新疆喀拉通克铜镍硫化物矿床Y9岩体年代学与成岩成矿机制探讨

Tentative discussion on rock_forming and ore_forming mechanism of Kalatongke Cu_Ni sulfide deposit and chronology of Kalatongke Y9 intrusion

新疆喀拉通克是中国大型铜镍硫化物矿床中基性程度最低的,显示出罕见的Cu平均品位大于Ni平均品位。矿区划分为南、北2个岩带,南岩带主要为原生矿,北岩带主要为氧化矿。文章研究对象为北岩带中的Y9岩体,近年发现其下部存在原生矿石。通过单颗粒锆石SHRIMP测年,获得Y9岩体中辉长岩的结晶年龄为(287±4)Ma,与Y1岩体的成岩年龄〔(287±5)Ma〕一致,结合岩石地球化学和同位素地球化学特征,证明喀拉通克矿区南、北岩带具有同期同源岩浆演化的特征,岩浆源自亏损型地幔部分熔融与不含沉积物消减板片脱水物质的混合。研究认为喀拉通克铜镍矿床形成于亏损地幔在相对较高的氧逸度条件下低程度部分熔融,产生硫化物不饱和的岩浆,岩浆源区相对富水和较高的氧逸度,原始岩浆具有较高的钛含量,具有富碱亲合性。

The Kalatongke large-sized Cu-Ni sulfide deposit is hosted by mafic intrusion, and the sulfide ores are characterized by unusual copper grades which are higher than nickel grades. The mining area used to be divided into northern and southern belts. Previous exploration indicated that the intrusions in the northern belt only host oxidized ores. However, original Ni-Cu sulfide orebodies were discovered recently in the Y9 intrusion in the northern belt. The zircon crystals separated from the Y9 gabbro have an age of （287 ± 4） Ma by SHRIMP U-Pb dating in this study, which is similar to the age of Y1 intrusion （ （287 ± 5） Ma）. In combination with the rock geochemical and isotopic geochemical data, it is concluded that the northern and southern belts experienced the same homologous magma evolution. The primary magma was derived from partial melting of depleted mantle, which experienced mixture of dehydration substance from subducted slab. Studies show that the magma source of the Kalatongke Cu-Ni sulfide deposit is characterized by rich water and high oxygen fugacity, and the primary magma might have come from depleted mantle through low degree partial melting, thus belonging to sulfide unsaturated magma characterized by fairly high titanium content and alkali-rich affinity.