摘要
金川铜镍矿床是中国最大的岩浆铜镍硫化物矿床。前人研究表明,金川矿床成矿过程存在较高程度的同化混染作用,但同化混染物质的源区以及促使岩浆中硫化物发生熔离的机制一直存在争议。笔者通过多硫同位素(δ^(34)S、Δ^(33)S)和Fe同位素(δ^(56)Fe)联合示踪金川矿床成矿过程可能混染的地壳物质,尤其是太古宙沉积岩中S对金川矿床中硫化物熔离作用的影响。金川矿床Ⅰ、Ⅱ矿区中硫化物Δ^(33)S值为-0.07‰~0.22‰,超出了幔源岩浆Δ^(33)S值的参考值(-0.06‰~0.06‰),且不同于矿床围岩混合花岗岩中黄铁矿Δ^(33)S值(-0.04‰~-0.08‰),表明金川成矿岩浆同化混染作用应发生在深部,与其直接围岩无关。Ⅰ、Ⅱ矿区中磁黄铁矿δ^(56)Fe值为-1.07‰~-0.33‰,计算表明与硫化物熔体处于平衡的母岩浆δ^(56)Fe值为-0.7‰,远低于正常的幔源玄武质岩浆范围。此外,正Δ^(33)S值的矿石中磁黄铁矿通常具有很低的δ^(56)Fe值,两者具有明显的负相关关系,表明金川母岩浆中硫化物熔离可能是由于同化混染太古宙沉积岩中黄铁矿所致。
The Jinchuan Ni-Cu deposit is the largest magmatic Ni-Cu sulfide deposit in China.Previous studies shown that there is a high degree of contamination in the mineralization process of the Jinchuan deposit,but the source of the contaminating material and the mechanism that causes the sulfide melt segregation from the magma are still controversial.In this paper,we use a combination of multiple S(δ^(34)S+Δ^(33)S)and Fe(δ^(56)Fe)isotopes to trace the contaminated crustal materials during the mineralization process of the Jinchuan deposit,especially the influence of sulfur in Archean sedimentary rocks on the sulfur saturation of the Jinchuan deposit.The Δ^(33)S value of sulfide minerals in the segment Ⅰ and Ⅱ of the Jinchuan deposit is from−0.07‰ to 0.22‰,which ex-ceeds the Δ^(33)S value of mantle-derived magma and is completely different from the Δ^(33)S value of pyrite(-0.04‰~-0.08‰)in the wall rock of the Jinchuan deposit,indicating that the contamination of the Jinchuan magma should occur at depth and have nothing to do with its direct wall rock.The δ^(56)Fe value of pyrrhotite in the Jinchuan deposit is from -1.07‰ to -0.33‰.Calculations show that the δ^(56)Fe value of Jinchuan parent mag-ma in equilibrium with the sulfide melt is−0.7‰,which is far lower than the normal mantle-derived basaltic magma range.In addition,pyrrhotite in sulfide ores with positive Δ^(33)S values usually has very low δ^(56)Fe values,and Δ^(33)S-δ^(56)Fe values have a significant negative correlation,indicating that the sulfide segregation in the Jinchuan parent magma may be due to the contamination of pyrite in Archean sedimentary rocks.
作者
段俊
Teuku Amrul Mahdi
王宁
徐刚
房明举
付易遥
贾天河
DUAN Jun;Teuku Amrul Mahdi;WANG Ning;XU Gang;FANG Mingju;FU Yiyao;JIA Tianhe(School of Earth Sciences and Resources,Chang'an University,Xi'an 710054,Shaanxi,China;PT.Sebuku Iron Laterite,Jakarta 14450,Indonesia;Shaanxi Mineral Resources and Geological Survey,Shaanxi Institute of Geological Survey,Xi'an 710068,Shaanxi,China)
出处
《西北地质》
北大核心
2025年第4期56-68,共13页
Northwestern Geology
基金
国家自然科学基金项目(U2444203、41802081、42473027)
陕西省自然科学基础研究计划项目(2023-JC-YB-224)
长安大学创新创业训练计划项目(S202410710300)联合资助。
