An Overview of the Carbonatites from the Indian Subcontinent

Randive, Kirtikumar; Meshram, Tushar

doi:10.1515/geo-2020-0007

Cited by 17 publications

(7 citation statements)

References 115 publications

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“…There are a large number of Proterozoic carbonatite complexes (Sevathur, Samalpatti, Jogipatti et al) in southern India belonging to Precambrian (~1600-600 Ma) alkaline magmatism within the Eastern Ghats Mobile Belt (EGMB). They are emplaced within the Precambrian granulite terrains (Southern Ghats Terrain, SGT) along NE-SW trending fault systems [3,4,6].…”

Section: Geological Settingmentioning

confidence: 99%

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Mineralogy of Dolomite Carbonatites of Sevathur Complex, Tamil Nadu, India

et al. 2021

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The main mass of the Sevathur carbonatite complex (Tamil Nadu, India) consists of dolomite carbonatite with a small number of ankerite carbonatite dikes. Calcite carbonatite occurs in a very minor amount as thin veins within the dolomite carbonatite. The age (207Pb/204Pb) of the Sevathur carbonatites is 801 ± 11 Ma, they are emplaced within the Precambrian granulite terrains along NE–SW trending fault systems. Minor minerals in dolomite carbonatite are fluorapatite, phlogopite (with a kinoshitalite component), amphibole and magnetite. Pyrochlore (rich in UO2), monazite-Ce, and barite are accessory minerals. Dolomite carbonatite at the Sevathur complex contains norsethite, calcioburbankite, and benstonite as inclusions in primary calcite and are interpreted as primary minerals. They are indicative of Na, Sr, Mg, Ba, and LREE enrichment in their parental carbonatitic magma. Norsethite, calcioburbankite, and benstonite have not been previously known at Sevathur. The hydrothermal processes at the Sevathur carbonatites lead to alteration of pyrochlore into hydropyrochlore, and Ba-enrichment. Also, it leads to formation of monazite-(Ce) and barite-II.

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Section: Geological Settingmentioning

confidence: 99%

“…The pyrochlore contains 24% of U 3 O 8 [2] and occurred within early generation carbonatite, unlike most other carbonatite complexes in the Indian subcontinent. There are about 360 tons of Nb 2 O and 1.2 million tons of vermiculite reserves in the Sevathur carbonatites [4].…”

Section: Introductionmentioning

confidence: 99%

Mineralogy of Dolomite Carbonatites of Sevathur Complex, Tamil Nadu, India

et al. 2021

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“…Carbonatites are mantle-derived igneous rocks that contain more than 50 modal percent of carbonates and less than 20 wt.% SiO 2 [ 28 , 29 , 30 , 31 , 32 ]. Sillai Patti carbonatite is the second-largest carbonatite complex in Pakistan [ 33 ], after Loe-Shilman carbonatite.…”

Section: Introductionmentioning

confidence: 99%

Detection and Relative Quantification of Neodymium in Sillai Patti Carbonatite Using Decision Tree Classification of the Hyperspectral Data

Qasim

Khan

2022

Sensors

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A recent increase in the importance of Rare Earth Elements (REEs), proportional to advancements in modern technology, green energy, and defense, has urged researchers to look for more sophisticated and efficient exploration methods for their host rocks, such as carbonatites. Hyperspectral remote sensing has long been recognized as having great potential to identify the REEs based on their sharp and distinctive absorption features in the visible near-infrared (VNIR) and shortwave infrared (SWIR) electromagnetic spectral profiles. For instance, neodymium (Nd), one of the most abundant Light Rare Earth Elements (LREEs), has among the most distinctive absorption features of REEs in the VNIR part of the electromagnetic spectrum. Centered at ~580, ~745, ~810, and ~870 nm in the VNIR, the positions of these absorption features have been proved to be independent of the mineralogy that hosts Nd, and the features can be observed in samples as low in Nd as 1000 ppm. In this study, a neodymium index (NI) is proposed based on the 810 nm absorption feature and tested on the hyperspectral images of the Sillai Patai carbonatite samples to identify Nd pixels and to decipher the relative concentration of Nd in the samples based on the depth of the absorption feature. A preliminary spectral study of the carbonatite samples was carried out using a spectroradiometer to determine the presence of Nd in the samples. Only two of the absorption features of Nd, centered at ~745 and ~810 nm, are prominent in the Nd-rich samples. The other absorption features are either weak or suppressed by the featureless spectra of the associated minerals. Similar absorption features are found in the VNIR and SWIR images of the rock samples captured by the laboratory-based hyperspectral cameras that are processed through Minimum Noise Fraction (MNF) and Fast Fourier Transform (FFT) to filter the signal and noise from the reflectance data. An RGB false-color composite of continuum-removed VNIR reflectance bands covering wavelengths of 587.5, 747.91, and 810.25 nm efficiently displayed the spatial distribution of Nd-rich hotspots in the hyperspectral image. The depth of the 810 nm absorption feature, which corresponds to the concentration of Nd in a pixel, is comparatively greater in these zones and is quantified using the proposed NI such that the deeper the absorption feature, the higher the NI. To quantify the Nd-rich pixels in the continuum-removed VNIR images, different threshold values of NI are introduced into a decision tree classifier which generates the number of pixels in each class. The strength of the proposed NI coupled with the decision tree classifier is further supported by the accuracy assessment of the classified images generating the Kappa coefficient of 0.82. Comparing the results of the remote sensing data obtained in this study with some of the previously published studies suggests that the Sillai Patti carbonatite is rich in Nd and associated REEs, with some parts of the samples as high in Nd concentration as 1000 ppm.

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“…Twenty-six major carbonatite complexes have been reported from the Indian subcontinent (Krishnamurthy, 2019; Paul et al , 2020; Randive and Meshram, 2020). Among these, the Cretaceous Amba Dongar, Gujarat; the Tertiary Sarnu-Dandali complex, Rajasthan and the Neoproterozoic Sevattur (also known as Sevathur) alkaline-carbonatite complex are known for the commercial mining of fluorite, REE and vermiculite, respectively (Viladkar and Subramanian, 1995; Palmer and Williams-Jones, 1996; Bhushan and Kumar, 2013; Bhushan, 2015).…”

Section: Introductionmentioning

confidence: 99%

Composition and genesis of albitite-hosted antecrystic pyrochlore from the Sevattur carbonatite complex, India

Dey

Mitchell

Bhattacharjee

et al. 2021

MinMag

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The Neoproterozoic Sevattur complex is composed essentially of calcite and dolomite carbonatites together with pyroxenites and diverse syenites. This work reports the compositions and paragenesis of different pyrochlore generations hosted by albitite veins in this complex. The pyrochlore are distinctive, being exceptionally rich in uranium (26 to 36 wt.% UO2). Five types of pyrochlore (Pcl-I to Pcl-V) are recognised on the basis of composition and texture. With the exception of Pcl-V, the majority of the pyrochlore (Pcl-II to Pcl-IV) are surrounded by a thick orbicular mantle of Ba-rich potassium feldspar. This mantle around Pcl-V is partially-broken. Pcl-I is restricted to the cores of crystals, and associated with Pcl-II and -III and is relatively rich in Nb (0.53–0.62 apfu) together with more A-site vacancies (0.37–0.71 apfu) compared to Pcl-II to Pcl-IV. Other pyrochlore (Pcl-II to Pcl-IV) are characterised by elevated Ca and Ti compared to Pcl-I, which are related to the (3Nb5+ + Na+ → 3Ti4+ + U4+) and (2Nb5+ → 2Ti4+ + Ca2+) substitutions, respectively. These substitutions represent replacement of Pcl-II to Pcl-IV. Alteration and Ba-enrichment in all the pyrochlore are marked by interaction with an externally-derived Ba-rich hydrothermal fluid following the (2Nb5+ → 2Ti4+ + Ba2+) substitution. This substitution, coupled with extensive metamictisation leads to the formation of Ba-rich (15.9–16.3 wt.% BaO) patchy-zoned Pcl-V. The orbicular mantles around Pcl-I to Pcl-IV have prevented extensive metamictisation and extensive secondary alteration compared to Pcl-V, where mantling is partially disrupted. The compositional and textural variation suggests that Pcl-II to Pcl-IV form by nucleation on Pcl-I, and are transported subsequently as antecrysts in the host albitite.

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An Overview of the Carbonatites from the Indian Subcontinent

Cited by 17 publications

References 115 publications

Mineralogy of Dolomite Carbonatites of Sevathur Complex, Tamil Nadu, India

Mineralogy of Dolomite Carbonatites of Sevathur Complex, Tamil Nadu, India

Detection and Relative Quantification of Neodymium in Sillai Patti Carbonatite Using Decision Tree Classification of the Hyperspectral Data

Composition and genesis of albitite-hosted antecrystic pyrochlore from the Sevattur carbonatite complex, India

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