The Chatree deposit is located in the Loei-Phetchabun-Nakhon Nayok volcanic belt that extends from Laos in the north through central and eastern Thailand into Cambodia. Gold-bearing quartz veins at the Q prospect of the Chatree deposit are hosted within polymictic andesitic breccia and volcanic sedimentary breccia. The orebodies of the Chatree deposit consist of veins, veinlets and stockwork. Gold-bearing quartz veins are composed mainly of quartz, calcite and illite with small amounts of adularia, chlorite and sulfide minerals. The gold-bearing quartz veins were divided into five stages based on the cross-cutting relationship and mineral assemblage. Intense gold mineralization occurred in Stages I and IV. The mineral assemblage of Stages I and IV is characterized by quartz-calcite-illite-laumontite-adularia-chlorite-sulfide minerals and electrum.

Cu-Mo mineralization occurs in southern part of the Chatree Au-Ag deposit, central Thailand. Quartz veins of Cu-Mo mineralization are divided into five types: Types A, B, C, D and E. Quartz veins of Types A, B and C are hosted in altered granodiorite porphyry, and quartz veins of Types D and E occur in altered andesite lava. Mineral assemblages of Types A, B and C quartz veins are composed of qz-chl-ilt-mol-pyccp, qz-chl-ilt-ccp-py and qz-chl-ilt-ccp-py-sp-po, respectively. Types D and E quartz veins consist of qzchl-py-ccp-sp-po and qz-ep, respectively. Fluid inclusions of quartz veins are divided into liquid-rich twophases fluid inclusion, vapor-rich two-phases fluid inclusion and multiphase solid-bearing fluid inclusion. Coexistence of a halite-bearing fluid inclusion having salinity of 37 equiv. wt.% NaCl and a vapor-rich twophases fluid inclusion having salinity of 1 equiv. wt.% NaCl suggests that the Cu-Mo-bearing quartz veins were formed at temperature of 450 C and pressure of 250 bars (depth of approximately 1.5 km from the paleosurface). Based on the formation temperature of 450 C of quartz veins and the δ 18O values of quartz of the quartz veins, the δ 18 O value of fluid responsible for the Cu-Mo-bearing quartz vein is estimated to be +9.9‰. The origin of fluid forming the Cu-Mo-bearing quartz veins in the N prospect of the Chatree mining area would be magmatic water. Based on the characteristics of geology, age, mineral assemblage and the formation environment, Cu-Mo mineralization would be different from the epithermal Au-Ag mineralization of the Chatree mining area.

Huai Yuak area is located at Ban Kaeng Subdistrict, Sisatchanalai District, Sukhothai Province, Northern Thailand. The occurrences of gold are distributed along the Sukhothai Fold Belt from Phrae to Lampang though Sukhothai provinces. The Huai Yuak area is a one of the primary gold deposits in the Sukhothai Fold Belt. The geology of the Huai Yuak area is comprised of siltstone, sandstone, shale and tuff from the Permian to Triassic age. Quartz veins of the deposit were formed in siltstone, sandstone and shale. Based on the cross-cutting relationship and mineral assemblages, the quartz veins can be divided into three stages. Quartz veins of stage I are composed of a large amount of microcrystalline quartz with a minor amount of arsenopyrite and a trace amount of calcite, illite, pyrite, chalcopyrite, galena and electrum. Quartz veins of stage II consist of mainly quartz. Quartz veins of stage III are comprised of a large amount of dolomite and a small amount of quartz with a trace amount of illite and arsenopyrite. Electrum is associated with arsenopyrite, galena, pyrite, chalcopyrite and sphalerite. The electrum was formed as inclusion and filled in fractures of arsenopyrite and pyrite. Based on structure, texture and occurrence, pyrite and arsenopyrite can be classified into four types. Type 1 pyrite and arsenopyrite were disseminated in sandstone, siltstone and shale. Type 1 is characterized by euhedral to subhedral shape with size ranging from 0.1 to 3.0 mm. Type 2 pyrite and arsenopyrite were formed in a fracture as veins in shale and metashale. Type 3 pyrite and arsenopyrite occur in quartz veins. Type 3 is associated with galena, chalcopyrite, sphalerite and electrum. The electrum in Type 3 at Huai Yuak deposit was formed as inclusions and native gold associated with pyrite, arsenopyrite, chalcopyrite, galena, sphalerite and quartz of stage III. The concentration of electrum is related to arsenic content in pyrite. Type 4 of pyrite and arsenopyrite was formed in shale rock. Pyrite and arsenopyrite gains at the Huai Yuak gold deposit have had developed under a different structure and physical condition from uplift during volcanic arc setting.

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The Huai Kham On gold deposit is located in the central part of the Sukhothai Fold Belt, northern Thailand. The Sukhothai Fold Belt represents an accretionary complex formed by subduction and collision between the Indochina and Sibumasu Terranes. There are many small gold deposits in the Sukhothai Fold Belt; however, the styles and formation environments of those gold deposits are not clear. The geology of the Huai Kham On deposit consists of volcanic and volcanosedimentary rocks, limestone, and low‐grade metamorphic rocks of Carboniferous to Triassic age. Gold‐bearing quartz veins are hosted by volcanic and volcanosedimentary rocks. The quartz veins can be divided into four stages. The mineral assemblage of the gold‐bearing quartz veins of Stages I and II comprises quartz, calcite, illite, pyrite, native gold, galena, chalcopyrite, and sphalerite. Quartz veins of Stage III consist of microcrystalline quartz, dolomite, calcite, pyrite, native gold, and chalcopyrite. Veins of Stage IV consist of calcite, dolomite, chlorite, and quartz. Fluid inclusions in quartz veins are classified into liquid‐rich two‐phase (Types IA and IB), carbonic‐aqueous (Type II), and carbonic (Type III) fluid inclusions. The homogenization temperatures of Types IA and II fluid inclusions that are related to the gold‐bearing quartz veins from Stages I to III ranged from 240° to 280°C. The δ18O values of quartz veins of Stages I to III range from +12.9 to +13.4‰, suggesting the presence of a homogeneous hydrothermal solution without temperature variation such as a decrease of temperature during the formation of gold‐bearing quartz veins from Stages I to III in the Huai Kham On gold deposit. Based on the calculated formation temperature of 280°C, the δ18O values of the hydrothermal solution that formed the gold‐bearing quartz veins range from +3.2 to +3.7‰, which falls into the range of metamorphic waters. The gold‐bearing quartz veins of the Huai Kham On deposit are interpreted to be the products of metamorphic water.