Page images
PDF
EPUB
[merged small][merged small][merged small][merged small][ocr errors][ocr errors][merged small][merged small]

WASHINGTON, H. S.

WAYLAND, E. J. .

WOODHEAD, F. N.

Deccan Traps and other Plateau
Basalts. Bull. Geol. Soc. Amer.,
XXXIII, 765-803.

Note on the Sources of Origin of
Ceylon Gem-Stones. Econ. Geol.,
XVIII, 514-516.

WAYLAND, E. J. and The Miocene of Ceylon. Quart. Jour. Geol.
DAVIES, A. M.
Soc., LXXIX, 577-602.

WITHERS, THOMAS H.. Revision of some Fossil Balanomorph
Barnacles from India and the East
Indian Archipelago. Rec. Geol. Surv.
Ind., LIV, 281-295.

Coal Mining in the Raniganj and
Jharia Coal Fields. Coll. Guard.,
CXXVI, 1101-1102. (Abstract.)

Introduction

A GEOGRAPHICAL CLASSIFICATION OF THE MINERAL DEPOSITS OF BURMA. BY J. COGGIN BROWN, O.B.E., D.SC., M.I.M M., M.I.M.E., F.G.S., Superintendent. Geological Survey of India. (With Plate I).

[merged small][ocr errors]

CONTENTS,

F

[merged small][ocr errors][merged small][subsumed][subsumed][subsumed][merged small]

INTRODUCTION.

THE

THE mineral deposits of Burma may be classified into a number of more or less well defined geographical groups, each of which is built up of rocks belonging to contemporaneous geological periods, marked by the effects of the same diastrophic events and characterised by certain mineral associations often prevalent over areas of considerable extent. These groups may be named as follows: (See Table 1.)

[merged small][ocr errors][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small]

A Classification of the Mineral Deposits of Burma.

Typical Igneous Rocks.

Sub-group.

[blocks in formation]

Stratified Rocks.

[blocks in formation]

Gem-gravels of Mogok.

Gold and Platinum placers of the Irrawaddy, Chindwin, etc.
Eluvial wolfram and cassiterite deposits of Tavoy, Mergui, etc.

Alluvial Cassiterite deposits of Tavoy, Mergui and Amherst.
Manganese ores of Myingyan and Meiktila.

Soap sands of the "Dry Zone," etc.

Serpentine

Intrusive granite.
Quartz diorite

Biotite granite

Granite

[blocks in formation]

Rhyolites and tuffs at base Galena, of Ordovician.

zine blende, chalcopyrite, pyrite, stibnite.

Plio-pleistocene and Recent deposits include:

Lignite Deposits of the Shan States and Tenasserim. Oil Shales of Amherst. Residual Iron Ores of the Shan States.

[blocks in formation]

1. The Arakan-Naga Region, composed of very folded and altered strata, of pre-Tertiary and perhaps mainly Mesozoic age, penetrated in many places by ultra-basic rocks, which are often changed into serpentine, and bearing chromite, native copper, chalcocite, platinum?, osmiridium?, gold?, chrysotile, steatite and magnesite. The Tawmaw serpentine-jadeite sub-group is included here, though it is not known definitely that the serpentines of the larger region continue across to it in an unbroken lime.

2. The Pegu Gulf, composed of Tertiary rocks, ranging in a complete sequence from the Eocene to the Pliocene and containing hydrocarbons, petroleum, coal and amber.

3. The Mogok-Frontier Region built up of gneisses and crystalline limestones. The gneisses are usually of a biotitic character and are frequently invaded by granites and pegmatites. The crystalline limestones contain rubies, sapphires, spinels and other gem stones as well as graphite.

4. The Mingin Group. A comparatively small, and, as far as known at present, unique area characterised by quartz diorites intrusive into tuffs and other volcanic rocks, and carrying gold-telluride quartz veins containing gold, chalcopyrite, pyrite, galena, franklinite and altaite, the telluride of lead.

5. The Chaung Magyi Group, including both the mica schists of Mong-Long, and the slates, phyllites and quartzites of the Chaung Magyi Series proper. Dykes of intrusive tourmaline granite occur in the mica schists and large boss-intrusions of biotite granite in the Chaung Magyi rocks. Both series are traversed by quartz veins, usually barren, but occasionally carrying gold.

6. The Shan-Yunnan Region, composed chiefly of sedimentary rocks ranging in age from Ordovician to Jurassic. Intrusive rocks are rare but in places islands of strata belonging to the Chaung Magyi group reach the surface. The metallogenetic sequence is essentially a sulphidic one, argentiferous galena, zinc blende, chalcopyrite, pyrite and stibnite. A solitary coal field of Jurassic age is known.

7. The Tenasserim Region, made up of granite intrusive into sediments of unknown age. The predominating minerals are wolfram and cassiterite with smaller amounts of molybdenite, bismuthinite, native bismuth, chalcopyrite, pyrite, arsenopyrite, zinc blende and stibnite. Large portions of this region are occupied by limestone, probably of Upper Paleozoic age, but the geological survey of

Burma has not progressed far enough for these to be separated yet, or for their relations with the granite to be explained.

8. Under a separate head must be included the Plio-Pleistocene and Recent deposits scattered throughout Burma, which contain minerals of present or potential value; such as the lignite and peat deposits of the Shan States, the oil shales of Amherst, the residual iron ores of the North Shan States and elsewhere, the surface manganese ores of Meiktila, the laterite of Lower Burma, the hill and lake gem-gravels of the ruby mines, the gold and platinum placer deposits of the Irrawaddy, Chindwin and other rivers, the eluvial wolfram and cassiterite deposits and the alluvial cassiteritebearing sands of Tavoy and Mergui, the soap sands of the "Dry Zone", etc. It is not proposed to describe these separately and in detail here but they will be mentioned as occasion arises.

THE ARAKAN-NAGA REGION.

The mountain chain of which the

Arakan Yoma forms the

Orography.

southern part stretches in a double convex arc for 1,500 miles of which 400 are under the sea. The submarine portion is south of latitude 16° but it appears again in the Andaman and Nicobar Islands attaining therein heights of over 2,000 feet. In Burma it borders the western edge of the Irrawaddy and Chindwin valleys and up to latitude 21° its trend is approximately north-north-west with peaks of over 4,000 and 6,000 feet. Beyond this region, where it enters the hill tracts of Pakokku and Northern Arakan, it begins to lose the individuality it possesses further south in groups of more or less parallel ranges directed north and south. Further north still, in Manipur and the Naga Hills, the ridges bend round to the northeast and converge into the Patkoi Range and its offshoots, which continue till they meet the north and south folds of the frontier system. Mount Victoria in the Pakokku Hill Tracts is over 10,000 feet high, while in Manipur and the Naga Hills there are peaks of over 6,000, 7,000 and 8,000 feet respectively.

The whole country is covered with dense vegetation, its structure is complicated and appears to possess few beds of marked particularity, it is inhabited by tribes of doubtful temperament and the movements of the few geologists who have worked in it have usually been guided by those of the armed forces they accompanied..

« PreviousContinue »