GEOLOGY AND GENESIS OF FENSHUI GOLD DEPOSIT

Fenshui gold deposit,located in northeast of Dashiqiao,Liaoning Province,occurs in the external contact belt of Shipengyu super-unit,belonging to post-magmatic mesothermal deposit.Archean metamorphic plutonite,upper crustal rock and Liaohe group metamorphic formation are distributed in Fenshui gold field.The former is the main wall rock of gold ore body.The biotite alkali-feldspar granite of Shipengyu super-unit, formed in early Yanshanian stage (Rb-Sr 186±13 Ma),is the ore-forming parent rock of Fenshui gold deposit.The main gold ore bodies occur in single quartz veins in plate,vein or lenticle shapes,10-129.5 meters long and 0.25-2.98 meters thick.The mean grade of gold ore is 11.71×10-6,with a variation of 71.9% to 234%, belonging to even-most uneven type.There are 46 ore bodies with 1839.5 kg of total reserves in Fenshui gold deposit.More than 5000 kg of gold have been mined since 1939.The characteristics of lead isotope show that the ore-forming material of Fenshui gold deposit originated from two sources of 186±13 Ma and 2800 Ma±.In early Yanshanian stage, the post-magmatic hydrothermal solution that derived from middle-plutonic intrusion (186±13 Ma)of biotite alkali feldspar granite in Shipengyu ultra-unit extracted ore-forming materials from country rock (2800 Ma±) to form gold deposits little later than 186±13 Ma.