| 释义 |
trachyte Geol. and Min.|ˈtreɪkaɪt, ˈtrækaɪt|
[a. F. trachyte (Haüy); f. Gr. τρᾱχύς rough, or perh. τραχύτης roughness.]
A group of volcanic rocks, having a characteristically rough or gritty surface. The name was given by Haüy to certain volcanic rocks from Auvergne, and at first used in a wide sense; now confined to rocks consisting mainly of sanidine (or glassy orthoclase) felspar, as distinguished from oligoclase- and quartz-trachytes, and intermediate forms: see trachy- b.
1821R. Jameson Man. Min. 427 Rocks of extinct and ancient volcanoes... 1. Trachyte. This rock which is of the nature of felspar, is generally porphyritic, the imbedded crystals being most frequently of the glassy kind. 1830Lyell Princ. Geol. I. 386 These isles are formed of brown trachyte..full of crystals of glassy felspar. 1854Murchison Siluria xviii. 425 These were, in ancient times, penetrated by granites, porphyries, trachytes, and other eruptive matters. 1876Page Adv. Text-bk. Geol. v. 105 The trachytes are rough-grained subcrystalline varieties of felspathic lava. 1911Encycl. Brit. XXVII. 116/2 Trachyte..was long used in a much wider sense..in fact it included quartz-trachytes (now known as liparites and rhyolites) and oligoclase-trachytes, more properly assigned to Andesites.
b. attrib., as trachyte rock, trachyte porphyry; trachyte tuff, a tuff having the composition and structure of trachyte.
1872C. King Mountain. Sierra Nev. ix. 188 Rounded domes of trachyte rock. 1877Tylor in Nature 5 July 191/1 In a still larger chulpa [i.e. Peruvian burial-tower] there are hewn trachyte blocks as large as twelve feet long [etc.]. 1885Geikie Text-bk. Geol. ii. ii. vii. (ed. 2) 166 Thus we have felsite-tuffs, trachyte-tuffs, basalt-tuffs, pumice-tuffs, porphyrite-tuffs, etc. |