Petrology and associated alterations of younger granitoids of Peninsular Gneissic Complex of Mall area, Eastern Dharwar Craton, Southern India.

  • Unique Paper ID: 161958
  • Volume: 10
  • Issue: 7
  • PageNo: 71-82
  • Abstract:
  • monzonites and diorites. The northern part of the EDC comprises of Peninsular Gneissic Complex –II (PGC-II) of Archean to Paleoproterozoic ages. It comprises of hybrid granite gneiss, grey hornblende biotite granite, grey porphyritic granite, grey biotite granite, grey hornblende granite, alkali feldspar granite and pink granite which were later categorized as Tonalite-Granodiorite- Monzogranite (TGM) suite and Monzogranite-Syenogranite (MS) suite. These litho-types are intruded by pegmatites, quartz veins and basic dykes of dolerite, gabbro and pyroxenite. The supracrustals belonging to Dharwar Supergroup are represented by amphibolite and meta basalt which occur as rafts/enclaves within the Peninsular Gneissic Complex-II. Alteration zones, most important features of terrain which are imprints of later phase activities including deformation, hydrothermal and mineral fluids. Study of these alteration zones may help in understanding the deformational and associated late phase hydrothermal events. The present study is about bringing out the alterations within the granitoids of Peninsular Gneissic Complex- II (PGC-II) which is one of the characteristic features of granitoids of Mall area of Nalgonda District, Telangana. These alterations are mainly associated with shear zones and joint planes within the granitoids. The granitoids are part of younger granitoids of PGC-II of Eastern Dharwar Craton covering parts of Toposheet 56L/09 & L/13 in Nalgonda and Ranga Reddy districts of Telangana, South India. The shear planes within the granitoids area are probable sources of carrying out the potassic and chloritic material into the surrounding rocks through joint/fracture planes. The alteration is present in both pervasive and channel flow. These alteration zones are usually associated with fluoride, hematite, pyrite, molybdenum and REE phases. Petrographic studies including SEM reveals that these alterations helped in enrichment of REE phases and a few sulphide phases within the host rock. Chemical analysis reveals that the host rock i.e., Porphyritic alkali feldspar granite contain Molybdenum upto 5.5 % and upto 2000 ppm of TREE with enrichment of LREE (La, Ce, Nd and Sm). Progressive approach towards these alteration

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