Molecular and isotopic compositions of hydrocarbons at DSDP Site 76-533
In an investigation of gas hydrates in deep ocean sediments, gas samples from Deep Sea Drilling Project Site 533 on the Blake Outer Ridge in the northwest Atlantic were obtained for molecular and isotopic analyses. Gas samples were collected from the first successful deployment of a pressure core ba...
Main Authors: | , , , , |
---|---|
Format: | Dataset |
Language: | English |
Published: |
PANGAEA
1983
|
Subjects: | |
Online Access: | https://doi.pangaea.de/10.1594/PANGAEA.809749 https://doi.org/10.1594/PANGAEA.809749 |
id |
ftpangaea:oai:pangaea.de:doi:10.1594/PANGAEA.809749 |
---|---|
record_format |
openpolar |
spelling |
ftpangaea:oai:pangaea.de:doi:10.1594/PANGAEA.809749 2023-05-15T17:36:39+02:00 Molecular and isotopic compositions of hydrocarbons at DSDP Site 76-533 Brooks, James M Barnard, Leo A Weisenburg, Denis A Kennicutt, Mahlon C Kvenvolden, Keith A LATITUDE: 31.260000 * LONGITUDE: -74.869800 * DATE/TIME START: 1980-10-13T00:00:00 * DATE/TIME END: 1980-10-13T00:00:00 1983-04-05 application/zip, 4 datasets https://doi.pangaea.de/10.1594/PANGAEA.809749 https://doi.org/10.1594/PANGAEA.809749 en eng PANGAEA https://doi.pangaea.de/10.1594/PANGAEA.809749 https://doi.org/10.1594/PANGAEA.809749 CC-BY-3.0: Creative Commons Attribution 3.0 Unported Access constraints: unrestricted info:eu-repo/semantics/openAccess CC-BY Supplement to: Brooks, James M; Barnard, Leo A; Weisenburg, Denis A; Kennicutt, Mahlon C; Kvenvolden, Keith A (1983): Molecular and isotopic compositions of hydrocarbons at Site 533, Deep Sea Drilling Project Leg 76. In: Sheridan, RE; Gradstein, FM; et al. (eds.), Initial Reports of the Deep Sea Drilling Project, Washington (U.S. Govt. Printing Office), 76, 377-389, https://doi.org/10.2973/dsdp.proc.76.108.1983 76-533 76-533A Deep Sea Drilling Project DRILL Drilling/drill rig DSDP Glomar Challenger Leg76 North Atlantic/RIDGE Dataset 1983 ftpangaea https://doi.org/10.1594/PANGAEA.809749 https://doi.org/10.2973/dsdp.proc.76.108.1983 2023-01-20T07:32:57Z In an investigation of gas hydrates in deep ocean sediments, gas samples from Deep Sea Drilling Project Site 533 on the Blake Outer Ridge in the northwest Atlantic were obtained for molecular and isotopic analyses. Gas samples were collected from the first successful deployment of a pressure core barrel (PCB) in a hydrate region. The pressure decline curves from two of the four PCB retrievals at in situ pressures suggested the presence of small amounts of gas hydrates. Compositional and isotopic measurements of gases from several points along the pressure decline curve indicated that (1) biogenic methane (d13C = -68 per mil; C1/C2 = 5000) was the dominant gas (>90%); (2) little fractionation in the C1/C2 ratio or the C carbon isotopic composition occurred as gas hydrates decomposed during pressure decline experiments; (3) the percent of C3, i-C4, and CO2 degassed increased as the pressure declined, indicating that these molecules may help stabilize the hydrate structure; (4) excess nitrogen was present during initial degassing; and (5) C1/C2 ratios and isotopic ratios of C gases were similar to those obtained from conventional core sampling. The PCB gas also contained trace amounts of saturated, acyclic, cyclic, and aromatic C5-C14 hydrocarbons, as well as alkenes and tetrahydrothiophenes. Gas from a decomposed specimen of gas hydrate had similar molecular and isotopic ratios to the PCB gas (d13C of -68 per mil for methane and a C1/C2 ratio of about 6000). Regular trends in the d13C of methane (about -95 to -60 per mil) and C1/C2 ratios (about 25000 to 2000) were observed with depth. Capillary gas chromatography (GC) and total scanning fluorescence measurements of extracted organic material were characteristic of hydrocarbons dominated by a marine source, though significant amounts of perylene were also present. Dataset North Atlantic Northwest Atlantic PANGAEA - Data Publisher for Earth & Environmental Science ENVELOPE(-74.869800,-74.869800,31.260000,31.260000) |
institution |
Open Polar |
collection |
PANGAEA - Data Publisher for Earth & Environmental Science |
op_collection_id |
ftpangaea |
language |
English |
topic |
76-533 76-533A Deep Sea Drilling Project DRILL Drilling/drill rig DSDP Glomar Challenger Leg76 North Atlantic/RIDGE |
spellingShingle |
76-533 76-533A Deep Sea Drilling Project DRILL Drilling/drill rig DSDP Glomar Challenger Leg76 North Atlantic/RIDGE Brooks, James M Barnard, Leo A Weisenburg, Denis A Kennicutt, Mahlon C Kvenvolden, Keith A Molecular and isotopic compositions of hydrocarbons at DSDP Site 76-533 |
topic_facet |
76-533 76-533A Deep Sea Drilling Project DRILL Drilling/drill rig DSDP Glomar Challenger Leg76 North Atlantic/RIDGE |
description |
In an investigation of gas hydrates in deep ocean sediments, gas samples from Deep Sea Drilling Project Site 533 on the Blake Outer Ridge in the northwest Atlantic were obtained for molecular and isotopic analyses. Gas samples were collected from the first successful deployment of a pressure core barrel (PCB) in a hydrate region. The pressure decline curves from two of the four PCB retrievals at in situ pressures suggested the presence of small amounts of gas hydrates. Compositional and isotopic measurements of gases from several points along the pressure decline curve indicated that (1) biogenic methane (d13C = -68 per mil; C1/C2 = 5000) was the dominant gas (>90%); (2) little fractionation in the C1/C2 ratio or the C carbon isotopic composition occurred as gas hydrates decomposed during pressure decline experiments; (3) the percent of C3, i-C4, and CO2 degassed increased as the pressure declined, indicating that these molecules may help stabilize the hydrate structure; (4) excess nitrogen was present during initial degassing; and (5) C1/C2 ratios and isotopic ratios of C gases were similar to those obtained from conventional core sampling. The PCB gas also contained trace amounts of saturated, acyclic, cyclic, and aromatic C5-C14 hydrocarbons, as well as alkenes and tetrahydrothiophenes. Gas from a decomposed specimen of gas hydrate had similar molecular and isotopic ratios to the PCB gas (d13C of -68 per mil for methane and a C1/C2 ratio of about 6000). Regular trends in the d13C of methane (about -95 to -60 per mil) and C1/C2 ratios (about 25000 to 2000) were observed with depth. Capillary gas chromatography (GC) and total scanning fluorescence measurements of extracted organic material were characteristic of hydrocarbons dominated by a marine source, though significant amounts of perylene were also present. |
format |
Dataset |
author |
Brooks, James M Barnard, Leo A Weisenburg, Denis A Kennicutt, Mahlon C Kvenvolden, Keith A |
author_facet |
Brooks, James M Barnard, Leo A Weisenburg, Denis A Kennicutt, Mahlon C Kvenvolden, Keith A |
author_sort |
Brooks, James M |
title |
Molecular and isotopic compositions of hydrocarbons at DSDP Site 76-533 |
title_short |
Molecular and isotopic compositions of hydrocarbons at DSDP Site 76-533 |
title_full |
Molecular and isotopic compositions of hydrocarbons at DSDP Site 76-533 |
title_fullStr |
Molecular and isotopic compositions of hydrocarbons at DSDP Site 76-533 |
title_full_unstemmed |
Molecular and isotopic compositions of hydrocarbons at DSDP Site 76-533 |
title_sort |
molecular and isotopic compositions of hydrocarbons at dsdp site 76-533 |
publisher |
PANGAEA |
publishDate |
1983 |
url |
https://doi.pangaea.de/10.1594/PANGAEA.809749 https://doi.org/10.1594/PANGAEA.809749 |
op_coverage |
LATITUDE: 31.260000 * LONGITUDE: -74.869800 * DATE/TIME START: 1980-10-13T00:00:00 * DATE/TIME END: 1980-10-13T00:00:00 |
long_lat |
ENVELOPE(-74.869800,-74.869800,31.260000,31.260000) |
genre |
North Atlantic Northwest Atlantic |
genre_facet |
North Atlantic Northwest Atlantic |
op_source |
Supplement to: Brooks, James M; Barnard, Leo A; Weisenburg, Denis A; Kennicutt, Mahlon C; Kvenvolden, Keith A (1983): Molecular and isotopic compositions of hydrocarbons at Site 533, Deep Sea Drilling Project Leg 76. In: Sheridan, RE; Gradstein, FM; et al. (eds.), Initial Reports of the Deep Sea Drilling Project, Washington (U.S. Govt. Printing Office), 76, 377-389, https://doi.org/10.2973/dsdp.proc.76.108.1983 |
op_relation |
https://doi.pangaea.de/10.1594/PANGAEA.809749 https://doi.org/10.1594/PANGAEA.809749 |
op_rights |
CC-BY-3.0: Creative Commons Attribution 3.0 Unported Access constraints: unrestricted info:eu-repo/semantics/openAccess |
op_rightsnorm |
CC-BY |
op_doi |
https://doi.org/10.1594/PANGAEA.809749 https://doi.org/10.2973/dsdp.proc.76.108.1983 |
_version_ |
1766136217266552832 |