Sm–Nd, Sr, C and O isotope systematics in hydrothermal calcite–fluorite veins: Implications for fluid–rock reaction and geochronology
Saved in:
| Title: | Sm–Nd, Sr, C and O isotope systematics in hydrothermal calcite–fluorite veins: Implications for fluid–rock reaction and geochronology |
|---|---|
| Authors: | Barker, Shaun L.L. sbarker@eos.ubc.ca, Bennett, Vickie C.1 vickie.bennett@anu.edu.au, Cox, Stephen F.1 stephen.cox@anu.edu.au, Norman, Marc D.1 marc.norman@anu.edu.au, Gagan, Michael K.1 michael.gagan@anu.edu.au |
| Source: | Chemical Geology. Oct2009, Vol. 268 Issue 1/2, p58-66. 9p. |
| Subjects: | Isotope geology, Geological time scales, Calcite, Fluorite, Neodymium, Strontium isotopes, Limestone |
| Geographic Terms: | Australia |
| Abstract: | Abstract: The 147Sm–143Nd isotope system may be used to determine the age of hydrothermal vein growth for single veins, or sets of veins, providing that the minerals in these veins formed from a hydrothermal fluid with initially homogeneous 143Nd/144Nd. In this study, we determined the 147Sm–143Nd, 87Sr/86Sr, δ 13C and δ 18O isotopic composition of 9 calcite and fluorite veins (comprising 12 samples in total) that form part of a low-temperature (100–200°C) fault and fracture hosted hydrothermal system, in the eastern Lachlan Fold Belt, Australia. The vein swarm is hosted by mid-Devonian limestones, which were folded around 350–325Ma, with vein growth occurring during folding. The veins chosen for analysis yield homogeneous Sr isotopic compositions (87Sr/86Sr=0.70851±0.00003) and δ 1 8O isotope values (22.5±0.1‰), which are similar to those of the host limestones. The homogeneity of Sr and O isotope compositions is attributed to the progressive reaction of fluids with host rock, with sufficient reaction occurring along discrete fluid flow pathways to fully equilibrate the fluids for these isotope systems. By contrast, 143Nd/144Nd isotope compositions for the same samples show more variation (143Nd/144Nd=0.51259–0.51199), which significantly exceeds analytical error. In addition, calcite and fluorite from within the same vein have distinctly different age-corrected Nd isotope compositions. Accordingly, it is likely that fluorite and calcite precipitated from different fluids. This study indicates that apparently synchronous vein-forming fluids, as suggested by structural relationships, may have diverse isotopic characteristics even over relatively small scales, reflecting variable equilibration of the fluids with the host-rocks. Incomplete equilibration or mixing, resulting in a range of initial 143Nd/144Nd compositions, is likely to be a common characteristic of fracture-hosted hydrothermal systems, compromising attempts to determine ages using Sm–Nd isochrons. The formation of veins with essentially identical Sr and O isotope compositions, yet diverse initial 143Nd/144Nd ratios, means that Sr and O isotopes cannot be used to identify suitable samples for Sm–Nd geochronological studies. [Copyright &y& Elsevier] |
| Copyright of Chemical Geology is the property of Elsevier B.V. and its content may not be copied or emailed to multiple sites without the copyright holder's express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.) | |
| Database: | Engineering Source |
| FullText | Text: Availability: 0 |
|---|---|
| Header | DbId: egs DbLabel: Engineering Source An: 44472000 AccessLevel: 6 PubType: Academic Journal PubTypeId: academicJournal PreciseRelevancyScore: 0 |
| IllustrationInfo | |
| Items | – Name: Title Label: Title Group: Ti Data: Sm–Nd, Sr, C and O isotope systematics in hydrothermal calcite–fluorite veins: Implications for fluid–rock reaction and geochronology – Name: Author Label: Authors Group: Au Data: <searchLink fieldCode="AR" term="%22Barker%2C+Shaun+L%2EL%2E%22">Barker, Shaun L.L.</searchLink><i> sbarker@eos.ubc.ca</i><br /><searchLink fieldCode="AR" term="%22Bennett%2C+Vickie+C%2E%22">Bennett, Vickie C.</searchLink><relatesTo>1</relatesTo><i> vickie.bennett@anu.edu.au</i><br /><searchLink fieldCode="AR" term="%22Cox%2C+Stephen+F%2E%22">Cox, Stephen F.</searchLink><relatesTo>1</relatesTo><i> stephen.cox@anu.edu.au</i><br /><searchLink fieldCode="AR" term="%22Norman%2C+Marc+D%2E%22">Norman, Marc D.</searchLink><relatesTo>1</relatesTo><i> marc.norman@anu.edu.au</i><br /><searchLink fieldCode="AR" term="%22Gagan%2C+Michael+K%2E%22">Gagan, Michael K.</searchLink><relatesTo>1</relatesTo><i> michael.gagan@anu.edu.au</i> – Name: TitleSource Label: Source Group: Src Data: <searchLink fieldCode="JN" term="%22Chemical+Geology%22">Chemical Geology</searchLink>. Oct2009, Vol. 268 Issue 1/2, p58-66. 9p. – Name: Subject Label: Subjects Group: Su Data: <searchLink fieldCode="DE" term="%22Isotope+geology%22">Isotope geology</searchLink><br /><searchLink fieldCode="DE" term="%22Geological+time+scales%22">Geological time scales</searchLink><br /><searchLink fieldCode="DE" term="%22Calcite%22">Calcite</searchLink><br /><searchLink fieldCode="DE" term="%22Fluorite%22">Fluorite</searchLink><br /><searchLink fieldCode="DE" term="%22Neodymium%22">Neodymium</searchLink><br /><searchLink fieldCode="DE" term="%22Strontium+isotopes%22">Strontium isotopes</searchLink><br /><searchLink fieldCode="DE" term="%22Limestone%22">Limestone</searchLink> – Name: SubjectGeographic Label: Geographic Terms Group: Su Data: <searchLink fieldCode="DE" term="%22Australia%22">Australia</searchLink> – Name: Abstract Label: Abstract Group: Ab Data: Abstract: The 147Sm–143Nd isotope system may be used to determine the age of hydrothermal vein growth for single veins, or sets of veins, providing that the minerals in these veins formed from a hydrothermal fluid with initially homogeneous 143Nd/144Nd. In this study, we determined the 147Sm–143Nd, 87Sr/86Sr, δ 13C and δ 18O isotopic composition of 9 calcite and fluorite veins (comprising 12 samples in total) that form part of a low-temperature (100–200°C) fault and fracture hosted hydrothermal system, in the eastern Lachlan Fold Belt, Australia. The vein swarm is hosted by mid-Devonian limestones, which were folded around 350–325Ma, with vein growth occurring during folding. The veins chosen for analysis yield homogeneous Sr isotopic compositions (87Sr/86Sr=0.70851±0.00003) and δ 1 8O isotope values (22.5±0.1‰), which are similar to those of the host limestones. The homogeneity of Sr and O isotope compositions is attributed to the progressive reaction of fluids with host rock, with sufficient reaction occurring along discrete fluid flow pathways to fully equilibrate the fluids for these isotope systems. By contrast, 143Nd/144Nd isotope compositions for the same samples show more variation (143Nd/144Nd=0.51259–0.51199), which significantly exceeds analytical error. In addition, calcite and fluorite from within the same vein have distinctly different age-corrected Nd isotope compositions. Accordingly, it is likely that fluorite and calcite precipitated from different fluids. This study indicates that apparently synchronous vein-forming fluids, as suggested by structural relationships, may have diverse isotopic characteristics even over relatively small scales, reflecting variable equilibration of the fluids with the host-rocks. Incomplete equilibration or mixing, resulting in a range of initial 143Nd/144Nd compositions, is likely to be a common characteristic of fracture-hosted hydrothermal systems, compromising attempts to determine ages using Sm–Nd isochrons. The formation of veins with essentially identical Sr and O isotope compositions, yet diverse initial 143Nd/144Nd ratios, means that Sr and O isotopes cannot be used to identify suitable samples for Sm–Nd geochronological studies. [Copyright &y& Elsevier] – Name: AbstractSuppliedCopyright Label: Group: Ab Data: <i>Copyright of Chemical Geology is the property of Elsevier B.V. and its content may not be copied or emailed to multiple sites without the copyright holder's express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract.</i> (Copyright applies to all Abstracts.) |
| PLink | https://search.ebscohost.com/login.aspx?direct=true&site=eds-live&db=egs&AN=44472000 |
| RecordInfo | BibRecord: BibEntity: Identifiers: – Type: doi Value: 10.1016/j.chemgeo.2009.07.009 Languages: – Code: eng Text: English PhysicalDescription: Pagination: PageCount: 9 StartPage: 58 Subjects: – SubjectFull: Isotope geology Type: general – SubjectFull: Geological time scales Type: general – SubjectFull: Calcite Type: general – SubjectFull: Fluorite Type: general – SubjectFull: Neodymium Type: general – SubjectFull: Strontium isotopes Type: general – SubjectFull: Limestone Type: general – SubjectFull: Australia Type: general Titles: – TitleFull: Sm–Nd, Sr, C and O isotope systematics in hydrothermal calcite–fluorite veins: Implications for fluid–rock reaction and geochronology Type: main BibRelationships: HasContributorRelationships: – PersonEntity: Name: NameFull: Barker, Shaun L.L. – PersonEntity: Name: NameFull: Bennett, Vickie C. – PersonEntity: Name: NameFull: Cox, Stephen F. – PersonEntity: Name: NameFull: Norman, Marc D. – PersonEntity: Name: NameFull: Gagan, Michael K. IsPartOfRelationships: – BibEntity: Dates: – D: 20 M: 10 Text: Oct2009 Type: published Y: 2009 Identifiers: – Type: issn-print Value: 00092541 Numbering: – Type: volume Value: 268 – Type: issue Value: 1/2 Titles: – TitleFull: Chemical Geology Type: main |
| ResultId | 1 |
