Advanced carbonation of felsic and mafic rocks, very rarely, creates fenite, a metasomatic alteration caused particularly by carbonatite intrusions.
42.
The central circular part of highly dissected, craggy hills of carbonatite is asymmetrical and about 200 m lower than Karroo ridge.
43.
The 1960 eruption of Ol Doinyo Lengai led to geological investigations that finally confirmed the view that carbonatite rock is derived from magma.
44.
The southern rare earth zone is a 1 kilometre by 1 kilometre area in the low magnetic central core of the Ngualla carbonatite.
45.
The Mud Tank and Mount Weld carbonatites take the form of multi-stage cylindrical intrusive bodies with several distinct phases of carbonatite intrusion.
46.
In nature, carbonate rocks, potentially carbonatite, kimberlites, carbonate-bearing melilitic rocks and other rare alkaline rocks may satisfy these criteria.
47.
"' Carbonatite "'( ) is a type of rock defined by mineralogic composition consisting of greater than 50 percent carbonate minerals.
48.
Most carbonatites tend to include some silicate mineral fraction; by definition an igneous rock containing > 50 % carbonate minerals is classified as a carbonatite.
49.
The Mount Weld carbonatite is unassociated with a belt or suite of alkaline igneous rocks, although calc-alkaline magmas are known in the region.
50.
The subvolcanic and intrusive rocks of the central Kaiserstuhl are plutonic equivalents of the erupted material ( essexite, carbonatite and coarse-granular phonolite ).
