Geochemistry Of Platinum-group And Semimetal Elements And Potential Exploration In Depth Of The Western Intrusion Of The Jinchuan Ni-Cu-(PGE) Sulfide Deposit

For most magmatic sulfide deposits,platinum-group elements?PGE,including OS,Ir,Ru,Rh,Pt and Pd?,especially Pt and Pd are strongly correlate with semi-metal elements,such as As,Bi,Sb,Se,and Te.The majority of platinum group minerals?PGM?consist of Pt and Pd complexed with one or more of As,Bi,Sb,Se and Te.Semi-metal elements play a critical role in controlling the distribution of PGE in magmatic sulfide deposits.However,the behaviors of these elements in magmatic systems have not been well known and the researches of this area are still very weak.Thus,it has significant theory to research the relationship between semi-metal elements and PGE in the Jinchuan Ni-Cu-?PGE?sulfide deposit,which is typical of the large-scale mineralization in small intrusion.After more than a decade of prospecting in the depth and border of Jinchuan deposits,some newly-found orebodies have been found in the Longshou mine of Jinchuan deposit,such as line-6 concealed Cu-rich orebody and line-11 orebody at the dept of segment?,No.58 orebody in the south of segment?.It is important for us to understand the geological features and orebody emplaced rules of the Jinchuan deposit by studying these new orebodies.The study objects of these thesis includ No.58 orebody,the main orebody of segment?,No.24 orebody of segment?,concealed Cu-rich orebody between segment?and segment?,and No.1 orebody of western part of segment?.All these orebodies belong to the Longshou mine of the Jinchuan deposit.The features of rock,mineralogical and deposit of orebody of the Jinchuan deposit have been investigated.To compare the differences between the western intrusion and the eastern intrusion of the Jinchuan deposit,the contents of Ni,Cu,PGE and semi-metal elements of different types of sulfide ores have been measured.It is significant for us to understand the relationship between semi-metal elements and Ni,Cu,PGE and the petrogenetic significances of Jinchuan deposits by studying these.Meanwhile,the research of the newly-found orebody shape,spatial relationship,geochemistry characteristics and genetic type will enrich the petrogenetic of Jinchuan deposits and providing a theory bases for seeking new orebodies in depth and border and ore-bearing magmatic plumbing system.The main results of this thesis are summarized below:?1?The semi-metal elements concentrated in sulfide melt together with Ni,Cu,and PGE during sulfide immiscibility.In the subsequent crystallization of monosulfide solid solution?mss?from the sulfide melt,the semi-metal elements and Ni,Cu and PGE behave incompatibly and remain in the residual sulfide liquid.However,some semimetal elements will partition into pentlandite during mss fractionation with Pd.?2?The similar contents of Ni,Cu,PGE and semi-metal elements of the western intrusion and the eastern intrusion of the Jinchuan deposit implied that they may come from the same source.Additionally,the different primitive-mantle normalized PGE patterns of the sulfides ores of the two ore-bearing intrusion implied that the sulfide of them experience different fractional crystallization.?3?The variations of S/Se in the Jinchuan deposit have been influenced by sulfide segregation,crustal contamination and hydrothermal alteration.The low S/Se ratio of ores may be related to S loss during hydrothermal alteration.?4?Owning to the genesis relationship between Cu-rich orebody and massive orebody,there maybe some unfounded orebodies in the dept of Cu-rich orebody.?5?The No.58 orebody do not correlate with segment?in space,but the similar contents of PGE and semimetal elements implied that the two ore-bearing rock may come from the same source.The fracture zone is the most important ore-controlling factor in the No.58 orebody and may intersect fault F₈ in the deep.The prospect of seeking new ore-bearing ultramafic intrusions or orebodies is in the dept of the fracture zone.