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Petrogenesis of Zincian Spinel from Mamandur Base Metal Sulphide Prospect, Tamil Nadu


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1 Department of Geology, University of Calcutta, 35, Ballygunge Circular Road, Kolkata – 700 019, India
     

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Zincian spinels (gahnites) from the Mamandur Zn-Pb-Cu prospect of the Southern Granulite Terrain have been studied. Gahnites in the quartzofeldspathic gneiss occur either as (a) porphyroblastic grains closely in association with cordierite and sphalerite or as (b) inclusions in poikiloblastic quartz grains, restricted within quartz veinlets. Compositionally these gahnites belong to two different clusters corresponding to two modes of occurrences. The origin of the porphyroblastic gahnites is linked with the process of desulphidation of sphalerite whereas those occurring as inclusions within poikiloblastic quartz are direct crystallisation products from silica rich hydrothermal solution. A new compositional field for this latter group of gahnites is proposed here.

Keywords

Gahnite, Cordierite, Desulphidation, Mamandur, Base Metal.
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  • Petrogenesis of Zincian Spinel from Mamandur Base Metal Sulphide Prospect, Tamil Nadu

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Authors

Biswajit Ghosh
Department of Geology, University of Calcutta, 35, Ballygunge Circular Road, Kolkata – 700 019, India
Sandip Some
Department of Geology, University of Calcutta, 35, Ballygunge Circular Road, Kolkata – 700 019, India
Animesh Thakur
Department of Geology, University of Calcutta, 35, Ballygunge Circular Road, Kolkata – 700 019, India

Abstract


Zincian spinels (gahnites) from the Mamandur Zn-Pb-Cu prospect of the Southern Granulite Terrain have been studied. Gahnites in the quartzofeldspathic gneiss occur either as (a) porphyroblastic grains closely in association with cordierite and sphalerite or as (b) inclusions in poikiloblastic quartz grains, restricted within quartz veinlets. Compositionally these gahnites belong to two different clusters corresponding to two modes of occurrences. The origin of the porphyroblastic gahnites is linked with the process of desulphidation of sphalerite whereas those occurring as inclusions within poikiloblastic quartz are direct crystallisation products from silica rich hydrothermal solution. A new compositional field for this latter group of gahnites is proposed here.

Keywords


Gahnite, Cordierite, Desulphidation, Mamandur, Base Metal.

References