Geological Tour of Devonian and Ordovician Magmatism of Kuznetsk Alatau and Minusinsk Basin by Richard Ernst & Vassily V. Vrublevskii & Platon Tishin

Author:Richard Ernst & Vassily V. Vrublevskii & Platon Tishin
Language: eng
Format: epub
ISBN: 9783030295592
Publisher: Springer International Publishing

The macroscopic appearance of these listed varieties of volcanic units are similar to those in Section No. 2. These units are lilac-gray, maroon-brown, and yellow-brown formations with distinct fine, and less often coarse platy jointing. Often present is selective reddening of the plagioclase porphyritic phenocrysts (in lavas) and pyroclasts (in tuffs), often along cracks and leading to the appearance of a mosaic of orange and brick-red spots (Fig. 4a, b). This appearance may be due to the processes of auto-metasomatic albitization, since the secondary albite is always brightly-colored red with thin hematite dust during microscopic examination in transmitted light, which was first noticed by Bognibov (1974). Another proposed explanation for the origin of spotted appearance is the burn effect of dry hot gas jets moving along cracks during the cooling of lava flows (Peshekhonov et al. 1991).

Fig. 4Albitization of tuffs of the Lower Matarak subformation concentrated along glassy lenses (a) and along cracks (b)

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