CLAY MINERALS IN INDIAN SOILS in soil Minerology

CLAY MINERALS IN INDIAN SOILS in soil Minerology

1. Topic : “CLAY MINERALS IN INDIAN SOILS ” SAC 504 soil minerology 1

2. CONTENTS Introduction – Clay minerals Clay minerology of Benchmark Soils The critical evaluation of the nature and distribution of naturally occuring c lay minerals in the soils of.., Deccan basalt Peninsular Gneiss Quaternary deposits Weathering sequence for the formation of Kaolinite Carbonates , G ypsum , G ibbsite and Zeolites in Soils of India. Layer silicate clay minerals in the Indian soils . Soil orders – Dominant clay minerals

3. Clay Minerals Clay minerals are layer silicates that are formed usually as products of chemical weathering of the other silicate minerals at the earth surface. They are found most often in shales – most common type of sedimentary rock. Feldspar + water Clay mineral + cations + anions + soluble silica Most commonly forming secondary minerals, That form illite , montmorillonite , chlorite, vermiculite & kaolinite. Inorganic crystalline minerals(<2microns). Variable in color Negative electrical charge Swelling in soil moisture condition. INTRODUCTION

4. Feldspars to clay + H 2 CO 3 (acid)

5. Clay Mineralogy of Benchmark Soils

6. I. Clay Minerals In Deccan Basalt Deccan basalt – 5,00,000 squares of km . W eathering of basalt - fine textured black soils B elonging to Ustorth ent s , Ustochr ept , Pellust ert s , Chromust ert s and Pellud ert . Basalt yields S mectite clay as first weathering product as detected in the Clay fractions of weathering rinds of Spheroidally weathered Basalt . Basalts composed dominantly of plagioclase and pyroxene with some accessory minerals like magnetite, ilmenite , volcanic glass and Palagonite .

7. Deccan basalt can not account for the presence of all the mineral identified in the sand, silt and clay fractions. Presence of mica, K- feldspars, rutile and zircon in few Vertisols suggest that they are formed in alluvium of weathering Deccan basalts and other rock formations, transported downstream. Addition of minerals in Vertisols from rock other than basalt is quite likely during erosional & depositional episodes.

8. II. Clay minerals in soils of Peninsular Gneiss These rock have, in general, given rise to fairly well weathered ferruginous soils in semi arid, sub-humid and humid climates in the state of AP , MP , OS, TN, KA, KL & WB. These soils occur as Paleustalfs , Rhodustalf , Haplustalf , Plinthaquults , Plinthustults , and Plinthudults .

9. Mineralogy of associated red and black soils Soil topo sequences with ferruginous soils on the slopes and black soils in depressions occur. F erruginous soils of such associations are classified a Ustorthents in semi-arid climate. In Black soil type clay fraction is dominated by S mectitic mineral In Ferruginous soils dominated by interstratified Smectite -Kaolin ( Sm /K) mineral .

10. Ferruginous soils ( Ustalfs ) developed in humid climate on basalt and dominated by kaolinite and/or gibbsite -very rare. Enriched with interstratified Sm /K - kaolin portion is the most dominant. Kaolinite often end product in such transformation is not detected Its absence has been attributed to the incomplete leaching of base due to the presence of zeolites that prevented its formation from smectite . Even under prolonged weathering in tropical humid climate since the Upper-Cretaceous to the present the pedogenesis of ferruginous soils ( Ustalfs ) has not resulted in the formation of kaolinite and/or gibbsite. This is in contrast to kaolinitic ferruginous soils ( Ustalfs ) developed on Peninsular gneiss of Mysore plateau during the Upper~Cretaceous to Plio -Pleistocene transition period.

11. III. Clay minerals in soils of Quaternary deposits Alluvial soil in deposits of the Indus, Ganga and Brahmaputra and their tributaries need a special mention. 600,000 sq.km. Haplaquents , Ustifluvents , Udifluvents , Haplustaljs , Natrustaljs and Ustochrepts in the vast areas of Punjab, Haryana, Uttar Pradesh, Bihar, Rajasthan and West Bengal . Mica, Vermiculite , S mectite , mixed-layer minerals, Chlorite and Kaolinite Soils in Quaternary deposits of the Sub-Himalayan region of Jammu and Kashmir, and Himachal Pradesh belong to Haplustalf , Hapludalfs , Haplaquepts , Eutrochrepts , Hapludalf , Paleudalfs , and Haplohumults .

12. In these soils of semi-arid to per humid climates vermiculite and smectite minerals are the weathering products of biotite mica through a 1.0-1.4 nm mixed-layer phase. Intrastratified minerals --- mica- smectite -chlorite, mica-vermiculite-chlorite and kaolinite smectite Mica- Smectite -Chlorite associated with pedogenesis in alkaline conditions, Kaolinite-Smectite with acidic soil conditions. . In acid soils of North Eastern states, Vermiculite acts a Al 3+ sink ( Alumination ) .

13. The primary rock mineral undergo hydrolysis  Releasing monomeric form of silica , aluminum and iron ; iron precipitates first, followed by co precipitation of Fe & Al as a gel occluding islands of hydrous iron oxides; further leaching of bases from the weathering zone lead to acidic conditions Under acidic conditions, gel crystallizes into kaolinite and incorporate part of the Fe in octahedral sheet. not valid for all ferruginous soils V. Sequence of weathering for the formation of Kaolinite

14. Under acidic weathering environment in humid climate smectite /kaolin interstratification is an important ephemeral stage during the transformation of smectite ( montmorillonite ) to kaolinite. @ Initial stage, smectite dominates over kaolin in the total Sm /K interstratified mineral With depth the proportion of kaolin increases Smectite ( montmorillonite ) Chloritized smectite - kaolin ( SmlK =33:67)* Chloritized smectite -kaolin ( SmlK = 16: 4) Kaolin (100)**

15. V. Calcium Carbonates in soils Calcium carbonate (CaCO 3 ) is a very common soil mineral in dry (sub humid to arid) regions of the country. Formation of CaCO3 in soils is an important pedogenic process in many arid and semi-arid parts of the Indian subcontinent. Occurance is in agro ecological sub regions indicates presence of CaCO3 in humid & per humid regions also. Its presence in soils of humid climatic region is considered mostly as inherited material in soils developed in strongly calcareous parent materials , usually on younger geomorphic surfaces.

16. Gypsum in soils: Gypsum (CaSO 4 .2H 2 O) is relatively common soil mineral in soils of arid and semi-arid climates and by far the dominant form of CaSO 4 in soil Frequently found in a horizon situated somewhat beneath the horizon in which CaCO 3 is accumulated. It sometimes occurs as Indurated horizons and a Crystal Disseminated in surface soil horizons. It is not only found in soils of hot arid and cold arid climates but also in sub soils of humid regions , however, a weathering product of pyrite (FeS2)' Its presence in shrink swell soil of TN and KA has been reported.

17. Gibbsite in soils: In Oxisols of humid tropical climates gibbsite is one of the major minerals. It is also a common mineral but found in lower contents in many Ultisols of humid tropical, subtropical and temperate region. The presence of gibbsite in soils need not be considered as a signature of extreme weathering conditions of soils. There are two different views regarding the genesis of gibbsite in tropical acid soils namely Direct weathering of primary Al-silicate mineral, Transformation through clay mineral intermediate . Cannot be formed until all the expansible 2: 1 clay minerals are decomposed.

18. Predominant soil orders in India and their distribution. Source: Adapted from Srinivasa Rao et al. (2013)

19. Zeolites in Indian soils Constituents of Cenozoic volcanogenic Sedimentary rocks and altered pyroclasic rocks. Zeolite have also been reported as secondary minerals in the Deccan basalt of the Western Ghats in Maharashtra. Present in the sand, silt and clay of red and black soil of the Western Ghats of Maharashtra .

20. Alluvial soils Dominant (50-60 %) clay mineral – Illite – Others like Kaolinite , Chlorite & Smectite . Some old alluvium soils – Smectite Black soils Dominant clay minerals (70-80%)- Smectite group – Others like Illite & Kaolinite . Red & Lateritic soils Dominant clay minerals (70-80%) Kaolinite – Others like Illite , kaolinite-smectite mixed layer minerals & Smectite . VI. Layer silicate clay minerals in the Indian soils.

21. Alfisol - Kaolinite and M ontmorillonite as dominant clay minerals and quartz as an accessory mineral. ( Zhang et al., 2016 ) Sepiolite and P alygorskite  have been reported in Aridisols by Kodama et al ., 2014 Andisols -  Allophane , imogolite , ferrihydrite , and halloysite . Randy  et al ., 2017 . Mollisols - Smectite and illite , with occasional small amounts of K aolinite, Illite , vermiculite, smectite , chlorite, and interstratified clay minerals are found in podzolic soils. Vii.Based on soil orders dominant clay minerals

22. Histosols  are soils that consist of dominantly organic soil materials, they have high contents of smectite  clay mineral . O xisols soil order consists of 1:1 clay minerals (kaolinite) and Fe and Al oxy-hydroxides , ( Iron and Al uminium clays) such as G ibbsite, Hematite and Goethite (Schaefer et al., 2008 ) Ultisol - The well-developed, extensively leached soil horizons are enriched in kaolin -group clay minerals and metal oxides appear as red or bleached layers . Gellisols - Dominantly they have high contents of smectite and ve rmiculite   clay mineral .

23. Spodosols - D ominated by vermiculite and vermiculite- illite interstratified minerals, and they have minor kaolinite, quartz and gibbsite. No hydroxy interlayered vermiculite (HIV) was found in the E horizon .   ( Ching -Wei Lin et al 2002) Poorly crystalline Kaolinite and H alloysite are the dominant clay minerals Entisols Graham et al .( 1988). Inceptisol generally dominated by  smectite clay minerals and some kaolinite  and it was derived from clay sediment main material  Enriched with either silicate clay or with an amorphous mixture of aluminum and organic carbon

24. Major soils of India and their equivalent US soil Taxonomy and general distribution of clay minerals

25. CONCLUSION Here we have seen the critical evaluation of clay minerals in Indian soils in response to major soils and major agro ecological regions & weathering sequence of formation of Kaolinite clay minerals. Along with clay minerology of Benchmark soils.