Objective The Riqingwei Basin is located in the Rizhao–Qingdao–Weihai area, within the Sulu orogenic belt. During the Early Cretaceous Qingshan period, strong tectonic fluid activity occurred. Previous studies have shown that crustal thinning triggers a tectonic magmatic evolution sequence based on the crustal magma system in a basin, but there has been no research on the characteristics of high–temperature and high–pressure fluid breaking through surrounding rocks and corresponding crack filling under the driving force of basic magma.

Methods Based on this, an investigation was conducted in the four areas of Dingzi Bay, Lingshan Island, Wulian, and Taolin in the basin, and five samples were obtained and analyzed for petrography, XRF, whole rock main and trace elements, rare earth elements, and gas–liquid inclusions.

Results It was found that Mg and Fe elements were co enriched in the carbonate veins of Dingzi Bay, and P elements were significantly depleted. Lamprophyry and basalt belong to the same olivine crude basalt series and are rich in volatile components such as H₂O and CO₂. The distribution patterns of rare earth and trace elements in the Carbonate veins, lamprophyry and basalt are roughly the same.

Conclusions Research has confirmed that the accumulation of light components (750℃≤T≤1300℃, P>>1000 MPa) at the top of the basalt magma reservoir in the study area has broken through the weak points of the surrounding rock, forming hidden explosive breccia. Subsequently, crystal differentiation produces lamprophore magma, which is locally immiscible and forms low viscosity gas hydrothermal fluid filled large pore sandstone, liquefying and enveloping it into cracks; The immiscibility effect caused by shallow cooling and pressure reduction generates a large amount of high–pressure gas hydrothermal fluid (T>354℃, P>>76.13 MPa), which breaks through the surrounding rock and forms hydraulic breccia veins. Finally, during the cooling and pressure reduction process, the cracks are filled with differentiated crystals in the order of quartz–ferromagnesian carbonate–calcite.