Zircon U–Pb and Lu–Hf Signatures for the Gold Porphyry Deposits in the Alta Floresta Gold Province (Amazonian Craton, Brazil): Implications for Regional Exploration

The present work focuses on investigating U–Pb and Lu–Hf ages of zircon grains obtained from Au mineralized granitic rocks from Alta Floresta Gold Province (AFGP), in the Amazonia craton, Brazil. Also, detrital zircon grains from recent Au-rich sediments were analyzed for U–Pb ages and Lu–Hf isotopic signatures to apply to regional gold exploration in the AFGP to define targets consisting of deep-seated mineralized bodies using isotopic tracers. U–Pb ages of magmatic rocks, obtained from zircon grains, indicate crystallization ages ranging from 1896 Ma to 1825 Ma for rocks associated with gold deposits, and TDM model ages between 2.65 and 1.96 Ga and εHf values between +8.0 and −4.6. U–Pb ages obtained from 89 detrital zircon grains indicate peaks at 2055–1980 Ma, 1889–1985 Ma, 1790–1700 Ma, and 1600–1550 Ma. The first group is related to the basement, represented by the rocks of the Cuiu-Cuiu Complex (TDM 2.0–1.9 Ga and εHf from +8.7 to −1.32). The second group concerns the mineralized magmatic rocks in the AFPG, and the ages range from 18,896 to 1825 Ma, TDM ages ranging from 2.90 to 2.75 Ga, and the εHf values from +15 to −8. The age ranging from 1790 to 1700 is associated with anorogenic magmatism (TDM 2.0–1.9 Ga and εHf from +5.36 to −8.46). The youngest group comprises ages from 1600 to 1550 Ma, probably correlated to the Serra da Providencia suite with TDM of 1,6 to 1,50 Ga and εHf from +5,0 to −10. In this way, it was possible to identify the age range of detrital zircon grains concerning the ages of mineralized granites and characterize the Hf signatures associated with the mineralization processes. In this sense, the zircon grains associated with the magmatic processes responsible for the concentration of noble metals exhibited U–Pb ages and εHf values interpreted as having been generated in magmas originating from a depleted mantle. As suggested in the literature, the magma characteristics reported here are coherent with a hot, hydrous, Fe-rich, high-K calc-alkaline, and subvolcanic emplacement. Based on the model that correlates gold deposits with porphyritic magmatic processes, significant discoveries with world-class volumes may result from better characterization of the deposit types found in the province.