Biotit a amfibol z ultradraselných hornin jihlavského plutonu – produkty sekundární hydratace pyroxenu

Jana Suchánková, Jaromír Leichmann, Josef Zeman

Abstrakt

Syenites from the Jihlava pluton contain a broad spectrum of ferromagnesian minerals. Clinopyroxene (Cpx), Orthopyroxene (Opx), Biotite (Bt) Cummingtonite (Cum) and Actinolite (Act). Clino- and orthopyroxenes exhibit structures eg. zoning, admixtures typical for magmatic phases. Cummigtonite is partly product of hypersthene hydration, whereas actinolite originated on the expense of augite. Biotite grows at the contact between hypersthene and K-feldspar via reaction 3 Opx + Kfs = Bt + 3 Qtz. Because of hypersthene contains common admixtures of Cpx and K-feldspar contains myrmekites of andesine composition, therefore small amount of actinolitic hornblende originated during this reaction in addition. Much larger amount of actinolite, together with plagioclase was produced during the reaction between augite and K-feldspar – apart from prevailing biotite and quartz. Observed reactions indicate that the magma was dry and intrudes probably in the lower crust conditions, and was partly hydrated and reequilibrated during subsequent rapid exhumation.

Bibliografická citace

Suchánková, J., Leichmann, J., & Zeman, J. (2016). Biotit a amfibol z ultradraselných hornin jihlavského plutonu – produkty sekundární hydratace pyroxenu. Geologické výzkumy na Moravě a ve Slezsku, 13. Získáno z https://journals.muni.cz/gvms/article/view/4870

Klíčová slova

Jihlava pluton; syenites; ferromagnesian minerals; hydration

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Reference

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