Granitoids around the Malanjkhand copper deposit: Types and age relationship |
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| Authors: | M K Panigrahi A Mookherjee G V C Pantulu K Gopalan |
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| Institution: | (1) Department of Geology and Geophysics, Indian Institute of Technology, 721 302 Kharagpur;(2) Present address: Department of Geological Sciences, Jadavpur University, 700 032 Calcutta;(3) National Geophysical Research Institute, Uppal Road, 500 007 Hyderabad |
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| Abstract: | On the basis of field relations, petrography and chemistry, three types of granitoids are recognized at Malanjkhand in and
around the copper deposit over an area of about 200 km2. These are (i) a fine grained ‘leucogranite’ of restricted occurrence in the surrounding area (Gr-I); (ii) coarse-grained,
grey in most parts, gneissose granitoid of regional extension (Gr-II); and (iii) the pink-feldspar bearing massive type hosting
the mineralization with occasional representatives in the surrounding country (Gr-III). Gr-I comes out as a distinct entity
on the basis of cross-cutting relation and mineralogical and chemical composition, the Rb-Sr whole rock isochron also giving
a younger age than the other two groups irrespective of the regression model used. Gr-II comes out as the oldest unit but
its age relationship with Gr-III cannot be established unequivocally. An uncorrelated error regression model establishes the
age relationship as Gr-I<Gr-III<Gr-II, whereas a two-error regression model establishes temporal closeness between Gr-II and
III.
The term ‘granitoids’ is being used broadly to include rocks ranging in composition from alkali-granite to tonalite. |
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| Keywords: | Malanjkhand copper deposit granitoids geochronology isochrons initial ratio temporal relation |
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