Skip to main content Accessibility help

The riebeckite-bearing dikes of Shetland (With Plate III)

  • James Phemister, C. O. Harvey (a1) and P. A. Sabine (a1)


The peninsula in which the mainland of Shetland ends north of Ronas Voe and Colla Firth is occupied mainly by the Ronas Hill Granite. This body is intrusive into a metamorphic series consisting of orthogneiss on the north and paragneiss oil the north-east, east, and south-east of tile peninsula. It is a biotite-granophyre within which earlier bodies of basic rock varying from diorite to gabbro are found. It is unsheared and unfoliated and is cut by a swarm of dikes with north-south trend which extends from tile north coast to Ronas Voe. There is evidence also of the existence of dikes earlier than the granite. The later dikes comprise spessartine, microdiorite, porphyrite, quartzfelspar- porphyry, and a great variety of felsites which are generally granophyric and spherulitic. Many of the felsites contain riebeckite and aegirine and have a corresponding blue or blue-green colour. From observation of chilling of dike against dike and intersection of dike by dike it has been found that tile basic dikes, spessartine, microdiorite, and porphyrite, are the oldest of the suite, the quartz-felspar-porphyries are older than the felsites, and the blue riebeckite-felsites are younger than white, pink, and dull red felsites which contain neither aegirine nor riebeckite



Hide All
Berman, (H.) and (E.S.), Larsen., 1931. Composition of the alkali-amphiboles. Amer. Min., vol. 16, p. 140.
(T.M.), Finlay., 1930. The Old Red Sandstone of Shetland. Pt. II. North-Western Area. Trans. Roy. Soc. Edin., vol. 56, p. 671.
(A.F.), Hallimond., 1943. On the graphical representation of the calciferous amphiboles. Amer. Min., vol. 28, p. 65.
(C.O.), Harvey., 1939. Simple method for determination of water in silicates. Bull. Geol. Surv. Gt. Brit., no. 1, p. 8.
Prnllips, (F. Coles), 1926. Note on a Riebeckite-Bearing rock from the Shetlands. Geol. Mag., vol. 63, p. 72.
(P.A.), Sablwe., 1950. The optical properties and composition of the acmitic pyroxenes. Min. Mag., vol. 29, p. 113.
Suzuki, (J.), 1938. On the Occurrence of Aegirine.Augite in Natrolite Veins in the Dolerite from Nemuro, Hokkaido. Journ. Fac. Sci. Hokkaido Imp. Univ., ser. IV, vol. 4, p. 183.
(G.W.), Tyrrell., 1928. The Geology of Arran. Mem. Geol. Surv. Gt. Brit.
(B.E.), Warren., 1930. The crystal structure and chemical composition of the monoclinic amphiboles. Zeits. Krist., vol. 72, p. 493.
Washington, (H. S.) and (H.E.), Merwin., 1927. The acmitic pyroxenes. Amer. Min., vol. 12, p. 233.

The riebeckite-bearing dikes of Shetland (With Plate III)

  • James Phemister, C. O. Harvey (a1) and P. A. Sabine (a1)


Full text views

Total number of HTML views: 0
Total number of PDF views: 0 *
Loading metrics...

Abstract views

Total abstract views: 0 *
Loading metrics...

* Views captured on Cambridge Core between <date>. This data will be updated every 24 hours.

Usage data cannot currently be displayed