冰冻区季节性洪流与砂金成矿

Seasonal flood and placer gold metallogeny in permafrost region

大、小兴安岭北部冰冻区，纬度偏高，气候严寒，冻结期长。流水短暂的季节性河流，比降大流速快，具春融雪水凌汛和雨季两次洪峰，河流水位、流量变差大，携带能力强，因而河流冲—洪积含金碎屑物泥砾混杂，分选、磨圆差。冰冻区季节性洪流，冲刷和堆积交互发生，且具间歇性、周期性，有助于砂金的搬运、淘洗、筛选，提高砂金品位，富集成矿。经勘查、实验证明：在单向冻结“盐析浓金”作用下，冰冻区砂金矿的富矿段，富集在季节洪流的冲—洪积层下部。

The northern part of Da Xiao Xing'an Mountains is a permafrost region with cold weather and longtime gelivation.Many rivers there have deep slope and rapidly current,and have two flood peaks when in ice run and raining season.They vary greatly in water level and rate of flow and have a large carrying capacity.As the seasonal rivers erode and sediments alternately and periodicly,they are very helpful for carrying,panning and selecting gold to form deposits. It has proved by investigations and experiments that the rich block of placer gold in the permafrost region is at the lower of sediments as a result of one way freezing of salt seperating out and gold enriching.