The Volume of Granites in Main Helium Source Rocks of Weihe Basin and the Estimation of Their Helium Production: A Case Study of the Lantian Batholith

As the key of helium resource evaluation, the evaluation of helium source rocks mainly consist of rock type, contents of helium-derived elements uranium and thorium, formation age and volume. Granite is viewed as the main helium source rock and first three parameters are readily accessable. However, the volume of granite is too complicated to be constrained. The Weihe basin show great potential for helium resources, in which enormous granitic batholiths along its southern magin are considered as the main helium reservoir for crustal-derived helium, providing ideal conditions for this parameter. In this study, the Lantian batholith is selected and the shape of it is near to a flat elliptical column with high length-width ratio based on the published geological and geophysical data. Moreover, the thickness of Lantian batholith is calculated to be 4.7 km and the volume is 572 km³ according to a power-law relationship. In addition, the results show that the average contents of helium-produced elements U and Th are 5.8×10⁶ and 19×10⁶ in Lantian batholith. Combined with the radioactive decay law, the calculated helium production for the Lantian batholith is about 0.27 billion cubic meters. In view of voluminous granitic batholiths at the south edge of Weihe basin, total helium production have been evaluated at 18.4 billion cubic meters, which will provide significant implications for the exploration breakthrough of helium in Weihe Basin and further establishment of the helium resource evaluation.