MINERAL RESOURCES
Since the knowledge of geology of the state is still too incomplete, mineral-prospecting remains awaited. Poor communication facilities, inaccessibility and inclement climate have been the constraints in mineral explorations. However, the first attempt of systematic geological survey in Ukhrul District in the recent years have located quite a number of minerals whose mining potential needs be assessed after a detailed study. As it is clear from the Mineral Map, more occurrences of the minerals of whatever indication it is, are met with in the eastern longitudinal half of the state where the rocks are comparatively of older Disang formations. A part of the 220 km long ophiolite belt running north-south is also extended into the eastern border areas. These metamorphose rocks have more possibilities to undergo greater mineralisation. Investigations have revealed the occurrence of the following minerals.
A substantial deposit of good quality limestone suitable for use in the manufacture of cement has been located during the recent years by the Geological Survey of India near Ukhrul. Limestone has also been located at a number of other areas e.g. Hundung, Mova, Khonggoi, Lambui and Paoyi. In the Ukhrul area, limestone occurs in two bands. A reserve of 579 M tonnes has been proved by drilling to a depth of 105 meters. Other deposits are 0.26 M tonnes at Khonggoi and 1.88 M tonnes at Hundung. All these deposits taken together are expected to be able to feed a cement plant of modest capacity of 200 tonnes per day for about 45 years. But the present installed capacity is only 50 TPD (tonne per day).
Evaporities are the mineralised salt sediments from the evaporation of saline waters specially the seawaters. These are used in fertilizer, chemical, drug and building industries. Minor occurrences of magnesium and other salts in Kongai area of Chingai sub-division of Ukhrul District have been located.
A number of brine wells occur at Chingai, Challao, Nameri, Luchai-Khullen, Mariem and Kharawam in Ukhrul District and at Ningel and Chandrakhong village in Thoubal District. The spring water is locally used in making salt cakes.
Chromite deposits containing partly metallurgical grade ore have been located at Kwatha and Khudengthabi in Chandel District and near Siroi Peak in Ukhrul District. Open cast mining has been operated by M/s Orissa Industries Pvt. Ltd., Rourkela. Possibilities of locating bigger deposits are indicated. Production of Chromite in 1993-94, 1994-95, 1995-96, 1996-97 are 643 MT, 784, 470 MT and 62 MT respectively.
Nickeliferous magnetites, copper and cobalt have been located at Kwatha, Khudengthabi and Namphesha along the ultramaphic expositions near Moreh. The ore grade and size of deposit need further assessment with investigations extended into the northern strips of the ultramaphic belt. The possibility of locating platinum in this ophiolite belt has been observed (NEC).
Minor occurences of these minerals have been reported from the ultramaphic suites of rocks particularly in the Ukhrul and Moreh areas.
Jadeite, a semi-precious mineral occurs in the Indo-Burma borders. While Burma and China have abundant resource of these minerals, Indian occurences are very poor. Other compact coloured minerals include the surpentinites found in the same belt.
The alluvial soils and some of the residual soils in the valley contain clay. The character of the clay is clay is such that it can not be used in the manufacture of white-ware. Bricks, sanitary and channel pipes can be manufactured from it. The clay deposit at Kangvai (Churachandpur District) has been recommended for use in terracotta industries. This deposit has a reserve of 2.52 M tonnes. The clay deposits at Thongjao, Sekmai and some other villages are used in pottery. The rest are fit for brick industry.
Lignites have been located at Kangvai (Churachandpur District) and some other places but they have found to be uneconomical. The Central Ground Water Board encountered gas emanations during exploratory drillings in search of ground water potentials at eight different places in Imphal and Bishenpur Districts. Of these, the samples from Wangkhei (Borehold No.4) and Lamphel (Borehole No.14) were put to test at the laboratories of the GSI and the ONGC, (IFCD, 1984). The GIS laboratory test revealed the gas to be inflammable and almost odourless with very faint carbide like smell. The chemical composition of the gas emanation was
CO2 = 3.6%
CnH2n = 1.4%
CH4 = 72.0%
C2H6 = 10.0%
N2 and inert = 10.9%
Samples of oil and gas emanated at Lamphelpat well were analysed with the following results:
Methane = 37.53 %
Ethane = 14.69 %
Propane = 33.93 %
Iso-Butane = 04.10 %
Butane = 6.70 %
Oil is a mineral which is normally not exposed on the surface. Although, the oil sample tested indicates resemblance to crude oil, the final answer to the existence of oil bearing structure is yielded only by actual drilling. Drilling is not done in an unknown area without securing the sub-surface picture by "other means" as it is very expensive operation. These "other means" are mainly geophysical prospecting methods which according to Prof. D.K. Ganguli of Manipur University, has remained pending with the programme of GSI and the ONGC in this state.
Oil, which consists of gaseous, liquid and sometimes solid hydrocarbons in mutual solution is mainly of marine origin. Once formed in the source rock, it migrates along the state untill it meets a suitable structure or trap where it is stored underground with the salt water at the bottom, the liquid oil above it, and the gas at the topmost part. the Indo-Stanvac Oil Prospecting Project in Bengal Basin found the strata without oil reserves but with evidence of oil bearing once with a dip towards the SE-direction. In the theory of migration, Prof. Ganguli's belief is that the same oil from the Bengal Basin must have migrated eastward leaving pockets in Bangladesh, Tripura, Mizoram, Nagaland and Andaman where such occurrences have already been detected.
Manipur has the same stratigraphic sequence of the same age in oil laden Assam and other places mentioned above including Myanmar. The gas encounters in Manipur Valley were during groundwater surveys and not during an oil-prospecting mission. Proper intensive geophysical surveys therefore, may revealed a better picture of the oil structures of the state.
