Overprinting of the Paleoproterozoic Haib Porphyry Cu-Mo deposit by ∼1.0–1.20 Ga hydrothermal events: Evidence from Titanite Petrochronology

Titanite is a key accessory mineral for tracing magmatic origin and hydrothermal evolution, yet systematic studies on its application in ancient, often overprinted Precambrian analogues remain sparse. The Paleoproterozoic Haib porphyry Cu-Mo deposit in southern Africa hosts abundant primary and hydrothermal titanite, making it an ideal natural laboratory for testing the applicability of titanite to resolve the genesis of ancient porphyry systems. Three genetic generations of titanite are recognized based on textural, isotopic, and compositional features. Magmatic titanites (Ttn 1) in diorite and quartz monzonite xenoliths yielded U-Pb intercept ages of 1880–1887 Ma and are enriched in REE, Mo, Hf, and Zr. Hydrothermal titanite (Ttn 2) can be divided into two subgroups: Ttn 2a represents hydrothermally overprinted Ttn 1 with patchy zoning and yielded dates of 1880 Ma to 1841 Ma, whereas Ttn 2b precipitated from hydrothermal fluids and yielded dates of ∼1840 Ma. In comparison, alteration-related titanites (Ttn 3) occur in veins and potassic-altered porphyries, forming rims around coronitic rutile through hydrothermal replacement. Ttn 3 is characterized by pronounced LREE depletion and fractionated HREE patterns and yielded substantially younger ages of ∼1.03–1.20 Ga. These results demonstrate that the Haib porphyry system formed in the Paleoproterozoic and was overprinted by a separate Mesoproterozoic hydrothermal event related to the regional ∼0.95–1.20 Ga Namaqua orogeny. Our findings establish titanite as a robust petrochronometer for deciphering primary formation and the post-magmatic hydrothermal overprinting of ancient porphyry deposits.