Magmatic thermal influence on the metallic element composition of Xiamaling Formation shale: Implications for oil-source correlation and hydrocarbon potential evaluation

The majority of current studies on the influence of magmatic intrusions on shale have focused on how these intrusions affect organic geochemistry and shale reservoir properties. In comparison, less attention has been paid to the changes in elemental compositions generated by the thermal effects of magmatic intrusions into shale, which has limited our understanding of oil tracking and the evaluation of hydrocarbon potential. Here we conduct a case study of magma-associated shale reservoir in the Mesoproterozoic North China Craton using a combination of mineralogy, organic petrology, and geochemistry. The results show that the intrusion-related heating effect resulted in a more acidic and oxidizing diagenetic environment in the shale and that the total organic carbon, vanadium, and rare earth element contents decreased approaching the intrusion. However, the contents of elements (e.g., silicon and barium) associated with organic matter productivity do not exhibit trends pertaining to the distance from intrusion, given their independence from crude oil migration. These findings shed new light on the migration of metal elements during the thermal evolution of shale and can provide a scientific basis for applying metal elements to oil-source correlation and hydrocarbon potential evaluation.