is similar to I-type granites (sourced from magma of partially-melted igneous rocks) and S-type granites (sourced from magma of partially-melted sedimentary rocks), which are originated from orogenic (mountain-building) settings (e.g. convergent plate boundaries). In terms of geological times, these REEs-enriched granites which formed evenly over a wide geological time period (i.e. from Ordovician to Cretaceous), showing that these deposits are not formed in special environments related to any major geological events. Magmatic-hydrothermal processes In general, parental rocks of regolith-hosted rare earth element deposits are felsic igneous rocks (e.g. granite, rhyolite, rhyolitic tuff etc.), which are associated with granitic magmatism and volcanism in subduction system. During magma crystallisation, LREE and HREE are primarily enriched in granitoids through two separate mechanisms. LREE enrichment: LREE-enriched granitoids are formed by magma differentiation, which progressively fractionates magma composition into chemically-distinctive layers during its cooling process. As REEs are incompatible elements (less preferred to incorporate into the structure of solidifying crystals), they remain as melt in magma chamber until the last stage of cooling. Therefore, the last and the uppermost fraction of granitoid is highly REEs-enriched. HREE enrichment: HREE-enriched granitoids are formed by auto-metasomatism. It is a process of chemical alterations of recently crystallised felsic magma by the left-over hydrothermal fluid (e.g. water, CO2 etc.) at the later stage of magma crystallisation. During the chemical alteration, through various chemical reactions with hydrothermal fluids, HREEs are then introduced into secondary minerals along veinlets. Secondary processes Secondary process (i.e. weathering) is essential in further enrichment of HREE-/LREE-rich granitoid. It turns the granitoid to an economically-extractable orebody. Therefore, warm and humid climate, together with slightly acidic soil in subtropical zones favour the formation of regolith-hosted rare earth element deposits. A combination of intense chemical, physical and microbiological weathering allows the removal of REEs in upper, more acidic completely weathered layer, downward migration through rainwater and eventually, deposition (and concentration) at lower, less acidic moderately weathered layer. (REE forms a more stable complex in soil with higher pH). In addition, intense weathering in subtropical areas (i.e. South China) continuously removes significant volume of overlying materials from the in-situ weathering system, which is a process called denudation. In response to the mass removal, exhumation (an isostatic-uplifting process which deep-seated rock is brought to the land surface) occurs and hence, replenishes materials for on-going denudation. Thus, the dynamic equilibrium system between denudation and exhumation further facilitates the development of thicker weathering profile