Ti-rich dual spherules recovered from Segment S2 near the axial ridge (69.865 degrees E, 24.819 degrees S), of the southern Central Indian Ridge (CIR), Indian Ocean, were examined to understand their petrogenesis and hydrothermal-magmatic significance. Three Ti-rich dual spherules were identified within an 85 g sediment sample. Two of these comprise cryptocrystalline spherules containing w & uuml;stite and titanite-ilmenite-shcherbakovite (tn-il-shc) assemblages, whereas the third consists of a Ti-rich magnetite-w & uuml;stite spherule attached to an ellipsoidal Fe-Ti-rich cryptocrystalline clast hosting cuboidal to rhombohedral rutile crystals within silica-rich glassy mesostasis. The high abundance of the spherules and absence of Ni enrichment argue against an extraterrestrial origin. Textural relationships, including shared interfaces between adjacent droplets, reaction rims, dendritic crystallites and localized fine-grained zones near the attachment sites, indicate that the dual spherules formed via collision and interaction of molten Fe-Ti-rich droplets prior to quenching. Followed by nucleation at the liquid-liquid interface and growth within a thermal gradient. In one dual-spherule, the molten droplet seems to have collided with a pre-existing solid rutile-bearing clast, suggesting entrainment of altered fragments during eruptive activity. In contrast, the mineral chemistry of Ti-rich magnetite/wustite, rutile-bearing clast and the presence of Fe-rich vein indicate modification via hydrothermal processes post-formation of the dual-spherule. However, the studied spherules likely formed during ridge-axis hydrothermal-magmatic activity, where Fe-Ti-rich molten droplets were generated during late-stage magmatic differentiation, dispersed into the water column and rapidly quenched to produce the observed dual-spherules.

Hydrothermal exploration has traditionally focused on ridge-axis systems, yet emerging studies increasingly highlight the prevalence of off-axis hydrothermal activity. Despite the Indian Ocean ridge system comprising nearly 28% of the global mid-ocean ridge network, it remains one of the least studied. This study investigates the geochemical and mineral magnetic characteristics of surface sediments along segment 4 of the Central Indian Ridge (CIR) from the Rodriguez Triple Junction to assess hydrothermal contributions, particularly from off-axis sources. Geochemical and magnetic analyses reveal a carbonate-dominated sediment composition with clear hydrothermal signatures. Major and trace element concentrations, thermomagnetic behaviour, and magnetic grain size distributions collectively indicate a significant input of hydrothermally altered material, especially in off-axis sediments. These off-axis samples exhibit lower magnetic susceptibility and finer magnetic grain size in contrast to the higher susceptibility and coarser grains observed in near-axis sediments. Elemental patterns show stronger hydrothermal enrichment in off-axis locations, despite their greater distance from known active vent fields, suggesting input from previously undocumented hydrothermal sources. While precise localization of these sources requires further investigation, the findings provide crucial preliminary information and highlight the importance of off-axis hydrothermal systems. This study contributes to a broader understanding of hydrothermal processes in slow-spreading ridge environments and underscores the need for expanded exploration in this underexplored region.

The seawater precipitation, hydrothermal input (plume-derived or weathered sulfide), and weathering of nearby rock outcrops constrain the dominant end-member components in the mid-ocean ridge (MOR) sediments. We have conducted mineralogical, geochemical, and statistical studies of surface sediments from the eastern part of the ultra-slow spreading Southwest Indian Ridge (SWIR) 63 degrees E-69 degrees E. Further, we combined factor analysis and linear regression to demonstrate how relative enrichment/depletion of certain elements compared to the general regional sediment composition can constrain the local seafloor processes. Mineralogy and factor analysis of the carbonate-free geochemical data reveal that the sediments consist of three main end-members with respect to Al, Ti, Mg, Fe, Mn, K, Rb, Cu, Zn, V, Cr, Ni, and As; the end-members are mixed in different proportions in the sediments. The three endmember components, authigenic hydrothermal minerals-Fe-Mn-(oxyhydr)oxides, bernessite, and hematite; basaltic detritus-Labradorite and alteration products (montmorillonite, vermiculite, and illite); and ultramafic detritus-antigorite, account for 62.3 %, 21.8 %, and 10.2 % of the elemental variance, respectively. We also used Ti/Al vs Cr/Al and Ni/Al proxies to show that some samples consist of ultramafic and serpentinized detritus. The sediment sample C-GC-16(0-1 cm) at 67.260 degrees E, 26.574 degrees S, consists of relatively high conservative and redox-sensitive elements (U, Mo, V, As), alkali metals (K, Rb, Cs), and Cu, reflecting the presence of a hydrothermal source in the near vicinity. Moreover, linear relations reveal the relative scavenging of REEs from the seawater by Fe-Mn-(oxyhydr)oxides, which are recorded by Ce anomaly and REE fractionation values relative to Fe and Mn content.

Tianzuo hydrothermal field (THF) in the eastern Southwest Indian Ridge (SWIR) is reported as an inactive ultramafic-hosted system and fragments of massive and altered sulphides were recovered from the hydrothermal field at (27 degrees 57 ' S, 63 degrees 32 ' E). The sulphide formation happened in the THF in two phases, at both high-temperature and low to medium temperature environment. The mineral assemblages in massive sulphides suggest the contribution of high-temperature hydrothermal fluid in the ore formation process. The presence of covellite and Fe-oxy-hydroxides in the altered sulphides indicates a low to medium-temperature environment and subseafloor alteration of fluid by seawater mixing. Elevated TREE contents with no significant Eu anomaly in both massive and altered sulphides further supports the subseafloor hydrothermal fluid mixed with seawater. Elevated Pd and Rh concentrations, along with their positive correlation with Cu, suggest Pd and Rh fractionation during the seawater-hydrothermal fluid mixing. 230Th/U dating results of massive hydrothermal sulphide samples give the age of 24 kyr (+2.4) and 15.6 kyr (+0.8), and an incomplete sampling demonstrates a possible minimum age of the vent field.

The interest in deep-sea mineral resources has surged recently, driven by the increasing need for metals and the global push for sustainable, low-carbon energy sources under the 'blue economy' framework. The deepsea minerals include polymetallic nodules, cobalt-rich Fe-Mn crusts, and polymetallic sulphides, which contain high amounts of copper, nickel, cobalt and other valuable metals. These mineral deposits are often associated with unique and fragile ecosystems, which necessitates the development of mining technologies with minimal environmental impact. Here, we review the key deep-sea minerals, their resource potential, exploration aspects and the need for sustainable extraction, with a particular focus on India's exploration activities.

Iron is a limiting nutrient in the marine biogeochemical cycle, and hydrothermal processes at mid-ocean ridges are well-known as one of its sources to the water column. However, a major portion of the hydrothermal iron is precipitated near the source and plays an essential role in oceanic elemental cycling. Here, we carried out a detailed study on the geochemical characteristics of Fe, using a sequential chemical extraction protocol, in a short sediment core collected from the eastern Southwest Indian Ridge (SWIR) to understand the iron association in individual mineral phases. Major and trace and rare-earth element concentrations, positive europium anomaly, and rare-earth fractionation show that the source components in the sediment core are composed of biogenic, local mafic, ultramafic, and hydrothermal origin. Solid-phase Fe speciation results indicate that >60% of Fe is associated with the Fe-oxides phase and indicate the hydrothermal plume particulates settled from the water column. A relatively low concentration of Fe associated with the pyrite and silicate (FeRes) phase suggests an erosion of sulphide and silicate minerals from the nearby vent field. The down-core variation reflects the transformation of primary ferrihydrite to more stable oxide mineral goethite/hematite and, to some extent, the formation of silicate minerals.

Mineral magnetic and geochemical investigations were carried out on a short sediment core collected from the eastern Southwest Indian Ridge (ESWIR) to study the variations in the source components. The magnetic concentration parameter chi arm (representing the concentration of stable single domain (SSD) sized grains), magnetic grain size ratios chi arm/chi lf, chi arm/SIRM, geochemical ratios Fe/Ti, Co/Zn, and Zn/Fe and Ba content serve as hydrothermal indicators, all of which show a distinct top - bottom variability. The magnetomineralogical parameters S-ratio and coercivity (Hc) also follow these variations, suggesting an increased contribution of hydrothermal components in the top 15 cm of the core. Significant enrichments of Fe, Mn, and Mg in the samples, along with depletions of detrital elements Al, Si, Rb, Zr, Hf, and Nb in the element/Upper Continental Crust (UCC) values, show that the majority of the detrital component is locally sourced. Thermomagnetic measurements of samples indicate that the major remanence carrier is magnetite in the core, along with minor contributions from titanomagnetite, hematite, and iron sulfides.

Mid-oceanic ridge basalts (MORB) offer the best access to the earth's interior in understanding the mantle evolution with time and represent the most dynamic and youngest geological features on the earth's surface. The eastern Southwest Indian Ridge (SWIR) extending from the Melville fracture zone (MFZ; 28°S, 60°E) to the Rodrigues Triple Junction (RTJ; 25°30' S, 70°E) displays unique major and trace element compositions when compared to the global MORB systematics. This study presents new petrological, geochemical, and Sr-Nd isotope data of the collected on-axis and off-axis basalts from the eastern part of the SWIR (63–69°E). In the Ce/Pb vs. Ce and Nb/U vs. Nb plots, the analyzed samples exhibit modifications associated with subduction zones. They follow a trajectory from the lower continental crust towards the fresh MORB. Similarly, in the Nb/Yb vs. Th/Yb plot, the samples deviate from the MORB and OIB mantle array, revealing a pronounced enrichment linked to subduction-related processes. Further, in the Rb/Nb vs. Ba/Nb, as well as in the 87Sr/86Sr vs. 143Nd/144Nd plots, the studied samples cluster within the Backarc basin basalt (BABB) field and distinctly separate them from the Indian MORB basalt. The ratios [K2O/TiO2=0.08-0.21, (La/Sm)N=0.82-1.1, Th/Nb=0.08-0.22, and Nb/La=0.35-0.72] are quite variable and enriched in these basalts compared to N-MORB and suggests that the mantle source is reasonably heterogeneous beneath this section of SWIR and the extent of mantle melting is not the primary controlling process responsible for the genesis of the variable chemical compositions. The present study on the basalts from eastern SWIR unveils a distinct Back arc setting, indicating modifications in the mantle source associated with subduction-related hydrated processes. Notably, this study provides the first evidence from the eastern segment of the SWIR, supporting the notion of Pacific mantle outflow influencing and modifying the Indian Ocean mantle around 200 million years ago. Further, this study proposes a flat slab subduction mechanism akin to the model presented by Navarrete et al. (2019) as a plausible mechanism for this enrichment process.

Abstract Water column physico‐chemical studies were conducted over the southern Central Indian Ridge between 24°44’S and 25°52’S to identify and chemically characterize seafloor hydrothermal activity. High turbidity values were observed between 2300 and 2700 m with two distinct layers, between water depths of 2320–2500 m and 2510–2650 m, at two closely spaced CTD stations at 24°48.62’S (CTD‐17‐P5) and 24°48.68’S (CTD‐17‐P8). Elevated concentrations of dissolved Mn (DMn: 19–112 nM), dissolved Fe (DFe: 33–88 nM), methane (CH4: 32–246 nM), elevated δ3He values (28%–88%), and stable carbon isotope ratios of CH4 confirm the hydrothermal origin. In plume layer‐1, the maximum concentrations were observed at 2375m at P8 and in plume layer‐2, the maximum concentrations were observed at 2570 m at P5. The stable isotope ratios of methane (δ13C‐CH4) show that heavier isotopes are enriched (−13.2‰ to −14.7‰) in the plume waters and are similar to vent fluids on the global mid‐oceanic ridges. Further, morphological and mineralogical studies of plume particles, collected from the plume layer‐2 maxima, clearly show the presence of barite, pyrite, chalcopyrite, and indicate possible venting of high‐temperature fluids in the vicinity of P5. Enrichment in methane relative to the other tracers and the general geochemical characteristics of these two plume layers, CH4/Mn (1.8–2.2); CH4/Δ3He (85–97 × 106), Mn/Δ3He (44–46 × 106), Fe/Δ3He (52–54 × 106), indicate that these plumes are formed from fluids released at the seafloor that circulated through ultramafic/gabbroic rocks. The high concentrations of dissolved gases and metals combined with the presence of sulfide particles in the water column provide evidence for a new ultramafic/gabbroic‐hosted hydrothermal vent field, at 24°49’S on the southern Central Indian Ridge.

The development of multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS) in 1992 opened up new opportunities for geochemical, mineral exploration, and environmental studies. Recent developments in MC-ICP-MS and its hyphenation to techniques such as laser ablation including femtosecond laser sampling, advances in detection system and several other developments made MC-ICP-MS, one of the most versatile analytical techniques for the determination of isotopic compositions in several types of earth and environmental materials. Different studies in recent times indicated that MC-ICP-MS can routinely produce isotopic data that is similar in precision to those obtainable by secondary ion mass spectrometry (SIMS), sensitive high resolution ion microprobe (SHRIMP), and thermal ionization mass spectrometry (TIMS), with striking advantages such as relatively higher throughputs, ease of analysis as the source operates at atmospheric pressure, and possibility of sample introduction by other means such as laser ablation and chromatographic techniques. Recent studies demonstrate the decisive benefits of MC-ICP-MS analysis (both solution and laser ablation modes) not only isotopic ratio determinations, but also absolute element concentration determinations of several elements in the periodic table in different types of geological and environmental materials in terms of versatility, accuracy, precision and for improved spatial resolution. Laser ablation split stream (LASS) technique with ability to do dating, and capability to obtain isotopic and elemental information simultaneously in rocks and minerals on a single sampling event, when coupled to a second ICP-MS system (typically a quadrupole ICP-MS or a high resolution-ICP-MS) demonstrated its potential to become an important analytical tool in solving important problems, especially in geochemistry. The performance characteristics of MC-ICP-MS are compared with those of other similar analytical techniques such as TIMS, SHRIMP, and SIMS with recent examples. This review contains detailed descriptions of the development of MC-ICP-MS instrumentation, analytical procedures, reference materials, and focused applications in the area of geochemistry, mineral exploration, and environmental areas.

The marine carbonate sediment samples are subsampled and collected from various cores spanning from top depths 11.67 m (core depth below sea floor; CSF) and 11.45 m (CSF) up to the depth of 168.57 m (CSF) respectively of U1394 A and B holes drilled to south east of Montserrat Volcanic Island during IODP Expedition 340. These thin horizons are characterised for major, minor, trace, rare earth elements and total carbon to decipher their mode of origin, provenance and implications on paleo-environment. The carbonate sediments show variation in major oxide contents in SiO2 (11.4–35.5 wt%), CaO (22.4–44.7 wt%), CaCO3 (3.6–76.6 wt%), Fe2O3T (1.1–6.0 wt%), MgO (2.9–4.0 wt%) with very low K2O, TiO2 and P2O5 contents. Their Mg/Ca, reciprocals (Ca/Mg) and Sr/Ca ratios classify these sediments as dolomitic limestones. These sediments depict very low total organic carbon (TOC) contents compared to total inorganic carbon (Tic) indicating their lithogenic origin. The PAAS normalised rare earth element and yttrium (REY) distribution patterns show slightly depleted LREE abundances relative to HREE with (La/Yb)SN range between 0.3 and 0.7 indicating low degree of fractionation with varying ∑REE contents (35–105 ppm). Subchrondritic to superchondritic Y/Ho (25.7–31.6), Ce/Ce* (0.2–0.5) and Pr/Pr* (1.0–1.3) indicate low magnitude negative anomalies, slight negative to positive anomalies of Eu (Eu/Eu*; 0.9–1.6) point towards minimal terrigenous input, varied nature of sediments and plagioclase addition. The studied sediments mimic the seawater REY distribution patterns indicating REY are sourced from the seawater. The major, minor, immobile element ratios and redox sensitive element proxies indicate that the studied carbonate sediments are derived from an intermediate to felsic source. These sediments deposited in a low saline, oxygen rich open ocean shallow water environment akin to an active continent margin affinity. It can also be stated that later to their dissolution in extinct arc zones (between the old and young arc) led to the re-deposition in favourable sites in the marine sediment column during middle Miocene period or later due to the submarine slope failures and debris avalanches.

Hydrothermal vent incidence is proportional to the spreading rate of the mid-oceanic ridges (MORs) (Baker et al., 1996). However, the ultra-slow spreading Southwest Indian Ridge (SWIR) is unique and has a relatively higher incidence of hydrothermal vent fields compared with other ultra-slow spreading ridges (German et al., 1998; Baker and German, 2004). In the present study, sediment samples from the less studied easternmost section of the ultra-slow spreading SWIR are investigated to decipher the signatures of hydrothermal activity. The sediments are mainly composed of calcium carbonate (55-85%), Fe-Mn-(oxyhydr)oxide (13-27%), and residual aluminosilicate phases (2-17%). The metalliferous nature, low Mn concentration (393-1772 ppm), negative Ce, and positive Y anomalies in the shale-normalized rare earth element (REE) pattern of the bulk sediments provide evidence for the presence of hydrothermal inputs in most of the sediments. The fractionation among lighter REEs over heavier REEs in bulk sediments indicates the high-temperature hydrothermal plume fall-out to the sediments. The leached fraction also shows similar negative Ce and positive Y anomalies, and indicates that the Fe-Mn-(oxyhydr)oxide precipitates in these sediments may be dominantly of hydrothermal origin. In addition to hydrothermal Fe-Mn-(oxyhydr)oxide phases, the residual fraction of the sediments also consists of minor quantities of hydrothermally sourced sulfate phases. Otherwise, the residual fraction is significantly dominated by mid-oceanic ridge basalt (MORB) derived components in addition to serpentinized peridotite and terrigenous material. Among the studied sediments, sample E-3-16 from Fuji Dome (influenced by hydrothermal activity) has high zinc concentrations, which indicates the possibility of a new vent field in the vicinity. The present study also introduces a new geochemical tool (Zn/Fe vs Co/Zn proxy) for assessing the contribution of hydrothermal components in the sediments. The Zn/Fe vs Co/Zn proxy will be more useful in MOR settings hosting sulfides dominated by sphalerite. The influence of hydrothermal activity in most of the studied sediments from the eastern SWIR indicates that the ultra-slow spreading eastern SWIR has the potential to possess a larger number of hydrothermal vent fields.

Prakasam Igneous Province (PIP) is an important geological domain in the Eastern Dharwar Craton (EDC), found in the junction zone between the EDC and Eastern Ghat Mobile Belt (EGMB). The Pedda Cherlo Palle (PCP) gabbros are massive, leucocratic-mesocractic, and show cumulus textures with minerals plagioclase, cpx, and amphiboles. Compositionally, plagioclase is a labradorite-bytownite, cpx is diopside to augite, olivines are hyalosiderites and amphiboles are magnesiohornblendes. PCP gabbros have normal SiO2, high Al2O3, moderate to high TiO2, Na2O and medium Fe2O3, so, classified as subalkaline tholeiitic gabbros. Fractionated rare earth element (REE) patterns, high abundance of large ion lithofile elements (LILE) and transitional metals coupled with light REE (LREE) relative enrichment over heavy REE (HREE) and Nb are characteristics of partial melting of depleted mantle and melts that have undergone fractional crystalisation. These partial melts are enriched in LREE and LILE, due to the addition of slab derived sediment and fluids. PCP gabbros contain low abundance (5.1 to 24.6 ng/g) of platinum group elements (PGE), and show an increase in the order Ir>Os>Pt>Ru»Pd>Rh. We propose that the subduction related intraoceanic island arc might have accreted to the southeastern margin of India to the east of Cuddapah basin in a collisional regime that took place during Ur to Rodinia amalgamations.

REE (Rare Earth Elements) and yttrium in sea water samples, from the Afanasy-Nikitin Seamount (ANS) located around 3 South latitude and 83 East longitude in the north central Indian Ocean were precisely determined by high resolution inductively coupled plasma mass spectrometry (HR-ICP-MS) method. A modified procedure has been designed for determination of REE and yttrium wherein the water samples were subjected to a pre-concentration step using bis-2-ethylhexyl phosphoric acid (HDEHP) complexing agent. Sea water reference materials such as NASS-5 and SLEW-3 were used for calibration as well as to check the accuracy of the procedure adopted. Samples were analyzed for REE and yttrium by HR-ICP-MS. Precisions achieved for various rare earths and yttrium is better than 8% RSD with comparable accuracies. Limit of detection (3σ) were generally in the range of 0.02-1.2 pg/ml range for all these elements. This method facilitates rapid and interference-free determination of REE and yttrium from relatively small volume of sea water (10 ml). Recoveries for different REE and Y were better than 5%, and accuracy and precision of the determinations are within 8% RSD. The Ce-negative anomalies with smooth normalized-REE patterns obtained for both certified reference materials and samples further substantiate that the procedure adopted and the data generated are extremely accurate. A slight enrichment of heavy REE were observed in the central Indian Ocean waters which might be attributed to the river flows containing more dissolved trace elements including REE. A sharp negative Ce-anomaly in the normalized REE distribution patterns indicates that the source of REE in particular Ce in marine sediments is seawater. Results of the variation in REE concentrations with depth indicated that the physico-chemical conditions of bottom ocean water follow a very complex mechanism.

Boggulakonda gabbroic complex (BKGC) (E 80°00'30", N 15°44'04") in the Prakasam Igneous Province (PIP) (southern India) is studied in detail using major, trace, REE and PGE geochemistry to understand its geochemical evolution. It shows sharp contact relationships with the Precambrian quartzofeldspathic mica schist and granite gneisses. It is one among the several gabbroic complexes, occurring to the east of Cuddapah basin, along the eastern margin of Nellore schist belt. It is predominantly composed of gabbro and gabbronorite with melanocratic to leucocratic variations. Petrographic studies show cumulus, poikilitic and porphyritic textures, micro-deformation features and symplectites/replacement textures. Magnetite and ilmenites are dominant opaques with subordinate pyrite and chalcopyrite. Cumulus phases of plagioclase, Cpx, are essential minerals whereas olivine, opx, amphibole and opaques appear as intercumulus phases. These rocks are classified as sub-alkaline, low Ti-tholeiitic gabbros. The normative compositions indicate that these rocks are quartz, plagioclase and pyroxene normative. The differentiation index (D.I.) determined from the norm compositions are in the range of 11.4 to 20.9 indicating that they are early-middle stage basaltic differentiates. These studies also indicate fractional crystalization was a dominant process of their genesis. The major, incompatible trace and REE geochemistry of BKGC rocks show LILE-LREE enrichment and HREE-HFSE depletion, pronounced Eu-positive anomalies, negative Nb anomalies relative to Th and low Ti/V ratios. Based on the above and other binary plots, it can be inferred that the BKG rocks are the products of ∼5-15% partial melting of depleted mantle source strongly modified by the melt enrichment and addition of slab derived fluids in a subduction zone environment and emplaced as tholeiitic island arc magmas. BK gabbroic rocks indicate low abundances of PGE. PPGE's are greater than IPGE; Pd/Ir and Pd/Pt ratios are greater than primitive mantle and chondrites. PGE geochemistry correlate well with the petrogenesis and tectonic discrimination studies made by using major, trace and REE geochemistry.

Accurate and reliable analytical techniques and methodologies possessing high sensitivity and selectivity, coupled with convenience and economy and applicable to real-world situations, are required for geochemical studies. Quantitative analysis of major, minor, and some trace elements were performed in several geochemical reference samples using a new microwave plasma-atomic emission spectrometry (MP-AES) technique. A range of rock, soil, sediment, and water reference materials were chosen to evaluate the performance of this technique. A set of sample decomposition/digestion methods, which included a closed digestion technique utilizing a multi-acid mixture in a closed vessel and a fusion digestion technique utilizing lithium meta-borate in a glassy carbon crucible, were used for the determination of all major and minor elements in addition to Si, and more than 15 trace elements in sample solutions at the ng/g and sub-ng/g levels. Matrix interference effects encountered from concomitant elements, acid type and concentration, calibration strategies adopted, detection limits, accuracy and precision obtained were discussed. The analytical wavelengths selected were based on sensitivity and interference effects from other concomitant elements present in different sample solutions.The detection limits for several elements were found to be in the 0.05 to 5 ng/g range, which approached those of an ICP-AES technique but were much superior to flame AAS. Precisions of <= 3% RSD were obtained for major and minor elements and <= 6% RSD for trace elements with comparable accuracies for most determinations. The results obtained in this study clearly indicate that MP-AES is a suitable atomic emission spectrometry technique for the accurate determination of major, minor, and selected trace elements required in geochemical studies.

Methods were designed and developed for the quantitative determination of Au, Ag, Pt and Pd in several rock and ore reference samples by a new analytical technique, microwave plasma-atomic emission spectrometry (MP-AES). Two-gram samples dissolved in 100 ml using aqua regia digestion was directly. used without any separation or a pre-concentration step for the determination of Au and Ag. On the other hand, NiS fire-assay technique followed by tellurium co-precipitation separation and pre-concentration step was adopted on 5 g samples to separate Pt and Pd from rock matrix for the determination of these two elements. Detection limits obtained are in the 0.5-5 ng/ml range for all these metals. MP-AES detection limits were compared with those of other well-established techniques, such as F-AAS, GF-AAS, INAA, ICP-AES and ICP-MS. The results obtained for Au, Ag, Pt and Pd were compared with those obtained by well-established analytical techniques such as F-AAS and ICP-MS. Precision and accuracy of the methods were demonstrated using replicate analyses of some international precious metal ore reference materials. Precisions of <5% RSD at practically 10-200 ng/ml levels of these elements in solution with comparable levels of accuracies were obtained which show good agreement with certified data. As there is limited literature on the application of MP-AES in geochemical and mineral exploration areas, this study forms one of the first application studies in these areas.

The performance and response of two commonly used certified reference materials (CRMs) for mafic rocks MRG-1 (CANMET, Canada) and JGb-1 (Geological Survey of Japan), both gabbroic in composition, are evaluated for a set of mafic plutonic rocks (gabbros) from Boggulakonda (BK) occurring to the east of Proterozoic Cuddapah Basin, South India. In this study, quadrupole-inductively coupled plasma mass spectrometry was used to generate trace and rare earth element (REE) data using MRG-1 and JGb-1 as calibration standards separately for a comparative study. It is found that the two CRMs show highly variable major, minor and trace element compositions except ΣREE. When used for BK gabbros, JGb-1 has yielded better results than MRG-1 with respect to trace elements (HFS elements Nb and Ta in specific), whereas a good agreement was observed between both CRMs for REE concentrations when compared with certified data. The Nb–Ta element distribution patterns for BK gabbros in the spidergrams plotted using JGb-1 as CRM show relatively prominent and pronounced negatively spiking anomalies with reference to Th, whereas using MRG-1 as calibration CRM yielded unresolved and unclear Nb–Ta anomalies in the present study. The geochemistry (major, minor and trace) of MRG-1 is different when compared to that of JGb-1. Probably this is reason for the disparity in the results obtained by inductively coupled plasma mass spectrometry on mafic plutonic rocks. The study conducted on the BK gabbros, reveals better and reliable results using JGb-1 as CRM. This study also reveals the importance of using proper CRM for calibration having closely matching trace and REE concentrations in addition to major and minor elements, for obtaining reliable data in geological samples.

Application of xenon (Xe-129) as an internal standard for the precise and accurate determination of several trace elements in different kinds of water samples by inductively coupled plasma mass spectrometry (ICP-MS) is described. The novelty of this approach is that no external addition of any reagent is involved since xenon is present as an impurity in the plasma gas itself. As a result, the possibility of introducing any type of elemental impurities through the addition of an internal standard will be completely avoided. Therefore, this feature will be of great value when determinations are carried out for elements present at ng/mL and sub-ng/mL levels.The utility of Xe-129 as an internal standard has been validated using standard reference materials NIST 1640d, NIST 1643e, and NIST 1640a. The accuracies and precisions achieved were markedly better when internal standardization was applied. In general, trace element data in a variety of water samples were obtained with < 5% RSD with comparable accuracy in each case, suggesting that this method can be applied routinely for the determination of trace elements in water.