Geological assessment of some permo-carboniferous carbonate sediments in The Southern Part of The Pha Houa Xang Range, Mouang Thakhek, Khammouane Province, The Lao PDR

Abstract

Some Permo-Carboniferous carbonate sediments in the southern part of the Pha Houa Xang range, Mouang Thakhek, Khammouane Province, the Lao PDR have been studied. The rocks can be lithologically divided into 3 rock units in ascending order, namely, A, B and C. The rock of unit A comprises dark grey, very thickly-bedded dolomitic limestone. Petrographically, it is composed partly of euhedral to subhedral rhombs of dolomite embedded in microspar calcite martrix. Geochemically, the rock of unit A is characterized by 43.95 wt.% of CaO, 9.44 wt.% of MgO, witht little amount of SiO2 and others. The possible use of this rock unit is for road materials, and concrete aggregates. The rock of unit B comprises mainly dark grey, bedded-limestone intercalated with thinly-bedded, brownish grey to dark grey chert. Petrographic study shows that the rock are composed of laminated micrite and pelmicrite. Geochemically rock unit B is characterized by relatively high silica (SiO2) content ranging from 10.51 to 78.10 wt.% with average value of 30.74 wt.% . The calcium oxide (CaO) content is relatively low. Its average value is 34.80 wt.% Magnesium oxide content (MgO) is not too high with an average value of 2.32 wt.%. The rock of unit B is regarded as an impure limestone. It can also be used for road materials and concrete aggregates. The rock of unit C consists predominantly of light grey to brownish grey, fine-grained, very thickly-bedded limestone. Petrographic study shows that the rock comprise predominantly oosparite, and oomicrite. Geochemically, its CaO content ranges from 51.01wt.% to 55.60 wt.% with an average value of 54.79wt.% MgO content is relatively low. It varies from 0.08 to 3.94 wt.% with an average value 1.11 wt.% . The rock unit C can be classified as high to very high purity limestone according to Cox et al. (1977). Accordingly, it is potentially suited remarkably for Portland cement, agriculture, ceramic (grade II), quick lime, and sugar refining. The possible geological reserve for Portland cement is calculated to be 1,381.93 mill. metric tons, agriculture -1381.93 mill. metric tons, ceramic grade II- 1364.27 mill. metric tons, quick lime 1314.04 mill. metric tons, and sugar refining - 1087.26 mill. metric tons, respectively. According to its excellent location, the limestone from the study area can be regarded as highly potential site for exploitation in the near future.