Low-pressure and low-temperature K-bearing kosmochloric diopside from the Osayama serpentinite mélange, SW Japan

Tatsuki Tsujimori, Juhn G. Liou

Research output: Contribution to journalArticle

8 Citations (Scopus)

Abstract

Kosmochloric diopside with high K content up to 0.56 wt% (0.026 K atom per formula unit) was discovered from the Osayama serpentinite mélange in the Chugoku Mountains, SW Japan. K-bearing clinopyroxene fills microcracks (5-150 μm in wide) together with uvarovite within albite vein of a tremolite rock. Compositions of analyzed clinopyroxene consist mainly of kosmochlor + augite (92-98 mo1%; Ko19-38Aug56-76) components and minor amounts of jadeite (0-6 mol%), aegirine (0-5 mol%), Ca-Tschermak (0-3 mol%), and K-kosmochlor (0-2 mol%). Although the K content in clinopyroxene is also variable and heterogeneous even in a single vein, clinopyroxene with higher K content occurs in Ko-rich part. Higher magnification secondary electron images confirmed that exsolution and inclusion are essentially absent in the analyzed clinopyroxenes. The good negative correlation between Cr + Na + K and Ca + Mg + Fe2+ indicates the Cr incorporation into the octahedral site. Furthermore, K correlates with Na and Cr, indicating a simultaneous enrichment of K for Na and Cr during pyroxene growth. Textual relations, and parageneses and compositions of minerals suggest that the K-Cpx precipitated together with uvarovite in brittle microcracks directly from a Ca- and Cr-rich hydrothermal fluid at approximately P <0.3 GPa and T <400 °C. Although it has been experimentally concluded that only ultrahigh-P (>4 GPa) environment permits to host relatively large K+ cation into the clinopyroxene structure, our finding indicates that the incorporation of K into the kosmochlor-diopside series solid solution with at least 0.2 Cr cation p.f.u. is possible even at low P conditions.

Original languageEnglish
Pages (from-to)1629-1635
Number of pages7
JournalAmerican Mineralogist
Volume90
Issue number10
DOIs
Publication statusPublished - Oct 2005
Externally publishedYes

Fingerprint

Bearings (structural)
serpentinite
Microcracks
diopside
clinopyroxene
Cations
low pressure
Japan
microcracks
veins
Chemical analysis
microcrack
Minerals
cations
Solid solutions
Rocks
magnification
mountains
Atoms
Temperature

ASJC Scopus subject areas

  • Geochemistry and Petrology
  • Geophysics

Cite this

Low-pressure and low-temperature K-bearing kosmochloric diopside from the Osayama serpentinite mélange, SW Japan. / Tsujimori, Tatsuki; Liou, Juhn G.

In: American Mineralogist, Vol. 90, No. 10, 10.2005, p. 1629-1635.

Research output: Contribution to journalArticle

@article{4ac401273acb4a74903084a879939c96,
title = "Low-pressure and low-temperature K-bearing kosmochloric diopside from the Osayama serpentinite m{\'e}lange, SW Japan",
abstract = "Kosmochloric diopside with high K content up to 0.56 wt{\%} (0.026 K atom per formula unit) was discovered from the Osayama serpentinite m{\'e}lange in the Chugoku Mountains, SW Japan. K-bearing clinopyroxene fills microcracks (5-150 μm in wide) together with uvarovite within albite vein of a tremolite rock. Compositions of analyzed clinopyroxene consist mainly of kosmochlor + augite (92-98 mo1{\%}; Ko19-38Aug56-76) components and minor amounts of jadeite (0-6 mol{\%}), aegirine (0-5 mol{\%}), Ca-Tschermak (0-3 mol{\%}), and K-kosmochlor (0-2 mol{\%}). Although the K content in clinopyroxene is also variable and heterogeneous even in a single vein, clinopyroxene with higher K content occurs in Ko-rich part. Higher magnification secondary electron images confirmed that exsolution and inclusion are essentially absent in the analyzed clinopyroxenes. The good negative correlation between Cr + Na + K and Ca + Mg + Fe2+ indicates the Cr incorporation into the octahedral site. Furthermore, K correlates with Na and Cr, indicating a simultaneous enrichment of K for Na and Cr during pyroxene growth. Textual relations, and parageneses and compositions of minerals suggest that the K-Cpx precipitated together with uvarovite in brittle microcracks directly from a Ca- and Cr-rich hydrothermal fluid at approximately P <0.3 GPa and T <400 °C. Although it has been experimentally concluded that only ultrahigh-P (>4 GPa) environment permits to host relatively large K+ cation into the clinopyroxene structure, our finding indicates that the incorporation of K into the kosmochlor-diopside series solid solution with at least 0.2 Cr cation p.f.u. is possible even at low P conditions.",
author = "Tatsuki Tsujimori and Liou, {Juhn G.}",
year = "2005",
month = "10",
doi = "10.2138/am.2005.1749",
language = "English",
volume = "90",
pages = "1629--1635",
journal = "American Mineralogist",
issn = "0003-004X",
publisher = "Mineralogical Society of America",
number = "10",

}

TY - JOUR

T1 - Low-pressure and low-temperature K-bearing kosmochloric diopside from the Osayama serpentinite mélange, SW Japan

AU - Tsujimori, Tatsuki

AU - Liou, Juhn G.

PY - 2005/10

Y1 - 2005/10

N2 - Kosmochloric diopside with high K content up to 0.56 wt% (0.026 K atom per formula unit) was discovered from the Osayama serpentinite mélange in the Chugoku Mountains, SW Japan. K-bearing clinopyroxene fills microcracks (5-150 μm in wide) together with uvarovite within albite vein of a tremolite rock. Compositions of analyzed clinopyroxene consist mainly of kosmochlor + augite (92-98 mo1%; Ko19-38Aug56-76) components and minor amounts of jadeite (0-6 mol%), aegirine (0-5 mol%), Ca-Tschermak (0-3 mol%), and K-kosmochlor (0-2 mol%). Although the K content in clinopyroxene is also variable and heterogeneous even in a single vein, clinopyroxene with higher K content occurs in Ko-rich part. Higher magnification secondary electron images confirmed that exsolution and inclusion are essentially absent in the analyzed clinopyroxenes. The good negative correlation between Cr + Na + K and Ca + Mg + Fe2+ indicates the Cr incorporation into the octahedral site. Furthermore, K correlates with Na and Cr, indicating a simultaneous enrichment of K for Na and Cr during pyroxene growth. Textual relations, and parageneses and compositions of minerals suggest that the K-Cpx precipitated together with uvarovite in brittle microcracks directly from a Ca- and Cr-rich hydrothermal fluid at approximately P <0.3 GPa and T <400 °C. Although it has been experimentally concluded that only ultrahigh-P (>4 GPa) environment permits to host relatively large K+ cation into the clinopyroxene structure, our finding indicates that the incorporation of K into the kosmochlor-diopside series solid solution with at least 0.2 Cr cation p.f.u. is possible even at low P conditions.

AB - Kosmochloric diopside with high K content up to 0.56 wt% (0.026 K atom per formula unit) was discovered from the Osayama serpentinite mélange in the Chugoku Mountains, SW Japan. K-bearing clinopyroxene fills microcracks (5-150 μm in wide) together with uvarovite within albite vein of a tremolite rock. Compositions of analyzed clinopyroxene consist mainly of kosmochlor + augite (92-98 mo1%; Ko19-38Aug56-76) components and minor amounts of jadeite (0-6 mol%), aegirine (0-5 mol%), Ca-Tschermak (0-3 mol%), and K-kosmochlor (0-2 mol%). Although the K content in clinopyroxene is also variable and heterogeneous even in a single vein, clinopyroxene with higher K content occurs in Ko-rich part. Higher magnification secondary electron images confirmed that exsolution and inclusion are essentially absent in the analyzed clinopyroxenes. The good negative correlation between Cr + Na + K and Ca + Mg + Fe2+ indicates the Cr incorporation into the octahedral site. Furthermore, K correlates with Na and Cr, indicating a simultaneous enrichment of K for Na and Cr during pyroxene growth. Textual relations, and parageneses and compositions of minerals suggest that the K-Cpx precipitated together with uvarovite in brittle microcracks directly from a Ca- and Cr-rich hydrothermal fluid at approximately P <0.3 GPa and T <400 °C. Although it has been experimentally concluded that only ultrahigh-P (>4 GPa) environment permits to host relatively large K+ cation into the clinopyroxene structure, our finding indicates that the incorporation of K into the kosmochlor-diopside series solid solution with at least 0.2 Cr cation p.f.u. is possible even at low P conditions.

UR - http://www.scopus.com/inward/record.url?scp=26944501062&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=26944501062&partnerID=8YFLogxK

U2 - 10.2138/am.2005.1749

DO - 10.2138/am.2005.1749

M3 - Article

VL - 90

SP - 1629

EP - 1635

JO - American Mineralogist

JF - American Mineralogist

SN - 0003-004X

IS - 10

ER -