Dharwar-Shimoga Belt

Dharwar-Shimoga Belt Project, Karnataka State

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This Project area forms part of Archaean Western Dharwar Craton in the State of Karnataka. Deccan Exploration Services Private Limited (DESPL), a wholly-owned subsidiary of Deccan Gold Mines Limited (DGML), explored an area of 5000 sq km of the Dharwar-Shimoga Greenstone belt covered under 2 RP blocks and identified 22 gold prospects.

Gold mineralization in all the prospects is hosted within sulphidic banded ferruginous chert. Prospects around Dharwar towards north (Dharwar Cluster) and Haveri in the south (Ganajur-Karajgi Cluster) are considered as significant discoveries. Seven (7) Prospecting License (PL) and two (2) Mining Lease (ML) applications, covering all the important prospects of Dharwar-Shimoga basin, were filed. The Ganajur-Karajgi PL, within the southern Ganajur-Karajgi cluster, was granted in the year 2009.

The Mangalagatti PL, which is located in the northern Dharwar Cluster, was granted in the year 2013 but the execution process is awaited.   The remaining applications are under various stages of processing. The updates on the Dharwar-Shimoga Belt Projects are presented below:

GANAJUR MAIN GOLD DEPOSIT & ITS SATELLITE PROSPECTS IN THE  GANAJUR – KARAJGI CLUSTER

DESPL had carried out systematic exploration in the Hanagal RP Block covering an area of 1542 sq.km.  The Reconnaissance included litho-structural mapping, regional stream geochemical, rock chip, channel sampling, limited Reverse Circulation Drilling (RC) and Down the hole Hammer drilling (DTH). The exploratory work during the RP tenure resulted in delineating several new gold prospects.  The Ganajur Main Gold prospect has now progressed into a future mining project with economically mineable grades.

DGML has lodged 3 prospecting Licence applications covering all the important prospects. Gold mineralization in the area is hosted within Banded sulphidic chert.

 

Amongst the 3 PL applications that were lodged DESPL was granted the Prospecting Licence over an area of 2.2 sq.kms by the Government of Karnataka for the Ganajur-Karajgi PL Block on 10.9.2009. The PL was executed on 25th September 2009. Ganajur-Karajgi PL Block is part of Ranibennur group of the late Archaean-Dharwar-Shimoga greenstone belt in the western Dharwar Craton. DESPL explored the PL Block by multidisciplinary techniques as per international standards. The exploration efforts have resulted in upgrading the project in terms of resource augmentation and value addition.  The PL block comprises the highly rated Ganajur Main Gold Deposit which has now progressed into an advanced project that is surrounded by other seven (7) Satellite Prospects known as Ganajur East, South, South East, Central prospects, Karajgi Main, Karajgi East and Hut prospects.

Exploration carried out so far has demonstrated that the Ganajur-Karajgi PL block is an important mineralised corridor with a substantial  possibility of finding additional gold resources.  Summary of work carried out under the PL is furnished below:

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TABLE-1, SUMMARY OF EXPLORATION WORK CARRIED OUT IN  GANAJUR-KARAJGI PL BLOCK

SL NO TYPE OF EXPLORATION UNIT QUANTUM
1 TOPOGRAPHIC SURVEY SQ.KMS 2.2
2 GEOLOGICAL MAPPING (1: 2000 AND 1:5000 SCALE) SQ.KMS 2.2
3 GROUND GEOPHYSICAL MAGNETIC SURVEY LINE KMS 288
4 GROUND GEOPHYSICAL SP-RESISTIVITY SURVEY LINE KMS 16.5
5 GROUND GEOPHYSICAL IP SURVEY LINE KMS 17.4
6 GROUND GEOPHYSICAL EM SURVEY LINE KMS 9
7 TRENCHING LENGTH (M) 945.3
8 SAMPLING AND ANALYSIS Nos 2707
9 DRILLING    
  A. RC DRILLING (51 DRILL HOLES) METRES 2328
  B. DIAMOND CORE DRILLING (76 DRILL HOLES) METRES 6147.29
  TOTAL DRILLING 8475.29
10 COMPREHENSIVE METALLURGICAL STUDIES (AMMTEC) KGS 200
11 ENVIRONMENTAL BASE LINE DATA COLLECTION (AIR, DUST FALL, NOISE, WATER, SOIL) SAMPLES 207
12 MINERAL RESOURCE ESTIMATION BY SRK (AS PER JORC) COMPLETED
13 SCOPING/PRE-FEASIBILITY STUDIES (for Ganajur Main Gold Project) COMPLETED
14 LAND ACQUISITION  IN PROCESS

 

The details of the individual prospects in the Ganajur-Karajgi Cluster are given below:

 

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a) Ganajur Main Prospect 

Ganajur Main Gold Prospect is a new discovery by DGML that came to light during the RP tenure. It is one of the most advanced projects of the company. DESPL carried out a limited drilling programme during the RP period that indicated significant gold grades over substantial width. Based on this drilling an inferred resource of 1.53 million tonnes grading 3.79 g/t (approximately 122,000 ounces of contained gold) was estimated.

Immediately after the execution of the PL, DESPL undertook a detailed exploration programme involving trenching, diamond core and  RC drilling as per International norms to discover an open pittable resource. DESPL has completed 4166 metres of diamond core and 1219 metres of Reverse Circulation (RC) drilling at Ganajur Main Prospect. This has resulted in defining a mineralised zone of 600 metres along the strike direction and 120 metres along the depth. Most of the drill holes intersected significant gold mineralization over a considerable width which is ideal for an open pit mining operation  DESPL also lodged a Mining Lease application covering an area of 0.29 sq.kms covering Ganajur Main Prospect. This application is currently awaiting approval of the Ministry of Mines, Government of India (MoM) after it was recommended by the State Government of Karnataka (SG).

The details of the mineralization intersected in the drill holes completed during the PL stage is furnished in the Table-2.

TABLE-2,  DETAILS OF MINERALISED ZONES INTERSECTED IN THE DRILL HOLES

SL.NO BH ID From (m) To (m) Average Width (m) Average Au (g/t) Drill Type
1 G 12 20 24 4 2.19 RC
G 12 32 34 2 3.66 RC
2 G 16 24 41 17 3.89 RC
3 G 18 21 32 11 3.6 RC
4 G 22 11 13 2 1.9 RC
5 G 25 21 24 3 1.62 RC
6 G 27 22 23 1 3.13 RC
7 G34 63 72 9 6.49 RC
8 G35 92 93 1 1.72 RC
9 GMC-1 34.6 43.6 9 5.21 Core
GMC-1 47.1 48.1 1 1.4 Core
10 GMC-2 46.2 53.4 7.2 1.51 Core
GMC-2 54.4 79.9 25.5 1.12 Core
11 GMC-3 59.4 79.9 20.5 2.64 Core
GMC-3 84.4 93.4 9 3.27 Core
12 GMC-4 29.5 45 15.5 2.84 Core
GMC-4 48 56.5 8.5 5.85 Core
13 GMC-5 47 48.5 1.5 1.71 Core
GMC-5 50 79 29 8.54 Core
14 GMC-7 39.9 72.5 32.6 9.89 Core
15 GMC-9 83 90 7 4.46 Core
16 GMC-10 48.35 75 26.65 3.86 Core
17 GMC-11 39.3 46.8 7.5 5.37 Core
GMC-11 54.2 57.7 3.5 6.65 Core
GMC-11 62.8 65.8 3 4.19 Core
18 GMC-12 44 58.3 14.3 4.03 Core
19 GMC-13 59.2 71.15 11.95 3.58 Core
20 GMC-14 85.8 89.5 3.7 3.7 Core
21 GMC-15 47.7 62.31 14.61 3.24 Core
22 GMC-16 22.5 65.34 42.84 8.91 Core
23 GMC-17R 43.3 70.7 27.44 7.89 Core
24 GMC-18 57.9 80.75 22.85 5.45 Core
25 GMC-19 34.4 53.9 19 5.13 Core
26 GMC-27 39 45.5 6.5 2.19 Core
27 GMC-28 33.5 39 5.5 3.97 Core
28 GMC-29 48 54 6 2.05 Core
29 GMC-29 64.5 69.7 5.2 3.05 Core
30 GMC-30 8.4 22.5 14.1 1.35 Core

 

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Based on the excellent exploration results DGML appointed SRK Mining Services (India) Pvt Ltd. to independently review the data and submit a mineral resource estimate and preliminary economic assessment of the Ganajur Main Gold Deposit. SRK has estimated a JORC compliant resource of 3,08,000 oz of gold to a depth of 120 meters of which most of it is under indicated category (Table-3). The resource is equivalent to 121 category as per UNFC classification. Resource estimation was carried out by generating 3D block models with the help of Datamine Software and grade interpolation was done using Kriging Method. The 3D model was subdivided into two domains viz, Oxide and Sulphide domains based on the lithological observation of the drilled core.

 

 

 

 

 

 

 

Table 3- Mineral Resource statement of Ganajur Main Gold Deposit

CATEGORY AS PER SRK (JORC)

Quantity (tonnes)

Grade (g/t)

Gold (ounces)

UNFC CODE AS PER IBM

A. SULPHIDE B. OXIDE 1. INDICATED

1,921,000 631,000

3.83 3.19

237,000 65,000

TOTAL INDICATED

2,552,000

3.67

301,000

121

A. SULPHIDE B. OXIDE 2. INFERRED

93,000 17,000

1.82 3.26

5,000 2,000

TOTAL INFERRED

109,000

2.06

7,000

 

Metallurgical Studies

A representative sample (200 KGS) of the Ganajur sulphide gold ore drawn from the drill cores and was sent to Internationally reputable ALS-AMMTEC Laboratory, Perth in Australia for carrying out a comprehensive metallurgical testing and gold recovery studies. The ore sample was tested to know the following aspects:

  1.   Resistance to crushing measured as Abrasive Index
  2.   Resistance to grinding – measured as Bond’s Work Index
  3.   Presence of free gold – recovered as gravity concentrates
  4.   Presence of locked gold – recovered as cyanidable gold
  5.  Diagnostic gold analysis test work
  6.   Flotation product test work
  7.   Best possible route to get maximum gold recovery
  8.   Reagent consumption

Based on the inferences of the results of Bench-Scale Testing of the Ganajur ore two Preliminary flow sheets for the recovery of gold were developed. The recovery route can be either of the following:

  1. Crushing – grinding – gravity – CIL
  2. Crushing – grinding – flotation – roasting – CIL

The first route is simple but has a low gold recovery of 76.93%. The second route is more efficient in gold recovery (89%), but involves roasting of flotation.

Key developments on Ganajur Main gold project is as follows:

  1. DGML has entered into MOU with Government of Karnataka to establish a gold mining industry in this project area. The company has proposed for a 2000 TPD processing unit.
  2. Mining Lease application is under consideration at Ministry of Mines, New Delhi.
  3. State Level Expert Appraisal Committee (SEAC), Karnataka has accepted an application for Terms Of Reference (TOR) and issued a letter of TOR for the proposed 2000 TPD Ganajur gold ore mine. The total area covered under TOR is 48 Ha that includes 29.14 Ha covered under the Mining Lease Application.
  4. DESPL’s application of TOR for the proposed 2000 TPD processing plant with the Ministry of Environment and Forests (MOEF) has also been accepted. The total area covered b y this application is 38.45 Ha.
  5. DESPL has taken up the environmental studies in and around the project area as per the Terms of Reference issued by both SEAC and MOEF.
  6. State High-Level Clearance Committee (SHLCC), cleared the request for allotment of 200 acres of land for the Ganajur Main Gold Mining and Ore Processing Plant. Land acquisition will be routed through Karnataka Industrial Areas Development Board (KIADB).
  7. DGML has also submitted the application with the Karnataka Industrial Areas Development Board (KIADB) for allotment and acquisition of 200 acres of land for the plant and mines on 26-03-2013. Consent of 70% of the land owners has been obtained a pre-requisite for initiating the land acquisition process.
  8. Mine development and gold production are expected in the year in the year 2017 after the receipt all these approvals.
  9. Mining Plan is being finalised that would be submitted to Indian Bureau of Mines once the Letter of Intent from the State Government is obtained.

 

DGML has made all out efforts to speed up the implementation of the project while the approval of the ML is awaited.

 

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b) Ganajur South East Prospect 

Ganajur southeast prospect is located at 1.2 km SE of Ganajur Main prospect.  The mineralized body is a gossanous banded sulphidic chert hosted by greywacke & traversed by fine stringers of quartz-carbonate veins and is considered as the south-eastern extension of Ganajur Main Gold Deposit.  The prospect was discovered during exploration under an RP that was further confirmed by detailed trenching and drilling during the PL stage.  Exploration under the PL stage also defines  mineralized zone for a length of 455 metres. DESPL carried out IP survey in the PL area that indicated significant charge ability anomaly extending for nearly 2.8 kms that included Ganajur SE prospect. Preliminary RC drilling in this prospect intersected significant mineralization that included  6.23 g/t Au over 15.0m width in one of the drill holes.
Encouraged by these findings a close spaced diamond core drilling programme was initiated and 1276.95 metres of drilling was carried out in 15 drill holes. The drilling was in accordance with the international best practices and QA/QC procedures.  Most of the drill holes intersected a sulphidic chert band carrying significant gold values. Table-4 summarizes the intersections of gold in the drill holes. Typical drill hole cross section is given in

 

TABLE-4, DETAILS OF MINERALISED ZONES INTERSECTED IN THE DRILL HOLES, GANAJUR SE PROSPECT

 

BHID FROM (M) TO (M) WIDTH (M) GRADE AU G/T HIGHEST GOLD VALUE
GSEP-C7 63.4 67.9 4.5 3.81 12.5
70.6 71.6 1 2.75 4.2
74.6 76.2 1.6 4.1 10.39
GSEP-C8 38.5 42.5 4 4.3 17.38
GSEP-C10 68.65 74.9 6.25 8.31 20.21
80.4 83.2 2.8 3.73 4.9
GSEP-C2 54 57.15 3.15 3.58 11.01
62 62.5 0.5 5.95 5.95
GSEP-C3 46.2 49.1 2.9 2.24 5.59
53.1 56.6 3.5 1.82 3.87
GSEP-C4 80.6 81.1 0.5 7.58 7.58
GSEP-C5 41.2 44.2 3 1.32 2.28
GSEP-C6 64.7 66.3 1.6 2.25 3.15
GSEP-C12 71.2 74.1 2.4 1.96 4.1
GSEP-C13 91.6 96.45 4.85 3.58 17.81
GSEP-C14 70.35 76.55 2.7 5.41 10.44
78.75 81.4 2.65 4.36 8.56
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The results from the latest drilling programme has confirmed our interpretation of finding additional gold Resources in the satellite prospects surrounding the Ganajur Main Gold Deposit which is currently under consideration of the Govt. of India for grant of Mining Lease.

An indicated resource of 35,000 ozs of gold was estimated by DESPL to a vertical depth of 110 metres. The parameters considered include specific gravity of 2.95 and the cut-off grade of 0.5 g/t Au.  The ore body extends for a strike length of 150 metres and is open to the strike and depth.

c)Karajgi Main Prospect

The prospect is located 1 km SE of the Ganajur Main Prospect. Several ancient workings are located in the BIFs. During RP tenure DESPL completed a short programme of 861m of RC drilling following an earlier programme of channel sampling of auriferous BIF bands. This brought to light a 133m long 6.59 m wide zone of gold with the grade averaging 3.23 g/t up to a shallow depth of 50 m. An inferred resource of 90000 tonnes averaging 2.23 g/t was estimated on the southern branch of the sulphidic BIF. Significant results during RP followed by an indication of strong charge ability/IP  features prompted DESPL to undertake additional drilling in this block under PL.

In the first phased, DESPL completed 2 diamond core drill holes at Karajgi Main prospect in order to test the geophysical IP anomaly and also to understand structural controls of gold mineralisation. Out of two holes drilled, KMC-01 intersected two significant zones of gold mineralisation. The first one is 5.0 m thick which passed through between  45.50 to 50.50m averaging 7.43 g/t. gold including a high value of 33.60 g/t.  The second zone is 9.0 m thick and was encountered between 71.1 and 80.1m averaging 3.19 g/t gold. The results from Karajgi Main Prospect have confirmed the existence of high-grade gold-bearing zones and a distinct possibility of finding additional resources. Additional drilling was also completed after this observation.

DESPL compiled all the data generated under RP and PL stages in Karajgi Main prospect and a 3D resource model was generated. The ore body section was constructed using 0.5 g/t Au as cut off and a minimum width of 1m.

A total of 3 auriferous zones were defined trending northwest and dipping towards the northeast.  Zone-1 and 2 with the cumulative strike length of 360 metres with steep dips towards NE are the two branches that constitute the Karajgi main mineralised zone.  Zone-3 is on the northern slope of the Karajgi Main hill that is correlated to Band-A. Zone-3 has a strike length of 140 metres dipping at 30 to 35towards NE.

Based on these data DESPL re-estimated the resource for Karajgi Main Prospect. The resource was estimated up to a vertical depth of 80 metres. The true thickness of the ore body varies between 1.45 to 9.0 metres.  An inferred resource of 26000 ozs of Au was estimated averaging 3.07 g/t.

d) Karajgi Hut Prospect

The Karajgi Hut prospect is located around 600m NE of Karajgi Main prospect. Two parallel BIF bands were defined with a cumulative strike length of 530 metres as a result of exploration carried out under RP and PL stage. Preliminary RC drilling has indicated that the northwestern part is more promising in terms of gold grades and width. Ground IP geophysical survey has also indicated a moderate IP anomaly in this block. DESPL carried out a systematic resistivity survey towards NW part of this prospect in order to examine the possibility of finding concealed mineralised chert bands if any and also to explore NW extension of the mineralised chert bands already known. A total of 2.4 line kms of survey was accomplished along NE and SE profiles. The survey was carried out using Schlumberger array at an electrode spacing of 5m, 10m and 15m separation.

The data was processed using Encom Discover and IP2Win softwares. The resultant plots reveal two NW-SE trending moderately resistive anomalies that could be interpreted as two limbs of a folded structure. These anomalies are interpreted as the Northwest extension of the mineralised chert band of Hut Prospect. DESPL now plans to expose the new targets by way of trenching.

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e) Lakkikoppa Prospect

At Lakkikoppa Prospect, gold mineralization occurs in BIFs over 3 km length. Surface rock chip samples returned assays up to 2.07 g/t gold. Resampling of 44 trenches opened by the GSI, gave assays ranging from 1.45 to 3.5 g/t for 1 to 5 m width over a length of 500m. GSI has drilled 11 diamond drill holes over 3 km length of the BIF. We would purchase the GSI’s data for our own assessment before planning future drilling programmes in this important prospect.

Mangalagatti and Bhavihal Prospects in Mangalgatti Cluster :

Mangalagatti and Bhavihal prospects are located 12 to 20 kms north of Dharwar city. They form part of the ‘Dharwar Cluster’ of gold bearing sulphidic Chert bands. The Dharwar cluster comprises of Mangalagatti SE, Mangalagatti Main, NW and Bhavihal prospects. All these are considered as highly potential like the Ganajur-Karajgi cluster near Haveri. DESPL’s application of Prospecting License over an area of 4 sq.kms and covering the Mangalagatti Prospects was approved by Ministry of Mines and Government of Karnataka issued grant order in the month of October, 2012 and the PL is expected to be executed shortly.

f) Mangalagatti Prospect:

Initial exploration during the RP tenure in the Mangalagatti SE prospect by RC drilling and channel sampling had revealed significant gold mineralization. Gold mineralization is hosted by south-easterly plunging folded banded iron formation. Two auriferous zones extending for nearly 500 metres over a width of 30 metres were defined. An ancient working and adjacent pounding marks indicates ancient mining activity in the area. An inferred resource of 1.5 million tonnes@ 1.63 g/t Au was estimated based upon results of shallow RC drilling programme.

After the successful exploration by geophysical methods in the Ganajur-Karajgi PL block, DGML conducted Induced Polarization (IP) survey in the PL block to investigate the existence of possible mineralised zones in addition to those already explored. The IP survey was carried out on 12 lines by dipole-dipole configuration at 50 to 100 m dipole spacing involving 19.7 line kms.

The results of the IP survey revealed a 300 to 400 metres wide broad-based charge ability anomaly suggesting that the mineralization is controlled by a folded structure. More interestingly the IP anomaly has been traced all along for a distance of 2.0 kms and the anomaly is still open.  

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DGML also tested the depth extension of the IP anomaly by carrying out the survey at larger dipole separation. The survey indicates that the IP anomaly continue to greater depths below 200 metres with the sharp increase in the intensity of the anomaly.

These results are very positive and warrants detailed exploration by drilling. DGML will launch resource drilling in Mangalagatti SE prospect and its adjacent targets once the PL is executed.

g) Mangalgatti NW Prospect

Drilling in the NW prospect gave relatively, subdued intersections within strongly weathered rocks. The strongly weathered zone extends beyond 50 metres depth, as in many parts of the Western Australian goldfields. The subdued intersections are typical of the strongly leached profile. Further drilling revealed a structurally controlled quartz-vein zone of mineralization. We plan to carry out deeper drilling to find out the exact width, grade and style of the gold bearing tract in this prospect.

h) Bhavihal Prospect  :

Bhavihal prospect is located at a distance of 8 kms NW of Mangalagatti prospect. Preliminary channel sampling followed by RC drilling during the RP tenure had clearly brought out surface expression of a wide ore body hosted in cherty BIF. The poorly outcropping auriferous chert in this prospect has given high surface assay values of up to 29 g/t. The limited RC drilling was also intended to examine open pittable resource similar to Mangalagatti SE prospect. As a result of this preliminary investigation an area of 400 metres was delineated and an inferred resource of 74,000 oz of Au was estimated averaging 1.76 g/t. A preliminary IP survey was initiated on 3 lines to understand the IP signature. It is very encouraging to note that all the three lines have brought out two moderate charge ability anomalies with co-incident resistivity highs. With this positive information, it is planned to go ahead with additional IP survey to explore the depth and strike continuity of the mineralization.

i) Kulavalli Prospect

Kulavalli Prospect, like the Bhavihal, is located not far off from Mangalagatti Prospect. Kulavalli gold-bearing tract is 4.3km long. Four parallel gold- bearing BIFs have been recognized to date. Initial surface rock chip sampling gave values ranging from 0.18 to 6.1g/t gold. Follow-up spot rock-chip sampling gave assays from 0.27 to 18.0g/t gold and a channel sample gave 6.73 g/t over 8m width. A PL application has been filed for undertaking intensive drilling in this important prospect.

j) Durgadakeri Prospect

Durgadakeri Prospect has a strike length of 4 km. Ten rock chip samples from this prospect showed gold in the range of 0.3 to 40.16 g/t Au. Further surface exploration will precede drill testing.

k) Jakkinakatti Prospect

In Jakkinakatti Prospect, the gold-bearing BIF is exposed over a strike length of 700m with the width varying from 3 to 4 metres. Rock chip and channel sampling have brought out a mineralized zone, 180m long x 3.4m wide. The gold content of rock chips ranged from 0.06 to 4.67 g/t while the channel sampling gave assays in the range 0.01 to 13.55 g/t.