吉林红旗岭地区岩浆铜镍硫化物矿床的硫化物饱和机制

The attainment of sulfide saturation of mantled-derived magma by crustal contamination is a key factor for the formation of magmatic Ni-Cu sulfide deposits. The different ways of magma achieving sulfide saturation may have influences on the sulfide contents in the intrusions, but its mechanism remains a controversial issue. Numerous Triassic mafic-ultramafic intrusions occur in the Hongqiling region. Only one large and several medium-small Ni-Cu sulfide deposits were found in these intrusions, whereas more of the intrusions are sulfide barren. It provides a good opportunity to study the different mechanisms of sulfide saturation in different types of mineralized intrusions. Taking three mineralized intrusions and one sulfide barren intrusion in Hongqiling region as the research object, we are going to carry a project that is aimed to investigate the S, C, Sm-Nd, and Re-Os isotopic compositions of the intrusion, the direct wall rocks, and sedimental strata in the region. Combining the S and Re-Os data, the results will help us to understand whether the externally sulfur must be added or not, in the genesis of large Ni-Cu sulfide deposits. The final goal is to identify which strata in the Hongqiling region (not only the direct wall rocks) served as the major crustal assimilation compounds, trigging sulfide saturation of mantle-derived magma. This project will provide theoretical support to mineral exploration in Hongqiling region.

幔源岩浆遭受地壳混染，达到硫化物饱和是形成铜镍硫化物矿床的关键。由于岩浆达到硫化物饱和的方式不同，不同岩体的矿化程度会有所差异，但具体机制有待探讨。吉林红旗岭地区广泛出露三叠纪镁铁-超镁铁质岩体，其中只赋含一个大型矿床、少数几个中-小型矿床，其它大多不含矿。这为研究矿化程度不同的岩体及其硫化物饱和机制的差异问题提供了很好的天然窗口。本项目拟选取红旗岭地区三个含矿程度不同的岩体和一个不成矿岩体作为研究对象，对岩体、岩体直接围岩和区域沉积地层开展S和C同位素、Sr-Nd和Re-Os同位素研究，探讨不同含矿岩体的硫化物饱和机制和成矿差异性的控制因素。结合S同位素和Re-Os同位素，查明地壳S加入与形成大型铜镍硫化物矿床的关系。最终从整个区域地层的角度分析地壳混染源（不仅仅是岩体的直接围岩），以期查明区域上导致岩浆硫化物饱和的地层单元，为矿产勘查工作提供理论依据。

造山带中产出的岩浆铜镍硫化物矿床形成机制的研究，对于岩浆矿床成矿理论和找矿勘查具有重要的理论意义和应用价值。本项目选取中亚造山带最东端红旗岭-漂河川地区的含矿岩体、岩体直接围岩和区域沉积地层为研究对象，开展S、C和Sr-Nd同位素研究，探讨含矿岩体的硫化物饱和机制，并利用岩相学观察结合3D成像扫描技术，讨论了漂河川4号岩体硫化物熔体的运移机制。本文的主要结论是：1.红旗岭-漂河川地区镁铁-超镁铁质岩体的母岩浆发生地壳混染，最可能的对象为二叠纪板岩和片麻岩；2..红旗岭-漂河川地区岩浆铜镍硫化物矿床成矿所需的硫主要来自于地幔；3.地壳S和Re-Os的赋存相不一样，导致了矿石S同位素和Os同位素发生解耦；4.地层中还原性有机C的加入改变了岩浆氧逸度，是本地区铜镍硫化物矿床母岩浆达到硫化物饱和的主要机制；5.漂河川4号岩体球状构造矿石的形成是因为硫化物熔体和硅酸盐熔体液相线温度的差异