Teagle, D. A. H. et al. (1998): Tracing the evolution of hydrothermal fluids in the upper oceanic crust; Sr-isotopic constraints form DSDP/ODP Holes 504B and 896A
Leg/Site/Hole:
Related Expeditions:
ODP 111
Identifier:
ID:
1999-034042
Type:
georefid
Creator:
Name:
Teagle, D. A. H.
Affiliation:
University of Michigan, Department of Geological Sciences, Ann Arbor, MI, United States
Role:
author
Name:
Alt, J. C.
Affiliation:
University of Leeds, United Kingdom
Role:
author
Name:
Halliday, A. N.
Affiliation:
Role:
author
Identification:
Title:
Tracing the evolution of hydrothermal fluids in the upper oceanic crust; Sr-isotopic constraints form DSDP/ODP Holes 504B and 896A
Year:
1998
Source:
In: Mills, R. A. (editor), Harrison, K. (editor), Modern ocean floor processes and the geological record
Publisher:
Geological Society of London, London, United Kingdom
Volume:
148
Issue:
Pages:
81-97
Abstract:
Whole rock and secondary mineral (super 87) Sr/ (super 86) Sr determinations from ODP Holes 504B and 896A have been compiled into a profile for the upper 2 km of in situ ocean crust to constrain the composition and evolution of recharge and discharge fluids. There is a gradual trend from elevated (super 87) Sr/ (super 86) Sr whole rock ratios at the top of the crust towards primary MORB compositions at the base of the sheeted dykes. Rocks from the mineralized lava-dyke transition zone have (super 87) Sr/ (super 86) Sr ratios clustering in the range of black smoker fluids. Igneous and alteration phases are not in Sr-isotopic equilibrium, therefore whole rock strontium isotopic ratios reflect the proportion of secondary minerals and the extent of plagioclase recrystallization. The (super 87) Sr/ (super 86) Sr of anhydrite directly records the chemical evolution of seawater during recharge. There is a slight decrease in anhydrite (super 87) Sr/ (super 86) Sr with depth in the volcanic rocks but anhydrite from the lowermost dykes yields diabasic (super 87) Sr/ (super 86) Sr ratios. Epidotes in cross-cutting veins have higher (super 87) Sr/ (super 86) Sr than the background alteration recorded by amphibole in the lower dykes. This elevated signature reflects the (super 87) Sr/ (super 86) Sr of 504B black smoker-type fluids and requires less fluid evolution than the background alteration, suggesting channelling of recharge fluids locally.
Language:
English
Genre:
Serial
Rights:
URL:
Coverage: Geographic coordinates: North:2.0000 West:-85.0000 East:
-83.0000 South:0.0000
Keywords: Isotope geochemistry; Solid-earth geophysics; alkaline earth metals; alteration; basalts; black smokers; Cenozoic; crust; Deep Sea Drilling Project; dikes; discharge; DSDP Site 504; Equatorial Pacific; geochemistry; hydrothermal vents; igneous rocks; intrusions; IPOD; isotope ratios; isotopes; Leg 111; Leg 137; Leg 140; Leg 148; Leg 69; Leg 70; Leg 83; Leg 92; metals; mid-ocean ridge basalts; Miocene; Neogene; Ocean Drilling Program; oceanic crust; ODP Site 896; Pacific Ocean; recharge; sea water; sheeted dikes; Sr-87/Sr-86; stable isotopes; strontium; Tertiary; upper crust; volcanic rocks; whole rock;
.