热失重分析中烧失率的地质意义初探——以海拉尔盆地贝38井南屯组一段泥岩为例

Geology Significance of Cauterized Loss in Analysis of Thermal Loss-in-weight: A case of Lower Cretaceous Nantun 1 Member Shale Samples from Well Bei-38 in Hailaer Basin

海拉尔盆地贝38井南屯组一段20块泥岩样品中出现5块烧失率异常,其烧失率达8.812%～18.770%,为其它样品的2～4倍。对异常样品作进一步烧失试验:0～400℃区间,烧失强度都较低,说明粘土矿物的吸附水、层间水及有机质的可溶烃含量都较少;400～500℃区间有2块样品的烧失强度明显异常,表明其有机质含量明显偏高;500～950℃区间,另2块样品的烧失强度特别高,这是由于其中的伊利石结构水脱失所致。该地层的微量元素Cu/Zn、Sr/Ba、V/Ni和常量元素Mn/Ti、MnO2随深度的变化与烧失率曲线有极好的相关性。烧失率异常可指示氧化—还原环境或水体深浅变化以及判别水体的盐度。

There are 1/4 abnormal samples of cauterized loss in the Lower Cretaceous Nantun 1 Member shale from Well Bei-38 in Hailaer Basin. The cauterized loss of the 5 samples are 2～4 times as high as the average samples.The result of experiment shows: (1)low cauterized loss between 0～400℃ implies that there are a small amount of absorbed water and interlayer water in clay minerals and a small amount of soluble organic matter;(2)obviously abnormal cauterized loss for two samples between 400～500℃ indicates that organic matter is high evidently;(3)extraordinarily abnormal cauterized loss for the other two samples between 500～950℃ are abnormal because the structured water in mineral illite are dehydrated. The variation of Mn/Ti and MnO2 ratios of the constant elements, and Cu/Zn, Sr/Ba and V/Ni ratios of the trace elements with increasing depth is correlative well with their curves of cauterized loss.It is suggested that the cauterized loss can indicate the oxidation-reduction environment or the varied depth and the salinity of water.