ISSN IJAEES (2015) Vol.3, No.1, 1-5 Research Article International Journal of Advancement in Earth and Environmental Sciences

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(4000-2500NM): A CASE STUDY IN AND AROUND ASKOT BASEMETAL MINERALIZATION OF KUMAON HIMALAYA, INDIA H. Govil Department of Geology, Aligarh Muslim University, Aligarh, India (himgeo@gmail.

1 ISSN IJAEES (2015) Vol.3, No.1, 1-5 Research Article International Journal of Advancement in Earth and Environmental Sciences SPECTRAL REFLECTANCE OF THE HYDROTHERMALLY ALTERED MINERALS IN THE VISIBLE AND NEAR INFRARED PORTION ( NM): A CASE STUDY IN AND AROUND ASKOT BASEMETAL MINERALIZATION OF KUMAON HIMALAYA, INDIA H. Govil Department of Geology, Aligarh Muslim University, Aligarh, India (himgeo@gmail.com) ABSTRACT: Spectroscopy in the visible and infrared portion of the electromagnetic spectrum offers a rapid, inexpensive technique for identification of different altered/weathered/clay minerals. The shape and position of the spectral absorption features of the different minerals, available in the visible and infrared portion ( micron) helps in the identification of different materials. In this study different altered, weathered and clay minerals in the crystallines rocks near the Askot basemetal mineralization have been identified using the visible and near infrared portion of the electromagnetic spectrum. Different altered, weathered and clay minerals like goethite, clinochlore, muscovite, illite, and montmorillonite have been identified with the help of spectroscopy analysis of the rock samples collected from the field during field visit. The mineralogy identified in this area has also been confirmed with other conventional methods of the mineral identification and the results are in good confirmation with the established geology of this area and confirm the large scale hydrothermal activity in this region. KEYWORDS: Spectroscopy, altered minerals, hydrothermal alteration, clay minerals INTRODUCTION: Imaging spectroscopy, in the recent years, has gained an enormous success for mineral identification and mapping. Spectroscopy is the application of the reflectance and/or emittance spectra of each and every material available on the earth surface either by the airborne or space borne sensor or by using the spectroradiometer instrument on the ground (1). Spectroscopy can be used in the solid, liquid and gas to detect individual absorption features due to the specific chemical bonds (1). Each and every material available on the earth surface is formed by different chemical bonds and can be detected either by reflectance or emittance spectroscopy. Detection of the spectral reflectance (plots of reflectance versus wavelength) of any material through spectroscopy is dependent mainly on three factors: spectral coverage of the spectroradiometer, spectral resolution and the most important signal-to-noise ratio of the instrument. Abundance of material also affects the depth of the absorption feature (2). Spectral reflectance properties of the altered/weathered minerals in the visible and near infrared ( nm) portion of the electromagnetic spectrum play an important role for identification of the different minerals like calcite and dolomite etc. Spectroscopy also offers a rapid, inexpensive technique for identification of the major as well as the minor amount of other minerals available as a mixture in the altered rocks. This is the only technique available today, which can be used in the field as well as in the laboratory and in any form of sample (powered, sawed, broken, polished etc.). But when spectroscopy is used in the day light, OH and HOH absorption features cannot be recognized due to the water absorption region at 1400nm and 1900nm.

2 Govil, H. / International Journal of Advancement in Earth and Environmental Sciences, Vol.3, No. 1 2 Visible and near infrared spectra of the hydrothermally altered rocks indicate that the individual and mixture of the different altered minerals can be identified using spectroscopy technique (3-5). Physical and chemical changes caused by the hydrothermal alteration can be detected in the infrared with the help of OH bond fundamental stretch and Al-O-H fundamental bending (6). Fluid inclusion in the carbonate minerals can also be identified by the H-O-H absorption features near 1900nm (7). This technique has been used to identify the different minerals like kaolinite-serpentines, smectites, chlorites (8), muscovite and talc (9) pyroxens, olivines and feldspar (1, 10) and carbonates (7). Askot basemetal mineralization of Kumaon Himalaya is significant due to the economic potential occurrence in the altered rocks. Sulfide of gold, silver, copper, lead and zinc have also been found previously in this region of the Himalaya. The basemetals in this area are found in the altered rock of the crystallines of Kumaon Himalaya. A large scale hydrothermal activity has been observed in this area due to the tectonic activity held in the past (11), which makes this region suitable for the hydrothermal alteration studies. The aim of this study is to identify different altered/weathered minerals available in and around the Askot basemetal mineralization using imaging spectroscopy. The study also aimed to analyze the diagnostic absorption features responsible for different minerals and alteration types responsible for the alteration in that area with the help of the spectral analysis results. This is the first spectroscopic overview of the altered/weathered minerals available in and around Askot basemetal mineralization of Kumaon Himalaya. 2. STUDY AREA: Crystallines are the most prominent rock types occurring in and around the Askot basemetal mineralization of Askot area, Kumaon Himalaya. These crystallines are locally named as Askot crystallines. Origins of the crystallines are debatable. One group of researchers consider these crystallines autochthonous in nature (12, 13) and other believe that they are the remnant of the Central Axial Crystallines Zone which were pushed forward due to orogenic movement (14, 15). Fig.I. Geology map of the study area with mineral locations The dominant rock types in this area include augen gneiss, granite gneiss, garnetiferous-biotite gneiss, biotite-muscovite gneiss, calcsilicates and quartzites. Dikes of aplites and pegmatites are common in the rocks of higher (northern) horizons of this zone. The major rock types are gneisses, quartzites, variety of schists, calcsilicates, and leucogranite dikes especially at higher (northern) horizons (16). Fig.I shows the geological map of the study area along the field location of the samples.

3 Govil, H. / International Journal of Advancement in Earth and Environmental Sciences, Vol.3, No INSTRUMENT USED: In order to measure the surface reflectance of the altered/weathered samples collected from the field, Field Spec 4 spectroradiometer was used in the laboratory of Indian Agriculture Research Institute, New Delhi, India. This is a portable instrument consisting the three units: fiber optics probe gun/contact probe, spectroradiometer and computer interface. This instrument has two integrated spectroradiometer coving the spectral range of 350 to 2500nm. The specifications of the Field Spec 4 are given in table I. Spectral Range nm Spectral Resolution nm /2100 nm Sampling Interval nm nm Scanning Time 100 milliseconds Channels 2151 Detectors VNIR detector ( nm): 512 element silicon array SWIR 1 detector ( nm): Graded Index InGaAs Photodiode, TE Cooled SWIR 2 detector ( nm): Graded Index InGaAs Photodiode, TE Cooled Input 1.5 m fiber optic (25 field of view) Calibrations Wavelength, absolute reflectance, radiance*, irradiance*. All calibrations are NIST traceable. (*radiometric calibrations are optional) Table: I: Field Spec 4 Specifications Source: During this study contact probe and fiber optics gun were used for geological sample analysis in the laboratory as well as in the field. Averages of the 10 samples were considered for better accuracy. Samples collected from the Field Spec 4 were post-processed with the help of view spec pro software for reflectance conversion. 4. RESULTS: Fig.IIa shows the Goethite spectral signature taken from the samples collected from the gossanised zone above the Askot basemetal mineralization. Goethite: Goethite ((Fe+3O(OH)) is an iron oxide mineral crystallize in the orthorhombic system and comes under the Dispore group of minerals. Goethite shows an absorption feature at 0.9-µm and 0.86-µm absorption features due to Laporte-forbidden transitions (17). This is a pure Goethite spectra and does not contain any spectral mixing in the SWIR region. In general, Goethite spectral signatures can be identified in the VNIR region and SWIR region show the mixing of the other minerals. Fig. IIb shows the spectra taken to the near to the mining area of Askot basemetal mineralization site. The VNIR region shows the spectral signatures of Goethite mineral while the SWIR region shows the presence of muscovite. Muscovite (KAl 2 (Si 3 Al)O 10 (OH,F) 2 ) is a phyllosilicate, comes under the mica group of minerals and crystallizes in the monoclinic system. Diagnostic absorption feature of muscovite occurs between nm is due to the compositional difference in the Al content of muscovite. Some other absorption features are also found at 1413nm and 1905nm due to the OH stretching and H-O-H overtones respectively. Fig.IIc shows the all the diagnostic absorption features of muscovite mineral without any without any mixing. Fig.IId shows the spectral signature of the Clinochlore mineral. Clinochlore ((Mg, Fe ++ ) 5 Al(Si 3 Al)O 10 (OH) 8 ) is a phyllosilicate, comes under the category of Chlorite group and crystallize in the monoclinic system. Clinochlore is a SWIR active mineral and shows diagnostic absorption features at 2255nm and nm, which is due to the presence of AlFe-OH or AlMg-OH and MgOH vibrational process (8). OH and HOH absorption feature occur at 1400 and 1900nm. Fig.IIe illustrates the spectral signature of the illite mineral. Illite ((K, H3O) (Al, Mg, Fe) 2 (Si, Al) 4 O 10 [(OH) 2,(H 2 O)]) is a phyllosilicate and comes under the Illite group and crystallizes in the monoclinic system. Illite is a short wave infrared (SWIR) active mineral and shows a distinct absorption feature at 2205 nm,

4 Govil, H. / International Journal of Advancement in Earth and Environmental Sciences, Vol.3, No. 1 4 which is due to the vibrational absorption feature of AlOH presence in the mineral (1). Two other absorption features are also available at 2345 nm and 2440 nm due to the same molecule. Fig.IIf depicting the montmorillonite mineral occurred at the outer fringes of the Askot basemetal mineralization. Montmorillonite (Na,Ca)0,3(Al,Mg)2Si4O10(OH)2 n(h2o) comes under the Smectite group and crystallizes in the monoclinic system. It shows diagnostic absorption feature at 2200nm along with the OH and HOH absorption features at 1400 and 1900nm. (a) (b) (c) (d) (e) (f) Fig.II: Spectral signature of the samples collected around Askot basemetal mineralization (a) Goethite (b) Goethite and Muscovite mixture (c) Muscovite (d) Clinochlore and Muscovite Mixture (e) Illite (f) Montmorillonite and Illite mixture 5. DISCUSSION AND CONCLUSION: XRD and thin section studies are the two conventional methods for identification of altered/weathered and clay minerals. Though clay minerals are not easy to identify in thin sections and altered and weathered rock samples need proper care during sample preparation. Muscovite mineral can be easily identified in the thin section as well as in the XRD (X-ray diffraction) but the other minerals viz. goethite, clinochlore, illite and montmorillonite need special treatment for the XRD analysis and are typical to identify in the thin section analysis. Spectral analysis of the rock samples open a new quick identification method for altered/ weathered and clay minerals without any sample preparation in the field as well as in the laboratory.

5 Govil, H. / International Journal of Advancement in Earth and Environmental Sciences, Vol.3, No. 1 5 Reflectance spectral signatures recorded from the rock samples collected from the field have been analyzed for the identification of different altered/weathered and clay minerals. On the basis of the mineralogy identified with the aid of ASD spectroradiometer, it can be concluded that this area has experienced intense hydrothermal activity in the past. Mineralogy identified in this area indicates the sericitic argillic and propylitic alteration in this region, which was in good confirmation with the previous workers (2, 11). Spectroscopy has been found suitable technique for identification of hydrothermally altered/weathered and clay minerals in the laboratory as well as in the field in and around Askot basemetal mineralization in Kumaon Himalaya, India. VNIR and SWIR regions of electromagnetic spectrum ( nm) have been found suitable for identification of altered/weathered and clay minerals. Goethite mineral has been proven again as an important guide in identification of different ore minerals. ACKNOWLEDGEMENT: I acknowledge the contribution of Mr. Prashant Kawisher, Mr. Gautam Ghosh and Dr. R. N. Sahoo for this study. This work was funded by Natural Resource Data Management System (NRDMS), Department of Science and Technology (DST), India through grant no. NRDMS/11/1669/10/Pr: 9. REFERENCES: 1. Clark, R. N.,1999, Spectroscopy of Rocks and Minerals, and Principles of SpectroscopyJohn Wiley and Sons, Inc p, Govil, H., 2014, Identification of hydrothermally altered assemblages and gossans in parts of Kumaon Himalaya using hyperspectral data: implications for mineral exploration, Geology,Aligarh Muslim University Aligarh, 3. Hunt, G. R., Salisbury, J. W. and Lenhof, C. J., 1971, Spectra of altered rocks in the visible and near infrared, Economic Geology, no. 74, p Hunt, G. R., 1979, Near infrared ( µm) spectra of alteration minerals: potential of use in remot sensing Geophysics, vol. 44, p Hunt, G. R., 1979, Near-infrared spectra of alteration minerals - potential for use in remote sensing Geophysics, no. 44, p Hunt, G. R. and Ashley, R. P., 1979, Spectra of altered rocks in the visible and near infrared, Economic Geology, no. 74, p Gaffey, S. J., 1986, Spectral reflectance of carbonate minerals in the visible and near infrared ( microns): calcite, aragonite and dolomite, American Mineralogist, vol. 71, p Bishop, J. L., Lane, M. D., Dyar, M. D. and Brown, A. J., 2008, Reflectance and emission spectroscopy study of four groups of phyllosilicates: smectites, kaolinite-serpentines, chlorites and micas, Clay Minerals, no. 43, p Farooq, S. and Govil, H., 2013, Mapping Regolith and Gossan for Mineral Exploration in the Eastern Kumaon Himalaya, India using hyperion data and object oriented image classification, Advances in Space Research, vol. 53, no. 12, p Adams, J. B., 1974, Visible and near infrared diffuse reflectance spectra of pyroxenes as applied to remote sensing of solid objects in the solar system, Journal of Geophysical Research, vol. 79, p Farooq, S., 1985, Basemetal Mineralization in Askote Area, Pithoragarh Distt., Kumaon Himalaya, Geology,Aligarh Muslim Univeristy Aligarh, 12. Bhattacharya, A. R., 1980, New light on the stratigraphy and structure of the Kumaon lesser Himalaya: A study in mathmatical perspective, Structural geology of the Himalaya, Today and Tomorrow's Printers & Publishers, 13. Misra, R. C. and Sharma, R., 1972, Structure of Almora Crystallines, Lesser Kumaon Himalaya: An interpretation., Himalayan Geology, vol. 2, p Gansser, A., 1964, Geology of the Himalayas, Intersci. Pub., p Heim, A. and Gansser, A., 1939, Central Himalaya, geological observations of the Swiss expendition 1936, Mem. Soc. Helv. Sci. Nat, vol. 73, no. 1, p Bhattacharya, A. R., 2008, Basement Rocks of the Kumaun - Garhwal Himalaya: Implications for Himalayan Tectonics, Earth Science India, vol. 1, no. 1, p Morris, R. V., H.V. Lauer, C.A. Lawson, E.K. Jr. Gibson, G.A. Nace and Stewart, C., 1985, Spectral and other physiochemical properties of submicron powders of hematite (-Fe2O3), maghemite (-Fe2O3), maghemite (Fe3O4), goethite (-FeOOH), and lepidochrosite (-FeOOH), J. Geophys. Res, no. 90, p

ISSN IJARSGG (2015) Vol.3, No.1, 1-8 Research Article International Journal of Advancement in Remote Sensing, GIS and Geography

ISSN IJARSGG (2015) Vol.3, No.1, 1-8 Research Article International Journal of Advancement in Remote Sensing, GIS and Geography ISSN 2321 835 IJARSGG (2015) Vol.3, No.1, 1-8 Research Article International Journal of Advancement in Remote Sensing, GIS and Geography IDENTIFICATION AND MAPPING OF HYDROTHERMALLY ALTERED MINERALS IN