Charnockitic magmatism in southern India

Rajesh, H.M.; Santosh, M.

doi:10.1007/bf02704023

Cited by 90 publications

(56 citation statements)

References 106 publications

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“…The largest charnockite massif of KKB-the Nagercoil massif-is of granitic composition, while the charnockites of MB and NB are largely tonaltic to trondhjemitic in composition (Rajesh and Santosh 2004). It is well known that granites have higher abundance of K, U and Th relative to tonalities and trondhjemites.…”

Section: Discussionmentioning

confidence: 98%

“…This process removes, to a variable degree, biotite from the khondalites giving rise to garnetiferous quartzofeldspathic rock. While some patchy charnockites were developed from khondalite (Ravindra Kumar et al 1985), the major massif charnockites of Nagercoil is considered to be metamorphosed igneous rocks (Rajesh and Santosh 2004).…”

Section: Geologymentioning

confidence: 99%

“…Accessory minerals are zircon and apatite. The whole rock composition ranges between granodiorite and granite (Rajesh and Santosh 2004). The patchy charnockite at Ponmudi developed from biotite-garnet-plagioclase-K-feldspar-quartz-graphite gneiss, a member of the Khondalite Group.…”

Section: Geologymentioning

confidence: 99%

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High radiogenic heat production in the Kerala Khondalite Block, Southern Granulite Province, India

Ray

Roy

Srinivasan

2007

Int J Earth Sci (Geol Rundsch)

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In situ radioelemental (K, U and Th) analysis and heat production estimates have been made at 59 sites in the Kerala Khondalite Block (KKB) of the Southern Granulite Province (SGP) of India. Together with the in situ analyses on granulites and gneisses previously reported from 28 sites, and heat production estimated from the published geochemical analyses on granites and syenites of the KKB, the new data set allows good characterization of heat production for the major granulite facies rocks and granitoids of the KKB. Garnet biotite gneisses are characterized by high levels of Th and U, with mean values of 60 and 3 ppm, respectively. Khondalites, leptynites and charnockites have slightly lower levels of Th (23, 20 and 22 ppm, respectively) and U (2.9, 2.4 and 0.9 ppm, respectively). The mean K, U, Th abundances for the granites, leucogranites and granitic gneisses ranges from 3.9 to 4.3%, 2.6 to 4.3 ppm, 22 to 50 ppm respectively, and for the syenites 4.8%, 2 ppm and 5.7 ppm. Mean radiogenic heat production values for garnet-biotite gneiss, khondalite, leptynite and charnockite are 5.5, 2.7, 2.4 and 2.2 lW m -3 , respectively. For the granites, leucogranites, granitic gneisses and syenites it is 2.6, 3.4, 4.6 and 1.4 lW m -3 , respectively. Heat production of granulite facies rocks, which are the most abundant rocks in KKB, correlate well with Th, but less with U, suggesting that variation is caused by Th and U bearing accessory minerals such as monazite and zircon. The high heat production of the KKB granulites are in contrast to the low heat production of the Late Archaean granulites of the Northern Block (NB) of the SGP which are highly depleted in radioelements and also the granulites of Madurai Block (MB) that have higher radioelemental abundances than in the granulites of the NB. The high heat production of the KKB granulites could be due to the nature of protoliths and/or metasomatism associated with Neoproteroic-to-Pan African alkaline magmatic activity represented by alkali granite and syenite-carbonatite emplacements and emplacement of pegmatites.

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Section: Discussionmentioning

confidence: 98%

Section: Geologymentioning

confidence: 99%

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High radiogenic heat production in the Kerala Khondalite Block, Southern Granulite Province, India

Ray

Roy

Srinivasan

2007

Int J Earth Sci (Geol Rundsch)

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“…The Charnockite group of rocks are also migmatised to varying degrees resulting in retrogression and conversion into migmatite complex comprising different types. The migmatite complex comprises different types of gneiss, such as garnetiferous, biotite gneiss, hornblende gneiss, augen gneiss and garnetiferous gneiss (Rajesh and Santosh 2004).…”

Section: Basement Rockmentioning

confidence: 99%

Foundation Floor Geological Mapping of a Nuclear Reactor

2010

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Foundation floor mapping is essential for very important structures to provide permanent data set for geological interpretations. Prototype fast breeder reactor (PFBR) is being constructing at Kalpakkam, India. Nuclear Island Connected Building (NICB) is the main nuclear safety related structure of (PFBR), and is resting on a raft of 101.5 m 9 93 m size at about 20 m below the existing ground level. Geological floor mapping was prepared after the excavation. 2 m 9 2 m grids were used for sampling study and mapping of the walls and floor. The floor region of this raft foundation was seen to contain certain weathered zone with fractures of thickness of in the order of 2 m. No evidences of faulting/shearing were observed on the surface of the floor area. The entire floor area was made up of compact and sound rock mass. However, there were some isolated patches of soft weathered/altered rock and small fractures in the rock. The structural features observed during the mapping exercise indicated the need for consolidation grouting so that the entire floor area function as single rock mass. This foundation geological map will assist in making better interpretation of post-construction foundation instrumentation data.

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“…This may relate to an early component of the pervasive late Neoproterozoic to early Palaeozoic (PanAfrican) overprint as revealed by 0.45-0.6 Ga zircon rims, monazite and uraninite ages (Santosh et al, 2003). The Cambrian-Ordovician ages as well as their distinct alkaline chemistry relate to post-orogenic magmatism in an extensional setting for a suite of younger granites that occurs within the Madurai Block as well as within the late Neoproterozoic shear/suture zones in southern India (Rajesh, 2004;Rajesh and Santosh, 2004).…”

Section: Geological Settingmentioning

confidence: 99%

Geothermobarometry of granitic pegmatites of Nagamalai - Pudukottai area, Madurai Block, South India

Manu¹,

Kumar²

2018

ESI

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The pegmatites in the Neoproterozoic A-type granites of NagamalaiPudukottai area are of two types-gray and pink. These pegmatites contain hornblende. In this work an attempt is made to understand the nature of magma, the process of crystallisation and the Pressure-Temperature (P-T) conditions of formation of the rock with the help of the Electron microprobe (EPMA) study of hornblende from both varieties of pegmatites.The EPMA of the hornblende from the granitic pegmatites indicate their calcic nature. The structural formula of these calcic amphiboles corresponds to hastingsite. The Al tot pressure calibration suggests the formation of the gray and pink pegmatites to be 5 kilobar (average). Based on the amphibole-plagioclase thermometer the magmatic temperature deduced for gray and pink pegmatites is 760 o C and 745 o C respectively. These temperature values suggest the later formation of pink pegmatites. The study reveals the formation of the granites and associated pegmatites from a less evolved, hydrous, and less viscous calcic melt in the upper crust.

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Charnockitic magmatism in southern India

Cited by 90 publications

References 106 publications

High radiogenic heat production in the Kerala Khondalite Block, Southern Granulite Province, India

High radiogenic heat production in the Kerala Khondalite Block, Southern Granulite Province, India

Foundation Floor Geological Mapping of a Nuclear Reactor

Geothermobarometry of granitic pegmatites of Nagamalai - Pudukottai area, Madurai Block, South India

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