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Full-Text Articles in Physical Sciences and Mathematics
Pressure-Temperature-Time Constraints For Exhumation Of Ultrahigh-Pressure Metamorphic Rocks, North Qaidam Terrane, Western China, Brittany Kristine Fagin
Pressure-Temperature-Time Constraints For Exhumation Of Ultrahigh-Pressure Metamorphic Rocks, North Qaidam Terrane, Western China, Brittany Kristine Fagin
All Master's Theses
Ultrahigh-pressure rocks of a Paleozoic continental suture zone are exposed in the southeastern North Qaidam terrane (Dulan region). Garnetite sample D119 contains minor Czo+Qtz+Chl+Ttn; rutile inclusions in titanite suggest that titanite replaced rutile during decompression. Pressure-temperature estimates of sample D119 are 16.1-18.4 kbar and 485-520 °C. Sample D130B is a mafic band in calc-silicate gneiss, with garnet porphyroblasts in a fine-grained Hbl-Cpx-Pl-Qtz symplectite that is interpreted as former omphacite. D130B symplectite pressure-temperature estimates are 7.7-9.4 kbar and 623-708 °C. Titanite U-Pb ages of 419.7±3.1 Ma and 415.9±4.2 Ma are interpreted to date retrogression of D119 and D130B, respectively. Average exhumation …
Thermobarometry And Geochronology In The Dulan Region, North Qaidam Ultrahigh-Pressure Terrane: Resolving Spatial Variation Of Ages, Temperatures, And Pressures, Megan Eileen Regel
Thermobarometry And Geochronology In The Dulan Region, North Qaidam Ultrahigh-Pressure Terrane: Resolving Spatial Variation Of Ages, Temperatures, And Pressures, Megan Eileen Regel
All Master's Theses
The Dulan ultrahigh-pressure (UHP) terrane exposes 449-422 Ma eclogites in the east and 449-418 Ma high-pressure granulites to the west, but the relationship between the units is poorly understood. Zirconium-in-rutile temperatures show an east-west 3- 5°C/km gradient in four UHP eclogites: 662-716±10°C; garnet-omphacite-phengite thermobarometry of peak conditions yields 659-730±82°C, 25.3-27.1±3.2 kbars. Zircon U-Pb ages of four eclogites are the same within uncertainty, averaging 434±2.9 Ma. Tiin- zircon thermometry and rare earth element patterns indicate these ages represent eclogite facies metamorphism. One high-pressure/high-temperature (HP/HT) granulite yields a minimum rutile temperature of 773±4°C. Previous thermobarometry of highpressure granulites yields ≥800°C and 14-17 …
Geochemistry, Geothermobarometry And Geochronology Of High-Pressure Granulites And Implications For The Exhumation History Of Ultrahigh-Pressure Terranes: Dulan, Western China, Benjamin David Joseph Christensen
Geochemistry, Geothermobarometry And Geochronology Of High-Pressure Granulites And Implications For The Exhumation History Of Ultrahigh-Pressure Terranes: Dulan, Western China, Benjamin David Joseph Christensen
All Master's Theses
The Dulan ultrahigh-pressure (UHP) rocks of the North Qaidam terrane, Western China, represent continental crust that has been subducted ~100 km during continental collision. Adjacent granulites representing burial to ~50 km could either be overprinted eclogites or a separate high-pressure-high-temperature (HP-HT) granulite unit. Overprinted eclogites and HP-HT granulites imply different P-T-t paths for UHP rocks. Metamorphic conditions for the granulites are 750–880 °C and 14–17 kbar. Zircon U-Pb geochronology, REE patterns and Ti-in-zircon thermometry indicate an increase in temperature from ~800 °C (449 Ma) to ~900 °C (418 Ma). This temperature increase could explain the presence of granulite leucosomes and …