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甘肃永登何家圈一带出露的中奥陶世地层,下部为火山岩,上部为板状硅质岩和灰岩。在火山岩剖面中,下部为巨厚的变质辉石安山岩、安山玢岩及杏仁状安山岩;上部为安山质火山角砾岩(安山质自碎角砾熔岩、安山质熔角砾岩)和安山质岩屑凝灰岩。火山碎屑岩呈透镜状或似层状,与围岩产状基本一致。火山碎屑岩向板状硅质岩过渡的地带是胶磷矿赋存的部位,数量可观。矿石中P_2O_5含量一般为
The middle Ordovician strata exposed in Hejian circle of Yongding, Gansu Province are volcanic rocks in the lower part and plate-shaped cherts and limestones in the upper part. In the volcanic rock profile, the lower part of the thick metamorphic pyroxene andesite, andesite and almond-shaped andesite; the upper part of the Andesite volcanic breccia (Anshan self-broken breccia lava, Andean breccia ) And andesitic lithic tuff. Pyroclastic rocks were lenticular or lamellar, basically consistent with the surrounding rock-like. The volcanic clastic rocks transition to platy chert is the site where phlogoidite occurs, with a considerable number. P2O5 ore content is generally