Timing and tectonic setting of tin mineralization in southern Myanmar: constraints from cassiterite and wolframite U–Pb ages

Abstract

The southern Myanmar tin ore district is an important part of the well-known Southeast Asia tin belt (SATB), and hosts numerous economically important primary tin-tungsten ore deposits. However, the timing of formation of these deposits is unclear due to the scarcity of robust age data. The tectonic setting of tin mineralization in this area also needs to be further constrained. Most of the primary tin-tungsten ore deposits in southern Myanmar are typical hydrothermal quartz vein–type, with cassiterite and wolframite as the main ore minerals. Here, we present in situ U–Pb ages of cassiterite and wolframite from nine granite-related hydrothermal Sn–W deposits in southern Myanmar. Cassiterite samples from the Hermyingyi, Thitkhatoe, Thaling Taung, Kalonta, Taungphila, Pagaye, Bawapin, Kanbauk, and Letha Taung deposits yield common lead-corrected weighted mean ²⁰⁶Pb/ ²³⁸U ages of 61.6 ± 0.8 Ma, 61.9 ± 0.6 Ma, 60.4 ± 0.9 Ma, 63.0 ± 0.6 Ma, 62.9 ± 0.6 Ma, 69.5 ± 0.5 Ma, 63.6 ± 0.6 Ma, 61.3 ± 0.6 Ma, and 84.9 ± 0.5 Ma, respectively. Wolframite samples collected from these deposits also yield consistent ages with the cassiterite samples. These ages, combined with available tin mineralization ages from other deposits in the western part of the SATB, define three epochs of Sn metallogeny related to three contrasting geodynamic settings: (1) Early Cretaceous (~ 125–110 Ma) mineralization is related to post-collision slab break-off after collision between the West Burma terrane and the Sibumasu-Tengchong terrane; (2) Late Cretaceous to Paleocene (~ 90–60 Ma) mineralization developed in an Andean-type accretionary setting during subduction of the Neo-Tethys oceanic lithosphere; (3) Early Eocene (~ 50–40 Ma) mineralization may have formed in a post-collision setting after the India-Asia collision.

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