| 释义 |
rapakivi Petrol.|ræpəˈkiːviː, ˈræpəkiːviː|
Also † Rapa-, -kiwi.
[a. Finn. rapakivi crumbly stone, f. rapa mud + kivi stone.]
A form of granite characterized by plagioclase mantles surrounding large crystals of potash feldspar; orig. spec. that occurring in southern Finland. Usu. attrib.
[1784R. Kirwan Elem. Mineral i. viii. 149 A stone of this sort which moulders by exposures to the air, is found in Finland, and is said to contain sometimes saltpetre, and sometimes common salt, it is there called Rapakivi.] 1795Ibid. (ed. 2) I. 345 The aggregate of felspar and mica is called Rapakivi. 1906J. P. Iddings Rock Minerals ii. 487 Quartz..may often be the darkest mineral visible megascopically, as in some varieties of rapakiwi from Finland. 1933R. A. Daly Igneous Rocks viii. 141 Sederholm concluded that the Rapakivi granite in southern Finland is a thick flow, poured out on the surface of a fault trough or graben, the liquid rising along one or more of the faults concerned. 1944Proc. Geologists' Assoc. LV. 74 The typical rock, the rapakivi granite proper, is characterised by abundant large ovoids..of potash-felspar which lie in a matrix of quartz, potash-felspar, plagioclase and dark mica, and, sometimes, hornblende; often the potash-felspar ovoids are mantled by a ring made up of small oligoclases, and it is this striking phenomenon which is usually in mind when the rapakivi granites are considered. 1976Nature 10 June 482/2 The granites locally display the well developed rapakivi texture characteristic of anorogenic granites throughout the world. |