Ultrahigh-pressure metabasaltic garnets as probes into deep subduction zone chemical cycling

Robert L. King, Gray Edward Bebout, Katsura Kobayashi, Eizou Nakamura, Sebastiaan N G C Van Der Klauw

Research output: Contribution to journalArticle

39 Citations (Scopus)

Abstract

We demonstrate an approach to examining the metamorphic history of subducting oceanic crust that can complement records of subduction zone chemical cycling derived from studies of igneous rocks produced at volcanic arcs. By merging methods utilizing garnet zoning to establish prograde reaction histories with in situ high-resolution trace element geochemistry, and application to coesite-bearing mafic eclogites representing subduction to depths beneath arcs, we are able to directly identify geochemical manifestations of reactions contributing to element mobility in the subducting slab that are only inferred in studies of volcanic arcs or theoretical metamorphic models. Specifically, we identify a prograde metamorphic reaction, based solely on the zoning of geochemistry and mineral inclusions within garnet, and infer that these features are a record of the breakdown of coexisting clinozoisite + titanite and probable liberation of trace element-laden fluid from the rock during prograde metamorphism. We are then able to assign a specific depth interval for the reaction through calculation of the P-T dependence of the reaction for these eclogites and comparison with a published P-T trajectory. Because of the robust preservation of records of petrologic and geochemical processes by garnet, this methodology is particularly suited for study of ultrahigh-pressure (UHP) eclogites, in which severe retrograde alteration (generally related to exhumation) commonly obscures prograde history.

Original languageEnglish
Article numberQ12J14
JournalGeochemistry, Geophysics, Geosystems
Volume5
Issue number12
DOIs
Publication statusPublished - Dec 2004

Fingerprint

Garnets
garnets
subduction zone
garnet
Zoning
Geochemistry
probe
Trace Elements
cycles
zoning
island arc
probes
Bearings (structural)
history
geochemistry
trace element
Igneous rocks
arcs
clinozoisite
element mobility

Keywords

  • Garnet zoning
  • Geothermobarometry
  • Lithium
  • Rare earth elements
  • Subduction zones
  • Ultrahigh-pressure metamorphism

ASJC Scopus subject areas

  • Geochemistry and Petrology
  • Geophysics

Cite this

Ultrahigh-pressure metabasaltic garnets as probes into deep subduction zone chemical cycling. / King, Robert L.; Edward Bebout, Gray; Kobayashi, Katsura; Nakamura, Eizou; Van Der Klauw, Sebastiaan N G C.

In: Geochemistry, Geophysics, Geosystems, Vol. 5, No. 12, Q12J14, 12.2004.

Research output: Contribution to journalArticle

@article{07b4e1cc83d14ba481001440449ab6ff,
title = "Ultrahigh-pressure metabasaltic garnets as probes into deep subduction zone chemical cycling",
abstract = "We demonstrate an approach to examining the metamorphic history of subducting oceanic crust that can complement records of subduction zone chemical cycling derived from studies of igneous rocks produced at volcanic arcs. By merging methods utilizing garnet zoning to establish prograde reaction histories with in situ high-resolution trace element geochemistry, and application to coesite-bearing mafic eclogites representing subduction to depths beneath arcs, we are able to directly identify geochemical manifestations of reactions contributing to element mobility in the subducting slab that are only inferred in studies of volcanic arcs or theoretical metamorphic models. Specifically, we identify a prograde metamorphic reaction, based solely on the zoning of geochemistry and mineral inclusions within garnet, and infer that these features are a record of the breakdown of coexisting clinozoisite + titanite and probable liberation of trace element-laden fluid from the rock during prograde metamorphism. We are then able to assign a specific depth interval for the reaction through calculation of the P-T dependence of the reaction for these eclogites and comparison with a published P-T trajectory. Because of the robust preservation of records of petrologic and geochemical processes by garnet, this methodology is particularly suited for study of ultrahigh-pressure (UHP) eclogites, in which severe retrograde alteration (generally related to exhumation) commonly obscures prograde history.",
keywords = "Garnet zoning, Geothermobarometry, Lithium, Rare earth elements, Subduction zones, Ultrahigh-pressure metamorphism",
author = "King, {Robert L.} and {Edward Bebout}, Gray and Katsura Kobayashi and Eizou Nakamura and {Van Der Klauw}, {Sebastiaan N G C}",
year = "2004",
month = "12",
doi = "10.1029/2004GC000746",
language = "English",
volume = "5",
journal = "Geochemistry, Geophysics, Geosystems",
issn = "1525-2027",
publisher = "American Geophysical Union",
number = "12",

}

TY - JOUR

T1 - Ultrahigh-pressure metabasaltic garnets as probes into deep subduction zone chemical cycling

AU - King, Robert L.

AU - Edward Bebout, Gray

AU - Kobayashi, Katsura

AU - Nakamura, Eizou

AU - Van Der Klauw, Sebastiaan N G C

PY - 2004/12

Y1 - 2004/12

N2 - We demonstrate an approach to examining the metamorphic history of subducting oceanic crust that can complement records of subduction zone chemical cycling derived from studies of igneous rocks produced at volcanic arcs. By merging methods utilizing garnet zoning to establish prograde reaction histories with in situ high-resolution trace element geochemistry, and application to coesite-bearing mafic eclogites representing subduction to depths beneath arcs, we are able to directly identify geochemical manifestations of reactions contributing to element mobility in the subducting slab that are only inferred in studies of volcanic arcs or theoretical metamorphic models. Specifically, we identify a prograde metamorphic reaction, based solely on the zoning of geochemistry and mineral inclusions within garnet, and infer that these features are a record of the breakdown of coexisting clinozoisite + titanite and probable liberation of trace element-laden fluid from the rock during prograde metamorphism. We are then able to assign a specific depth interval for the reaction through calculation of the P-T dependence of the reaction for these eclogites and comparison with a published P-T trajectory. Because of the robust preservation of records of petrologic and geochemical processes by garnet, this methodology is particularly suited for study of ultrahigh-pressure (UHP) eclogites, in which severe retrograde alteration (generally related to exhumation) commonly obscures prograde history.

AB - We demonstrate an approach to examining the metamorphic history of subducting oceanic crust that can complement records of subduction zone chemical cycling derived from studies of igneous rocks produced at volcanic arcs. By merging methods utilizing garnet zoning to establish prograde reaction histories with in situ high-resolution trace element geochemistry, and application to coesite-bearing mafic eclogites representing subduction to depths beneath arcs, we are able to directly identify geochemical manifestations of reactions contributing to element mobility in the subducting slab that are only inferred in studies of volcanic arcs or theoretical metamorphic models. Specifically, we identify a prograde metamorphic reaction, based solely on the zoning of geochemistry and mineral inclusions within garnet, and infer that these features are a record of the breakdown of coexisting clinozoisite + titanite and probable liberation of trace element-laden fluid from the rock during prograde metamorphism. We are then able to assign a specific depth interval for the reaction through calculation of the P-T dependence of the reaction for these eclogites and comparison with a published P-T trajectory. Because of the robust preservation of records of petrologic and geochemical processes by garnet, this methodology is particularly suited for study of ultrahigh-pressure (UHP) eclogites, in which severe retrograde alteration (generally related to exhumation) commonly obscures prograde history.

KW - Garnet zoning

KW - Geothermobarometry

KW - Lithium

KW - Rare earth elements

KW - Subduction zones

KW - Ultrahigh-pressure metamorphism

UR - http://www.scopus.com/inward/record.url?scp=34147185321&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=34147185321&partnerID=8YFLogxK

U2 - 10.1029/2004GC000746

DO - 10.1029/2004GC000746

M3 - Article

AN - SCOPUS:34147185321

VL - 5

JO - Geochemistry, Geophysics, Geosystems

JF - Geochemistry, Geophysics, Geosystems

SN - 1525-2027

IS - 12

M1 - Q12J14

ER -