(1. 中南大學(xué) 有色金屬成礦預(yù)測教育部重點(diǎn)實(shí)驗(yàn)室，長沙 410083；
2. 中南大學(xué) 地球科學(xué)與信息物理學(xué)院，長沙 410083；
3. 金川集團(tuán)股份有限公司 鎳鈷研究設(shè)計院，金昌 737104)
摘 要: Ⅱ-2號礦體為金川銅鎳硫化物礦床的第二大礦體，位于Ⅱ礦區(qū)30行以東。為了解Ⅱ-2號礦體母巖漿在演化過程中的特殊性，采用鎳锍試金ICP-MS法分析金川礦床Ⅱ-2號礦體各類礦石的Cu、Ni、S及鉑族元素(PGE)含量，研究其特征，并與Ⅱ-1號礦體礦石進(jìn)行對比。結(jié)果表明：礦石ΣPGE含量變化較大(44.6×10-9~8526.7×10-9)，Pd/Ir介于1.25~26.55之間，為典型的巖漿型成因。海綿隕鐵狀礦石和局部海綿隕鐵狀礦石為Ⅱ-2號礦體主要的礦石類型，其PGE配分模式極為相似，且為漸變過渡的接觸關(guān)系，說明二者為同一期巖漿侵位的產(chǎn)物。富銅礦石與塊狀硫化物礦石、含細(xì)脈狀礦石的配分模式有互補(bǔ)的特征，富銅礦石具有極高的ΣPGE(8526.7×10-9)和Cu/Ni(5.46)，塊狀硫化物礦石和含細(xì)脈狀礦石相對富集IPGE(ΣPPGE/ΣIPGE＜1)，這三者與海綿隕鐵狀及局部海綿隕鐵狀礦石的區(qū)別明顯，為巖漿演化到后期的產(chǎn)物，而從相互的接觸關(guān)系來看，塊狀硫化物礦先于富銅礦侵位。通過研究Ⅱ-2號礦體與Ⅱ-1號礦體海綿隕鐵狀礦石的鉑族元素及Cu、Ni特征，發(fā)現(xiàn)二者母巖漿均為地幔中等熔融形成的高M(jìn)gO苦橄質(zhì)玄武巖，具有相同的源區(qū)特征；由二者的鉑族元素分異情況、Cu/Ni、Cu/Pd及Ir與Ru、Rh、Pt、Pd的相關(guān)性，研究二者的母巖漿在液態(tài)硫化物-硅酸鹽體系和單硫化物固溶體-液態(tài)硫化物體系中的演化特征，認(rèn)為Ⅱ-1號礦體和Ⅱ-2號礦體中的硫化物是先后從母巖漿中熔離，且分離后具有不同步的演化特征；通過Ⅱ-2號礦體的地球化學(xué)剖面及金川礦床的Cu、Ni品位縱剖面和XOY平面投影等值線圖，證明這種先后熔離作用發(fā)生在深部巖漿房中，而后Ⅱ-2號礦體和Ⅱ-1號礦體的成礦巖漿分別進(jìn)入兩條相對獨(dú)立的巖漿通道，最后由不同的巖漿通道中心侵位到最終的成礦空間，形成Ⅱ-2號礦體與Ⅱ-1號礦體。
關(guān)鍵字: 金川；銅鎳硫化物礦床；鉑族元素；巖漿通道；成礦過程
（1. Key Laboratory of Metallogenic Prediction of Nonferrous Metals,
Ministry of Education, Central South University, Changsha 410083, China;
2. School of Geosciences and Info-Physics, Central South University, Changsha 410083, China;
3. Nickel Cobalt Research and Design Institute, Jinchuan Group Co., Ltd., Jinchang 737104, China）
Abstract:The Ⅱ-2 orebody, which is located in the east of line Ⅱ30, is the second largest orebody of Jinchuan Cu-Ni (PGE) sulfide deposit. In order to find out the particularity of parental magma of Ⅱ-2 orebody during evolution, the contents of platinum group elements(PGE), Cu, Ni and S in Ⅱ-2 orebody were analyzed by using nickel sulphide fire assay technique ICP-MS. Its characteristics were researched and compared with that of Ⅱ-1 orebody. ΣPGE contents of the Ⅱ-2 orebody have large variation range (44.6×10-9-8526.7×10-9). The data of Pd/Ir , which ranges from 1.25 to 26.55, indicates that the Ⅱ-2 orebody is of magmatic origin. Sideronitic ore and partial sideronitic ore, which are the main ore types, have similar distribution patterns. Besides, sideronitic ore and partial sideronitic ore show gradual transition contact, which illustrates that the two ore types are products of the same emplacement period. Copper-rich ore, massive sulphide ore and vein interpenetration ore have complementary relations in the PGE distribution pattern diagram, and there is a clear distinction among these three ore types, sideronitic ore and partial sideronitic ore. The ΣPGE(8526.7×10-9) and Cu/Ni(5.46) of copper-rich ore are extremely high, and massive sulphide ore and vein interpenetration ore have the feature of relative accumulation of the IPGE (ΣPPGE/ΣIPGE＜1). Therefore, copper-rich ore, massive sulphide ore and vein interpenetration ore are formed in the late stage of magmatic evolution, and the contact relationship shows that emplacement of massive sulphide ore precedes copper-rich ore. Based on comparison of sideronitic ores’ PGE, Cu and Ni features between II-2 and II-1 orebodies, parental magmas of these two ore bodies belong to high-MgO type topicritic basalt formed by moderate partial melting of mantle and have the same source characteristics. PGE distribution patterns, PGEs differentiation situation, Cu/Ni and Cu/Pd, and the relationship of Ir and Ru, Rh, Pt and Pd of sideronitic ores were used to study the parental magma of II-2 and II-1 orebodies in terms of sulfide liquid-silicate system and MSS-sulfide liquid system, it might be possible to deduce that sulfides of the two ore bodies are successively separated from the parental magma, with out-of-step evolution features. Based on the studies on genchemical section of II-2 orebody, the contour map of longitudinal section projection and XOY plane projection of Ni and Cu grade, the separation processes of the two orebodies sulfide occur in deep-seated magma chamber and intrude the pre-existing tensional rupture through different magma conduit systems, forming II-2 and II-1 orebodies.
Key words: Jinchuan; Cu-Ni sulfide deposit; platinum-group elements; magma conduit; metallogenic process
