Geochemistry of the Ultramafic Rocks from the Bay of Island Ophiolitic Complex, Newfoundland.
The Bay of Islands Ophiolitic Complex (BOIC) is one of most well preserved and well-exposed ophiolites in the world. The BOIC consist of four massifs; these are the Table Mountain (TBL), North Arm Mountain (NAM), Blow-Me-Down Mountain (BMD) and Lewis Hills massifs. Proposed geological environments o...
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ftcanadathes:oai:collectionscanada.gc.ca:OOU.#10393/24159 2023-05-15T17:22:17+02:00 Geochemistry of the Ultramafic Rocks from the Bay of Island Ophiolitic Complex, Newfoundland. Stern, Fabio G. 2013-05-14T20:18:38Z http://hdl.handle.net/10393/24159 en eng http://hdl.handle.net/10393/24159 geochemistry ultramafic rocks Bay of Island Ophiolitic Complex Table Mountain Blow-Me-Down Mountain Lewis Hills massifs Thèse / Thesis 2013 ftcanadathes 2014-06-14T23:47:42Z The Bay of Islands Ophiolitic Complex (BOIC) is one of most well preserved and well-exposed ophiolites in the world. The BOIC consist of four massifs; these are the Table Mountain (TBL), North Arm Mountain (NAM), Blow-Me-Down Mountain (BMD) and Lewis Hills massifs. Proposed geological environments of the BOIC in Newfoundland are diverse; ranging from oceanic spreading ridge to supra-subduction setting. The BOIC has a complete ophiolite sequence as defined at the Penrose Conference (Anonymous, 1972) including ultramafic mantle rocks, ultramafic to gabbroic cumulate rocks, sheeted dikes, pillowed basaltic rocks and capping sedimentary rocks in structurally ascending order. We studied harzburgite and overlying massive dunite in the BOIC. Harzburgite is generally medium-grained, and contains olivine, orthopyroxene, Cr-spinel, clinopyroxene and rare sulfide minerals. Harzburgite is massive to strongly deformed, with local development of mylonitic shear zones. A foliation and lineation are defined by elongated and fragmented grains of orthopyroxene and Cr-spinel. Dikes, sills, veins, and irregularly-shaped bodies of dunite and pyroxenite are present throughout the harzburgite unit. Dunite is the predominant lithology of the Blow-Me-Down Mountain. It is typically fine- to medium-grained, massive, and contains minor Cr-spinel and rare sulfide minerals. Dunite contains olivine, Cr-spinel and minor pyroxenes in some samples. Olivine crystals are commonly partly replaced by serpentine along fractures and in outer rims. Bulk rock and mineral composition data suggest that harzburgites are mild to highly refractory mantle residues after partial melting. In contrast all dunite samples show a cumulate geochemical signature from a mafic melt that originated from highly refractory mantle peridotites. Our study suggest that the harzburgite in the BOIC originally formed as oceanic lithosphere at a slow spreading ridge, possibly in the vicinity of active arc systems, whereas the parental melt for dunites formed in subduction setting. The second part of this study measured trace element compositions for olivine, Cr-spinel and bulk rock of dunite. The measured bulk rock compositions are compared to those of calculated based on mineral chemistry and their abundance. This comparison suggests that the trapped melt fraction was negligible during the crystallization of the dunites. The calculated melt compositions for the dunites confirm that the melt formed in subduction setting. Thesis Newfoundland Theses Canada/Thèses Canada (Library and Archives Canada) Blow Me Down ENVELOPE(-55.148,-55.148,49.517,49.517) Blow Me Down Mountain ENVELOPE(-63.065,-63.065,58.784,58.784) Table Mountain ENVELOPE(69.031,69.031,-48.668,-48.668) |
institution |
Open Polar |
collection |
Theses Canada/Thèses Canada (Library and Archives Canada) |
op_collection_id |
ftcanadathes |
language |
English |
topic |
geochemistry ultramafic rocks Bay of Island Ophiolitic Complex Table Mountain Blow-Me-Down Mountain Lewis Hills massifs |
spellingShingle |
geochemistry ultramafic rocks Bay of Island Ophiolitic Complex Table Mountain Blow-Me-Down Mountain Lewis Hills massifs Stern, Fabio G. Geochemistry of the Ultramafic Rocks from the Bay of Island Ophiolitic Complex, Newfoundland. |
topic_facet |
geochemistry ultramafic rocks Bay of Island Ophiolitic Complex Table Mountain Blow-Me-Down Mountain Lewis Hills massifs |
description |
The Bay of Islands Ophiolitic Complex (BOIC) is one of most well preserved and well-exposed ophiolites in the world. The BOIC consist of four massifs; these are the Table Mountain (TBL), North Arm Mountain (NAM), Blow-Me-Down Mountain (BMD) and Lewis Hills massifs. Proposed geological environments of the BOIC in Newfoundland are diverse; ranging from oceanic spreading ridge to supra-subduction setting. The BOIC has a complete ophiolite sequence as defined at the Penrose Conference (Anonymous, 1972) including ultramafic mantle rocks, ultramafic to gabbroic cumulate rocks, sheeted dikes, pillowed basaltic rocks and capping sedimentary rocks in structurally ascending order. We studied harzburgite and overlying massive dunite in the BOIC. Harzburgite is generally medium-grained, and contains olivine, orthopyroxene, Cr-spinel, clinopyroxene and rare sulfide minerals. Harzburgite is massive to strongly deformed, with local development of mylonitic shear zones. A foliation and lineation are defined by elongated and fragmented grains of orthopyroxene and Cr-spinel. Dikes, sills, veins, and irregularly-shaped bodies of dunite and pyroxenite are present throughout the harzburgite unit. Dunite is the predominant lithology of the Blow-Me-Down Mountain. It is typically fine- to medium-grained, massive, and contains minor Cr-spinel and rare sulfide minerals. Dunite contains olivine, Cr-spinel and minor pyroxenes in some samples. Olivine crystals are commonly partly replaced by serpentine along fractures and in outer rims. Bulk rock and mineral composition data suggest that harzburgites are mild to highly refractory mantle residues after partial melting. In contrast all dunite samples show a cumulate geochemical signature from a mafic melt that originated from highly refractory mantle peridotites. Our study suggest that the harzburgite in the BOIC originally formed as oceanic lithosphere at a slow spreading ridge, possibly in the vicinity of active arc systems, whereas the parental melt for dunites formed in subduction setting. The second part of this study measured trace element compositions for olivine, Cr-spinel and bulk rock of dunite. The measured bulk rock compositions are compared to those of calculated based on mineral chemistry and their abundance. This comparison suggests that the trapped melt fraction was negligible during the crystallization of the dunites. The calculated melt compositions for the dunites confirm that the melt formed in subduction setting. |
format |
Thesis |
author |
Stern, Fabio G. |
author_facet |
Stern, Fabio G. |
author_sort |
Stern, Fabio G. |
title |
Geochemistry of the Ultramafic Rocks from the Bay of Island Ophiolitic Complex, Newfoundland. |
title_short |
Geochemistry of the Ultramafic Rocks from the Bay of Island Ophiolitic Complex, Newfoundland. |
title_full |
Geochemistry of the Ultramafic Rocks from the Bay of Island Ophiolitic Complex, Newfoundland. |
title_fullStr |
Geochemistry of the Ultramafic Rocks from the Bay of Island Ophiolitic Complex, Newfoundland. |
title_full_unstemmed |
Geochemistry of the Ultramafic Rocks from the Bay of Island Ophiolitic Complex, Newfoundland. |
title_sort |
geochemistry of the ultramafic rocks from the bay of island ophiolitic complex, newfoundland. |
publishDate |
2013 |
url |
http://hdl.handle.net/10393/24159 |
long_lat |
ENVELOPE(-55.148,-55.148,49.517,49.517) ENVELOPE(-63.065,-63.065,58.784,58.784) ENVELOPE(69.031,69.031,-48.668,-48.668) |
geographic |
Blow Me Down Blow Me Down Mountain Table Mountain |
geographic_facet |
Blow Me Down Blow Me Down Mountain Table Mountain |
genre |
Newfoundland |
genre_facet |
Newfoundland |
op_relation |
http://hdl.handle.net/10393/24159 |
_version_ |
1766108812690849792 |