long, which meets the Burma Railways at Namyao, 547 miles from Rangoon. European exploitation dates from 1902, but the upper parts of the deposits were mined for silver by the Chinese for centuries. before that. The ore channel is at least 8,000 feet long and 400 to 500 feet wide and within this zone there are two ore bodies of major importance. The first, known as the "Chinaman," is a huge, lenticular replacement with a core of practically pure sulphides of lead and zinc. It is known to contain nearly 5 millions of tons of ore averaging 27.6 per cent. lead, 19 per cent. zinc, 0.5 per cent. copper and 25 ounces of silver per ton of lead. The ore body is not yet fully explored and this estimate does not include ore containing under 20 per cent. combined lead and zinc. The second ore body is known as the "Shan" and consists of a mixture of the sulphides of lead and zinc with larger quantities of copper than the 'Chinaman" carries. A recent estimate of the proved and probable ore in the Shan body places the total at 570,000 tons, averaging 17 per cent. lead, 11 per cent. zinc, 6 per cent. copper and 19.3 ounces of silver per ton of lead. 66 These ore bodies have been formed by the metasomatic replace ment of rhyolitic tuffs by sulphides carried in hot solutions which ascended from below through an intensely sheared and crushed zone. The tuffs form part of the Bawdwin Volcanic Series which is itself conformably overlain by the Pangyun Beds which may be of Ordovician or Cambrian Age. Five miles away from Bawdwin there is a great massif of intrusive biotite granite and it is thought possible that the mineralising solutions emanated from this. Unfortunately its age is not known. The age of the great Bawdwin overthrust fault which is mainly responsible for the shattering of the rocks in the vicinity of the ore body is the same as that of the Lilu overthrust with which it is connected further south. This does not appear to dislocate beds younger than the Silurian as far as is known at present, but which may be much younger.1 About twenty-five miles to the north-east of Bawdwin are situated the old Chinese lead mines of of Mohochaung which unfortunately no full description has yet been published. M. H. Loveman, however, in a passing reference states that the ore bodies occur in sandstones and shales and are entirely similar Lead-zinc Ore Bodies of Mohochaung. 1 J. Coggin Brown (12), pp. 121-178. to those of Bawdwin as regards the character of the ore itself. The beds in which they are found are probably roughly contemporaneous in age with the Bawdwin sediments and although no rhyolite is present a coarse muscovite-biotite granite is found about 3 miles further to the west. Loveman concludes that "it is a reasonable presumption to consider the granite mass as extending below the ore bodies at both Mohochaung and Bawdwin probably at a great depth below the surface, and it may be to the influence of the granite that the mineralising solutions should be ascribed.” This is, however, simply a hypothesis with no actual facts to support it.1 Small occurrences of galena and other lead and copper ores are known to occur in other parts of the Northern Shan States but none of them are of any economic importance. Amongst others the following may be mentioned the argentiferous galena which used to be mined from the Plateau Limestone near Lashio in the early days of lead slag smelting at Nam Tu2; the galena with cerussite from Namsaw, Hsipaw State; the galena scattered through grey limestone from Mong Tung. Chalcopyrite is known to occur in Mong Lung and stibnite in Hsumhsai.3 Other occurrences of lead and copper ores. Argentiferous galena used to be mined from limestones of Ordovician age near Taunggaung about 20 miles to the north-east of Mandalay. Near Maymyo, chalcocite occurs in the Plateau Limestone with smaller quantities of bornite and a little chalcopyrite, in tiny, reticulated veins disseminated through the mass of the limestone itself. It is often associated with barytes but the usual gangue is calcite. The copper-bearing beds are parallel to and in the vicinity of several galena veins which have been worked to a considerable extent by the Shans. Most of the galena occurs in irregular bunches though some of it is disseminated, and the tenor of both. the lead sulphide and of the chalcocite in silver is high. For the details of this occurrence, I am indebted to Dr. J. Morrow Campbell. Bawzaing, or Mawson, is a small State of the Myelat division. of the Southern Shan States which has been known to produce small quantities of lead and silver for many years. The workings were of Argentiferous Lead and Copper Ores of Bawzaing. 1 M. H. Loveman: (43), pp. 2120-2143. 2 T. H. D. LaTouche: (39), p. 378. 3 L. L. Fermor: (24), p. 234. described by E. J. Jones in 1887 who states that they were situated at Bawzaing, Bwelou and Dwinzu, a few miles to the north and north-east of Kyauktat.1 They were visited again by C. S. Middlemiss in 1899.2 The ore is found beneath the surface covering of red clay overlying limestone, probably of Lower Palæozoic age; in yellow clay filling clefts and fissures in the limestone, and occurs in blocks and fragments varying from the size of a pea to masses three feet across. A more extended examination of this area than was possible by either Jones or Middlemiss has been made recently by Dr. Morrow Campbell, who has found that the old Chinese pits cover a very wide expanse and that there are several bands of country which have been pitted over. They indicate that the deposits consist of very numerous veins parallel to one another and also crossing one another. The country rocks consist of limestones and shales while the stiff clays with which they are covered are believed to be of residual origin while the lumps of galena are the undissolved remains of the veins. Pyrites near Bawzain and Kyauktat. In the bed of the Thaingyi Chaung between Bawdwin and Pwehla, Jones records the occurrence of dark grey shales containing considerable quantities of nodular iron pyrites which was collected and Similar occurrences exist in the Thinge Chaung Middlemiss states too that pyrites is dug for the manufacture of sulphur at Yebok in the Pwehla State, and also at places in the Bawzaing State. distilled for sulphur. and near Kyauktat. Copper ores Bawzain, etc. of Jones records the occurrence of malachite at Kyauktat while Middlemiss mentions the presence of antimonial tetrahedrite with azurite and malachite, at a number of isolated places round about Yataung Hill, some 10 miles to the west-north-west of Bawzaing. At one place, Ganamgya, these ores occur in thin veins in limestone. A vein of argentiferous galena, said to be from 3 to 30 feet thick, occurring in limestone among the foot-hills of Mount Pima, was opened up by a company in 1908. After the extraction of about 2,500 tons of ore in 1909, the mine was closed. It is regrettable that Galena at Mount Pima. 1 E. J. Jones: (35), pp. 191-194. there are no further mineralogical data of this occurrence which although so close to the Burmese plains must be regarded as properly within the Shan-Yunnan ore province. Stibnite deposits of the Southern Shan States. The stibnite deposits of the Southern Shan States were examined by H. C. Jones in 1917 who concluded that none of them appear to be large, or of much economic value. They include the following localities Naking and Loi Hke in Mong Hsu, Mong Ing in Keng Tung, Hkomhpok and Loihsang in Mong Kung. The stibnite usually exists in a bladed, striated variety, and rarely in drusy and massive forms. The oxidised ores valentinite and cervantite are common. The Naking deposit, which in 1908 yielded about 1,000 tons of stibnite, is irregularly distributed through a vein in sandstones, perhaps of Jurassic age. Some of the others appear to be quartz-stibnite veins in Plateau Limestone. North-Eastern Putao. Galena and Cupriferous pyrites of the Shweli-Nmai Hka divide in Myitkyina. Although lying well within the area which I have termed the Mogok-Frontier Province, the highly silicious Galena deposits of limestones of the western side of the Nam Tamai valley may be an outlying patch of metamorphosed Paleozoic rocks belonging properly to the ShanYunnan Province. In them occur a number of sparse, disseminated galena-pyrites veinlets and impregnations which according to Stuart are not worth consideration from an economic point of view.2 In much the same manner bands of sedimentary rocks consisting of limestones and shales appear to be isolated amongst the granites and true metamorphic rocks of the Frontier Ranges between Hpimaw and the Lagwi Pass. According to Stuart they seem to be identical in appearance with rocks of Ordovician and of Devonian age found by the writer in Western Yunnan. At the Chinese galena mines of this vicinity a fine-grained, silicified and chloritised tuff is in contact with white crystalline limestones which are believed to be altered Palæozoics, while the contact zone on both sides is veined and sparsely impregnated with galena, carrying small amounts of silver. Veins of slightly cupriferous pyrites are also found, frequently 10 feet and more across, which bear subsidiary veinlets of galena. Near the contact zone there is a peculiar calcite-mica-magnetite-pegmatite carrying occasional 1 H. C. Jones: (36), pp. 44-50. 2 M. Stuart: (63), pp. 241-254. galena, pyrite and chalcopyrite. The deposits do not appear to be large and their altitude of over 11,000 feet above the sea in a most inaccessible locality, cursed with a climate which renders them only workable during the rains, detracts from their present commercial value.1 The abandoned galena mines of Ponsee in the Bhamo district which were described by Anderson in 1870 and the lead and copper mines of the Mingkuan district north of Têngyüeh in Yunnan, visited by the writer in 1907, the copper deposits of the Taungbalaung reserve in the south of Myitkyina and west of the 1st defile of the Irrawaddy, which produced small tonnages of ore in 1910 and 1911, perhaps form other examples of isolated portions of the ShanYunnan Province lying amongst older rocks.2 THE TENASSERIM REGION, The Tenasserim region commences in the extreme south of Burma, in the Mergui district, and extends north through Tavoy, Amherst and Thaton, Papun and Karenni to the Southern Shan States where it ends somewhat indefinitely. It includes also parts of the eastern hilly portions of the Yamethin and Toungoo districts. It is characterised throughout by the presence of a biotite boss granite which forms the cores of the ranges of the Indo-Malayan system and with which the wolfram and cassiterite veins of Burma. are intimately associated. It is but a part of the great mountain system which stretches into Western Siam and the Malay Peninsula. As delimited here it has a length of some 700 miles and a maximum breadth of about 60 miles as the crow flies, between the sea and the Siamese frontier in Tenasserim proper. The mountain ranges of the Southern Shan States coalesce into Karenni where elevations of over 5,000 feet are attained while further south they maintain a well marked individuality. The upper portion of the area is drained by the Salween and the lower by the Tavoy and Tenasserim rivers. These and the smaller streams usually follow approximately north and south courses. In the Amherst and Tavoy districts the higher peaks reach heights of over 4,000 and sometimes of almost 5,000 feet above the sea. In the south of Tavoy the massif of Myinmolet 1 M. Stuart: (64), p. 408. 2 J. Anderson: (1), p. 267; J. Coggin Brown: (12), pp. 128-131. |