Chemical Geology最新文献

{"title":"Allanite U-Th-Pb geochronology by laser ablation inductively coupled plasma mass spectrometry: Evaluation and development of reference materials with low common Pb","authors":"Tao Luo ,&nbsp;Mufei Li ,&nbsp;Xiaodong Deng ,&nbsp;Jiarun Tu ,&nbsp;Hongtao Shen ,&nbsp;Tom Kapitany ,&nbsp;Beining Hu ,&nbsp;Wen Zhang ,&nbsp;Zhaochu Hu","doi":"10.1016/j.chemgeo.2024.122562","DOIUrl":"10.1016/j.chemgeo.2024.122562","url":null,"abstract":"<div><div>Allanite, a member of the epidote supergroup, is widely distributed across various rock types. The U-Th-Pb geochronology of allanite can provide critical time constraints for investigating igneous rock formation, metamorphic events, and hydrothermal mineralization processes. Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) offers high spatial resolution for <em>in-situ</em> U-Th-Pb dating of allanite with the advantage of avoiding compositional zoning and inclusions. However, current allanite reference materials for LA-ICP-MS U-Th-Pb dating often contain high and variable common Pb contents, limiting their effectiveness as primary calibration standards. This study introduces two new allanite reference materials (AMK and ASP) with low common Pb content. Allanite AMK and ASP exhibit <em>f</em>_<em>206</em> values (the proportion of common ²⁰⁶Pb in the total measured ²⁰⁶Pb) below 0.8 % and 5.5 %, respectively. AMK contains 140 ± 41.9 μg g⁻¹ (1σ) of U and 306 ± 145 μg g⁻¹ (1σ) of Th, while ASP contains 261 ± 143 μg g⁻¹ (1σ) of U and 130 ± 102 μg g⁻¹ (1σ) of Th. ID-TIMS analysis yielded a weighted mean ²⁰⁷Pb/²⁰⁶Pb age of 1533.6 ± 1.9 Ma (2σ, MSWD = 5.1, <em>n</em> = 6) for AMK and a weighted mean ²⁰⁶Pb/²³⁸U age of 335.86 ± 0.52 Ma (2σ, MSWD = 5.9, <em>n</em> = 8) for ASP. To mitigate the impact of common Pb in primary reference materials, two ²⁰⁷Pb method-based calibrating procedures (VizualAge_UcomPbine software correction and a ‘two-step’ calibration strategy) were performed to the commonly used Tara allanite standard. While accurate allanite U<img>Pb ages can be obtained with both calibration strategies, analytical precision was reduced due to uncertainty propagated from the common Pb correction. Furthermore, a simple and robust allanite LA-ICP-MS U-Th-Pb dating method was established by calibrating against allanite AMK without prior common Pb correction. We propose allanite AMK as an effective primary reference material for LA-ICP-MS U-Th-Pb dating, while ASP serves as a suitable secondary reference material due to its very low common Pb content. Our results confirm no significant matrix effects during LA-ICP-MS analyses of allanites across a wide range of Th contents (from 0.03 to 21,900 μg g⁻¹) and FeO content variations (from 12.8 to 14.6 wt%).</div></div>","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"674 ","pages":"Article 122562"},"PeriodicalIF":3.6,"publicationDate":"2024-12-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142912324","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":"Pressure sensor based on the Raman shift of the 128-cm−1 band of quartz for pressure measurements in hydrothermal diamond-anvil cells","authors":"Jiankang Li ,&nbsp;I-Ming Chou ,&nbsp;Xian Wang ,&nbsp;Yongchao Liu ,&nbsp;Ziheng Han ,&nbsp;Jie Gao","doi":"10.1016/j.chemgeo.2024.122558","DOIUrl":"10.1016/j.chemgeo.2024.122558","url":null,"abstract":"<div><div>To interpret data collected from high-pressure (<em>P</em>)–temperature (<em>T</em>) experiments simulating geological processes, pressure information during these experiments is crucial. Traditionally, the Raman shifts of the quartz 464-cm⁻¹ band are commonly used as a hydrostatic-pressure calibrant in such experiments, particularly in those performed using hydrothermal diamond-anvil cells (HDACs). In this study, we conducted experiments using HDAC and a Raman spectrometer to investigate the sensitivity of the quartz 128-cm⁻¹ Raman band to changes in <em>P</em> and <em>T</em>. We found that the Raman shift of this band exhibits higher sensitivity to changes in <em>P</em> and <em>T</em> than the 464-cm⁻¹ band at <em>T</em>s above 200 °C. Changes in the Raman shift of the 128-cm⁻¹ band with <em>P</em>s and <em>T</em>s are 9–16 cm⁻¹/GPa and ~ (50–40) × 10⁻³ cm⁻¹/°C, respectively, at 200–700 °C and &lt; 1.0 GPa; the corresponding values for the 464-cm⁻¹ band are ~9 cm⁻¹/GPa and ~14 × 10⁻³ cm⁻¹/°C, respectively. The experimental data of <em>P</em>s, <em>T</em>s, and the Raman shifts of the quartz 128 cm⁻¹ band relative to that at 0.1 MPa and 23 °C (<em>∆ω</em>₁₂₈) were fitted into an equation to express their relation:</div><div><em>∆ω</em>₁₂₈ (cm⁻¹) = 1.20176 × 10⁻¹⁰ × <em>T</em>⁴–1.64508 × 10⁻⁷ × <em>T</em>³ + 2.0665 × 10⁻⁵ × <em>T</em>²–0.02134 × <em>T</em> + 0.00599 × <em>P</em> + 1.60394 × 10⁻⁵ × <em>T</em> × <em>P</em> + 0.48515,</div><div>where 23 ≤ <em>T</em> (°C) ≤ 700, <em>P</em> (MPa) &lt; 1000, and <em>R</em>² = 0.9986. Based on the scattered experimental data, the error of this equation is ±20 MPa. Based on this equation, the hydrostatic <em>P</em> can be calculated at a specific <em>T</em> when <em>∆ω</em>₁₂₈ is obtained in high <em>P–T</em> experiments using HDAC or other types of optical cells.</div></div>","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"674 ","pages":"Article 122558"},"PeriodicalIF":3.6,"publicationDate":"2024-12-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142858004","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":"Fe-dependent structural evolution of peralkaline soda aluminosilicate glasses: Iron speciation vs. glass transition","authors":"Michele Cassetta ,&nbsp;Emanuele De Bona ,&nbsp;Alessia Sambugaro ,&nbsp;Francesco Enrichi ,&nbsp;Nicola Daldosso ,&nbsp;Beatrice Giannetta ,&nbsp;Claudio Zaccone ,&nbsp;Mattia Biesuz ,&nbsp;Vincenzo M. Sglavo ,&nbsp;Renat Almeev ,&nbsp;Luca Nodari ,&nbsp;Daniele Giordano ,&nbsp;Gino Mariotto","doi":"10.1016/j.chemgeo.2024.122561","DOIUrl":"10.1016/j.chemgeo.2024.122561","url":null,"abstract":"<div><div>The incorporation of iron into peralkaline silicate glasses significantly impacts their structural and thermal properties. Here we investigate how addition of iron influences the network connectivity (short- and medium-range order) and glass transition temperature (<em>T</em>_<em>g</em>) with particular regard to the iron speciation and the Fe²⁺ and Fe³⁺ coordination state. We also found a sort of tipping point in iron concentration beyond which the short-range structures evolve linearly with density while the medium-range structure deviates from linearity. This behavior seems related to a re-enrichment of tetrahedral units triggered by iron self-compensation effect explaining the observed jump in <em>T</em>_<em>g</em>.</div></div>","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"674 ","pages":"Article 122561"},"PeriodicalIF":3.6,"publicationDate":"2024-12-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142858003","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":"Prediction of organic geochemical parameters from inorganic geochemical data in the Cretaceous-Danian Moreno Formation, San Joaquin Basin, California","authors":"Hunter C. Olson,&nbsp;Allegra Hosford Scheirer,&nbsp;Samantha R. Ritzer,&nbsp;Erik A. Sperling","doi":"10.1016/j.chemgeo.2024.122551","DOIUrl":"10.1016/j.chemgeo.2024.122551","url":null,"abstract":"<div><div>Accurately reconstructing original Total Organic Carbon (TOC) in thermally mature rocks is essential for the correct application of geochemical proxies and understanding organic carbon burial through time. To reconstruct original TOC using empirical methods, it is vital to have an accurate estimate of the original Hydrogen Index (HI). The two most common methods are estimating original HI using kerogen type or using average HI values from immature rocks elsewhere in the basin. This study tests the ability to use inorganic geochemical data to reconstruct original HI using the Upper Cretaceous-Paleogene Moreno Formation from the San Joaquin Basin, California, USA as a case study. The study utilized cores from the Moreno Formation that are thermally immature, thus preserving original HI values, and that span a range in initial HI. First, inorganic geochemical data were produced (elemental abundances and iron speciation) for samples previously analyzed for organic geochemistry. These data suggest that bottom water conditions during deposition of the Moreno Formation were ferruginous (anoxic and non-sulfidic), without development of sustained euxinia (anoxic and sulfidic). Next, a random forest machine learning analysis was implemented to analyze which inorganic geochemical variables best predict HI in the Moreno Formation. The most important proxies were those for detrital input (Ti, Th), marine export productivity (Cu, Ni), and redox proxies for suboxic conditions (Se, Cr, iron speciation). Finally, the random forest framework was used to predict HI values for three main study cores based on their inorganic geochemistry. These predictions were compared stratigraphically and statistically against the measured values and the kerogen type and average HI methods for reconstructing HI and show this new method has better predictive power than approaches based on single values. This indicates strong promise for using inorganic geochemistry, which is relatively immune to thermal maturation, to reconstruct organic geochemical parameters that are modified during burial and diagenetic process.</div></div>","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"674 ","pages":"Article 122551"},"PeriodicalIF":3.6,"publicationDate":"2024-12-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142858007","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":"Removal of arsenate from aqueous solutions by transformation of cerussite to mimetite","authors":"Ewa Stępień ,&nbsp;Maude Julia ,&nbsp;Daniel Buczko ,&nbsp;Martina Bottaro ,&nbsp;Andreas Kappler ,&nbsp;Maciej Manecki ,&nbsp;Christine V. Putnis","doi":"10.1016/j.chemgeo.2024.122531","DOIUrl":"10.1016/j.chemgeo.2024.122531","url":null,"abstract":"<div><div>Water pollution by arsenic is a growing concern due to its toxicity and health effects, prompting research on its immobilization. A novel method for removing arsenate ions from water using synthetic or natural cerussite powder (PbCO₃) is proposed. Laboratory experiments over three months at pH 2–8 show that in the presence of chloride ions, cerussite transforms into Pb(AsO₄)₃Cl (mimetite), and in their absence, into Pb(AsO₄)₃OH.</div><div>Arsenate is removed as lead carbonate dissolves and mimetite precipitates, achieving a removal efficiency of 57–99.9 %. Repeated treatments can enhance this efficiency to over 99 %, with the cerussite powder being reusable. Atomic Force Microscopy experiments show that mimetite formation is surface-controlled, and cerussite reacts with arsenate through a dissolution-precipitation mechanism, partially armouring the cerussite surface.</div><div>Repeating the experiments with cerussite in the presence of other cations (Mn, Fe, Ni, Cu, Zn, Cd, Al) or anions (CO₃²⁻, SO₄²⁻, PO₄³⁻, F⁻) showed that their presence has no significant effect on the progress and efficiency of the process. Only Al may slightly reduce the effectiveness. Reaction with solutions with an initial concentration of 5 mg As/L resulted in a 99.9 % reduction in As content. Similar observations were noted in experiments using natural arsenic-enriched waters (∼0.1 mg As/L), though the reaction proceeded more slowly, requiring additional time for arsenate removal to reach completion. These findings suggest that cerussite removes arsenate from water by gradually being replaced with mimetite crystals. While challenges remain in optimizing this method, it has the potential to become a novel technology for arsenic-contaminated water remediation.</div></div>","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"674 ","pages":"Article 122531"},"PeriodicalIF":3.6,"publicationDate":"2024-12-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143159408","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":"Volcanic-intrusive connections and crystal-melt segregation in the Dulan tilted crustal section: Insights from accessory mineral evolution","authors":"Bin Liu ,&nbsp;Luan Wu ,&nbsp;Chang-Qian Ma ,&nbsp;Meng-Yu Zhang ,&nbsp;Zhen-Hua Xue ,&nbsp;Yang Sun ,&nbsp;Shi-Ze Li","doi":"10.1016/j.chemgeo.2024.122517","DOIUrl":"10.1016/j.chemgeo.2024.122517","url":null,"abstract":"<div><div>The volcanic-intrusive connection is critical for understanding the formation of transcrustal magma systems and the mechanisms driving magma eruption. Yet, the genetic links between abyssal intrusive rocks and acidic volcanic rocks remain poorly understood. Here, we present new data from the Dulan volcanic-intrusive complex, a tilted section of the East Kunlun orogenic belt, integrating zircon U<img>Pb dating, trace elements, apatite and zircon Hf isotope geochemistry, and whole-rock geochemistry to investigate volcanic-intrusive connections and track crystal-melt segregation processes. The Dulan complex comprises rhyolite, granite porphyry, and granodiorite, all showing consistent zircon U<img>Pb ages, rare earth element (REE) patterns, and εHf(t) values, suggesting a shared magma source. Glomerocrysts of plagioclase, alkali feldspar, and hornblende, along with antecrystic zircon and apatite, imply a cumulate affinity in granodiorite and granite porphyry. Compositional variations in whole-rock and accessory minerals indicate that plagioclase, apatite, and zircon fractionation significantly influenced magma evolution. We propose a two-stage crystal segregation process in a ∼ 2 Myr-long magma reservoir system. In the early stage, at ∼33 km depth, aqueous fluid influx initiated crystal-melt segregation, forming the Dulan granodiorite from residual mush. In the later stage, mafic melt and fluid injections caused crystal-melt segregation in a shallower reservoir at ∼12 km depth, with high-silica magma producing rhyolite, while residual mush consolidated into granite porphyry. Our findings suggest that volcanic-intrusive connections are more complex than mere compositional equivalence or complementarity, requiring multidimensional analysis through accessory minerals and whole-rock geochemistry.</div></div>","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"672 ","pages":"Article 122517"},"PeriodicalIF":3.6,"publicationDate":"2024-11-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142747434","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":"Kinetic MgFe isotope fractionation in natural basalts during melt-peridotite interaction","authors":"Gang Zeng ,&nbsp;Xiao-Jun Wang ,&nbsp;Xiao-Yu Zhang ,&nbsp;Yuan Zhong ,&nbsp;Jin-Hua Shi ,&nbsp;Xun Yu ,&nbsp;Lie-Wen Xie ,&nbsp;Li-Hui Chen","doi":"10.1016/j.chemgeo.2024.122514","DOIUrl":"10.1016/j.chemgeo.2024.122514","url":null,"abstract":"<div><div>Although Mg and Fe isotopes are frequently used to trace the source heterogeneity of basalts (e.g., recycled carbonated materials or eclogite in the mantle), they can also be fractionated by geological processes during magma migration from the source to the surface. Recently, the light Mg and heavy Fe isotopic compositions observed in high-Ti lunar basalts have been attributed to the kinetic fractionation that occurs during interaction between the melt and ambient harzburgite cumulates. Due to the thick lithospheric mantle, the melt-peridotite interaction is frequently invoked to explain the chemical variations observed in continental basalts on Earth. However, the isotope fractionation behavior of Mg<img>Fe isotopes during this process has not been well addressed. Here we present Mg<img>Fe isotopic compositions of alkaline basalts from the Nanjing basaltic field in eastern China, alongside the peridotite xenoliths hosted within these basalts, in order to assess the potential isotopic fractionation under this specific condition. Previous petrographic evidence suggests that these peridotite xenoliths had undergone significant interaction with the hosting basalts. Peridotite xenoliths exhibit homogeneous, normal-mantle-like δ²⁶Mg (from −0.243 ‰ to −0.281 ‰), but they have highly variable, low δ⁵⁷Fe (from 0.156 ‰ to −0.057 ‰), indicating that melting reaction has not altered the Mg isotopic compositions but has modified the Fe isotopic compositions of these xenoliths. The hosting basaltic rocks exhibit heavy Fe isotopic compositions (δ⁵⁷Fe = 0.218 ‰–0.366 ‰) and extremely light Mg isotopic compositions (δ²⁶Mg = −0.641 ‰−−0.389 ‰). The δ²⁶Mg values of these xenolith-rich basalts are well correlated with their δ⁵⁷Fe values, Hf isotopes, and certain elemental ratios (e.g., Lu/Hf, La/Sm, Ca/Al, and Na/Ti). These correlations can be explained by mixing between the host basaltic magma and a type of melt derived from peridotite xenolith. These xenolith-derived melts have significantly lighter Mg and heavier Fe isotopic compositions than the normal mantle. Given their extremely low Mg/Fe ratios resulting from near-solidus melting, they are not in Mg or Fe equilibrium with the residual solid. Consequently, kinetic Mg<img>Fe isotope fractionation is inferred to occur during the interaction between the melt and peridotite. Therefore, our results serve as a representative sample for characterizing Mg<img>Fe isotope fractionation via chemical diffusion in natural systems, and they highlight the significant influence of melt-peridotite interaction on the heterogeneity of Mg<img>Fe isotopes in those xenolith-rich basalts (characterized by low melt/olivine ratios).</div></div>","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"672 ","pages":"Article 122514"},"PeriodicalIF":3.6,"publicationDate":"2024-11-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142748099","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":"Apatite as an indicator of tectono-magmatic evolution of silica-undersaturated to silica-oversaturated rocks on the NW Indian Plate margin","authors":"Musa Khan ,&nbsp;Huan Li ,&nbsp;Thomas J. Algeo ,&nbsp;Asad Khan ,&nbsp;Adnan Khan ,&nbsp;Yiming Xie","doi":"10.1016/j.chemgeo.2024.122516","DOIUrl":"10.1016/j.chemgeo.2024.122516","url":null,"abstract":"<div><div>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/Sr⁸⁶_i = 0.7035 to 0.7057 and εNd(t) = +0.3 to +6.0 for the silica-undersaturated group, ⁸⁷Sr/Sr⁸⁶_i = 0.7044 to 0.7205 and εNd(t) = +1.8 to +3.8 for the silica-saturated group, and ⁸⁷Sr/Sr⁸⁶_i = 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. T_DM2 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.</div></div>","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"672 ","pages":"Article 122516"},"PeriodicalIF":3.6,"publicationDate":"2024-11-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142747433","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":"Secular evolution of continental crust of the North China Craton constrained by U-Pb and Lu-Hf-O/Sm-Nd isotopic analyses of detrital zircon and monazite in river sediments","authors":"Guangyan Zhou ,&nbsp;D. Graham Pearson ,&nbsp;Yan Luo ,&nbsp;Long Li ,&nbsp;Christopher M. Fisher ,&nbsp;Rui Li ,&nbsp;Wei Wang ,&nbsp;Yuanbao Wu","doi":"10.1016/j.chemgeo.2024.122515","DOIUrl":"10.1016/j.chemgeo.2024.122515","url":null,"abstract":"<div><div>Robust detrital minerals from large rivers that sample large-scale continental areas represent important archives of continental crust evolution though time. Compared to the single proxy approach, integrating multiple isotope systems of multiple detrital minerals helps to gain a more comprehensive understanding of crustal growth and evolution. This novel method has so far only been applied to single-sample studies of large rivers and has not yet been utilized for reconstructing continental growth on a cratonic scale. Here, we analyze the U-Pb age, trace element and Lu-Hf-O/Sm-Nd isotopic systematics of detrital zircon (DZ) and monazite (DMnz) from multiple river sediments, with their corresponding drainage basins covering most of the North China Craton (NCC). The results show that the Precambrian DZ have U-Pb age clusters coincident with known episodes of felsic magmatism within the NCC basement. These zircons have variable δ¹⁸O values reflecting extensive incorporation of supracrustal materials into their parent magmas. The DZ sourced from Phanerozoic orogens show mantle-like to high δ¹⁸O values and highly negative to positive ε_Hf(t) values, reflecting the accretion of juvenile crust as well as reworking of ancient continental material. In contrast, DMnz are mostly sourced from high-grade metamorphic rocks and peraluminous granites formed in orogens. The Sm-Nd isotopic compositions of the Paleoproterozoic DMnz reflect a contribution from widespread granulite-amphibolite facies metamorphic rocks of lower crustal origin, recording a major juvenile crust extraction event at ca. 2.5–2.4 Ga that is absent in the DZ record. The integrated DZ-Hf and DMnz-Nd datasets indicate ca. 65–70 % of the existing continental crust was separated from the mantle before ca. 2.4–2.3 Ga with a sharp decrease in growth rate since then, likely linked to the preservation potential of continental masses before and after cratonization of the NCC.</div></div>","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"672 ","pages":"Article 122515"},"PeriodicalIF":3.6,"publicationDate":"2024-11-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142722510","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":"Carbon translocation within land snails affects the carbon isotopic fractionation","authors":"Chenglong Li ,&nbsp;Haolin Tan ,&nbsp;Min Wu ,&nbsp;Rui Bao ,&nbsp;Yijiang Xu ,&nbsp;Xuefen Sheng","doi":"10.1016/j.chemgeo.2024.122511","DOIUrl":"10.1016/j.chemgeo.2024.122511","url":null,"abstract":"<div><div>Stable carbon isotope composition (δ¹³C) of land snail materials is widely used as a proxy for reconstructing past vegetation and environmental changes. Interpretation δ¹³C data is challenging due to the complexities of snail physiology. This study cultured <em>Lissachatina fulica</em> (Bowdich, 1822) snails to investigate δ¹³C of their soft tissues and excrement under various plant types and dietary carbonate content. Our results show that snails primarily assimilate organic matter (OM), with limited use of dietary carbonates. δ¹³C of organic matter in excrement correlates positively with that in the diet, but exhibits deviations due to variable carbon isotopic fractionation during assimilation. Tissue δ¹³C (δ¹³C_tissue) is positively related to the δ¹³C of OM (δ¹³C_OM) in the diet, varying by turnover rates, with faster turnover rate, such as the digestive gland, exhibiting more negative δ¹³C_tissue values. Moreover, carbon isotopic fractionation between tissues and diet (Δ¹³C_tissue-OM) differs based on plant type. Snails fed with C₃ plants show positive Δ¹³C_tissue-OM values, whereas those fed with C₄ plants exhibit negative values. These Δ¹³C_tissue-OM values are far from equilibrium (Δ¹³C_tissue-OM = 0) with conditions of rapid snail growth. Our findings indicate that the snails fed with C₃ and C₄ plants result in distinct carbon isotopic fractionation, leading to the deviation in δ¹³C between plants and land snail materials (e.g., excrement, tissues, shells and shell-bound organic matter). A comprehensive model of carbon metabolism and isotopic fractionation in snails is proposed including the assimilation process from diet to soft tissues and excretion. This study highlights the importance of physiological factors such as growth rates and turnover rates when interpreting δ¹³C of land snail materials for paleoenvironmental reconstructions.</div></div>","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"672 ","pages":"Article 122511"},"PeriodicalIF":3.6,"publicationDate":"2024-11-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142722511","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}