Late Cretaceous‐Tertiary tectonics of the southwest Pacific: Insights from U‐Pb sensitive, high‐resolution ion microprobe (SHRIMP) dating of eclogite facies rocks from New Caledonia

摘要: [1] We present new U-Pb sensitive, high-resolution ion microprobe (SHRIMP) dates for zircon from eclogite facies samples northern New Caledonia, which have important consequences the Late Cretaceous to Eocene tectonic evolution of southwest Pacific region. Two high-pressure metapelites contain zoned crystals. Cores these crystals represent inherited magmatic grains, yield an age 85 Ma in both samples. Igneous domains a metamorphosed mafic cumulate and felsic metasedimentary rock were also dated at 55 Ma. The igneous uniform rocks sedimentary origin indicates that sedimentation took place restricted source area soon after magmatism. Therefore protoliths are considered formed between back-arc basin. This time period matches unmetamorphosed Poya Terrane western Caledonia provides further evidence direct link two terranes. In metapelites, irregular rims cross cut oscillatory zoning cores low trace element Th/U contents inclusions minerals providing during metamorphism. 44.1 ± 0.9 44.5 1.2 ages obtained burial related subduction It is suggested initiated deposition youngest sediments stopped 44 attempted continental crust, now represented as Norfolk Ridge. system produced could only operated maximum 11 m.y. would been relatively hot. constraint peak metamorphism significantly predates (by 10 m.y.) timing obduction Ultramafic Nappe, discounting any Combining our results with previously documented geological data, we revised model development involves multiple episodes compression extension Eocene.