塔里木克拉通东北缘二叠纪镁铁质岩浆氧化物与硫化物成矿条件对比

塔里木克拉通东北缘坡北、磁海等地二叠纪幔源岩浆活动形成了镍钴硫化物矿床和铁钴氧化物矿床，两者赋矿镁铁 超镁铁岩体的年龄相近(290~260 Ma)，主、微量元素和Sr Nd Hf同位素组成相似，分配系数接近的微量元素比值分布于相同趋势线，揭示两者岩浆源区相同，可能为俯冲板片流体交代的亏损地幔或软流圈地幔。两类矿床镁铁 超镁铁质岩中Co与Ni含量正相关，Co主要富集在基性程度高的岩石中；块状硫化物与磁铁矿矿石中Co与Ni相关性差，Co和Ni具有不同的富集机制，Co热液富集作用明显。北山镁铁 超镁铁杂岩体是地幔柱相关软流圈上涌，诱发俯冲板片交代的亏损岩石圈地幔发生部分熔融，形成的高镁母岩浆演化过程中经历壳源混染、硫化物饱和富集镍钴形成铜镍钴硫化物矿床，富铁母岩浆氧逸度高、富水，岩浆分离结晶磁铁矿、叠加热液作用富集钴，形成铁钴氧化物矿床。

Comparison of metallogenic conditions of Permian mafic oxide and sulfide deposits in the northeastern margin of Tarim craton, China

The Permian mantle derived magmatism had formed Ni Co sulfide deposits and Fe Co oxide deposits in the Pobei and Cihai area of the northeastern margin of Tarim craton. The mafic ultramafic complexes hosting Pobei Ni Cu Co sulfide deposit, Cihai Fe Co oxide deposit were formed in the same period (260~290 Ma). The ore bearing mafic ultramafic complexes show similar major trace elements petrogeochemical and Sr Nd Hf isotopic signatures, the trace element ratios with close partition coefficient are plotted on the same trend lines, indicating a simillar mantle magmatic source. The mantle magmatic source could be depleted mantle metasomatized by subducted slab fluids and superimposed by asthenosphere mantle. The mafic ultramafic rocks of both Cu Ni Co sulfide deposits and Fe Co oxide deposits display a strong positive correlation between Ni and Co contents, but the magnetite ore shows weak correlation between Co and Ni contents. Co is mainly enriched in ultramafic rocks in mafic ultramafic complexes. The magnetite ores have different Co Ni enrichment mechanisms from Ni Co sulfide ores, cobalt minerals as cobaltite etc. occurs at the edge or fissure of pyrrhotite, suggesting an obvious hydrothermal enrichment. The Early Permian mafic ultramafic complexes in the northeastern margin of Tarim craton could be derived from the different degree of partial melting of metasomatic depleted mantle, which was caused by asthenosphere upwelling associated with mantle plume. Ni Co sulfide deposits were formed through sulfide saturation of high MgO magma caused by crustal contamination. Low degree of partial melting of depleted mantle with subduction metasomatism had formed in the oxygen fugacity parent magma with high iron and water contents, which crystallized and formed magnetite ore, and hydrothermal process caused cobalt enrichment to form Fe Co oxide deposits.