Gold deposits of karnataka

Gold deposits of karnataka

1. GOLD DEPOSITS OF KARNATAKA SEMINAR ON

2. Contents : I ntroduction Origin Gold deposits situated in karnataka Formation of Kolar gold field Kolar Gold deposites Hutti Gold field Mode of occurrence of Gold Conclusions References

3. INTRODUCTION It also has complete resistance to the common corrosive agents and there fore to oxidation and tarnishing. The Carat is a useful indicator of the gold content of jewellery, 24 Carat being pure gold. Gold exhibits a combination of physical and chemical properties which render it unique. It melts at about 1060 , has a naturally lustrous colour. It is extremely malleable and ductile and is efficient of electricity. Gold has a high specific gravity 19.6 Indian jewellery by for the largest demand is usually 22 Carat, where the proportion of Silver is considerable. Chemical symbol of gold is Au

4. ORIGIN All primary Gold deposits are formed usually during the late stages of the chilling of the magma ,which along fissures to the upper layers of the earth`s crust from great depths. The Gold is transported together with the magma from the depths of the earth in hot aqueous solution and vapors. These solutions get solidified with the falling of temperature, giving rise to ore bodies mostly in the form of veins in rocks. These veins generally consist of Quartz with a small admixture of other minerals. The particles of gold in the form of fine grains, platelets and flaks and some times crystals wires, filaments etc. In the course of time these rocks and veins under the action of geological agents, undergo mechanical disintegration and chemical decomposition. The weathered products while being carried down to the depositional site undergo the process give rise to placer Gold deposits. Economic gold minerals are 1) Native gold 2)Gold amalgam 3) Telluride( Calaverite , Sylvanite , Krennerite , Petzite )

5. MODE OF OCCURENCE LODE GOLD Gold occurs many geological settings. The following are the important principal modes of occurrences observed in India. STRATIFORM GOLD IN GRANULITE BELT DISSIMINATED GOLD IN CONGLOMERATES PLACER & ALLUVIAL GOLD GOLD IN LATERITE SOILS

6. Gold deposits of Karnataka There are two Gold fields situated in Karnataka. They are 1.KOLAR gold field 2.HUTTI gold field In Kolar Gold field the Gold deposits are associated with schistose rocks where aluminiumferous quartzite lodes occur along closely placed mineralized zones. In Hutti Gold field, the Gold deposits are occur along fractures within chlorite schist's and greenstones in a highly regular manner. These gold fields are within the Dharwar schist belts of Karnataka KGF is about 30 kilometers from Kolar and 100 kilometers from Bangalore. Hutti is situated in Raichur District, Karnataka State, located at 80 km due west of Raichur

7. Hutti gold fields Kolar gold fields

8. FORMATION OF GOLD IN KOLAR GOLD FIELD The Kolar Greenstone or Schist Belt covers a 3 - 6km wide area extending up to 80km in length.  The rocks within the belt are comprised of complexly folded and faulted mafic and felsic volcanic sequence generally of low metamorphic grade. The northern 40 km long portion of the belt has laterite cover restricts exploration work The three groups of the Kolar Gold Fields, being Gold is preferentially concentrated in vein quartz, often associated with sulphides.  Most of these gold prospects represent typical Archean hydrothermal lode gold mineralization. South Kolar East Kolar North Kolar

9. North Kolar covers the northerly extension of the Kolar Greenstone Belt and includes major synformal fold. Lode gold mineralisation is hosted by shear zones, sheared granite and quartz viens .  NORTH KOLAR Quartz bodies of different types, both barren and mineralised and several generations occur in the ferruginous and carbonaceous Phyllites and within linear bodies of metagabbro .  

10. SOUTH KOLAR mineralisation occurs near to the contact of the mafic amphibolitic metabasalt with felsic volcanic and metasediments of the Champion Gneiss.   Gold is concentrated in vein quartz and also associated with sulphides. The zone having highly sulphidic rocks and at one of the prospects and quartz viens on the other end.

11. EAST KOLAR This horizon is a heterogeneous assemblage of volcano-sedimentary rocks . The volcanics are represented by rhyolite and acidic tuffs of dacitic composition.  All these are deformed and metamorphosed to lower amphibolite facies . Gold mineralisation in the Surapalle area occurs in highly tectonised shear zones which transect the foliation at a very low angle

12. Kolar gold field have four productive mines Nandydurg mine Champian reef Mysore mine Ooregum The champian reef mine is one of the deepest mine in the word. The average content of champian reef was 15grams/tonn There were about 15 parallel lodes in the kolar gold field, in them 6 were gold-quartz lodes,9 were gold-quartz-sulphide lodes About 84 tones of gold have been produced since the mines were nationalized

13. Champion lode of Kolar gold field: The gold -quartz lode is localized along a shear zone traversing the mafic rocks of komatitic and tholeitic character This lode have been mined over a strike lenth of more than 8 km and to depth of 3400 mts . Lode are mainly made up of quartz and calcite .Other minerals include sheelite , biotite , muscovite, and tourmaline. Sulphides are pyrite, arsenopyrite , pyrhotite , chalcopyrite and galena. High values of Cr and Ni are also noticed

14. The wall rock reaction have taken place along the structural features. REE geochemistry of quartz-carbonate lodes indicate light REE compared sulphide lodes. Mobilization of gold took place around 2600my The important wall rock alteration which accompany the mineralization are sericitization , chloritization , biotization , carbonization and greisenization . (CONT..)

15. Stratiform Sulphide type: The Oriental lode of KFG is a stratiform sulphide type lode lying about 400 to 500 mts to the west of champion reef lode in north Kolar . It is strongly a pyritic lode. Width of this lode is ranges from 1.5mts-4.5mts This lode is localized between volcanic flows and it is made up of alternating bands of sulphide and amphibole-quartzite encountered in archian schist belts Dominating sulphide minerals are pyrhotite with arsenopyrite and minor pyrite chalcopyrite and sphalerite .

16. HUTTI GOLD FIELD There are number of gold bearing quartz veins extensively mined to shallow depths There is a number of old prospects include HUTTI, MASKI, BUDINI, TOPDUR, CHIKHARUR, TOPPALDODDI, WONDALLI, KADONI, UDBAL, MUKANGAVI The country rocks are greenstones, cherts , chlorite schist intruded by granite, quartz, porphyry gabro and dolerite dykes. There 6 auriferous qurtz reefs strike village Zone-1 Middle reef oakely`s reef Main reef

17. In the Main reef Quartz veins occupy fissures in surrounding rocks. The quartz occurs in the form of lenses, often less than 100 ft in depth. The pyrites are abundantly developed in grains and crystals throughout the lodes. The gold is free and it has been deposited independently of pyrite Samples from the southern extension of Main reef gave 22gm/ton over 0.35mts, 20gm/ton over 0.45m, 10gm/ton over 0.60m

18. Oakery`s reef in the hutti gold field have been provided to be auriferous over a strike length of 213mts with 1.25gm/ton to 9.98gm/ton Up to 1990 about 33 tonnes of gold have been recovered from 5 million tonnes of ore at a recovery grade of 6.52gm/ton. The company formed in1947 to mine the Hutti gold field, as the Hyderabad gold mine company ltd, with the Hyderabad state gov.Then transformed to Karnataka state and became the Hutti gold mines company ltd

19. CONCLUSIONS: Gold has been prised high and considered as king of the metals. Kolar and hutti gold fields are important gold producing centers in karnataka Champion reef is the richest gold bearing quartz-lode in so far encountered in india . The champian reef mine is one of the deepest mine in the word. Gold deposits generally occurs with quartzite and sulphide lodes within these two gold fields Main reef is the important gold producing reef among the Hutti gold field

20. B.P.Radhakrishna (1990) GOLD –the Indian scene , Published by GSI,p:143 K.V.G.K.Gokhale&T.C.Rao Ore deposites of India Thomson ltd.1973, p:101 REFERENCES: http://www.search.ask.com/web?q=kolar+gold+field http://en.wikipedia.org/wiki/Hatti_Gold_Mines