A Metamorphosed, Layered Alpine-Type Peridotite in the Langavat Valley, South Harris, Outer Hebrides

A. Livingstone
Department of Geology, The Royal Scottish Museum, Edinburgh, EH1 1JF

Summary: A layered alpine-type peridotite, of pre-Scourian age(?), has been metamorphosed in the granulite facies then partially retrogressed to greenschist facies assemblages. Following granulite facies metamorphism of the dunite-harzburgite peridotite, granitization and metasomatism modified the peridotite by adding calcium and generated olivine-tremolite rocks. Anthophyllite-rich rocks developed from localized orthopyroxene-rich zones. The main epoch of serpentinization followed after tremolite formation and removed a portion of the calcium previously added, but with negligible effect upon the original trace-element content. Between tremolite generation and the main period of serpentinization greenschist facies assemblages formed. The layered rocks possess a repetitive, chemical variation normally attributable to basic igneous processes, although they may have formed either by vein metasomatism or by metasomatism of a disrupted layered igneous series. Twelve rock and five mineral analyses are presented, and trace element data for twenty-one rocks.

Mineralogical Magazine; March 1976 v. 40; no. 313; p. 493-499; DOI: 10.1180/minmag.1976.040.313.09
© 1976, The Mineralogical Society
Mineralogical Society (www.minersoc.org)