Chemistry of peridotites from ODP 109-670A
During Leg 109 of the Ocean Drilling Program, about 100 m of serpentinized peridotites were drilled on the western wall of the M.A.R. axial rift valley, 45 km south of the Kane Fracture Zone. The present study reports petrological and mineralogical data obtained from 29 small pieces of these ultrama...
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1990
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ftpangaea:oai:pangaea.de:doi:10.1594/PANGAEA.745288 2024-09-15T18:24:21+00:00 Chemistry of peridotites from ODP 109-670A Juteau, Thierry Berger, Emmanuel Cannat, Mathilde LATITUDE: 23.166600 * LONGITUDE: -45.032200 * DATE/TIME START: 1986-06-12T01:30:00 * DATE/TIME END: 1986-06-16T16:15:00 1990 application/zip, 4 datasets https://doi.pangaea.de/10.1594/PANGAEA.745288 https://doi.org/10.1594/PANGAEA.745288 en eng PANGAEA https://doi.pangaea.de/10.1594/PANGAEA.745288 https://doi.org/10.1594/PANGAEA.745288 CC-BY-3.0: Creative Commons Attribution 3.0 Unported Access constraints: unrestricted info:eu-repo/semantics/openAccess Supplement to: Juteau, Thierry; Berger, Emmanuel; Cannat, Mathilde (1990): Serpentinized, residual mantle peridotites from the M.A.R. Median Valley, ODP Hole 670A (21°10'N, 45°02'W, Leg 109): primary mineralogy and geothermometry. In: Detrick, R; Honnorez, J; Bryan, WB; Juteau, T; et al. (eds.), Proceedings of the Ocean Drilling Program, Scientific Results, College Station, TX (Ocean Drilling Program), 106/109, 27-45, https://doi.org/10.2973/odp.proc.sr.106109.117.1990 109-670A DRILL Drilling/drill rig Joides Resolution Leg109 North Atlantic Ocean Ocean Drilling Program ODP dataset publication series 1990 ftpangaea https://doi.org/10.1594/PANGAEA.74528810.2973/odp.proc.sr.106109.117.1990 2024-08-21T00:02:25Z During Leg 109 of the Ocean Drilling Program, about 100 m of serpentinized peridotites were drilled on the western wall of the M.A.R. axial rift valley, 45 km south of the Kane Fracture Zone. The present study reports petrological and mineralogical data obtained from 29 small pieces of these ultramafic rocks, including about 60% serpentinized harzburgites, 26% serpentinized lherzolites, 14% serpentinized dunites, and one sample of olivine websterite. Modal analyses show that all these rocks are plagioclase-free four-phase peridotites equilibrated in the spinel lherzolite facies. The estimated average modal composition of the sample set is about 80% olivine, 14% opx, 5% cpx, and 1% spinel, that is, a cpx-poor lherzolite. The well developed porphyroclastic structures and mineralogical characteristics of these rocks indicate their affinity with the group of residual mantle tectonites, among the abyssal peridotites. Features typical of magmatic cumulates are lacking. The high contents in Al2O3 of the cpx (average 5.4%) and of the opx (average 4.3%) porphyroclasts, the low Cr# of the spinels (average 22.9%), and the rather high content in modal cpx (about 5%), indicate a moderate percentage of melting, of the order of 10%-15%. Site 670 peridotites plot close to the least depleted mantle rocks collected in the oceans in most diagrams used to define the average trend of the ocean-floor peridotites. Microprobe traverses across the cores of the exsolved opx and cpx porphyroclasts permitted the recalculation of the magmatic compositions of these pyroxenes: the 'primitive' opx were equilibrated at about 1300°C, probably at the end of the main melting episodes, whereas the 'primitive' cpx show lower equilibration temperatures, at about 1200°C, reflecting a more complex thermal history. The subsolidus evolution is well recorded, from 1200°C to about 950CC, by the exsolved pyroxenes and the olivine and spinel phases. Unusually high blocking temperatures, close to 1000°C, indicate that the peridotite body was cooled very ... Other/Unknown Material North Atlantic PANGAEA - Data Publisher for Earth & Environmental Science ENVELOPE(-45.032200,-45.032200,23.166600,23.166600) |
institution |
Open Polar |
collection |
PANGAEA - Data Publisher for Earth & Environmental Science |
op_collection_id |
ftpangaea |
language |
English |
topic |
109-670A DRILL Drilling/drill rig Joides Resolution Leg109 North Atlantic Ocean Ocean Drilling Program ODP |
spellingShingle |
109-670A DRILL Drilling/drill rig Joides Resolution Leg109 North Atlantic Ocean Ocean Drilling Program ODP Juteau, Thierry Berger, Emmanuel Cannat, Mathilde Chemistry of peridotites from ODP 109-670A |
topic_facet |
109-670A DRILL Drilling/drill rig Joides Resolution Leg109 North Atlantic Ocean Ocean Drilling Program ODP |
description |
During Leg 109 of the Ocean Drilling Program, about 100 m of serpentinized peridotites were drilled on the western wall of the M.A.R. axial rift valley, 45 km south of the Kane Fracture Zone. The present study reports petrological and mineralogical data obtained from 29 small pieces of these ultramafic rocks, including about 60% serpentinized harzburgites, 26% serpentinized lherzolites, 14% serpentinized dunites, and one sample of olivine websterite. Modal analyses show that all these rocks are plagioclase-free four-phase peridotites equilibrated in the spinel lherzolite facies. The estimated average modal composition of the sample set is about 80% olivine, 14% opx, 5% cpx, and 1% spinel, that is, a cpx-poor lherzolite. The well developed porphyroclastic structures and mineralogical characteristics of these rocks indicate their affinity with the group of residual mantle tectonites, among the abyssal peridotites. Features typical of magmatic cumulates are lacking. The high contents in Al2O3 of the cpx (average 5.4%) and of the opx (average 4.3%) porphyroclasts, the low Cr# of the spinels (average 22.9%), and the rather high content in modal cpx (about 5%), indicate a moderate percentage of melting, of the order of 10%-15%. Site 670 peridotites plot close to the least depleted mantle rocks collected in the oceans in most diagrams used to define the average trend of the ocean-floor peridotites. Microprobe traverses across the cores of the exsolved opx and cpx porphyroclasts permitted the recalculation of the magmatic compositions of these pyroxenes: the 'primitive' opx were equilibrated at about 1300°C, probably at the end of the main melting episodes, whereas the 'primitive' cpx show lower equilibration temperatures, at about 1200°C, reflecting a more complex thermal history. The subsolidus evolution is well recorded, from 1200°C to about 950CC, by the exsolved pyroxenes and the olivine and spinel phases. Unusually high blocking temperatures, close to 1000°C, indicate that the peridotite body was cooled very ... |
format |
Other/Unknown Material |
author |
Juteau, Thierry Berger, Emmanuel Cannat, Mathilde |
author_facet |
Juteau, Thierry Berger, Emmanuel Cannat, Mathilde |
author_sort |
Juteau, Thierry |
title |
Chemistry of peridotites from ODP 109-670A |
title_short |
Chemistry of peridotites from ODP 109-670A |
title_full |
Chemistry of peridotites from ODP 109-670A |
title_fullStr |
Chemistry of peridotites from ODP 109-670A |
title_full_unstemmed |
Chemistry of peridotites from ODP 109-670A |
title_sort |
chemistry of peridotites from odp 109-670a |
publisher |
PANGAEA |
publishDate |
1990 |
url |
https://doi.pangaea.de/10.1594/PANGAEA.745288 https://doi.org/10.1594/PANGAEA.745288 |
op_coverage |
LATITUDE: 23.166600 * LONGITUDE: -45.032200 * DATE/TIME START: 1986-06-12T01:30:00 * DATE/TIME END: 1986-06-16T16:15:00 |
long_lat |
ENVELOPE(-45.032200,-45.032200,23.166600,23.166600) |
genre |
North Atlantic |
genre_facet |
North Atlantic |
op_source |
Supplement to: Juteau, Thierry; Berger, Emmanuel; Cannat, Mathilde (1990): Serpentinized, residual mantle peridotites from the M.A.R. Median Valley, ODP Hole 670A (21°10'N, 45°02'W, Leg 109): primary mineralogy and geothermometry. In: Detrick, R; Honnorez, J; Bryan, WB; Juteau, T; et al. (eds.), Proceedings of the Ocean Drilling Program, Scientific Results, College Station, TX (Ocean Drilling Program), 106/109, 27-45, https://doi.org/10.2973/odp.proc.sr.106109.117.1990 |
op_relation |
https://doi.pangaea.de/10.1594/PANGAEA.745288 https://doi.org/10.1594/PANGAEA.745288 |
op_rights |
CC-BY-3.0: Creative Commons Attribution 3.0 Unported Access constraints: unrestricted info:eu-repo/semantics/openAccess |
op_doi |
https://doi.org/10.1594/PANGAEA.74528810.2973/odp.proc.sr.106109.117.1990 |
_version_ |
1810464681640329216 |