玉石沟铬铁矿床产于北祁连蛇绿岩型超镁铁岩中，可分为产于堆积超镁铁岩中的堆积铬铁矿床和产于地幔橄榄岩中的豆荚状铬铁矿床两种类型。堆积铬铁矿床由玄武岩浆分离结晶作用形成，位于辉长岩下约２０ｍ处的纯橄岩或辉石岩中；豆荚状铬铁矿床由地幔岩部分熔融作用形成，产于地幔橄榄岩上部或顶部基性程度最高的纯橄岩或纯橄岩－斜辉辉橄岩杂岩带，位于堆积杂岩下约２００～１７００ｍ范围内。 The Yushigou chromite deposit is produced in the North Qilian ophiolite-type ultramafic rock and can be divided into the accumulative chromite deposit produced in the accumulative ultramafite and the podiform ferrochrome produced in the mantle peridotite Two types of deposits. The bedded chromite deposit is formed by the separation and crystallization of basalt magma and is located in dunite or pyroxenite about 20m below the gabbro. The podiform chromite deposit is formed by the partial melting of the mantle rock and is produced in the upper part of the mantle peridotite Or dacite or dipsite-mafic complex with the highest basicity at the top, located within the range of 200-1700 m below the accumulated complex.