Journal of Geological Society of India (Online archive from Vol 1 to Vol 78)

M. Bhargava ¹, A. B. Pal ¹

Affiliations
1 Hindustan Copper Ltd., Malanjkhand - 481 116, Madhya Pradesh, IN

Abstract

Regional studies covering the Malanjkhand granitoid pluton have indicated various features related to Cu-Mo-Au metallogeny in the area. The rocks belong to Archaem and Proterozoic sequences and are similar to those occurring further south of Malanjkhand in the Dongargarh area.

Malanjkhand pluton is emplaced in an environment favourable for Cu-Mo-Au mineralization. It is located at the northern end of the Kotri-Dongargarh mobile belt. Magmatic differentiation resulting in a copper-bearing hydrothermal phase could be the source of copper. The mineralized vein systems occur close to microgranitoid intrusions, which are the most differentiated rocks in the area. Hydrothermal activity could be related to these intrusives.

Regional structures indicate a marked similarity in orientation of megascopic fabric elements such as shears and fractures, schistosity and gneissosity, faults, orientation of quartz veins and dykes. All the elements indicate a dominant N-S trend and the role of regional stresses. The fissures and mylonitized shear zones provided the channels through which acidic and basic magmatic activity took place.

The ore mineral assemblages include Cu-Mo-Au with Ag and traces of Co. The veins are emplaced in shear zones in the granitoids, along schistosity planes in older schistose and gneissic rocks and at the contact of granitoids with Nandgaon volcanics. Most veins, basic dykes and microgranitoid intrusions occur in a 10 km wide zone of intense tectonic and magmatic activity.

Hydrothermal alteration has affected the Malanjkhand gmitoid. Alteration is stronger close to the mineralized veins. The alteration assemblages identified are potassic and propylitic. Potash metasomatism has produced K-rich zones close to mineralization. Pink granitoids contain higher amount of Fe₂O₃ compared to the gray granitoids. This is due to the presence of hematite introduced during potassic alteration. Alteration sequences and genetic models have been proposed, which can be used as guidelines for further exploration in the province.

Mineralization associated with the granitoids at Malanjkhand and elsewhere in the region is of porphyry type. Various characteristics such as tectonic regime, association of I-type calc-alkaline granitoids, hydrothermal alteration, stockwork of mineralized veins, strong structural control, temperature of formation, huge tonnage and low tenor are features akin to various porphyry deposits of the world, especially those associated with plutonic rocks.

Keywords

Copper, Molybdenum, Gold, Metallogeny, Malanjkhand, Porphyry Copper, Madhya Pradesh.

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A. K. Chaudhuri ¹, A. B. Pal ¹

Affiliations
1 Dept. of Geology & Geophysics, Indian Institute of Technology, Kharagpur, West Bengal, IN

Abstract

Precambrian metasediments in the northern part of the Gangpur Series, represented by mica schist, phyllite-slate, and schistose quartzite have been investigated over an area of 50 sq km around Lase (22°21' ; 84°45') of Sundargarh district, Orissa. Structural analysis reveals that the earliest folds in bedding (S₁) were reclined in nature, but they have been blurred by the profuse development of axial plane schistosity (S₂). S₂, however, shows upright to slightly overturned folds plunging moderately to E to ESE. The most dominant attitude of S₂ nearly normal to the regional fold axis points to the reclined geometry of the folds in S₁. Non-penetrative fracture cleavage surfaces (S₃) have developed parallel to the axial planes of S₂-folds, generally displacing the folded segments. The S₃-surfaces, however, show appreciable fanning.

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A. K. Chaudhuri ¹, A. B. Pal ¹

Affiliations
1 Department of Geology & Geophysics, Indian Institute of Technology, Kharagpur 721302, IN

Abstract

Shape analysis of a large number of pebbles from a 60 km stretch of the basal Raghunathpalli conglomerate in the Gangpur Group in eastern India, indicates that a flattening strain on originally constricted pebbles during the earliest folding episode gave rise to the present shape of the pebbles. The longest and the intermediate axes of pebbles lie invariably on the schistosity developed parallel to the axial planes of the earliest isoclinal folds. Though the Gangpur Group shows a remarkable multideformation plan, the pebbles show mainly the effects of the earliest deformation.

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A. K. Chaudhuri ¹, A. B. Pal ¹, A. Roy ¹

Affiliations
1 Department of Geology and Geophysics, Indian Institute of Technology, Kharagpur-721302, IN

Abstract

Three phases of folding have been detected in a large exposure along the Sapai lladi near Amaidegri (22°01': 84°08') in the Ghoriajhor manganese belt in the western part of the Gangpur Group. Reclined to inclined folds (F₁) plunging SSE have been coaxially refolded by open upright F₂ folds, and finally, upright folds with ENE-trending axial planes (F₃) cause culmination and depression of axes of open-folded reclined folds. The multiple deformations cause characteristic outcrop patterns and they are reflected in two distinct S-pole girdles around a plane of symmetry which is the axial trend of F₃ folds.

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A. K. Chaudhuri ¹, A. B. Pal ¹

Affiliations
1 Department of Geology and Geophysics, Indian Institute of Technology, Kharagpur 721 302, IN

Abstract

Gangpur Group, an important Precambrian metasedimentary sequence near Rourkela in eastern India shows an easterly antiformal closure, but the northerly younging towards the core shown by cross beds in the southern limb proves large scale inversion. Three generations of folds F₁, F₂ and F₃ are proved on mesoscopic and macroscopic scales by structural analysis. The limbs and axial planes of low easterly plunging isoclinal reclined folds (F₁) along with schistosity developed parallel to these axial planes are coaxially folded by upright F₂ folds; N-S trending upright F₃ folds cause culminations and depressions in axes of F₁ and F₂ folds. The stratigraphy of the complexly folded Precambrian Group is worked out on the basis of the structural model. One important marker horizon of carbonaceous quartz phyllite and banded quartzite recurs four times because of large scale axial plane folding.

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M. M. Bhargava ¹, A. B. Pal ¹

Affiliations
1 Hindustan Copper Limited, P.O. Malanjkhand-481116, Madhya Pradesh, IN

Abstract

The Malanjkhand ore body consists of rnineralised quartz veins, mainly of two generations, emplaced in altered and silicified granitoids. Hypogene wall rock alteration includes silicification, potassic alteration, chloritisation and biotitisation, Sassuritisation and sericitisation of plagioclase are common. Hydrothermal alteration has modified the composition of granitoids. Oxidation and supergene enrichment have resulted in distinct supergene mineral zoning. Leached zone, supergene oxide zone and supergene sulphide zone have been identified. Supergene enrichment has increased >22% copper in the supergene sulphide zone. Localisation of copper in the deposit is related to intensity of fracturing in Stage-II veins as well as volumetric proportion of the silicified granitoid patches. The ore body contains >2000 ppm Mo on the northern side. Mo mineralisation is independent of copper concentration. Gold and silver show positive correlation with copper. The mode of occurrence of sulphide mineralisation suggests its genesis under variable hydrothermal conditions. The localisation of quartz veins in long and narrow zones as well as limited hydrothermal alteration suggests that fluids must have followed permeable zones provided by the sheared and fractured granitoids.

Keywords

Economic Geology, Porphyry Copper Deposit, Malanjkhand, Madhya Pradesh.

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A. B. Pal ¹, G. L. Sindhupe ²

Affiliations
1 Hindustan Copper Limited, Khetri Copper Complex, Khetrinagar - 333 504, IN
2 Hindustan Copper Limited, Malanjkhand - 481 116, IN

Abstract

Age old gold panning along the streams, ancient workings for gold mineralization in the quartz veins emplaced in Malanjkhand granitic pluton (MG) along the peripheral contacts of older rocks of Amgaon Gneiss (AG) and Nandgaon Volcanics (NV) besides shear controlled zones drew the attention of present authors to take up detailed survey. These quartz veins are the locales for future exploration of copper-gold mineralization. Garhi Dongri (Gd) and Khandapar (Kdp), occuring at the peripheral contacts, may be gold rich and copper poor in mineralization and are very significant Gidori (Gd) and Pipardhar (Pd) areas, falling within sheared zones, may be considered as prospective sites for Malanjkhand-type rich copper and poor gold mineralization. Shitalpani(Stp) and Kundikasa(Kd) may fall under poor copper and/Or poor gold categories. GD prospect is found to be a promising for gold mineralization. Stp is under investigation and preliminary results suggest that it may be a poor-copper(?) prospect. Mineralogical association and alterations in GD and Stp are very similar to mineralogical alterations at Malanjkhand porphyry copper deposit. Gold rich and gold poor deposits are known in the northern chilean belt of porphyries and many other porphyry deposits.

Keywords

Gold Mineralization, Malanjkhand Porphyry Copper Deposit, Garhi Dongri Prospect, Madhya Pradesh.

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A. B. Pal ¹, G. L. Sindhupe ²

Affiliations
1 Hindustan Copper Limited, Khetri Copper Complex, Khetrinagar - 333 504, IN
2 Hindustan Copper Limited, Malanjkhand, Balaghat - 481 116, IN

Abstract

The use of indicator plants and plant organs have been considered as a tool for mineral exploration as early as in eighth century. In the present paper, the data on the biogeochemical studies of the plants growing in three copper prospecting areas of Madhya Pradesh are presented. The areas are near Gidori, Pipardhar and Garhi Dongri villages within Malanjkhand granitoid, situated to the south of Malanjkhand porphyry copper deposit. Nineteen plant species abundant in these areas were chosen for chemical analysis of their organs for copper. Analyses indicated that Jangli Tulsi (Hyptis suaveolens, (L.) Poit) plant, with their stunted growth, act as an indicator plant for copper rich soil. High copper concentration in some of their organs are observed. Kurlu tree (Sterculia urens, Roxb ) is found to be a good metal accumulator plant among others for base metal exploration. These observations can help as a supplementary guide for exploration of copper and other metals in this vast soil covered area.

Keywords

Copper Mineralization, Indicator plants, Biogeochemistry, Malanjkhand, Madhya Pradesh.

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K. L. Rai ¹, H. K. Pandey ², A. B. Pal

Affiliations
1 Department of Geology, Government Engineering College, Raipur - 492 010, IN
2 Central Ground Water Board, State Unit Office, Allahabad, U.P., IN

Abstract

No Abstract.

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Santosh Kumar ¹, Vikoleno Rino ¹, A. B. Pal ²

Affiliations
1 Department of Geology, Kumaun University, Nainital - 263 002, IN
2 Hindustan Copper Limited, Malanjkhand, Balaghat - 481 116, IN

Abstract

The Cu(±Mo±Au) hosting Malanjkhand granitoids (MG, -2400 Ma) represent Palaeoproterozoic felsic magmatism in Central India, which constitute part of the Bundelkhand Protocontinent. The enclaves hosted in MG can be classified broadly into two categories (1) Microgranular enclaves (2) Country-rock xenoliths. The microgranular enclaves (ME) are mesocratic to melanocratic, fine to coarse grained, porphyritic and commonly showing typical igneous textures. Field and microstructural evidences of ME and MG suggest the interaction between coeval enclave (mafic) and granite magmas. Modal compositions of ME are mostly granodiorite, quartz monzodiorite and monzogranite, whereas MG belong to quartz monzodiorite and monzogranite both being related to the calc-alkaline granodiorite (medium-K) series but evolve into the field of granitoids generated by crustal fusion. The primary enclave magma generating various ME can be represented by a ME (SiO₂=48.58, MgO=8,59 and Fe₂O₃-15.15 wt%), geochemically similar to calc- alkaline basalt. On various bi-variate geochemical plots MG and ME show a wide compositional variation suggesting mixing of enclave and granite magmas. On a multicationic R₁-R₂ plot the tie lines joining the ME and respective host MG suggest that sufficient chemical disequilibria exist between them. Using experimental melt compositions in terms of Si02 and K20 contents, the MG melt is likely to be derived from a tonalitic source, which subsequently experienced fractional crystallization, evolving within a high-K calc-alkaline field, whereas the ME plot in various fields suggesting the involvement of magma-mixing phenomena and to a certain extent potassium migration leading to a different degree of chemical disequilibria with their host MG, rather than crystal-liquid separation. Contents of selected trace elements (Ni, Rb, Sr, Y, Zr) of few pairs of ME-MG suggest partial to complete equilibration between them. However, Ti and Y contents, closer to primitive mantle, are indicative of mantle contribution to the source rocks from which ME and MG are derived.

Keywords

Palaeoproterozoic Granitoids, Microgranular Enclaves, Typology, Geochemistry, Magma-Mixing, Malanjkhand, Madhya Pradesh.

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