Marginal Zone of Mesozoic Basin in Jiaodong Area——The Cradle of Large(Super-large)Scale Type Gold Deposits

Marginal zone of Mesozoic basin in Jiaodong area is one of the area where gold deposits prospecting has gained new breakthrough in recent years.Some medium,large and super-large type gold deposits have been discovered in this area,such as Pengjiakuang gold deposit in Rushan,Xilaokou gold deposit,Jinzhuang gold deposit in Muping,Songjiagou gold deposit,Guocheng gold deposit in Haiyang,Dazhuangzi gold deposit in Pingdu,Xilin gold deposit in Qixia,Hushan gold deposit and Dujiayagold deposit in Fushan area.These gold deposits have the characteristics of the same period and same source with altered rock type gold deposit in northwest of Jiaodong area.But they were formed in different geological space,different surrounding rock conditions,and formed a group of epithermal deposit which have close contact relation with Mesozoic magmatic-tectonic activities in late Yanshan period.Its diagenetic and metallogenic ages are between 127.6~105Ma.Material sources have the characteristics of mixed source with shell and mantle.Magmatic activities caused the extraction of gold elements of activation fluid and new fluid seperated and dissoluted from magma fractional in internal and surrounding rocks of granites.It is important oreforming factors.Gold deposits occurred in fractural system in marginal zone of the basin.Extension and detachment has provided favorable spaces for mineralization.Accompanying with Mesozoic lithosphere thinning,and hot doming-extensional structures generated by emplacement of large-scale intrusive rocks(hidden),and formed unique alterated complex type gold deposit in marginal zone of the basin.Deposit characteristics can compare with altered rock type gold deposit in northwest Jiaodong area.It is indicated that there has great ore potentiality in this area.