Uralitization – An example from Kuusamo, Finland
The course of events as well as the chemical changes associated with the alteration of clinopyroxenes to uralite have been studied from diabases in Kuusamo, Finland. The uralitization takes place in several phases starting from the intercumulus spaces, where late-magmatic fluids cause an increase in...
| Main Authors: | , |
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| Format: | Article |
| Language: | English |
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Geological Society of Finland
1977-06-01
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| Series: | Bulletin of the Geological Society of Finland |
| Online Access: | http://www.geologinenseura.fi/bulletin/Volume49/sgs_bt_049_1_pages_039_046.pdf |
| Summary: | The course of events as well as the chemical changes associated with the alteration of clinopyroxenes to uralite have been studied from diabases in Kuusamo, Finland. The uralitization takes place in several phases starting from the intercumulus spaces, where late-magmatic fluids cause an increase in iron and titanium in the pyroxene as a first phase of alteration. During the second phase the pyroxene is altered to actinolitic amphibole which appears as isolated flakes within the pyroxene, later the entire pyroxene crystal becomes filled with colourless amphibole. At this stage Fe, Ti, Al and K and Na are introduced internally from the rock-mass itself into the altering mineral. Some Ca is removed simultaneously. Finally, the amphibole changes into a green hornblende with additional introduction of the above elements. During the last phase the crystal boundaries of the original pyroxene are exceeded and the amphibole overflows from the pyroxene crystal spaces at the expense of the adjoining plagioclase that participates in the reaction. The density of the uralitized rock is somewhat lower than that of an unaltered counterpart. It is postulated that some silica is removed during the process to account for the drop in the density.
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| ISSN: | 0367-5211 1799-4632 |