塔里木盆地火成岩热释气特征研究

采用加热释气法对塔里木盆地塔北和塔中地区二叠系火成岩中所含流体特征进行了研究,以揭示与岩浆活动相伴生的深部来源流体的特征。塔中地区2个火成岩样品释气总量分别为1 902.7μL/g和1 517.7μL/g,塔北地区5个样品释气总量在515.2～691.5μL/g之间;塔中地区火成岩中流体含量显著高于塔北地区。无论塔中和塔北地区,气体释放量都在中温阶段(700℃)达到高峰。CO₂为火成岩所释放气体中最主要的组成部分,在每个样品的每个温度阶段都有较高的含量,最高可达91.47%;N2和SO₂也是所释放气体中的主要组成部分,在部分样品中含量较高;所释放气体中都或多或少含有一定量的CO,H₂及烃类气体、稀有气体等组分。火山岩所释放气体的40Ar/36Ar值较高,在450.3～1 170.3之间,反映了深源的特点。但气体中3He/4He值除一个辉绿岩样品较高(0.35Ra)外,其他的都较低,位于0.0091～0.091Ra之间,具有壳源的特征;其原因是火成岩所包裹的He与地壳He发生了相互扩散而混合。 

Features of gas released from heated igneous rock,Tarim Basin

The fluid entrapped in Permian igneous rocks collected from the north and the center of the Tarim Basin has been studied using heating method so as to analyze the features of fluid from deep strata.The total amounts of gas released from the 2 igneous rock samples collected in the central Tarim region are 1 902.7 μL/g and 1 517.7 μL/g,much higher than those of the 5 igneous rock samples collected in the northern Tarim region(515.2-691.5 μL/g).In both the central and the northern Tarim regions,gas release amounts reach a peak during the medium temperature stage(700 ℃).CO2 is the dominant compound in released gas from each sample during each temperature stage,and reaches as high as 91.47%.N2 and SO2 are also important compounds in released gas,and have high contents in some samples.CO,H2,hydrocarbon and noble gas are found in released gas more or less.The 40Ar/36Ar ratios of released gas are high,usually between 450.3 and 1 170.3,indicating deep source.However,the 3He/4He ratios of released gas are low(0.009 1-0.091 Ra) except for one diabase sample(0.35 Ra),indicating crust source.The reason is that He in igneous rocks mixes with that in crust due to diffusion effect.