Formation of orthopyroxene-magnetite symplectites by reactive melt flow: Insights into the Shangzhuang layered intrusion in Beijing, China

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Authors

  • Sijia Wang
  • Tong Hou
  • Qiuhong Xie

Research Organisations

External Research Organisations

  • China University of Geosciences
  • Chinese Academy of Geological Sciences (CAGS)
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Details

Original languageEnglish
Article number106262
Number of pages13
JournalJournal of Asian earth sciences
Volume273
Early online date17 Jul 2024
Publication statusPublished - Sept 2024

Abstract

Interstitial microstructures in layered intrusions can provide crucial insights into the formation, transport, evolution, and solidification processes of magma. The symplectites commonly observed in the Shangzhuang layered intrusions in Beijing, China, can be classified into three types based on their occurrence and related primocryst minerals. Regardless of variation in types, the vermicular symplectites consistently exhibit a volume ratio of magnetite to orthopyroxene at approximately 1:4. Orthopyroxene in the symplectites shows no geochemical difference from those primocrysts. Inter-cumulus hornblende formed during the late stage after the formation of symplectites so that the symplectites are always enclosed by hornblende. By utilizing the hornblende geothermobarometer, we have also constrained that the symplectites have been formed within a relatively wide temperature range of 1040–915 °C through a reaction between the interstitial immiscible Fe-rich melt and the primocryst olivine and orthopyroxene. The reaction can be simplified as Ol/Opx (primocryst) + Fe-rich melt → Opx (symplectite) + Mt (symplectite). Besides, based on the mass balance and reaction results, the Si/O ratio of Fe-rich melt is estimated to be 1:3. The study of these symplectites contributes to refining the processes of reactive melt flow in mafic layered intrusions during late-stage magmatic crystallization.

Keywords

    Fe-rich melt, Interstitial liquid immiscibility, Mafic layered intrusions, Reactive melt flow, Symplectite

ASJC Scopus subject areas

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Formation of orthopyroxene-magnetite symplectites by reactive melt flow: Insights into the Shangzhuang layered intrusion in Beijing, China. / Wang, Sijia; Hou, Tong; Xie, Qiuhong.
In: Journal of Asian earth sciences, Vol. 273, 106262, 09.2024.

Research output: Contribution to journalArticleResearchpeer review

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title = "Formation of orthopyroxene-magnetite symplectites by reactive melt flow: Insights into the Shangzhuang layered intrusion in Beijing, China",
abstract = "Interstitial microstructures in layered intrusions can provide crucial insights into the formation, transport, evolution, and solidification processes of magma. The symplectites commonly observed in the Shangzhuang layered intrusions in Beijing, China, can be classified into three types based on their occurrence and related primocryst minerals. Regardless of variation in types, the vermicular symplectites consistently exhibit a volume ratio of magnetite to orthopyroxene at approximately 1:4. Orthopyroxene in the symplectites shows no geochemical difference from those primocrysts. Inter-cumulus hornblende formed during the late stage after the formation of symplectites so that the symplectites are always enclosed by hornblende. By utilizing the hornblende geothermobarometer, we have also constrained that the symplectites have been formed within a relatively wide temperature range of 1040–915 °C through a reaction between the interstitial immiscible Fe-rich melt and the primocryst olivine and orthopyroxene. The reaction can be simplified as Ol/Opx (primocryst) + Fe-rich melt → Opx (symplectite) + Mt (symplectite). Besides, based on the mass balance and reaction results, the Si/O ratio of Fe-rich melt is estimated to be 1:3. The study of these symplectites contributes to refining the processes of reactive melt flow in mafic layered intrusions during late-stage magmatic crystallization.",
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