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Lithium isotope traces magmatic fluid in a seafloor hydrothermal system.

Yang D, Hou Z, Zhao Y, Hou K, Yang Z, Tian S, Fu Q - Sci Rep (2015)

Bottom Line: The δ(7)Li results vary from +4.5‰ to +13.8‰ for fluid inclusions and from +6.7‰ to +21.0‰ for the hosted gangue quartz(9 gangue quartz samples containing primary fluid inclusions).This δ(7)Li range, together with Li-O modeling , suggest that magmatic fluid played a significant role in the ore formation.This study demonstrates that Li isotope can be effectively used to trace magmatic fluids in a seafloor hydrothermal system and has the potential to monitor fluid mixing and ore-forming process.

View Article: PubMed Central - PubMed

Affiliation: Institute of Mineral Resources, CAGS, Beijing 100037, P. R. China.

ABSTRACT
Lithium isotopic compositions of fluid inclusions and hosted gangue quartz from a giant volcanogenic massive sulfide deposit in China provide robust evidence for inputting of magmatic fluids into a Triassic submarine hydrothermal system. The δ(7)Li results vary from +4.5‰ to +13.8‰ for fluid inclusions and from +6.7‰ to +21.0‰ for the hosted gangue quartz(9 gangue quartz samples containing primary fluid inclusions). These data confirm the temperature-dependent Li isotopic fractionation between hydrothermal quartz and fluid (i.e., Δδ(7)Liquartz-fluid = -8.9382 × (1000/T) + 22.22(R(2) = 0.98; 175 °C-340 °C)), which suggests that the fluid inclusions are in equilibrium with their hosted quartz, thus allowing to determine the composition of the fluids by using δ(7)Liquartz data. Accordingly, we estimate that the ore-forming fluids have a δ(7)Li range from -0.7‰ to +18.4‰ at temperatures of 175-340 °C. This δ(7)Li range, together with Li-O modeling , suggest that magmatic fluid played a significant role in the ore formation. This study demonstrates that Li isotope can be effectively used to trace magmatic fluids in a seafloor hydrothermal system and has the potential to monitor fluid mixing and ore-forming process.

No MeSH data available.


Geological map of the Gacun deposit (modified from refs. 10,12), showing sample locations and spatial distribution of the major orebodies on a 4100 m exploration plane.The Triassic volcanic-sedimentary strata were folded and steeply-dipped eastwards due to later deformation, providing an ideal cross-section that shows a rhyolitic package and the hosted orebodies from the deep (west) to top (east). Inset map shows tectonic framework of the Yidun Arc, formed by westward subduction of the Ganzi-Litang oceanic lithposhere in Triassic10. The Gacun deposit is located in an intra-arc rifting zone within the Traissic arc, and consists of three major orebodies. The location of U-Pb dating samples and the boundaries of a feeder zone of hydrothermal system10 are also shown. 53 samples for Li analyses were collected along 8 prospecting lines across orebodies at different heights (4050 m, 4100 m, 4150 m) and are shown on an exploration plane at 4100 m. Locations of all samples are marked by solid circles (at 4100 m) and open circles (at 4050 m and 4160 m). The minimal amount of seawater (Xseawater) in the ore-forming fluids for each sample was estimated by binary mixing modeling on Li-O isotopic data of 53 quartz samples (see Appendix II, Table S1, and Fig. 3). All data from Table S1.
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f1: Geological map of the Gacun deposit (modified from refs. 10,12), showing sample locations and spatial distribution of the major orebodies on a 4100 m exploration plane.The Triassic volcanic-sedimentary strata were folded and steeply-dipped eastwards due to later deformation, providing an ideal cross-section that shows a rhyolitic package and the hosted orebodies from the deep (west) to top (east). Inset map shows tectonic framework of the Yidun Arc, formed by westward subduction of the Ganzi-Litang oceanic lithposhere in Triassic10. The Gacun deposit is located in an intra-arc rifting zone within the Traissic arc, and consists of three major orebodies. The location of U-Pb dating samples and the boundaries of a feeder zone of hydrothermal system10 are also shown. 53 samples for Li analyses were collected along 8 prospecting lines across orebodies at different heights (4050 m, 4100 m, 4150 m) and are shown on an exploration plane at 4100 m. Locations of all samples are marked by solid circles (at 4100 m) and open circles (at 4050 m and 4160 m). The minimal amount of seawater (Xseawater) in the ore-forming fluids for each sample was estimated by binary mixing modeling on Li-O isotopic data of 53 quartz samples (see Appendix II, Table S1, and Fig. 3). All data from Table S1.

Mentions: In this study we first report Li isotopic compositions of the Gacun Zn-Pb-Cu deposit, a giant volcanogenic massive sulfide deposit in the Yindun arc-basin system1011, southwest China (Fig. 1). Our data suggest that magmatic fluids escaping from a rhyolitic melt play an important role in ore formation. Additionally, we demonstrate that the Li isotopic measurements can be used to monitor the mixing of fluids associated with ore formation and could help to locate the particularly mineralized horizons.


Lithium isotope traces magmatic fluid in a seafloor hydrothermal system.

Yang D, Hou Z, Zhao Y, Hou K, Yang Z, Tian S, Fu Q - Sci Rep (2015)

Geological map of the Gacun deposit (modified from refs. 10,12), showing sample locations and spatial distribution of the major orebodies on a 4100 m exploration plane.The Triassic volcanic-sedimentary strata were folded and steeply-dipped eastwards due to later deformation, providing an ideal cross-section that shows a rhyolitic package and the hosted orebodies from the deep (west) to top (east). Inset map shows tectonic framework of the Yidun Arc, formed by westward subduction of the Ganzi-Litang oceanic lithposhere in Triassic10. The Gacun deposit is located in an intra-arc rifting zone within the Traissic arc, and consists of three major orebodies. The location of U-Pb dating samples and the boundaries of a feeder zone of hydrothermal system10 are also shown. 53 samples for Li analyses were collected along 8 prospecting lines across orebodies at different heights (4050 m, 4100 m, 4150 m) and are shown on an exploration plane at 4100 m. Locations of all samples are marked by solid circles (at 4100 m) and open circles (at 4050 m and 4160 m). The minimal amount of seawater (Xseawater) in the ore-forming fluids for each sample was estimated by binary mixing modeling on Li-O isotopic data of 53 quartz samples (see Appendix II, Table S1, and Fig. 3). All data from Table S1.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4561896&req=5

f1: Geological map of the Gacun deposit (modified from refs. 10,12), showing sample locations and spatial distribution of the major orebodies on a 4100 m exploration plane.The Triassic volcanic-sedimentary strata were folded and steeply-dipped eastwards due to later deformation, providing an ideal cross-section that shows a rhyolitic package and the hosted orebodies from the deep (west) to top (east). Inset map shows tectonic framework of the Yidun Arc, formed by westward subduction of the Ganzi-Litang oceanic lithposhere in Triassic10. The Gacun deposit is located in an intra-arc rifting zone within the Traissic arc, and consists of three major orebodies. The location of U-Pb dating samples and the boundaries of a feeder zone of hydrothermal system10 are also shown. 53 samples for Li analyses were collected along 8 prospecting lines across orebodies at different heights (4050 m, 4100 m, 4150 m) and are shown on an exploration plane at 4100 m. Locations of all samples are marked by solid circles (at 4100 m) and open circles (at 4050 m and 4160 m). The minimal amount of seawater (Xseawater) in the ore-forming fluids for each sample was estimated by binary mixing modeling on Li-O isotopic data of 53 quartz samples (see Appendix II, Table S1, and Fig. 3). All data from Table S1.
Mentions: In this study we first report Li isotopic compositions of the Gacun Zn-Pb-Cu deposit, a giant volcanogenic massive sulfide deposit in the Yindun arc-basin system1011, southwest China (Fig. 1). Our data suggest that magmatic fluids escaping from a rhyolitic melt play an important role in ore formation. Additionally, we demonstrate that the Li isotopic measurements can be used to monitor the mixing of fluids associated with ore formation and could help to locate the particularly mineralized horizons.

Bottom Line: The δ(7)Li results vary from +4.5‰ to +13.8‰ for fluid inclusions and from +6.7‰ to +21.0‰ for the hosted gangue quartz(9 gangue quartz samples containing primary fluid inclusions).This δ(7)Li range, together with Li-O modeling , suggest that magmatic fluid played a significant role in the ore formation.This study demonstrates that Li isotope can be effectively used to trace magmatic fluids in a seafloor hydrothermal system and has the potential to monitor fluid mixing and ore-forming process.

View Article: PubMed Central - PubMed

Affiliation: Institute of Mineral Resources, CAGS, Beijing 100037, P. R. China.

ABSTRACT
Lithium isotopic compositions of fluid inclusions and hosted gangue quartz from a giant volcanogenic massive sulfide deposit in China provide robust evidence for inputting of magmatic fluids into a Triassic submarine hydrothermal system. The δ(7)Li results vary from +4.5‰ to +13.8‰ for fluid inclusions and from +6.7‰ to +21.0‰ for the hosted gangue quartz(9 gangue quartz samples containing primary fluid inclusions). These data confirm the temperature-dependent Li isotopic fractionation between hydrothermal quartz and fluid (i.e., Δδ(7)Liquartz-fluid = -8.9382 × (1000/T) + 22.22(R(2) = 0.98; 175 °C-340 °C)), which suggests that the fluid inclusions are in equilibrium with their hosted quartz, thus allowing to determine the composition of the fluids by using δ(7)Liquartz data. Accordingly, we estimate that the ore-forming fluids have a δ(7)Li range from -0.7‰ to +18.4‰ at temperatures of 175-340 °C. This δ(7)Li range, together with Li-O modeling , suggest that magmatic fluid played a significant role in the ore formation. This study demonstrates that Li isotope can be effectively used to trace magmatic fluids in a seafloor hydrothermal system and has the potential to monitor fluid mixing and ore-forming process.

No MeSH data available.