Russian Journal of Earth Sciences
Papers in press
Magmatic amphiboles and micas in oceanic peridotites and some specific features
of the felated magmas: 15–20oN MAR fracture zone
B. A. Bazylev, S. A. Silantiev, H. G. B. Dick, and N. N. Kononkova
Abstract
The aim of this work was to study the petrography and mineralogy of mineral
associations with magmatic high-Ti hornblendes and micas in MAR spinel harzburgite. The
mineral compositions were examined using electron and ion microprobes. It was found that
these mineral associations had been formed in a temperature range of 870–950oC as a result
of the crystallization of a residual highly differentiated (96–98%) mantle magma and its
interaction with the host peridotite. Based on the compositions of the pyroxenes and
amphibole, the initial mantle magma was in equilibrium with the minerals of the restite
harzburgite and based on its enrichment in LREE (La/SmN = 10–12) can be classified as
intraplate OIB magma. The absence of a Sr anomaly in the model composition of the initial
magma, evaluated for one of the two MAR areas concerned (Site 16ABP-68), and the
negative Sr anomaly characteristic of the model composition of the magma, calculated for
the other MOR area (Site 16ABP-62), can serve as an independent confirmation of the local
rock heterogeneity in the region of intraplate magma generation, possibly associated with a
crustal component recycling.