Hostname: page-component-586b7cd67f-vdxz6 Total loading time: 0 Render date: 2024-11-30T20:29:17.811Z Has data issue: false hasContentIssue false
  • English
  • Français

A Note on Rhythmic Layering in Hornblende-rich Picrite and Dolerite Intrusions, near Rhiw, Caernarvonshire

Published online by Cambridge University Press:  01 May 2009

T. R. W. Hawkins
T. R. W. Hawkins
Affiliation:
Geological Survey Office, Ring Road Halton, Leeds, 15.
Get access Rights & Permissions [Opens in a new window]

Abstract

Banding, recorded by previous workers in hornblende picrite and dolerite intrusions near Rhiw, is found to be rhythmic layering. At least three major units (200 to 250 feet in thickness) have been recognized, and intermediate and minor scale units also occur, predominantly within the basal major unit. The majority of the rocks display cumulate textures, and crystallization appears to have been completed by heteradcumulus or adcumulus growth. Thin coarser-grained sheets, rich in plagioclase, and slightly discordant to the layering, are considered to be contemporaneous segregation veins.

Type
Articles
Information
Geological Magazine , Volume 102 , Issue 3 , June 1965 , pp. 222 - 226
Copyright
Copyright © Cambridge University Press 1965

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

REFERENCES

Bonney, T. G., 1881. On a Boulder of Hornblende Picrite near Pen-y-Carnisiog, Anglesey. Quart. J. geol. Soc. Lond., 38, 137.CrossRefGoogle Scholar
Brown, G. M., 1956. The Layered Ultrabasic Rocks of Rhum, Inner Hebrides. Phil. Trans. (Ser. B), 240, 1–55.Google Scholar
Eldsden, J. V., 1888. Notes on the Igneous Rocks of the Lleyn Promontory. Geol. Mag., 5, 305–8.Google Scholar
Harker, A., 1888. The Eruptive Rocks of Sarn. Quart. J. geol. Soc. Lond., 44, 442–461.CrossRefGoogle Scholar
Harker, A., 1889. The Bala Volcanic Series of Caernarvonshire and associated Rocks, Cambridge.Google Scholar
Matley, C. A., 1932. The geology of the country around Mynydd Rhiw and Sarn, south-western Lleyn, Caernarvonshire. Quart. J. geol. Soc. Lond., 88, 238–273.CrossRefGoogle Scholar
Ramsay, A. C., 1866. The Geology of North Wales. Mem. Geol Surv. U.K.Google Scholar
Tawyney, E. B.,1880. Woodwardian Laboratory Notes: North Wales Rocks. Geol. Mag., 7, 207–215 and 452–8.CrossRefGoogle Scholar
Teall, J. J. H., 1888. British Petrography, London.Google Scholar
Wager, L. R., and Deer, W. A., 1939. Geological investigations in East Greenland. Part III—The petrology of the Skaergaard intrusion, Kangerdlugssuaq. Medd. Grønland, 105, 1–352.Google Scholar
Wager, L. R., and Brown, G. M., 1951. A note on rhythmic layering in the ultrabasic rocks of Rhum. Geol. Mag., 88, 166–8.CrossRefGoogle Scholar
Wager, L. R., and Brown, G. M., and Wadsworth, W. J., 1960. Types of Igneous Cumulates. J. Petrol., 1, 73–85.CrossRefGoogle Scholar