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CRITERIA FOR ASSESSMENT OF RECOVERY PERCENTAGE OF COMMERCIAL GRANITES IN RESPECT OF MAJOR MUTI-COLOURED GRANITE BELTS OF TAMILNADU, INDIA.

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CRITERIA FOR ASSESSMENT OF RECOVERY PERCENTAGE OF COMMERCIAL GRANITES IN RESPECT OF MAJOR MUTI-COLOURED GRANITE BELTS OF TAMILNADU,INDIA By B.KANISHKAN Director(Rtd) Geological Survey of India Dt: 19-04-2013

Focus:

Focus To discuss on various technical and environmental problems To establish a logical link between sound geological knowledge and successful exploitation To suggest optimum utilization of waste generated. To establish a logical link between sound geological knowledge and scientific assessment of recovery percentage of a granite deposit/quarries. Focus

BACKGROUND INFORMATION :

BACKGROUND INFORMATION Assessment of recovery percentage of commercial granites is the hot topic of the day especially for the Revenue/Mineral administrators of the State of TamilNadu. Considering the complexity of the problem the topic has been chosen to highlight the importance of the Geological inputs that are essential in resolving the issue. Geological Survey of India (GSI) being a premier organization having its main stake on Geological Mapping in identifying the various economic minerals for the economic development of the country since 1851 ,commenced its maiden survey for the Granite occurrences in Melur belt, Madurai district, TamilNadu during the year 1993.

BACKGROUND INFORMATION:

BACKGROUND INFORMATION Encouraged by the results of the survey, GSI launched a National survey for this commodity and now has a rich data base of various resources of granite spread across the Country. Paper highlights the methods for assessment of Recovery percentage in a granite deposit/ quarry and in specific to the major multi-colored granite belts of TamilNadu. Viz. Melur, Madurai district and Krishnagiri.

Criteria for Assessment of Recovery percentage :

Criteria for Assessment of Recovery percentage Recovery percentage of a Granite deposit/quarry is based mainly on Marketing and Geological considerations besides on methods of operation of a quarry. Aesthetic sense of the Buyer for a particular colour and fabric of the deposit besides recovery and size of blocks. Structural stability of the formation which ultimately restricts the export size of blocks

METHODS:

METHODS No standard norms like ISI standards available for assessment of recovery percentage of any granite deposit/quarry. Scientific method is to prepare the geological map of each deposit/quarry with background knowledge of quarrying and marketing considerations. Each deposit/quarry to be examined with an expert in this field to bring out its petrological and structural variations.

CAUTION:

CAUTION Each quarry is unique in its occurrence and hence one should not presume that a quarry lying adjacent to a successful quarry need to be the same and may be either good or bad due to the variations mentioned above. Any method to compute uniform percentage of Recovery Percentage for the entire belt lacks not only scientific tenor but also not tenable.

Marketing Criteria:

Marketing Criteria Market for a granite variety is of paramount importance for the success of any quarry. Barring that it can be considered only as a building stone for local use. Buyers’ preference is for the pleasing colours, design and its uniformity in the formation. Recent trend is mostly for yellow, white, brown, blue and black colours

Marketing Criteria:

Marketing Criteria In yellow most wanted is for gold or yellowish white/ light pink. Gold/yellow colour in a white quarry is nothing but secondary attrition/coating due to weathering or rusting of garnets/magnetite. In early nineties, the rusting of garnets in Leptynite formation in Melur belt was considered as rejects. uniformity of sheet rock with same colour, texture and gneissosity (design) are considered essential for export market .

Marketing Criteria:

Marketing Criteria Considering the overall market trend and demand, one can visualize the recovery percentage of those deposits/quarries to make it viable for economic operation.

Geological Criteria:

Geological Criteria Success and failure of a granite quarry operation duly after satisfying the market considerations is decided later mainly by the Geological criteria. Which requires in depth knowledge in structural mapping and its application in commercial granite exploitation. Failure to understand the nature of the formation is like a major catastrophe of an earthquake for the Investors .

Geological Criteria:

Geological Criteria Geological mapping in a granite quarry/ belt with regional geological in puts like regional shear/ lineament associated with later alkaline/granite activity in a particular belt ultimately decides on the recovery percentage and success and failure of a quarry, which has to be understood before making any investment for its exploitation.

BASIC REQUIREMENT OF GEOLOGIST IN ASSESSING THE RECOVERY PERCENTAGE OF A GRANITE DEPOSIT/QUARRY:

BASIC REQUIREMENT OF GEOLOGIST IN ASSESSING THE RECOVERY PERCENTAGE OF A GRANITE DEPOSIT/QUARRY Sound geological/structural mapping knowledge particularly in a hard rock terrain. Background knowledge on market trend and requirements. Background knowledge on working of a granite quarry. Lastly,theoretical knowledge without practical experience/ application can not do any justice for this specialised work.

Geological Criteria-Regional Geology-A first step forward:

Geological Criteria-Regional Geology-A first step forward Regional Geology plays a major role in success and failure of a deposit/quarry. Imprints of regional disturbances/ major tectonic zones are well preserved on a micro-level in each of the deposits/quarries. Signatures of such disturbances have to be studied carefully before making an assessment. The role of a field Geologist becomes very important at this juncture .

Regional Geology:

Regional Geology

Geological structures:

Geological structures Rocks in general have undergone more than one phase of deformations and accordingly exhibit a variety of geological structures which have a definite bearing on the degree of commercial exploitation.

Structural aspects:

Structural aspects Critical study of the structural stability of the deposit is of paramount importance in determining the success of quarry operations vis-a vis its recovery percentage. Major failures in granite quarry operations may be attributed to the structural instability of the sheet formation to produce defect free gang saw size rough blocks. Sheet rock should be more or less uniform without shear cracks and to exhibit uniform design and colours and less of inclusions

Structural aspects:

Structural aspects Geological structures that are applicable to granite quarry operations can be grouped under: Favourable Structures. Unfavourable Structures. Disastrous Structures .

Favourable Geological Structures:

Favourable Geological Structures Facilitate easy recovery of blocks of desired export sizes with minimum usage of men, material and machinery forces. Presence of such favourable structures viz. sheet joints; vertical joints; steep dipping foliation planes; migmatitic structures etc. enhance the recovery percentage in quarry operation Value addition by way of production of big gang saw sized blocks.

Favourable Geological Structures:

Favourable Geological Structures

Favourable Geological Structures:

Favourable Geological Structures

Steep Dipping Foliation Planes :

Steep Dipping Foliation Planes Natural weak planes help in smooth splitting of blocks. If the vertical splitting mechanism synchronises with the foliation plane of the rock, the advantages are: Avoids wrong cutting to spoil the beauty of the finished product viz. slabs/ tiles. Enhances the durability of the slab and tile. In the case of black galaxy deposit, Ongole, AP; the galaxy (bronzite) is exposed mainly along the foliation plane and hence rock splitting should be oriented along that plane only.

Unfavourable Geological Structures:

Unfavourable Geological Structures Unfavourable geological structures are: Close spaced vertical/oblique joints, minor faults, silickensides, hair line fractures; low dipping foliation planes etc. Presence have an adverse effect on quarrying and ultimately restrict the size of the blocks. Though harmful to export market, may allow some blocks of smaller dimension especially in high value Kunnam black granite deposit and black galaxy deposit, Ongole. Smaller blocks of jet black granite can be utilised for processing UK monuments besides accessory items for Japanese monuments.

Unfavourable Geological Structures:

Unfavourable Geological Structures

Close Spaced Joints:

Close Spaced Joints Presence of close spaced joints of both vertical and inclined restrict the size and shape of the boulders By critical study of joint pattern vis-à-vis the size, shape and weathering pattern of the boulders especially in a dyke rock, one can visualise the nature and quality of the sheet rock occurring beneath. Accuracy in such analysis will facilitate preparation of a feasibility report for exploitation of granite deposit. In certain cases, the close spaced vertical joints as seen in some black granite quarries of Chamrajnagar, Karnataka, persist deep into the sheet rock and hence the recovery of blocks are restricted to monument size(>0.25 CBM) blocks.

Close Spaced Joints:

Close Spaced Joints

Minor Faults:

Minor Faults Frequently intercepted in black granite dykes and exhibit a dextral and sinistral pattern along its ‘Run’ By carrying out strike mapping with a tape and compass the structural disposition of the dyke can be brought out. Surface expressions: Boulders of cobble (uneven) sizes. Odd shaped sheared boulders showing deep weathering Dextral and Sinstral shifts at closer intervals. Development of secondary features like hairline fractures, silickensides, quartz and pyrite specks; white moles of quartz and feldspar etc.,seen mainly along fault planes.

FAULTS ALONG DYKE:

FAULTS ALONG DYKE

Low dipping Foliation Plane:

Low dipping Foliation Plane Recovery and the size of the blocks are reduced considerably Further, while processing for tiles and slabs, the material quarried from such low dipping formations generally yield a poor recovery besides a low durability strength.

Thiruthangal Quarry, Virudhunagar Dt. TamilNadu:

Thiruthangal Quarry, Virudhunagar Dt. TamilNadu

Low dipping Foliation Plane:

Low dipping Foliation Plane

Low dipping Foliation Plane:

Low dipping Foliation Plane

Folds:

Folds Major fold structures are common in multi-coloured granite deposits. In such case, quarrying along limb portions may be safer than nosal portion, since the fracture cleavages restrict the recovery and size of the blocks.. Sira Grey granite occurrence in Tumkur district, Karnataka is a linear deposit and the fine grained grey granite band exhibits, warping and swerving along its length. Therefore, the quarries opened within such kink portions exhibit criss-cross veination of pegmatite and hence the quarry operations are to be suspended for low recovery.

Shear Cracks:

Shear Cracks Shear cracks are normally noticed within the structurally disturbed zones. Effects of minor shears in a granite deposit is manifested in the form of thin and linear nerve like fractures cross-cutting the formation which are harmful to quarry operations. Restrict both size and recovery of blocks.

Disastrous Geological Structures:

Disastrous Geological Structures Harmful in totality in granite operations. These structures are of regional phenomena like the lineament zone, major shear zone, suture zone, active fault zone etc. Granite deposits including the dykes emplaced earlier to the tectonic activity are badly affected. Such deposits are not suitable for exploitation and in certain cases, it is difficult even to retrieve blocks of cobble sizes.

Disastrous Geological Structures:

Disastrous Geological Structures

Sheared Dyke:

Sheared Dyke

PowerPoint Presentation:

Structural stability of the granite body decides on the recovery, size and scope of the prospect

Assessment of Recovery percentage in major granite belts of TamilNadu:

Assessment of Recovery percentage in major granite belts of TamilNadu I. Paradiso Granite Deposit,Krishnagiri, TamilNadu

GEOLOGY OF THE AREA:

GEOLOGY OF THE AREA Paradiso granite variety is nothing but a medium to fine grained pink and grey migmatite. The deposit occurs between Soolamalai – Chendrapalli – Jagadevipalayam villages in the north and Jainur – Aleripattai – Sivampatti villages in the south.

GEOLOGY OF THE AREA:

GEOLOGY OF THE AREA The migmatite group of rocks include the coarse-grained dark grey migmatite, pinkish grey and greyish pink ‘Paradiso’ migmatite, later traversed by swarms of the dolerite dykes oriented mainly along WNW-ESE direction. The alkaline rocks represented by epidote hornblende gneiss is confined to the southern margins of the area.

Objective of the Resource Survey:

Objective of the Resource Survey a). Demarcation of the commercial litho boundaries of different varieties of Paradiso granite occurring within the belt. b) Within such commercial litho boundaries, demarcate the productive, defective and promising zones to minimize quarry failures. c) Assessment of Recovery percentage of each of the 105 quarries surveyed and on the probable reserve of the entire belt.

RESULTS OF THE SURVEY:

RESULTS OF THE SURVEY Survey has identified around 25 quarries as most successful in its operations and another 25 quarries under average category and the remaining 55 quarries categorised under failure category. Main reasons for high rate of failure is due to poor recovery which may be attributed to structural defects like shear cracks etc.

Highlights of recovery percentage in each of the four major blocks of Krishnagiri belt:

Highlights of recovery percentage in each of the four major blocks of Krishnagiri belt Sl.No No. of quarries surveyed. Colour Pattern/design Main defects Average Recovery % % of Failures 1 36 Pink/Grey mixed Moderate to poor Colour /pattern variations/black /orange patches/Hairline fractures/quartz lines/feldspar patches etc. Poor to 10-15-25% 44% 1.Chendarapalli-Soolamalai-Jagadevi block

2. Modikuppam-Togarapalli Block:

2. Modikuppam-Togarapalli Block Sl.No No. of quarries surveyed. Colour Pattern/design Main defects Average Recovery % % of Failures 1 17 Grey/pink mixed Poor to Moderate Black patches/ Colour /pattern variations /orange patches/Hairline fractures/Pegmatite and quartz veins/Green epidote lines Poor to maximum 20% 64%

3. Velampatti -Tattakkal - Jainur Block:

3. Velampatti -Tattakkal - Jainur Block Sl.No No. of quarries surveyed. Colour Pattern/design Main defects Average Recovery % % of Failures 1 32 Grey/pink mixed besides violetish grey Poor to Moderate Colour /pattern variations/ Hairline fractures/orange/ black patches/ black dots/green lines etc. Poor to maximum 15% 44%

4. Sandur – Mattur Block:

4 . Sandur – Mattur Block Sl.No No. of quarries surveyed. Colour Pattern/design Main defects Average Recovery % % of Failures 1 20 Grey/pink mixed besides violetish grey Poor to Moderate Hairline fractures/ grey Colour domination /pattern variations/ / black patches etc. Poor to maximum 15% 55%

SUMMARY:

A database has been generated for the entire Paradiso belt, Reflects on an average of poor recovery to maximum of 25 % for the entire belt of 350sq.km. Critical evaluation of each of the deposit under geological and marketing considerations will bring down the failure rate in each of the belts besides minimizing the environmental problems in those respective belts. SUMMARY

SUMMARY:

SUMMARY In view of the geological attributes as mentioned, failure rate in quarry operations turned out to quite high. As a result the quarries had to be abandoned abruptly causing much damage to the environment (land degradation) and huge accumulation of waste rocks. Most of the agricultural belt mainly mango yielding belt has been damaged in Krishnagiri area. Above environmental damage could have been avoided had the deposit been assessed scientifically prior to commencement of exploitation. Basic failure to understand the geometry of deposit is causing much environmental degradation besides on disposal of huge waste rocks in the belt.

Assessment of Recovery percentage in major granite belts of TamilNadu:

Assessment of Recovery percentage in major granite belts of TamilNadu 2 . KASHMIR WHITE GRANITE BELT OF MELUR AREA,MADURAI DISTRICT, TAMILNADU.

MELUR BELT:

MELUR BELT Melur belt, Madurai district is endowed with a number of multi-coloured granite deposits like Kashmir White, Raw Silk, Tiger Skin, Pink- multi etc., Out of which, major granite activity is restricted to the 15 km. linear Leptynite deposit commercially known as Kashmir White stretching along E-W direction between Kilaiyur on the west and Kilavalavu- Purakuttu malai in the east.

MELUR BELT:

MELUR BELT Sudden spurt of export demand for this material in different commercial names viz. Kashmir Gold, Ivory pink, Ivory white, Kashmir white, New colonial cream/white etc. the quarrying activity during the last decade has grown up beyond any imagination.

MELUR BELT:

MELUR BELT Kashmir deposit having rusted garnets and top yellow weathering zone were rejected in nineties but have maximum demand in the present export market, which is quite astonishing.

MELUR BELT:

MELUR BELT Kashmir White deposit (Leptynite) being the remelted ( anatectic) product of the Khondalitic country rock, it is a misconception in arriving at a uniform 90% recovery for the entire belt without giving allowance for colour and textural variations besides for the enclaves of unmelted or partially digested country rock black patches within the deposit and for the effects of lateral shears/ structural disturbances.

Buyers Preference in Kashmir White Past and Present:

Buyers Preference in Kashmir White Past and Present

BETTER RECOVERY QUARRY:

BETTER RECOVERY QUARRY

LOW RECOVERY QUARRY:

LOW RECOVERY QUARRY

Blocks with black patches:

Blocks with black patches

RECOVERY PERCENTAGE OF THE DEPOSIT:

RECOVERY PERCENTAGE OF THE DEPOSIT 1. Kilayur-Kilavalavu Main productive zone: Length of the band : 2.5 km Breadth/Width of the band : 250m. Recovery Percentage : 40% ( recovery may be lower within the zone due to the variations and percentage of defects and massiveness of sheet formation in each of the quarries)

RECOVERY PERCENTAGE OF THE DEPOSIT:

RECOVERY PERCENTAGE OF THE DEPOSIT 2. E. Malampatti Productive zone: Length of the band : 1.5 km Breadth/Width of the band : 45m. Recovery Percentage : 30% ( recovery may be lower within the zone due to the variations and percentage of defects and massiveness of sheet formation in each of the quarries)

RECOVERY PERCENTAGE OF THE DEPOSIT:

RECOVERY PERCENTAGE OF THE DEPOSIT Besides Geological aspects, buyers’ likes and dislikes in a natural granite formation e.g for yellow /Gold material in Kashmir White, the recovery percentage of such particular material may be restricted to 5- 10 m in a quarry and hence one can presume a low recovery of 15-20% only . Considering the trend and demand, one can visualize the recovery percentage of those quarries.

Conclusion :

Conclusion Proper assessment of the geometry of each granite deposit ultimately determines its recovery, size and scope of the prospect. Our past experience in the trade has taught us a lesson that the success of the industry primarily depends on adopting the right techniques both in evaluation and its exploitation with latest technological advancements to fulfil the basic requirements of overseas buyers. Present trend in the industry is focused on High volume and Low margin business.

CONCLUSION:

CONCLUSION The paper has highlighted the various considerations that are essential for arriving at the recovery percentage in a quarry. With out a geological map of a quarry or for the belt, one can not do justice in arriving at the reserve and it is the basic tool before and after commencement of any quarry operation.

CONCLUSION:

CONCLUSION Vital Geological inputs not only forecast the success and failure of the deposit but also on assessing the average recovery percentage. Recovery percentage of each of the quarry can be assessed ONLINE on monthly basis based on the blocks produced and the quantum of waste disposed of. Method is not only realistic but also prudent.

THANK YOU :

THANK YOU

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