Depletion, cryptic metasomatism, and modal metasomatism of central European lithospheric mantle: evidence from elemental and Li isotope compositions of spinel peridotite xenoliths, Kozákov volcano, Czech Republic

0443759 - GLÚ 2016 RIV DE eng J - Článek v odborném periodiku
Medaris Jr., L. G. - Ackerman, Lukáš - Jelínek, E. - Magna, T.
Depletion, cryptic metasomatism, and modal metasomatism of central European lithospheric mantle: evidence from elemental and Li isotope compositions of spinel peridotite xenoliths, Kozákov volcano, Czech Republic.
International Journal of Earth Sciences. Roč. 104, č. 8 (2015), s. 1925-1956. ISSN 1437-3254. E-ISSN 1437-3262
Institucionální podpora: RVO:67985831
Klíčová slova: Central European lithospheric mantle * geochemistry * geothermometry * Li isotopes * spinel peridotite xenoliths
Kód oboru RIV: DD - Geochemie
Impakt faktor: 2.133, rok: 2015

Spinel peridotite xenoliths in 4.1 Ma basanite lava at Kozákov volcano vary in equilibration temperature from 675 to 1,135 °C and provide a continuous sample of lithospheric mantle from the Moho to a depth of ca 82 km. The sub-Kozákov mantle is layered, consisting of an upper equigranular layer (UEL) from 32 to 45 km, an intermediate protogranular layer (PGL) from 45 to 66 km, and a lower equigranular layer (LEL) below 66 km. Relative to primitive mantle, all three layers are depleted in major incompatible elements and heavy rare earth elements, with the UEL being most depleted among the three layers, consisting of harzburgite and having experienced >15 % fractional melting. In contrast, the PGL and LEL experienced <10-15 % melting and consist of lherzolite; the PGL and LEL overlap in major element composition, with the PGL displaying a decreasing degree of depletion with depth. Subsequent metasomatism by silicate melt led to cryptic enrichments in large-ion lithophile elements, light REE, and high field strength elements over all the layers and, locally, modal enrichment in orthopyroxene. Metasomatism is accompanied by elevated whole-rock Li contents (1.2-3.6 ppm) and isotopically light δ7Li (-0.8 to -5.8 >). Lithium contents and δ7Li show no strong correlation with rock type or depth, although values of δ7Li are -3.0 in the PGL and >-3.5 > in the UEL and LEL. The layered structure and geochemical characteristics of sub-Kozákov lithospheric mantle are the product of Variscan or pre-Variscan melting, Variscan tectonics, and Neogene volcanism and metasomatism.
Trvalý link: http://hdl.handle.net/11104/0250854