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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.
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