Volume 7, Issue 11, November – 2022 International Journal of Innovative Science and Research Technology

ISSN No:-2456-2165

Geochemical Exploration New Solution to an Old

Problem: Identification of Gold Mineralized Zones
Vishnu Kumar Singh*
Geological Survey of India, State Unit: Andhra Pradesh, SR, Hyderabad – 500068
* Corresponding Author

Abstract:- Veins and pegmatite are suitable carriers for II. GEOLOGY OF THE STUDY AREA
the mineralization of several elements such as Au(gold),
Silver(Ag), Cu( copper) etc. in this paper we will discuss The area is occupied by the rocks of Khondalite,
the REE and Gold mineralization in the korukonda area Charnockite and Migmatites Groups of Eastern Ghats
nearby to Rajahmundry, Andhra Pradesh. Here pegmatite Supergroup in the north, overlain by Tirupathi Formation of
was the rich source of REE, Graphite and quartz vein East Coast / Gondwana of Gondwana Supergroup, Deccan
intruded within the Migmatite gneiss could be a potential Trap, Rajahmundry Sandstone towards southern part and
source of Au(Gold). The values of Rare Earth Elements Krishna-Godavari Formation towards southwest The
(REE) from Lanthanum (La) to Lutetium (Lu) are Khondalite Group is represented by khondalite, which occupies
exclusively higher concentration in the eastern and North- the northern part of the area. Khondalite is observed around
eastern parts of the area, The value of LREE Ranges Mellisala, Gopalpuram and Tirumalayyapalem. It is chiefly of
from143.25 ppm to 2042.75 ppm, and HREE ranges from garnet-sillimanite + graphite gneiss and contains a few thin
9.09 to 27.37 ppm. the maximum value of Au(gold) impersistent bands of quartzite at places. Intermediate
observed is around 47 ppb in stream sediments which charnockite and hypersthene granite/acid charnockite
indicates moderate enrichment of Au (Gold) in the study comprising the charnockite Group occur as minor bodies. The
area . Migmatite Group is made up of garnetiferous quartzo
feldspathic gneiss and manganiferous quartzo-feldspathic
Keywords:- REE (Rare Earth Elements ), Rajahmundry, rocks which are derived from the former due influx of quartzo
Migmatite , Veins, Pegmatite,Ppm(Parts Per Million), feldspathic injections and observed near Rajavaram, korukonda
Ppb(Parts Per Billion) and Srirangapatam.

I. INTRODUCTION

The area is bounded by latitude N 17° 00’ 00” to 17° 15’

00” and longitude 81° 45’ 00” to 82° 00’ 00” E. covers the
upland area North of Godavari delta in East Godavari District
of Andhra Pradesh. It is well connected by a metalled road. The
higher values of LREE are recorded over pegmatites intruded
within Manganiferous (Migmatite) gneiss, at the contact of
Basalt & Tirupathi Sandstone and garnet-sillimanite gneiss in
the area. It varies from 143.25 ppm to 2042.75 ppm with
median values of 643.26 ppm. The threshold values for LREE
is 1195.39, whereas HREE is varies from 9.09 ppm to 27.37
ppm with median values of 16.87 ppm. The threshold values
for HREEs is 23.08. The elevated values obtained might be due
to the weathering and leaching of Pegmatite and gneisses in the
area. The higher concentrations of REE suggesting that
gneisses and Pegmatite are the source rocks for REE. It is
observed that LREE content is comparatively more than the
HREE. Gold(Au), Tellurium (Te), selenium(Se) ,Bi(Bismuth), Fig 1: Geological Map of Study Area ( Source :
Antimony(Sb) and Silver show moderate level of enrichment, Geological survey of India )
which indicates that gold and silver might be available in the
pegmatite and quartz vein in form of selenides and tellurides

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Volume 7, Issue 11, November – 2022 International Journal of Innovative Science and Research Technology
ISSN No:-2456-2165
III. MATERIAL & METHOD assigning weights. The advantage of IDW-generated
interpolated raster surface in exactly restricted to lowest &
194 Soil samples were collected as per the NGCM highest values, but statistically generated kriging surface is
program of the Geological survey of India field season 2018- restricted to the values which are above the available lowest
19 , Chemical Analysis of the Sample was done by the values and much below the actual highest values. Therefore,
Chemical Division, Southern Region Hyderabad anomaly zone/threshold values generated by box plot
500068.Spatial Analytical techniques were used to prepare the sometime do not fall within the limit of Krigging surface
geochemical distribution of elements of elements and the
environment for Spatial and statistical Analysis was GIS
IV. RESULT & DISCUSSION
A. Statistical Methods
Gold (Au), Bismuth(Bi) and Antimony (Sb): values of
 Univariate Statistical Analysis gold .bismuth and Antimony are quite encouraging in the
The univariate analysis explores each variable in a data chemical result of stream sediment highest value of gold
set, separately. It looks at the range of values, as well as the observed nearby kolavacherla and thima puram which is
central tendency of the values. It describes the pattern of around 0.05 ppm due to sieving process by 120 mesh sieve .
response to the variable. It describes each variable on its own. the value of gold diminished. the higher value of gold observed
Univariate analysis commonly involves reporting measures of over the pegmatite and quartz veins of migmatite gneiss group
central tendency. This involves describing the way in which of eastern ghat super group and at the contact of Deccan basalt
quantitative data tend to cluster around some value. In and Tirupathi sandstone. Same way the value of Bi and Sb
univariate analysis, the measure of central tendency is an anomalous values fall around the kolavacherla and its
average of a set of measurements, the word "average" is surrounding which indicate that the area around the
variously construed as (arithmetic) mean, median, mode, or kolavacherla and its surrounding have the potential for gold
another measure of location. The descriptive statistics function mineralization
of MS Excel was used to find the univariate statistic containing
the number of samples or count (n), minimum value, Silver (Ag): silver values of stream sediments and slope
maximum value, mean, median, mode, standard deviation, and wash shows moderate enrichment in the area since the samples
skewness. The mean, median, and mode values are compared were sieved by the 120 mesh size sieve the values got
to have a theoretical assessment of the normality in the diminished. The highest value of Ag observed was 0.17 ppm
distribution of elements. In case, skewness was found to be which shows around 3 times Enriched then the continental
high, histograms were prepared for those elements, using crust over the quartz and pegmatite veins of Migmatite group
geostatistical values of rocks and laterite of Rajahmundry sandstone

 Bi-variant Statistics Rare Earth Element (REE)

The bivariate analysis involves the analysis of two
variables (often denoted as X, Y), for the purpose of LREE: The higher values of LREE are observed over
determining the empirical relationship between them. In order Manganiferous gneiss and garnet sillimanite gneiss in the area.
to see if the variables are related to one another, it is common It varies from minimum value 143 ppm to maximum value is
to measure how those two variables simultaneously change 2042 ppm with median values of 643.26 The threshold values
together. Common forms of bivariate analysis involve creating for LREE is 1195.39 ppm. The elevated values obtained might
a percentage table or a scatter plot graph and computing a be due to the weathering and leaching of Pegmatite and
simple correlation coefficient. The correlation matrix is gneisses in the area. The higher concentrations of REE over
prepared by using the correlation function of MS Excel lithology suggesting that gneisses and Pegmatite are the source
rocks for REE, which is evident from the analytical results and
The software used for the analysis is MS-EXCEL and elemental distribution maps
Arc GIS. The statistical table for each element is attached with
their respective elemental distribution maps. The term
univariate statistics is commonly used in statistics to HRRE: HREE varies from minimum value 9.09 ppm to
distinguish a distribution of one variable from a distribution of maximum value is 23.37 ppm with median values of 16.87
several variables. Univariate analysis is commonly used in the ppm The threshold values for HREE is 23.08 ppm it was
first stage of analysis of the data at hand, which include observed that LREE content is comparatively more than the
descriptive statistics, histogram, and box plot. HREE content which may be due to low concentration of high
field strength elements (HFSE) in Pegmatite and gneisses
 Inverse Distance Weighting (IDW) present in the area.
It is a type of deterministic method for multivariate
interpolation with a known scattered set of points. The
assigned values to unknown points are calculated with a
weighted average of the values available at the known points.
The name given to this type of methods was motivated by the
weighted average applied, since it resorts to the inverse of the
distance to each known point ("amount of proximity") when

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Volume 7, Issue 11, November – 2022 International Journal of Innovative Science and Research Technology
ISSN No:-2456-2165
Table 1: Correlation matrix of Bi-Au-Sb-Hg elements

Hg(ppb) Au (ppb) Sb(ppb) Bi(ppm)

Hg(ppb) 1
Au (ppb) 0.00618 1
Sb(ppb) -0.006 0.144795 1
Bi(ppm) 0.008358 0.162949 0.871686 1

Table 2: Descriptive statistics of LREE and HREE

Parameters LREE HREE
Mean 685.83 16.86
Standard Error 26.09 0.22
Median 643.26 16.87
Standard Deviation 363.46 3.11
Sample Variance 132103.86 9.69
Kurtosis 0.45 0.83
Skewness 0.72 0.25
Range 1899.51 18.29
Minimum 143.25 9.09
Maximum 2042.75 27.37 Fig 2: Geochemical map of Heavy Rare Earth Elements
Mean+2sd 1412.76 23.08 (HREE) over the Lithology map of the study area

Table 3: Correlation matrix of LREEs & HREEs lanthanide series

LREE La Ce Pr Nd Eu Sm Gd
La 1.00
Ce 1.00 1.00
Pr 0.99 0.99 1.00
Nd 0.98 0.99 0.99 1.00
Eu 0.72 0.71 0.68 0.69 1.00
Sm 0.99 0.99 0.99 0.98 0.72 1.00
Gd 0.98 0.97 0.97 0.96 0.72 0.99 1.00
HREE Tb Dy Ho Er Tm Yb Lu
Tb 1.00
Dy 0.74 1.00
Ho 0.30 0.85 1.00
Er 0.42 0.84 0.92 1.00
Tm -0.01 0.57 0.86 0.89 1.00
Yb 0.01 0.55 0.83 0.88 0.99 1.00
Lu -0.06 0.48 0.79 0.81 0.95 0.98 1.00

Very strong Correlation

Strong Correlation

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Volume 7, Issue 11, November – 2022 International Journal of Innovative Science and Research Technology
ISSN No:-2456-2165

Fig 3: Geochemical map of Light Rare Earth Elements Fig 6: Geochemical map of Gold (Au) over the Lithology
(LREE) over the Lithology map of the study area map of the study area

Fig 4: Geochemical map of Cerium (Ce) over the Lithology

Fig 7: Geochemical map of Silver (Ag) over the Lithology
map of the study area
map of the study area.

Fig 5: Geochemical map of Lanthanum (La) over the Fig 8: Anomalous zones of Au(gold), Se(selenium) and Te
Lithology map of the study area (tellurium) over the Lithology map of the study area

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Volume 7, Issue 11, November – 2022 International Journal of Innovative Science and Research Technology
ISSN No:-2456-2165
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