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S. Bhattacharya & S. K. Sen comment: In a recent paper, Dobmeier & Raith (2000) have claimed to have provided ‘conclusive evidence’ that the patchy charnockites in the Chilka Lake area were formed from the leptynites which enclose them. This runs counter to our interpretation that these patches were derived from larger charnockitic layers through deformation and migmatization (Bhattacharya, Sen & Acharyya, 1993). Any re-interpretation is in order, provided it does not ignore or distort the field facts. In our opinion, these authors have done so, and we are constrained to make the following points.
1. Definition of charnockite and its use
Dobmeier & Raith (2000) refer to Streckeisen (1976) for definition and further alleged that improper use of the term charnockite ‘allowed pooling of charnockite with enderbite, thereby leading to petrographic confusion and erroneous interpretations of charnockite formation’ (p. 29).
Charnockites and enderbites as defined in Streckeisen (1976) occur together, along with intermediate varieties, in many granulite terranes which contain these rocks (Newton, 1992). It may be recalled that in the Streckeisen system of nomenclature charnockites have alkali feldspar:plagioclase proportions varying from 90:10 to 35:65; while in enderbites they vary from 10:90 to 0:100. Rocks with alkali feldspar:plagioclase ratios falling in between are styled charno-enderbites.
In the Chilka area many larger bands which have all been labelled as enderbites by Dobmeier & Raith (2000) are charnockites according to this definition. In the five sets of modal analyses reported in Bhattacharya, Sen & Acharyya (1993) three are distinctly charnockites in the cores, their relative alkali feldspar:plagioclase proportions being 16:20, 18:20 and 14:18. Among the other two, one with the ratio 16:25 is practically a charno-enderbite, while the other with 32:7 is an alkali feldspar charnockite. Thus Dobmeier & Raith’s generalization that all larger bands are enderbites is incorrect.
The most significant aspect of the modal data from …