英国牛津大学Cheng, Anran和Ballentine, Chris J.带领其课题组，报道了原生N₂–He气田形成于克拉通内沉积盆地的新成果。相关论文发表在2023年3月1日出版的《自然》杂志上。

研究小组证明了仅仅来自结晶体基底的地壳氮(与地壳氦成正比-第四代-以稳定的比例脱气)就可以在一些沉积盆地的底部达到足够的浓度，形成游离气相。使用与沉积盆地演化相结合的气体扩散模型，研究组以经典的克拉通内沉积盆地(北美威利斯顿盆地)为例，早在大约1.4亿年前，对这个盆地的研究，证明了地壳氮达到饱和并形成气相。氦分裂成气相。这一成气机制解释了在该盆地和其他盆地的基底沉积岩性中观测到的原始氮气-氦气，预测了伴生地壳气相氢的存在，并且由于相溶解度缓冲，将氦气进入上覆地层的流量减少了约30%。这种气相形成机制的识别为定量评估世界范围内类似陆内沉积盆地的氦和氢储量潜力提供了依据。

据了解，氦、氮和氢在大陆地壳深处不断产生。静止大陆地壳的概念性脱气模型主要假设这些气体溶解在水中，在较浅层沉积系统中，气体通过充满水的孔隙空间中的扩散进行垂直迁移(如参考文献7, 8所示)。气相出溶是氦浓缩和形成社会资源的关键。

附：英文原文

Title: Primary N2–He gas field formation in intracratonic sedimentary basins

Author: Cheng, Anran, Sherwood Lollar, Barbara, Gluyas, Jon G., Ballentine, Chris J.

Issue&Volume: 2023-03-01

Abstract: Helium, nitrogen and hydrogen are continually generated within the deep continental crust. Conceptual degassing models for quiescent continental crust are dominated by an assumption that these gases are dissolved in water, and that vertical transport in shallower sedimentary systems is by diffusion within water-filled pore space (for example, refs. 7,8). Gas-phase exsolution is crucial for concentrating helium and forming a societal resource. Here we show that crustal nitrogen from the crystalline basement alone—degassing at a steady state in proportion to crustal helium-4 generation—can reach sufficient concentrations at the base of some sedimentary basins to form a free gas phase. Using a gas diffusion model coupled with sedimentary basin evolution, we demonstrate, using a classic intracratonic sedimentary basin (Williston Basin, North America), that crustal nitrogen reaches saturation and forms a gas phase; in this basin, as early as about 140million years ago. Helium partitions into this gas phase. This gas formation mechanism accounts for the observed primary nitrogen–helium gas discovered in the basal sedimentary lithology of this and other basins, predicts co-occurrence of crustal gas-phase hydrogen, and reduces the flux of helium into overlying strata by about 30per cent because of phase solubility buffering. Identification of this gas phase formation mechanism provides a quantitative insight to assess the helium and hydrogen resource potential in similar intracontinental sedimentary basins found worldwide.

DOI: 10.1038/s41586-022-05659-0

Source: https://www.nature.com/articles/s41586-022-05659-0