小兴安岭伊春地区环斑花岗岩组合特征及其地质意义

Characteristics and significances of rapakivi in Yichun area of Xiaoxinganling,Heilongjiang Province

通过1:25万鹤岗市幅区域地质调查,首次在小兴安岭中南段摩天岭一带发现了具环斑结构的晚石炭世二长花岗岩。环斑长石多呈自形晶宽板状或宽板柱状,少数为圆球状,大小不一,2～3.5cm,内核为肉红色碱性长石,外壳为宽1～2mm的灰白色斜长石,有时也见无环的卵圆形斑晶。其岩相学、岩石地球化学特征研究表明,摩天岭环斑花岗岩及其岩石组合为不同于前寒武纪典型非造山环斑花岗岩的造山带型环斑花岗岩,为形成于造山带与板块俯冲体制有关的岛弧或活动大陆边缘环境下的I型花岗岩。

Through 1：250000 geological mapping of Hegang City, the authors discovered adamellite in Motianling area in the middle and south of the Xiaoxinganling Mountain, which has the rapakivi texture, and was formed in Late Carboniferous. The rapakivi feldspars are idiomorphism and assume mainly broad platy or broad columnar and subordinately spherical forms. The sizes of the rapakivi feldspars vary from 2 cm to 3.5cm. The core is pink alkali feldspar, and the crust is grayish white plagiodase 1-2mm in size. Some are spherical phanerocrysts without rapakivi. A study of lithofacies, petrochemical and geochemical characteristics of the Motianling raparkivi granite and the rock assemblage shows that it is different from the representative anorogenic raparkivi granite of the Precambrian orogenic belt. It is the I-type granite in the orogenic belt related to the subduction of the plate system and the active continental margin of the island.