西藏扎布耶盐湖钙华岛钙华的地质地球化学特征及意义

扎布耶盐湖属世界独一无二的天然产碳酸锂的盐湖,并富含Cs。该湖钙华岛的钙华自东而西呈高出湖面25～30m、15～25m和0～15m的3套产出。钙华的构造类型有层状构造、蜂窝状构造、鲕粒状构造、块状构造等,结构类型有粒状结构、针状结构、包裹状结构、溶蚀结构、生物结构等。钙华的矿物主要有文石和方解石2种。钙华的CaO为49.49%～51.16%。钙华的稀土元素配分模式均为重稀土元素富集型。3套钙华Cs的平均值为4.54μg/g→6.68μg/g→5.34μg/g,Li的平均值为109.9μg/g→116.5μg/g→136.9μg/g。扎布耶盐湖的Cs、Li等组分的源区是深部的重熔岩浆,泉水为携带成矿物质的载体。其中所含的Cs、Li等元素一部分保存在钙华中,另一部分随泉水汇入盐湖中,盐湖的持续蒸发使湖水中的稀碱金属元素含量增高。

Geological and geochemical features and significance of travertine in travertine-island from Zhabuye salt lake,Tibet,China

The Zhabuye salt lake is a unique salt lake,which naturally produces lithium carbonate and is rich in Cs.From east to west- there are 3 suites of the travertine,respecdvely 25～30m,15～25m,0～15m above the lake surface.There are several fabric patterns of travertine,such as bedded structure.alveohte structure,oohfic structure,block structure,miarohte structure.radial structure.crustose structure and so OIL Textural patterns are made up of granular texture,acicular texture,inclusion texture,solution texture,hollow texture and organic texture.The major minerals in the travertine are aragonite and calcite,which aragonite shows in sohd or hollow acicular tex-tare,calcite appears in rhombic granular texture,parcel structure or corrosion structure.The content of CaO are almost accordant in the 3 sultes of travertine and the average value is 49.49%～51.16%.The NASC normalized REE paerns are also accordant nearly,and all of dleir HREE is rich.The average value of Cs are 4.541μg/→6.68μg/g→5.34μg/g from east to west,and the average of Li appears in an increas-ing trend:109.9μg/g→116.5μg/g→136.9μg/g.It releases CO_2 when spring seeps from underground:Then spdng meets with lake water,due to rapid growth of the spering's pH value,calcium carbonate deposits then forms travertine.The source area of Li,Cs,B in Zhabuye salt lake is deep re-melting magma,and spring is the carrier of the mineralization.Some of the elements such as Cs,Li preserve in travertine,others converge in salt lake.Because of sustained evaporation,the content of rare alkali metal is increasing in salt lake.