RESERVE AND QUALITY ASSESSMENT OF THE BHAINSEDOBHAN MARBLE, LESSER HIMALAYA, CENTRAL NEPAL

About 400 m thick band of Precambrian Bhainsedobhan Marble of central Nepal is a potential source of raw material for the cement industry. This formation belongs to the allochthonous Bhimphedi Group of the Kathmandu Complex of the Lesser Himalayas. The Mahabharat Thrust (Main Central Thrust?) separates this group from underlying rocks of the Nawakot Complex, which is in turn separated from the Siwaliks by the Main Boundary Thrust to the south. The Bhainsedobhan Marble consists mainly of medium to coarsely crystalline white-blue marble. Some layers of siliceous and dolomitic marble are also present. Variations in grain size and color define three varieties of the marble: medium-grained yellow to pink, medium-grained white, and coarse-grained light-blue to blue.

Detailed exploration and reserve estimation of the Bhainsedobhan Marble has been done in Bhainse based on borehole sampling. Reserve estimation based on channel sampling has been done in Okhare and Khortar. Results of “total” and “rapid” analyses of chemical constituents of samples from these three locations show average values of CaO higher than 44%, and MgO less than 3%. Samples from white and blue bands are of higher grade. The reserve estimation done with a vertical section method shows the total deposits of Bhainse, Okhare and Khortar as 10.8 million tons, 8.6 million tons and 13.7 million tons, respectively.

The Bhainsedobhan Marble is eye-catching for mining due to its proximity to the local market, the ready availability of infrastructure, and available land for construction of cement plants. The entire exposure of the Bhainsedobhan Marble is located near an east-west highway and at an elevation of less than 1500 m. Mining access can be traced into the marble band from the highway following river ways, which are flowing from north to south. The ultimate pit slope can range from 65° to 75°. The Bhainse and Okhare deposits are already in production. Hetauda Cement Industry with a total capacity of 800 tpd is using both deposits. Other prospects need detailed exploration. The estimated demand for cement in the Nepalese market is about 2.7 million tons per year by 2010, however the estimated production is only 0.5 million ton. This large difference between demand and supply requires optimum use of limestone resources available in Nepal.