Petrogenesis of Gabbro from Ultraslow-Spreading Gakkel Ridge
Petrologic evolution under mid-ocean ridges (MORs) has long been a major means to study the complex structure of the oceanic crust. Gakkel Ridge, the Arctic mid-ocean ridge, is especially interesting with its unique “ultraslow” spreading rate. Geochemical studies of Gakkel Ridge basalts and peridoti...
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ftunivhouston:oai:uh-ir.tdl.org:10657/5306 2023-05-15T15:04:53+02:00 Petrogenesis of Gabbro from Ultraslow-Spreading Gakkel Ridge Lee, Yuan-Ping 1994- Snow, Jonathan E. Brandon, Alan D. Gao, Yongjun Bittner, Eric R. 2019-08 application/pdf born digital https://hdl.handle.net/10657/5306 en eng https://hdl.handle.net/10657/5306 The author of this work is the copyright owner. UH Libraries and the Texas Digital Library have their permission to store and provide access to this work. Further transmission, reproduction, or presentation of this work is prohibited except with permission of the author(s). Gakkel Ridge Gabbro Thesis Text 2019 ftunivhouston 2022-04-03T15:46:32Z Petrologic evolution under mid-ocean ridges (MORs) has long been a major means to study the complex structure of the oceanic crust. Gakkel Ridge, the Arctic mid-ocean ridge, is especially interesting with its unique “ultraslow” spreading rate. Geochemical studies of Gakkel Ridge basalts and peridotites have shown the primitive magma to be created by a low degree of partial melting and a heterogeneous parental mantle. However, the extremely thin seismic “Layer 3”, correlated generally with gabbro, and its properties are not yet well studied. We studied the geochemistry of gabbros recovered from the AMORE program (Arctic Mid-Ocean Ridge Expedition, 2001), using Electron Probe Microanalyzer (EPMA) and LA-ICP-MS. A total of 25 thin sections from 6 stations were analyzed. The results of the clinopyoxene (cpx) Mg# (Mg/(Mg+Fe)) versus anorthite content (An% = (Ca/Ca+Na)) of the studied gabbros show a relatively low trend in An% compared to global gabbros. This implies the degree of partial melting is among the lowest compares to the global MORs. In addition, MELTS models of isobaric fractional crystallization of average Gakkel primitive basalt indicates that the SLD (solid line of descent) of (Mg# cpx vs An% plag) matches with our results quite well. Such models indicate that the SMZ (Sparsely Magmatic Zone) and the WVZ (Western Volcanic Zone) are generated with about 7.5% and 11% of partial melting respectively. Using these solid line of descent models, the major element trends can be used to predict (or infer) the thickness of the oceanic crust. The crustal thickness calculated by the Gakkel gabbros is about 2 – 4 km, in accordance with predictions made with the basalt and the seismic data that infers a cold mantle. This low-pressure melting phenomenon under Gakkel Ridge can also be determined by the lowest SLD of MgO and FeO in cpx compared to global data. Trace elements in clinopyroxene generally also show the result of crystallization of primary magmas. There seems to be little influence of the degree of partial melting. Clinopyroxene however shows us a substantial and consistent core and rim fractionation. This could be explained by melt-rock reaction or in-situ crystallization. Earth and Atmospheric Sciences, Department of Thesis Arctic University of Houston Institutional Repository (UHIR) Arctic Gakkel Ridge ENVELOPE(90.000,90.000,87.000,87.000) |
institution |
Open Polar |
collection |
University of Houston Institutional Repository (UHIR) |
op_collection_id |
ftunivhouston |
language |
English |
topic |
Gakkel Ridge Gabbro |
spellingShingle |
Gakkel Ridge Gabbro Lee, Yuan-Ping 1994- Petrogenesis of Gabbro from Ultraslow-Spreading Gakkel Ridge |
topic_facet |
Gakkel Ridge Gabbro |
description |
Petrologic evolution under mid-ocean ridges (MORs) has long been a major means to study the complex structure of the oceanic crust. Gakkel Ridge, the Arctic mid-ocean ridge, is especially interesting with its unique “ultraslow” spreading rate. Geochemical studies of Gakkel Ridge basalts and peridotites have shown the primitive magma to be created by a low degree of partial melting and a heterogeneous parental mantle. However, the extremely thin seismic “Layer 3”, correlated generally with gabbro, and its properties are not yet well studied. We studied the geochemistry of gabbros recovered from the AMORE program (Arctic Mid-Ocean Ridge Expedition, 2001), using Electron Probe Microanalyzer (EPMA) and LA-ICP-MS. A total of 25 thin sections from 6 stations were analyzed. The results of the clinopyoxene (cpx) Mg# (Mg/(Mg+Fe)) versus anorthite content (An% = (Ca/Ca+Na)) of the studied gabbros show a relatively low trend in An% compared to global gabbros. This implies the degree of partial melting is among the lowest compares to the global MORs. In addition, MELTS models of isobaric fractional crystallization of average Gakkel primitive basalt indicates that the SLD (solid line of descent) of (Mg# cpx vs An% plag) matches with our results quite well. Such models indicate that the SMZ (Sparsely Magmatic Zone) and the WVZ (Western Volcanic Zone) are generated with about 7.5% and 11% of partial melting respectively. Using these solid line of descent models, the major element trends can be used to predict (or infer) the thickness of the oceanic crust. The crustal thickness calculated by the Gakkel gabbros is about 2 – 4 km, in accordance with predictions made with the basalt and the seismic data that infers a cold mantle. This low-pressure melting phenomenon under Gakkel Ridge can also be determined by the lowest SLD of MgO and FeO in cpx compared to global data. Trace elements in clinopyroxene generally also show the result of crystallization of primary magmas. There seems to be little influence of the degree of partial melting. Clinopyroxene however shows us a substantial and consistent core and rim fractionation. This could be explained by melt-rock reaction or in-situ crystallization. Earth and Atmospheric Sciences, Department of |
author2 |
Snow, Jonathan E. Brandon, Alan D. Gao, Yongjun Bittner, Eric R. |
format |
Thesis |
author |
Lee, Yuan-Ping 1994- |
author_facet |
Lee, Yuan-Ping 1994- |
author_sort |
Lee, Yuan-Ping 1994- |
title |
Petrogenesis of Gabbro from Ultraslow-Spreading Gakkel Ridge |
title_short |
Petrogenesis of Gabbro from Ultraslow-Spreading Gakkel Ridge |
title_full |
Petrogenesis of Gabbro from Ultraslow-Spreading Gakkel Ridge |
title_fullStr |
Petrogenesis of Gabbro from Ultraslow-Spreading Gakkel Ridge |
title_full_unstemmed |
Petrogenesis of Gabbro from Ultraslow-Spreading Gakkel Ridge |
title_sort |
petrogenesis of gabbro from ultraslow-spreading gakkel ridge |
publishDate |
2019 |
url |
https://hdl.handle.net/10657/5306 |
long_lat |
ENVELOPE(90.000,90.000,87.000,87.000) |
geographic |
Arctic Gakkel Ridge |
geographic_facet |
Arctic Gakkel Ridge |
genre |
Arctic |
genre_facet |
Arctic |
op_relation |
https://hdl.handle.net/10657/5306 |
op_rights |
The author of this work is the copyright owner. UH Libraries and the Texas Digital Library have their permission to store and provide access to this work. Further transmission, reproduction, or presentation of this work is prohibited except with permission of the author(s). |
_version_ |
1766336624498573312 |