【作者】 郝梓国； 王希斌； 鲍佩声； 彭根永； 金远新；

【Author】 Hao Ziguo Chinese Academy of Geological Sciences Wang Xibin Bao Peisheng Peng Genyong Jin Yuanxin (Institute of Geology,CAGS)

【机构】 中国地质科学院； 中国地质科学院地质研究所；

【摘要】 新疆西准噶尔地区蛇绿岩同世界上许多蛇绿岩类似,其地幔橄榄岩中的二辉橄榄岩呈 LREE 亏损型；而斜辉辉橄岩、纯橄岩等岩石的 REE 则呈“U”字型富集。在蛇绿岩上部层序中的堆积杂岩和火山熔岩有 N、T、E 三种稀土分配型式,它们均是多种因素作用的结果。稀土元素的特征表明,蛇绿岩形成时的初始岩浆作用发生在一个亏损的地幔区(石榴石二辉橄榄岩区),结束于富集型的地幔区(斜长石和尖晶石二辉橄榄岩区)。钕同位素的研究亦得到证实。理论计算表明,原始地幔岩的熔化程度是：唐巴勒的为21%,玛依勒山20%,达拉布特19．5%,和布克赛尔14．5%,证明 PPG 系列蛇绿岩的熔融程度高于 PTG 系列。更多还原

【Abstract】 The ophiolites in western Junggar,Xinjiang,are the same as many ophiolites elsewhere in the world.The lherzolite in mantle peridotite shows a pattern of LREE depletion,while harzburgite,dunite and other rocks display a“U”-shaped pattern of LREE enrichment.The causes for producing such different LREE distribution patterns are:(1)Partial melting of upper pyrolite,(2)magmatic inclusions,and(3)metasomatism of the,upper mantle.There are three distribution patterns(N,T and E Patterns)in the cumulate complexes and volcanic lavas,resulting from(1)degree of partial melting of upper pyrolite,and(2)crystallization-differentiation of magmas at different depths(differentiation of eclogite,pyroxenite and troctolite). Researches of REE indicate that the magmatism during the formation of ophiolites initiated in a REE-depleted mantle area(Pl-and/or Sp-lher- zolite area),which has been confirmed by Nd isotope study. In terms of the incompatible characteristics of REE,the degree of partial melting calculated using the equilibrium and nonequilibrium equation is 21% in Tangbae,20% in Mayileshan,19.5% in Dalabute and 14.5% in Hebukesai’er,thus suggesting that the degree of partial melting of the PPG lineage of ophiolites is higher than that of the PTG lineage.更多还原