@phdthesis{oai:air.repo.nii.ac.jp:00003307,
 author = {PATCHAWEE, NUALKHAO},
 month = {Sep},
 note = {Permo-Triassic granitoids from various areas along the Loei Fold Belt, northeastern Thailand, were studied. The aim of this work is to document the petrochemical characteristics of granitoids in the Loei Fold Belt. The Loei Fold Belt is an 800 km long, north-south trending fold belt that hosts several epithermal Au-Ag and skarn Au-Cu-Fe deposits. The study areas are divided into five regions i.e., (1) Mung Loei, (2) Phu Thap Fah - Phu Thep, (3) Phetchabun, (4) Nakon Sawan - Lobburi and (5) Rayong - Chantaburi region. The granitoids consist of monzogranite, granodiorite, monzodiorite, tonalite, quartz-syenite and quartz-rich granitoids. These granitoids are composed of quartz, plagioclase, K-feldspar at varying proportions with mafic minerals such as hornblende and biotite. Accessory minerals, such as titanite, zircon, magnetite, ilmenite, apatite, garnet, rutile, and allanite are also present. Magnetic susceptibilities of granitoids vary from 6.5×10-³ to 15.2×10-³ in SI unit in Muang Loei, from 0.1×10-³ to 29.4×10-³ in SI unit in Phu Thap Fah – Phu Thep, from 2.7×10-³ to 34.6×10-³ in SI unit in Petchabun, from 2.4×10-³ to 14.1×10-³ in SI unit in Nakon Sawan – Lobburi and 0.03×10-³ to 2.8× 10-³ in SI unit in Rayong – Chantaburi. Concentration of major elements suggests that these intermediate to felsic plutonic rocks have calc-alkaline affinities. Concentration of rare earth elements (REE) of the granitoids normalized to chondrite displays moderately elevated LREE and relatively flat HREE patterns, with distinct depletion of Eu. Rb vs. Y/Nb and Nb/Y tectonic discrimination diagrams illustrate that the granitoids from Muang Loei, Phu Thap Fah – Phu Thep, Phetchabun, Nakon Sawan – Lobburi and Rayong - Chantaburi formed in continental volcanic-arc setting. New age data from radiometric K-Ar dating on K-feldspar from granodiorite in Loei and Nakhon Sawan areas yielded 171±3 and 221±5 Ma, respectively. K-Ar dating on hornblende separated from diorite in Lobburi yielded 219±8 Ma. These age dating data suggest magmatism of Muang Loei occurred in the Middle Jurassic, and Nakon Sawan – Lobburi occurred in Late Triassic. Both Nb vs. Y and Rb vs. (Y + Nb) discrimination diagrams and age data indicate that Nakon Sawan – Lobburi granitoids intruded in Late Triassic at Nong Bua, Nakon Sawan province and Khao Wong Phra Jun, Lobburi province in volcanic arc setting. Muang Loei granitoids at the Loei province formed later in Middle Jurassic also in volcanic arc setting. Most of δ³⁴SCDT of pyrite separated from granitoids along Loei Fold Belt, range from -2.1 to +2.2‰. The negative δ³⁴SCDT values of ore minerals from skarn deposit suggest that the I-type magma has been influenced by light biogenic sulfur from local country rocks. The Au-Cu-Fe-Sb deposits correlates with the magnetite-series granitoids in Phetchabun, Nakon Sawan-Lobburi and Rayong - Chantaburi areas. Metallogeny of Au and Cu-Au skarn deposits, and epithermal Au deposit are related to adakitic rocks of magnetite-series granitoids from Phetchabun and Nakon-Sawan areas. All mineralization along the Loei Fold Belt are generated in the volcanic arc related to the subduction of Paleo-Tethys.  T Al content of biotite of granitoids increase in the following order: granitoids associated with Fe and Au deposit < those with Cu deposit < barren granitioids. XMg of biotite in granitoids in Muang Loei, indicate the crystallization of biotite in magnetite-series granitoids under high oxygen fugacity condition. On the other hand, low XMg (<0.4) of biotite in magnetite-series granitoids in Phu Thap Fah – Phu Thep and Rayong – Chantaburi, indicate reduced environment, low oxygen fugacity, associated with Au skarn deposit (Phu Thap Fah) and Sb-Au deposit (Bo Thong), respectively. The magnetite-series granitoids at Phu Thap Fah having low magnetic susceptibilities and low XMg of biotite, were formed by reduction of initially oxidizing magnetite-series granitic magma by interaction with reducing sedimentary country rocks as suggested by negative δ³⁴SCDT values.},
 school = {秋田大学},
 title = {Mineralization, Magmatism and Tectonics along the Loei Fold Belt, Northeastern Thailand},
 year = {2018}
}