On the issue of uralitization
Abstract
The first conclusion to be drawn from the observations made is the undeniable connection between the formation of actinolite and the decomposition of plagioclase. This connection is so inseparable that, as mentioned, augite decidedly never comes into contact with plagioclase pseudomorphs anywhere. We are, of course, unaware of the immediate primary cause of the decomposition of plagioclase and augite, and it undoubtedly stems from the still-unknown composition of the mineralized solution that penetrated the rock, which, however, must have contained both CaO (from the decomposition of plagioclase) and K₂O (otherwise muscovite would not have formed), with the first component diffusing from the plagioclase and the second diffusing toward it. And since at the points where the diffusing components exited the boundaries of the plagioclase, we see the transformation of augite into actinolite, and since CaO is the only component originating from the plagioclase whose content in actinolite is greater than in augite, we must conclude that it was precisely this component that was halted and absorbed by the augite, which was also affected by the overall chemical alteration of the rock—more pronounced in the plagioclase than in the augite.
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