Informatics Publishing Limited

Sumana Dasgupta ¹, Jyotisankar Ray ¹, Abhijit Mazumder ¹, Niroj K. Sarkar ², Sumita Das ¹, Chandrani Dasgupta ¹

Affiliations
1 Department of Geology, Calcutta University, 35, Ballygunge Circular Road, Calcutta 700 019, IN
2 59/3, Tatipara Lane, Howrah, West Bengal, IN

Abstract

The porphyritic granite bodies occurring around Raghunathpur have been studied petrographically to find out correlation characteristics among several mineralogical parameters with the help of systematic grid-sampling and modal analyses. Q-A-P diagram clearly suggests that the porphyritic granite bodies belong either to tondite or quartz-rich granitoid. The quartz-rich granitoids of porphyritic granite bodies are found to have distinct spatial control. Average mineralogical composition of porphyritic granite bodies and nature of correlation amongst significant parameters have been worked out following statistical procedures. The correlations among different mineralogical parameters however, yield poor values indicating the effects of assirnilation/granitisationlmagma mixing. A fair degree of silica enrichment, imposed on the crystallising magma parental to the porphyritic granite, has been suggested for its genesis, which is also corroborated by textural evidences.

Keywords

Porphyritic Granite Bodies, Correlation Characteristics, Mineralogy, Petrogenesis, Purulia, West Bengal.

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Pawan Govil ¹, Abhijit Mazumder ¹, Anoop Tiwari ¹, Sandeep Kumar ²

Affiliations
1 National Centre for Antarctic and Ocean Research, Headland Sada, Vasco-da-Gama, Goa - 403 804, IN
2 Geology Department, Banaras Hindu University, Varanasi, Uttar Pradesh - 221 005, IN

Abstract

A sediment core (L2) from Larsemann Hills, Antarctica was analyzed for Biogenic Silica (BSi), Sand (%) and Total Organic Carbon (TOC). The 78 cm core length represents the time span of ~8.3 cal ka BP. The values of BSi from the core show prominent high productivity from ~8.3 to ~6 cal ka BP in comparison to less productivity in mid-late Holocene (~6 cal ka BP to recent). Moreover, high sand (%) infers the glacio-fluvial deposition from ~8.3 to ~5 cal ka BP TOC shows little variation through out the core, except in the upper ~10 cm (~4 cal ka BP) part wherein it is comparatively high. The increased TOC in the upper part of the core possibly indicates presence of algal mat due to exposure of the lake to the ice free (glacier free) conditions.

Keywords

Climate, Sediment Core, Holocene, Larsemann Hills.

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