Remote Sensing Division, GSI, WR, Jaipur. Page 1

Discovery of Copper deposit at Mundiyawas-Khera area of Alwar Basin, North

Delhi Fold Belt has opened scope for base metal search in the basin. The semi-arid

climatic condition resulting in poor vegetation cover along with the presence of good

surface exposure of the litho-units favours the use of remotely sensed data in locating

extension of this mineralized zone. In the present study, an attempt has been made to

identify favourable locales of base metal mineralisation by integrating the spectral

signatures derived from satellite data with available geochemical and geological

databases.

Geological and structural map of the study area has been updated with the help

of available database of GSI, spectral signature derived from satellite data followed by

field validation. The satellite data used for the present work include ASTER-L1T, IRS R2

LISS IV, Cartosat-1, Landsat 8, OLI (DN and surface Reflectance data) and Landsat 7

ETM. Various spatial and spectral enhancement (PCA, MNF, OIF & Band ratio)

techniques have been carried out in the satellite data to derive spectral signatures of

litho-pack which host mineralisation in the Mundiyawas-Khera block. Principal

component analysis and band rationing has been carried out to identify illite, alunite,

kaolinite & iron oxide rich alteration zones. A prominent hydrothermal alteration zone is

identified (Fig.1) with the help of ASTER PC image and it extends from Ajabgarh (TS

54A/8) to Biharisar which is north of Thanagazi (54A/7). It has an approximate length of 26

km and width of 3 km to 8 km and roughly shows a N-S trend. The known Mundiyawas-

Khera prospect fall well within this zone. The zone of hydrothermal alteration identified

during the present study follows the trend of the major lineament (NNE-SSW) observed in

the study area. The WNW-ESE trending lineament derived from drainage divide, which is

otherwise not traceable in the flat terrain, cross cuts this major NNE-SSW trending lineament

to the north of Mejorh. Numbers of old workings are observed in the vicinity of this

lineament e.g. around 1 km NE of Gurah Kishoridas (near Angari) and around 1.5 km east of

Shyampura. In these old workings, surface manifestation of mineralisation (malachite stain)

is observed within the quartz vein and tremolite bearing dolomitic marble, which is the

Remote Sensing Division, GSI, WR, Jaipur.

IDENTIFICATION OF NEW FAVOURABLE LOCALES OF BASEMETAL MINERALISATION IN ALWAR BASIN, RAJASTHAN.

Remote Sensing Division, GSI, WR, Jaipur. Page 2

country rock. Similar hydrothermal alteration zone is also observed in and around Kundla in

54A/8, it shows a rough NE -SW trend from Uparla Guwarla (54A/8) to Dhamrer (54A/11).

The geochemical data pertaining to Degree sheet 54A has been processed and

multivariate analysis has been carried out to find out oxides/ trace element that show a

positive /negative correlation with base metal distribution in the area. The study reveals that

Cu has positive correlation with Bi (Correlation Coefficient: 0.48), Ni (CC: 0.38), Se (0.37),

Fe2O3 (0.35), Co (0.35), As (0.31), V (0.30), TiO2 (0.27), MgO (0.26) and MnO (0.25). It has

negative correlation with SiO2 (-0.23) & Na2O (-0.20). The analysis further reveals that MgO

/ K2O enriched areas in the study area roughly coincide with Na2O depleted areas and these

zones coincide with alteration zone brought out by satellite data. This alteration zone (Fig.1)

linked to hydrothermal activity has been brought out clearly by RGB composite PCA (-PC4

(1234), PC4 (1346), 3/2) image.

Figure: 1.

Remote Sensing Division, GSI, WR, Jaipur. Page 3

The processed satellite data products were integrated with geochemical, geological

and lineament database in GIS platform to identify promising areas for detailed mineral

exploration study. Three promising areas identified for detailed mineral exploration study

through the present work are Mejorh, Kundalka (Fig.2) and Amra-Ka-Bas (T.S: 54A/7 & 11).

Two more promising areas for base metal exploration are identified in the adjoining area

through the present work and are around Basi (54A/4) and around Kundla (54A/8). Field

study followed by petrographic analysis reveals that the felsic volcanic rock host

mineralization in the newly identified areas (Mejorh, Amra-Ka-Bas and Kundalka). High

incidence of Ba and Zr in the bed rock samples collected from the study area is attributed to

the presence of felsic volcanics. Petrochemical study reveals that the felsic volcanics hosting

sulphide mineralization in the above-mentioned areas fall in Rhyolite / Dacite field and

appears to be similar to the host rock of Mundiyawas-Khera prospect.

Epigenetic phase of mineralisation is also observed in the field wherein the

hydrothermal fluid might have scavenged the primary ore and deposited along with later

formed quartz-carbonate veins.

Figure: 2.

Remote Sensing Division, GSI, WR, Jaipur. Page 4

Figure: 3. Quartz-carbonate vein showing malachite stain near Rup-Ka-Bas.

Ore petrographic study reveals that in the newly identified promising areas,

association of the ore mineral (Chalcopyrite) with other sulphide phases (Pyrrhotite,

Arsenopyrite and Pyrite) are similar to that of Mundiyawas-Khera deposit (Fig.4). Sulphide

specks collected from the surface samples of volcanics at Mejorh, Kundalka and Amra Ka

Bas reveals that Pyrrhotite is the major sulphide phase which contains fine to coarse

disseminations, specks and stringers of chalcopyrite. They exhibit mutual straight boundary

as well as embedded relationship with each other indicating crystallization of the minerals

from the same fluid for a longer duration of time. Colloform texture is observed in some of

the sections from Amra-Ka-Bas where early formed pyrrhotite is being replaced by pyrite and

this most likely indicates presence of relatively low temperature hydrothermal fluids.

Strong lithological control, nature of occurrence of the sulphide grain and its

association with volcano sedimentary rocks are indicative of the fact that primary

mineralisation may be of VMS type.

Figure: 4.