## 3 Ore Deposit Geology  
The lithology that occurred in Lijiapuzi mining district is mainly that of Archean metamorphic rocks and Mesozoic anddesite and tuff (Figure 2). The former was metamorphosed so intensely that mismatization occurred widely in the mining area. The Nb-Ta bearing pegmatities were believed to be related to the regional mignatization in the southeastern part of the mining area [27], partially owing to the isotopic dating of muscovite in the pegmatities ranging from 2395 Ma to 2464 Ma ([PERSON], No. 101 Geological Team Co., Ltd, Liaoning Nonferrous Geology Bureau, Fushun, P. R. China; Unpublished work). The Mesozoic volcanic activities led to the reactivation and superimposition of the brittle fractures upon the ancient basement. The faults in the mining area can be divided into two categories, i.e., the NE trending Lijiapuzi overthrust fault, which dips to the SE with an angle of 40-60\({}^{\circ}\), and the NW trending Dabuqiyan overthrust fault, which dips to the NE with an angle 40-60\({}^{\circ}\). Both the faults are compressive-shearing, conjugated, and belong to the same tectonic stress field. Figure 1: Regional geologic map of Lijiapuzi. Ar-Archean metamorphic rocks; My-Archean mignatitic granite; Z-Sinian shale and limestone; \(\in\)-bitumen bearing shale and limestone; O-dolomitic limestone; C-carbonaceous shale; P-quartz sandstone; K-sandstone interlayer with andesite; Q-quaternary. The detailed exploration of the Lijiapuzi deposit began in 2008 and finished in 2018 [28]. A total of 11 Nb-Ta bearing pegmatities were explored, with an average of 0.0045%Nb\({}_{2}\)O\({}_{5}\) and 0.0312%Ta\({}_{2}\)O\({}_{5}\) (Table 1). Generally the NE-trending pegmatities are longer but thinner, echelon arranged with relatively regular shape such as the vein-type, have large extension depth and weak or no differentiation. The NW-trending pegmatities are shorter but thicker, and usually occur near the surface with small extension depth and relatively irregular shapes such as lenticular and well-differentiated [27]. All the pegmatities are localized in Archean metamorphic rocks. Note that No.1, No.2 and No.9 pegmatities are composed of both the NE-trending and NW-trending sub-fractures, and the pegmatities dics occur as a whole, indicating that the pegmatite-controlling fractures were formed contemporarily and probably conjugated. \begin{table}
\begin{tabular}{c c c c c c c} \hline \multirow{2}{*}{**Ore Body**} & \multicolumn{3}{c}{**Ore Body Size**} & \multicolumn{3}{c}{**Grade (\%)**} & \multicolumn{3}{c}{**Occurrence**} \\ \cline{2-7}  & **Length (m)** & **Average** & **Nb\({}_{2}\)O\({}_{5}\)** & **Ta\({}_{2}\)O\({}_{5}\)** & **Dip Direction** & **Dip Angle** \\ \hline \⃝1 & 238 & 0.83 & 0.0038 & 0.0339 & 305\({}^{\circ}\) & 75\({}^{\circ}\) \\ \hline \⃝2 & 156 & 0.99 & 0.0040 & 0.0319 & 315\({}^{\circ}\) & 75\({}^{\circ}\) \\ \hline \⃝2-1 & 163 & 1.99 & 0.0074 & 0.0330 & 315\({}^{\circ}\) & 65\({}^{\circ}\) \\ \hline \⃝3 & 90 & 0.12 & 0.0028 & 0.0320 & 325\({}^{\circ}\) & 85\({}^{\circ}\) \\ \hline \⃝4 & 648 & 1.21 & 0.0051 & 0.0298 & 145\({}^{\circ}\) & 75\({}^{\circ}\) \\ \hline \⃝5 & 42 & 3.39 & 0.0022 & 0.0510 & 55\({}^{\circ}\) & 40\({}^{\circ}\) \\ \hline \⃝6 & 26 & 1.87 & 0.0035 & 0.0475 & 40\({}^{\circ}\) & 50\({}^{\circ}\) \\ \hline \⃝7 & 112 & 0.37 & 0.0020 & 0.0158 & 40\({}^{\circ}\) & 65\({}^{\circ}\) \\ \hline \⃝8 & 100 & 0.28 & 0.0020 & 0.0592 & 295\({}^{\circ}\) & 40\({}^{\circ}\) \\ \hline \⃝9 & 31 & 0.99 & 0.0036 & 0.0549 & 25\({}^{\circ}\) & 75\({}^{\circ}\) \\ \hline \⃝0 & 35 & 0.27 & 0.0020 & 0.0254 & 70\({}^{\circ}\) & 55\({}^{\circ}\) \\ \hline \⃝0 & 102 & 0.50 & 0.0033 & 0.0351 & 302\({}^{\circ}\) & 65\({}^{\circ}\) \\ \hline \end{tabular}
\end{table} 
Table 1: The general characteristics of Nb-Ta bearing pegmatities in Lijiapuzi deposit (Adapted from ref. [28]). Figure 2: Geological map of Lijiapuzi Nb-Ta deposit. Lithology is the same as Figure 1B. 1-mineralization borehole; 2-non-mineralization borehole; 3-pegmatities ore bodies; 4-sections.