Publication details
Zajímavá mafická žíla ze štoly Holedná – Bosonohy (brněnský masiv): přechodný petrografický typ mezi typickými mikrodiority a lamprofyry
| Title in English | Interesting mafic dyke from the mine adit Holedná – Bosonohy (the Brno Massif): transitional petrographic type between microdiorites and lamprophyres |
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| Authors | |
| Year of publication | 2011 |
| Type | Article in Periodical |
| Magazine / Source | Zprávy o geologických výzkumech v roce 2011 |
| MU Faculty or unit | |
| Citation | |
| Field | Geology and mineralogy |
| Keywords | poikilitic spessartite;mineral composition;magnesiumhastingsite;Brno Batholith; Moravo-Silesian Region |
| Description | The Brno Massif is crosscut by numerous mafic post-collisional calc-alkaline dykes of supposed Variscan age. From the petrographic point of view, the microdiorite dykes strongly prevail against the less abundant lamprophyres. In this article, we describe a new finding of a spessartite dyke which represents a transitional petrographic type between the archetypal microdiorites and amphibole lamprophyres. The dyke is characterised by abundant phenocrysts of anhydrous mafic minerals (clinopyroxene, pseudomorphosed olivine). On the other hand, the dyke also contains euhedral to subhedral matrix amphiboles (mainly magnesiohastingsite) poikilitically enclosed by the larger plagioclase aggregates. Presence of matrix amphiboles suggests the increase in water activity of the parental melt. This may have occurred (based on our barometric estimations) within the deep crustal H2O-rich zone between the Conrad and Moho discontinuities. |
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