Význam magnetické susceptibility pro geologické mapování hornin těšínitové asociace na listu 1 : 25 000 Starý Jičín (25-124)
Roč.14,(2007)
New results of geophysical investigations of the Early Cretaceous rocks teschenite association in the area around town Starý Jičín (western part of the Carpathians) provide evidence for subdivision these rocks on two groups. The teschenites contains primary magnetite (high magnetic susceptibility, 3–82×10-3 SI), although were strongly affected by hydrothermal fluids. On the other hand, alterated picrite to basalt (picrite, monchiquite, fourchite and basalt) are characterised by low magnetic susceptibility (0.06–16×10-3 SI) and ferromagnesian minerals are very rare. These two rock groups are subdivided according to proportion between main rocks forming minerals (mafic and felsic minerals). The magnetic susceptibility reflected variation in chemical composition [FeO/(FeO+MgO)] and different kind of alteration between teschenite and magnesium rich rocks (picrite to basalt). In the magnesium rich rocks transformation primary magmatic assemblage to the secondary minerals (chlorite, limonite), lead to distinct decline magnetic susceptibility.
petrology; teschenite association; magnetic susceptibility; hydrothermal alteration
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