An excursion in the French–Italian Alps: the 'Atlantic'-type ophiolite at Mont Chenaillet

In his famous address to the Geological Society of America in 1957, H. H. Read concluded that 'there are granites and granites'. This is equally true for ophiolites, slices of oceanic lithosphere produced by sea-floor spreading and preserved by obduction during plate collision. Although they form in similar ways, it is clear that there are different types of ophiolite which originate under different conditions. Compared to the 'classic' ophiolites of Oman, many, such as those in the Alps, lack a sheeted dyke complex and were for a long time considered abnormal. Analogues for this type have now been found forming today and they occur when the rate of spreading is slow.