33 research outputs found
Metamorphism of granulite facies metapelites
No full text© 2004 Dr. Laixi TongThis thesis involves a study of metamorphism and partial melting in granulite facies metapelites from three regions, the Larsemann Hills and the Rauer Group of east Antarctica, and Fishery Bay in southern Eyre Peninsula of South Australia. Along with the metamorphic study, thermochronological dating was also undertaken for the first two areas to constrain the timing of tectonothermal events and syn- to post-tectonic cooling history. (From Abstract
Diverse PT paths of the northern Dabie complex in central China and its reworking in the early Cretaceous
No full textAssemblages and textural evolution of UHP eclogites from the Chinese Continental Scientific Drilling main hole
No full textPolymetamorphic evolution of the Vestfold Block in East Antarctica and implications for the amalgamation of terranes
No full textSHRIMP zircon age constraints from the Larsemann Hills region, Prydz Bay, for a late Mesoproterozoic to early Neoproterozoic tectono-thermal event in East Antarctica
No full textMetamorphic evidence of the Kuunga orogeny in South China: High-pressure pelitic granulites and gneisses from the Gaozhou Complex
No full textThe role of the South China Block in the Kuunga orogeny, a pivotal event marking the assembly of the Gondwana supercontinent, remains a subject of debate. This study investigates high-pressure (high-P) granulite-facies metamorphism in the Yunkai orogen of eastern South China to shed light on this controversy. Recently, high-P pelitic granulites with a mineral assemblage of garnet, K-feldspar, and sillimanite pseudomorph replacing earlier kyanite were identified in the Gaozhou Complex. Petrographic observations, phase equilibria modeling, geothermobarometry, and laser ablation−inductively coupled plasma−mass spectrometry (LA-ICP-MS) zircon U-Pb dating have revealed a four-stage metamorphic evolution. The peak P stage (M1) is characterized by high-P conditions of 10−11.8 kbar/760−830 °C in the kyanite and rutile stability fields. This is followed by the peak temperature (T) metamorphism (M2) at slightly lower pressures and higher temperatures of 7.8−9.5 kbar/840−870 °C, which suggests a subsequent period of thermal relaxation. Subsequent decompression and cooling (M3) led to the formation of cordierite + spinel coronae, which reflects a change in P-T conditions to 4.5−5.3 kbar/730−790 °C. The final retrogression (M4) occurred under lower-grade conditions of 3.7−4.4 kbar/600−640 °C. Consequently, high-P pelitic granulites in this region have undergone a clockwise P-T path, which indicates a continental collision setting. Zircon U-Pb dating from the high-P granulites and gneisses yielded multistage metamorphic ages of ca. 520 Ma, ca. 440 Ma, and ca. 240 Ma, which correspond to the Pan-African, Caledonian, and Indosinian tectono-thermal events, respectively. These metamorphic ages, coupled with the clockwise P-T path, reveal a history of polymetamorphism associated with a long-lived subduction−continental collision event during the assembly of Gondwana and the subsequent Indosinian overprinting. These multiple orogenic processes provide significant insights into the tectonic evolution of the South China Block. Our findings contribute to the evidence of the Kuunga orogeny in South China during the assembly of Gondwana and offer a robust framework for interpreting the complex metamorphic histories of orogenic belts
Emplacement age of the Songshugou ultramafic massif in the Qinling orogenic belt, and geologic implications
No full textConfirmation of ultrahigh-temperature metapelitic granulite in the Altay orogen and its geological significance
No full textZircon U-Pb Ages from an Ultra-High Temperature Metapelite, Rauer Group, East Antarctica: Implications for Overprints by Grenvillian and Pan-African Events
No full textProlonged metamorphism of garnet-orthoamphibole gneisses from the Fuyun area: New insights into metamorphic evolution of the southern Chinese Altai orogen
No full textGarnet-orthoamphibole gneisses (GOG) represent a metamorphic lithology originated from hydrothermally altered metasediments or metabasites, and usually comprise low-variance mineral assemblages and are suitable to recover the P-T trajectory. In this study, we firstly report the occurrence of the GOG in the southern Chinese Altai orogen, NW China. Revealing metamorphic P-T-t path for GOG is crucial for better understanding of the orogenic evolution. Petrographic observations, mineral chemistry and phase equilibrium modeling suggest a three-stage metamorphic evolution: 1) M1 assemblage mainly consists of garnet + hornblende + gedrite + biotite + plagioclase + quartz + sillimanite + rutile +/- ilmenite, with P-T conditions of 7.7-9.0 kbar and 700-790 degrees C; 2) M2 stage is represented by symplectitic intergrowths of orthopyroxene + cordierite + ilmenite and local presence of spinel, with P-T conditions of 5.9-6.5 kbar and 800-880 degrees C; and 3) M3 stage is characterized by an assemblage of anthophyllite/biotite + plagioclase + quartz + ilmenite + cordierite +/- staurolite, with P-T conditions of 5-6 kbar and 80 Ma) may have witnessed a long-lasting tectonic evolution from continent-arc collision (i.e. between the Junggar terrane and the Chinese Altai orogen) to post-orogenic extension in the late Paleozoic. The latter episode was likely companied by underplating and intruding of mantle-derived magmas as a result of the slab break-off or the nearby Tarim mantle plume activity
