摘要
辽北晚前寒武纪高压变质带展布于建平—北票一带。高压变质带由榴辉岩、石榴单斜辉石岩等高压变质基性岩组成。这些岩石遭受了从麻粒岩相到角闪岩相连续退变质作用的改造。早期榴辉岩相变质反应条件为：Ｔ＝８００℃±，Ｐ＞１．５ＧＰａ；麻粒岩相的温压条件为：Ｔ＝８００～９００℃，Ｐ＝０．９～１．１５ＧＰａ，属中高压型；晚期角闪岩相的温压条件变为：Ｔ＝５７０～６５０℃，Ｐ＝０．６０～０．７５ＧＰａ。变质反应的Ｐ－Ｔ－ｔ轨迹呈现出顺时针演化。结合辽北造山带其它的标志判断，这些高压变质岩的形成和抬升与中、新元古代时期洋壳俯冲消减和陆块碰撞，并伴随快速构造上升有关。
he high pressure metamorphic belt of Late Precambrian,first discovered in Jianping Beipiao area(Chen Shuliang et al.,1995),is composed of high pressure metamorphic basic rocks:eclogite,granulite,garnet clinopyroxenite and so on,and have undergone 3 stages of metamorphism:the early stage of eclogite facies aggrading metamorphism;the middle stage of granulite facies retrograde metamorphism;in the end, the late stage of amphibolite facies regional metamorphism with PT conditions respectively being 800℃±,P>1.5GPa;800900℃,0.91.15GPa;570650℃,0.60.75GPa,and its PTt path clockwise.The above mentioned facts and other indictors of Liaobei orogenic belt suggest that the formation and uplift of the high pressure metamorphic belt is related with subduction of ocean crust,collision between continents,and therefrom the rapid uplift in Middle to Late Proterozoic.
关键词
高压变质带
P-T-T轨迹
晚前寒武纪
辽北
地层
High pressure metamorphic belt PTt path Late Precambrian North Liaoning
