Chemical Geology最新文献

{"title":"Quantification of the REE3+ aqua ions and chloride species in aqueous fluids by in situ Raman spectroscopy using perturbations of the water band","authors":"Bryan J. Maciag ,&nbsp;Alexander P. Gysi ,&nbsp;Nicole C. Hurtig","doi":"10.1016/j.chemgeo.2025.122684","DOIUrl":"10.1016/j.chemgeo.2025.122684","url":null,"abstract":"<div><div>Acidic NaCl-rich aqueous fluids play a crucial role in forming hydrothermal rare earth elements (REE) mineral deposits. Aqueous REE mobility is mostly controlled by the stability of REE³⁺ and REE chloride species. Our current knowledge of REE speciation is based on solubility data, thermodynamic models and <em>in situ</em> spectroscopic measurements, sometimes coupled with molecular simulations. Here we investigate Nd and Yb speciation in pH 2 chloride-bearing solutions at 25 °C and 0.1 MPa with variable Cl/REE ratios using Raman spectroscopy in solutions with 0.1 to 0.6 mol/kg NdCl₃ or YbCl₃ and 0.2 to 3.2 mol/kg NaCl. Due to the challenges in resolving the REE-Cl band, we develop a new method using the water vibrational mode and multivariate curve resolution (MCR) analysis. The Raman spectra for the vibrational band of water (2700 to 3900 cm⁻¹) were collected at 25 °C and fitted by three Gaussian sub-peaks, then quantified using MCR analysis to de-convolute the water band into bulk H₂O and the perturbations caused by of Cl⁻, REE³⁺, and REE chloride species. REE speciation based on the perturbations of the water band indicates that REE³⁺ aqua ions dominate in acidic solutions at 25 °C, but up to ∼20 mol% YbCl²⁺ forms at high YbCl₃ concentrations. The new method is promising for quantifying <em>in situ</em> speciation of the REE³⁺ aqua ions and REE chloride species in aqueous fluids while providing information on the hydration of ions. This method improves our molecular level understanding of REE aqueous species and their role in REE mobilization during fluid-rock interaction.</div></div>","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"679 ","pages":"Article 122684"},"PeriodicalIF":3.6,"publicationDate":"2025-02-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143512016","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Cl, Br and I measurements in rock samples by ICP-MS/MS using reaction gases","authors":"Benoît Villemant ,&nbsp;Julie Noël ,&nbsp;Benoît Caron","doi":"10.1016/j.chemgeo.2025.122681","DOIUrl":"10.1016/j.chemgeo.2025.122681","url":null,"abstract":"<div><div>Analysis of chlorine (Cl), bromine (Br) and iodine (I) in poorly concentrated geological materials remains a major analytical challenge. Analysis of halogens extracted in solution using single quadrupole ICP-MS is highly sensitive but suffers from numerous mass interferences. Experimental determination of species potentially interfering with halogens when analyzing silicates shows that mass interferences with ³⁵Cl are low (&lt;1 % of the ³⁵Cl signal) but that ³⁷Cl signal is completely hidden by ¹⁹F- oxides and ¹H<img>³⁶Ar signals. Mass interferences with Br isotopes signals may be up to 20 times higher in Br-poor, K-rich or REE-rich samples: they are mainly due to [⁴⁰Ar³⁹K]⁺ and [¹⁵⁸Gd]⁺⁺ for ⁷⁹Br and to [¹⁶²Dy]⁺⁺ for ⁸¹Br. Due to the low abundance of ¹²⁷I, mass interferences are always significant and mainly due to argides and chlorides: [³⁶Ar⁹¹Zr]⁺, [³⁸Ar⁸⁹Y]⁺, [⁴⁰Ar⁸⁷Rb]⁺, [⁴⁰Ar⁸⁷Sr]⁺, [³⁵Cl⁹²Zr]⁺, [³⁷Cl⁹⁰Zr]⁺. In addition, matrix effects combined to solvent molarity (NH₄OH or HNO₃) may significantly affect halogens ionisation leading to possible systematic bias in halogens analysis. The use of a triple quadrupole mass spectrometer (ICP-MS/MS) with H₂ and N₂O reactions/collision gases allows the reduction of all interferences and matrix effects to values lower than analytical errors. ³⁵Cl and ³⁷Cl are measured through the reactant species ClH₂⁺ in H₂ reaction mode, and ⁷⁹Br rand ⁸¹Br are measured through BrO⁺ species in N₂O reaction mode. ¹²⁷I is measured in N₂O collision mode that slightly reduces argides and chlorides species and significantly increases the ¹²⁷I signal by collision focusing.</div><div>Sample digestion in NH₄HF₂ and dissolution of the residue in NH₄OH (He et al., 2019) allow a simple and complete recovery of all halogens. Combined with ICP-MS/MS and gas reactions, the technique improves the precision and detection limits of halogen measurements by an order-of-magnitude compared to the currently reported performances of single quadrupole ICP-MS measurements. A set of international standard reference materials (ISRM) that cover a large range of halogen compositions are analysed: basalts BIR-1, BCR-1, BHVO-2, andesites AGV-1 and AGV-2, rhyolites RGM-1, ATHO and JR-1, minerals, marine sediment, soil, copper deposit and NIST-610 and -612 glass standards.</div></div>","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"681 ","pages":"Article 122681"},"PeriodicalIF":3.6,"publicationDate":"2025-02-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143643427","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Mo isotope evidence for the significance of subducted continental crust in formation of post-collisional porphyry Cu deposits","authors":"Jing Jing Fan ,&nbsp;Qiang Wang ,&nbsp;Xiao Ping Long ,&nbsp;Derek A. Wyman ,&nbsp;Andrew C. Kerr ,&nbsp;Jie Li ,&nbsp;Zi Long Wang ,&nbsp;Lin Gong ,&nbsp;Dong Jing Xu ,&nbsp;Qi Ji Yang ,&nbsp;Le Zhang ,&nbsp;Ze-Xian Cui","doi":"10.1016/j.chemgeo.2025.122683","DOIUrl":"10.1016/j.chemgeo.2025.122683","url":null,"abstract":"<div><div>Porphyry systems in continental collision belts contain substantial copper (Cu) and molybdenum (Mo) resources. However, unraveling their magma source compositions poses a significant challenge due to the superposition of previous oceanic subduction fingerprints. We report Mo isotope data on post-collisional (Oligocene–Miocene) Cu (Mo)-bearing porphyries (CBPs) and related barren-ore rocks (including Eocene granites and Miocene high-Mg diorites and ore-barren granites) in the eastern Gangdese belt, southern Tibet. The Eocene granites with high δ^98/95Mo values (0.37–0.58 ‰) and K₂O, Th contents originated from anoxic sediment-modified juvenile lower crust related to oceanic subduction. The Miocene high-Mg diorites with shoshonitic characteristic have extremely low δ^98/95Mo of −1.20 ‰ to −0.92 ‰, possibly deriving from a lithospheric mantle metasomatized by slab melts from subducted Indian crust. By contrast, the CBPs show moderate and variable δ^98/95Mo values (−0.85 ‰ to 0.34 ‰), reflecting either source or magma mixing of juvenile Asian lithosphere and subducting continental crust-derived melt components. The Miocene ore-barren granites have element compositions similar to the CBPs but are more Na-rich and have lower Th contents, slightly depleted Sr-Nd isotopes, and heavy Mo isotopes (−0.14 ‰ to 0.23 ‰), implying lower amounts of continental components in their magma source. Our Mo isotope data thus provides solid evidence for the incorporation of subducted Indian slab melts into the CBP magmas. Furthermore the CBPs contain more Indian components than the Miocene ore-barren granites, suggesting that the input of subducted continental crust melts is critical in the formation of post-collisional porphyry systems possibly by oxidizing the overlying fertile lithosphere.</div></div>","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"680 ","pages":"Article 122683"},"PeriodicalIF":3.6,"publicationDate":"2025-02-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143444930","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Characterizing sedimentary organic carbon in a hydrothermal spreading center, the Escanaba Trough","authors":"Hope L. Ianiri,&nbsp;Pamela L. Campbell,&nbsp;Amy Gartman,&nbsp;Nancy G. Prouty","doi":"10.1016/j.chemgeo.2025.122679","DOIUrl":"10.1016/j.chemgeo.2025.122679","url":null,"abstract":"<div><div>Sediments in critical marine mineral environments are of wide importance due to their preservation of both marine minerals and organic carbon (OC) stocks. However, OC storage and cycling is often overlooked in mineral system studies. This work characterizes sedimentary OC within the Escanaba Trough, a hydrothermal sulfide system off the coast of northern California. By utilizing ROV-based push coring, we collected sediments near and far from high temperature, low temperature, and inactive vents. We applied a multipronged organic geochemical approach, measuring bulk sediment, OC fractions of varying labilities, and biomarkers to tease apart the storage, source, and cycling of OC within this complex system. In contrast to past work indicating a primarily terrestrial source to deeper, Pleistocene sediments, our results suggest a primarily marine source in surface sediments at least 50 m away from active venting. Near active venting, we see evidence of locally produced chemosynthetic OC in addition to the background marine source. This chemosynthetic OC appears to be rapidly remineralized and supports more complex deep-sea food webs compared to hemipelagic sites. Still, the greatest contribution of labile OC was observed at inactive vent sites, which we suggest is due to hydrothermal fluid alteration of more labile OC at actively venting sites. Depending on fluid temperature, hydrothermally altered OC is either preserved in the sediments as petroleum or migrated with fluid flow. Considering inactive sites are those most likely to be targeted by potential mining, we suggest additional studies could verify if these results apply at other sedimented seafloor massive sulfide systems.</div></div>","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"679 ","pages":"Article 122679"},"PeriodicalIF":3.6,"publicationDate":"2025-02-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143453028","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Methanogenesis rather than carbon dioxide production drives positive priming effects in anoxic sediments of saline lakes","authors":"Jian Yang ,&nbsp;Pingping Zhang ,&nbsp;Min Cai ,&nbsp;Mingxian Han ,&nbsp;Zenghui Wu ,&nbsp;Haiyi Xiao ,&nbsp;Jibin Han ,&nbsp;Xiying Zhang ,&nbsp;Hailiang Dong ,&nbsp;Hongchen Jiang","doi":"10.1016/j.chemgeo.2025.122680","DOIUrl":"10.1016/j.chemgeo.2025.122680","url":null,"abstract":"<div><div>Priming effect is an essential mechanism regulating global organic carbon storage. The generation of priming effects has been exclusively investigated in anoxic sediments of freshwater lakes and in oxic sediments of saline lakes. However the differences in priming effect generation between oxic and anoxic saline lake sediments remain unclear. Here, we investigated the effects of algal and grass organic matter additions on priming effects under oxic and anoxic conditions in saline lake sediments. Sediment microcosms from three saline lakes with different salinities were amended with algal (¹³C-labeled <em>Chlorella vulgaris</em>) and grass (¹³C-labeled <em>Festuca ovina</em>) organic matter and incubated under oxic and anoxic conditions for 7 days to estimate priming effect intensities for CO₂ and CH₄ production. The results showed that algal and grass organic matter additions promoted higher CO₂ production under anoxic conditions than under oxic conditions, with grass organic matter inducing more CO₂ production than algal organic matter. Under oxic conditions, both algal and grass OM additions induced positive priming effects for CO₂ production, while negative priming effects were observed under anoxic conditions. In contrast, positive priming effects for CH₄ production were found in all anoxic microcosms. Our study highlights the importance of OM mineralization and positive priming effects for CH₄ production in anoxic sediments of saline lakes, which should not be overlooked given the high global warming potential of CH₄ and the increasing anoxia in global lakes due to climate change.</div></div>","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"678 ","pages":"Article 122680"},"PeriodicalIF":3.6,"publicationDate":"2025-02-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143394338","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Chalcophile and siderophile element (CSE) partitioning between sulfide liquid and silicate melt and the role of the “Hadean matte”","authors":"Mingdong Zhang ,&nbsp;Yuan Li","doi":"10.1016/j.chemgeo.2025.122671","DOIUrl":"10.1016/j.chemgeo.2025.122671","url":null,"abstract":"<div><div>This study evaluates the role of mantle-to-core segregation of the “Hadean matte” (sulfide liquids) occurring in the solidifying magma ocean in determining the chalcophile and siderophile element (CSE) abundances of the silicate Earth. The partition coefficients of CSEs between sulfide liquid and basaltic to peridotitic melt (<span><math><msubsup><mi>D</mi><mi>CSE</mi><mrow><mi>Sul</mi><mo>/</mo><mi>Sil</mi></mrow></msubsup></math></span>) were determined at 1–14 GPa and 1300–2100 °C. The variations in the obtained <span><math><msubsup><mi>D</mi><mi>CSE</mi><mrow><mi>Sul</mi><mo>/</mo><mi>Sil</mi></mrow></msubsup></math></span> (30–160 for Co, 50–1200 for Ni, 40–940 for Cu, 20–210 for Mo, 50–210 for Ag, 20–90 for Cd, 4–60 for In, 30–150 for Sb, 3900–30,000 for Re, 15–210 for Pb, 140–1700 for Bi, 0.3–7 for Zn, 0.7–7 for Ge, and 0.1–0.9 for Ga) can be explained and parameterized as a function of the experimental pressure, temperature, and composition of the silicate melt and sulfide liquid. Application of the <span><math><msubsup><mi>D</mi><mi>CSE</mi><mrow><mi>Sul</mi><mo>/</mo><mi>Sil</mi></mrow></msubsup></math></span> parameterization to the mantle-to-core segregation of sulfide liquids in a deep magma ocean at 75 GPa shows that less than 10 % of each of Co, Ni, Cu, Zn, Ga, Ge, Mo, Ag, Cd, In, Sb, Pb, and Bi in the silicate Earth can be sequestered in the core; whereas, in a shallow magma ocean at 10 GPa, 50–80 % of each of Cu, Ag, and Bi and less than 50 % of the other CSEs can be sequestered in the core. In contrast, mantle-to-core segregation of sulfide liquids could have extracted more than 90 % of the Re in the silicate Earth in both cases, requiring the addition of a late veneer to explain the present-day mantle value. Our results demonstrate that if Earth's volatile CSEs (Cu, Zn, Ga, Ge, Ag, Cd, In, Sb, Pb, and Bi) were delivered when metal segregation to the core was largely inactive, the depletion pattern of volatile CSEs relative to the lithophile elements of similar volatility in the silicate Earth cannot be explained by mantle-to-core segregation of sulfide liquids. Also, previous models that used mantle-to-core segregation of sulfide liquids as an important approach to explain the depletion of volatile CSEs in the silicate Earth need to be re-examined.</div></div>","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"679 ","pages":"Article 122671"},"PeriodicalIF":3.6,"publicationDate":"2025-02-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143402021","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Indian ocean-type mantle domain in the Carboniferous Qushiman ophiolite in the Northern Pamir: Significance for the intra-oceanic subduction in the Paleo-Tethys Ocean","authors":"Yan Jing ,&nbsp;Chuan-Lin Zhang ,&nbsp;Chen Wang ,&nbsp;Masumeh Sargazi ,&nbsp;Zhi-Hao Song ,&nbsp;Yi-kang Quan ,&nbsp;Zhi-Kai Xu ,&nbsp;Xiao-Qiang Liu ,&nbsp;Hong-Ran Wang","doi":"10.1016/j.chemgeo.2025.122677","DOIUrl":"10.1016/j.chemgeo.2025.122677","url":null,"abstract":"&lt;div&gt;&lt;div&gt;The opening, oceanic subduction, and final closure of several branches of the Paleo-Tethys Ocean provide significant constraints on reconstruction of the Central Asian blocks in Pangea. Although it has been generally agreed that the Triassic Tanymas ophiolite represents the relic of the Paleo-Tethys oceanic crust, the initiation of subduction and final closure of the Paleo-Tethys Ocean in the Pamir Plateau remain equivocal, which hampers further understanding of the Tethys tectonic domain. Here we present field investigations, zircon U&lt;img&gt;Pb ages, and whole-rock geochemistry and Sr-Nd-Pb-Hf isotopic data of the newly identified Qushiman supra-subduction zone (SSZ)-type ophiolite in the Northern Pamir in order to address the integrated evolution of the Paleo-Tethys Ocean in this less known Tethyan. The Qushiman ophiolite mainly consists of serpentinite, gabbro, basalt, diorite, plagiogranite, amphibolite, granulite, and schist. Zircons U&lt;img&gt;Pb dating of the gabbro yielded ages of 320–319 Ma. Both the gabbros and amphibolites exhibit typical fore-arc basalts (FAB) affinities with depleted Sr-Nd-Hf isotopic compositions, high &lt;sup&gt;207&lt;/sup&gt;Pb/&lt;sup&gt;204&lt;/sup&gt;Pb and &lt;sup&gt;208&lt;/sup&gt;Pb/&lt;sup&gt;204&lt;/sup&gt;Pb ratios, flat chondrite-normalized rare earth element (REE) patterns but remarkable low Nb/La ratios (0.21–0.29) for the gabbros. Their higher &lt;sup&gt;208&lt;/sup&gt;Pb/&lt;sup&gt;204&lt;/sup&gt;Pb and &lt;sup&gt;207&lt;/sup&gt;Pb/&lt;sup&gt;204&lt;/sup&gt;Pb ratios are comparable to those of Indian MORB, indicating the presence of the DUPAL anomaly in the Pamir Plateau of the Paleo-Tethys domain. These geochemical features argue that the gabbros and amphibolite were likely derived from partial melting of depleted mantle wedge source with involvements of 2 % pelagic sediments. These FAB-like gabbros and amphibolites, together with magmatic flare-up at 320 Ma in the Pamir Plateau archived initial subduction of the Paleo-Tethys Ocean. The basalt samples exhibited ocean island basalt (OIB)-like geochemical signatures with enrichment of light rare earth element (LREE), positive anomalies of Nb, Ta, Zr, and Hf, and markedly enriched Sr&lt;img&gt;Nd isotopic compositions, indicating partial melting of enriched mantle wedge. The diorites characterized by high MgO contents were likely derived from mantle wedge peridotite metasomatized by fluids derived from subducting oceanic slab. These magmatic assemblages of FAB-like gabbros and amphibolites, OIB-like basalts and high-Mg diorites, as well as geochemical transitions from normal mid-ocean ridge basalt (N-MORB)-like to arc-style affinities in the Qushiman ophiolite are analogous to those of the modern Izu-Bonin-Mariana intra-oceanic arc, suggesting tectonic transformation from oceanic expansion to initial intra-oceanic subduction of the Paleo-Tethys Ocean. The variety of magmatic compositions highlights the contributions of subduction-related pelagic sediments and fluids to their mantle wedge sources. The 184–179 Ma metamorphic age of amphibolites is con","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"679 ","pages":"Article 122677"},"PeriodicalIF":3.6,"publicationDate":"2025-02-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143429096","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Compositional evolution (Li, Be) in cordierite-group minerals from metamorphic and magmatic rocks of the Bory Granulite Massif, Moldanubian Zone, Czech Republic and its implications for origin of related granitic pegmatites","authors":"S. Hreus ,&nbsp;J. Kocáb ,&nbsp;M. Novák ,&nbsp;M. Vašinová Galiová ,&nbsp;P. Gadas","doi":"10.1016/j.chemgeo.2025.122668","DOIUrl":"10.1016/j.chemgeo.2025.122668","url":null,"abstract":"<div><div>Samples of cordierite-group minerals (CGM) from various rocks in the Bory Granulite Massif (BGM), Moldanubian Zone - granulite (1), leucosome to pegmatitic leucosome in migmatites (2), small zoned granitic pegmatites (2) and large, complexly zoned granitic pegmatites (11) were examined by the means of EPMA and LA-ICP-MS. CGM are morphologically and compositionally highly variable from subhedral grains, ∼0.5–5 cm in size, of cordierite (XMg₅₇) from granulite, subhedral grains, &lt; ∼5 cm, of cordierite-sekaninaite (XMg₅₆_–₄₄) from leucosome to pegmatitic leucosome, cordierite (XMg₆₀) from graphic unit and subhedral grains to large conic subhedral crystals, up to 0.7 m long, of sekaninaite (XMg₂₈_–₃) mainly from albite unit of complexly zoned pegmatites. Concentrations of Be and chiefly Li in CGM vary significantly - granulite (Be = 84–89 ppm, Li = 204–242 ppm), leucosome to pegmatitic leucosome (Be = 184–317 ppm, Li = 204–338 ppm), complexly zoned pegmatites (outer and blocky units - Be =150–200, Li = 577–904 ppm; albite unit - Be ≤51 ppm, Li = 572–3662 ppm; ≤0.79 wt% Li₂O). The following substitution mechanisms were revealed: homovalent R²⁺ substitutions - major Mg = Fe in all types of CGM, minor Mg + Fe = Mn in sekaninaite with low XMg, moderate to minor heterovalent substitution NaLi = □ R²⁺and insignificant substitution NaAl = □ Si in sekaninaite from complexly zoned pegmatites. Textural evolution from small bodies of leucosome to large complexly zoned pegmatites with Li-rich sekaninaite, and to Li-rich lepidolite pegmatites in BGM somewhat resembles evolution of simple anatectic pegmatites to albite-spodumene pegmatites from the Austroalpine Unit Pegmatite Province (Eastern European Alps); however, pegmatites from BGM with Li-bearing sekaninaite and lepidolite + petalite crystallized at lower P ∼ 2 kbar. Variations in concentrations of Be and Li in the individual paragenetic types of CGM and chiefly high Li and very low Be in sekaninaite manifest that pegmatitic melts underwent several steps of magmatic fractionation evident chiefly in complexly zoned pegmatites.</div></div>","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"680 ","pages":"Article 122668"},"PeriodicalIF":3.6,"publicationDate":"2025-02-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143550163","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Apatite and Zircon as key indicators for effusive-explosive transition in the Leningcou Volcano: Middle Triassic Volcanic activity in the East Kunlun Orogenic Belt","authors":"Gui-Zhi Huang ,&nbsp;Chang-Qian Ma ,&nbsp;Bin Liu ,&nbsp;Zhen-Hua Xue ,&nbsp;Huai Xiong ,&nbsp;Kai-Pei Lu ,&nbsp;Quan-Cheng Lian ,&nbsp;Ke Gao ,&nbsp;Meng-Yu Zhang ,&nbsp;Si-Yu Yang","doi":"10.1016/j.chemgeo.2025.122670","DOIUrl":"10.1016/j.chemgeo.2025.122670","url":null,"abstract":"<div><div>Volcanic eruptions play a critical role in the Earth's system by linking the lithosphere, atmosphere, hydrosphere, and biosphere. Determining the mode of volcanic eruptions is essential for assessing the potential hazards posed by volcanic activity to humans. Although significant progress has been made in monitoring active volcanoes and analyzing them with modern techniques, our understanding of the effusive-explosive transition in ancient volcanic eruptions remains limited. This study focuses on the Leningcou ancient volcano in the Triassic Chachaxiangka area of the East Kunlun Orogenic Belt on the northern Tibet Plateau. It aims to investigate the products around the ancient volcanic caldera through the study of accessory minerals and to identify potential factors influencing the effusive-explosive transition in volcanic eruptions.</div><div>Our research reveals that the Leningcou ancient volcano is composed of intermediate to acidic pyroclastic rocks and lava, with lava mainly exposed in the center of the ancient crater. Zircon U-Pb dating results indicate that this volcano was active during the Middle Triassic, approximately 242 Ma. Combined with whole-rock Sr-Nd isotopes and apatite Nd isotopic analysis, we suggest that the volcanic products originate from a similar crust-mantle mix source region and experienced varying degrees of crustal contamination. Using apatite hygrometers, we calculated the water content of the melts from the volcanic crater products, finding similar values with an average ranging between 3.3 and 3.7 wt% for both effusive and explosive volcanic rocks. The water content in the rhyolite melt of effusive eruptions reaches the highest value of 3.7 wt%. By analyzing redox-sensitive elements in apatite and zircon, we found that rhyolitic melts from explosive eruptions exhibit lower oxygen fugacity (ΔFMQ &lt;0), whereas the andesitic and rhyolitic melts of effusive eruptions show higher oxygen fugacity (ΔFMQ &gt;1).</div><div>Our research proposes a new model suggesting that a recharge event of mafic magma in the shallow crustal magma reservoir reactivated the crystal mush and triggered explosive eruptions. Higher melt water content introduced by new magma, along with a more open magma reservoir, are often key to factors in the transition from effusive to explosive eruptions.</div></div>","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"678 ","pages":"Article 122670"},"PeriodicalIF":3.6,"publicationDate":"2025-02-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143394088","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Chemical and isotopic evidence from the laterally asymmetric Bega Batholith for protracted Devonian fluid-induced infracrustal partial melting, eastern Lachlan Fold Belt, southeastern Australia","authors":"Ian S. Williams ,&nbsp;Malcolm T. McCulloch ,&nbsp;Simon D. Beams","doi":"10.1016/j.chemgeo.2025.122667","DOIUrl":"10.1016/j.chemgeo.2025.122667","url":null,"abstract":"&lt;div&gt;&lt;div&gt;The Devonian Bega Batholith in far southeastern Australia is composed of meridional strips of granites (supersuites) 10–20 km wide and up to 300 km long, each with distinctive chemical and isotopic compositions. The granites are predominantly granodiorites, with tonalites, some monzogranite and rare gabbro. West to east there are systematic changes in their chemical compositions, including increases in Na, P, Sr and Al, and decreases in Ca, Fe, Y and Rb, but relatively constant K, Mg and Ti. Similarly, there is also a systematic west to east trend towards more primitive isotopic compositions, with falling whole rock initial &lt;sup&gt;87&lt;/sup&gt;Sr/&lt;sup&gt;86&lt;/sup&gt;Sr (Sr&lt;sub&gt;i&lt;/sub&gt;), and rising whole rock ε&lt;sub&gt;Nd&lt;/sub&gt; and zircon ε&lt;sub&gt;Hf&lt;/sub&gt; values. The bulk of the granites were emplaced by a belt of magmatic activity up to 50 km wide that moved stepwise west to east over a period of about 25 Ma, followed about 15 Ma later by a separate episode of A-type magmatism. At any given time, particularly when the western part of the batholith was forming, granites belonging to as many as four different supersuites were being intruded simultaneously as coherent strips at widely separated locations. The granites within individual supersuites were not emplaced simultaneously, but over significant periods of time, in some cases ≥10 Ma. The main determinant of the chemical and isotopic composition of a pluton was its location, not its emplacement age, i.e. ‘where’ was more important than ‘when’. There are no systematic changes in granite age or composition along the length of the batholith. The western supersuites have relatively similar evolved isotopic compositions, consistent with a sediment contribution to the magmas. This accords with the relatively common inherited zircon cores in those granites, the age pattern of which matches that in the detrital zircon from the early Palaeozoic flysch into which the granites were emplaced. The eastern supersuites contain much less inherited zircon (although with the same age pattern) and show distinct trends in isotopic composition both between and within supersuites, becoming progressively more primitive eastwards and with decreasing age. In the abundance of elements such as Ca, Na, P, Sr, V and Sc, and in isotopic signatures (Sr&lt;sub&gt;i&lt;/sub&gt;, ε&lt;sub&gt;Nd&lt;/sub&gt; and ε&lt;sub&gt;Hf&lt;/sub&gt;), there is a sharp step in composition between the supersuites in the west and east. In contrast, throughout the batholith the isotopic compositions of feldspar Pb and whole rock and zircon O (δ&lt;sup&gt;18&lt;/sup&gt;O) are relatively uniform. These features are difficult to reconcile with infracrustal mixing between different mantle-derived magmas and significant amounts of a high level crustal component such as the Palaeozoic flysch. Those magmas would have to have different compositions in different linear strips at any given time, and to maintain those compositions as the belt of magmatism stepped eastwards. More likely the lower crust, from whic","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"678 ","pages":"Article 122667"},"PeriodicalIF":3.6,"publicationDate":"2025-02-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143386912","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}