辽西杨家杖子向斜构造下部隐伏花岗岩接触变质作用

Contact metamorphism of buried granite in the lower part of Yangjiazhangzi syncline,western Liaoning

为了进一步确定杨家杖子钼矿区向斜构造下部是否存在隐伏花岗岩地质体,以及隐伏花岗岩接触变质作用特征,进行了大地电磁测深和钻探验证,结果显示:上富儿沟JK-1井于1 727 m、杨家杖子岭前矿南沟JK-2井于1 514.79 m、喜鹊沟JK-5井于1 159.92 m分别钻遇到花岗岩地质体;大地电磁测深显示杨家杖子向斜构造下部1 160~1 750 m存在隐伏花岗岩地质体,虹螺山大岩基与杨家杖子向斜构造下部的花岗岩体是连通的。以喜鹊沟JK-5井为例,隐伏花岗岩接触变质影响厚度780 m±,接触变质内带,角岩-矽卡岩带,变质程度为辉石角岩相,影响厚度约500 m,发育辉钼矿化;接触变质中带,透辉石大理岩带,角闪角岩相,影响厚度100 m±,发育含有透辉石大理岩;接触变质外带,为含透闪石微晶大理岩,钠长石-绿帘角岩相,宽度180 m,180 m以上过渡到未变质石灰岩。杨家杖子钼矿的主要矿体均产于石灰岩与花岗岩接触带的矽卡岩和斑状花岗岩中,属于矽卡岩-斑岩型钼矿床。

Magnetotelluric sounding and borehole drilling are carried out to confirm the occurrence of concealed granite and its contacting metamorphism in the lower part of the Yangjiazhangzi syncline.Granites were encountered at 1 727 m at the Well JK-1 of Shangfuergou,1 514.79 m at Well JK-2 of Nangou,and 1 159.92 m at Well JK-5 of Xiquegou,respectively.Magnetotelluric data also show that concealed granite occurred at depth between 1 160 to 1 750 m in the lower part of Yangjiazhangzi syncline,and is connected with the Hongluoshan batholith.Taking Well JK-5 of Xiquegou as an example,the thickness of contact metamorphic zone for the granite is^780 m.The inner part of contact metamorphic zone,i.e.,hornfel-skarn zone,is^500 m thick,which was metamorphosed at pyroxene-hornfel facies,and accompanied by molybdenite mineralization.The middle part of contact metamorphic zone,i.e.,diopside-marble zone,is^100 m thick,which was metamorphosed at hornblende-hornfel facies.The outer part of contact metamorphic zone composed of tremolite-bearing microcrystalline marble is 180 meters thick,which was at metamorphosed albite-epidote hornfel facies.The main ore bodies of the Yangjiazhangzi molybdenum deposit are produced in skarn and porphyritic granite in the contact zone of limestone and granite,which are skarn-porphyry type molybdenum deposit.