大西洋中脊赤狐热液区热液产物矿物学特征及其地质意义

Mineralogical and geological significance of hydrothermal products:A case from the Chihu hydrothermal field,South Mid-Atlantic Ridge

赤狐热液区是2019年中国在南大西洋中脊23.7°S发现的一个位于拆离断层上盘的热液区。本文利用光学显微镜、电子探针、TerraSpec Halo矿物鉴别仪和XRD粉晶衍射仪,对该区热液产物进行了矿物学和矿物成分研究。结果表明,赤狐热液区热液产物可分为硅质硫化物、硅质矿化角砾岩和碳酸盐质矿化角砾岩。这些产物均由不等量蚀变岩石碎屑、团块状硫化物角砾、细粒浸染状硫化物以及硅质和碳酸盐质胶结基质组成。团块状硫化物与细粒浸染状硫化物之间在矿物组合、结构构造和矿物成分上的差异指示该热液区可能经历了多个喷发周期,蚀变岩石碎屑的复杂性和多样性指示该热液区除了基性源岩外,还可能受到超基性源岩影响。

The Chihu hydrothermal field is a mineral occurrence related to a detachment fault structure.It was discovered in 2019 at 23.7°S of the southern mid-Atlantic ridge.The detachment fault is believed having important influences on the hydrothermal activity and mineral deposition of the field.In this paper,mineralogy and mineralogy chemistry studies are conducted for the hydrothermal products by means of transmission-reflection microscope,Terraspec Halo mineral discriminator and X-ray diffraction(XRD).The results suggest that the hydrothermal products are mainly composed of siliceous sulfides,siliceous mineralized and carbonate mineralized breccias consisting of altered rock fragments,massive sulfide breccia,fine-grained disseminated sulfide,and siliceous and carbonate cemented matrix.The difference in mineral composition,structure and mineral composition between massive sulfide and fine-grained disseminated sulfide indicates that the hydrothermal area may have experienced multiple times of eruption cycles.The complexity and diversity of altered rock fragments suggest that in addition to basic source rocks,this hydrothermal field may also be affected by ultrabasic source rocks.