U-Pb ages of detrital zircon and monazite from beach placers in Sri Lanka: Implications for configuration of the Columbia supercontinent

We report new U-Pb ages of zircons and monazites, and trace element chemistry combined with Hf isotopes of the zircons from beach placers on the southwest coast of Sri Lanka, in order to understand the provenance and history of crustal evolution. The zircon ages record major concentrations that range from 650-450 Ma, 1000-650 Ma to 2300-1600 Ma, and a few grains are > 2500 Ma. The primary source signature occurs at ca. 2300-1600 Ma, with significant amounts of ca. 1800 Ma ages. The Rare Earth Element patterns of older zircons support their magmatic origin. The higher percentage of Ediacaran - Late Cambrian ages are interpreted to be metamorphic, which is further supported by the monazite ages that range from 580-481 Ma. These ages provide information on the entire multiple thermal history of Sri Lanka. The monazite trace element chemistry points towards their possible derivation from garnet bearing metasedimentary rocks. The higher percentage of Paleoproterozoic ages indicate the uplifted Highland Complex of Sri Lanka was the primary source provenance. Zircon ages and Hf isotopic compositions indicate that Paleoproterozoic was the major period of crustal growth, and Neoproterozoic was the period of prominent crustal reworking in Sri Lanka. The similarity between the Paleoproterozoic age peaks of zircons with comparable Hf isotopic signatures of beach sands from Sri Lanka and southwest India suggests derivation from a similar provenance. Moreover, the ages of metasediments and magmatic rocks from Sri Lanka are comparable to those from granulite terranes in Madagascar and East Africa. The remarkably similar age distributions and Hf isotopic signatures indicate that East Africa and central Madagascar were juxtaposed from the Paleoproterozoic to the early Mesoproterozoic, when southern India and Sri Lanka were contiguous with Madagascar. Hence, the comparable Paleoproterozoic age peaks of beach sands from four contiguous terranes provide evidence on the distribution and configuration of the Columbia Supercontinent.