Chapter 1 - Introduction

Abstract

Geologically, Myanmar can be divided into the post-Jurassic Popa-Loimye magmatic arc in the west and northwest, the continental Shan Plateau, and a late Triassic suture zone and former Permian to Triassic island arc in the Far East. The main purpose of this book is to describe these features, their constituent belts and segments, and the abundant mineral deposits and occurrences within them and to discuss or propose plate boundary–related tectonic or magmatic events to which they may be related. Additional terranes proposed since 1978 include the Western Burma block; Sibumasu (Sino-Burma-Malaysia-Sumatra), which includes all or most of the Shan Plateau but has a very loosely defined western boundary; and the Mt. Victoria Land block, originally envisaged as the exposed part of a Western Burma block basement. Myanmar is also divided into a western and eastern half by the northerly trending Sagaing Fault, on which the western half has moved northward relative to the east since the early Miocene. According to some estimates, this displacement exceeds 300 km, but there is no general agreement. In the south the fault forms the boundary of the Popa-Loimye arc, the northward continuation of the Sunda arc, but in the north what may be the offset arc continues east of the Sagaing Fault through the Tagaung-Myitkyina Belt into northeastern India and Tibet. Because of this uncertainty in displacement, this Introduction (Part 1) is followed by Parts 2 and 3, dealing with geology and mineralization, respectively, east and west of the fault. Most of Part 4 is concerned with structural belts or types of mineral deposit that occur both east and west of the fault. Myanmar's mineral deposits cover a wide variety of types, almost regardless of how they are categorized. Jade exports have recently exceeded in value that of all other minerals combined, eclipsing that of ruby, once the principal gemstone is produced. Very recently Myanmar became the world's largest exporter of tin, from new mines in Wa State; although when these tin reserves decline, their value may soon be overtaken by that of copper from Letpadaung, part of Southeast Asia's largest producing copper deposit near Monywa. The Mawchi mine northeast of Yangon was at one time the world's largest producer of tungsten, and Bawdwin in the northern Shan State the largest base metals mine, producing ore from a Cambrian deposit with similarities to the Miocene Kuroko ores in Japan. Myanmar has also produced up to several percent of world manganese and contains several different types of gold deposit, but the official production figure for gold is an underestimate. The well-received 1994 Mining Law has been modified and superseded, but details and rules are not yet final. There is a widespread desire that individual deposit and national production figures, long provided for oil and gas, be publicly available for every mineral.