The Study On The Relationship Between Skarn And Ore-Forming Magmatite In The Pusangguo Copper Polymetallic Ore Deposit, Tibet

The Pusangguo deposit is tectonically located at one end of the famous Gangdise metallogenic belt, characterized by complex structures and frequent magma activities which might provide positive minerogenetic conditions.At the same time,it is also a unique skarn-hydrothermal vein type deposit identified by high grades of ores and valuable abundances of elements as a giant metallic deposit in Nanmulin basin, Tibet, China.Since the previous studies of the Pusangguo deposit are unable to describe the forming process of the Skarnr in Pusangguo deposit,especially the exact magmatite which drive the skarn alteration and exact stratum whichis the ore-bearing rock.Based on precious studies and recent ore exploration works of the Pusangguo deposit, this paper uses petrographic chronologyand geochemical studies of the skarn,granodiorite and diorite-porphyrite to get the conclusions below:(1)The intermediate-acid intrusion are granodiorite and diorite-porphyrite which belong to calc-alkaline series,volcanic arc type crust-mantle granite.The intrusion age of diorite-porphyrite(13.6Ma) is near tothe intrusion ageof granodiorite(13.56).The geochemical characteristics of skarn and diorite porphyrite are more analogical.So diorite porphyrite is ore-forming magmatite.(2)There is horizontal alteration zonage from the east diorite-porphyrite to the west granodiorite as garnet skarn-^actinolite-tremolite-epidote skamâ†'marble。And there is vertical petrofacies zonage in the diorite-porphyrite drill hole showing that the alteration and mineralization of upper part is stronger than the below.But granodiorites don’t have this phenomenon.It is obviously seen that akarn alteration has generated in the marble at the bottom of the K1t4.So carbonatite such as limestone and marble is the ore-bearing surrounding-rock.(3)The next exploration must carry on near the dioritic porphyrite and along the layer of marble.