Melt pockets and spongy clinopyroxenes in mantle xenoliths from the plio-Quaternary al ghab volcanic field, NW Syria: implications for the metasomatic evolution of the lithosphere

George S K Ma; Kuo Lung Wang; John Malpas; Yoshiyuki Iizuka; Costas Xenophontos; Abdulsalam A. Turkmani; Gavin H N Chan; Tadashi Usuki; Queenie H S Chan

doi:10.1007/978-3-319-15627-9_7

Melt pockets and spongy clinopyroxenes in mantle xenoliths from the plio-Quaternary al ghab volcanic field, NW Syria: implications for the metasomatic evolution of the lithosphere

George S K Ma^*, Kuo Lung Wang, John Malpas, Yoshiyuki Iizuka, Costas Xenophontos, Abdulsalam A. Turkmani, Gavin H N Chan, Tadashi Usuki, Queenie H S Chan

^*Corresponding author for this work

Research output: Chapter in Book/Report/Conference proceeding › Chapter › peer-review

13 Citations (Scopus)

Abstract

Spongy minerals, especially clinopyroxenes, and fine-grained, often glass-bearing mineral assemblages, commonly referred to as melt pockets, occur in many mantle xenolith suites worldwide, but their origins remain far from being clearly understood. We describe a suite of spongy clinopyroxene- and melt pockets-bearing peridotite xenoliths from the Plio-Quaternary volcanic field in the Al Ghab Depression, a pull-apart basin of the Dead Sea Fault System in northwestern Syria. The melt pockets comprise fine-grained olivines, clinopyroxenes, spinels and feldspars ± amphiboles ± glasses. Petrography and major and trace element mineral chemistry suggest that the xenoliths have experienced at least two stages of metasomatism with the formation of the melt pockets being associated with the latest event. The first metasomatic episode featuring LREE, Na, Th, U enrichment and relative Ti and Zr depletion in the cores of primary clinopyroxenes involved metasomatism by a low-silica, CO₂-rich agent. The second metasomatic episode was associated with the development of melt pockets which evolved from decompressional and perhaps metasomatism-induced incongruent melting of clinopyroxene ± spinel. The spongy clinopyroxenes that occur as coronas around clear, primary clinopyroxenes represent a transitional stage of the partially melted crystals. The incongruent melting produced a liquid that evolved within the melt pockets and eventually migrated out to form amphiboles and micas elsewhere in the lithosphere. Albeit with some uncertainty, geothermobarometric estimations reveal significant, systematic differences in the equilibration pressures between the primary minerals (0.8-1.4 GPa), and spongy and melt-pocket minerals (0.7-0.9 GPa), lending good support for the decompressional origins of the spongy clinopyroxenes and melt pockets. It is interpreted that decompression resulted from local transtension associated with the development of the Al Ghab pull-apart basin, a step-over zone of the Dead Sea Fault System, in Plio-Quaternary time.

Original language	English
Title of host publication	The Earth's heterogeneous mantle
Subtitle of host publication	A geophysical, geodynamical, and geochemical perspective
Editors	Amir Khan, Frédéric Deschamps
Place of Publication	Cham, Switzerland
Publisher	Springer, Springer Nature
Pages	205-257
Number of pages	53
ISBN (Electronic)	9783319156279
ISBN (Print)	9783319156262
DOIs	https://doi.org/10.1007/978-3-319-15627-9_7
Publication status	Published - 1 Jan 2015
Externally published	Yes

Publication series

Name	Springer Geophysics

Keywords

lithospheric mantle
mantle metasomatism
melt pocket
spongy texture
thermobarometry

Access to Document

10.1007/978-3-319-15627-9_7

Cite this

Ma, G. S. K., Wang, K. L., Malpas, J., Iizuka, Y., Xenophontos, C., Turkmani, A. A., Chan, G. H. N., Usuki, T., & Chan, Q. H. S. (2015). Melt pockets and spongy clinopyroxenes in mantle xenoliths from the plio-Quaternary al ghab volcanic field, NW Syria: implications for the metasomatic evolution of the lithosphere. In A. Khan, & F. Deschamps (Eds.), The Earth's heterogeneous mantle: A geophysical, geodynamical, and geochemical perspective (pp. 205-257). (Springer Geophysics). Springer, Springer Nature. https://doi.org/10.1007/978-3-319-15627-9_7

Ma, George S K ; Wang, Kuo Lung ; Malpas, John et al. / Melt pockets and spongy clinopyroxenes in mantle xenoliths from the plio-Quaternary al ghab volcanic field, NW Syria : implications for the metasomatic evolution of the lithosphere. The Earth's heterogeneous mantle: A geophysical, geodynamical, and geochemical perspective. editor / Amir Khan ; Frédéric Deschamps. Cham, Switzerland : Springer, Springer Nature, 2015. pp. 205-257 (Springer Geophysics).

@inbook{3257311c8564476994fc5a3ba7c14f6b,

title = "Melt pockets and spongy clinopyroxenes in mantle xenoliths from the plio-Quaternary al ghab volcanic field, NW Syria: implications for the metasomatic evolution of the lithosphere",

abstract = "Spongy minerals, especially clinopyroxenes, and fine-grained, often glass-bearing mineral assemblages, commonly referred to as melt pockets, occur in many mantle xenolith suites worldwide, but their origins remain far from being clearly understood. We describe a suite of spongy clinopyroxene- and melt pockets-bearing peridotite xenoliths from the Plio-Quaternary volcanic field in the Al Ghab Depression, a pull-apart basin of the Dead Sea Fault System in northwestern Syria. The melt pockets comprise fine-grained olivines, clinopyroxenes, spinels and feldspars ± amphiboles ± glasses. Petrography and major and trace element mineral chemistry suggest that the xenoliths have experienced at least two stages of metasomatism with the formation of the melt pockets being associated with the latest event. The first metasomatic episode featuring LREE, Na, Th, U enrichment and relative Ti and Zr depletion in the cores of primary clinopyroxenes involved metasomatism by a low-silica, CO2-rich agent. The second metasomatic episode was associated with the development of melt pockets which evolved from decompressional and perhaps metasomatism-induced incongruent melting of clinopyroxene ± spinel. The spongy clinopyroxenes that occur as coronas around clear, primary clinopyroxenes represent a transitional stage of the partially melted crystals. The incongruent melting produced a liquid that evolved within the melt pockets and eventually migrated out to form amphiboles and micas elsewhere in the lithosphere. Albeit with some uncertainty, geothermobarometric estimations reveal significant, systematic differences in the equilibration pressures between the primary minerals (0.8-1.4 GPa), and spongy and melt-pocket minerals (0.7-0.9 GPa), lending good support for the decompressional origins of the spongy clinopyroxenes and melt pockets. It is interpreted that decompression resulted from local transtension associated with the development of the Al Ghab pull-apart basin, a step-over zone of the Dead Sea Fault System, in Plio-Quaternary time.",

keywords = "lithospheric mantle, mantle metasomatism, melt pocket, spongy texture, thermobarometry",

author = "Ma, {George S K} and Wang, {Kuo Lung} and John Malpas and Yoshiyuki Iizuka and Costas Xenophontos and Turkmani, {Abdulsalam A.} and Chan, {Gavin H N} and Tadashi Usuki and Chan, {Queenie H S}",

year = "2015",

month = jan,

day = "1",

doi = "10.1007/978-3-319-15627-9_7",

language = "English",

isbn = "9783319156262",

series = "Springer Geophysics",

publisher = "Springer, Springer Nature",

pages = "205--257",

editor = "Amir Khan and Fr{\'e}d{\'e}ric Deschamps",

booktitle = "The Earth's heterogeneous mantle",

address = "United States",

}

Ma, GSK, Wang, KL, Malpas, J, Iizuka, Y, Xenophontos, C, Turkmani, AA, Chan, GHN, Usuki, T & Chan, QHS 2015, Melt pockets and spongy clinopyroxenes in mantle xenoliths from the plio-Quaternary al ghab volcanic field, NW Syria: implications for the metasomatic evolution of the lithosphere. in A Khan & F Deschamps (eds), The Earth's heterogeneous mantle: A geophysical, geodynamical, and geochemical perspective. Springer Geophysics, Springer, Springer Nature, Cham, Switzerland, pp. 205-257. https://doi.org/10.1007/978-3-319-15627-9_7

Melt pockets and spongy clinopyroxenes in mantle xenoliths from the plio-Quaternary al ghab volcanic field, NW Syria: implications for the metasomatic evolution of the lithosphere. / Ma, George S K; Wang, Kuo Lung; Malpas, John et al.
The Earth's heterogeneous mantle: A geophysical, geodynamical, and geochemical perspective. ed. / Amir Khan; Frédéric Deschamps. Cham, Switzerland: Springer, Springer Nature, 2015. p. 205-257 (Springer Geophysics).

Research output: Chapter in Book/Report/Conference proceeding › Chapter › peer-review

TY - CHAP

T1 - Melt pockets and spongy clinopyroxenes in mantle xenoliths from the plio-Quaternary al ghab volcanic field, NW Syria

T2 - implications for the metasomatic evolution of the lithosphere

AU - Ma, George S K

AU - Wang, Kuo Lung

AU - Malpas, John

AU - Iizuka, Yoshiyuki

AU - Xenophontos, Costas

AU - Turkmani, Abdulsalam A.

AU - Chan, Gavin H N

AU - Usuki, Tadashi

AU - Chan, Queenie H S

PY - 2015/1/1

Y1 - 2015/1/1

N2 - Spongy minerals, especially clinopyroxenes, and fine-grained, often glass-bearing mineral assemblages, commonly referred to as melt pockets, occur in many mantle xenolith suites worldwide, but their origins remain far from being clearly understood. We describe a suite of spongy clinopyroxene- and melt pockets-bearing peridotite xenoliths from the Plio-Quaternary volcanic field in the Al Ghab Depression, a pull-apart basin of the Dead Sea Fault System in northwestern Syria. The melt pockets comprise fine-grained olivines, clinopyroxenes, spinels and feldspars ± amphiboles ± glasses. Petrography and major and trace element mineral chemistry suggest that the xenoliths have experienced at least two stages of metasomatism with the formation of the melt pockets being associated with the latest event. The first metasomatic episode featuring LREE, Na, Th, U enrichment and relative Ti and Zr depletion in the cores of primary clinopyroxenes involved metasomatism by a low-silica, CO2-rich agent. The second metasomatic episode was associated with the development of melt pockets which evolved from decompressional and perhaps metasomatism-induced incongruent melting of clinopyroxene ± spinel. The spongy clinopyroxenes that occur as coronas around clear, primary clinopyroxenes represent a transitional stage of the partially melted crystals. The incongruent melting produced a liquid that evolved within the melt pockets and eventually migrated out to form amphiboles and micas elsewhere in the lithosphere. Albeit with some uncertainty, geothermobarometric estimations reveal significant, systematic differences in the equilibration pressures between the primary minerals (0.8-1.4 GPa), and spongy and melt-pocket minerals (0.7-0.9 GPa), lending good support for the decompressional origins of the spongy clinopyroxenes and melt pockets. It is interpreted that decompression resulted from local transtension associated with the development of the Al Ghab pull-apart basin, a step-over zone of the Dead Sea Fault System, in Plio-Quaternary time.

AB - Spongy minerals, especially clinopyroxenes, and fine-grained, often glass-bearing mineral assemblages, commonly referred to as melt pockets, occur in many mantle xenolith suites worldwide, but their origins remain far from being clearly understood. We describe a suite of spongy clinopyroxene- and melt pockets-bearing peridotite xenoliths from the Plio-Quaternary volcanic field in the Al Ghab Depression, a pull-apart basin of the Dead Sea Fault System in northwestern Syria. The melt pockets comprise fine-grained olivines, clinopyroxenes, spinels and feldspars ± amphiboles ± glasses. Petrography and major and trace element mineral chemistry suggest that the xenoliths have experienced at least two stages of metasomatism with the formation of the melt pockets being associated with the latest event. The first metasomatic episode featuring LREE, Na, Th, U enrichment and relative Ti and Zr depletion in the cores of primary clinopyroxenes involved metasomatism by a low-silica, CO2-rich agent. The second metasomatic episode was associated with the development of melt pockets which evolved from decompressional and perhaps metasomatism-induced incongruent melting of clinopyroxene ± spinel. The spongy clinopyroxenes that occur as coronas around clear, primary clinopyroxenes represent a transitional stage of the partially melted crystals. The incongruent melting produced a liquid that evolved within the melt pockets and eventually migrated out to form amphiboles and micas elsewhere in the lithosphere. Albeit with some uncertainty, geothermobarometric estimations reveal significant, systematic differences in the equilibration pressures between the primary minerals (0.8-1.4 GPa), and spongy and melt-pocket minerals (0.7-0.9 GPa), lending good support for the decompressional origins of the spongy clinopyroxenes and melt pockets. It is interpreted that decompression resulted from local transtension associated with the development of the Al Ghab pull-apart basin, a step-over zone of the Dead Sea Fault System, in Plio-Quaternary time.

KW - lithospheric mantle

KW - mantle metasomatism

KW - melt pocket

KW - spongy texture

KW - thermobarometry

UR - http://www.scopus.com/inward/record.url?scp=84943805533&partnerID=8YFLogxK

U2 - 10.1007/978-3-319-15627-9_7

DO - 10.1007/978-3-319-15627-9_7

M3 - Chapter

AN - SCOPUS:84943805533

SN - 9783319156262

T3 - Springer Geophysics

SP - 205

EP - 257

BT - The Earth's heterogeneous mantle

A2 - Khan, Amir

A2 - Deschamps, Frédéric

PB - Springer, Springer Nature

CY - Cham, Switzerland

ER -

Ma GSK, Wang KL, Malpas J, Iizuka Y, Xenophontos C, Turkmani AA et al. Melt pockets and spongy clinopyroxenes in mantle xenoliths from the plio-Quaternary al ghab volcanic field, NW Syria: implications for the metasomatic evolution of the lithosphere. In Khan A, Deschamps F, editors, The Earth's heterogeneous mantle: A geophysical, geodynamical, and geochemical perspective. Cham, Switzerland: Springer, Springer Nature. 2015. p. 205-257. (Springer Geophysics). doi: 10.1007/978-3-319-15627-9_7

Melt pockets and spongy clinopyroxenes in mantle xenoliths from the plio-Quaternary al ghab volcanic field, NW Syria: implications for the metasomatic evolution of the lithosphere

Abstract

Publication series

Keywords

Access to Document

Other files and links

Fingerprint

Cite this