The same is true with zinc, although it shows a
relatively moderate contrast level in the water of the
mineralized zone (Table 3). Th e average level of zinc in
well water near the uranium orebody is 60.2 µg/L, which
contrasts moderately with the average value of water
derived from barren sites (29.3 µg/L, Table 3).
7 Novel Hydrogeochemical Discrimination
Diagram
The new approach for hydrogeochemical exploration for
uranium in arid regions is mainly based on the use of cost
effective and rapidly recognized hydrochemical guides to
locate the orebody (El-Rayes 2010). In this study, the
statistically analysed hydrogeochemical and other ancillary
geological data revealed that there is a strong correlation
between Mg 2+, TDS and uranium occurrences. The
decrease of Mg 2+ content in the groundwater of the study
area constitutes a very important guide in the search for
uranium mineralization in west central Sinai. The
extremely low Mg2+ values are recorded in waters derived
from wells draining the radiometrically high anomalous
zone. The Mg 2+ depletion may be attributed to the
dolomitization and dedolomitization processes that act on
different lithological units (Mansour, 1994). These
secondary processes lead to alterations of the parent rocks
as in the dolomitization of the pre-existing limestone in
hyper-saline lagoons (Strakhov, 1958). The bases of these
hyper-saline lagoons are form ed of carbonaceous shale
with high uranium content which plays its role in the U-
enrichment during the process of dolomitization. The
prevalence of the carbonate anions is suitable for the
presence of the di-uranyl tri-carbonate anionic solution
complex [UO2(CO3)3]4- (Smith et al., 2009). This di-uranyl
tri-carbonate anion accompanies the MgCO 3 needed for
dolomitization. Wright (1977) mentioned that the ore in
Australian U-deposits is found only in rocks that have been
chloritized through the regional addition of Mg 2+.
Groundwater constitutes the ultimate source of Mg 2+
needed for the secondary processes of dolomitization and
chloritization. The low Mg 2+ in U-mineralized waters
implies that Mg 2+ is removed from water in contact with the
uranium orebody and consumed in dolomitization and
chloritization of the uranium-bearing rocks. This result is
used to build up a new hydrogeochemical discrimination
diagram which could be used as a quick and cost-effective
exploration tool in the search for uranium deposits in
environmentally similar areas. The median Mg 2+
concentration level in groundwater samples ranges from 3.5
meq/l (for mineralized water) to 6.7 meq/l (for non-
mineralized water). To show the validity of using the low
Mg2+ concentration as an expl oration guide for uranium
mineralization, the Mg 2+ content of water samples is plotted
against the total dissolved solids for the collected samples
(Fig. 16). Samples derived from wells adjacent to the
radiometrically high anomalous zone (N-2, N-3, H-5 & H-
2) exhibit a positive and steep regression line on this plot.
This line is recognized as the U-mineralized water line.
Water derived from barren sites falls on another relatively
gentle sloped regression line intersecting the previously
mentioned line and recognized as the non-mineralized water
line. The high slope of the U-mineralized water line reflects
the removal of Mg 2+ from water by uranium minerals as the
TDS increases significantly.
Water samples plotted on the lower part of the U-
mineralized water line (below the intersecting point (Fig.
16) indicate the presence of a stronger uranium orebody
along the flow path of these waters. In this regard, and
based on the results of the present study, the sample of well
number H-3 indicates a new strong anomaly of uranium
mineralization confirmed for the first time by the present
study. This well (H-3) drains an area extending westward
outside the mapped area towards the western flank of Wadi
Baba, at which a new uranium occurrence may be found.
More attention should be paid to this zone in future
geological and geochemical surveys. Water samples with a
relatively high Mg2+ content and plotting on the upper part
of the U-mineralized water line (above the intersection
point) reflect the mixing between mineralized and non-
mineralized, Mg-rich waters. Sample No. H-2 is a good
example of such a type of mixing (Fig. 16).
8 Conclusions
The results of regional hydrogeochemical exploration
for uranium occurrences in the west central Sinai area
Fig. 16. Hydrogeochemical discrimination diagram for
uranium-mineralized groundwater in the west central
Sinai, Egypt.
indicates that the groundwat er affected by uranium
mineralization has similar major ion relativity expressed
essentially as SO 4>Cl>HCO3 and, to a lesser extent, as
Cl>SO4>HCO3. These relativities are associated with low
magnesium content as a rule and constitute a signature of
uranium mineralization when expressed as Schoeller plots.
Possible pathfinder elements associated with the
uranium ore of west central Sinai include low Mg 2+, SO4
2-,
V, Zn and Ni. The low magnesium content is the most
effective hydrogeochemical indicator of uranium minerali-
zation in the west central Sinai area.
The positive anomalies of the immobile trace elements,
including Ni, Fe and Zn are strongly distributed close to
the uranium orebody. Conversely, the relatively mobile
trace elements, including Co, U, V and Cr have
significantly anomalous values in water as they have been
leached far away from the uranium orebody.
Statistically analysed hydrogeochemical and other
ancillary geological and geophysical data reveal that there
is a strong correlation between both low Mg 2+ and total
dissolved salts (TDS) of groundwater and the uranium
occurrences. This result is used to build up a new
hydrogeochemical discrimination diagram which could be
used as a graphical exploration tool in the search for
uranium occurrences in west central Sinai..
Based on the obtained results, a new site for uranium
occurrence, west of W. Baba, is inferred and recom-
mended for future detailed geological and geochemical
studies. The proposed novel hydrogeochemical discrimi-
nation diagram is recommended to be used as a quick and
cost effective exploration tool in the search for uranium
ores in environmentally similar arid areas around the
world.