| 释义 |
ptygmatic, a. Geol.|tɪgˈmætɪk|
[ad. Sw. ptygmatisk (J. J. Sederholm 1907, in Bull. de la Commission Géol. de Finlande xxiii. 89), f. Gr. πτύγµα, πτύγµατ- folded matter: see -ic.]
Applied to the highly sinuous and often discordant folding exhibited by the veins in some gneisses and migmatites, and to the veins themselves.
1907J. J. Sederholm in Bull. de la Commission Géol. de Finlande xxiii. 110 [English summary of original Sw. article.] The primary folding caused by melting, he designates as ptygmatic... These suggestions are made with every reservation. 1926G. W. Tyrrell Princ. Petrol. xxi. 333 (caption) Ptygmatic folding of a quartz vein in amphibolite. 1952Geol. Mag. LXXXIX. 1 The term ‘ptygmatic’ was originally coined by Sederholm in 1907 (p. 110) to describe ‘the primary folding caused by melting’ in gneisses and migmatites. The word.., as defined, would embrace most of the contortions, many of which are now included in the term ‘flow fold’, commonly seen in migmatite zones the world over... The term was later restricted by Sederholm (1926) to those tortuous quartzo-felspathic veins, which occur in areas of granitization. 1970K. C. Jackson Textbk. Lithol. vii. 420 (caption) Ptygmatic folding of a pegmatite dike in gneiss.
Hence ptygˈmatically adv., in a way characteristic of ptygmatic folds; also (as a back-formation) ˈptygma, a ptygmatic fold.
1928Summary of Progr. Geol. Survey Gt. Brit. 1927 ii. 72 Other observers of what are certainly ptygmatically folded veins have not accepted Sederholm's explanation. 1944Trans. R. Soc. Edin. LXI. 228 The foliation (gneissic structure) of the host rock appears to conform to the plications of the ‘ptygma’. 1960Rep. 21st Internat. Geol. Congr. XIV. 138 It is concluded that ptygmas could have been formed as the result of development in a passive host or possibly, though improbably, as the result of magmatic flowage. 1971Scottish Jrnl. Geol. VII. 316 Pre-D2 quartz veins are..ptygmatically folded when at high angle to S2. |