吉林省金城洞地区金矿成矿物质来源

ORE Forming MATERIAL RESOURCES OF GOLD DEPOSITS IN JIN CHENG DONG AREA JILLN PROVINCE

金城洞地区金矿按产出地质背景划分为产于晚太古宙变质岩系中的金矿和产于花岗岩侵入体中的金矿。变质岩系金丰度分析表明，本区变质岩石金丰度背景值为２０４×１０－９，花岗岩金丰度分析表明，中生代二长岩中金丰度为６６０７×１０－９，其它花岗岩中则较低，为０７—２８３×１０－９；各类岩石金易溶性实验表明，区内斜长角闪岩、二长岩、煌斑岩中金呈易释放金形式存在，可为金矿成矿提供部分成矿物质，其它岩石中金呈不易释放金的形式存在。区内岩（矿）石硫同位素组成δ３４Ｓ在＋００４～＋４８‰之间，与陨石硫δ３４Ｓ值（－１～＋５１‰）相近；各类岩（矿）石稀土元素模式曲线平行分布，以ＬＲＥＥ富集、弱—无铕异常为特征，反映了它们具有相似的来源；各类铅同位素分析表明，变质岩、花岗岩、金矿石的铅同素组成投点均落于μ＝８５和μ＝９５８之间，进一步反映了成矿物质来源于深源（下地壳和上地幔之间）。

Gold deposits in Jinchengdong area can be devided into two types,one occur late Archean metamorphic rocks,another occur granitic entrusives.Gold abundance analyses show that the background value of metamorphic rocks is 2.04×10 -9 ,the value of the Mesozoic monozonites is 66.07×10 -9 ,the other granites have low gold abundance.The dissolved experiment of different rocks show that the gold of plaiogoamphioble,monozonite and lamprophyre is easily dissolved,and provide partial ore forming materials for gold deposits,but it is difficult to dissolve the gold of other rocks.The different rocks have the unifrom sulfar isotope composition and similar with chronide values,this indicates ore forming materials are from abyssal resoures.Rare earth element curves of differient rocks are parallel,charactered with LREE enrichment and little Eu anomoly,this feature indicates these rocks have the similar resources.Lead isotope of the rocks(ores)plot in area between u=8.5 and u=9.58 line,this further indicate the ore forming materials come from abyssal resoures(under crust or upper matle).