THULEAN BASALTS 780 



The rocks of the Spitsbergen group (including King Charles Land) 

 are fairly well known and we have several analyses of them. 29 The lavas 

 are mostly basalts, but some "trachydolerites" and nephelite basanites 

 occur. The basalts show some variation, but there are the two usual 

 main types, one porphyritic, with labradorite phenocrysts, and the other 

 densely aphyric. The texture is ophitic, the plagioclase and augite are 

 as usual, there is a little olivine, and sometimes a little glass. An average 

 of 13 analyses is given in Table IX. The lower iron oxides and lime and 

 the higher alkalies show the decided alkalic affinities of the basalts. 



We have little information as to the rocks of Franz Josef Land and 

 but two analyses of them. 30 The basalts are aphyric for the most part, 

 but some are porphyritic, with labradorite phenocrysts, and Teall de- 

 scribes one with augite phenocrysts. The mode is the usual one of the 

 plateau basalts, but a little olivine is present in a few specimens. Al- 

 though the texture is generally ophitic, yet this is not so common as 

 among the basalts of Iceland and the Faroes, as was pointed out by Teall 

 Many of Teall's specimens contain glass. The average of the two analyse - 

 available is given in Table IX. 



The chemical characters of the Thulean basalts are shown in a series 



of averages for the various districts given in Table IX. These averages 



are of the basalts alone and do not include any analyses of rhyolites or 



other non-basaltic rocks. 



Table IX 



Averages of Analyses of Thulean Basalts 



12345678 



Si0 2 46.54 48.64 49.04 45.80 45. OS 49.05 48.09 47.46 



A1 2 3 14.96 14.05 13.54 13.32 14.15 13.47 13.77 13.89 



Fe 2 3 4.34 3.03 2.43 5.12 2.28 3.27 4.58 3.58 



FeO 9.07 9.96 10.46 9.46 8.59 9.15 9.05 9.38 



MgO 7.29 5.26 7.42 6.34 7.01 8.16 6.03 6.79 



CaO 9.25 9.92 10.55 9.64 10.20 8.22 11.04 9.83 



Na 2 2.84 3.06 2.43 2.39 3.99 3.11 2.47 2.90 



K 2 0.78 0.75 0.53 1.36 1.79 1.50 0.39 1.01 



H 2 0± 2.69 1.04 0.67 2.00 0.90 0.89 2.15 1.4S 



Ti0 2 2.15 3.78 2.51 3.84 2.93 1.89 1.89 2.71 



P 2 5 0.21 0.38 0.38 0.34 0.62 0.84 0.24 0.43 



MnO 0.29 0.18 0.20 0.18 0.22 0.18 0.29 0.22 



Incl 0.10 0.19 0.31 2.68 0.03 0.08 0.22 



100.51 100.05 100.35 100.10 100.44 99.76 99.67 99.90 



29 H. Backlund : Tsch. Min. Pet. Mitth., vol. 26, 1907, p. 357 ; A. Hamberg : Geol. For. 

 Forh., vol. 21, 1899, p. 509 ; V. M. Goldschmidt : Skr. Videns. Selsk. Christ., 1911, no. 9 ; 

 Holmes and Harwood : Min. Mag., vol. 18, 1918, p. 205. 



30 J. J. H. Teall : Quart. Jour. Geol. Soc, vol. 53, 1897, p. 477, and vol. 54, 1898, p. 

 G46 ; Holmes and Harwood : Min. Mag., vol. 18, 1918, p. 209. 



