西秦岭铀成矿带中志留系硅岩灰岩的成因研究

Lithogenesis Research of Silicalite and Limestone of Silurian in the Uranium Metallogenic Belt in Western Qinling

通过大量的剖面测制和室内分析，从岩石的地质产状、岩石学及地球化学特别是稀土元素地球化学方面研究了西秦岭铀成矿带中硅、灰岩的成因。原始沉积的泥晶灰岩和球粒泥晶灰岩沉积于水下高地较低能环境，球粒主要为粪球粒及少量硅质生物体。硅岩具生物化学沉积（Ｉ类）和由灰岩硅化（交代）成因（Ｉ类）两种成因类型，它们在地质产状、结构构造、常量元素及稀土元素地球化学等方面都存在显著差异。

The genesis of Silurian silicalite and limestone was studied from the geological setting,lithology and geochemistry especially the REE geochemistry in this paper based on many measured sections and laboratory analyses. The sedimentary environment of micrite limestone and pellet micrite limestone was the upland under deeper water with low water energy. The pellets were composed of organism pellets and radiolarite.There are two types of silicalite:the organic deposit (type I) and the silicalite silicanzed from limestone (type II).They are obviously different in the geologic setting,texture and structure,geochemistry of rare element and REE etc. As sedimental environmental model was proposed for early Silurian in the Uranium metallogenic belt in Western Qinling based on the synthetical study.