【作者】 柴凤梅；

【导师】 毛景文； 张招崇；

【作者基本信息】 中国地质大学（北京） ， 矿物学、岩石学、矿床学， 2006， 博士

【摘要】 近年来,随着全球对镍需求量的不断增加,与岩浆型Ni-Cu-(PGE)硫化物矿床有关的镁铁-超镁铁质岩体的研究得到了重视。同时,镁铁-超镁铁质岩石对于研究壳幔相互作用、地球深部动力过程等具有重要的意义。新疆北部是我国,也是全球岩浆型Ni-Cu-(PGE)硫化物矿床分布最密集的地区之一,该区位于中亚造山带南部边缘。研究这些与岩浆型Ni-Cu-(PGE)硫化物矿床有关的镁铁-超镁铁质岩体的成因,对造山带内的岩浆型Ni-Cu-(PGE)硫化物矿床的找矿勘查活动以及研究中亚造山带的形成和演化具有重要的意义。前人对这些岩体的成因研究较为薄弱。本文选择位于不同构造单元的白石泉(中天山)、黄山东(东天山)和喀拉通克(阿尔泰山南缘)镁铁-超镁铁质岩体进行系统的岩石学和地球化学研究,探讨三个典型岩体的岩石成因,以期为研究区的岩浆型Ni-Cu-(PGE)硫化物矿床的找矿提供线索,同时为后造山作用过程提供约束条件。目前取得的主要认识有:1.白石泉、喀拉通克、黄山东镁铁-超镁铁质侵入体是造山后碰撞阶段岩浆活动的产物,它们具有相同的地球动力学背景。2.三个岩体的岩石组合及含矿岩石类型不同,但造岩矿物特征大体相同。白石泉岩体与黄山东岩体包括超镁铁质与镁铁质岩石,而喀拉通克岩体缺乏超镁铁质岩石。前两个岩体的主要含矿岩石为橄榄岩与辉石岩,喀拉通克岩体主要为苏长岩含矿。3.三个岩体均具有大离子亲石元素(LILE)和轻稀土元素(LREE)富集,高场强元素(HFSE)亏损的微量元素特征。均具有低的Sr同位素初始比值,正的εNd值和低的放射性成因Pb,高于地幔的O同位素特征。白石泉岩体与黄山东岩体均具有极低的铂族元素成分,并且铂族元素主要受结晶分异作用的影响。4.三个岩体的母岩浆性质相似,均为含有水的高镁拉斑玄武岩。但是它们的母岩浆中MgO的含量有别。5.三个岩体的源区相似,岩浆的演化特征相近。它们的源区均为受到俯冲洋壳物质混染的软流圈地幔。它们的原始岩浆均经过了两个阶段的演化。第一阶段为橄榄石的结晶与硫化物的熔离阶段,第二个阶段为富含橄榄石与硫化物“晶粥”的就地分异阶段。地壳物质混染和橄榄石的结晶是岩浆中S饱和的主控因素。关键词:岩浆型Ni-Cu-(PGE)硫化物,镁铁-超镁铁岩,地球化学,新疆北部更多还原

【Abstract】 Recently, the increased demand of Cu, Ni, Pt and Pd, etc., greatly promotes the research onthese mafic-ultramafic rocks associated with magmatic Ni-Cu-(PGE) sulfide deposits.Furthermore, the mafic-ultramafic rocks can be an important object to understand crust-mantlemagmatism and the process of continental geodynamics.In the past twenty years about 20 magmatic Ni-Cu-(PGE) sulfide deposits and occurrenceshave been discovered in northern Xinjiang, China. These Ni-Cu-(PGE) sulfide deposits, relatedto mafic-ultramafic intrusions, are one component of the large scale metallogenesis duringpost-collisional tectonism in Late Carboniferous–Early Permian within the Central AsianOrogenic belt. To understand the origin of these Ni-Cu-(PGE)-bearing mafic-ultramaficintrusions is potentially important not only to the guidence exploration on Ni-Cu-(PGE) sulfidedeposits in orogenic belt but also to the study on the evolution of the CAOB. However, theprevious studies were focused on these Ni-Cu-(PGE) deposits, with little attention to the originand evolution of these mafic-ultramafic intrusions. Thus, three intrusions, including Baishiquanintrusions in Central-Tianshan Block, Huangshandong intrusions in Jueluotage orogenic beltand Kalatongke intrusions in Altay orogenic belts, are chosen for objects in this dissertation.The characteristics of petrology, mineralogy and geochemistry on these intrusions areinvestigated for the purpose as follow: (1) to determine the petrogenesis and evolution of theserocks;(2) to provide some clues for Ni-Cu-(PGE) sulfide ore genesis;(3) to discuss the mantlesource regions to understand the geodynamic processes;(4) to compare these characteristicsand find the reasons of similarities and differences, to discuss the regularities of formation forthe magmatic Ni-Cu-(PGE) sulfide deposits in orogenic belt. (5) to provide some constraints forthe process of post-collisional tectonism.On the basis of the systematically research on three mafic-ultramafic intrusions hostingNi-Cu-(PGE) sulfide deposits in the CAOB, some conclusion has been drawn:(1) The Baishiquan, Huangshandong and Kalatongke mafic-ultramafic intrusions occurredin the postcollisional setting and were related to lithospheric delamination and magmaticunderplating.(2) These intrusions have different rock assemblages and host rocks for Ni-Cu deposits,although the petrogenetic minerals are same. The Baishiquan and Huangshandong intrusionsare composed of peridotite, pyroxenite, hornblendite, troctolite, norite, gabbro and diorite, andthe Kalatongke intrusions consist of norite, gabbro-norite and biotite diorite. The peridotite andpyroxenite are the main host rocks for the Cu-Ni ores in the Baishiquan and Huangshandongintrusion, while norite in Kalatongke intrusion.(3) All of the intrusions are characterized by enrichment in large ion lithophile elements(LILE, e.g., Rb, Sr, K, U, Pb and Th) and light rare earth elements (LREE), depletion in highfield strength elements (HFSE, e.g., Nb, Ta, Ti and P) in relative to primitive mantle andMORB. Their Sr, Nd, Pb and O isotope data suggest a mixture of depleted asthenosphericmantle with MORB-like isotopic signature and subducted slab with EMⅡisotopic signature.The absolute PGE abundances are low, and the PGE is mainly affected by crystallizationdifferentiation in the Baishiquan and huangshandong intrusions.(4) The parental magmas are high-magnesium tholeiite, but have different contents in MgO.(5) The primitive magmas are derived from the asthenospheric mantle contaminated bypreviously subduction material. The primary magma with high-magnesium componentsexperienced two stages evolution. Olivine is the main fractionated phase in first stage of magmaevolution, and sulfides segregated from the silicate magma. The parental magma, which isolivine-and sulfide-laden crystal mush, entered the high-level magma chamber anddifferentiated in situ to form these intrusions. The sulfides segregation can be ascribed to thecrust contamination and the olivine crystallization.更多还原