The Yinachang deposit is interpreted as a Paleoproterozoic IOCG deposit containing iron-oxide Cu-Au mineralisation in the Kangdian region of SW China (Zhao and Zhou 2011; Zhao et al., 2013). The deposit includes measured resources of ~17 Mt Fe at grades of 42-45%, ~700,000 t Cu at a grade ~1% and ~12 t of Au at ~0.5 g/t, and unmeasured occurrences of U, Nb, Co, Ag, Mo, and REEs. Apatite is an ubiquitous accessory phosphate mineral in a wide range of rock types and is often used as a vector for mineral exploration (Mao et al., 2016). In this contribution, hydrothermal fluorapatite in banded Fe-Cu ore is studied at Yinachang. This is the first time zoned fluorapatite has been observed in Cathodoluminescence (CL) images of grains ~500 µm wide where the core is bright and the edge is dark. EPMA analyses of 7 spots show that the core has an average content of 0.11% Cl, 0.28% La2O3, 0.65% Ce2O3, 0.33% Nd2O3, and 0.42% SiO2. In contrast, the rims of 6 spots average 0.07% Cl, 0.11% La2O3, 0.13% Ce2O3, 0.09% Nd2O3, and 0.09% SiO2. The EPMA scans of fluorapatite in Figure 1 show that the concentration of La, Ce, Nd, Cl, Si is significantly higher in the core, but the concentration of Ca, P, O, F is not significantly different for both zones. SEM analysis also shows that the concentration of La, Ce, Nd, Cl is higher in the core. TEM analysis shows that the bright part of the zoned fluorapatite is due to enrichment in Nd, Ce, Y and Si, although the atomic structure of the fluorapatite does not change. The above analyses show that there of the two stages of REE enrichment and the early one is richer.

Reference(s)

Zhao, X.F. and Zhou, M.F., 2011. Fe–Cu deposits in the Kangdian region, SW China: a Proterozoic IOCG (iron-oxide–copper–gold) metallogenic province. Mineralium Deposita, v. 46, p. 731–747.

Zhao, X.F., Zhou, M.F., Li, J.W., Selby, D., Li, X.H., and Qi, L., 2013. Sulfide Re–Os and Rb–Sr isotopic dating of the Kangdian IOCG metallogenic province, SW China: implications for regional metallogenesis. Economic Geology, v.108, p. 1489-1498. 

Mao, M., Rukhlov, A.S., Rowins, S.M., Spence, J. and Coogan, L.A., 2016. Apatite Trace Element Compositions: A Robust New Tool for Mineral Exploration. Economic Geology, v.111, p. 1187-1222.