Growth and physical transport of molybdenite spherules in a Na-Al-F-rich melt, Cave Peak porphyry Mo deposit, Texas, USA

The Eocene Cave Peak intrusive complex in Trans-Pecos Texas, USA, hosts a porphyry Mo system enriched in Mo, F, Nb, W, Sn, and rare earth elements. Some Cave Peak molybdenite occurs as unusual 100- to 500-µm spherules within aluminofluoride veins. Textural features and buoyancy considerations indicate that molybdenite spherules were formed at depth and were transported by an immiscible alkali fluoride melt. We suggest that these previously unrecognized spherules provide evidence for physical transport of mineral grains as a mechanism to enrich the metal content of F-rich porphyry systems emplaced into shallow crustal settings.