摘要
辽东一吉南沉积变质再造硼矿床成矿物质来源于古火山活动。沉积于早元古代箕状断陷盆地沉降中心。其中有3个含硼沉积旋回,上部旋回含矿性最好。含硼镁质碳酸盐岩矿源层,在吕梁运动变质热液作用下转化为含矿溶液,受该时期东西向褶皱层间剪切运动控制,顺层流入褶曲翼部低压空间和背斜轴部虚脱部位聚集、交代、沉淀,形成硼矿床。矿床具严格的层控特点,并主要分布于层间剪切运动强烈的东西向复背斜和背斜的倒转翼或陡翼,以及复背斜轴部次一级向斜翼部的陡倾地段。中新生代构造运动使矿层重新破碎,并在新的纵弯褶曲层间剪切应力作用下,塑性流动到背斜轴部形成厚矿体,或受正断层上盘下降过程的挤压,从上盘流到下盘富集。由上部含硼沉积旋回所构成的东西向复背斜、背斜的倒转翼为该区主要找矿靶区。
The materials in relation to the mineralization in the sedimentometamorphicboron helt through East Liaoning-South Jilin region had a close link with ancientvalconic activitics,then coming together into the deepest parts of the EarlyProterozoic semigraben basin.In these tectonic depressions,three boron-bearingsedimentary cycles have so far been recogniged.The first cycle,represented byWengquangou deposit,is dominated by magnetite-ascharite paragenesis.The secondis well-developed in Gaotaigou deposit with the same mineral paragenesis as the first.The third,made up of ascharite alone,yields quite a few large-sized deposits likeHouxianyu,Zhuanmiao,etc.,of the most important economy.In all these cycles,the magnesiocarbonate rocks are believed as source beds which later converted intomineralizing solutions in the presence of metamorphic fluids associated with Lüliangmovement.At the same time,these solutions were governed and directed by interbedshear stress from EW-trending folding into the low pressure zones of flanks of folds,or into the incoherent zones of their axes.These two structural environments greatlyfavoured them to concentrate,replace,precipitate and eventually form boratedeposits.From the above explanation,it is not difficult to sum up that the sourcebeds of magnesiocarbonate rock are exactly what is seen today to be boratized beds,displaying a extreme strataboundnese.In a word,almost all of orebodies lie eitheralong overturn or steep flanks of EW-striking anticlinoriums and anticlines whereinterbed shearing took place vigorously,or at steep-dipping parts of flanks ofsecondary synclines.Later,by Mesozoic-Cenozic times,neotectonism caused theorebeds to deform,even break down and plastically flow,impeled by interbed shearstress,into axial parts Of anticlines or into footrwalls of normal faults.All this isclearly reflceted in the EW-trending anticlinorium and anticlines of the third cyelewhich are reasonably regarded as prospective exploration targets in the future.
