Quantitative Depth Profiling of Zircon Crystallization Histories: New Insights Into Himalayan Magmatic‐Tectonic Evolution

Abstract Laser ablation inductively coupled plasma mass spectrometry (LA‐ICP‐MS) has expanded in situ U‐Pb geochronology. However, conventional circular or square ablation pits (>15 μm) lack the resolution to resolve complex or narrow growth zones (<5–15 μm). Depth profiling offers a unique solution by ablating through the surface of mineral grains, producing continuous, spatially resolved isotopic data. Current depth profiling analyses rely on manual, subjective identification of age signal plateaus, hindering efficiency and reproducibility. This study introduces the Automated Depth Profiling Technique (ADEPT), a quantitative workflow that includes data optimization, automated plateau segmentation, and rigorous screening to objectively identify growth zones and calculate U‐Pb ages. Bayesian posterior validation of ADEPT showed >84% of data within one root mean square error. Applying ADEPT to 4,615 Himalayan leucogranite zircon depth profiles reveals that 74% of grains preserve 2–4 distinct age signal plateaus, confirming major age peaks at 45 ± 2, 35 ± 3, 19 ± 4, and 9 ± 2 Ma. Analysis of zircon age continuity (ΔAge, the difference between core/or mantle and rim ages) reveals a systematic eastward decrease across the Himalayan orogen. We interpret this trend as a record of thermal longevity of magma reservoir tied to the regional tectonic regime. Specifically, compressional and cooler settings foster more continuous zircon growth (i.e., smaller ΔAge), whereas extensional and warmer settings produce relatively discontinuous growth (i.e., larger ΔAge). ADEPT provides a robust and efficient tool for resolving complex mineral age histories and offers new insights into the magmatic and tectonic evolution of the Himalaya.