大兴安岭中部第四纪火山岩中石榴石橄榄岩捕虏体的初步研究  

Preliminary study on garnet peridotite xenolith of Quaternary volcanic rocks in middle Daxing'an Mountain Range.

作　　者：樊祺诚[1] 隋建立[1] 赵勇伟[1] 孙谦[1] 李霓[1] 杜星星[1] 

机构地区：[1]中国地震局地质研究所,北京100029

出　　处：《岩石学报》2008年第11期2563-2568,共6页Acta Petrologica Sinica

基　　金：国家自然科学基金(40772038);地震行业专项(200808014)

摘　　要：大兴安岭中部的绰尔河—哈拉河地区分布有近30座第四纪火山,初步分为更新世火山和全新世火山两期。火山岩中含有丰富的尖晶石橄榄岩和石榴石橄榄岩捕虏体,石榴石橄榄岩的类型主要是石榴石二辉橄榄岩。根据绰尔河新鲜的石榴石二辉橄榄岩 P-T 平衡条件估计(1164℃,2.36GPa),其形成深度约76km。这与中国东部其它地方四相共存的石榴石二辉橄榄岩类似,区别于五相共存的尖晶石/石榴石二辉橄榄岩形成条件(<70kmm),证实它们是来自尖晶石二辉橄榄岩与石榴石二辉橄榄岩相转变带之下深度超过70km 的石榴石橄榄岩稳定区。About 30 Quaternary volcanoes, which can be divided into two stages of Pleistocene and Holocene volcanoes, distribute in the area of Chaoer Rive and Halaha River, middle of Daxin＇anling Mountain Range. Many mantle xenoliths of spinel-and garnetfacies peridotites occur in the volcanic rocks. The garnet peridotites are mainly garnet lherzolites, with typical mineral assemblage of O1 ＋ Opx ＋ Cpx ＋ Gt. Calculated P-T condition of the garnet lherzolite （with fresh garnet, no kelyphite-rim） is 1164℃ and 2.36 GPa, equals to the depth of 76kin. This result agrees with former researches on P-T conditions of other four-phase garnet lherzolite in eastern China, but differs from that of the five-phase spinel/garnet lherzolite （ general less than 70km）. The fact indicates that magmas of these volcanoes were derived from the mantle source in garnet-facies, which is deeper than 70km.

关 键 词：大兴安岭中部 第四纪火山 石榴石二辉橄榄岩捕虏体 岩石学与矿物学特征 P—T平衡条件 

分 类 号：P588.125[天文地球—岩石学]