Original paper

Lithium-rich albite–topaz–lepidolite granite from Central Vietnam: a mineralogical and geochemical characterization

Hien-Dinh, Thi Thu; Dao, Duy Anh; Tran, Tam; Wahl, Michael; Stein, Eckardt; Gieré, Reto

Abstract

A potential lithium deposit has been discovered in the La Vi mining district, located in Quang Ngai Province, Central Vietnam. The Li-rich rocks (average contents: 1.3 ± 0.9 wt.% Li2O) are highly fractionated peraluminous granites, which are characterized by high contents of Al2 O3, Na2 O, and K2 O, as well as F (up to 2.19 wt.%) and P2 O5 (up to 0.65 wt.%), but very low concentrations of CaO, MgO, MnO, and Fe2 O3. Among the trace elements, Rb, Cs, Sb, Nb, and Ta occur in relatively high concentrations. The granites exhibit a light pink colour and contain mainly albite, quartz, muscovite, lithian muscovite, and lepidolite, with minor amounts of amblygonite – montebrasite, herderite, fluorapatite, topaz, and cassiterite, as well as accessory beryl and goyazite. Electron microprobe analyses of amblygonite revealed high Na2 O concentrations, but these are due to the presence of micrometre-sized lacroixite inclusions. Under the optical microscope, the granite samples are characterized by a range of grain sizes and microfabrics, which indicate that the original granites were hydrothermally altered. We conclude that this late-stage alteration was associated with albitization, greisenization and Li enrichment, so that the unique features of the rare albite–topaz–lepidolite granites are probably of secondary rather than primary origin.

Keywords

li-rich micasquang ngaiherderitelithiumlepidolitela vialbite–topaz–lepidolite granitevietnamgoyaziteamblygonite