【作者】 王建中；

【导师】 钱壮志；

【作者基本信息】 长安大学 ， 矿物学、岩石学、矿床学， 2010， 博士

【摘要】 中亚造山带是世界上重要的成矿带,也是铜镍岩浆硫化物矿床发育的成矿带之一。其中,喀拉通克铜镍硫化物矿床是该成矿带的典型矿床。该矿床成矿岩体小,岩体基性程度相对低,矿床规模大,工业矿体分布较为集中,矿石品位高,从而为研究该类矿床的成因提供了有利条件。论文选择喀拉通克铜镍硫化物矿床为对象,通过岩石学、矿物学、PGE地球化学以及Nd、Sr、Pb、Os同位素等的分析测试,对喀拉通克矿床的成矿作用和成矿过程进行研究,探讨了硫化物熔离机制、铂族元素的赋存规律、铂族矿物成因和同位素体系间“脱耦”等问题,建立了成岩成矿模式。并通过研究喀拉通克矿床的铂族元素、铜、镍的特征和分布规律,综合对比喀拉通克、金川、黄山东、白马寨和Voisey’sBay铜镍硫化物矿床的铂族元素特征,对喀拉通克矿床的成矿潜力进行分析,取得的主要进展如下：(1)利用ICP-MS分析测试了岩石、矿石的PGE含量,并对铂族矿物(PGM)进行了电子探针分析,分析数据丰富了喀拉通克铜镍矿床的研究资料。(2)研究了铂族矿物的粒径、寄主矿物等微观特征,并通过质量平衡计算、相图分析探讨了该矿床铂族矿物的成因和形成过程,不仅为铂族元素选冶提供了第一手资料,而且为成矿作用和铂族元素富集规律研究提供了矿物学依据。(3)相似的铂族元素配分曲线和大多数硫化物Co/Ni比值小于1,表明该矿床Y1-Y9岩体群和G21岩体来自同一岩浆系统,为同源岩浆演化的产物,这与岩石主量元素提供的成因信息一致。(4)区域构造、岩石组合、年代学及岩石地球化学研究表明,喀拉通克矿床形成于早二叠世后碰撞伸展阶段的拉张环境,岩浆源区由被消减板片交代的地幔楔物质和软流圈地幔物质组成,且以软流圈地幔物质为主。岩石圈伸展减薄,软流圈物质上涌并发生减压部分熔融,在软流圈物质加热下地幔楔发生14%的部分熔融,产生铂族元素不亏损的初始岩浆。(5)PGE特征显示喀拉通克成矿母岩浆为高镁拉斑玄武质岩浆,组成类似于金川母岩浆,为携带大量硫化物熔体和橄榄石等矿物的“晶粥”。在深部岩浆房,初始岩浆局部混染少量地壳物质,橄榄石、辉石和铬铁矿等矿物发生分离结晶作用,使得岩浆中硫化物达到饱和而熔离,少量硫化物预先熔离伴随橄榄石等的丢失,导致成矿母岩浆亏损铂族元素。(6)选择性混染导致岩浆中Os的含量和初始Os同位素组成增高,而对Sr、Nd、O同位素体系的影响较弱,造成Os、Sr、Nd、O同位素问发生“脱耦”。(7)喀拉通克矿床铂族矿物以Pt、Pd、Ni的碲化物、铋化物固溶体系列矿物为主,分布不均一,主要分布在磁黄铁矿、镍黄铁矿等硫化物中。粒径多在3-5um。矿物组合、质量平衡计算和相图分析显示,铂族元素主要以铂族矿物的形式存在,多数铂族矿物为岩浆熔离成因,个别矿物颗粒可能为热液叠加作用的产物。(8)喀拉通克矿床浸染状矿石宏观上具有最先成矿的特点,相似的Pd/Ir、Pt/Pd、Cu/Pd比值及IPGE与PPGE之间分异不明显,说明浸染状矿石是含矿岩浆较快速度冷凝与就地结晶分异的产物。而致密块状矿石宏观上晚于浸染状矿石侵位,具有岩浆通道贯入成矿的特征,IPGE比PPGE更加亏损,且IPGE与PPGE之间分异显著,这意味着硫化物熔体在深部岩浆房与更多的橄榄石、铬铁矿等矿物反应,而后贯入到构造破碎带,经历单硫化物固溶体分离结晶后形成块状矿石。(9)在考虑矿床成岩成矿大陆动力学背景的基础上,以成矿作用和深部成矿过程为核心,建立了喀拉通克铜镍矿床的成岩成矿模式。(10)喀拉通克、金川、白马寨、黄山东和Voisey’s Bay铜镍矿床均经历了深部硫化物熔离作用,硫化物熔离导致母岩浆亏损PGE,但对Ni和Cu而言可能起到预富集作用。因此,在目前的勘查深度内喀拉通克铜镍矿床的PGE成矿潜力有限,而铜、镍的成矿潜力较大。更多还原

【Abstract】 The Central Asian Orogen belt is an important metallogenic zone hosting many Ni-Cu magmatic sulfide deposits in the world. Kalatongke deposit is the biggest and representative one in Xinjiang, it is associate with small rock masses and lack of ultramafic rocks, which is charactered by concentrative industrial ore bodies with high tenor. All these provide some investigative advantages for the ore genesis of magmatic sulfide deposit. Kalatongke deposit was selected for detailed study on the base of petrology, mineralogy, PGE geochemistry, Nd, Sr, Pb and Os isotope geochemistry, focusing on the key issues of magmatic sulfide deposits:①the metallogenes and its deep process;②the factors controlling on the sulfide segregation, the relationship between crustal contamination and sulphide segregation;③what is the cause for the decoupling of the Sm-Nd-O and Re-Os isotopic systems. Systematically comparison for the characters of PGE between Kalatongke and the other ones such as Jinchuan, Baimazhai, Huangshandong and Voisey’s Bay deposit.were carried out, the characters and distribution regularity of PGE, Ni and Cu from Kalatongke deposit were studied, in order to analyse its metallogenic potential. The following are the main results:(1)The PGE content of rocks, ores and platinum-group mineral (PGM) from the Kalatongke Ni-Cu sulfide deposit, have been analyzed by the ICP-MS and electron microprob respectively, analytic results enriches the researchful data of Kalatongke Ni-Cu deposit.(2)The microcosmic characters such as grain scale and its hosting minerals have been researched. Studies on the oregenesis of PGM are performed using mass balance calculation and phase plots. All these provide not only first-hand data for PGE beneficiation, but also mineralogical evidence for research on the metallogenes and enrichment regularity of PGE.(3)The Kalatongke deposit has similar mantle-normalized pattern, and smaller Co/Ni ratio than the unity of most sulfides, showing that the rock bodies from Y1 to Y9 and G21 derived from the same magma system, it is consisted with the genesic information from the main oxides of rocks.(4)Petrogeochemistry, district rock assemblage, structure and chronology have proved that, Kalatongke sulfide deposit formed in the postcollisional extension setting at the early Permian. Its mantle source is composed of mantle wedge components matasomasised by the fluid from the subducting slab and aesethenosphere, aesethenosphere melt because of the decompression and underwell. Then, the mantle wedge melted by 14 percent degree and gave rise to a tholeitiitic basalt, which should be undepleted in platinum group element.(5)The characteristics of PGE suggest that Kalatong parental magma is likely of a high magnesium tholeitiitic basalt, and similar to that of the Jinchuan deposit, consisting of "crystal mushes" formed by accumulation of suspended olivine crystals and sulfide melt. Primary magma underwent minor crustal contamination to some extent locally in the stage chamber. Olivine, pyroxene and chromite crystallization is the main control factor resulting in the magma sulfur saturation and segregation, minor sulfide presegregation induced the parental magma depleted in platinum group element.(6)The select contamination would heighten the Os content and the initial Os composition, on the contrary, it has little influence on the Sr, Nd,O isotopic system resulting in decoupling of the Os and Sr, Nd,O isotopic due to the lower Sr、Nd、REE contents in sulfide.(7)PGM are predominated by the (Pt, Pd, Ni)-Te-Bi solide solution mainly closed in sulfide. Mineral assemblage, mass balance calculation and phase charts show that PGE are at large in PGM, most of which are from the magma segregation, individual one maybe come from the hydrothermal fluid.(8)The disseminated ores from the different ore body of Kalatongke deposit, which is the earliest mineralization than the massive ores in macro scale, have similar Pd/Ir、Pt/Pd and Cu/Pd ratio, imply that they have slight fractionation between the IPGE and PPGE due to the faster cooling and in situ crystallization and fractionation of the parental magma. On the contrary, for the dense massive ores with visible fractionation between the IPGE and PPGE, they have the mineralization characters injected in the magma conduit and more depleted in IPGE than PPGE. As suggest that the sulfide melt suffered more separation and crystallization of olivine and chromite in deep, then, the sulfid melt laterly injected the structure crash belt and came into being the massive ores, which consists of monosulfide solide solution underwent separation crystallization.(9)Mineralization mode focusing on the minerogenesis and deep mineralization process is established, on the base of continental kinetic setting of Kalatongke deposit. (10)Comparison for the characters of PGE among the five deposits mentioned above show that, they are all depleted in PGE due to minor sulfide presegregation event in deep, but it maybe play an import role for the mineralization of Cu and Ni.. So Kalatongke deposit has limited metallogenic potentiality for PGE, but has better capacity of Cu and Ni in the operational exploration depth.更多还原