对在砂砾石层上钻孔的工艺要进行分析，并采取适当的改进措施。
It should analysis on the craft of drilling in sand-stone layer, better to accept the improve methods in properly.
溆浦砂锡矿床赋存在第四系冲积层中锡石主要富集在底部砂砾石层。
Placer tin deposit in xupu occurs in alluvial sediment of quatemary system and cassiterite chiefly concentrates at the bottom of gravel layers.
溆浦砂锡矿床赋存在第四系冲积层中，锡石主要富集在底部砂砾石层。
Placer tin deposit in Xupu occurs in alluvial sediment of Quatemary SyStem and CaSSiterite chiefly concentrates at the bottom of Gravel layers.
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