| 释义 |
ignimbrite Geol.|ˈɪgnɪmbraɪt|
[f. L. ign-is fire + imbr-is, imber shower of rain, stormcloud + -ite1.]
Any pyroclastic rock, typically a welded tuff, deposited from or formed by the settling of a nuée ardente.
1932P. Marshall in N.Z. Jrnl. Sci. & Technol. XIII. 200 The type of rocks formed in this way varies greatly, but it is suggested that they should all be included in a separate group, for which the name ‘Ignimbrite’ seems satisfactory. 1959A. McLintock Descr. Atlas N.Z. 11 Early in the Pleistocene Period, huge eruptions there formed a plateau of rhyolitic rock known as ‘ignimbrite’, some 10,000 square miles in extent. 1962E. A. Vincent tr. Rittmann's Volcanoes ii. 80 Ignimbrites, or welded tuffs, are formed in enormous quantities from overflowing glowing clouds in fissure eruptions of very acid magmas. The incandescent ash particles are intimately fused to one another and attain a largely pseudoliquid state, especially in the deeper portions of the deposit, so that the massive rock which results often shows columnar jointing and is easily confused with a rhyolitic lava. 1969C. Ollier Volcanoes vii. 73 Ignimbrite will be used here in the sense of Cook (1966). This is a rock unit term, and should not be used as a petrological term: several petrological types can give rise to ignimbrites though rhyolite and andesite predominate. Neither does the term imply any post-depositional alteration such as welding, though this may be present. 1970Nature 12 Sept. 1125/1 This..is matched in volume only by the large welded tuff sheets of the central North Island of New Zealand, the type locality for ignimbrite. |