## 3 Results and Discussion
The inferred ore veins and rock distribution along Line L2 are shown in Figure 9. Similar to Line L1, the depth of the igneous rock top interface gradually decreases from smaller to larger station numbers, intruding into the country rocks with the top interface at approximately 200 m elevation. Based on resistivity and IP anomaly characteristics, areas exhibiting metallic mineralization IP signatures and low-resistivity anomaly zones within or adjacent to high-resistivity regions are interpreted as ore veins. Three ore veins are identified in this profile: Vein A (skarm-type) is relatively deep (between stations 200 and 400), showing low-resistivity and moderate-chargeability anomalies with its top interface near 0 m elevation; Vein B (greisen-type) develops at the contact between igneous and sedimentary rocks (between stations 600 and 800), exhibiting low-resistivity and high-chargeability anomalies with its top interface near 50 m elevation; Vein C (greisen-type) occurs at the granite-sedimentary rock contact (between stations 970 and 1150), displaying relatively low-resistivity anomalies with its top interface near 100 m elevation. The intrusion of composite granites and subsequent post-magmatic hydrothermal activities in the study area provided sufficient heat sources for rock and mineral formation. Combined with the relatively abundant W and Sn in the region, these processes supplied ample material sources for mineralization. The contact zones between intrusive granites and country rocks created favorable metallogenic conditions. The delineated greisen-type veins are distributed near the top interface and contact zones of intrusive granites, while the identified skarm-type veins occur in limestone strata contacting granites. Greisen-type W-Sn deposits are high-temperature pneumatolytic-hydrothermal deposits typically associated with the upper or marginal zones of highly fractionated granites, whereas skarm-type deposits are contact metasomatic deposits predominantly hosted in marble, limestone, and skarm formations. Figure 10 presents the drilling results along the exploration line in the Longshang mining area (Figure 1c), where both skarm-type and quartz vein-type W-Sn veins are developed. The greisen-type W-Sn veins occur in the upper and marginal zones of the granite pluton, while the skarm-type W-Sn veins are hosted within Devonian limestone strata in contact with the granite. The drilling results not only confirm the accuracy of the delineated ore veins but also demonstrate the effectiveness of the large-electrode-spacing multi-channel spread-spectrum induced polarization method in polymetallic mineral exploration. Figure 8: The results of the two-dimensional inversion of the L2 linear width frequency. Figure 10: Drilling Results in the Longshang mining district (modified from [14]). 1: Devonian limestone; 2: medium-fine-grained porphyritic biotite granite; 3: skarn-type W-Sn orebody; 4: greisen-type W-Sn orebody. Figure 9: Interpretative geological profile of L2. 1: Weathered layer/quaternary sediments; 2: sandstone/sandy mudstone; 3: Devonian limestone; 4: medium-fine-grained porphyritic biotite granite; 5: skarn-type W-Sn orebody and its identification letter; 6: greisen-type W-Sn orebody and its identification letter; 7: greisen-type W-Sn orebody and its identification letter. As an advanced mineral exploration technique, SSIP demonstrates significant advantages over conventional IP, audio-magnetotellurics (AMT), and controlled-source audio-magnetotellurics (CSAMT). Utilizing broadband continuous-signal spectrum analysis, SSIP enables the simultaneous acquisition of multi-frequency data in a single measurement. It offers efficient data collection and full-spectrum dispersion characterization capabilities, making it particularly suitable for mineral exploration in geologically complex regions.