermo-magmatic erosion. By contrast, the distribution of water in xenoliths is relatively “recent” and was controlled by local metasomatic processes that operate shortly before the volcanic eruption. Hence, water abundances in minerals of Tok mantle xenoliths appear to represent a snapshot of water in the vicinity of the xenolith source regions.

‘Water’ content as a tool to estimate rheological differences in the lithosphere of young extensional basins

2020 ◽  
Author(s):  
Nóra Liptai ◽  
Thomas P. Lange ◽  
Levente Patkó ◽  
Márta Berkesi ◽  
Csaba Szabó ◽  
...  
Keyword(s):  
Rheological Properties ◽  
Upper Mantle ◽  
Lithospheric Mantle ◽  
Pannonian Basin ◽  
Volcanic Field ◽  
Mantle Xenoliths ◽  
Self Healing ◽  
Alkali Basalts ◽  
Extensional Basin ◽  
Marginal Areas

&lt;p&gt;Nominally anhydrous minerals in the lithospheric mantle, such as olivine and pyroxenes can host a small amount (tens to hundreds of ppm) of structurally bound hydroxyl (&amp;#8216;water&amp;#8217;). Numerous studies pointed out that water has a strong effect on the rheological properties of the lithospheric mantle, such as melting temperature, electrical conductivity, viscosity and seismic wave propagation speed. Water content of mantle xenoliths can thus be used to estimate such rheological properties which can then be compared with geophysical observations.&lt;/p&gt;&lt;p&gt;In this study we present effective viscosities and electrical resistivities calculated with the use of &amp;#8216;water&amp;#8217; contents of upper mantle xenoliths from the Carpathian-Pannonian region (CPR). The CPR is a young extensional basin in Central Europe, where intraplate alkali basalts sampled the lithosphere in five areas, including locations from both the central and marginal regions. &amp;#8216;Water&amp;#8217; contents are generally higher in xenoliths from the marginal areas compared with those from the central areas of the CPR, due to significant hydrogen loss during the extension in the Miocene (Patk&amp;#243; et al., 2019). It is demonstrated that due to the different &amp;#8216;water&amp;#8217; contents, the lithospheric mantle in the central areas can be characterized with higher effective viscosity and electrical resistivity, and thus can be considered as more rigid than the marginal areas. This relative rigidity induced by lithospheric thinning may be a general feature of extensional basin systems worldwide, and can be regarded as a &amp;#8216;self-healing&amp;#8217; mechanism of the extending lithosphere.&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;&lt;p&gt;References:&lt;/p&gt;&lt;p&gt;Patk&amp;#243;, L., Liptai, N., Kov&amp;#225;cs, I. J., Aradi, L. E., Xia, Q.-K., Ingrin, J., Mih&amp;#225;ly, J., O&amp;#8217;Reilly, S. Y., Griffin, W. L., Wesztergom, V., Szab&amp;#243;, C., 2019. Extremely low structural hydroxyl contents in upper mantle xenoliths from the N&amp;#243;gr&amp;#225;d-G&amp;#246;m&amp;#246;r Volcanic Field (northern Pannonian Basin): Geodynamic implications and the role of post-eruptive re-equilibration. Chemical Geology, 507, 23-41.&lt;/p&gt;

A review of the composition and chemistry of peridotite mantle xenoliths in volcanic rocks from Antarctica and their relevance to petrological and geophysical models for the lithospheric mantle

2021 ◽  
pp. M56-2021-26
Author(s):  
A. P. Martin
Keyword(s):  
Lithospheric Mantle ◽  
Volcanic Rocks ◽  
Mantle Peridotite ◽  
Mantle Xenoliths ◽  
Future Research ◽  
Isostatic Adjustment ◽  
Peridotite Mantle ◽  
Geodynamic Models ◽  
The Antarctic ◽  
First Time

AbstractThis chapter reviews the geochemistry and petrology of mantle peridotite xenoliths from across Antarctica, including parameters that are of most relevance to geophysical studies. This Memoir is the first time such a complete overview of the chemistry of Antarctic mantle xenoliths has been available and Antarctica should no longer be the ignored continent in studies of mantle xenoliths in volcanic rocks. Xenoliths indicate that the chemistry, heat flow and water content of the Antarctic lithospheric mantle varies regionally at scales of one to thousands of kilometres. The prevalence of variability in xenoliths suggests that the Antarctic mantle is ubiquitously heterogeneous. This has important, yet unquantified, implications for interpreting geophysical data and for reference Earth models used in Antarctic geophysical studies. Information about and interpretations of Antarctic mantle xenoliths can be linked to studies from once adjacent continental blocks in Africa, India, Australia, New Zealand and South America. Together, this can improve understanding of the mantle contribution to glacial isostatic adjustment and geodynamic models to show how the Antarctic mantle fits with adjacent continents in the puzzle of lithospheric blocks. Numerous, fundamental and important research questions remain unanswered making further study of the Antarctic mantle an exciting prospect for future research.

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