Determination Of Isotopes Research Articles

Utilizing isotopic and elemental markers to enhance the authenticity of potatoes

AbstractGiven the economic importance of potato production, establishing the origin of unknown commercial samples declared as local, is particularly important for both producers and competent authorities. In the study presented here, stable isotopic ratios of deuterium, oxygen, carbon and nitrogen, were determined in order to develop a potato provenance methodology. Isotopic determinations were conducted in an alcohol, preceded by the enzymatic degradation of potato starch using α-amylase to yield soluble dextrins and oligosaccharides. Subsequently, the hydrolyzed potato starch underwent fermentation to produce ethanol, which was then obtained through distillation under controlled conditions. The integration of data obtained from analyzing the D/H isotopic ratios using SNIF-NMR spectroscopy in potato samples for the first time, in conjunction with measurements of the 13C/12C, 15N/14N, and 18O/16O ratios via IRMS, yielded a unique isotopic fingerprint for the potato samples under examination. Elemental analysis by ICP-OES also added important information in the dataset. The chemometric analysis by applying OPLS-DA technique, highlighted the parameters of (D/H)II, δ18O, R and Cu as the best discriminator markers. The proposed model gave 94.07% correct classification of the samples, regarding their geographical origin. It is believed that the differentiation of local potatoes is related to the unique geological and climatic conditions existing in the island. All the above-mentioned conclusions are very promising, for the protection of local potato production.

Disequilibrium in natural decay series in samples from Czech water treatment plants: Uranium, radium and thorium isotopes determination

In the Czech Republic, underground or mixed source water treatment plants are classified as the workplaces with possible increased exposure from a natural source of radiation. When releasing waste materials or residues from these NORM workplaces into the environment, the content of natural radionuclides is measured and compared with the clearance levels established by Czech legislation. The content of natural radionuclides in solid samples is determined primarily by high-resolution gamma-ray spectrometry. Six radionuclides, 238U, 228Th, 226Ra, 228Ra, 210Pb, 40K, are measured directly or by their measurable decay products (assuming equilibrium), the activity concentration of the other four radionuclides, 234U, 230Th, 210Po, 232Th is conservatively estimated. The study is focused on mapping the properties of NORM arising from the treatment of groundwater and, based on the real samples measurement, verification of new proposed assessment approach. It was tested whether the knowledge of the content of natural radionuclides in water can be practically used to estimate the content in NORM. Samples of water, filter material or sludge were taken from 16 different water treatment plants. Combination of gamma-ray spectrometry and radiochemical methods were applied to determine the content of radionuclides 234U, 238U, 226Ra, 228Ra, 228Th, 230Th and 232Th in solid NORM, and radionuclides 234U, 238U, 226Ra, 228Ra in water. Based on the results the proposed modification of the assessment was verified.

Evaluation of a Novel Femtosecond Laser Ablation System for In Situ Analysis Based on Two-Dimensional Galvanometer Scanners.

Uneven energy distribution of femtosecond lasers presents a significant challenge for single-spot analysis, which often leads to concave ablation craters. This study assesses the performance of a femtosecond laser ablation system for in situ analysis using novel galvanometer scanners. A galvanometer rapidly moved the laser beam focus to create craters with a small beam spot. We first examined the inductively coupled plasma mass spectrometry (ICP-MS) signal sensitivity to laser parameters, establishing a strong linear correlation with the laser energy, repetition rate, scanning ablation area, and galvanometer scanning frequency. Elemental fractionation analysis of NIST SRM 610 suggests minimal bias, with fractionation indices of different elements approaching unity. Subsequently, the elemental concentration of six reference material glasses was measured by fsLA-ICP-MS to evaluate the elemental quantification capabilities of the Galvo-femtosecond laser (Galvo-fsLA). The laser's capability for in situ U-Pb dating was demonstrated by concordant U-Pb ages of five zircon reference materials that are highly consistent with the ID-TIMS ages reported previously. Finally, the reliability of the new Galvo-fsLA for isotope analysis was verified by the accurate determination of radiogenic Hf, Pb isotopes, and stable Cu isotopes, all agreeing well with their reference values within uncertainties. These assessments underscore the significant potential of Galvo-fsLA for enhanced accuracy and precision of single-spot in situ analysis.

A Catalyst Tube-Equipped Dual-Stage Tube Furnace System for Accurate Hg Isotopic Determination of Ore Samples Using Neptune Plus Multicollector Inductively Coupled Plasma Mass Spectrometry.

Mercury (Hg) isotopes, which display mass-dependent fractionation and mass-independent fractionation, provide a multidimensional tracer to decipher the source of metals in mineral deposits. However, mineral ore samples usually contain abundant interfering elements (e.g., Te) that can cause inaccurate Hg isotopic analysis. Available acid digestion and combustion methods failed to remove these interfering elements, hindering the application of Hg isotopes for metallogenetic tracing. Here, we developed a new dual-stage tube furnace system employing a Mn-containing catalyst tube to pretreat mineral ore samples. This method yielded good Hg recoveries (100.5 ± 3.8%, 1SD, n = 15) and low levels of interfering elements in sample solutions, allowing for accurate analysis of a series of ore standard reference materials (GBW-11108v: coal; GSO-3: Cu-Ag sulfide ore; GBW 07859: Au-Te sulfide ore). The new method was also successfully applied to measure the Hg isotopic composition of magmatic and hydrothermal ore deposits, which yielded a large range in Δ199Hg value (-0.19 to 0.22‰) for ore deposits formed in different geological settings, highlighting the future applications of this method for metallogenic tracing, especially tracing the source of metals in mineral ore deposits.

RELATION BETWEEN δ13С, δ18О AND REE CONTENT IN CARBONATITES OF THE TOMTOR COMPLEX, SAKHA REPUBLIC (YAKUTIA)

The paper reports the comprehensive study of phosphorus-rare metal (polymineral) carbonatites (I) and rare metal (ankerite) carbonatites (II) of the Tomtor massif based on ICP-MS, XRF, XRF-SI, SEM methods and isotope determination of C, O and 86Sr/87Sr. With a similar mineral composition, the REE+Y content in carbonatites (I) averages 0.38 wt. %, and in carbonatites (II) it is 1.3 wt. %. The δ18О-δ13С diagram provides the C and O isotopic compositions of carbonatites (I) and (II) as two intersecting trends: (I) carbonates from wells 4041, 6151, 115-117 represent the secondary generation of carbonates derived with the deuterium fluid involved; (II) depicts transformation of carbonate by low-T fluid, with fluid/rock ratio = 5. The study identified an increase in the REE and δ18O contents in carbonatites as the temperature of their formation decreases and enrichment of rocks with REE minerals, associated with REE mobility reduction in the fluid while the temperature is decreasing.

Determination of Calcium Isotopes Using Inductive Coupled Plasma-Tandem Mass Spectrometry with Ozone-Induced Oxidation.

In this study, we propose a new method for determination of calcium (Ca) isotopes using inductive coupled plasma-tandem mass spectrometry (ICP-MS/MS). The most abundant isotope of Ca, 40Ca, has a spectrum identical with that of argon (Ar), which is often used as the carrier gas in ICP-MS analysis. The detection capability for 40Ca is thus significantly reduced in the presence of 40Ar. To avoid interference from 40Ar during the 40Ca measurements, ozone (O3) was used as the reaction gas in the ICP-MS/MS analysis. The reaction of Ca+ with O3 in the collision cell preferentially produced CaO3+. In contrast, the reaction between Ar+ and O3 produced ArO+, which further reacted with the oxidized O3 to produce Ar+. Because Ar+ does not produced ArO3+ as the main product of the reaction with O3, the measurement of Ca+ as CaO3 via O3-induced oxidation resulted in considerably less interference from Ar+. The detailed mechanism of CaO3+ formation was investigated via quantum chemistry calculations by using density functional theory. The interaction between Ca+ and O3 yielded CaO3+, which immediately dissociated into either Ca+ and O3 or CaO+ and O2 because the pressure in the collision cell was approximately 1 Pa in the MS/MS experiments. Consequently, CaO3+ was formed by the consecutive reaction of Ca+ with O3, with CaO+ and CaO2+ as intermediates. The present method achieved the detection of less abundant Ca isotopes in certified reference materials such as 43Ca, 44Ca, 46Ca, and 48Ca, thereby allowing the determination of Ca isotopes with high sensitivity.

High–precision determination of carbon stable isotope in silicate glasses by secondary ion mass spectrometry: Evaluation of international reference materials

Secondary ion mass spectrometry (SIMS) has been used for isotope analysis of volatile components dissolved in silicate melts for decades. However, carbon in situ stable isotope analysis in natural silicate glasses has remained particularly challenging, with the few published attempts yielding high uncertainties. In this context, we characterized 31 reference silicate glasses of basaltic and basanitic compositions, which we then used as reference materials to calibrate δ13C − value analyses in silicate glasses by SIMS. This set of reference materials covers a wide range of CO2 concentrations (380 ppm – 12,000 ppm) and δ13C values (−28.1 ± 0.2 to −1.1 ± 0.2 ‰, ±1σ). The sets of reference materials were analyzed using large−geometry SIMS at two ion microprobe facilities to test reproducibility across different instrumental setups. The instrumental mass fractionation (IMF) varied widely with two different large−geometry SIMS instruments as well as with different analytical parameters such as field aperture size and primary beam intensity. We found that a precision better than ±1.1 ‰ (both average internal and external precision, ±1σ) for CO2 content higher than 1800 ppm could be achieved using a primary beam intensity of less than 5 nA, resulting in a final spot size of 10–20 μm, allowing precise analysis of δ13C in mineral−hosted melt inclusions. This level of precision was achieved at CO2 concentrations as low as 1800 ppm. This advance opens a wide range of new possibilities for the study of δ13C − value in mafic melts and their mantle sources. The reference materials are now available at the CNRS–CRPG ion microprobe facility in Nancy, France and will be deposited at the Smithsonian National Museum of Natural History, Washington, USA where they will be freely available on loan to any researcher.

World-class amethyst-agate geodes from Los Catalanes, Northern Uruguay: genetic implications from fluid inclusions and stable isotopes

AbstractThe amethyst and agate geodes from the Los Catalanes Gemmological District in Uruguay represent one of the main deposits of its kind worldwide. The geometry of the deposit is horizontal, with an irregular distribution of amethyst geodes within the upper level of the basalt lava flows and shows strong variations in their abundance, as well as quality, geometry, and shape. Reliable exploration guides are scarce, and the limited knowledge of the geological parameters controlling its occurrence makes exploration unpredictable, leading to inaccurate reserve estimation. Based on cutting-edge methods including nucleation-assisted microthermometry of one-phase fluid inclusions and determination of triple oxygen isotope in silicates and carbonates, as well as analysis of geode-hosted water and groundwater, we estimate the crystallisation temperatures in the range between 15 and 60 °C. These low temperatures point to amethyst crystallisation after the emplacement of the complete basalt pile. The mineralising fluid shows isotopic signatures consistent with meteoric water and very low salinities from pure water up to rarely over 3 wt% NaCl-eq., likely sourced from the groundwater hosted in the aquifers in the basaltic sequence and underlying units. Based on the insights provided by the new data, we propose the combination of open- and closed-system crystallisation inside pre-existing cavities due to the episodic infiltration of meteoric water in a rather stable geological context.

Determination of uranium and thorium isotopes in NORM materials in the ceramic industry by using alpha-particle spectrometry

Determination of uranium and thorium isotopes in NORM materials in the ceramic industry by using alpha-particle spectrometry

Mines to moana: Hydrochemical legacies in a historically mined watershed

This study investigates contemporary freshwater contamination originating from old mine workings in the Thames-Coromandel region of Te Ika-a-Māui (North Island), Aotearoa New Zealand. We employed a multi-method approach, including stable H and O isotope determinations of surface water, geochemical modelling, and diffusive gradients in thin films (DGT) deployments. Atypically, spring-summer (Sept–Nov) surface water stable oxygen isotope ratios (δ18O) were negatively displaced from meteoric values (ca. −0.28 ± 0.13 ‰), indicating a remarkable degree of low-temperature water-rock interaction, likely enhanced by dry antecedent conditions. Isotope ratios in tributaries showed less alteration than the main stem, suggesting greater meteoric inputs and shorter residence times in areas of high topographic relief. Conversely, in the main stem, isotope ratios revealed higher mineral weathering, accompanied by elevated dissolved metal concentrations, consistent with dominant inputs from shallow groundwater. Weathering of primary sulfides contributed pronounced acidity in one tributary (pH ca. 3.8), but overall, carbonate buffering ameliorated acid mine drainage across the catchment (pH ca. 7–8). Nevertheless, our results confirm exceedances of ecological guideline values (>80% protection threshold) for several toxic metals including Al, Zn, Cd and Pb; with implications for fresh and coastal water quality in Tikapa Moana-o-Hauraki, the Firth of Thames.

Determination of uranium isotopes in ground water by alpha spectrometry and associated age-dependent ingestion dose.

Determination of uranium isotopes in ground water plays a key role in assessment of geochemical condition of ground water and for estimating ingestion dose received by the general public because of uranium intake through drinking water. An attempt has been made in the present study to estimate isotopic composition and activity ratios (AR) of uranium isotopes by analysing the ground water samples using alpha spectrometry. Associated age-dependent ingestion dose was also calculated for the public of different age groups. 238U, 235U and 234U activity concentration was found to vary in the ranges of 5.85±1.19 to 76.67±4.16, < 0.90 to 3.15±0.84 and 6.52±1.25 to 107.02±4.92 mBq/L, respectively. 235U/238U AR varies from 0.038 to 0.068 with an average of 0.047 which is close to 0.046 implies that uranium in the ground water is from natural origin. Uranium concentration was found to vary in the range of 0.47±0.10μg/L to 6.20±0.34μg/L with a mean value of 3.01±0.23μg/L, which is much lower than national as well as international recommendation value. Annual ingestion dose to the public of all age groups for uranium intake through drinking water ranges from 0.60±0.11 to 19.50±1.03μSv/y.

Applications of zinc stable isotope analysis in environmental and biological systems: a review

Zinc (Zn) is an essential trace element that is involved in both biotic and abiotic processes in Earth's surface environments. Over the last 20 years, advances in mass spectrometry instrumentation have enabled unprecedented high-precision Zn isotope abundance ratio determinations in natural and anthropogenic samples. Supported by a solid theoretical background inherited from the traditional non-metal stable isotopes (C, N, H, O, S), the understanding of the controlling factors of Zn isotope fractionation has rapidly evolved. In this article, we review the main applications and findings of Zn isotopes in a variety of scientific domains, including metal contamination, magmatic differentiation, plant uptake, weathering, global climate change, dietary and trophic chains, and biomedicine. The analytical aspects of Zn isotope determination in solid and water samples and the principles and mechanisms of Zn isotope fractionation are also reviewed. This work aims to provide a general yet in-depth panorama of Zn isotope chemistry and to demonstrate the versatility and potential of this isotope system for studying the biological, geological and chemical cycling of Zn.

A fast method of liquid-liquid extraction for simultaneous 210Pb, 210Bi, 210Po isotopes determination in water samples

Currently, rapid, and efficient methods are pivotal in environmental monitoring within nuclear nations and in the effective management of radiation emergencies. For this reason, a comprehensive comparative analysis was conducted to select a sensitive, rapid, and robust method for determining the natural isotopes of 210Pb, 210Bi, and 210Po in water samples using a single analytical technique. The method is demonstrated using an ultra-low background liquid scintillation spectrometer Wallac 1220 Quantulus. In total, 9 laboratory procedures based on TOPO, TIOA, HDEHP, and scintillation cocktails were compared to determine the optimal method for mutual analysis of three isotopes within the same sequence action. The evaluation was carried out using samples spiked with a prepared SRM 4337 210Pb solution, and it included an assessment of several validation criteria. The recoveries (%) of 210Pb, 210Bi, and 210Po were 57.1%, 99.1% and 78.6% respectively, with the solvent extractor based on 0.20 M TIOA in toluene and using UG AB scintillation cocktail. The minimum detectable activities (MDA) of 210Pb, 210Bi, and 210Po were found to be 17.8, 6.80, and 0.90 [mBq/L] for the measurements using LSC, respectively. However, the least effective was the extraction with HDEHP in toluene/UG XR. The developed procedure is applicable in most laboratory conditions and could be applied to any aqueous samples. This approach gives a new opportunity with fast screening of environmental samples for a radiation risk assessment.

Elucidating the Genetic Mechanism and the Ore-Forming Materials of the Kaladawan Iron Deposit in the North Altyn Tagn, Western China

The Kaladawan iron deposit is located in the North Altyn Tagh and exhibits occurrences of iron ore bodies at the contact zone between Ordovician magmatic rocks (basalts, rhyolite, and granodiorite) and marble. However, controversy persists regarding the genetic classification and metallogenic mechanism of this deposit. Through a field investigation, single mineral in situ geochemical analysis, whole-rock geochemical analysis, and Fe isotope determination, the following conclusions are made: (1) Ti-(Ni/Cr) and (V/Ti)-Fe diagrams indicate that the magnetite from all studied rocks underwent hydrothermal metasomatism, while (Ni/(Cr + Mn))-(Ti + V) and (Ca + Al + Mn)-(Ti + V) diagrams suggest a skarn origin for these magnetites. Therefore, it can be inferred that the Kaladawan iron deposit is skarn-type. (2) The iron ore exhibits similar rare-earth-element characteristics to the altered basalt. Additionally, the altered basalts (δ56Fe = 0.024~0.100‰) are more enriched in light Fe isotopes than the unaltered basalts (δ56Fe = 0.129~0.197‰) at the same location, indicating that the ore-forming materials of the Kaladawan iron ore are mainly derived from basaltic rocks. (3) According to the law of mass conservation and the intermediate Fe isotopic composition of the iron ore between the granodiorite and basalt, the hydrothermal fluid for the formation of iron ores was inferred to be derived from the late intrusive granodiorite.

Optimizing distillation techniques for isotopic determinations in beverages

Optimizing distillation techniques for isotopic determinations in beverages

Improved determination of nitrate isotopes in irrigated agricultural areas and Bayesian mixing model quantification of nitrate sources and fate

Technological advancements in isotope techniques have been widely utilized in environmental pollution research, particularly for the monitoring of nitrate pollution in water. The utilization of pretreatment with an aqueous nitric acid solution offers numerous advantages in analyzing isotopic composition; however, there is still room for improvement regarding conversion efficiency, reduced reaction time, and cost control. In light of this, this study proposes an enhanced chemical conversion method that involves mitigating the interference caused by the nitrogen azide reaction during the pretreatment process, optimizing the purge gas to remove interfering factors, and improving the inlet device for measuring nitrous oxide. The improved method was applied to determine nitrate isotopes in the Ulansuhai Basin, Inner Mongolia and its reliability was verified through analytical results obtained from bacterial denitrification methods. The mean δ15N-NO3- and δ18O-NO3- values determined using the chemical transformation method were 4.85‰ and 23.44‰, respectively. Compared with the previous method, the improved method enhanced the maneuverability of precise control, the pretreatment time was reduced from 2 to 3 hours to 1.5 hours, and the experimental cost was scaled down to half of the original one. In addition, the contribution of each source was calculated by combining nitrate isotopes with a Bayesian stable isotope mixing model. It was found that manure sewage accounted for (50.1±22.6) % while soil nitrogen sources contributed (25.1±20.4) % to nitrate levels in Ulansuhai Lake's water. The chemical conversion methods successfully improved within this study can also be applied to other watersheds or regions. These research findings provide a valuable theoretical foundation for managing nitrogen sources within watersheds.

Uranium Single Particle Analysis for Simultaneous Fluorine and Uranium Isotopic Determinations via Laser-Induced Breakdown Spectroscopy/Laser Ablation-Multicollector-Inductively Coupled Plasma-Mass Spectrometry.

Uranyl fluoride (UO2F2) particles (<20 μm) were subjected to first-of-its-kind analysis via simultaneous laser-induced breakdown spectroscopy (LIBS) and laser ablation multi-collector inductively coupled plasma-mass spectrometry (LA-MC-ICP-MS). Briefly, a nanosecond pulsed high-energy laser was focused onto the sample (particle) surface. In a single laser pulse, the UO2F2 particle was excited/ionized within the microplasma volume, and the emission of light was collected via fiber optics such that emission spectroscopy could be employed for the detection of uranium (U) and fluorine (F). The ablated particle was simultaneously transported into the MC-ICP-MS for high precision isotopic (i.e., 234U, 235U, and 238U) analysis. This method, LIBS/LA-MC-ICP-MS was optimized and employed to rapidly measure 80+ UO2F2 particles, which were subjected to different calcination processes, which results in varying degrees of F loss from the individual particles. In measuring the particles, the average F/U ratios for the populations treated at 100 and 500 °C were 2.78 ± 1.28 and 1.01 ± 0.50, respectively, confirming loss of F through the calcination process. The average 235U/238U on the particle populations for the 100 and 500 °C were 0.007262 (22) and 0.007231 (23), which was determined to be <0.2% from the expected value. The 234U/238U ratios on the same particles were 0.000053 (11) and 0.000050 (10) for the 100 and 500 °C, respectively, <10% from the expected value. Notably, each population was analyzed in under 5 min, demonstrating the truly rapid analysis technique presented here.

Geological and isotopic reference points of the age of gold deposits of the Solovyovsky gold ore center in the Amur province

The data are presented on the geological and isotopic age of gold deposits of the Solovyovsky gold ore center in the Amur province, assigned to the gold-polymetallic, gold-sulfide-quartz, and goldquartz formation types. It is demonstrated that the geological and isotopic age of the most productive ore deposits of the gold-polymetallic (Berezitovoe) and gold-sulfide-quartz (Kirovskoe) types is Early Cretaceous according to geological data and Barremian (in the range of 131–125 million years) according to isotopic determinations. The geological age of poorly productive ore deposits of the gold-quartz type is difficult to determine due to the fact that the host rocks are most often represented by gneisses and crystal shales of Precambrian age. The isotopic age of formation of the Snezhninka and Zolotaya gora gold-quartz deposits is, respectively, Late Triassic (212 million years) and Late Jurassic (155 million years).

Surface and groundwater flow exchanges and lateral hydrological connectivity in environments of the Matusagaratí Wetland, Panama

The Matusagaratí wetland in the Panamanian Darien is one of the largest wetlands in Central America. These types of riverine wetlands, associated with large drainage basins, are complex hydrological environments where variations in water flows and exchanges condition the existence of different wetland habitats. The work aimed to establish the hydrological functioning of the Matusagaratí wetland in different sectors of the Balsas River, emphasizing the exchanges of surface and groundwater flows and the hydrological connectivity that exists between the different laterally linked wetland environments. For this purpose, a monitoring network for surface water and groundwater was established along transects intersecting various wetland environments in the middle and lower basin of the Balsas River. This network is complemented by measurement points for surface water located in streams and in the upper basin of the river. Data collected in sensors installed in boreholes were compared to river level and precipitation data. Continuous water level recording sensors were installed at the monitoring points, and samples were collected for the determination of major ions and stable isotopes. The results indicate that in the mangroves of the lower basin and in the cativo forests of the middle basin levee there is a strong exchange of water between the river and the shallow groundwater. This water exchange is strongly influenced by the tide which spreads from the estuary to the continent through the river. Meanwhile, in the middle basin, mixed forests and orey forests developed on the alluvial plain exhibit a hydrological functioning that depends primarily on precipitation inputs. This study provides data that could serve as a basis for the management of this large tropical wetland that, despite having protection initiatives, could be hydrologically impacted by unsustainable socio-economic practices.

U-Pb geochronology and Hf isotopes of the Grenvillian Río Hondo gneisses, Puebla: redefining the western edge of Oaxaquia

In situ Río Hondo (Puebla, southern Mexico) gneiss samples, as well as clastic samples recovered from the nearby-outcropping latest Paleozoic Matzitzi Formation, a fluvial unit mainly sourced by Grenvillian rocks, were historically interpreted as representative of the northernmost exposures of the Oaxacan Complex, the largest outcrop of ortho and metasedimentary units, made up of mostly 1.0–1.3 Ga protoliths, affected cfby local migmatization (ca. 1.1 Ga) and granulite facies metamorphism at ca. 0.98 Ga, constituting the most prominent outcrop of the Oaxaquia microcontinent.&#x0D; U-Pb geochronology and Lu-Hf isotopic determinations in zircon by LA-(MC)-ICP-MS were performed on both in situ and clast samples. In situ basement samples record a ca. 1.2 crystallization event, together with a younger one at ca. 1.02 Ga. both lacking inherited &gt;1.3 Ga components. The clasts have an unimodal zircon U-Pb age distribution, recording a crystallization event at ca. 1.2–1.27 Ga. Scarce inherited zircon cores between ca. 1.4–1.6 Ga were found, with only a few samples with a broader age distribution, suggesting a detrital protolith with zircon cores as old as ca. 1.8 and 2.4 Ga. No zircon overgrowths or geochemical-petrographic evidences are indicative of granulite metamorphism. Furthermore, all the studied metaigneous samples show discordant zircon ages produced by Pb loss events barely constrained between the latest Paleozoic to the Mesozoic.&#x0D; Hf isotopes reveal that zircon crystals from clasts have a range of εHf (1.25 Ga) ≈+1 to +5 and yield Hf model ages from 1.7 to 1.9 Ga. On the other hand, the The zircon Hf isotopes of one analyzed basement sample reveal a higher range of εHf (1.25 Ga) ≈+7 to +9, and Hf model ages from 1.5 to 1.6 Ga.&#x0D; Both ≈1.2 Ga and 1.02 Ga events are consistent with magmatic ages previously documented elsewhere in Oaxaquia, interpreted as indicating portions of the NW Amazonia-Oaxaquia arc system with cratonic influence or to slices of Baltica thrust over Oaxaquia during the Grenville orogeny. However, the absence of granulite facies indicators, such as zircon metamorphic ages and/or granulite paragenesis (typically, in other Oaxaquia samples, orthopyroxene and garnet) are interpreted as prime evidence that the studied samples didn’t undergo such high grade of metamorphism. Río Hondo gneisses, as this sequence is informally named, must belong to a source that had the influence of an older continental crust and can be tentatively associated either with rocks recently described in the Sierra de Juárez, or those belonging to the central basement of the Maya block, currently exposed farther to the SE in Chiapas.