摘要
喀拉通克铜镍矿床位于准噶尔板块北缘,矿区主要矿体赋存于Y1-Y3号岩体中。矿石构造类型为致密块状和浸染状两大类,其中前者与后者呈贯入接触,不同浸染状类型之间为过渡关系。岩石和矿石的PGE总量偏低,且以PPGE为主,IPCE含量较低。整体上岩石中的PGE含量显示随基性程度降低而变小。矿石中的PGE含量随硫化物含量增加增大,显示PGE主要分布于硫化物熔离形成的物相中。100%硫化物计算后,矿石PGE含量平均仅为573×10^(-9)。各岩体中浸染状矿石PGE组成并无明显差异;岩石和矿石具有相似的PGE分配模式,均属于Pt-Pd配分型。岩石Ni/Cu-Pd/Ir关系以及岩石地球化学资料显示,形成喀拉通克岩体的初始岩浆为MgO含量较高的玄武质岩浆,属于PGE不亏损的岩浆。基于PGE不亏损的大陆拉斑玄武岩初始岩浆推算,喀拉通克矿床母岩浆明显亏损PGE,而深部硫化物熔离可能是导致母岩浆PGE亏损的主要原因。岩石和矿石Pd/Pt比值总体特征,岩石Cr与Ni、Ir、Ru和Rh相关性,以及硫同位素和岩石学资料分析表明,初始岩浆在地壳深部发生的橄榄石、铬铁矿等矿物的分离结晶作用,可能是促使硫过饱和与深部熔离的主要因素。IPGE与PPGE分异特征及其相关分析,结合矿床宏观地质特征,推断该矿床浸染状矿的成矿作用经历了初始岩浆(PGE不亏损)→橄榄石等矿物分离结晶→硫化物深部熔离→成矿母岩浆(PGE亏损)→上侵并结晶分异的成矿过程。块状矿则可能是这一过程中PGE亏损的成矿母岩浆相对滞后熔离形成的硫化物熔体贯入的结果。
Kalatongke Ni-Cu Sulfide deposit, which occurring in the northern margin of the Junggar terrane, northern Xinjiang, NW China, three of 11 small mafic intrusions (#1, #2 and #3) are the main economic Ni-Cu sulfide ore bodies. The ore is comprised of disseminated sulfides ( including weakly-disseminated and heavily-disseminated) and massive sulfides, in the former they have transition relationship, but the latter has penetration contact relationship with the former. The total concentrations of PGE in rock and ore samples are low, their dominant elements are PPGE, generally decrease with basic degree decrease in rocks and increase with sulfide contents increase in ores, suggest that PGE distribution in the deposit is mainly controlled by ore phases derived from sulfides segregation. On the basic of 100% sulfide recalculated, the average concentrations of total PGE concentrations in ores are 573 x 10(-9). The composition of the total PGE show no notable difference among the disseminated of all intrusions. Rock and ore samples have similar mantle-normalized PGE patterns with relative enrichment of Pt and Pd. The diagram of Pd/Ir against Ni/Cu, and geochemistry of rocks reveal that primary magma of Kalatongke is basaltic magma with high MgO content, which is undepleted in platinum group element. Assuming the primary magma is similar to the continental tholeiite, simulanting result reveals that the parental magma visibly depleted PGE, at the same time, Ir depleted more than Pt and Pd, owing to the sulfide segregation in the deep crust. The Pd/Pt ratios of rocks and ores, binary variations of Cr versus Ni, Ir, Ru and Rh, and S isotope combining with petrology show that the fractionation of olivine and chromite is likely the main factor leading to sulfur saturation and segregation. The diversity between IPGE and PPGE of different type ores, its pertinency linking and the macroscopical geological fact, we conclude that the disseminated ores come from the undepleted initial magma, then the olivine and chromite crystallization and segregation and sulfide segregation in the deep crust, resulting in the parental magma depleted in PGE, in the end, the crystal-bearing magma ascend and intrude the present level in the crust. But the massive ore maybe derived from the sulfide melt which laterly segregated from the parental magma depleted in PGE, and then inject into disseminated ores.
出处
《岩石学报》
SCIE
EI
CAS
CSCD
北大核心
2009年第4期832-844,共13页
Acta Petrologica Sinica
基金
国家自然科学基金重点项目(40534020)
中国地质调查局地质大调查项目(1212010630508)资助成果
关键词
铂族元素
成矿过程
地球化学
铜镍硫化物矿床
喀拉通克
Platinum-group element
Mineralization process
Geochemistry
Cu-Ni sulfide deposit
Kalatongke
