西南印度洋中脊53°E百神海山表层沉积物物源特征及其对热液活动的指示

Characterization of surface sediments and their indication of hydrothermal activity on 53°E Baishen Seamount,southwest Indian Ridge

超慢速扩张洋中脊具有形成大型海底多金属硫化物堆积体的潜力,其中拆离断层控制的热液区常具规模大、富Cu、Au等特征。百神海山位于超慢速扩张西南印度洋脊Gallieni转换断层内角处,发育拆离断层构造,具有产出热液活动的有利构造条件,但一直未确认该区域是否存在热液活动。本研究对该区4站表层沉积物开展了主微量、稀土元素和微区地球化学分析,结果显示研究区沉积物中含丰富的超基性岩碎屑,并可能有玄武岩角砾的影响。沉积物中的有孔虫壳体富集Fe、Mn等热液元素,表明研究区受到热液组分的影响。根据富集特征的空间分布,可以推断热液活动喷口的位置靠近研究区的A3站位。这一综合分析深化了对该海山沉积物物源的认识,同时为超慢速洋中脊热液识别或找矿提供了有力线索。

Ultra-slow spreading mid-ocean ridges have the potential to form large seafloor polymetallic sulphides,in which hydrothermal zones controlled by detachment faults are often characterized by large-scale,Cu-rich and Au-rich zones.Baishen Seamount is located at the inner corner of the Gallieni Transform Fault on the ultra-slow spreading southwest Indian Ridge,and the development of the detachment fault structure has favorable tectonic conditions for hydrothermal activity,but it has not been determined whether there is any hydrothermal activity in this area.In this paper,primary trace and rare earth elements and in situ microzonation geochemical analyses were carried out on the surface sediments at four stations in the area,and results show that the sediments in the study area are rich in ultramafic clasts and may have been probably influenced by the basaltic breccias.Foraminiferal shells in the sediments are enriched in hydrothermal elements such as Fe and Mn,indicating that the study area was influenced by hydrothermal components.Based on the spatial distribution of enrichment features,it can be inferred that the probable location of the hydrothermally active vents is close to station A3 in the study area.This comprehensive analysis deepens the understanding of sediment source of this seamount and provides strong clues for hydrothermal identification or mineral searching in the ultra-slow mid-ocean ridge.