Structural Geology and Mineralization in A and K-East Pits at Chatree Gold Mine, Phichit and Phetchabun Provinces, Thailand

Abstract

The Chatree Gold Mine is located at the boundary between the Phichit and Phetchabun provinces in northeast-central Thailand. The gold mineralization occurs in epithermal veins and breccias hosted in Lower Triassic (250±6 Ma) volcanic and volcaniclastic-epiclastic sedimentary rocks. Structural evolution with respect to mineralization in the area covering the A and K-East Pits of the Chatree Gold mine has been interpreted based on geophysical data, pit-mapping data and kinematic-dynamic analyses of fault slip data. The results indicated that the volcanic and sedimentary host rocks were erupted and deposited under E-W extension generating N-S trending normal faults, probably in a back-arc position along a continental margin subduction zone that continued from the Permian. Mineralized veins intruded along normal faults and associated fracture systems probably during or shortly after the extension episode at 250.9±0.8 Ma. The mineralization zones were then crosscut and redistributed by Middle Triassic andesitic dykes (244±7 Ma) and strike-slip faults, both of which trend NW-SE and NE-SW. The strike-slip faults of both orientations have both right-lateral and left-lateral movements. During the Late Triassic, the area was affected by E-W compression that was probably related to collision between the Indochina Plate and the Shan-Thai Plate (Sibumasu Plate) or its constituent terranes. The compression produced N-S trending reverse faults and shear zones. Certain reverse faults have been observed a result of inversion of the pre-existing normal faults. The dykes and strike-slip faults are inferred to have formed simultaneously under transient stress systems during the gradual transition between the Early Triassic E-W extensions to the Late Triassic E-W compression.