Geochemical characteristics of the high- and low-Ti basaltic rocks from the uplifted shoulder of the Ohře (Eger) Rift, Western Bohemia
Abstract
The volcanic rocks intrude the Variscan basement of the uplifted shoulder of the OhŕeRift in the Kruśné hory mountains. Low Mg# (44–59) and Cr, Ni contents and enrichment of LILE, Zr, Hf, Nb, Ta, U, Th and LREE in the high-Ti melanephelinites contrast with the composition of primitive low-Ti olivine melanephelinites/basanites displaying high Mg# (63–74)and high contents of compatible elements.
The high-Ti melanephelinites reveal a wide range in initial 87Sr/86Sr of ca. 0.7034–0.7038 and eNd of 2.4–4.9. The low-Ti melanephelinites show an overlapping range of initial 87Sr/86Sr of ca. 0.7035–0.7036 and eNd of 4.3–5.5.
The large variation in initial 87Sr/86Sr ratios at similar eNd values in those rock types is interpreted as evidence for melting of metasomatized lithospheric mantle sources comprising K-bearing phases with radiogenic Sr.