辽西太古代“建平变质杂岩”的变质作用演化

“建平变质杂岩”是辽宁省西部太古代的最下部的地体,它由连续性很差的表壳岩、TTG岩石及其它深成侵入岩构成。基本岩石类型有镁铁质岩石(包括角闪岩、辉石岩、斜长角闪岩等)、麻粒岩、紫苏花岗岩、片麻岩及少量的超镁铁质岩和磁铁石英岩。常见且主要的矿物相是斜方辉石、单斜辉石、石榴石、角闪石、斜长石和石英。岩相学研究确定了指示变质作用不同阶段的三个变质反应的存在,并且它们与推测的矿物相的转化关系吻合,结合地质温压的限定,本文得出了本区太古代末期的强烈的变质热事件的反时针的P-T-t演化轨迹,并推测出此变质热事件与大量的岩浆增聚密切相关。

Evolution of Metamorphism of Archean Jianping Metamorphic Complex from the Western Liaoning Province

Jianping metamorphic complex, the lowest section of the Archean terrain from the western Liaoning Province, is composed of discontinuous supracrustal rocks, TTG series and some other plutons, in which mainly include mafic rock (hornbiendite, pyr-oxenite, amphibolite etc.), granulite, charnockite, gneiss and a small amount of ultramafic as well as magnetite-quartzite (BIF). Common and major mineral phases are orthopyroxene, clinopyroxene, garnet, hornblend, plagioclase and quartz. According to petrographic observation, three metamorphic reactions that show different stages of metamorphism can be determined, which is in accordance with the mineral transformation deduced theoretically. Combined with the estimation of metamorphic pressure and temperature, an anticlockwise P-T-t path for the intense metamorphic thermal event during the end of Archean in this area is obtained, and this thermal event is supposed to be closely related to the accretion of a great deal of magma.