Mesozoic picritic and alkali basalts from central Lebanon represent a significant part of an
extension-related Upper Jurassic to Upper Cretaceous discontinuous volcanic belt which occurs
throughout the Middle East. Volcanism was associated with an episode of intraplate extension that
followed a period of continental break-up, where Mesozoic micro-continental blocks separated from
Gondwana as the Neotethys ocean opened in Jurassic times. This volcanic episode produced mafic
lava flows ranging in thickness from 5 to 20 m, along with some minor pyroclastic flows. These flows
are stratigraphically intercalated with thick carbonate platform deposits. The basalts are made up of
about 15–20% olivine (Fo78–91), 30–35% clinopyroxene (salite), 40–50% plagioclase (An56–71) and
opaque Fe–Ti oxides (∼5%). Geochemically, the rocks exhibit a relatively wide range of SiO2 (40.4 to
50.5 wt%) and MgO (5.1 to 15.5 wt%) contents, are relatively enriched in TiO2 (1.7 to 3.7 wt%) and
vary in composition from alkali picrite and basanite to alkali basalt. The Mg numbers range from 0.56
to 0.70, with an average of 0.63. The rocks are enriched in incompatible trace elements such as Zr
(86–247 ppm), Nb (16–66 ppm) and Y (19–30 ppm). Such compositions are typical of those of
HIMU-OIB and plume-related magmas. The REE patterns are fractionated ((La/Yb)N = 11), LREE
enriched, and are generally parallel to subparallel. Elemental ratios such as K/P (1.1–4.7), La/Ta
(11–13), La/Nb (0.57–0.70), Nb/Y (0.68–1.55) and Th/Nb (0.20–0.36) suggest that crustal contamination
was minor or absent. This may be related to a rapid ascent of the magma, in agreement with the
nature (mafic, oceanic-like) and the small thickness (about 12 km) of the Mesozoic crust of the Eastern
Mediterranean region. The 143Nd/144Nd isotopic compositions of the lavas range from 0.512826 to
0.512886, and 87Sr/86Sr from 0.702971 to 0.703669, suggesting a HIMU-like mantle source. Trace element
compositions indicate a melt segregation depth of 100–110 km, well within the garnet lherzolite
stability field. The geochemical characteristics of the rocks are typical of within-plate alkali basalts,
and suggest that the magmas were derived from a fertile, possibly plume-related, enriched mantle
source. Petrogenetic modelling indicates that the magmas were produced by very small degrees of
batch partial melting (F = 1.5%) of a primitive garnet-bearing mantle source (garnet lherzolite).