Objective A dense lake−oasis system has developed in the southeastern Badain Jaran Desert. Two prevailing hypotheses on groundwater recharge mechanisms have been proposed for this area, namely long−distance recharge through fault−controlled deep circulation and combined recharge from local paleowater and precipitation. Direct geophysical evidence for deep structures is currently lacking. It remains unclear whether the Altyn Tagh Fault extends into the desert hinterland and which geological bodies govern the lake water supply. This study intends to identify concealed structures and water−storage rock bodies by deep electrical structure detection, clarify the controls of magmatic intrusions on the oasis groundwater system, and provide new evidence for investigating groundwater circulation mechanisms in arid regions.

Methods The Audio−Magnetotelluric (AMT) method was used to conduct a systematic survey in the desert hinterland. Six geophysical profiles were deployed, including a 150−km−long southwest−northeast trending traverse across the desert and a 25−km nearly north−south profile passing through the lake−concentrated zone. Two−dimensional resistivity cross−sections were adopted to characterize the deep subsurface electrical structure beneath the lake aggregation area.

Results (1) No electrical signatures of deep major faults were identified on the resistivity sections within the depth range of 0~2 km, and no obvious regional lateral abrupt changes in resistivity were observed. This indicates that the Altyn Tagh Fault Zone does not extend into the hinterland of the Badain Jaran Desert. (2) Multiple local high−resistivity anomalies with resistivity values greater than 2000 Ω·m occur along the profiles. Combined with monzogranite outcrops on the surface and regional geological data, these anomalies are interpreted as Yanshanian magmatic intrusions.

Conclusions Magmatic intrusions sustain the co−evolution of oases and climate via a dual water−controlling mechanism. A ternary coupled recharge mechanism of “magmatic water control−paleoclimate legacy−modern climate buffering” is proposed for the oases in the Badain Jaran Desert. This finding can provide new evidence with joint geophysical and hydrogeological constraints for the study of groundwater circulation in arid regions.