提出：①湘中地区中奥陶世锰矿是低磷、低铁、高碱度优质锰矿石；

That a: The Mn-deposits of Middle Ordovician Epoch in central Hunan were high grade Mn-ores with low-P, low-Fe and high basicity;

youdao

提出：①湘中地区中奥陶世锰矿是低磷、低铁、高碱度优质锰矿石；

That a: The Mn-deposits of Middle Ordovician Epoch in central Hunan were high grade Mn-ores with low-P, low-Fe and high basicity;

youdao