湘西沃溪Au-Sb-W矿床中富放射成因锶的成矿流体及其指示意义

The Ore-forming Fluid with a Marked Radiogenic ^(87)Sr Signature From the Woxi Au-Sb-W Deposit and its Significant Implications

研究表明 ,湘西沃溪Au Sb W矿床白钨矿的Sr含量很高 ,为 14 5 5～ 6 810 μg g ;87Sr/ 86 Sr为 0 .74 6 75～0 .75 0 0 3,明显不同于国外金矿中的白钨矿 ,表现出显著富放射成因锶。沃溪矿床的成矿流体为一种显著富放射成因锶的热水溶液 ,暗示成矿流体不可能是类似于现代大洋中脊喷出的热液或古海水 ,其矿床成因并非前人所认为的“海底热泉 (卤水 )沉积成因”或“海底喷流沉积成因”。矿床中这种显著富放射成因锶的成矿流体 ,很可能是热水溶液对下伏古老基底淋滤或是对元古界赋矿地层中的碎屑岩选择性优先淋滤所致。

Strontium isotope geochemistry of sc he elites from Woxi Au-Sb-W deposit, Western Hunan was systematically studied. Sr concentrations in scheelites are usually high, varying in the range of 1455-68 10 μg/g. The strontium isotope compositions varied between 0.74675 and 0.75003, which are obviously of radiogenic origin compared with other scheelites from go ld deposits reported by the foreign literatures. The ore-forming fluid from the Woxi Au-Sb-W deposit is characterized by the marked radiogenic 87 Sr -ri ch, which implies that the mineralizing fluid is other than the hydrothermal sol utions vented from modern ocean ridge or paleo-seawater, and that the Woxi depo sit shouldn't be classified into the 'seafloor hydrothermal spring sedimentary origin' or 'seafloor sedex sedimentary origin' as previously expected. The m arked radiogenic 87 Sr-rich fluid for the Woxi deposit probably result ed e ither from the preferential leaching of Rb-rich minerals in the Proterozoic roc ks or from the leaching of the underlying older continental crystalline basement by the hydrothermal solution.