## 3 Ore Deposit Geology
The common differentiation in pegmatites manifests as the microcline wall zone, the albite intermediate zone, and the quartz core whose boundaries are obscure (Figures 3A and 4B). In most cases, the aplite border zone, usually ubiquitous in other rare metal pegmatites [10], is absent in the Liijapuzi ore district. Figure 3: Field occurrence of pegmatites in the Lijiapuzi Nb-Ta ore deposit. (**A**) An abandoned mining gallery; (**B**) Marginal microcline rock sample, with late quartz veinlets filled in the fractures; (**C,D**) Transitional abtic rock sample, with gradual or irregular boundary; (**E**) Sample close to quartz core, with greenish muscovite; (**F**) purple lepidolite; (**G**) quartz core; (**H**) Chloritized plagioclase amphibolite; Mcl-microcline; Q-quartz; Ab-albite; Ms-muscovite; Lpd-lepidolite. In the wall zone, the pegmatic is mainly composed of microcline, quartz and a small amount of garnet, with either a minor amount or no muscovite at all (Figure 3B). In some cases there are quartz-veinlets dispersed in the wall zone, resulting in weak montmorillonite of the microcline (Figure 4A). In addition, there are few sulfide minerals (Figure 5A,B) ore Nb-Ta minerals. The intermediate zone differs from the wall zone by replacement of the microcline by albite (Figure 3C,D) with irregular boundaries (Figure 4B) and the appearance of massive greenish muscovite (Figure 3E), and occasionally purple lepidolite (Figure 3F), spodumene (Figure 4C), apatite (Figure 4E), and minor beryl, gahnite, cassiterite and zircon [27]. The Nb-Ta minerals such as tantalite and columbite, including microlite [27], were formed along the margin of albite (Figure 5E,F), indicating that the rare metal mineralization was intimately related to the albitization. Locally the mineral grains of early stages such as quartz, microcline, albite and muscovite were fractured and filled by epigenetic hydrothermal minerals. Laser Raman spectroscopy indicates that the opaque minerals involved are needle-like goethite along the cleavage or fractured margin of muscovite (Figures 4D and 5C), accompanied by the accumulation of uranium minerals such as  
Figure 4: The main minerals in the Lijiapuzi pegmatite deposit (Transmitted cross-polarized light). (**A**) microcline with crossed twinning, with weak alteration; (**B**) albitization of microcline with an irregular contact boundary between them; (**C**) spodumene; (**D**) muscovite, fractured perpendicular to cleavages and filled by late metallic minerals; (**E**) apatite; (**F**) chloritization of plagioclase amphibites; Mcl-microcline; Ab-albite; Q-quartz; Spd-spodumene; Ms-muscovite; Apt-apatite; Chl-chlorite; Tour-tournaline. calciouranoite (Figure 5D), which means there should have been an epigenetic hydrothermal mineralization after the formation of the Nb-Ta mineralization [28]. The paragenesis of goethite and uranium minerals is well in accordance with the mineralization pattern of a unconformity-type uranium deposit [29], and so is the Lijiapuzi, which is considered to be of supergene stage [27]. Where the pegmaties become thicker, or locally dilative, for instance, the thicker NW-trending pegmaties with the high differentiation of pegmatie will result in a pure quartz core, with minor or no other minerals (Figure 3G). The miarolitic cavities are seldom seen throughout the mining area. The wall rock alteration is weak in the Lijiapuzi ore district. Where the pegmaties are thick, especially the flanks around the local dilation parts of the pegmaties, the relatively strong alteration manifests as the chloritization of biotite and hornblende (Figure 3H), and occasionally there occurs some volatile components such as tourmaline in the host rocks (Figure 4F). Figure 5: The major metallic minerals in the Lijiapuzi ore deposit.