辽宁岫岩三叠纪侵入岩岩石单位的建立及岩浆演化

ESTABLISHMENT OF ROCK UNITS AND MAGMA EVOLUTION OF THE TRIASSIC INTRUSIVE ROCKS IN XIUYAN AREA, LIAONING PROVINCE

岫岩地区位于华北板块北缘,郯庐断裂带东侧,营口-宽甸台拱之凤城凸起上.区内结晶基底由太古宙变质深成岩及古元古代辽河群层状变质岩系组成.进入印支期,本区岩浆活动强烈,侵入岩发育.据其岩石类型、结构、构造、接触关系、岩浆演化等,将三叠纪侵入岩划分为早三叠世、中三叠世和晚三叠世,建立了岩石单位.其岩浆演化为基性→中性→酸性的演化过程.其中早三叠世侵入岩以中基性辉长岩、闪长岩类为主,并呈大小不等的捕虏体残存于晚期花岗岩中,中三叠世和晚三叠世侵入岩主要为酸性花岗岩类,并呈复式岩基产出.

Xiuyan area is located in the Yingkou-Kuandian uplift on the northern margin of North China plate,where the crystalline basement is composed of Archean metamorphic plutonic rocks and Paleoproterozoic Liaohe group layered metamorphic series.Since Indosinian period,magmatic activities in this area have been severe,with developed intrusive rocks.According to the rock types,structure,contact relationship and magmatic evolution,the Triassic intrusive rocks are divided into Early Triassic,Middle Triassic and Late Triassic rock units.The evolution process of magma is from basic,though intermediate to acidic.Among them the Early Triassic intrusive rocks include mainly intermediate-basic gabbro and dioritoid,occurring in later granite as xenoliths of various sizes.While the Middle and Late Triassic intrusive rocks are dominated by acidic granitoids as composite batholiths.