The geochemical features of the major and trace elements show that the rocks have both cumulates and non-cumulates phases and that all the three minerals; olivine, pyroxenes and plagioclases (ol + pyx + pl) are involved in the fractionation process.
The crustal part of the Muslim Bagh ophiolite has a less developed gabbroic section with relatively thick ultramafic-mafic cumulates section.
The mafic cumulate (gabbros) section is about 600 metres thick (Siddiqui et al., 1996).
The Hosenbein pluton shows many of the key structural, textural, and compositional characteristics of massif-type anorthosite, including (1) predominance of rocks containing 67.5-100 vol% plagioclase, (2) minor amounts of gabbronorite and ferrodiorite, (3) lack of complementary mafic-ultramafic cumulates, (4) predominantly massive adcumulate-mesocumulate texture, (5) mottling, foliation, and modal layering, (6) block structure, (7) plagioclase ([An.sub.41-60]) and orthopyroxene ([En.sub.28-62]) of intermediate composition, and (8) positive whole-rock Eu and Sr anomalies.
Parental magmas for massif-type anorthosite comprise plagioclase-phyric basaltic magmas that were separated from complementary mafic-ultramafic cumulates in the crust-mantle boundary zone (Fig.
Such an origin is consistent with the broadly similar mineralogy of gabbronorite-ferrodiorite to that of the plagioclase cumulates, and their broadly comagmatic origin as suggested by gradational contact morphologies.