Alkaline rocks appear to be widespread in the 'Precordillera' (approximately between 39°-33°30'S and 68-69°W) but detailed distributions and descriptions are not available.
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East of Las Salinas a gabbro occurs which contains abundant, interstitial nepheline.
Among the voluminous volcanics of the Cordillera Principal alkaline rocks are scarce. However, tephrites and basanites, essexites with nepheline, analcime and biotite, trachytes and trachydolerites and rocks described as bostonites, but containing sodalite and nepheline, all occur.