Trace Element Compositions Research Articles

Garnet as Indicator of Pegmatite Evolution and Mineralisation: The Case Study of the Koktokay Pegmatites, Altai, NW China

ABSTRACTPegmatite‐related deposits are among the most crucial sources of rare‐metal elements such as Li, Be, Nb, Ta, Rb, Cs and Sn. Despite nearly 2 centuries of extensive study, the mechanism governing the rare‐metal mineralisation of pegmatites remains contentious. Alongside the enrichment of rare‐metal elements in the source region, differentiation processes after emplacement may have also contributed to the concentration and mineralisation of rare‐metal elements. However, compared to fractional crystallisation, limited attention has been directed towards the role of liquid immiscibility in pegmatite mineralisation. In this study, the major and trace element compositions of garnets in the internally zoned (Be‐rich) and un‐zoned (barren) pegmatites from the Koktokay pegmatite field in Altai, NW China, were analysed to evaluate the role of liquid immiscibility in the generation of rare‐metal mineralised pegmatites. The studied garnets belong to the almandine‐spessartine solid solution and are magmatic in origin. The inter‐ and intra‐crystal chemical variations observed for the studied garnets were produced by a combined effect of magmatic crystallisation and liquid immiscibility. The decrease in the spessartine component of garnets from the margins inward and the depleted MREE–HREE distribution patterns of garnet domains indicate the onset of liquid immiscibility, which correlates with the Be mineralisation of the internally zoned pegmatite. Therefore, the chemical variations in garnets from the Koktokay pegmatites suggest a clear genetic relationship between liquid immiscibility and rare‐metal mineralisation, and they are proposed as potential indicators for prospecting rare‐metal ore deposits.

Geology and antimony mineralization of the Yangla polymetallic orefield in northwestern Yunnan, SW China: Trace element geochemistry of sulfides and calcite

The Yangla is the largest and highest-grade antimony deposit (10 kt Sb @ 14.87 %) in the Jinshajiang suture zone, northwestern Yunnan (SW China). Pyrite and stibnite are the main sulfides, and calcite is the main gangue mineral in the antimony ores. Antimony mineralization can be divided into three stages: pre-ore stage pyrite and quartz, syn-ore stage (incl. early, main and late sub-stage) stibnite-pyrite-calcite-quartz, and supergene stage valentinite and limonite. The trace element compositions of the three pyrite and two stibnite generations have been analyzed by (LA-)ICP-MS here. The bulk ore-related calcite trace element compositions were also measured by ICP-MS. Trace element correlations and principal component analysis (PCA) show that the majority of trace elements occur as solid solution and micro-/nano-inclusions in pyrite and stibnite. In pyrite, the Sb substitutes into the crystal lattice with Tl, Cu and Ag via (Tl++Cu++Ag+) + Sb3+ ↔ 2Fe2+. Gold occurs as invisible gold (Au+) and enters pyrite via the coupled substitution of As3+Au3+□ ↔ 3Fe2+ and/or As3+Au3+□ ↔ 3Cu2+. In stibnite, the Cu, Pb and As enter the crystal lattice via the coupled substitution of 2Sb3+ ↔ Cu+ + Pb2+ + As3+. Trace element features of calcite are highly similar to the Devonian Linong Formation (2nd member) marble, suggesting that the ore-forming fluid is closely associated with the marble. Syn-ore calcite is characterized by its higher Fe, Mn and MREE concentrations than the pre-/post-ore calcite, and can be regarded as a geochemical fingerprint for metallogenic prediction. The δCe (0.67–0.83, avg. 0.75) and δEu (1.40–2.51, avg. 1.89) values suggest that the antimony precipitation occurred under reducing to weakly oxidizing conditions. The atomic Yb/Ca, Yb/La, Tb/Ca, and Tb/La ratios of the syn-ore calcite imply that the antimony mineralization can be attributed to hydrothermal genesis. This deduction is also supported by that data of pyrite Ⅰ, Ⅱ, and Ⅲ mainly plotted inside the hydrothermal fields in the Co/Ni, As/Ag, Sb/Bi and Co-Ni-As discrimination plots. The Yangla stibnite ore samples mimic stibnite from typical hydrothermal mineralization systems (e.g., Woxi Au-Sb-W deposit, South China) in the Cu vs. Pb plot, which further supports a hydrothermal origin of the antimony. Therefore, we propose that the hydrothermal Sb mineralization is closely related to the Devonian carbonate rocks at Yangla.

Reappraising the eruptive history of the Alchichica Maar Volcano (Mexico) based on Sr–Nd isotopes: Understanding the role of the magma source region on the growth of small-volume volcanoes

Alchichica Maar is in the eastern sector of the Trans-Mexican Volcanic Belt, where volcanics range from basalts to rhyolites, with 87Sr/86Sr and 143Nd/144Nd values between 0.70293 to 0.70447 (εSr = −21.1 to −4.5) and 0.512733 to 0.512949 (εNd = +3.4 to +6.2), respectively. In this study, Nd and Sr isotopic data and new major and trace elements compositions are provided for the lava flow, the scoria cone, and the phreatomagmatic deposits composing Alchichica Maar Volcano. These results are used in combination with published data to reexamine its eruptive history, though to be formed by more than one eruptive event. The cogeneticy of the magmas that fed the eruptions of these deposits is examined to infer the role of the deep magma source region and post-magmatic alterations on the construction of the Alchichica Maar magmatic system. Alchichica samples present 87Sr/86Sr values between 0.70387 and 0.70447 (εSr = −9.0 to −0.4) and 143Nd/144Nd values from 0.512749 to 0.512773 (εNd = +2.0 to +2.8). While the 87Sr/86Sr values suggest a slight increment in radiogenic 87Sr from the pre-maar lower lava flow to the upper maar eruptions indicative of magma contamination within the upper crust and by hydrodynamic mingling during the phreatomagmatic phases, the slight variation in Nd isotopes suggest an overall homogeneous source where small batches of magmas formed episodically to feed monogenetic eruptions, which subsequently yielded the pre-maar lava flow, the pre-maar surge, the scoria cone, and the maar units. This study reinforces the idea that an already “tapped” source region of a monogenetic volcano may become fertile again, and new eruptions can occur from near or old vent sites. It also highlights the hazardous potential of small-volume volcanoes.

Triassic–Jurassic alkaline magmatism in the Ivrea-Verbano Zone, Southern Alps: A zircon perspective on mantle sources and geodynamic significance

The Ivrea-Verbano Zone (IVZ; western Southern Alps) consists of a distinctive sequence of the lower continental crust of the Adriatic plate, extending down to the subcontinental lithospheric mantle. It is characterized by a large variety of intrusive bodies of variable geochemical composition and age, offering a unique insight into the evolution of mantle-derived magmatism in post-collisional and extensional geodynamic settings. In this study, we characterize a suite of alkaline dykes intruding a mantle massif – the Finero Phlogopite Peridotite in northern IVZ. These dykes include zircon-bearing diorites and anorthosites, mainly composed by HFSE-rich amphibole and phlogopite, albite (>90 vol% in anorthosites) and apatite. Zircon, monazite, ilmenite, titanite, Nb-rich oxides, and carbonates are common accessory minerals. Additionally, a “composite” diorite dyke containing both HFSE-rich and HFSE-poor amphiboles was investigated. The study is aimed at providing new trace element, UPb geochronological and LuHf isotopes dataset on zircon from these alkaline dykes, to refine the understanding of their mantle source characteristics, emplacement age and geodynamic implications. The trace element composition of zircons from the studied dykes points to segregation from melts with alkaline to ultra-alkaline affinity. Concordia UPb ages of zircon from the alkaline diorite dykes span from 221 to 191 Ma, which are interpreted as the result of multiple crystallization/recrystallization stages related to different magmatic pulses. Conversely, zircon from anorthosite and composite diorite dykes yield a narrow time range of 198–202 Ma, highlighting the occurrence of a magmatic pulse around ca. 200 Ma. The εHf(t) values (+13.4 to +5.7) of zircon from the alkaline diorite dykes are significantly more positive compared to the values in those from anorthosite and composite diorite dykes (+4.2 to −0.4), suggesting that the parental melts were derived from heterogeneous asthenospheric mantle sources with low to moderate amount of recycled continental crust components. Our data and reappraisal of the literature indicate that the IVZ experienced a protracted period of alkaline magmatism from ca. 235 Ma to 185 Ma. The melts migrated along mantle shear zones during the Triassic-Jurassic lithospheric extension. Different pulses of alkaline magmatism were associated with relevant extensional tectonic stages recorded by the continental crust, presumably triggering a passive uplift of heterogenous asthenospheric reservoirs over a front of at least 500 km. This tectono-magmatic cycle is a precursor to the focused rifting stage which caused the opening of the Jurassic Alpine Tethys, enhancing Pangea fragmentation.

Magnesium isotope constraints on the role of recycled carbonate-rich sediments in the formation of ultrapotassic magmatic rocks at a continental arc setting

The formation of orogenic ultrapotassic magmatism in a subduction setting is still unclear as it requires various co-processing mechanisms. To address this problem, especially to investigate the role of carbonate metasomatism in the mantle source, whole-rock Mg-Sr-Nd isotopic compositions have been measured for ultrapotassic magmatic rocks from the Central Pontides arc, northern Turkey, one of the rare examples of subduction-related ultrapotassic magmatism. These ultrapotassic rocks have relatively low (87Sr/86Sr)i (0.70461–0.70687) and εNd(t) (0.3 to 2.6) values and display much lower δ26Mg values (−0.73 ‰ to −0.19 ‰) than the normal mantle. The petrological and geochemical characteristics of the Pontide Ultrapotassic rocks (PUR) indicate that the low δ26Mg values do not result from surficial weathering, diffusion, or magmatic differentiation, but rather reflect the presence of distinct metasomatizing agent in their mantle source. The low Hf/Hf*, Ti/Ti*, Fe/Mn and Ti/Eu ratios, high Ca/Al and (Na2O + K2O)/TiO2 ratios, and lack of significant correlations between δ26Mg and Fe/Mn or (Gd/Yb)N suggest that the low δ26Mg values cannot be reconciled with the contribution of recycled carbonated eclogites, but are induced by the addition of carbonate-rich sediments to their mantle source. This interpretation is also supported by the significant (La/Yb)N vs. Ti/Eu and Hf/Sm vs. CaO/Al2O3 correlations for the ultrapotassic rocks. Using two end-member mixing calculations of MgSr isotopic compositions, the mantle source of PUR is constrained to contain varying proportions of carbonates, mostly of dolomite composition. The addition of carbonate-rich sediments to the mantle may have occurred at depths of 100–150 km as indicated by the trace element compositions of PUR. In this regard, the enrichment of K and other large ion lithophile elements in the ultrapotassic rocks can be induced by the contribution of silicic sediments. Meanwhile, carbonatitic melts can be formed through the partial melting of carbonate-rich sediments in the subducting oceanic slab, which then reacts with the overlying mantle to form carbonated peridotite that serves as the source of ultrapotassic rocks with low-δ26Mg, low-silica, and high LREEs. This study reports for the first time the Mg isotope data of ultrapotassic rocks formed in a continental arc setting and documents that carbonate-rich sediments play an important role in creating such rocks. Future work is needed to test whether this process is common in both oceanic arc and continental arc settings.

East–west-trending tearing of the Indian slab beneath the eastern Tibetan Plateau: Insights from Eocene–Oligocene potassic adakite-like granites in western Yunnan

Large-scale Eocene–Oligocene potassic adakite-like granites predominantly occur between 25° N and 27° N, north of the Ailaoshan suture in western Yunnan, eastern Tibetan Plateau. However, limited interpretations of their spatial characteristics hinder our understanding of the tectonic evolution in this region. Herein, we present new petrographic analyses, zircon UPb ages, whole-rock major and trace element compositions, SrNd isotopic data and zircon Hf isotopic mapping for these granites. Zircon UPb ages indicate that the adakite-like granites were emplaced at approximately 37.1–33.6 Ma. These granites exhibit high-K calc-alkaline compositions, enriched light rare earth elements and significant depletion in heavy rare earth elements, characterised by high Sr contents (667–1795 ppm), Sr/Y ratios (35–158) and La/Yb ratios (13–62), alongside low Y (8.2–23.3 ppm) and Yb (0.71–1.13 ppm) contents. The adakite-like granites possess high initial 87Sr/86Sr ratios (0.70596–0.70687) and low εNd(t) values (−5.73 to −0.65), with two-stage depleted mantle model ages (TDM2) ranging from 1.3 to 0.9 Ga. Their zircon εHf(t) values range from −5.1 to +0.7, with Neoproterozoic TDM2 ages of 1.4–1.1 Ga. Notably, these adakite-like rocks in western Yunnan exhibit an eastward decrease in zircon εHf(t) and whole-rock εNd(t) values. By integrating these findings with the Hf isotopic mapping results, we suggest spatial heterogeneity in lower crustal composition in western Yunnan. The lower crust in the western Yangtze block comprises Neoproterozoic arc roots, while the lower crust of the Simao block represents a superposition of Neoproterozoic and Permian–Triassic arc roots. Based on the abrupt changes in angle and depth of the eastward-subducting Indian slab, along with the spatial characteristics of the Eocene–Oligocene magmatism, we propose that east–west-trending tearing of the subducted Indian slab occurs along approximately 26° N beneath the eastern Tibetan Plateau.

Spicing up nutrition: investigation of trace elements in some spices locally sold in two markets in Kisumu-Kenya.

Spices are integral to Kenyan cuisine, adding depth of flavour and aroma to dishes. Information on the levels of macro- and micronutrients in these spices is scarce, as they are sold locally in Kisumu City, Kenya; however, these species have medicinal value. The study reports the trace elements composition of eight selected spices (black pepper, cloves, ginger, cardamom, turmeric, cumin, red chillies, and garlic) sold in two open-air markets in Kisumu City. The trace elemental compositions for Zn, Ca, Fe, S, K, Na, P, Mg, Mn, B, Co, Li, Cu, Pb, and Cd were analysed using inductively coupled plasma-optical emission spectrometry (ICP-OES). Ginger had the highest mean concentrations of most essential elements, K (5767.86 ± 43.44mg/kg), Mg (4615.36 ± 76.27mg/kg), B (132.08 ± 0.66mg/kg), Li (33.52 ± 0.84mg/kg), Mn (365.29 ± 2.22mg/kg), and Zn (70.44 ± 0.85mg/kg), followed by Ca (5290.44 ± 147.34mg/kg), Na (1361.88 ± 41.01mg/kg), P (3954.25 ± 122.68mg/kg), and S (4031.88 ± 106.95mg/kg), while turmeric had the lowest. The concentrations of macro-elements in spices from the Kibuye market were slightly higher than those from the Jubilee market; however, these differences were not statistically significant (p < 0.05). Concentrations of Pb and Cd heavy metals were detected and reported for all spices in the two markets, although the levels were below the WHO standard; hence, the spices are safe for use as supplements for essential trace elements in addition to their medicinal uses.

Apatite as an indicator of tectono-magmatic evolution of silica-undersaturated to silica-oversaturated rocks on the NW Indian Plate margin

Permo-Carboniferous intrusive rocks situated on the NW boundary of the Indian Plate between the Main Mantle Thrust (MMT) and Main Boundary Thrust (MBT) have tremendous potential for enhancing our knowledge of regional tectono-magmatic activity in Pakistan, yet these units have received only limited investigation to date. Here, we examine the petrology, apatite geochemistry and Sr-Nd isotopes, and geochronology of the silica-undersaturated (sodalite syenite and nepheline syenite), silica-saturated (monzonite and quartz syenite), and silica-oversaturated (granite and quartz monzonite) intrusive suites of the Ambela Granitic Complex (AGC) in northern Pakistan. Cathodoluminescent (CL) images of apatite in the three suites show mostly oscillatory zonation and a homogenous texture. The apatite chemistry of three intrusives is characterized by high fluorine (F), rare earth element (REE), yttrium (Y), and thorium (Th) contents, and low levels of chlorine (Cl), iron oxide (FeO) and magnesium oxide (MgO), suggesting a magmatic origin. The three suites exhibit variation in Sr-Nd isotopes, i.e., 87Sr/Sr86i = 0.7035 to 0.7057 and εNd(t) = +0.3 to +6.0 for the silica-undersaturated group, 87Sr/Sr86i = 0.7044 to 0.7205 and εNd(t) = +1.8 to +3.8 for the silica-saturated group, and 87Sr/Sr86i = 0.7075 to 0.7186 and εNd(t) = −2.5 to +1.2 for the silica-oversaturated group. Garnet stability field indicators in the nepheline syenite imply a deeply sourced magma, with Sr-Nd isotopic, and trace-element compositions of the apatite indicating formation in the subcontinental lithospheric mantle. In contrast, the silica-oversaturated melts formed during magma ascent through crustal interactions at a range of depths, with their apatites showing affinity with A-type granites. Apatite grains from the three magmatic groups show distinctive Sr, Eu and Y patterns, reflecting less fractionation of the silica-undersaturated and -saturated suites than of the silica-oversaturated suite. Furthermore, apatites of the former suites have higher Eu/Eu* and SO3 and lower Ce/Ce* than those of the latter suite, suggesting development under more oxidizing magmatic conditions. TDM2 ages demonstrate parent material of Mesoproterozoic to Neoproterozoic age, whereas LA-ICP-MS U-Pb dating of magmatic apatite indicates cooling of all suites concurrently at ∼322–262 Ma. The latter ages document significant magmatic activity in the study region during the Late Carboniferous to Middle Permian, probably in connection with rifting of the northern margin of the supercontinent Gondwana, leading to opening of the Neo-Tethys Ocean.

Formation Mechanism of Muji Travertine in the Pamirs Plateau, China

The Muji spring travertines, located in the Muji Basin in the eastern Pamirs Plateau, represent a typical spring deposit found on plateaus that is characterized by arid and semi-arid climatic conditions. However, its formation mechanisms remain poorly understood. This study aims to explore the recharge processes of the spring, the sedimentary environment, and the genetics of Muji spring travertines through a comparative analysis of conventional hydrochemistry, H-O stable isotope analysis of both spring and river water, and petrographic observation, as well as in situ analysis of major and trace elements present in calcite within travertines. The basin is surrounded by mountains with a topography that facilitates groundwater convergence within it. Carbonate-bearing strata are extensively developed around the basin, which serves as a crucial material foundation for travertine development. It infiltrates underground through fractures and faults, interacting with carbonate rocks to produce significant amounts of HCO3−, Ca2+, and Mg2+. The observed range of isotopic compositions (δ2H, −102.27‰ to −96.43‰; δ18O, −14.90‰ to −14.36‰) in water samples suggests that their primary origin was from glacial and snowmelt sources. The concentration of HCO3− in spring water samples exhibits significant variability, with the highest value being 1646 mg·L−1, which deviates significantly from the typical composition of karst groundwater. During its migration, groundwater undergoes the dissolution of gaseous CO2 derived from deep metamorphic processes, leading to variable degrees of mixing with geothermal groundwater containing elevated concentrations of dissolved components that enhance the dissolution potential of carbonate rocks. Eventually, upwelling occurs along the Southwestern Boundary Fault of Muji, resulting in the formation of linear springs characterized by CO2 escape. The Muji laminated travertines exhibit distinct white and dark laminae, and radial coated grains consisting of micritic and sparry layers. Chemical composition analyses reveal significant differences in the trace and rare-earth element composition, as well as the Mg/Ca ratio, of the two types of travertines. Specifically, the micritic laminae of the pisoid (Mg/Ca = 0.019; Sr = 530 × 10−6; Ba = 64.6 × 10−6) and the dark laminae of the laminated travertine (Mg/Ca = 0.014; Sr = 523 × 10−6; Ba = 48.1 × 10−6) exhibit generally higher Mg/Ca ratios and Sr, Ba contents than the neighboring sparry laminae (Mg/Ca = 0.012; Sr = 517 × 10−6; Ba = 36.6 × 10−6) and white laminae (Mg/Ca = 0.006; Sr = 450 × 10−6; Ba = 35.6 × 10−6). The development of laminated travertines and radial coated grains here is attributed to periodic changes in groundwater recharge induced by seasonal temperature fluctuations, as evidenced by the structural characteristics of the two types of travertines and the trace element analysis of different layers. Algae play a role in forming the dark laminae of laminated travertines and the micritic laminae of pisoids.

Long-Term Effects of Liming Sod-Podzolic Soil by Dolomite on the Microelement Composition of Plants &lt;i&gt;Hordeum&lt;/i&gt; L.

In a long-term precision microfield experiment, the effect of liming acidic sod-podzolic light loamy soil with dolorous flour (DF, dose range 0–2.0 Ha, 9th year of the aftereffect) on the soil reaction, the content of mobile compounds Zn, Cu, Mn, Fe, Cd, Pb in the soil, and the trace element composition of barley plants (Hordeum L.) was studied. It was revealed that the most sensitive to changes in the acid-base properties of the soil were Zn and Mn, the content of which in the organs of barley plants significantly decreased linearly in the dose range of DF 0–2.0 Ha. The consequence was significant even at the minimum dose of DF (0.2 Ha). There was a tendency to a decrease in the Fe content in straw and ear of plants (r = –0.572 and –0.570, respectively) in the indicated dose range. The data obtained confirmed that precipitation can lead to an increase in the Cd content in grain crops: in the dose range of DF 0.8–2.0 Ha, the increase in the element content in the ears of plants relative to the control variant of the experiment reached 1.6–2.0 times, and in straw increased linearly in the dose range of DM 0–1.0 Ha (r = 0.945), the content of Cu and Pb in barley plants was weakly dependent on the dose of liming agent.

X-ray fluorescence mapping of brain tissue reveals the profound extent of trace element dysregulation in stroke pathophysiology.

The brain is a privileged organ with regards to its trace element composition and maintains a robust barrier system to sequester this specialized environment from the rest of the body and the vascular system. Stroke is caused by loss of adequate blood flow to a region of the brain. Without adequate blood flow ischemic changes begin almost immediately, triggering an ischemic cascade, characterized by ion dysregulation, loss of function, oxidative damage, cellular degradation, and break down of the barrier that helps maintain this environment. Ion dysregulation is a hallmark of stroke pathophysiology and we observe that most elements in the brain are dysregulated after stroke. X-ray fluorescence-based detection of physiological changes in the neurometallome after stroke reveals profound ion dysregulation within the lesion and surrounding tissue. Not only are most elements significantly dysregulated after stroke, but the level of dysregulation cannot be predicted from a cell-level description of dysregulation. X-ray fluorescence imaging reveals that the stroke lesion retains<25% of essential K+ after stroke, but this element is not concomitantly elevated elsewhere in the organ. Moreover, elements like Na+, Ca2+, and Cl- are vastly elevated above levels available in normal brain tissue (>400%, >200%, and>150%, respectively). We hypothesize that weakening of the blood-brain-barrier after stroke allows elements to freely diffuse down their concentration gradient so that the stroke lesion is in equilibrium with blood (and the compartments containing brain interstitial fluid and cerebrospinal fluid). The changes observed for the neurometallome likely has consequences for the potential to rescue infarcted tissue, but also presents specific targets for treatment.

Trace Element Composition of Surface Water in Almaty City and Human Health Risk Assessment.

This investigation meticulously examined the elemental composition of 64 water samples collected during the seasons of spring, summer, autumn, and winter of the year 2023. The average seasonal concentrations of arsenic (As), beryllium (Be), cobalt (Co), cadmium (Cd), copper (Cu), lithium (Li), molybdenum (Mo), nickel (Ni), lead (Pb), selenium (Se), uranium (U), mercury (Hg), aluminum (Al), barium (Ba), chromium (Cr), iron (Fe), manganese (Mn), strontium (Sr), vanadium (V), zinc (Zn), calcium (Ca), potassium (K), magnesium (Mg), sodium (Na), and chlorine (Cl) as well as SO4 and dry residue were computed at 16 strategically selected sites along the Bolshaya and Malaya Almatinka, Esentai, and Kargalinka rivers situated in Almaty. The sampling locations were categorized into three distinct sectors: upper (adjacent to mountainous regions), middle (urban zone), and lower (exceeding city limits), thereby facilitating the examination of discrepancies in water quality and elemental concentrations. The results reveal that surface water resources in Almaty, particularly concerning As, Ni, Cr, U, and Pb, may present a considerable carcinogenic risk if utilized for consumption purposes. This is especially alarming given that these rivers constitute a vital source of drinking water for the inhabitants of the city. Specifically, at two sampling locations along the Bolshaya and Malaya Almatinka rivers in proximity to significant urban thoroughfares, untreated river water displayed an elevated carcinogenic risk (CR ~ 10-2). These results highlight the urgent necessity for enhanced water treatment and ongoing monitoring to safeguard public health.

Protracted magma evolution and transcrustal magmatic plumbing system architecture at Erta Ale volcano (Afar, Ethiopia)

Abstract The Afar region is one of the only places on Earth where magmatic continental rifting and associated ongoing break-up processes are exposed onshore. The several active magmatic segments there are characterized by contrasted morphologies, crustal thicknesses, magma production rates, and magma-tectonic styles. In the Erta Ale Range rift segment, extension is magmatically accommodated, making the range the ideal place to study the magmatic behavior of a mature rift segment. Erta Ale Range comprises sub-segments with magma compositions ranging from basalts to rhyolites, but only the Erta Ale Volcano (EAV) sub-segment is active, where only basaltic compositions have been reported so far. Here, we show for the first time protracted differentiation at EAV that is not expressed volcanically at the surface, but is rather accessible via unique cognate gabbroic and microgabbroic blocks, and recorded by mixing with erupted basaltic magmas. These cognate samples record previously unknown mushy and evolved parts of the EAV plumbing system. To constrain their origin and evolution, we measured the major and trace element compositions of the bulk rocks, interstitial glasses, and melt inclusions. We also measured the oxygen isotopic compositions of olivine crystals, interstitial glasses, and melt inclusions. By combining these results with textural relationships and oxy-thermo-barometry calculations, we discuss magma differentiation and storage conditions, as well as magmatic interactions during transport through the crust. Comparison of our results with rhyolite-MELTS thermodynamic models highlights that protracted fractional crystallization is the main process of magma evolution, and when associated with reactive porous flow is capable of forming the evolved compositions observed (up to 75 wt.% SiO2). We also use the model outputs to quantify distinct steps of igneous differentiation in both shallow and deep crustal reservoirs, and we highlight significant interactions with hydrothermally altered wall rocks. We discuss this model within the geological contexts of the Erta Ale Range rift segment and the larger Afar region, and highlight contrasts with mature oceanic systems to argue that the region is not in the final stages of continental break-up.

Unlocking the Potential of Isopropanol as an Eco-Friendly Eluent for Large-Scale Fractionation of Fulvic Acids via Preparative Reversed-Phase High-Performance Liquid Chromatography and Multidimensional RP-HPLC: Evaluation of Molecular Diversity and Element Composition.

Humic substances are organic mixtures of extreme complexity, which significantly complicate their analysis by any method. Fractionation into more homogeneous mixtures seems to be almost the only way to overcome these difficulties. Preparative high-performance liquid chromatography (HPLC) provides almost any amounts of substances required for both further fractionation and studies by other methods. For the first time, isopropyl alcohol (IPA) is proposed for these purposes; its advantages are shown by the example of groundwater fulvic acids (FA). IPA is much safer than conventional solvents and elutes the most nonpolar compounds that are nonelutable by methanol and acetonitrile. The isolated fractions differ significantly in their molecular composition, which is confirmed by ultrahigh-resolution mass spectrometry and molecular spectroscopy. Stepwise IPA-gradient HPLC-UV analysis of each preparative fraction demonstrates the possibilities of multidimensional HPLC for FA. The isolated fractions were studied for contents of a broad range of elements, and the relationships between the molecular and trace-element compositions of the fractions were revealed. Our data reveals the existence of numerous and different organometal compounds in FA composition; thus, the proposed approach can be used for a more in-depth study of the mechanisms of element migration in the environment.

Mesozoic lithospheric mantle evolution in South China: Evidence from Ar-Ar dating, geochemistry and Sr-Nd-Pb isotopes of lamprophyres

Understanding the Mesozoic lithospheric mantle beneath South China is challenging, primarily because mantle-derived magmatic rocks are rare, whereas granitic magmatism is far more abundant. In this study, we present new 40Ar/39Ar geochronology, major and trace elemental composition, and Sr-Nd-Pb isotopic data for lamprophyres from northern and central Guangxi Province, South China. Our results reveal two intrusion phases: an earlier phase at 207.7 ± 1.2 Ma, and a later phase between 95.6 ± 0.6 Ma and 102.3 ± 0.7 Ma. The earlier phase, represented by the Danyang lamprophyres, is marked by low Cr (330–355 ppm) and Ni (241–258 ppm) contents and strongly fractionated REE patterns with (La/Yb)n ratios of 57.5 to 62.8. The later phase, represented by the Leidong, Nongchang, and Longchang lamprophyres, shows higher Cr (490–781 ppm) and Ni (237–377 ppm) contents, with less fractionated REE patterns and (La/Yb)n ratios of 20.2 to 27.8. Despite their temporal differences, the lamprophyres share similar isotopic characteristics, including high initial 87Sr/86Sr (0.707940–0.721310), negative εNd(t) (−9.19 to −5.31), and radiogenic Pb isotopic compositions (206Pb/204Pb: 18.200–18.331, 207Pb/204Pb: 15.62–15.72, 208Pb/204Pb: 38.53–38.84). These features suggest derivation from low-degree partial melting of a phlogopite-bearing, refractory peridotite lithospheric mantle, modified by olivine and clinopyroxene fractionation. This refractory mantle was metasomatically enriched by Proterozoic subduction processes beneath the Yangtze Craton. By synthesizing published Sr-Nd-Pb isotopic data, we propose that the lithospheric mantle beneath South China shifted from enriched to depleted mantle between ∼220 Ma and ∼ 100 Ma, possibly due to extension associated with the subduction and rollback of the Paleo-Pacific Plate.

Matrix Corrected SIMS In Situ Oxygen Isotope Analyses of Marine Shell Aragonite for High Resolution Seawater Temperature Reconstructions

AbstractMarine shells incorporate oxygen isotope signatures during growth, creating valuable records of seawater temperature and marine oxygen isotopic compositions. Secondary ion mass spectrometry (SIMS) measures these compositions in situ at finer length‐scales than traditional stable isotope analyses. However, determining oxygen isotope ratios in aragonite, the most common shell mineral, is hampered by a lack of ideal reference materials, limiting the accuracy of SIMS‐based seawater temperature reconstructions. Here, we tested the capability of SIMS to produce seawater temperature reconstructions despite the matrix calibration challenges associated with aragonite. We cultured Anadara trapezia bivalves at four controlled seawater temperatures (13–28°C) and used strontium labeling to mark the start of the temperature‐controlled shell increment, allowing for more spatially precise SIMS analysis. An improved matrix calibration was developed to ensure more accurate bio‐aragonite analyses that addressed matrix differences between the pure abiotic reference materials and the bio‐aragonite samples with intricate mineral‐organic architectures and distinct minor and trace element compositions. We regressed SIMS‐IRMS biases of abiotic and biogenic aragonites that account for their systematic differences in major, minor, and trace elements, allowing for more accurate SIMS analyses of the temperature‐controlled shell increment. The thorough matrix calibration allowed us to provide a SIMS‐based seawater‐corrected oxygen isotope thermometer of T(°C) = 23.05 ± 0.36 − 4.48 · (δ18Oaragonite [‰ VPDB] − δ18Oseawater [‰ VSMOW] ± 0.25) and 103lnαaragonite‐seawater = (17.78 ± 0.88) · 103/T (K) − (29.44 ± 2.40) that agrees with existing aragonitic IRMS‐based thermometer relationships and improves the applicability of SIMS‐based paleo‐environmental reconstructions of marine bio‐aragonites.

The mid-Cretaceous Hohonu Batholith (South Island, New Zealand): Identifying magmatic sources and processes during onset of crustal extension

The Hohonu Batholith is an aggregation of mostly mid-Cretaceous granitoid plutons on the West Coast of the South Island of New Zealand emplaced during a transitional period between subduction-related compression and continental lithospheric extension. This study reports an integrated dataset, comprising in-situ UPb, O and Hf isotope compositions and REE, Ti and other trace and major elements (ZrHf, ThU) for zircons extracted from four representative plutons within the batholith. Our results provide detailed insight into the protracted thermal, chronological and geochemical histories. LA-ICPMS UPb zircon ages indicate a primary episode of magma genesis and emplacement from 107 to 113 Ma, confirming published SIMS dating. However, a younger previously unrecognized age population of ~91–96 Ma is identified, primarily (although not exclusively) in zircon rims. This younger age event coincides with the timing of protracted lithospheric extension and crustal thinning of the Zealandia continent. The cryptic younger zircon ages suggest that Hohonu granitoids experienced a partial thermal overprint (accompanied by Pb loss) mostly recorded in rims. Differences in bulk rock geochemistry between plutons are inferred to reflect variable conditions of partial melting controlled by source mineralogy and H2O content. Isotope and trace element compositions, along with Ti-thermometry, measured on the same micro-volume of CL-imaged zircons, are used to test if source characteristics were imparted from melt to minerals in zircon-saturated silicic systems. Similarities are revealed in the zircon record of the selected plutonic rocks, confirming their broadly consanguineous relationship and the fundamental role of open-system behaviour, involving hybridization or assimilation between mantle-derived (or juvenile mafic) and a crustal-derived components, as previously inferred from whole rock NdSr isotope systematics. However, intra-sample decoupling of zircon OHf isotope systematics may also be linked to residual source component unmixing. This possibility, in addition to mafic recharge, may have obscured melt source compositional characteristics, and hence zircon REE appear as unsuitable fingerprints of source(s) and conditions of partial melting in this granitoid system. Simple compositional and thermal magma evolution trends appear punctuated by episodes of mafic recharge, presumably during lithospheric thinning.

In-situ trace element and sulfur isotope compositions of Multi-Stage sulfides in the Buzhu orogenic gold (Antimony) Deposit, southern Tibet: Implications for the metallogenic process

The Buzhu gold (antimony) deposit, located within the gold-antimony polymetallic belt of southern Tibet in the Tethys Himalayan belt, is a recently discovered medium-sized gold polymetallic deposit. The orebody consists primarily of gold-bearing quartz sulfide veins. Currently, the metallogenic mechanism of the deposit remains largely unexplored. Utilizing results from the mineralogical observation of principal ore minerals, LA-ICP-MS trace element analysis, and in-situ sulfur isotope analysis of pyrite, investigations reconstruct the evolution process of pyrite-arsenopyrite and constrain the metallogenic process of the Buzhu gold (antimony) deposit. It has been discovered that the gold-bearing sulfides in the Buzhu gold (antimony) deposit are primarily pyrite and arsenopyrite. Pyrite can be categorized into six generations: framboidal pyrite Py0, dissolution cavity pyrite Py1a (some exhibiting oscillatory zoning), disseminated pyrite Py1b, euhedral pyrite Py2a, irregular pyrite Py2b, and Py3. Arsenopyrite, on the other hand, can be classified into three generations: early arsenopyrite Apy0, disseminated arsenopyrite Apy1, and euhedral Apy2. The analysis of δ34S in pyrite throughout the ore-forming process indicates sulfur derives from multiple sources, with Py0 indicative of a biological sulfur source. The evolutionary process of pyrite, supported by trace element analysis, suggests that the remaining pyrite derives from sedimentary fluid transformation, with sulfur primarily sourced from metamorphic sediments. Elemental spectrum analysis and BSE observations indicate that the Buzhu gold (antimony) deposit primarily undergoes two distinct stages of mineralization: the initial stage is the gold-antimony mineralization phase, during which antimony precipitates in the fissures of Py1a as stibnite, while gold is primarily found in Py1-Apy1 as invisible gold, with the highest gold content in Apy1 (28.20–60.13 ppm, average 40.51 ppm). The subsequent stage of mineralization is characterized by gold mineralization, with gold primarily residing in the internal fissures of Apy2 as micron silver gold ore. The evolution characteristics of gold-bearing sulphide and the solubility curve of Au indicate that gold mainly derives from gold-bearing unsaturated fluid, rather than from early framboidal pyrite Py0 (0.52–1.06 ppm, average 0.79 ppm). Only a minor fraction of gold (originating from early sediments) in Py0 was liberated and integrated into subsequent pyrites. The content of antimony in Py0 significantly reduces after dissolution, suggesting that antimony predominantly originates from Py0 (206–440 ppm, average 335 ppm). Throughout the genesis of the Buzhu gold (antimony) deposit, the gold constituent underwent a sequence of pre-enrichment, re-enrichment, liberation, and precipitation. The processes of coupled dissolution-reprecipitation (CDR) and boiling fostered the reactivation and reenrichment of gold. The recrystallization into cubic pyrite led to the expulsion of gold from the pyrite lattice, and fluid oxidation resulting from multistage fluid boiling, coupled with a decrease in sulfur fugacity, led to gold precipitation.

Tectonic Implications of Early Permian Arc Rocks and Their Cretaceous to Early Cenozoic Reworking in Southern Lhasa Terrane, Tibet

AbstractThe Lhasa terrane in southern Tibet occupies a central position in Asian tectonics, yet its pre‐Mesozoic petrologic and tectonic evolution is poorly constrained, especially the Southern Lhasa subterrane (SLS). Here, new zircon U–Pb ages, zircon trace element and Hf isotopic compositions, and whole‐rock geochemical data for mafic meta‐igneous rocks from the SLS distinguish three tectono‐thermal events at ∼290 Ma, ∼126 Ma and ∼49 Ma. Whole‐rocks and zircons with ages of the two older events have arc magma geochemistry, but Hf isotopes are distinct from Mesozoic Gangdese arc magmas. Zircon cores and, arguably, whole rocks instead derive from ∼290 Ma magma formed during southward subduction of Paleo‐Tethys beneath the SLS. These rocks later underwent Early Cretaceous (∼126 Ma) remelting and early Cenozoic (∼49 Ma) metamorphism with P–T conditions of ~800°C and 15.3 kbar, and record a retrograde P–T path characterized by exhumation with cooling, consistent with a collisional origin. These data suggest Permian igneous rocks underwent reworking during both the Early Cretaceous and the early Cenozoic, reaching crustal thicknesses of at least ~50 km during the early Eocene. Combined with regional data, Paleo‐Tethys evidently experienced early Permian double‐sided subduction within the Lhasa terrane, with back arc basins forming between the SLS and the Indian margin to the south. These back arc basins ultimately widened to form the Neo‐Tethys Ocean, which then subducted during the Mesozoic, leading to Cretaceous arc magmatism and overprinting, followed by early Cenozoic metamorphism and final reworking during collision with India.

Gold and antimony metallogenic relationship of the Awanda Au (Sb) deposit, South Tianshan, NW China: Constraints from textures, in-situ trace elements and s-pb isotope systematics

The Tianshan is one of the most important gold ± antimony metallogenic province in the world. However, the relationship between Au and Sb mineralization remains poorly understood, largely due to lacking of systematic investigation on typical Au-Sb deposits. Here, we reported in-situ trace elements and S-Pb isotopic dataset on the Awanda Au (Sb) deposit, which is currently the second largest gold deposit in Chinese South Tianshan, and contain highly antimony (Sb) by our new petrographic observations. Sulfide from two minelization stages, i.e., Stage Ⅰ (arsenopyrite, pyrite, pyrrhotite, and minor chalcopyrite) and Stage II (gudmundite, aurostibite and stibnite), were analyzed using laser ablation inductively coupled plasma-mass spectrometry (LA-ICP-MS) and laser ablation multi-collector inductively coupled plasma mass spectrometry (LA-MC-ICP-MS). Trace element compositions reveal that ore minerals display positive correlations between As and Au-Sb-Cu-Zn-Pb, implying a common source for these elements. In situ δ34S values of sulfides that cluster in the range of − 2.94 to + 0.8 ‰, suggesting that sulfur contained in Au-As-Sb-bearing fluids were most likely derived from Upper Paleozoic sediments (δ34S = − 1.6 to + 0.3 ‰) during regional metamorphism. In-situ 206Pb/204Pb, 207Pb/204Pb and 208Pb/204Pb ratios (17.882 to 18.002, 15.467to 15.620 and 37.831 to 38.344) from sulfides are also support that the Upper Paleozoic strata may have supplied substantial metals. Combined with published electron microprobe and fluid inclusions data, our textural and chemical data suggest that fluid-rock interaction and decrease in pressure, temperature, and oxygen-sulfur fugacity were the main cause for Au-As and Au-Sb minelization, respectively. In summary, we propose that the Awanda Au (Sb) deposit fits the crust metamorphic model with Au-As and Au-Sb mineralization occur at mesozonal and epizonal depths, respectively.