Mineralogical and Geochemical Characteristics and Genetic Significance of the Zircon–Titanium Placer Deposit in the Wenchang Area, Hainan

Tracing the provenance and understanding the ore-forming processes of coastal zircon–titanium placers are important issues in placer research. The Wenchang area in Hainan Province is one of the important coastal zircon–titanium placer enrichment regions in China; however, the provenance, transport, and depositional mineralization mechanisms of these deposits remain poorly understood. In this study, systematic heavy mineral petrography, whole-rock major and trace element geochemical analyses, and zircon U–Pb dating were conducted on the zircon–titanium placer deposits in the coastal area of Wenchang to investigate their ore-forming processes. The results show that the zircon–titanium placers along the southeastern coast of Wenchang exhibit a gradual north–south transition in provenance, transport, and depositional mineralization mechanisms, and can accordingly be divided into Zone I (north) and Zone II (south). LA-ICP-MS zircon U–Pb dating reveals that zircons from the north (Zone I) are dominated by a major age population at 435.6 ± 2.2 Ma, with a subordinate age population at 155.1 ± 2.7 Ma. For the south (Zone II), previous data indicate that zircons yield ages predominantly in the ranges of 130–160 Ma and 230–260 Ma, with a minor group at 420–450 Ma, pointing to a provenance difference between the two zones. The northern zone (Zone I) is inferred to be characterized by proximal provenance and marine influence. The main sediment source is Paleozoic–Mesozoic granites in the Wenchang area and on both sides of the Qiongzhou Strait, with a possible minor contribution of distal detritus from the Pearl River drainage basin, introduced under the influence of currents in the Qiongzhou Strait. Heavy minerals were likely transported to the coast by rivers and wave erosion and subsequently enriched through repeated winnowing and sorting by high-energy waves and tides. The southern zone (Zone II) is characterized by multi-source convergence and mixed sedimentary mineralization. The sediments are interpreted to mainly derive from high-K granites in the Qiongzhong area, which were transported over long distances by the Wanquan River and other drainage systems and possibly mixed with Quaternary sediments and fine-grained detritus from the Pearl River basin carried by longshore currents. In the coastal environment, these materials were reworked by waves and tides and mixed with bioclastic debris, leading to ore enrichment. These results provide some basic data for a better understanding of the north–south variation and formation processes of the placers in this region, and may offer a useful reference for future exploration.