Quantitative, spatially resolved measurements of near-surface material composition on plasma-facing components (PFCs) are critical for interpreting plasma–wall interaction (PWI) driven impurity sources, assessing wall-conditioning performance, and providing model constraints for impurity migration and co-deposition in present-day magnetic confinement devices and future reactors. In this work, picosecond laser-induced breakdown spectroscopy (ps-LIBS) is applied to post-mortem graphite divertor tiles from the stellarator Wendelstein 7-X (W7-X) under device-relevant high vacuum (∼10−7 mbar) to obtain poloidally resolved two-dimensional maps and depth profiles of carbon (C), boron (B), hydrogen (H), and oxygen (O). The ps-LIBS results are cross-validated against isotope-sensitive diagnostics (nuclear reaction analysis, NRA; laser ablation molecular isotopic spectroscopy, LAMIS) and complemented by profilometry, focused ion beam scanning electron microscopy (FIB-SEM)/energy-dispersive x-ray spectroscopy (EDS) and x-ray photoelectron spectroscopy (XPS) to relate lateral patterns to film thickness and near-surface chemistry. Pronounced poloidal heterogeneity is observed: the thickness of mixed co-deposited layers range from ∼0.3 to 0.4 μm in erosion-dominated regions, to ∼0.9 μm in B-rich deposition zones, and exceeds 12 μm in 13C-rich deposits near the outer strike line after 2.5 h of H plasma operation. Depth profiling reveals that late-phase 13CH4 injection forms a C–H–O enriched top layer that locally restructures the pre-existing boronized layer resulting from boronizations, including a pronounced subsurface B maximum at ∼4-5 μm. A calibration-based approach was established to estimate B/C ratios and B inventories from ps-LIBS, enabling quantitative evaluation across the B-rich region, the 13C-rich deposition zone, and the erosion zone. The resulting poloidal and depth-resolved observables constitute benchmark-grade constraints for validating impurity transport/co-deposition modeling and support LIBS pathways toward in-vessel, near-real-time monitoring of surface elemental evolution under varying operational conditions.