| With the rapid development of Chinese economy,the demand for resources would increase intensively.At present,the situation for metal resources guarantee of nickel, copper and PGE in China is increasingly serious.How to improve the research degree of these mineral resources,innovate the metallogenic theory of Cu-Ni sulfide deposits, perfect the ore-forming evolution model,and guide the prospecting in the depth and border of known deposits,become more and more important.The Jinchuan deposit,hosted by olivine-rich ultramafic rocks,is the world's third largest magmatic Cu-Ni sulfide deposit being currently exploited.Jinchuan is also the largest supply base of Ni-Cu-PGE in China,whose Ni output is 88%of that in the whole China,PGE is 90%,and Cu is more than 13%.It has been prospected and exploited for more than fifty years since it was discovered in 1952.Part of high-grade orebodies has almost been depleted.The resource crisis begins to appear.Therefore how to discover alternative resources in the depth and border of Jinchuan Deposit becomes very urgent.The main clues of the study are the emplacing stage of Jinchuan ultrabasic magma and the evolutional model of magma.Its main research contents are the metallogenic epoch,the ore-forming mechanism,the emplacement mechanism,the magma evolutional-metallogenic model of Jinchuan Cu-Ni sulfide Deposit,the geological characteristics and genesis ofâ… -â‘¥Concealed Cu-rich orebody.Its purpose are to predict the prospecting target area in the depth and border of Jinchuan Deposit and serve the Jinchuan mine.It has very practical significance for guiding the prospecting in the Jinchuan Deposit, increasing its mineral resources,prolonging its Mine Service Life and serving other similar deposits for prospecting by using this perfect metallogenic theory.The main research contents and results are as follows:(1) Based on much geological data and the Surpac software,the three-dimensional visual model of Jinchuan Deposit had been built.It would distinctly and visually demonstrate the three-dimensional relationship among the Jinchuan ore-bearing ultrabasic rockbodies,the Jinchuan main orebodies and the Jinchuan main structure.Through analysis of spatial relationship and morphological characteristics of Jinchuan ultrabasic rockbody,it is realized that the Jinchuan ultrabasic rockbody is divided into two parts (East Part and West Part) and three concentrative segments(East,Middle and West).The main lithofacies feature of East Part rockbody contains large plagioclase,while there locally exists little(or doesn't exist) plagioclase-bearing lherzolite in the West Part rockbody.The basicity of rockbody and ore-beating lithofacies becomes gradually higher, and the enrichment degree of main ore-forming elements increases accordingly,from the East concentrative segment and the West concentrative segment to the Middle one.(2) On the basis of isotope dating data ofâ… -â‘¥Concealed Cu-rich orebody,the previous isotope dating data were systematically collected,synthetically analyzed,then explained with the attitude of development and inter-relation.The preliminary conclusions could be drawn out,which are that the forming age of Jinchuan main orebodies was 800-1000Ma,theâ… -â‘¥Concealed orebody formed at 800-1000 Ma,and the emplacement age of massive Ni-rich orebodies was earlier than 800 Ma.The view is of great significant to the study on the evolution of regional metallogenic environment and guidance the prospecting in the depth and border of Jinchuan Deposit.(3) By comparing the characteristics of orebody,ore and special geochemistry between theâ… -â‘¥Concealed orebody and neighboringâ…¡-â‘ main orebody,theâ… -â‘¥'s mineralization characteristic was summed up.It is concluded that theâ… -â‘¥Concealed orebody has the feature of both magmatic liquation and late reformation.Meanwhile,it is implied that there existed a Cu-rich magma between ore-bearing Ni-rich magma and ore pulp during differentiation by liquation of High MgO Basalts magma derived from mantle in the deep staging chambers.The magma ofâ… -â‘¥Concealed orebody experienced three stages:first,the deep liquation and pulsatory injection of the Cu- and PGE-rich magma; second,the concentration of tectonic activation;third,the later magma hydrothermal superposition.In addition,Pb and S isotope data indicate the magma ofâ… -â‘¥concealed orebody predominantly originates from mantle,but is contamined by a small crustal component.(4) The location of rockbody and orebody is controlled by the activity center of ore-bearing magma and ore pulp,among which the most critical controlling factor is the magma conduits connecting with the activity center of ore-bearing magma and ore pulp. Through contrastive analysis on the geological characteristics of main orebodies of each Mining Area and study on the enrichment law of such elements as Cu,Ni,Pt,Pd,Au and Ag etc.,it is pointed out that there might be a activity center in Exploration Line 6-8 of Jinchuanâ…¡-â‘ main orebody;the junction between Mining Area-â… and Mining Area-â…¡, the junction betweenâ…¡-â‘ main orebody andâ…¡-â‘¡main orebody,and the south of Mining Area-â…¢are the critical prospecting targets.(5) Based on evaluation of geophysical exploration,geochemical exploration, remote sensing technology and other geo-exploration technology etc.,the rational and synthetical combination of prospecting techniques for exploring in the depth and border of Jinchuan Deposit are respectively established according to the actual conditions of Jinchuan Deposit.
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