Heterogeneous and metasomatized mantle recorded by trace elements in minerals of the Donghai garnet peridotites, Sulu UHP terrane, China

In situ trace element data for minerals in the Zhimafang lherzolite and Xugou harzburgites from the Donghai area of the Sulu UHP terrane are presented. The Zhimafang lherzolite and the Xugou harzburgite have porphyroblastic and equigranular textures respectively, and consist of olivine (Fo90.6–92.4), enstatite (En92.0–92.7), garnet (Prp63.2–87.1) and diopside (Mg#90.8–95.7) with additional minor phlogopite. Garnets from both peridotites have low LREE and show negative Ce anomalies, but Zhimafang garnet has higher HREE abundance ((HREE)n = 8–l5) than Xugou garnet ((HREE)n = 2–6). Diopsides from both peridotites have low abundances of Yb, Y and Ti, and low Ti/Eu (517–1158), but high and variable Sr/Nd (4800–22,000) and (La/Yb)n (40–100). The petrographic and geochemical characteristics suggest that the Donghai garnet peridotites were subjected to metasomatism caused by silicate-rich melts with both carbonate and hydrous components. Several episodes of metasomatism may have occurred, given the complex evolution these bodies must have undergone in the mantle and crust. The differences in mineral chemistry (such as the Ni content and Mg# of olivine, and the Y, Al, HREE, Nd/Y and Sc/Y of garnet) between Zhimafang and Xugou peridotites suggest that they are derived from a heterogeneous mantle, and the Zhimafang lherzolite was less depleted than the Xugou harzburgite. Probably they have had a different evolutionary history prior to insert into the subducted continental slab.