吉林通化地区光华岩群斜长角闪岩变质作用特征及其构造意义

摘要

There is a set of amphibolite from Shuangmiao Formation of Guanghua Group in Tonghua area of Jilin,which is located in the northern margin of North China Craton.The amphibolite is one of the maj or metamorphic rocks consisting of Precambrian metamorphic basement.The original rock of amphibolite mainly belongs to subalkaline basalt,which maybe form in the island-arc setting. The amphibolites undergo three stages of metamorphism,including prograde,peak and retrograde stages.Mineral assemblage at prograde stage is Gt1+Hbl1+Pl1(the value of An is 13-16)+Q,and the pressure and temperature are 4.7-5.2 kbar and 544 ℃-555 ℃;mineral assemblage at peak stage is Gt2+Hbl2+Pl2(the value of An is 28-31)+Ilm2+Bt2+Q,and the pressure and temperature are 8.1-8.8 kbar and 655 ℃-673 ℃;mineral assemblage at retrograde stage is Gt3+Chl+Ath+Hbl3+Bt3+Ilm3+Pl3 (the value of An is 16-18)+Q,and the pressure and temperature are 7.9-8.3 kbar and 546 ℃-557 ℃.The metamorphic evolution process of amphibolite shows the counterclockwise P-T path,which is characterized by near-isobar cooling (IBC)processes.It is suggested that there is a tectonic evolution from Archean-Paleoproterozoic proto-ocean to collision of orogeny,and then orogenic taper,and the last magmatic undergrowth in Tonghua area of Jilin,China.%位于华北板块北缘的吉林通化地区光华岩群双庙岩组地层中存在一套斜长角闪岩,其是构成前寒武纪变质基底的主要变质岩之一.该斜长角闪岩的原岩主要为亚碱性玄武岩,可能形成于岛弧构造环境.该斜长角闪岩共经历了3个阶段变质作用,分别为进变质阶段、峰期变质阶段、退变质阶段.进变质阶段矿物组合为石榴石1+普通角闪石1+斜长石1(An牌号为13~16)+石英(Gt1+Hbl1+Pl1+Q),温度和压力范围分别为544℃~555℃和4.7~5.2 kbar;峰期变质阶段矿物组合为石榴石2+普通角闪石2+斜长石2(An牌号为28~31)+钛铁矿2+黑云母2+石英(Gt2+Hbl2+Pl2+Ilm2+Bt2+Q),温度和压力范围分别为655℃~673℃和8.1~8.8 kbar;退变质阶段矿物组合为石榴石3+绿泥石+直闪石+普通角闪石3+黑云母3+钛铁矿3+斜长石3(Au牌号为16~18)+石英(Gt3+Chl+Ath+Hbl3+Bt3+Ilm3+Pl3+Q),温度和压力范围分别为546℃~557℃和7.9~8.3 kbar.斜长角闪岩的变质演化过程呈现为近等压冷却(IBC)型的逆时针变质作用压力(P)-温度(T)轨迹.该地区经历了从太古宙—古元古代原大洋→碰撞造山→造山后拉伸→岩浆底侵作用的构造演化过程.