Abstract. Granulite xenoliths from the Quaternary West Eifel Volcanic Field in Germany
record evidence of magmatism in the lower crust at the end of the Permian.
The xenoliths sampled two distinct bodies: an older intrusion (ca. 264 Myr old) that
contains clinopyroxene with flat, chondrite-normalised rare earth element
(REE) profiles and a younger (ca. 253 Myr old) intrusion that crystallised
middle-REE-rich clinopyroxene. The younger body is also distinguished based
on the negative Sr, Zr and Ti anomalies in primitive mantle-normalised
multi-element plots. REE-in-plagioclase–clinopyroxene thermometry records
the magmatic temperature of the xenoliths (1100–1300 ∘C),
whereas Mg-in-plagioclase and Zr-in-titanite thermometry preserve an
equilibration temperature of ca. 800 ∘C. These temperatures,
together with a model of the mineral assemblages predicted from the
composition of one of the xenoliths, define the pressure of crystallisation
as ∼1 GPa. The xenoliths also preserve a long history of
reheating events whose age ranges from 220 to 6 Myr. The last of these
events presumably led to breakdown of garnet; formation of symplectites of
orthopyroxene, plagioclase and hercynite; and redistribution of heavy rare
earth elements into clinopyroxene. The data from the West Eifel granulite
xenoliths, when combined with the existing data from granulites sampled in
the East Eifel, indicate that the lower crust has a long a complex history
stretching from at least 1.6 Ga with intrusive events at ca. 410 and 260 Ma and
reheating from the Triassic to late Miocene.
Lunar Crater volcanic field (Reveille and Pancake Ranges, Basin and Range Province, Nevada, USA)