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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.


Two-dimentional compositional variation of a Triassic submarine hydrothermal system on a geological cross-section at Gacun.The map shows that the initial fluid dominated by magmatic vapors escaping from a rhyolitic dome discharged upwards via a sub-vertical feeder zone and drived the convective circulation of seawater-dominated fluids through volcanic units. The contours with tick of seawater quantitative proportion (number) for each mineralized zone were outlined, based on all point data on Xseawater for each sample in Fig. 1.
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f4: Two-dimentional compositional variation of a Triassic submarine hydrothermal system on a geological cross-section at Gacun.The map shows that the initial fluid dominated by magmatic vapors escaping from a rhyolitic dome discharged upwards via a sub-vertical feeder zone and drived the convective circulation of seawater-dominated fluids through volcanic units. The contours with tick of seawater quantitative proportion (number) for each mineralized zone were outlined, based on all point data on Xseawater for each sample in Fig. 1.

Mentions: Spatial variation in the minimum percentages of seawater (Xseawater) in the ore-forming fluid system shows the outline of a Triassic submarine hydrothermal system at Gacun (Figs 1 and 4), in which the convective circulation of fluids through ~233 Ma volcanic units was driven by a rhyolitic dome emplaced at ~221 Ma. The initial fluid is dominated by magmatic water, escaping from the rhyolitic dome, which firstly formed the LSO and subsequently mixed with seawater circulating through the hot rocks and discharged upward via a sub-vertical feeder zone (Fig. 4). Lateral migration of seawater mixed with magmatic fluid along permeable layers within the rhyolitic package formed the MSO orebodies (Fig. 4). The episodically inputting of fluids dominated by seawater into a seafloor brine pool within a submarine basin10 led to the formation of the UMO1011.


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)

Two-dimentional compositional variation of a Triassic submarine hydrothermal system on a geological cross-section at Gacun.The map shows that the initial fluid dominated by magmatic vapors escaping from a rhyolitic dome discharged upwards via a sub-vertical feeder zone and drived the convective circulation of seawater-dominated fluids through volcanic units. The contours with tick of seawater quantitative proportion (number) for each mineralized zone were outlined, based on all point data on Xseawater for each sample in Fig. 1.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

f4: Two-dimentional compositional variation of a Triassic submarine hydrothermal system on a geological cross-section at Gacun.The map shows that the initial fluid dominated by magmatic vapors escaping from a rhyolitic dome discharged upwards via a sub-vertical feeder zone and drived the convective circulation of seawater-dominated fluids through volcanic units. The contours with tick of seawater quantitative proportion (number) for each mineralized zone were outlined, based on all point data on Xseawater for each sample in Fig. 1.
Mentions: Spatial variation in the minimum percentages of seawater (Xseawater) in the ore-forming fluid system shows the outline of a Triassic submarine hydrothermal system at Gacun (Figs 1 and 4), in which the convective circulation of fluids through ~233 Ma volcanic units was driven by a rhyolitic dome emplaced at ~221 Ma. The initial fluid is dominated by magmatic water, escaping from the rhyolitic dome, which firstly formed the LSO and subsequently mixed with seawater circulating through the hot rocks and discharged upward via a sub-vertical feeder zone (Fig. 4). Lateral migration of seawater mixed with magmatic fluid along permeable layers within the rhyolitic package formed the MSO orebodies (Fig. 4). The episodically inputting of fluids dominated by seawater into a seafloor brine pool within a submarine basin10 led to the formation of the UMO1011.

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.