{"id":{"repo_id":"central-wash","oai_identifier":"oai:digitalcommons.cwu.edu:etd-1647"},"canonical_url":"https://search.dev.ndltd.org/etd/central-wash/oai:digitalcommons.cwu.edu:etd-1647","repository":{"repo_id":"central-wash","name":"Central Washington University","base_url":"https://digitalcommons.cwu.edu/do/oai/"},"display":{"title":"Estimating the thickness of an ultrahigh-pressure (UHP) terrane: insights from phase equilibria modelling and Zr-in-rutile thermometry, Dulan area, North Qaidam terrane, China","abstract":"The North Qaidam UHP terrane, in western China, exposes minor UHP eclogites hosted by ortho- and paragneisses. In the southeastern part of the terrane, the Dulan area exposes eclogite with the mineral assemblage Grt + Omp ± Ky ± Ph ± Zo ± Qz/Coe. LASS U-Pb analyses of zircons yield weighted mean ages of 463-425 Ma, and REE patterns indicate that these ages record the eclogite-facies metamorphism. Inherited zircon cores yield ages of 928-905 Ma, and REE patterns indicate that the eclogite´s protolith had a magmatic origin. Zr-in-rutile thermometry reveals that Dulan eclogites record peak temperatures of 647-711°C. Spatially distributed peak temperatures show an east-west temperature gradient of ~1 °C km-1 and a slow temperature increase of ~1 °C Myr-1. Our results indicate that retrogression can modify the original rutile´s Zr and Nb content, and therefore the obtained Zr-in-rutile temperatures. Phase equilibria modelling and Zr-in-rutile thermometry of four eclogites indicate they reached peak metamorphic iv conditions at ~26-32 kbar and ~630-690 °C. Coupling garnet mode isopleths with Grs isopleths appears to be a powerful approach to build P-T paths in eclogites where the original garnet composition has been modified by diffusion. The prograde path determined from one sample indicates that the eclogite followed a gradient of ~4-8 °C km-1, and underwent prograde metamorphism through the lawsonite stability field. The presence of retrograde amphibole and zoisite suggests that hydration happened during early retrogression, at ~23 kbar and <750 °C. Pressure fluctuations in the P-T path suggest that the Dulan area experienced subduction and exhumation cycles. Our results indicate that the Dulan area experienced slow heating, and a protracted eclogite-facies metamorphism (~38 Myr). Comparing predictions of thermal models to both the shape pf the P-T path and to the range of peak temperatures from spatially distributed samples suggests that the Dulan UHP area exhumed as part of a body at least 3-4 km thick.","abstract_html":"The North Qaidam UHP terrane, in western China, exposes minor UHP eclogites hosted by ortho- and paragneisses. In the southeastern part of the terrane, the Dulan area exposes eclogite with the mineral assemblage Grt + Omp ± Ky ± Ph ± Zo ± Qz/Coe. LASS U-Pb analyses of zircons yield weighted mean ages of 463-425 Ma, and REE patterns indicate that these ages record the eclogite-facies metamorphism. Inherited zircon cores yield ages of 928-905 Ma, and REE patterns indicate that the eclogite´s protolith had a magmatic origin. Zr-in-rutile thermometry reveals that Dulan eclogites record peak temperatures of 647-711°C. Spatially distributed peak temperatures show an east-west temperature gradient of ~1 °C km-1 and a slow temperature increase of ~1 °C Myr-1. Our results indicate that retrogression can modify the original rutile´s Zr and Nb content, and therefore the obtained Zr-in-rutile temperatures. Phase equilibria modelling and Zr-in-rutile thermometry of four eclogites indicate they reached peak metamorphic iv conditions at ~26-32 kbar and ~630-690 °C. Coupling garnet mode isopleths with Grs isopleths appears to be a powerful approach to build P-T paths in eclogites where the original garnet composition has been modified by diffusion. The prograde path determined from one sample indicates that the eclogite followed a gradient of ~4-8 °C km-1, and underwent prograde metamorphism through the lawsonite stability field. The presence of retrograde amphibole and zoisite suggests that hydration happened during early retrogression, at ~23 kbar and &lt;750 °C. Pressure fluctuations in the P-T path suggest that the Dulan area experienced subduction and exhumation cycles. Our results indicate that the Dulan area experienced slow heating, and a protracted eclogite-facies metamorphism (~38 Myr). Comparing predictions of thermal models to both the shape pf the P-T path and to the range of peak temperatures from spatially distributed samples suggests that the Dulan UHP area exhumed as part of a body at least 3-4 km thick.","abstract_has_math":false,"creators":["Hernández Uribe, David"],"institution":null,"degree_name":"Master of Science (MS)","degree_level":null,"degree_discipline":"Geological Sciences","degree_department":null,"school":null,"contributors":["Chris Mattinson","Wendy A. Bohrson","Audrey Huerta"],"advisors":[],"committee_chairs":[],"committee_members":[],"year":2017,"date_issued":"2017-01-01T08:00:00Z","date_published":"2017-01-01T08:00:00Z","updated_at":"2026-07-24T01:37:04Z","subjects":["North Qaidam","ultrahigh-pressure metamorphism","phase equilibria modelling","Zr-in-rutile","Earth Sciences","Geology","Physical Sciences and Mathematics"],"languages":["English"],"rights":[],"rights_urls":[],"identifier_entries":[]},"links":{"outbound_url":"https://digitalcommons.cwu.edu/etd/631","outbound_label":"Repository record","outbound_source":"dc:identifier"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor","label":"Contributor","values":["Chris Mattinson","Wendy A. Bohrson","Audrey Huerta"]},{"key":"dc:creator","label":"Author","values":["Hernández Uribe, David"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date.available","label":"Dc Date Available","values":["2022-06-14T07:00:00Z"]},{"key":"dc:type","label":"Dc Type","values":["Text"]},{"key":"thesis:degree_discipline","label":"Discipline","values":["Geological Sciences"]},{"key":"thesis:degree_name","label":"Degree Name","values":["Master of Science (MS)"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["North Qaidam","ultrahigh-pressure metamorphism","phase equilibria modelling","Zr-in-rutile","Earth Sciences","Geology","Physical Sciences and Mathematics"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:language","label":"Dc Language","values":["English"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier","label":"Identifier","values":["https://digitalcommons.cwu.edu/etd/631"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description.abstract","label":"Abstract","values":["The North Qaidam UHP terrane, in western China, exposes minor UHP eclogites hosted by ortho- and paragneisses. In the southeastern part of the terrane, the Dulan area exposes eclogite with the mineral assemblage Grt + Omp ± Ky ± Ph ± Zo ± Qz/Coe. LASS U-Pb analyses of zircons yield weighted mean ages of 463-425 Ma, and REE patterns indicate that these ages record the eclogite-facies metamorphism. Inherited zircon cores yield ages of 928-905 Ma, and REE patterns indicate that the eclogite´s protolith had a magmatic origin. Zr-in-rutile thermometry reveals that Dulan eclogites record peak temperatures of 647-711°C. Spatially distributed peak temperatures show an east-west temperature gradient of ~1 °C km-1 and a slow temperature increase of ~1 °C Myr-1. Our results indicate that retrogression can modify the original rutile´s Zr and Nb content, and therefore the obtained Zr-in-rutile temperatures. Phase equilibria modelling and Zr-in-rutile thermometry of four eclogites indicate they reached peak metamorphic iv conditions at ~26-32 kbar and ~630-690 °C. Coupling garnet mode isopleths with Grs isopleths appears to be a powerful approach to build P-T paths in eclogites where the original garnet composition has been modified by diffusion. The prograde path determined from one sample indicates that the eclogite followed a gradient of ~4-8 °C km-1, and underwent prograde metamorphism through the lawsonite stability field. The presence of retrograde amphibole and zoisite suggests that hydration happened during early retrogression, at ~23 kbar and <750 °C. Pressure fluctuations in the P-T path suggest that the Dulan area experienced subduction and exhumation cycles. Our results indicate that the Dulan area experienced slow heating, and a protracted eclogite-facies metamorphism (~38 Myr). Comparing predictions of thermal models to both the shape pf the P-T path and to the range of peak temperatures from spatially distributed samples suggests that the Dulan UHP area exhumed as part of a body at least 3-4 km thick."]},{"key":"dc:title","label":"Title","values":["Estimating the thickness of an ultrahigh-pressure (UHP) terrane: insights from phase equilibria modelling and Zr-in-rutile thermometry, Dulan area, North Qaidam terrane, China"]}]}],"canonical_facts":{"dc:contributor":["Chris Mattinson","Wendy A. Bohrson","Audrey Huerta"],"dc:creator":["Hernández Uribe, David"],"dc:date.available":["2022-06-14T07:00:00Z"],"dc:description.abstract":["The North Qaidam UHP terrane, in western China, exposes minor UHP eclogites hosted by ortho- and paragneisses. In the southeastern part of the terrane, the Dulan area exposes eclogite with the mineral assemblage Grt + Omp ± Ky ± Ph ± Zo ± Qz/Coe. LASS U-Pb analyses of zircons yield weighted mean ages of 463-425 Ma, and REE patterns indicate that these ages record the eclogite-facies metamorphism. Inherited zircon cores yield ages of 928-905 Ma, and REE patterns indicate that the eclogite´s protolith had a magmatic origin. Zr-in-rutile thermometry reveals that Dulan eclogites record peak temperatures of 647-711°C. Spatially distributed peak temperatures show an east-west temperature gradient of ~1 °C km-1 and a slow temperature increase of ~1 °C Myr-1. Our results indicate that retrogression can modify the original rutile´s Zr and Nb content, and therefore the obtained Zr-in-rutile temperatures. Phase equilibria modelling and Zr-in-rutile thermometry of four eclogites indicate they reached peak metamorphic iv conditions at ~26-32 kbar and ~630-690 °C. Coupling garnet mode isopleths with Grs isopleths appears to be a powerful approach to build P-T paths in eclogites where the original garnet composition has been modified by diffusion. The prograde path determined from one sample indicates that the eclogite followed a gradient of ~4-8 °C km-1, and underwent prograde metamorphism through the lawsonite stability field. The presence of retrograde amphibole and zoisite suggests that hydration happened during early retrogression, at ~23 kbar and <750 °C. Pressure fluctuations in the P-T path suggest that the Dulan area experienced subduction and exhumation cycles. Our results indicate that the Dulan area experienced slow heating, and a protracted eclogite-facies metamorphism (~38 Myr). Comparing predictions of thermal models to both the shape pf the P-T path and to the range of peak temperatures from spatially distributed samples suggests that the Dulan UHP area exhumed as part of a body at least 3-4 km thick."],"dc:identifier":["https://digitalcommons.cwu.edu/etd/631"],"dc:language":["English"],"dc:subject":["North Qaidam","ultrahigh-pressure metamorphism","phase equilibria modelling","Zr-in-rutile","Earth Sciences","Geology","Physical Sciences and Mathematics"],"dc:title":["Estimating the thickness of an ultrahigh-pressure (UHP) terrane: insights from phase equilibria modelling and Zr-in-rutile thermometry, Dulan area, North Qaidam terrane, China"],"dc:type":["Text"],"thesis:degree_discipline":["Geological Sciences"],"thesis:degree_name":["Master of Science (MS)"]},"updated_at":"2026-07-24T01:37:04Z"}