PETROGRAPHIC, MINERAL, GEOCHEMICAL CHARACTERISTICS OF BA NA GRANITOID

Abstract

Ba Na granitoid is isometric shape, with exposure of 30 sqa km area. Petrographic composition is mainly coarse – medium grained biotite granite, included in the first phase. The fine grained leuco rock of the second phase is small massif in shape, distributed along fault in NE – SW direction. SiO₂ content of Bana granitoid is variation from 73.74% to 76.24%. Total of K₂O +Na₂O is from 7.32% to 8.33%. Ratio of K₂O / Na₂O: 1.66 – 2.07. This is S – Granite. Value of ¹⁴⁷Sm/ ¹⁴⁴Nd = 0,1249 is nearly stable crust material. Ratio of Sm/Nd is low.  e_Nd has negative value and very small  proved that Ba Na granitoid must derive from crust source or mantle source which rich (EM). The age of source regional forming calculated from isotopic of Sm, Nd is 1.06 Ba (according to model of chondrite mantle source region) or 1.74 Ba (according to model of poor mantle source). The prospects of related mineralization  of Ba Na granitoid is Sn (W, Nb, Ta) with amsemblage of topaz – cassiterite – tourmaline – quartz (sometime is Ta – Nb) . The result of isotopic analysis of U-Pb in zircon of Ba Na biotite granite sample at lab of Tasmania University, Australia, age of Ba Na is 242.9 ± 1.5 Ma and 240.6 ± 2.2 Ma.