六盘山盆地热历史的裂变径迹证据

Apatite fission track evidence for the thermal history of the Liupanshan basin

研究盆地的热历史将为确定生烃过程和探勘目标提供重要制约因素 .磷灰石裂变径迹研究表明 ,六盘山盆地白垩系地层经历两次埋深加热事件 .第一次在白垩纪末之前达到最高古地温 ,第二次在晚新生代约 8MaB .P .之前达到最高古地温 .第一次最高古地温要高于第二次最高古地温 .晚新生代六盘山盆地古地温梯度约为 16℃ km .从白垩纪到新生代 ,六盘山盆地可能发生古地温梯度降低事件 .三叠纪、中侏罗统烃源岩达到或超过生油高峰温度 .白垩纪乃家河组和马东山组虽然进入生油窗温度范围 ,但未达到生油峰温度 .按照古地温资料推断 ,三叠纪、中侏罗统烃源岩应为六盘山盆地主要生烃源岩 ,晚白垩纪之前应为六盘山盆地烃源岩的主要生烃阶段 .

Studying the thermal history of a basin will provide important constraints on determination of hydrocarbon generation and exploring target. Apatite fission track data suggest that the early Cretaceous strata in the Liupanshan basin were subjected to two burial heating events. The first heating event occurred during Cretaceous, and reached the maximum temperature prior to the end of Cretaceous. The second one occurred during Eocene-late Miocene, and reached the maximum temperature at about 8MaB.P. The first maximum temperature by burial heating is higher than the second one. The maximum temperature to which the Triassic-Jurassic hydrocarbon source rocks were subjected is higher than the oil generation peak phase. The Naijia River formation and the Madong Mountain formation were buried to the \!oil generation window' phase, but the maximum temperature is lower than the oil generation peak phase. According to the paleotemperature results, the Triassic-Jurassic strata may be the predominant hydrocarbon source rocks in the Liupanshan basin. The predominant hydrocarbon generation occurred prior to the end of Cretaceous.