内蒙白云鄂博铁矿床中磁铁矿和赤铁矿的氧同位素组成

白云鄂博矿床分布在内蒙地轴北部边缘的过渡带。含矿岩系为元古代海相沉积碳酸盐、碎屑岩建造,主要由石英岩、白云岩和板岩组成,其中白云岩是矿体围岩。 矿床受东西向向斜构造控制。向斜以北为一大背斜构造,沿轴部被断层破坏,出露有古老的片麻岩和片岩。向斜以南的背斜构造轴部有海西期黑云母花岗岩侵入,使背斜构造轴部遭受破坏。

OXYGEN ISOTOPE COMPOSITION OF MAGNETITE AND HEMATITE IN BAIYUN EBO IRON DEPOSIT, INNER MONGOLIA

On the basis of the paragenesis of minerals and structure, the iron ores in Baiyun Ebo deposit can be divided into magnetite ore and hematite ore. Magnetite ores include dolomite type, fluorite type, riebeckite type, biotite type, massive type and soda pyroxene type. δO¹⁸ of magnetite in dolomite type(+1.3‰), fluorite type(+1.8‰), and riebeckite type(+1.8‰)is lower than that in biotite type(+2.9‰)and higher than those in massive type(+0.2‰)and soda pyroxene type(-0.3‰). They are products of sedimentary or sedimentary-metamorphic processes. Massive type magnetite and soda pyroxene type mabnetite are the products of hydrothermal metasomatism of dolomite type magnetite. Their δO¹⁸ are relatively low. Hematite in Baiyun Ebo has the lowest δO¹⁸(-3.2‰)and has characteristics of sedimentary origin. Therefore, Baiyun Ebo iron deposit has multi ple origins including sedimentary, metamorphous and hydrothermal metasomatic origin.