Using groundwater chemical and isotopic composition in the search for base metal deposits: hydrogeochemical investigations in the Hinta and Kayar Pb–Zn districts, India

Patrice de Caritat, D.C. McPhail, Kurt Kyser and Christopher J. Oates
Geochemistry: Exploration, Environment, Analysis, 9, 215-226, 21 July 2009, https://doi.org/10.1144/1467-7873/09-206

Abstract

ABSTRACT As part of mineral exploration campaigns carried out by Anglo American plc in India, groundwater samples were collected from over 200 wells in the Hinta and Kayar sedimentary exhalative base metal districts to evaluate the usefulness of hydrogeochemistry in mineral exploration. Mineralization occurs here mostly as Pb and Zn sulphides in metamorphic silicic–felsic and carbonate basement rocks. Groundwater chemical and isotopic data from 27 wells at Hinta and 181 wells at Kayar were interpreted using major element concentrations, their ratios to a conservative element (e.g. Cl−), isotope systematics and thermodynamic modelling. The results indicate that the following processes take place: evaporation, evapotranspiration, water–regolith–rock interaction (e.g. weathering of carbonate, silicate, and sulphate or sulphide minerals) and water mixing. Certain gradients, rather than absolute values, may reflect proximity to mineralization; these include: (1) concentrations of ore and related elements normalized to a conservative element (e.g. Zn/Cl− molar ratios from 1 × 10−7 up to 2 × 10−2; SO42 − /Cl− molar ratios from 1 × 10−5 up to 3.3); (2) isotopic ratios (e.g. δ34S from +23 down to +5‰ V-CDT, with two samples at −5‰); (3) saturation indices for ore, alteration or secondary minerals (e.g. SIjarosite from −15 up to zero). Hydrogeochemistry may be a useful tool to help vector toward ore deposits in deep or covered settings.

KEYWORDS

INTRODUCTION

Historically, regions with outcropping or subcropping bedrock have been the primary focus of the attention of mineral explorers. As developing nations strive to attain higher living standards, the demand for mineral resources is likely to grow over the foreseeable future. Consequently, the attention of active explorers is now increasingly turning to areas of (significant and/or complex) regolith cover where the bulk of the undiscovered deposits most probaby lie (e.g. Smith 1996; Closs 1997; Kelley et al. 2003, 2006; Hronsky & Groves 2008). These new frontier areas require a different set of exploration tools from traditional methods, or, at the very least, procedures that have been adapted to the particular challenges these areas pose, such as lack of outcrop, and overburden that may be thick, transported, weathered and/or altered.

Groundwater has the potential to interact with bedrock and any mineralization present at depth (Stumm & Morgan 1996; Domenico & Schwartz 1997; Drever 1997; Appelo & Postma 2005). Hydrogeochemical signatures develop through water–mineral interaction and dispersion haloes can form through diffusion and advection as groundwater flows from recharge areas to discharge zones, which can be hundreds of kilometres apart. Therefore, the crucial questions to address if hydrogeochemistry is to be applied to mineral exploration in this context are: Can groundwater acquire a chemical and/or isotopic signature (fingerprint) from mineralization? Can it retain that signature as it moves down the groundwater flow path? Can we recognize the signature when we sample groundwater close to and further down-flow from mineralization? Can we vector back to mineralization?

The present paper aims to make a contribution to answering these questions with two case studies from India. Ultimately, the answers and generalized principles (models for exploration) will come from distilling results from a number of case studies carried out around the world (e.g. Cameron 1978; Jiang et al. 1994; Taufen 1997; Leybourne et al. 1998; Gray 2001; Cameron et al. 2002; Pauwels et al. 2002; Carey et al. 2003; Phipps et al. 2004; Pirlo & Giblin 2004; Cameron & Leybourne 2005; de Caritat et al. 2005; Kelley et al. 2006; Leybourne & Cameron 2007). Such case studies are crucial also in establishing the sampling, analytical and interpretation protocols that are successful, cost-effective and practical for the mineral exploration industry.

STUDY AREAS

The present study focuses on hydrogeochemical investigations carried out around the base metal prospects of Hinta and Kayar in the State of Rajasthan ( Fig. 1), which holds c. 90% of the Pb and Zn reserves of India (Government of India Planning Commission 2007). The Hinta prospect (24°34′N, 74°11′E, c. 470 m above sea level (a.s.l.)) is located in southern Rajasthan c. 55 km ESE of Udaipur. The Kayar prospect (26°32′N, 74°41′E, c. 480 m a.s.l.) is located in central Rajasthan c. 11 km NNE of Ajmer.

Fig. 1
Fig. 1

Location maps of Rajasthan, northwestern India (main), and Hinta (a) and Kayar (b) study areas. Groundwater sample locations are shown (dots), as are inferred groundwater flow directions (arrows), on Google Earth™ images.

India has a population of c. 1 billion (2001 Census) and an average population density of 313 persons km−2 (Government of India 2008). Of the 56.5 million people of Rajasthan (average population density of 165 persons km−2), 77% live in rural areas, with implications for the use of natural resources, including the use and overuse of groundwater for drinking or irrigation water supplies (Srivastava et al. 2005). Temperatures in Rajasthan range from 8 to 28 °C in winter, and from 25 to 46 °C in summer; average rainfall ranges from c. 100 mm a−1 in the western deserts to 650 mm a−1 in the SE. Most rain falls from July to September during the monsoon season. Specific average rainfall figures for Udaipur (Hinta) and Ajmer (Kayar) are 858 mm and 602 mm, respectively. Drinking water in the Udaipur and Ajmer districts is mainly sourced from perennial rivers, non-perennial rivers during the monsoon season, and from shallow groundwater accessible through dug wells or tube wells (Raj Darpan 2008).

Recent overviews of the geology of Rajasthan were presented by Chakrabarti et al. (2004), Gupta (2004), Ray & Rao (2004) and Sinha-Roy (2004). Both Hinta and Kayar are part of the Proterozoic Aravalli–Delhi orogenic belt of central Rajasthan. The type of base metal mineralization in this belt is dominantly sedimentary exhalative (SEDEX) (Porwal et al. 2006), and this is the mineralization type found at both Hinta and Kayar. The most significant Zn–Pb–(Ag) deposit in the belt is Rampura Agucha (Höller & Gandhi 1995; Höller et al. 1996), a metamorphosed, stratiform, sediment-hosted deposit situated approximately halfway between Hinta and Kayar ( Fig. 2).

Fig. 2
Fig. 2

Simplified geological maps of central Rajasthan (main), and Hinta (a) and Kayar (b) study areas (Anglo American plc, unpublished data). G, Ghugra; H, Hinta; K, Kayar; RA, Rampura Agucha; U, unnamed deposit.

The Hinta area is located within the pre-Aravalli Supergroup Banded Gneiss Complex (Archaean) basement rock sequence (Roy & Jakhar 2002; Saini et al. 2006). The Hinta prospect is located on the eastern flank of a north–south-trending synform, which folds a sequence of metapelite, quartzite, graphitic schist, metacarbonate, metapsammite, amphibolite and gneissic metagranite. It is defined by several soil and bedrock Pb–Zn anomalies and a ground magnetic anomaly, all located near a NNE–SSW-trending shear zone (Anglo American plc, unpublished data).

The Kayar area is located within the NE–SW-trending Meso- to Neoproterozoic Delhi Supergroup belt (Roy & Jakhar 2002; Saini et al. 2006), which consists mainly of metapelite, metacarbonate and quartzite rocks. The Kayar prospect is hosted mainly in a thick package of thinly bedded pelites with subordinate interbedded fine-grained quartz–feldspar psammite, metacarbonate, minor amphibolite and pegmatite. Most of the sulphide mineralization occurs in variously graphitic pelites. The area also comprises the Ghugra prospect to the south of Kayar, as well as an unnamed prospect to the north (Fig. 2).

Based on topographic and satellite imagery (Landsat TM, Google Earth images), the groundwater at Hinta is interpreted to flow mainly in an easterly direction across the prospect, then towards the north (Fig. 1). In the larger Kayar study area, inferred flow directions are more variable (Fig. 1), but probably in a northwesterly direction at the Kayar prospect, and northeasterly at the Ghugra prospect.

METHODS

Anglo American plc obtained groundwater samples at both sites during fieldwork campaigns carried out in 2003 (Hinta) and 2004 (Kayar). Groundwater was accessed mostly via dug wells or tube wells, using a manual pump or, where unavailable, a bailer. Samples were filtered at 0.45 μm in the field using Pall Gelman ‘AquaPrep 600’ groundwater sampling capsules (USEPA compliant 600 cm2 Supor® hydrophilic polyethersulphone membrane in polypropylene capsule). The aliquots for cation analysis were acidified by addition of ultrapure 8M HNO3 to pH 2. Field duplicates were taken every 10 samples.

A total of 27 wells were sampled at Hinta, and 181 at Kayar. Field measurements consisted of determining water pH (rounded to 0.5 of a pH unit at Hinta), temperature (Kayar only), and electrical conductivity (EC).

The samples were analysed for anion concentrations by ion chromatography (IC) at the Geological Survey of Canada (GSC) laboratories, Ottawa, Canada; major element concentrations by inductively coupled plasma-emission spectrometry (ICP-ES) at the GSC; trace element concentrations by inductively coupled plasma-mass spectrometry (ICP-MS) at the GSC; and isotope ratios δ18O and δD of water, δ34S of dissolved SO42 − , and (at Kayar only) 87Sr/86Sr of dissolved Sr by mass spectrometry at Queen's University Isotope Laboratory, Kingston, Canada. Only a subset of samples from Kayar (n = 77) was submitted for isotopic analysis.

For the Hinta groundwaters, total inorganic carbon (TIC) was measured using a carbon analyser, from which dissolved HCO3− (alkalinity) was calculated assuming all TIC was present as HCO3− (a reasonable assumption for the water's pH range; Appelo & Postma 2005); ICP-ES data for S were used to calculate dissolved SO42 −  concentrations. Alkalinity or TIC was not measured for the Kayar groundwater samples, thus dissolved HCO3− was calculated from charge balance.

The quality of the analytical data was assessed using the results of several quality control measures, including the insertion of field and laboratory blanks, field and laboratory duplicates and certified reference materials (CRM) in the sample suites presented for analysis, and the calculation of charge balance for the Hinta samples (alkalinity having been determined by charge balance at Kayar). Results show that bias and precision were, for the vast majority of analytes, within 10%.

RESULTS

A statistical summary of the results for bulk properties, major cation, major anion and selected trace element concentrations, and isotopic ratios from the Hinta and Kayar groundwaters is shown in Table 1. The selected trace elements are those that relate to mineralization and/or may be expected to be fairly mobile under aquifer conditions (e.g. pH, salinity) at Hinta and Kayar, so as to potentially form a large footprint for exploration. In the following section, the results are interpreted with a view to determine the hydrogeochemical processes, including some related to potential mineralization, that affected the groundwater compositions.

View this table:
Table 1

Statistical summary of selected bulk parameters, major cations and anions, trace elements and isotopes for the groundwaters at Hinta and Kayar, northwestern India.

DISCUSSION

Bulk parameters

The relationship between EC and pH ( Fig. 3) shows that the Hinta groundwaters are both more dilute and more acidic than those from Kayar. Both areas have statistically significant (correlations cited in this paper are significant at the p > 0.99 level, unless otherwise indicated) trends of increasing EC with increasing pH (Hinta: r = 0.69; Kayar: r = 0.23), as expected when initially dilute and aggressive water reacts with minerals in soils and aquifers along its flow path. Some samples from Kayar have high pH values (up to pH 8.5–9), perhaps reflecting more protracted water–mineral interaction here, or a greater degree of carbonate dissolution. The Kayar samples also reach almost one order of magnitude higher EC values than Hinta ones, which may reflect increased evaporation, higher aeolian input of salts (no evaporitic units being known in either region), more extensive weathering and evolution, and/or older groundwaters at Kayar.

Fig. 3
Fig. 3

Electrical conductivity (EC) v. pH scatter diagram for Hinta and Kayar groundwaters. SW, average seawater.

Isotopes of O and H

At both Hinta and Kayar, the bulk of the δD and δ18O values fall close to, and to the right of, the local meteoric water line, and the remainder define linear trends with slopes lower than the local meteoric water line ( Fig. 4a). This is commonly interpreted to indicate that evaporation is an important control on the isotopic composition of the water molecules (e.g. Gat 1996). The groundwaters from Kayar intersect the local meteoric water line much lower than those from Hinta. Seeing that elevation of the two areas at present is similar and latitudinal separation is only c. 200 km, this difference is attributed to recharge under different conditions (palaeo-climate, palaeo-elevation, palaeo-latitude), consistent with the likelihood that the Kayar groundwaters are significantly older than those at Hinta, as mentioned above. The regression line of the isotopic data from Kayar has a lower slope (4.853; r = 0.98) than that from Hinta (5.473; r = 0.97). This lower slope at Kayar indicates that evaporation is more important here than at Hinta in controlling the stable isotope composition of H2O. This is consistent with the higher EC values observed for some of the Kayar samples.

Fig. 4
Fig. 4

(a) δD v. δ18O scatter diagram for Hinta and Kayar groundwaters, with their respective regressions lines shown as continuous (δD = 5.473 × δ18O −8.895, r = 0.97, n = 27) and dotted lines (δD = 4.853 ×δ18O −20.073, r = 0.98, n = 77), respectively. Indian Meteoric Water Line (IMWL) based on International Atomic Energy Authority data from New Delhi, Bombay and Shillong (Bhattacharya et al. 1985; Krishnamurthy & Bhattacharya 1991) shown as dashed line (δD = 7.2 ×δ18O +5.1). SW, average seawater. (b) δD v. Cl− scatter diagram for Hinta and Kayar groundwaters.

The diagram of δD v. Cl− concentration (Fig. 4b) indicates that evapotranspiration is also an important process taking place, particularly at Kayar. The trend shown by the Hinta waters is more consistent with mixing, with some evapo(transpi)ration also taking place.

Major cations and anions

A Piper diagram ( Fig. 5) shows that the groundwater types at Hinta are dominantly Na, trending to Na–Ca–Mg, and HCO3− trending to HCO3−–Cl−. Groundwater facies at Kayar are similar in their cation make-up, but the anions are more dominated by Cl−. In neither case is SO42 −  a major anion relative to Cl− and HCO3−. The major ion make-up of the groundwaters reflects the different major lithologies interacting with groundwater at each site; namely, dominantly carbonate rocks at Hinta (composition trending toward the Ca–HCO3− apex) and a mixture of carbonate and silicic–felsic rocks at Kayar (toward the Na–Cl− apex). In light of this, the higher pH and EC values recorded for some Kayar samples (see Bulk parameters section above) are more likely to reflect longer water–mineral interaction than carbonate dissolution.

Fig. 5
Fig. 5

Piper diagram for Hinta and Kayar groundwaters. SW, average seawater.

The relationships between Na and Cl− ( Fig. 6a) show that (1) the Hinta groundwaters are much fresher than those from Kayar (consistent with comments above), (2) the bulk of the more saline groundwaters (>10 mmol l−1 Cl−) fall on or near the seawater dilution line, and (3) most waters, especially the more dilute ones, have an excess of Na relative to Cl− (compared with the seawater dilution line). As there are no known evaporitic units in the study areas, and because few other minerals contain high amounts of Cl− that could form a sink for Cl−, this relative Na enrichment (molar Na/Cl up to 13) is probably caused by the addition of Na; for instance, through mineral weathering (e.g. incongruent dissolution of Na-bearing plagioclase) when the recharging waters are most dilute and acidic. Subsequently, Na is lost to solution presumably by cation exchange (e.g. Na in solution displaces Ca in exchangeable sites of clay minerals) before the waters undergo much evapo(transpi)ration, otherwise the Na/Cl would remain high at higher salinities. The older, more concentrated waters have molar Na/Cl closer to unity.

Fig. 6
Fig. 6

Na v. Cl− (a) and SO42 −  v. Cl− (b) scatter diagrams for Hinta and Kayar groundwaters. Dashed line represents seawater ratio. SW, average seawater.

The groundwaters show a greater scatter in terms of Cl− and SO42 −  compositions (Fig. 6b), particularly in the case of Kayar. Nearly all the Hinta groundwaters show an excess of SO42 −  relative to Cl−, which is more probably caused by the addition of SO42 −  through mineral weathering (sulphate and/or sulphide minerals) than by the loss of Cl−. The mineralization consists of sulphides, and disseminated pyrite has also been noted; these could be sources of dissolved SO42 −  through oxidation. It is not known how widespread secondary sulphate minerals are in the study areas, but given the climate, it is not unlikely that gypsum may be found in the regolith. In contrast, the Kayar groundwaters are scattered more equally on either side of the seawater dilution line, with a few samples showing a large SO42 −  deficit relative to Cl−. This can result from SO42 −  removal, such as via bacterial sulphate reduction (BSR; e.g. Krouse & Mayer 2000; Canfield 2001; Kirste et al. 2003), or an addition of Cl−, such as via dissolution of halite (NaCl). Unfortunately, we do not have S isotopic data for those few Kayar samples with low SO42 − /Cl− and therefore cannot argue further on the more likely of these two scenarios.

At Hinta, most samples immediately adjacent to, or down-flow from, mineralization have low SO42 − /Cl− (except one, which is above the 75th percentile) ( Fig. 7). The reasons for this are not clear at present. The lithological unit containing the Hinta mineralization, however, has several values above the 75th percentile further up and down strike from the mineralization; these could be areas of interest for future exploration. At Kayar, both the Kayar and Ghugra prospects show elevated SO42 − /Cl− values in their vicinity, but not the unnamed prospect. A few samples away from known mineralization also show elevated values.

Fig. 7
Fig. 7

Geochemical maps showing the distribution of 1000 SO42 − /Cl− (mass ratio) for Hinta (a) and Kayar (b) groundwaters. (See Fig. 1 for topographic, flow direction and geological information.) Basemap is geology polygons from Figure 2. Classes are based on the boxplot, and symbols are based on Exploratory Data Analysis principles (open circle, 0–25th percentile; dot, 25th–75th percentile; plus, 75th percentile–whisker; growing squares: whisker–Max.; see Tukey 1977; Velleman & Hoaglin 1981; Reimann et al. 2008).

Trace elements

Modelling of the oxidation of sulphide ore minerals, say ZnS, has shown that the concentrations of SO42 −  and Zn are expected to increase in the attending water (de Caritat & Kirste 2005; Brookfield et al. 2006). However, metals from the sulphide minerals (and other associated trace elements) tend to adsorb more or less readily onto surfaces of Fe-oxyhydroxides, for instance, such that less mobile elements (e.g. Pb) will have the potential to disperse much less than more mobile metals (e.g. Zn), oxyanions (AsO43 − ), or SO42 −  itself. Therefore, mineralization footprints of different sizes would be expected down-flow from a sulphide ore body for various elements or ratios of elements to Cl−.

In this paper, we consider trace cations Zn, Pb and Cu and oxyanion-forming Mo, As and Se, because these are sulphide ore metals, common pathfinders or trace elements (TEs) associated with stratiform sediment hosted Zn–Pb deposits (e.g. Large et al. 2000; Canet et al. 2004). Also, we are interested to see if different dispersion haloes result from the different transport characteristics of cations and oxyanions.

In considering these trace elements, we use their concentration ratios to Cl− to circumvent anomalous values that may be due solely to evaporative concentration or mixing with fresher water. Even in the narrow range of salinities encountered here, we find that any given TE concentration can correspond to a range of TE/Cl− spanning up to two orders of magnitude or more. At the lower end of the TE/Cl− range, the TE concentration may be high but so is the Cl− concentration (and other major ions or EC); at the higher end, the TE is genuinely elevated in the water up and above the expected value reflecting that water's salinity or conductivity.

Furthermore, by comparing these ratios with SO42 − /Cl−, any trend with a positive slope indicates coinciding addition of the metal or oxyanion and SO42 − , which may indicate that sulphide mineralization at, or below, the groundwater table is, or has been, undergoing oxidation with subsequent release of metals, oxyanions and SO42 − .

Many groundwater samples have elevated Zn/Cl− (which span over five orders of magnitude) and more than half of them also have high SO42 − /Cl− (compared with seawater for instance) ( Fig. 8a). There is a strong positive trend between the two ratios, particularly in the case of Hinta (r = 0.97 compared with r = 0.20 at Kayar). Because of the coincidence of Zn and SO42 −  addition (as opposed to simple increases in concentration), elevated Zn/Cl− in groundwater can indicate areas (immediately) down the hydraulic and/or chemical gradient from Zn-bearing sulphide minerals undergoing oxidation. Similar relationships are observed for Pb/Cl− v. SO42 − /Cl− (r = 0.66 at Hinta and r = 0.33 at Kayar) and for Cu/Cl− v. SO42 − /Cl− (r = 0.73 at Hinta and r = 0.32 at Kayar) (not shown). Together, these diagrams suggest that sulphide minerals are being oxidized, adding dissolved metals and SO42 −  to the groundwater.

Fig. 8
Fig. 8

Zn/Cl− v. SO42 − /Cl− (a) and Mo/Cl− v. SO42 − /Cl− (b) (molar ratios) scatter diagrams for Hinta and Kayar groundwaters. Smaller symbols are for samples with Zn or Mo concentrations below the detection limit (DL; see Table 1), which were assigned a value of ½ DL. SW, average seawater.

Elements such as Mo, As and Se can be present in aqueous solution as oxyanions, which, depending on the pH and redox conditions and the reactive sorbing surfaces of minerals present (e.g. Dold & Fontboté 2002), may allow them to be transported down-gradient further than cations. This may result in larger dispersion footprints under neutral to alkaline pH and oxidizing conditions (e.g. Gray 2001; Lawrance 2001) and hence more cost-effective hydrogeochemical exploration. The relationships between Mo/Cl− and SO42 − /Cl− in the present case studies show strong positive correlations (r = 0.96 at Hinta and r = 0.48 at Kayar) over more than five orders of magnitude in Mo/Cl− (Fig. 8b). This is interpreted to indicate a concomitant addition of Mo and SO42 − , which can be an indicator of the presence of mineralization, particularly if supported by data from cations (see above) and other oxyanions such as As (r = 0.57 at Hinta and r = 0.20 at Kayar) and Se (r = 0.93 at Hinta and r = 0.39 at Kayar) (not shown).

Figure 9 shows the geochemical map for As/Cl− at Hinta and Kayar. At Hinta, the mineralization and the unit hosting it generate several anomalies above the 75th percentile. The maximum As/Cl− value is located c. 2 km east (downstream along the inferred groundwater flow path; see Fig. 1) from the prospect, which may indicate the known mineralization. Another sample located between it and the Hinta mineralization, however, is low in As normalized to Cl−. Some samples collected down-gradient from the Kayar, Ghugra and unnamed prospects are anomalous in As/Cl− (>75th percentile), and several other (multi-point) anomalies are found; for example, in the northern part of the study area, in an east–west zone across the sampled area just south of the unnamed mineralization, and to the north and NW of a lake near Kayar.

Fig. 9
Fig. 9

Geochemical maps showing the distribution of 1000 As/Cl− (mass ratio) for Hinta (a) and Kayar (b) groundwaters. (See Fig. 1 for topographic and flow direction information.) Basemap is geology polygons from Figure 2. Classes are based on the boxplot, and symbols and sources are as in Figure 7.

Together with the evidence provided by the metal cations above, this supports the hypothesis of polymetallic sulphide minerals being oxidized, and thereby releasing ore metals, indicator trace elements and SO42 −  to the groundwater. These increases in trace element concentrations, even when normalized to Cl− to remove evaporation and dilution effects, amount to several orders of magnitude difference between the lowest and highest values. These gradients can thus potentially be used as sensitive hydrogeochemical exploration tools.

Isotopes of S and Sr

Important sources of S in the study areas and their typical S isotopic compositions (e.g. see Krouse & Mayer 2000) are likely to be: (1) natural atmospheric S of marine origin (δ34S values generally ranging from +15‰ to +21‰ V-CDT); (2) soil S species (expected to have similar isotopic composition to atmospheric deposition); (3) fertilizers (+10‰ to +15‰); (4) reduced S minerals, such as pyrite, from the metasedimentary rock units (−30‰ to +5‰); (5) S from sulphide mineralization (generally from −10‰ to +7‰; in the Hinta study area from 3.6 to 6.9‰, Anglo American plc, unpublished data; no data available from Kayar). Sources (1), (2) and (3) are essentially indistinguishable (δ34S > +10‰) and dominant here ( Fig. 10). Source (4) does not appear to be overwhelming here. Thus, oxidation of sulphide mineralization appears to be the most important source of 34S-depleted sulphate in the groundwaters.

Fig. 10
Fig. 10

δ34S v. SO42 − /Cl− (molar ratio) scatter diagrams for Hinta and Kayar groundwaters: (a) all data; (b) detail. Three samples from Hinta (903, 913 and 930) are identified by labels (see Fig. 11). The range of δ34S values for Zn sulphides from Hinta (3.6–6.9‰ V-CDT, Anglo American plc, unpublished data) is shown by shaded field.

Fig. 11
Fig. 11

Geochemical maps showing the distribution of δ34S for Hinta (a) and Kayar (b) groundwaters. Three samples from Hinta (903, 913 and 930) are identified by labels (see Fig. 10). (See Fig. 1 for topographic and flow direction information.) Basemap is geology polygons from Figure 2. Classes are based on the boxplot, and symbols and sources are as in Figure 7.

Many samples (particularly from Kayar) have low δ34S values (<10‰ V-CDT) and low SO42 − /Cl− (Fig. 10). It is uncertain how these samples evolved to this composition, but it is possible that they were in contact with sulphide mineralization then underwent BSR. A few samples, however, have similarly low δ34S values coinciding with elevated SO42 − /Cl−. Such a trend has been identified elsewhere as potentially indicative of the addition of 34S-depleted S from the oxidation of sulphide minerals by groundwater (de Caritat et al. 2005). Three of the Hinta samples (903, 913 and 930), in particular, form a trend with a negative slope in Figure 10b. These same three samples are also identified on the δ34S map (Fig. 11), where they describe a down-gradient trend pointing to the unit hosting the Hinta mineralization as a source of low δ34S SO42 − . At Kayar, a few areas also are characterized by low δ34S values; the prospects of Kayar and Ghugra are among those, and there are a few more areas of potential interest (samples from the unnamed prospect area were not analysed for δ34S).

Strontium is potentially a good tracer of the source rocks of chemical constituents in water (McNutt 2000). Usually, groundwater reacting with carbonate rocks will be rich in Sr but have a low 87Sr/86Sr signature, although some carbonates with radiogenic Sr isotopic signatures have been observed (e.g. Jacobson et al. 2002). Conversely, groundwater that has interacted with silicate rocks containing Rb-bearing minerals such as biotite and K-feldspar will contain little Sr of more radiogenic composition. Thus, lithological fingerprinting of aquifers can be attempted in some cases using groundwater Sr concentration and isotopic composition (e.g. de Caritat et al. 2005). Strontium isotopes have been used to help elucidate water–rock interaction processes around mineralization (e.g. de Caritat et al. 2005; Leybourne & Cameron 2006).

Strontium isotopes were available only from the Kayar study area (n = 58; Fig. 12), where they span a wide range (0.0256; Table 1). Here, 87Sr/86Sr varies inversely with EC (r = −0.264; significant at p > 0.95) and pH (r = −0.433) (not shown). The inverse correlation with pH reflects a greater contribution of dissolved weathering products from carbonates (higher pH), which we surmise have low 87Sr/86Sr here, than from metapelites (lower pH) in the area, which probably have more radiogenic Sr isotopic ratios. The groundwater 87Sr/86Sr values correlate with the distribution of lithologies at Kayar in that carbonates, with presumably low 87Sr/86Sr, crop out in the NE, whereas metapelites and granites crop out in the SW and central parts of the area, where the highest 87Sr/86Sr are recorded in the groundwaters (Fig. 12).

Fig. 12
Fig. 12

Geochemical maps showing the distribution of 87Sr/86Sr for Kayar groundwaters. (See Fig. 1 for topographic and flow direction information.) Basemap is geology polygons from Figure 2. Classes are based on the boxplot, and symbols and sources are as in Figure 7.

Saturation indices

Saturation index (SI) values, described as: SI=log⁡IAPKsp (1) where IAP is the ion activity product and Ksp is the solubility product of the mineral, give an indication of how undersaturated (SI ≪ 0), saturated (SI c. 0, as IAP approaches Ksp) or oversaturated (SI ≫ 0) a given solution is with respect to a mineral phase and have been used previously in ore-related research (Welch & Lico 1998; Pirlo & Giblin 2004; Leybourne & Cameron 2006). Here, SI values were calculated using PHREEQC (Parkhurst & Appelo 1999) for several typical ore, alteration and weathering minerals (galena, cerussite, alunite, jarosite, etc.), which can be reasonably assumed to be present in the systems being investigated. The lack of measured redox and, at Kayar, alkalinity precludes drawing conclusions from the SI values obtained for sulphide and carbonate minerals; however, calculated SI values for some non-carbonate secondary minerals yield potentially useful patterns.

The advantage of using SI values in hydrogeochemical exploration is that they incorporate variables such as pH, redox, ligand concentrations and temperature, all of which can affect mineral solubility and element transport, rather than just the raw metal concentrations and/or element combinations and ratios. It is difficult to assess the accuracy of SI values because of availability of thermodynamic properties for relevant minerals and aqueous species, and uncertainty in those properties and in estimates of activity coefficients, especially in high ionic strength groundwater such as found in many semi-arid or arid environments and/or highly weathered landscapes (e.g. Pirlo & Giblin 2004). Despite those current limitations, relative (rather than absolute) changes in SI values are likely to be useful, especially when plotted on maps to show spatial distributions. As an example, we found that SIjarosite might be a useful indicator. The solubility of jarosite can be described as: KFe3(SO4)2(OH)6(s)+3H+=K++2Fe3++2SO42−+4.5H2O(l) (2) giving the ion activity product (assuming aH2O(l) = ajarosite = 1): IAP=aK+aFe3+2aSO42−2aH+3 (3) where aX is the activity of species X. This expression, and consequently the SI, incorporates the measured concentrations and estimated activity coefficients of K+, Fe3+ and SO42 −  as well as the pH of the groundwaters (i.e. it is a multi-parameter indicator). Figure 13 shows the spatial distribution of SIjarosite, which clearly shows the dispersion pattern trending east from the Hinta mineralization along our inferred groundwater flow paths. The Kayar region map shows some elevated values down the inferred groundwater flow path from the Ghugra and unnamed prospects. In contrast, there are low values for the groundwaters near the Kayar prospect, and the reasons for this are unclear.

Fig. 13
Fig. 13

Geochemical maps showing the distribution of the saturation index (SI) values for jarosite for Hinta (a) and Kayar (b) groundwaters. (See Fig. 1 for topographic and flow direction information.) Basemap is geology polygons from Figure 2. Classes are based on the boxplot, and symbols and sources are as in Figure 7.

Activity–activity diagrams

Displaying hydrogeochemical data on activity–activity diagrams is useful in identifying potential indicator minerals for mineralization and/or lithology (primary, secondary and alteration), and the likely transporting aqueous species of elements. This approach has been applied only in a small number of earlier studies (e.g. Cameron & Leybourne 2005). Figure 14 shows that smithsonite is a likely indicator mineral of Zn mineralization at both Hinta (saturated) and Kayar (oversaturated), presumably as an alteration product of primary Zn sulphide minerals. The diagrams are drawn for maximum concentrations of Zn detected in the Hinta and Kayar groundwater datasets to highlight the stability of smithsonite. The stability field shrinks with decreasing Zn concentration. The calculated fugacity of CO2(g) is uncertain because alkalinity was not measured in the field (Hinta) or at all (Kayar), but it should be noted that the steepness of the solubility boundaries of smithsonite means that even an order of magnitude change in fCO2(g) would not change the implication that smithsonite is a likely indicator mineral. The most likely species of Zn in solution, and thus important in its transport, is Zn2+, although other aqueous complexes may be important and cannot be determined (e.g. organic complexes, because there is no information on dissolved organic compounds).

Fig. 14
Fig. 14

Log fCO2(g) v. pH diagrams for the Zn–C–O–H chemical system overlain with Hinta (a) and Kayar (b) groundwater data. The diagrams were calculated at 25 °C and 1 bar using the Geochemist's Workbench software (GWB; Bethke 2006) and the Minteq.dat thermodynamic database distributed with GWB. For Hinta (a), log a(Zn2+) = −5.5 (maximum value for the Hinta dataset); for Kayar (b), log a(Zn2+) = −4.8 (maximum value for the Kayar dataset). The data points were calculated using measured field pH and log fCO2(g) calculated using PHREEQC (Parkhurst & Appelo 1999).

CONCLUSIONS

Groundwaters were collected from >200 wells around the Hinta and Kayar SEDEX base metal prospects in Rajasthan, India, with the aim of determining whether hydrogeochemistry could be a useful tool in mineral exploration. This study assesses the chemical and isotopic data in terms of processes affecting the composition of groundwater, and seeks to identify useful chemical, isotopic and modelling approaches to recognizing groundwater–mineralization interaction.

The hydrogeochemical study of groundwaters at the Hinta and Kayar prospects helps identify processes that have taken place between water and minerals, which ultimately can inform on how groundwater can be used, here and elsewhere, as a useful sampling medium in mineral exploration projects. Water composition at both sites reflects the dominant bedrock types but the groundwaters at Kayar are more conductive, and have a higher pH and a lower slope in δD v. δ18O space, compared with those from Hinta, which is interpreted to indicate that they have undergone more water–mineral interaction and more evaporation. They also intersect the local meteoric water line much lower than the Hinta waters, suggesting recharge under different palaeo-recharge conditions (climate, elevation, latitude). Thus, the Kayar groundwaters are likely to be older than those from Hinta.

The groundwaters have experienced interaction with Na-minerals (e.g. Na-plagioclase dissolution) early in their evolution, followed by cation exchange, evaporation, evapotranspiration and mixing. A few samples from Kayar have low SO42 − /Cl− that could be caused by bacterial sulphate reduction, or an addition of Cl− (e.g. via dissolution of rare (unreported) evaporitic minerals). Interaction of groundwater with mineralization (sulphide oxidation) is recognized by elevated SO42 −  concentrations, lower δ34S isotopes reflecting sulphide mineralization, and elevated concentrations of cations and oxyanions associated with mineralization (e.g. Pb, Zn, Mo). We recommend the use of ratios of elements of interest (metals, oxyanions) to a conservative tracer, such as Cl−, in applications of hydrogeochemistry to mineral exploration. This is because this allows identification of element additions resulting from chemical processes, as distinct from simple concentration increases caused solely by evaporation, for which the ratios stay constant at least up to a point.

Spatial coincidence was noted at Hinta and Kayar between known areas of mineralization, or their host lithological units, and the distributions of Cl−-normalized anions (e.g. SO42 − /Cl−), cations (e.g. Zn/Cl−) and oxyanions (e.g. As/Cl−), as well as the distributions of isotopes (e.g. δ34S) and saturation indices (e.g. SI jarosite). These should be further investigated and modelled before they can be fully developed into mineralization vectors, but the empirical results presented here are encouraging. Activity–activity diagrams may be useful tools in interpreting hydrogeochemical data; for example, log fCO2(g) v. pH diagrams show that smithsonite could be a useful indicator mineral for Zn mineralization. Such information can be taken back to the field to help recognize areas of alteration or weathering at or near the surface that could be the focus of targeted exploration activity.

Acknowledgments

Fieldwork was carried out by Anglo American plc and sample analysis was performed in external laboratories for Anglo American plc. P. de C. and D.C.McP. completed evaluations of the Hinta and Kayar groundwater chemistry as part of an industry collaboration project under the Cooperative Research Centre for Landscape Environments and Mineral Exploration (CRC LEME), which is partly funded by the Australian Government. The authors are indebted to K. P. Tan and M. Lenahan of CRC LEME, who provided internal reviews of the original draft, and to M. Leybourne and an anonymous reviewer, who peer-reviewed the submitted manuscript for GEEA with utmost attention and objectivity. Their constructive criticisms, as well as G. Hall's supportive comments, have contributed to great improvements in the final paper. This paper is published with the approval of the CEO of CRC LEME and of the CEO of Geoscience Australia.

REFERENCES

  1. ↵
    1. Appelo C.A.J.,
    2. Postma D.
    2005. Geochemistry, Groundwater and Pollution, 2nd edn. Balkema, Rotterdam.
  2. ↵
    1. Bethke C.M.
    2006. The Geochemist's Workbench, Release 6.0 Reference Manual. University of Illinois, Urbana.
  3. ↵
    1. Bhattacharya S.K.,
    2. Gupta S.K.,
    3. Krishnamurthy R.V.
    1985. Oxygen and hydrogen isotope ratios in groundwaters and rivers from India. Proceedings of the Indian Academy of Sciences (Earth and Planetary Sciences), 94, 283–295.
    OpenUrlWeb of Science
  4. ↵
    1. Brookfield A.E.,
    2. Blowes D.W.,
    3. Mayer K.U.
    2006. Integration of field measurements and reactive transport modelling to evaluate contaminant transport at a sulfide mine tailings impoundment. Journal of Contaminant Hydrology, 88, 1–22.
    OpenUrlCrossRefPubMedWeb of Science
  5. ↵
    1. Cameron E.M.
    1978. Hydrogeochemical methods for base metal exploration in the northern Canadian Shield. Journal of Geochemical Exploration, 10, 219–243.
    OpenUrlCrossRefWeb of Science
  6. ↵
    1. Cameron E.M.,
    2. Leybourne M.I.
    2005. Relationship between groundwater chemistry and soil geochemical anomalies at the Spence copper porphyry deposit, Chile. Geochemistry: Exploration, Environment, Analysis, 5, 135–145.
    OpenUrlAbstract/FREE Full Text
  7. ↵
    1. Cameron E.M.,
    2. Leybourne M.I.,
    3. Kelley D.L.
    2002. Exploring for deeply covered mineral deposits: Formation of geochemical anomalies in northern Chile by earthquake-induced surface flooding of mineralized groundwaters. Geology, 30, 1007–1010.
    OpenUrlAbstract/FREE Full Text
  8. ↵
    1. Canet C.,
    2. Alfonso P.,
    3. Melgarejo J.C.,
    4. Belyatsky B.V.
    2004. Geochemical evidences of sedimentary–exhalative origin of the shale-hosted PGE–Ag–Au–Zn–Cu occurrences of the Prades Mountains (Catalonia, Spain): trace-element abundances and Sm–Nd isotopes. Journal of Geochemical Exploration, 82, 17–33.
    OpenUrlCrossRefWeb of Science
  9. ↵
    1. Canfield D.E.
    2001. Isotope fractionation by natural populations of sulfate-reducing bacteria. Geochimica et Cosmochimica Acta, 65, 1117–1124.
    OpenUrlCrossRefWeb of Science
  10. ↵
    1. Carey M.L.,
    2. McPhail D.C.,
    3. Taufen P.M.
    2003. Groundwater flow in playa lake environments: impacts on gold and pathfinder element distributions in groundwaters surrounding mesothermal gold deposits, St. Ives area, Eastern Goldfields, Western Australia. Geochemistry: Exploration, Environment, Analysis, 3, 57–71.
    OpenUrlAbstract/FREE Full Text
  11. ↵
    1. Chakrabarti C.,
    2. Pyne T.K.,
    3. Gupta P.,
    4. Basu Mallick S.,
    5. Guha D.
    (compilers) 2004. A Manual of the Geology of India, Vol. I Precambrian, Part IV Northern and Northwestern Part of the Peninsula. Geological Survey of India Special Publication, 77.
  12. ↵
    1. Closs L.G.
    1997. Exploration geochemistry: Expanding contributions to mineral resource development. In: Gubins A.G. (ed.) Proceedings of Exploration 97: Fourth Decennial International Conference on Mineral Exploration. Prospectors and Developers Association of Canada (PDAC), Toronto, 3–8.
  13. ↵
    1. de Caritat P.,
    2. Kirste D.
    2005. Hydrogeochemistry applied to mineral exploration under cover in the Curnamona Province. MESA Journal (Quarterly Earth Resources Journal of Primary Industries and Resources South Australia), 37, 13–17.
    OpenUrl
  14. ↵
    1. de Caritat P.,
    2. Kirste D.,
    3. Carr G.,
    4. McCulloch M.
    2005. Groundwater in the Broken Hill region, Australia: recognising interaction with bedrock and mineralisation using S, Sr and Pb isotopes. Applied Geochemistry, 20, 767–787.
    OpenUrlCrossRefWeb of Science
  15. ↵
    1. Dold B.,
    2. Fontboté L.
    2002. A mineralogical and geochemical study of element mobility in sulfide mine tailings of Fe oxide Cu–Au deposits from the Punta del Cobre belt, northern Chile. Chemical Geology, 189, 135–163.
    OpenUrlCrossRefWeb of Science
  16. ↵
    1. Domenico P.A.,
    2. Schwartz F.W.
    1997. Physical and Chemical Hydrogeology, 2nd edn. Wiley, New York.
  17. ↵
    1. Drever J.I.
    1997. The Geochemistry of Natural Waters: Surface and Groundwater Environments, 3rd edn. Prentice–Hall, Englewood Cliffs, NJ.
  18. ↵
    1. Gat J.R.
    1996. Oxygen and hydrogen isotopes in the hydrologic cycle. Annual Review of Earth and Planetary Sciences, 24, 225–262.
    OpenUrlCrossRefWeb of Science
  19. ↵
    Government of India 2008. National Portal of India. World Wide Web Address: http://india.gov.in/
  20. ↵
    Government of India Planning Commission 2007. Report of the Working Group on Mineral Exploration and Development (Other than Coal and Lignite) for the Eleventh Five Year Plan. Government of India, New Delhi.
  21. ↵
    1. Gray D.J.
    2001. Hydrogeochemistry in the Yilgarn Craton. Geochemistry: Exploration, Environment, Analysis, 1, 253–264.
    OpenUrlAbstract/FREE Full Text
  22. ↵
    1. Gupta P.
    2004. Ancient orogens of Aravalli region. Geological Survey of India Special Publication, 84, 151–205.
    OpenUrl
  23. ↵
    1. Höller W.,
    2. Gandhi S.M.
    1995. Silver-bearing sulphosalts from the metamorphosed Rampura, Agucha Zn–Pb–(Ag) deposit, Rajasthan, India. Canadian Mineralogist, 33, 1047–1057.
    OpenUrlWeb of Science
  24. ↵
    1. Höller W.,
    2. Touret J.L.R.,
    3. Stumpfl E.F.
    1996. Retrograde fluid evolution at the Rampura Agucha Pb–Zn–(Ag) deposit, Rajasthan, India. Mineralium Deposita, 31, 163–171.
    OpenUrlCrossRefWeb of Science
  25. ↵
    1. Hronsky J.M.A.,
    2. Groves D.I.
    2008. Science of targeting: definition, strategies, targeting and performance measurement. Australian Journal of Earth Sciences, 55, 3–12.
    OpenUrlCrossRefWeb of Science
  26. ↵
    1. Jacobson A.D.,
    2. Blum J.D.,
    3. Walter L.M.
    2002. Reconciling the elemental and Sr isotope composition of Himalayan weathering fluxes: insights from the carbonate geochemistry of stream waters. Geochimica et Cosmochimica Acta, 66, 3417–3429.
    OpenUrlCrossRefWeb of Science
  27. ↵
    1. Jiang R.,
    2. Ren T.,
    3. Zhang H.,
    4. Ma S.,
    5. Kong M.
    1994. Orientation hydrogeochemical survey of the Liudaogou Cu–Mo mineralized zone in a basalt-covered area, northeastern China. Journal of Geochemical Exploration, 51, 79–91.
    OpenUrlCrossRefWeb of Science
  28. ↵
    1. Kelley D.L.,
    2. Hall G.E.M.,
    3. Closs L.G.,
    4. Hamilton I.C.,
    5. McEwen R.M.
    2003. The use of partial extraction geochemistry for copper exploration in northern Chile. Geochemistry: Exploration, Environment, Analysis, 3, 85–104.
    OpenUrlAbstract/FREE Full Text
  29. ↵
    1. Kelley D.L.,
    2. Kelley K.D.,
    3. Coker W.B.,
    4. Caughlin B.,
    5. Doherty M.E.
    2006. Beyond the obvious limits of ore deposits: the use of mineralogical, geochemical, and biological features for the remote detection of mineralization. Economic Geology, 101, 729–752.
    OpenUrlAbstract/FREE Full Text
  30. ↵
    1. Kirste D.,
    2. de Caritat P.,
    3. Dann R.
    2003. The application of the stable isotopes of sulfur and oxygen in groundwater sulfate to mineral exploration in the Broken Hill region of Australia. Journal of Geochemical Exploration, 78-79, 81–84.
    OpenUrl
  31. ↵
    1. Krishnamurthy R.V.,
    2. Bhattacharya S.K.
    1991. Stable oxygen and hydrogen isotope ratios in shallow ground waters from India and a study of the role of evapotranspiration in the Indian monsoon. In: Taylor H.P. Jr., O'Neil J.R., Kaplan I. (eds) Stable Isotope Geochemistry: A Tribute to Samuel Epstein. Geochemical Society Special Publication, 3, 187–193.
    OpenUrl
  32. ↵
    1. Krouse H.R.,
    2. Mayer B.
    2000. Sulphur and oxygen isotopes in sulphate. In: Cook P.G., Herczeg A.L. (eds) Environmental Tracers in Subsurface Hydrology. Kluwer, Boston, MA, 195–231.
  33. ↵
    1. Large R.R.,
    2. Bull S.W.,
    3. McGoldrick P.J.
    2000. Lithogeochemical halos and geochemical vectors to stratiform sediment hosted Zn–Pb–Ag deposits: Part 2. HYC deposit, McArthur River, Northern Territory. Journal of Geochemical Exploration, 68, 105–126.
    OpenUrlCrossRefWeb of Science
  34. ↵
    1. Lawrance L.M.
    2001. Multi-element dispersion within salt-lake environments: case study of the buried Hannan South gold deposit, Western Australia. Geochemistry: Exploration, Environment, Analysis, 1, 323–339.
    OpenUrlAbstract/FREE Full Text
  35. ↵
    1. Leybourne M.I.,
    2. Cameron E.M.
    2006. Composition of groundwaters associated with porphyry-Cu deposits, Atacama Desert, Chile: Elemental and isotopic constraints on water sources and water–rock reactions. Geochimica et Cosmochimica Acta, 70, 1616–1635.
    OpenUrlCrossRefWeb of Science
  36. ↵
    1. Leybourne M.I.,
    2. Cameron E.M.
    2007. Groundwaters in geochemical exploration: methods, applications, and future directions. In: Milkereit B. (ed.) Proceedings of Exploration 07: Fifth Decennial International Conference on Mineral Exploration. Prospectors and Developers Association of Canada (PDAC), Toronto, 201–221.
  37. ↵
    1. Leybourne M.I.,
    2. Goodfellow W.D.,
    3. Boyle D.R.
    1998. Hydrogeochemical, isotopic, and rare earth element evidence for contrasting water–rock interactions at two undisturbed Zn–Pb massive sulphide deposits, Bathurst Mining Camp, N.B., Canada. Journal of Geochemical Exploration, 64, 237–261.
    OpenUrlCrossRefWeb of Science
  38. ↵
    1. McNutt R.H.
    2000. Strontium isotopes. In: Cook P.G., Herczeg A.L. (eds) Environmental Tracers in Subsurface Hydrology. Kluwer, Boston, MA, 233–260.
  39. ↵
    1. Parkhurst D.L.,
    2. Appelo C.A.J.
    1999. User's guide to PHREEQC (version 2) – A computer program for speciation, batch-reaction, one-dimensional transport, and inverse geochemical calculations. US Geological Survey Water-Resources Investigations Report, 99-4259.
  40. ↵
    1. Pauwels H.,
    2. Tercier-Waeber M.-L.,
    3. Arenas M.,
    4. et al.
    2002. Chemical characteristics of groundwater around two massive sulphide deposits in an area of previous mining contamination, Iberian Pyrite Belt, Spain. Journal of Geochemical Exploration, 75, 17–41.
    OpenUrlCrossRefWeb of Science
  41. ↵
    1. Phipps G.C.,
    2. Boyle D.R.,
    3. Clark I.D.
    2004. Groundwater geochemistry and exploration methods: Myra Falls volcanogenic massive-sulphide deposits, Vancouver Island, British Columbia, Canada. Geochemistry: Exploration, Environment, Analysis, 4, 329–340.
    OpenUrlAbstract/FREE Full Text
  42. ↵
    1. Pirlo M.C.,
    2. Giblin A.M.
    2004. Application of groundwater–mineral equilibrium calculations to geochemical exploration for sediment-hosted uranium: observations from the Frome Embayment, South Australia. Geochemistry: Exploration, Environment, Analysis, 4, 113–127.
    OpenUrlAbstract/FREE Full Text
  43. ↵
    1. Porwal A.,
    2. Carranza E.J.M.,
    3. Hale M.
    2006. Tectonostratigraphy and base-metal mineralization controls, Aravalli province (western India): New interpretations from geophysical data analysis. Ore Geology Reviews, 29, 287–306.
    OpenUrlCrossRefWeb of Science
  44. ↵
    Raj Darpan 2008. Official Portal of the Government of Rajasthan. World Wide Web Address: http://www.rajasthan.gov.in/rajgovt/Districtprofile/udaipur.html/.
  45. ↵
    1. Ray S.,
    2. Rao R.S.
    2004. Geology, metallogeny of Panchmata–Bhinder Belt and its comparative study with neighbouring Proterozoic cover belts, southeastern Rajasthan. Geological Survey of India Special Publication, 72, 101–112.
    OpenUrl
  46. ↵
    1. Reimann C.,
    2. Filzmoser P.,
    3. Garrett R.,
    4. Dutter R.
    2008. Statistical Data Analysis Explained – Applied Environmental Statistics with R. Wiley, New York.
  47. ↵
    1. Roy A.B.,
    2. Jakhar S.R.
    (eds) 2002. Geology of Rajasthan (Northwest India) Precambrian to Recent. Scientific Publishers (India), Jodhpur.
  48. ↵
    1. Saini P.,
    2. Singh S.,
    3. Pandit M.K.
    2006. Angular relationship between rocks of the Aravalli and Delhi Supergroups in southeastern Rajasthan – a possible unconformity. Current Science, 91, 432–434.
    OpenUrlWeb of Science
  49. ↵
    1. Sinha-Roy S.
    2004. Intersecting Proterozoic transpressional orogens, major crustal and suspect terranes in Rajasthan Craton: A plate tectonic perspective. Geological Survey of India Special Publication, 84, 207–226.
    OpenUrl
  50. ↵
    1. Smith R.E.
    1996. Regolith research in support of mineral exploration in Australia. Journal of Geochemical Exploration, 57, 159–173.
    OpenUrlCrossRefWeb of Science
  51. ↵
    1. Srivastava I.C.,
    2. Sharma B.,
    3. Kulshristha S.K.
    2005. Sector Policy for Rural Drinking Water and Sanitation (Draft). UNICEF Report, Government of Rajasthan. World Wide Web Address: http://rajwater.gov.in/sprdws.pdf.
  52. ↵
    1. Stumm W.,
    2. Morgan J.J.
    1996. Aquatic Chemistry, 3rd edn. Wiley, New York.
  53. ↵
    1. Taufen P.M.
    1997. Ground waters and surface waters in exploration geochemical surveys. In: Gubins A.G. (ed.) Proceedings of Exploration 97: Fourth Decennial International Conference on Mineral Exploration. Prospectors and Developers Association of Canada (PDAC), Toronto, 271–284.
  54. ↵
    1. Tukey J.W.
    1977. Exploratory Data Analysis. Addison Wesley, Reading, MA.
  55. ↵
    1. Velleman P.F.,
    2. Hoaglin D.C.
    1981. Applications, Basics and Computing of Exploratory Data Analysis. Duxbury, Boston, MA.
  56. ↵
    1. Welch A.H.,
    2. Lico M.S.
    1998. Factors controlling As and U in shallow ground water, southern Carson Desert, Nevada. Applied Geochemistry, 13, 521–539.
    OpenUrlCrossRefWeb of Science
Back to top
Alerts
Citation tools
Permissions
View PDF
Email to
Print
Download PPT
Bookmark this article