四川若尔盖北部寒武系太阳顶群硅质岩的热水沉积成因

HYDROTHERMAL SEDIMENTATION IN GENETIC OF SILICAUTE IN CAMBRAIN TAIYANGDING GROUP IN THE NORTHERN PART OF RUOERGAI SICHUAN

四川若尔盖北部寒武系太阳顶群为金矿矿源层,硅质岩为其中的主要组成部分.研究矿源层的成因,硅质岩成因是关键所在.硅质岩已遭受变质成为微晶石英岩,以块状为主.岩石中均含有不等量的有机碳.岩石中还保留了较多的沉积组构.主要化学成分以SiO_2为主,结合微量元素及稀土元素等综合研究表明,太阳顶群硅质岩为热水沉积成因,硅可能来自下伏及深部地层.

Cambrian Taiyangding Group, located in the northern part of Ruoergai in Sichuan province, is an important gold-bearing formation. Various evidences suggest that the Taiyangding group is the sourcebed gold deposits in this araa. Of the consistion rock units of carbonaceous silicalites and carbonaceous in Taiyangding group, the origin of the silicates is a key point in understanding the origin of the gold source bed in this area. Under low-rank metamor-phism, the silicate appears to be massive structure on the outcrops and contains varied amount on carbonaceous materials. Several kinds of sedimentary fabrics, such as laminated structure, rhythmic bedding, spherulitic structure, autobreccia structure, porous structure, colloform structure, are observed in the silicalites. Based on the comprehensive researches of petralogy, chemical composition, trace elements and REE of silicalites, it was concluded that the silicalite is the product of hydrothermal sedimentation in genetic.