长江上游地区几个层状基性-超基性侵入体的岩石特征及有关岩石学问题

PETROGRAPHIC CHARACTERISTICS AND SEVERAL OTHER RELATED PROBLEMS OF THE LAYERED BASIC-ULTRABASIC INTRUSIVES IN THE UPPER YANGTZE VALLEY

Three iron-, titanium-rieh layered basie-ultrabasie intrusives have been described.They occur in an approximately south-north striking belt of tectonie-magmatic complex within an anteklise. Iron and titanium were concentrated in the lower or middle lower parts of these intrusives in the early and middle stages of differentiation, during which 《FeO》 may have played an important role. Intimate spatial and temporal association as well as common petroehemical features (i.e., high iron and titanium contents) have been found between these layered intrusives and the syenite and alkalisyenite plutons. All of these rocks are considered as hypogene produets of the differentiation of the. Omeishan basaltic magma. In other words, the hypogene differentiation of the iron (titanium)-rieh, sub-alkali Omeishan basaltic magma under the same tectonic-geological conditions resulted in the formation of the rock series of layered intrusives (peridotite→iron, titanium-rich ultramafic rocks→iron, titanium-rich gabbro, plagioclasite)→syenite, alkali-syenite.

Three iron, titanium-rich layered basic-ultrabasic intrusives have been described. They occur in an approximately south-north striking belt of tectonic-magmatic com-plex within an anteklise. Iron and titanium were concentrated in the lower or middle lower parts of these intrusives in the early and middle stages of differentiation, dur-ing which <<FeO>> may have played an important role. Intimate spacial and temporal association as well as common petrochemical features (i.e., high iron and titanium contents) have been found between these layered intrusives and the syenite and alkali-syenite plutons. All of these rocks are considered as hypogene products of the differ-entiation of the Omeishan basaltic magma. In other words, the hypogene differentia-tion of the iron (titanium)-rich, sub-alkali Omeishan basaltic magma under the same tectonic-geological conditions resulted in the formation of the rock series of layered in-trusives (peridotite → iron, titanium-rich ultramafic rocks → iron, titanium-rich gab-bro, plagioclasite)→ syenite, alkali-syenite.