大庆徐家围子火山岩热释光特征与火山活动期次及岩性判别

热释光的用途很广,但在判断火山活动旋回(期次)以及火山岩类型鉴定方面,尚未涉及。本文通过对大庆徐家围子升深7和杨参1井岩石样品以及其他井部分火山岩样品的热释光特征的研究,发现:①升深7井中,顶部峰型和总积分强度近似,可指示为同期喷发产物;中下部热释光特征表现为“顶底韵律效应”,可能是较晚阶段的火山喷发物对前一阶段顶部有热改造而消耗了部分辐射积累。②杨参1井中根据热释光特征可划分2个旋回和4个期次。下部旋回发育双峰,主峰积分强度差别较大,可能指示底部为多源喷出产物(如多机构产物)混堆,小旋回产物之间叠加;主峰积分强度从下到上依次减小,反映了火山岩喷发强度的降低。上部旋回发育单峰,热释光积分强度相差不大,可能为一套同源产物。③升深7井中未发生明显蚀变作用的安山岩热释光特征相似而杨参1井中岩相均一、未蚀变的凝灰质岩热释光特征也很相似,这表明热释光特征技术应用于火山空落相岩石和火山熔岩岩性判别是有可能的。最后总结了火山岩热释光研究应注意的问题。

Thermoluminescence characteristics of volcanic rocks from Daqing and their significance in determination of volcanic cycles and lithology

The thermoluminescence (TL) technique has been widely used in various academic fields, but has not yet been involved in the determination of the volcanic cycle (stage) and the judgment of the type of volcanic rocks. Based on studying the TL features of all the volcanic rock samples from the boreholes Shengshen 7 and Yangcan 1, Xujiaweizi,Daqing City, as well as some samples from other boreholes, the authors have reached the following conclusions: (1) In the borehole Shengshen 7, the TL peak-types and total TL integral intensities of the rocks are similar to each other at the top, probably suggesting that the volcanic rocks are eruptive materials of the corresponding period; the TL parameters of the rocks vary rhythmically in the middle and at the bottom, and this may be the result of thermal alteration of the rocks at the top of each eruption by later eruptive materials which consumed part of the cumulated radiation. (2) In the borehole Yangcan 1, the volcanic cycles (stages) can be divided into two subcycles and four stages based on the TL feature variations. At the bottom of the cycle, the rocks show double TL peaks, and the intensities of the main TL peaks show remarkable differences, proba-bly indicating that the bottom rocks are multisource ejected prod-ucts from different volcanic structures, and the products of the small cycles are superimposed upon each other; the intensity of the dominant TL peak decreases upward,reflecting the declining of the eruptive activity of the volcanics. The rocks at the top cycle show a single peak, and the TL intensities only show insignificant differences, implying that the rocks belong to a suite of cognate products. (3) In the borehole Shengshen 7, the TL features of the andesites without obvious alteration are similar to each other; and in the borehole Yangcan 1, the TL features of the tuffaceous rocks with homogeneous lithofacies and without alteration are very similar too. These phenomena show that the utilization of the TL technique to distinguish rocks of pyroclastic fallout facies and determine lithology of lava is feasible.