concealed coalfield

例句：

1. 1. The mine is located in a concealed coalfield, making it difficult to access.
   这个矿位于一个隐蔽的煤田，难以到达。
2. 2.The discovery of this concealed coalfield has sparked interest in alternative energy sources.
   这个隐蔽的煤田的发现激发了对替代能源的兴趣。
3. 3. Due to the concealed nature of the coalfield, exploration efforts have been limited.
   由于煤田的隐蔽性质，勘探工作受到了限制。