Abstract

We report the first laser ablation-inductively coupled plasma-mass spectroscopy (LA-ICP-MS) study of trace element substitution in enargite. Results indicate significant variability in the composition of enargite samples from a single ore system. Samples come from the Mankayan district, Philippines, which hosts the Lepanto high-sulfidation Cu-Au deposit, now mined out, and the adjacent Far Southeast porphyry Cu-Au deposit; the genetic relationship between these deposits has been documented in previous studies. LA-ICP-MS analyses indicate significant incorporation of Sb and Fe in enargite (locally exceeding 1 wt %). Other elements such as Bi, Sn, Se, Te, Ag, and Zn occur at concentrations exceeding 0.1 wt percent. The distribution of selected trace elements in enargite correlates with previously published variations in fluid inclusion homogenization and melting temperatures and gas compositions. The spatial distribution of data indicates enargite is enriched in Au and Te close to the Far Southeast porphyry. Enargite is enriched in Silver, Fe, and Pb in the center of Lepanto, and Zn (± Cd) is enrich the ore distal to the Far Southeast porphyry. Locally elevated Sb contents occur in samples from subsidiary branch vein structures and may indicate that mineralizing fluids along these structures were modified compared to those that formed the main orebody.

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