No abstract

This paper presents field geological and petrographic aspects of various granitoid units occurring around Khatgaon area in the southeastern part of district of Maharashtra. The study area is bestowed with granitoids of Archaean to Proterozoic age overlain by Deccan basalts of Cretaceous age. Three main types of granitoids were identified in the study area viz., older granites, gneissic/foliated younger granites. These granitoid rocks are traversed by dykes, veins and veinlets of felsic and mafic composition. Although these granitoids are similar in mineralogy, they exhibit differences in petrographic characteristics. The granitoids of the study area, especially the gneissic granitoids, comprise felsic and mafic lenticular enclaves of different sizes. Petrographically older and younger granitoids show medium to fine-grained, porphyritic and inequigranular textures. The gneissic rocks foliation. At the contact of mafic enclaves and gneissic zones, conspicuous variation in mineralogy is observed in thin-sections. Presence of enclaves indicates coexistence and mixing of both felsic and mafic magmas at the source. The typical textures perthitic, graphics and lamellar twinning indicate a direct magmatic origin for these granitoid rocks. The presence of pyrite mineralization at Khatgaon indicates late stage hydrothermal activity associated with felsic veins.

The pedogenic carbonates, found mainly in arid and semi-arid regions of the world, are commonly referred to as calcretes or caliche or kankar authigenic carbonate products which occur in association with soil, forming the residual regolith. Many rock types can produce calcretes upon weathering and denudation, but calcrete derived from certain rocks like kimberlite/lamproite acts as an exploration guide. Calcrete is a prominent sampling medium in diamond-rich countries like Australia and South Africa whereas it has not received popularity in the Indian context. Kimberlites being ultrapotassic in nature and owing to the enrichment of olivine and serpentine often produce calcrete duricrust as a capping. Recently more than twenty lamproites have been discovered in the Telangana state by the Geological Survey of India. These occurrences unravel a new panorama that the state has a substantial potential for occurrence of more kimberlite/lamproite clan rocks. An attempt has been made here to test the geochemical affinity of calcretes from various locations within Nalgonda district. The geochemical data of calcrete samples of this study has been compared with published geochemical data of lamproites of Ramadugu Field, to understand their geochemical association to kimberlite/lamproite. The calcretes are low in SiO 2 (33.92-45.1 wt %), high in K 2 O (1.07-2.21 wt %) and CaO (0.78 When compared to other major elements, MgO displays low concentration. The trace elements are @ IJTSRD |

No abstract

No abstract