Geological detectives tracing tin to its source
The tin placers of Wetlet Township are a direct result of geological processes spanning millions of years. The story begins in the Cretaceous period, when masses of molten rock, or magma, pushed their way into the Earth's crust. This magmatism relates to the broader tectonic collision between the Indian and Eurasian plates. Specifically, the tin mineralization in this part of Myanmar is linked to the Western Granite Province, a belt of granitic intrusions running through the region. Many of these ore-bearing granites are classified as S-type, meaning they formed from the melting of pre-existing sedimentary rocks.
As these granitic bodies cooled and crystallized deep underground, hot, water-rich fluids circulated through fractures in the rock. These hydrothermal fluids contained high levels of dissolved elements, including tin. As the fluids cooled, they deposited various minerals, including cassiterite (SnO2), the primary ore of tin. Cassiterite formed within quartz veins and as disseminated crystals within the granite itself. Over immense timescales, uplift and erosion exposed these tin-bearing granites to the surface. Weathering broke down the host rock, freeing the dense and resistant cassiterite crystals. Rivers and streams then transported these sediments downstream, creating the placer deposits seen today. Because cassiterite is much heavier than most other sediment particles, it naturally concentrates in specific areas of the stream bed, such as on the inside of meanders or behind rock bars.