Title: Extrusive and Intrusive Igneous Rocks as Products of Magmatic Differentiation
Abstract: Prof. W. G. Brögger, in dedicating to me his recent work on ‘Die Eruptionsfolge der triadischen Eruptivgesteine bei Predazzo in Südtyrol,’ 1 has not only honoured me by this token of his friendship, which I prize highly, but also by associating my name with a work which commands my admiration, and with which I am in the most hearty accord. His treatment of the igneous rocks in the region of Predazzo as a generic series intermediate in composition between a granite-diorite-gabbro series and a granite-syenite (elaeolite-syenite) series is fully justified by their chemical and mineral composition and by their geological association ; and for the order in which these rocks have been erupted he has given ample evidence. The intrusive character of the granular rocks is clearly established, and the fantastic theory of Reyer abundantly disproved. So also the discussion of Kjerulf and Michel-Lévy’s hypotheses, regarding the melting and assimilation of overlying rocks by molten granitic magmas, leaves nothing to be said in further refutation of these suggestions, so far as they relate to the intrusion of igneous magmas that come within the range of our investigation. To suppose that such a process may have been active in the earliest period of the cooling globe is quite reasonable. It implies a very highly-heated magma, and shifting temperature or convection-currents. As applied by Suess to account for the great craters of the moon, it appears highly probable. But there is no evidence that such a melting has taken place in the
Publication Year: 1896
Publication Date: 1896-02-01
Language: en
Type: article
Indexed In: ['crossref']
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Cited By Count: 1
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