标题：Trace element and isotopic composition of mafic and ultramafic cumulate xenoliths in alkaline basalts from the Eastern Rhodopes, Bulgaria: Inferences on deep processes under the metamorphic core complexes
期刊名称：IOP Conference Series: Earth and Environmental Science
印刷版ISSN：1755-1307
电子版ISSN：1755-1315
出版年度：2008
卷号：2
出版社：IOP Publishing
摘要：Oligocene within-plate alkaline basalts, intruded in the Eastern Rhodope
metamorphic core complexes Kesebir and Biala Reka, carry ultramafic and mafic
xenoliths, consisting of clinopyroxenites, websterites, orthopyroxenites,
2-pyroxene- and clinopyroxene gabbros. These xenoliths are interpreted as
samples of layered intrusions formed at upper mantle-lower crustal depths.
Calculated parental liquids from LA ICP-MS analyses of clinopyroxene in the
ultramafic clinopyroxenites, orthopyroxenite and websterite indicate that they
may have formed from melts similar in composition to their host basanitic magma.
The clinopyroxene REE patterns of least magnesian websterites suggest amphibole
and clinopyroxene fractionation. Trace element compositions of gabbros and
high-Fe clinopyroxenites indicate that they are the most differentiated product
from the same parent. Calculated parental liquids for some of them, however,
show geochemical features typical for subduction-related rocks. In addition, Sr
and Nd isotopic compositions of evolved websterites and gabbros are more
radiogenic than those of the host basanites. This transition from within-plate
to subduction-related signature can be related to fractionation of amphibole,
accompanied by crustal contamination of the basanitic magma with more radiogenic
lower crustal material.
