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Abstract
The Skaergaard intrusion in East Greenland has been studied for more than forty years and although a wealth of information has been collected, the history of the intrusion is only partially understood. One of the unresolved problems is the origin of distinct textural varieties of apatite found side by side in the rocks from the late stages of the crystallization of the intrusion.
The solution to the problem lies in understanding the details of the cumulus, adcumulus and intercumulus history of apatite. This information may be useful to resolve the current debates on the role of silicate liquid immiscibility (McBirney, 1975) and the means of crystallization (Wager and Deer, 1939; Wager and Brown, 1968; McBirney and Noyes, 1979; Irvine, 1980) in the intrusion.
In order to solve the problem, detailed textural observations of the coexisting apatite morphologies were made, although for only one sample, which came from subzone b of the upper zone of the Skaergaard intrusion. The mineral association, diameter and chlorine content of apatite were determined as a function of textural type. In addition, some of the textural varieties were found to contain single large central inclusions.
As a result of this study, two generations of apatite in the same sample were documented and new evidence concerning the role of silicate liquid immiscibility in the Skaergaard intrusion was found.
