Kaolin deposits at Melthonnakkal and Pallipuram within Trivandrum block, southern India

doi:10.1016/j.gr.2005.11.010

Gondwana Research

Volume 9, Issue 4, June 2006, Pages 530-538

https://doi.org/10.1016/j.gr.2005.11.010 Get rights and content

Abstract

The kaolin deposits at Melthonnakkal and Pallipuram mines form part of the Warkalli Formation belonging to the Tertiary sequence in southern Kerala and occur at the boundary between the Tertiary sequence and Precambrian granulite facies metapelites (khondalites). The sedimentary clays are composed mainly of kaolinite, quartz and gibbsite. XRD and SEM studies have revealed that kaolinite is well-crystallized variety and the platy crystals are scarcely broken in the sedimentary clays. These sedimentary kaolins are considered to have been formed by intense tropical weathering of the khondalites, and subsequently transported and deposited with high organic input into lakes near the weathering crust over the basement rock. Besides, the surficial parts of the sedimentary deposits are extensively lateritized with the formation of goethite and hematite by Quaternary tropical weathering processes.

Introduction

Clay deposits constitute one of the important mineral resources, with different types of clays formed under various environments and mined for a variety of applications. Among the important clay deposits in southern India, an integral fragment of the Gondwana supercontinent, a number of clay workings occur surrounding Trivandrum region in southern Kerala. The clays are mostly kaolin and other similar types such as bauxitic clay and dark plastic clay. These clays are considered to be products of tropical weathering. The occurrence of these clay deposits and their general mineralogical features are outlined by Soman (1997), Soman and Machado (1986), and Soman and Slukin (1987), although detailed studies have not yet been carried out. The industrial properties were studied by Chandrasekhar and Ramaswamy (2002), and compared to the kaolin from Kutch, Gujarat.

At Melthonnakkal and Pallipuram in the Trivandrum district, high quality kaolin is mined by the English Indian Clay Mine and Sulaikha Clay Mine, respectively. The kaolin has been designated as china clay and has been used mainly for white paper and sanitary wares. The results from field studies in both these mines and the mineral associations and the properties of kaolinite through laboratory investigations are reported in this paper, together with some genetic considerations.

Section snippets

Geology

Southern India comprises a collage of Proterozoic high grade metamorphic rocks of dominantly upper amphibolite to granulite grade which are welded onto an Archean craton in the north (Drury et al., 1984). The southern part of South India comprises a vast supracrustal sequence of granulites termed as the Kerala Khondalite Belt (Chacko et al., 1987) or the Trivandrum Granulite Block (Santosh, 1996). The major lithounits in this block are garnet–sillimanite–cordierite–spinel bearing aluminous

Lithology of the clay deposits

The Melthonnakkal clay mine is one of the largest kaolin deposits in India. The deposit is stratified nearly horizontally. Clayey sediments ca. 30 m thick belonging to the Warkalli Formation are exposed by open-cut mining. The top to bottom lithostratigraphic profile (Fig. 2a) shows the sequence: brownish laterite soil, lateritized sandy clay, clay containing graphite spots, white clay, sandy clay, carbonaceous clay and sandy clay. The white clay is massive and very fine grained with soapy

Analytical methods

Representative kaolin samples were collected from both the clay mines during field investigations. X-ray powder diffraction method was employed to characterize the constituent minerals of kaolin samples, employing a Rigaku Geigerflex 2038 diffractometer using CuKα radiation. The accessory minerals were concentrated by hand-picking or sedimentation method for the X-ray identification. Microscopic observations of thin sections of representative samples were performed. Morphology of kaolinite was

Microscopic observation

Under the microscope, quartz grains cemented with clayey material in sandy clay samples are angular and poorly sorted (Fig. 3). Quartz grains are fringed with ferruginous material in lateritized sandy clay. In general, quartz in the Pallipuram samples are of finer grain size than those in the Melthonnakkal samples, although sandy quartz of varying grain size occur in both deposits. Trace amounts of rutile, graphite, sillimanite and zircon are found in sandy clay and sandy laterite samples in

Discussion

Kaolin of the Melthonnakkal and Pallipuram mines are considered to be secondary (sedimentary) accumulations derived from weathered primary source. The process of formation of the deposits is schematically shown in Fig. 7 and summarized below.

Sedimentary and residual clays of the mines are mostly composed of kaolinite and quartz. The kaolin clay containing organic matter occurs in the mines. The top portions of the profiles are extensively lateritized. Graphite and sillimanite are contained in

Summary and conclusions

The Melthonnakkal and Pallipuram kaolin deposits occur at the boundary between the Tertiary Warkalli Formation and Precambrian aluminous granulites (khondalites) in the Trivandrum region. The deposits form part of the Warkalli Formation and the sedimentary kaolin clay sequences consist of pure kaolin clay, sandy clay, carbonaceous clay, etc. These clays are composed mainly of kaolinite and quartz. The quartz grains in the sandy clay are angular and poorly sorted. Trace amounts of graphite,

Acknowledgments

We are indebted to the staff of the English Indian Clay Mine and Sulaikha Clay Mine, particularly Dr. P. T. Ambujakshan and Mr. H. Thampy for all their help and guidance in the field. We also thank the staff of Gondwana Research Trivandrum office for their kind help. Thanks are due also to Assoc. Prof. M. Iwai of Kochi University for his help on SEM observation.

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GR LetterKaolin deposits at Melthonnakkal and Pallipuram within Trivandrum block, southern India

Abstract

Introduction

Section snippets

Geology

Lithology of the clay deposits

Analytical methods

Microscopic observation

Discussion

Summary and conclusions

Acknowledgments

Applied Clay Science

Gondwana Research

Gondwana Research

Chemical Geology

The genesis of the china clays of South-West England — a multistage story

Metamorphic P–T conditions of the Kerala (South India) Khondalite Belt, a granulite facies supracrustal terrain

Journal of Geology

Precambrian tectonics and crustal evolution in South India

Journal of Geology

GR Letter
Kaolin deposits at Melthonnakkal and Pallipuram within Trivandrum block, southern India