MAGNETIC SUSCEPTIBILITY, GEOLOGY, PETROGRAPHY, AND GEOCHEMISTRY OF THE GRANITE HOST ROCK OF BASETH MO-CU MINERALIZED STOCK, CAMBODIA: IMPLICATION FOR ITS ORIGIN

Baseth quarry is mainly composed of Mo-Cu mineralized Jurassic microgranite (MG) stock which was intruded by small dacitic dykes with fault and quartz vein system. Both of the intrusive rocks is locally porphyritic, and has very low magnetic susceptibility. Petrograpically, the MG consists of quartz, potassium feldspar, plagioclase, biotite, and muscovite as major phase, and apatite, zircon, monazite, xenotime, and opaques as accessory minerals. The baseth granite is characterized by high SiO₂, Al₂O₃, K₂O, negative Nb, Sr, Ba, Ti, and Eu anomalies, and unfractionated heavy rare earth elements (HREE). In general, this granite showed S-type characteristics and syn-collsion tectonic setting affinity, and was emplaced at shallow depth, where heterogeneous crustal source rock exists, with several magma pulses. In addition, data supports ternary granitoids type, i.e. partial melting of upper mantle, partial melting of mafic rocks in forming continental crust, and partial melting of the subducting Sibumasu continental slab due to collision between Sibumasu and Indochina block.