Three types of eclogites were identified in the Xiaoxinzhuang area in the northern Sulu ultrahigh pressure (UHP) terrene based on their petrographic, compositional characteristics and locations. They are composed of garnet, omphacite, amphibole, epidote, phengite, quartz/coesite, rutile, apatite, ilmenite and kyanite. Garnet in eclogite exhibits weak compositional zoning, which shows an increase in Xgr and a decrease in Xpy from core to mantle, and a decrease in Xgr and a slight increase in Xpy from mantle to rim. Phengite inclusions in garnet show higher Si, up to 3.424 p.f.u., than those in the matrix. Pseudosections calculated using THERMOCALC in the NCKFMASHTO system for three representative samples record three stages of metamorphism: (I) prograde stage, (II) post- Pmax decompression and heating to the Tmax stage and (III) retrograde stage. Stage-I was recorded in garnet cores with mineral assemblage of garnet + omphacite ± amphibole ± lawsonite + phengite + quartz + rutile, and the P-T condition is constrained at 23.5–26.4 kbar and 623–655 °C. The Pmax, 41.5 kbar at 801 °C, is revealed from garnet enclosed by coarse-grained garnet with the mineral assemblage of garnet + omphacite + phengite + coesite + rutile. Stage-II produced garnet rim with mineral assemblage of garnet + omphacite + amphibole + quartz + rutile + metabasite melt, which constrained the P-T conditions of 21.4–23.0 kbar and 869–924 °C. Stage-III, recorded by unzoned garnet grain with the mineral assemblage of garnet + omphacite + amphibole + ilmenite + rutile + metabasite melt, constrained P–T conditions of 13.5–16.4 kbar and 813–852 °C. The data suggest that the rocks in the Xiaoxinzhuang area were subducted to a depth of over 135 km and underwent an UHP metamorphism. The P-T-t path revealed by the Xiaoxinzhuang eclogites is different from those in other areas of the Sulu UHP terrane, suggesting that they represent different rock slices during the subduction and exhumations.

Eclogites from the Guanshan and Yangkou areas of the Sulu orogen consist of garnet, omphacite, phengite, amphibole, quartz/coesite, rutile, and ilmenite. Garnet exhibits weak compositional zoning where Xgr decreases from the core to the mantle and then increases towards the rim, coupled with an increase in Xpy from the core to the mantle and then decrease towards the rim. Phase equilibria modelling with pseudosections calculated using THERMOCALC in the NCKFMASHTO system for the Guanshan and Yangkou eclogites records two stages of metamorphism: (I) prograde associated with quick subduction (Stage-I) and (II) retrograde associated with quick exhumation (Stage-II). Stage-I is recorded in the core-mantle zoning of garnet and Si content in phengite in the Guanshan and Yangkou eclogites with a mineral assemblage of Grt-Omp-Amp-Phg-Qtz-Rt ± Lws, and the P-T conditions are constrained at 22–26 kbar and 600–615 °C in Guanshan, while 24–26 kbar and 595–600 °C in Yangkou. The peak P-T conditions (Pmax = 33 kbar; T = 685 °C) of Guanshan eclogites are revealed by the maximum Si content in phengite and the minimum Xgr in the garnet mantle with the mineral assemblage of Grt-Omp-Phg-Coe-Rt ± Lws. The value of Pmax suggests that the subduction depth of the Guanshan eclogites exceeds 110 km. Stage-II is recorded in the mantle-rim zoning of garnet, and its P-T conditions are estimated to be 12–15 kbar and 780–820 °C for the Guanshan eclogites reflected by the assemblage of Grt-Omp-Amp-Pl-LL-Qtz-Rt ± ilm, and 13–14 kbar and 770–790 °C for the Yangkou eclogites by the assemblage of Grt-Omp-Amp-Pl-LL-Qtz-Rt. The two stages of metamorphism in the study areas are overall consistent with the regional metamorphic events, from ultra-high-pressure eclogite facies, through high pressure eclogite facies, to amphibole eclogite facies, with the ages of 245, 227 and 195 Ma, respectively.

The Duobaoshan (DBS)-Tongshan (TS) porphyry Cu–(Mo) deposit (4.4 Mt Cu, 0.15 Mt Mo) is located in the northeastern part of the central Asian orogenic belt (CAOB) in northeastern China. It is hosted by early Ordovician dioritic to granodioritic intrusions which are characterized by the subduction-related geochemical signatures including high concentrations of large ion lithophile elements (LILEs) and light rare earth elements (LREEs), and low concentrations of heavy REEs (HREEs) and high-field -strength elements (HFSEs), such as Nb, Ta, Zr and Ti in bulk rock compositions. Furthermore, they show adakitic geochemical signatures of high Sr/Y ratios (29~55) due to high Sr (290~750 ppm) and low Y (<18 ppm). Zircon trace element abundances and published Sr-Nd-Hf isotope data of these rocks suggest that the parental magmas for these ore-bearing intrusions were rich in H2O and formed by partial melting of a juvenile lower crust/lithospheric mantle or metasomatized mantle wedge during the northwestward subduction of the Paleo-Asian Ocean before the collision of the Songnen block with the Erguna-Xing’an amalgamated block in the early Carboniferous. Values of Ce4+/Ce3+ and Ce/Nd in zircons are 307~461 and 14.1~20.3 for mineralized granodiorites, and 231~350 and 12.4~18.2 for variably altered diorite and granodiorites in DBS, whereas those for DBS-TS microgabbros are 174~357 and 7.4~22, and 45.9~62.6 and 5.0~5.8 for the early Mosozoic Qz-monzonites, respectively. Zircon Eu/Eu* values are high and similar among mineralized granodiorites (~0.6), altered diorite and granodiorites (~0.6) and the Mesozoic Qz-monzonites (~0.8), whereas the values are low and variable for the DBS-TS microgabbros (0.3~0.6). The magma oxidation state calculated from zircon chemistry and whole rock compositions are FMQ +1.0 to +1.5 in mineralized samples, and FMQ +2.4 to +4.2 in altered samples. The values are comparable to those for the fertile intrusions hosting porphyry Cu-Mo-(Au) deposits in the central and western CAOB and elsewhere in the world. Elevated oxidation state is also observed in the TS microgabbros, FMQ +1.4 to +1.9, and the early Mesozoic Qz-monzonites, FMQ +2.4 to +2.5. Comparison of zircon geochemistry data from porphyry deposists elsewhere suggests that positive Ce anomalies are generally associated with fertile intrusions, but not all igneous rocks with high Ce anomalies are Cu fertile. The findings in this study are useful in exploration work and evaluating oxidation state of magmas for porphyry Cu-(Mo) deposits in the region and elsewhere.