GEOLOGICAL FEATURES OF TRIASSIC ALKALINE AND SUBALKALINE IGNEOUS COMPLEXES IN THE YAN-LIAO AREA

A number of Triassic (245-195 Ma) alkaline or subalkaline igneous complexes were discovered in the Yan-liao area in the northern part of the North China platform. These complexes are all poor in SiO2; most of them are rich in Fe, Mg, K and P and such incompatible elements as Rb, Ba. U and Sr and REE; the initial Sr-87 /Sr-86 ratios range from 0.7055 to 0.7057. They might have originated in the altered upper mantle. On that basis coupled with the distribution of the Triassic System and the tectonic deformation, it is suggested that there should have existed a tectono magmatic belt in the area in Triassic time, which is an important manifestation of the Indosinian movement in the area.Geosciences, MultidisciplinarySCI(E)2ARTICLE4339-355