CAJ | 학술논문

西藏蓬湖西蛇绿岩隶属于班公湖-怒江缝合带的中段,是藏北湖区较好的堆晶岩剖面之一.形成该堆晶岩时矿物分离结晶顺序为铬铁矿→橄榄石→单斜辉石→斜长石,分离结晶作用具有由富镁质、铁质向富铝质、钙质演化趋势.堆晶岩主量元素组成与世界典型蛇绿堆晶岩成分相似;各种堆晶岩石的微量元素和稀土元素配分曲线总体上基本一致,反映其同源性;岩石Nb和Ta亏损,稀土元素含量很低,分配模式呈LREE微弱亏损的平坦型.该蛇绿岩形成于弧后盆地扩张中心,属SSZ型蛇绿岩.
서장봉호서사록암대속우반공호-노강봉합대적중단,시장북호구교호적퇴정암부면지일.형성해퇴정암시광물분리결정순서위락철광→감람석→단사휘석→사장석,분리결정작용구유유부미질、철질향부려질、개질연화추세.퇴정암주량원소조성여세계전형사록퇴정암성분상사;각충퇴정암석적미량원소화희토원소배분곡선총체상기본일치,반영기동원성;암석Nb화Ta우손,희토원소함량흔저,분배모식정LREE미약우손적평탄형.해사록암형성우호후분지확장중심,속SSZ형사록암.
The Western Pung Co Lake ophiolite belongs to the middle segment of the Bangong-Nujiang suture. It is a good ophiolitic accumulate section occurring in Lake Area, northern Xizang(Tibet). The sequence of fractional crystallization of ophiolitic minerals is chromite→olivine→clinopyroxene→plagioclase. It reflects rocks are abundant in Mg and Fe early while rich in Al and Ca later. The composition of rocks of the Western Pung Co Lake ophiolite is similar to that of the representative ophiolitic accumulative rocks in the world. The distribution of trace and rare earth elements of the rocks are consistent each other, which indicates the same genesis of these rocks. Nb and Ta content of rocks are extremely depletion. REE content is very low. Distribution of REE of rocks are flat type with LREE lightly depletion. Petrology and geochemistry characteristics of the Western Pung Co Lake ophiolite indicate it is Supra-subduction zone type ophiolite and formed in a spreading center of a back arc basin.