Chemical Geology最新文献

{"title":"Relationships between salinity and hydrogen isotopes of n-alkanes in aquatic plants across Chinese natural lakes","authors":"Hu Liu ,&nbsp;Huanye Wang ,&nbsp;Zheng Wang ,&nbsp;Zhonghui Liu ,&nbsp;Yunning Cao ,&nbsp;Weiguo Liu","doi":"10.1016/j.chemgeo.2024.122570","DOIUrl":"10.1016/j.chemgeo.2024.122570","url":null,"abstract":"<div><div>Hydrogen isotope compositions (δD) of lipids are widely used in hydrological research, yet there have been limited investigations into the relationships between salinity and δD values of aquatic plants in natural lakes, which hinders the broader application of δD compositions as indicators of paleosalinity reconstructions. In this study, we examined δD compositions of <em>n</em>-alkanes in aquatic plants and lake water from 58 lakes (containing 18 brackish/saline lakes) across diverse regions of China (including the Tibetan Plateau, Inner Mongolia Plateau, Chinese Loess Plateau, Tarim Basin, and Yangtze Plain). Subsequently, we examined the correlations between salinity and <em>n</em>-alkane δD values in aquatic plants. Our findings indicate that δD values of <em>n</em>-alkanes from aquatic plants record variations in lake water δD (<em>R</em>² = 0.53, <em>p</em> &lt; 0.01). Furthermore, δD values of lake water in brackish/saline lakes exhibit a positive correlation with salinity (<em>R</em>² = 0.74, <em>p</em> &lt; 0.01). Thus, a positive correlation (<em>R</em>² = 0.68, <em>p</em> &lt; 0.01) is observed between δD values of <em>n</em>-alkanes from aquatic plants and lake salinity, whose changes both co-vary with lake water δD variations. Therefore, <em>n</em>-alkane δD values of aquatic plants can serve as indirect indicators of salinity for reconstructing paleosalinity in brackish/saline lakes. It is important to note that paleosalinity reconstruction in lakes using <em>n</em>-alkane δD values is generally more effective when lake salinity experiences large variations, whereas caution should be exercised when lake salinity changes are more subtle.</div></div>","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"674 ","pages":"Article 122570"},"PeriodicalIF":3.6,"publicationDate":"2024-12-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142887287","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 heterogeneity in 91500, GJ-1/89 and TEMORA-2 zircon reference materials","authors":"John T. Caulfield ,&nbsp;Charlotte M. Allen ,&nbsp;Teresa Ubide ,&nbsp;Ai Nguyen ,&nbsp;Henrietta E. Cathey","doi":"10.1016/j.chemgeo.2024.122580","DOIUrl":"10.1016/j.chemgeo.2024.122580","url":null,"abstract":"<div><div>Zircon is the most analysed mineral using laser ablation ICP-MS, partly because its trace element systematics can be used to explore a broad range of petrogenetic processes. However, internal chemical zoning, a common feature in zircon, can result in sampling of chemically distinct crystal domains. This affects not only unknown zircons, but also zircon secondary reference materials used to assess data accuracy and precision. To better resolve the extent of geochemical heterogeneity in zircon, we present long-term laser ablation Q-ICP-MS trace element data (<em>n</em> = 6342) for three widely distributed zircon reference materials: 91500, GJ-1/89 and TEMORA-2. Zircons 91500 and GJ-1/89 have volumetrically minor domains that appear anomalous in hyperspectral cathodoluminescence (CL) and represent large scale chemical features unrelated to minor banding documented in these reference materials. The extent of compositional variability is significantly greater in 91500, particularly for the REE + Y (91500 bias between zones = 51–63 %; GJ1/89 &lt; 5 %, except Ce). Uranium and Th show very similar data trends with 2-3× variation. In contrast, TEMORA-2 is strongly sector-zoned, showing bimodal distributions defined by prism sectors growing perpendicular to the c-axis and pyramid sectors growing along the c-axis. Prisms are enriched in REE + Y from 330 % to 85 % (Pr–Lu) over pyramids. Uranium, Th and Pb show prism sector enrichments of 71 %, 160 % and 75 %, respectively. Cerium, together with the HFSE and P appear to be sector independent. The chemical heterogeneity observed in TEMORA-2 zircon highlights the universal need to obtain texturally constrained analyses in sector-zoned zircons. Our data indicate that the GJ-1 crystals represent the best available zircon trace element reference material, and that 91500 is a good alternative provided minor anomalous domains are tracked.</div></div>","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"674 ","pages":"Article 122580"},"PeriodicalIF":3.6,"publicationDate":"2024-12-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142912320","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":"Salinity-redox covariation in Mississippian Bowland Shale (Craven Basin, UK) controlled by eustasy and climate","authors":"Yu Jiao ,&nbsp;Joseph F. Emmings ,&nbsp;Lian Zhou ,&nbsp;Thomas J. Algeo ,&nbsp;Lanping Feng ,&nbsp;Tao He ,&nbsp;Jinhua Liu ,&nbsp;Daqian Zhang ,&nbsp;Jianping Wang","doi":"10.1016/j.chemgeo.2024.122572","DOIUrl":"10.1016/j.chemgeo.2024.122572","url":null,"abstract":"<div><div>Changes in watermass properties can be monitored in real time in modern depositional systems, but reconstruction in deep-time systems is difficult. Here, we analyze long-term changes in salinity (B/Ga, Sr/Ba, and S/TOC) and redox conditions (Fe_HR/Fe_T, Fe_py/Fe_HR, and C_org/P) in the upper unit of the Mississippian Bowland Shale Formation, Craven Basin, UK. Variations in paleosalinity and redox in the Upper Bowland Shale were tightly coupled to fourth-order glacio-eustatic cyclicity. At basinal sites (borehole MHD and outcrop HC), transgressive to highstand packages (‘marine bands’) were associated with weakly hypersaline to normal marine, euxinic bottom-water conditions. In contrast, falling-stage and lowstand packages were deposited under normal-marine salinity and fluctuating euxinic to ferruginous anoxic conditions punctuated by (sub)oxic events. HC, located within a bathymetric low, exhibits significantly higher C_org/P (∼100) than MHD (&lt;50), located on an intrabasinal high, due to the more limited influence of oxygen-bearing hyperpycnal flows in the deep basin. A sharp shift to brackish conditions near the top of the HC section reflects the basinward progradation of the Pendle Paleodelta in response to long-term eustatic fall. In the relatively more proximal (landward) and stratigraphically younger COM borehole, the pattern of salinity-redox covariation in response to sea-level cyclicity is different: highstands were associated with normal-marine salinity and euxinic conditions, whereas lowstands exhibit shifts toward brackish, oxic bottom-water conditions, reflecting shoaling of this site into the ocean-surface layer and influence from the nearby Pendle deltaic system. The ultimate driver of late Mississippian sea-level fluctuations was growth and decay of Gondwanan icesheets during an early phase of the Late Paleozoic Ice Age, with interglacial stages potentially being marked by a shift toward stronger evaporation within the climatically sensitive zone occupied by the Craven Basin (∼10–15°S paleolatitude). Our findings provide new insights into the sea-level-redox-salinity dynamics of marginal-marine basins during a major ice age.</div></div>","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"674 ","pages":"Article 122572"},"PeriodicalIF":3.6,"publicationDate":"2024-12-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142912321","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":"From formation to maturation: Trace element systematics of sulfide chimneys from the Niaochao vent field (East Pacific Rise)","authors":"Xingwei Meng ,&nbsp;Xiaohu Li ,&nbsp;Astrid Holzheid ,&nbsp;Basem Zoheir ,&nbsp;Ling Chen ,&nbsp;Matthias Frische ,&nbsp;Smruti Sourav Rout ,&nbsp;Wei Li ,&nbsp;Fengyou Chu ,&nbsp;Xianglong Jin","doi":"10.1016/j.chemgeo.2024.122584","DOIUrl":"10.1016/j.chemgeo.2024.122584","url":null,"abstract":"<div><div>The identification of the maturity stages of collapsed sulfide chimneys remains challenging due to alterations in their original structural and mineralogical characteristics. The trace element composition of sulfides can provide valuable information about the mineralization processes in submarine hydrothermal systems. However, the link between trace element variations and the maturity stages of sulfide chimneys remains unclear. The present study employs in-situ trace element analysis and elemental mapping of sulfides in three maturity grades of sulfide chimneys at the Niaochao vent field (East Pacific Rise, 1–2°S) to elucidate the relationship between trace element variations, mineralogical changes, and fluid evolution.</div><div>The investigated sulfide chimneys are classified into seven mineralogical assemblages across five evolutionary stages, typically transitioning from sphalerite-pyrite-rich to chalcopyrite-pyrite-(high-Fe sphalerite)-rich and eventually reverting to pyrite-sphalerite-rich layers as chimneys mature. Initially, trace elements such as Cu, Zn, Pb, and Ag appear as micro- or nano-inclusions in anhedral pyrites, likely formed under rapid, disequilibrium, low-temperature conditions. Over time, these elements, along with Co, Ni, Se, and As, were incorporated into the lattices of euhedral and massive pyrites under high-temperature conditions. As chimneys grew inward, trace element enrichment transitioned from seawater-derived elements (e.g., Mg, V, U) and low-temperature-responsive elements (e.g., Zn, Pb, As, Tl) to high-temperature-responsive elements (e.g., Cu, Se, Co). This progression is marked by increasing concentrations of Co, As, Sb, Mo, and rising Co/Ni ratios in pyrites from chimney rims to cores, reflecting chimney maturity. In higher maturity grades of chimneys, elevated levels of Sb, Mg, and Se in anhedral pyrites, Se, Zn, and Cd in euhedral pyrites, and Se in chalcopyrite indicate a more advanced stage of hydrothermal evolution. These compositional trends suggest that trace elements can serve as indicators of chimney and hydrothermal system maturity, capturing the evolution of hydrothermal activity from initiation to maturation.</div></div>","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"674 ","pages":"Article 122584"},"PeriodicalIF":3.6,"publicationDate":"2024-12-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142887288","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":"Fluid evolution and halogen fractionation in orogenic belts: A comparative fluid inclusion appraisal in the Eastern Pyrenees","authors":"Eloi González-Esvertit ,&nbsp;Tobias Fusswinkel ,&nbsp;Àngels Canals ,&nbsp;Josep Maria Casas ,&nbsp;Joyce Neilson ,&nbsp;Thomas Wagner ,&nbsp;Enrique Gomez-Rivas","doi":"10.1016/j.chemgeo.2024.122578","DOIUrl":"10.1016/j.chemgeo.2024.122578","url":null,"abstract":"&lt;div&gt;&lt;div&gt;The physicochemical signatures of fluid-rock interaction, recorded in fluid inclusions, represent fundamental proxies for understanding the interplay between rock deformation, fluid migration, and ore deposit formation in the Earth's crust. Although fluid-rock interaction can take place simultaneously or sequentially both in the basement and the cover of collisional orogens, these two scenarios are generally investigated separately, thus precluding an integrated understanding of the processes involved. Here, we present a comprehensive study of the fluid evolution in the basement and cover rocks of the Pyrenees (SW Europe) by means of Geographic Information System (GIS)-assisted petrography, microthermometry, Electron Backscatter Diffraction (EBSD), Raman micro-spectroscopy, and Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS) microanalysis of individual fluid inclusions. The investigated fluids are sampled from giant quartz veins, which are tens of meters wide and up to several kilometres long. Two-phase aqueous fluid inclusions hosted in the basement (Canigó and Cap de Creus massifs) and cover rocks (Roc de Frausa massif) show significant variations regarding their homogenization temperature (T&lt;sub&gt;h&lt;/sub&gt;), salinity, and chemical composition. Basement-hosted H&lt;sub&gt;2&lt;/sub&gt;O-NaCl-CaCl&lt;sub&gt;2&lt;/sub&gt; fluids have T&lt;sub&gt;h&lt;/sub&gt; and salinity ranging between 190 and 220 °C and 12–16 wt% equivalent (eq.) NaCl in the Canigó massif, and between 190 and 260 °C and 16–20 wt% eq. NaCl in the Cap de Creus massif. Conversely, T&lt;sub&gt;h&lt;/sub&gt; of 180–240 °C and salinity of 4–7 wt% eq. NaCl were obtained for H&lt;sub&gt;2&lt;/sub&gt;O-NaCl cover rock-hosted fluids in the Roc de Frausa massif. Fluid salinity, cation concentrations, and halogen ratios suggest that basement-hosted fluids represent residual basinal brines that originated from seawater which underwent variable degrees of evaporation and organic matter interaction. In contrast, cover rock-hosted fluids represent seawater-like precursor fluids that record strong organic matter interaction without significant evaporative halogen fractionation. The data suggest that neither basement- nor cover-hosted fluids were released at depth from magmatic or metamorphic fluids, which agrees with geological constraints of the investigated areas. However, fluids from both basement and cover rocks infiltrated deep into the subsurface, as revealed by their variable metal and halogen concentration suggesting compositionally stratified fluid compositions at depth. Our data and conclusions differ from fluid inclusion studies reported for other giant quartz vein systems worldwide, suggesting that different fluid origins and evolution histories may drive the formation of these large quartz accumulations. Moreover, the large variations of the Br/Cl, I/Cl, and Br/I ratios show that halogen ratios should be used with caution: they are excellent tracers of the fluid evolution history, but may not provide a straig","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"674 ","pages":"Article 122578"},"PeriodicalIF":3.6,"publicationDate":"2024-12-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142912322","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":"Spatial distribution and molecular evidence of CO2 dark production from lake sediments during anoxic-oxic transitions across a watershed","authors":"Wen Guo ,&nbsp;Peng Liao ,&nbsp;Junjian Wang ,&nbsp;Peng Zhang ,&nbsp;Yuanhang Lei ,&nbsp;Jingfu Wang ,&nbsp;Jingan Chen","doi":"10.1016/j.chemgeo.2024.122577","DOIUrl":"10.1016/j.chemgeo.2024.122577","url":null,"abstract":"<div><div>Anoxic-oxic interfaces that occur in lake sediments serve as hotspots for CO₂ production. Traditionally, in lake sediments, the oxidative production of CO₂ has been primarily attributed to microbial mechanisms. Although abiotic formation of hydroxyl radicals (<img>OH) can oxidize organic carbon to CO₂ in soils, the specific role of <img>OH in CO₂ production and its spatial distribution remains unexplored in lake sediments. Particularly, the underlying mechanism of CO₂ production from lake sediments during the anoxic-oxic transition is lacking. Here, by integrating field measurements, laboratory incubations, and advanced characterizations, we provide compelling evidence that the coupled iron‑carbon cycles drive the extensive CO₂ production during oxygenation. Surface-adsorbed Fe(II) and structural Fe(II) in sediments are the major drivers of CO₂ production. CO₂ production exhibited significant spatial variabilities across the watershed, with shallow sediments displaying higher CO₂ production due to the abundant Fe(II). The spatial distribution of CO₂ closely mirrors that of <img>OH generated from Fe(II) oxygenation, with <img>OH accounting for a CO₂ flux of 95.61 g C m⁻² d⁻¹. Spectroscopic and microscopic characterizations reveal that <img>OH-mediated carboxyl addition initiates the ring opening of aromatic structures, leading to their depolymerization, demethoxylation, and fragmentation, ultimately producing condensed aromatic compounds and CO₂. Besides, <img>OH facilitates the oxidative decomposition of larger macromolecules to bioavailable low-molecular-weight acids. Altogether, we propose that the Fe(II)-driven <img>OH formation represents a previously unrecognized and prevalent abiotic mechanism of CO₂ production in lake sediments. This new knowledge is valuable for improving the ability to predict CO₂ emissions at hotpots.</div></div>","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"674 ","pages":"Article 122577"},"PeriodicalIF":3.6,"publicationDate":"2024-12-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142887289","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":"Textural and chemical variation of apatite from Ziyang-Zhuxi alkaline rocks (Central China): Implications for REE migration during magmatic and hydrothermal processes","authors":"Lisha Yang ,&nbsp;Lianxun Wang ,&nbsp;Chao Zhang ,&nbsp;Yuxiang Zhu ,&nbsp;Thomas Ulrich ,&nbsp;Changqian Ma ,&nbsp;Xin Deng","doi":"10.1016/j.chemgeo.2024.122581","DOIUrl":"10.1016/j.chemgeo.2024.122581","url":null,"abstract":"<div><div>Apatite is a ubiquitous rare earth elements (REE)-rich accessory mineral of great significance in revealing the behavior of REE in alkaline rocks. This study investigates the textural, elemental, and Rb<img>Sr isotopic compositions of apatite from a series of alkaline volcanic-intrusive rocks in the Ziyang-Zhuxi region of the South Qinling Belt (China), including gabbroic rocks (pyroxenite, basalt, gabbro, and diabase), dioritic rocks (pyroxene diorite and amphibole monzonite), and syenitic rocks (biotite syenite and trachyte). Two main types of apatite, magmatic and metasomatic, have been identified in the studied rocks. The magmatic apatite (Ap-1) is represented by euhedral hexagonal crystals and commonly occurs as inclusions in pyroxene, amphibole and feldspar. The metasomatic apatite (Ap-2) generally occurs in syenitic rocks, exhibiting obvious metasomatic textures and is commonly associated with secondary monazite. In Ap-1, the LILE (e.g., Sr, Ba) and compatible elements (e.g., V, Sc) decrease from alkaline mafic rocks to felsic rocks, indicating that fractionation of feldspars and mafic minerals such as pyroxene and amphibole dominated the magma evolution process. The REE contents (ΣREE from 4060 to 37,100 ppm), however, increase accordingly, suggesting that magma evolution promotes REE enrichment in the residual melt. On the other hand, the metasomatic apatite (Ap-2) displays obvious lower ΣREE contents (mean of 10,480 ppm) than their magmatic apatite (Ap-1) counterparts (mean of 30,890 ppm), indicating a leaching process of REE from primary apatite during hydrothermal fluid metasomatism. The leached REE from apatite (∼30 %) either precipitated into monazite as an in-situ replacement or were remobilized and migrated locally. The higher Sr contents and ⁸⁷Sr/⁸⁶Sr ratios of Ap-2 than those of Ap-1 (0.7090–0.7107 vs 0.7033–0.7046) indicate an external contribution of Sr from the late hydrothermal fluids. Therefore, we propose that the REE enrichment mechanism of the studied alkaline rocks can be attributed to two major processes: magma fractional crystallization followed by hydrothermal metasomatism.</div></div>","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"674 ","pages":"Article 122581"},"PeriodicalIF":3.6,"publicationDate":"2024-12-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142912328","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":"Strontium isotope and trace element compositions of olivine-hosted melt inclusions from the Song Da ultramafic volcanic suite, northern Vietnam: Implications for chemical heterogeneity in mantle plumes","authors":"Charbel Kazzy ,&nbsp;Alexander V. Sobolev ,&nbsp;Adrien Vezinet ,&nbsp;Valentina G. Batanova ,&nbsp;Igor S. Puchtel ,&nbsp;Evgeny V. Asafov ,&nbsp;Eero Hanski ,&nbsp;Andrey E. Izokh ,&nbsp;Leonid V. Danyushevsky ,&nbsp;Vũ Hoàng Ly ,&nbsp;Can Pham-Ngoc ,&nbsp;Tran Tuan Anh","doi":"10.1016/j.chemgeo.2024.122564","DOIUrl":"10.1016/j.chemgeo.2024.122564","url":null,"abstract":"&lt;div&gt;&lt;div&gt;Ultramafic magmas are the ideal tracеrs of mantle composition, as they are derived from high degrees of partial melting and their compositions approach that of mantle peridotite. The Permian Song Da ultramafic volcanic rocks in northern Vietnam represent a rare example of well-preserved Paleozoic picrites of the Emeishan Large Igneous Province (ELIP), with the most Mg-rich olivine phenocrysts of up to Fo&lt;sub&gt;93.5&lt;/sub&gt;. As such, they are invaluable for constraining temperature, pressure, and composition of the ELIP mantle source. Here, we report the results of a study of olivine-hosted melt inclusions from ultramafic lavas of both low-Ti and high-Ti types in the Song-Da zone of the ELIP, providing new information on the concentrations of mobile trace elements, volatile components, and Sr isotope compositions of parental melts. Our data suggest a significant difference between the mantle source compositions of low-Ti and high-Ti primary melts of the Song Da zone. The latter melt likely originally contained 2.7 ± 1.2 wt% CO&lt;sub&gt;2&lt;/sub&gt; and 0.6 ± 0.1 wt% H&lt;sub&gt;2&lt;/sub&gt;O, but lost most of its volatile inventory during degassing. Its enrichment in trace elements is attributed to a low degree of partial melting (less than 9 %) of a PREMA-type peridotitic source, as evidenced by the bulk rocks Nd and melt inclusions Sr isotopic data, contaminated by metasomatic fluids or recycled components bringing Pb, Sr, and Na. The low-Ti komatiite-type Song Da melts contain an excess of H&lt;sub&gt;2&lt;/sub&gt;O (H&lt;sub&gt;2&lt;/sub&gt;O/Ce up to 5500), similarly to some Archean komatiites, show a decoupling of Nd and Sr isotopes, and reveal mixing of at least two unusual components: (1) one with low initial &lt;sup&gt;87&lt;/sup&gt;Sr/&lt;sup&gt;86&lt;/sup&gt;Sr (down to 0.7040), low Nb/U and Ce/Pb ratios and relatively enriched in La, Th, U, Pb, and Sr, and (2) the other with high initial &lt;sup&gt;87&lt;/sup&gt;Sr/&lt;sup&gt;86&lt;/sup&gt;Sr (up to 0.7080), high Nb/U and Ce/Pb ratios, and strongly depleted in highly incompatible lithophile elements such as Ba, Rb, Nb, K, U, Th, La, and Sr. We suggest that component (1) reflects contamination with lower continental crust or other subduction-related constituents in the mantle source, while component (2) represents partial melt derived from dehydrated seawater-altered recycled harzburgite that was part of a subducted oceanic slab 300 to 500 Ma in age. The latter component can be recognized only in the melts that are exceptionally depleted in highly incompatible elements. The data from this study and &lt;span&gt;&lt;span&gt;Kazzy et al. (2024)&lt;/span&gt;&lt;/span&gt; suggest that the ELIP was produced by a mantle plume with a maximum potential temperature (T&lt;sub&gt;p&lt;/sub&gt;) of ∼1600 °C at ∼260 Ma. Because of its high temperature, this plume passed through the hydrated mantle transition zone (MTZ) in a partially molten state, which allowed it to entrain in its hottest part H&lt;sub&gt;2&lt;/sub&gt;O and components of the subducted 300–500 Ma Paleo-Tethyan oceanic plate stagnated in the MTZ for ∼200 Ma. An alter","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"674 ","pages":"Article 122564"},"PeriodicalIF":3.6,"publicationDate":"2024-12-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142887305","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":"Observed dissolved gallium in the tropical and subtropical waters in the Western Pacific Ocean","authors":"Zheng Bo Liu ,&nbsp;Jing Zhang ,&nbsp;Shuo Jiang ,&nbsp;Han Su ,&nbsp;Jingling Ren ,&nbsp;Hang Zhang ,&nbsp;Shijian Hu","doi":"10.1016/j.chemgeo.2024.122573","DOIUrl":"10.1016/j.chemgeo.2024.122573","url":null,"abstract":"<div><div>The concentration data of Gallium (Ga) observed in the Western Pacific section spanning from 2°S to 20°N along 142°E are reported for the first time. The spatial distribution of Ga in the surface, subsurface, intermediate, and deep layers is presented, and its influencing factors are discussed. We find that terrestrial input from Papua New Guinea constitutes a significant source of surface Ga in this region, while the distribution of Ga concentrations is regulated by water mass mixing. The elevated concentrations of dissolved Ga in the subsurface are derived from the North Pacific Subtropical Mode Water, implying that the latter exerts significant influence on the spreading of dissolved Ga. The Ga concentration in intermediate waters is mainly governed by the Antarctic Intermediate Water (AAIW). A strong correlation (R² &gt; 0.8) is found between Ga concentration and salinity at depths of deep waters, and the non-conservative behavior of Ga in deep waters is difficult to detect in this region. Profile structures of Ga concentration inside the Philippine Sea basin are different from that outside the basin, indicating that the Ga concentration may reflect the upwelling of deep water within the basin. We further compared the concentration data of Ga with those from the GS01, GP16, GP15, IOC2002, and VERTEX cruises in terms of distribution, behavior and potential usage. We suggest that Ga exhibits promising potential as a new tracer for monitoring intermediate and deep water masses, and Ga concentration can serve as a good indicator for the AAIW and Upper Circumpolar Deep Water.</div></div>","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"674 ","pages":"Article 122573"},"PeriodicalIF":3.6,"publicationDate":"2024-12-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142887292","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":"Hydrothermal solubility of Dy hydroxide as a function of pH and stability of Dy hydroxyl aqueous complexes from 25 to 250 °C","authors":"Sarah E. Smith-Schmitz ,&nbsp;Alexander P. Gysi","doi":"10.1016/j.chemgeo.2024.122576","DOIUrl":"10.1016/j.chemgeo.2024.122576","url":null,"abstract":"<div><div>The rare earth elements (REE) have important applications in green energy technologies. The formation of mineral deposits in geologic systems commonly involves hydrothermal fluids which can mobilize the REE. However, the REE speciation is not well known as a function of pH. The thermodynamic properties of REE hydroxyl complexes used in geochemical models are based on the Helgeson-Kirkham-Flowers (HKF) equation of state parameters which were derived by extrapolation of low temperature experimental and estimated data. In this study, Dy hydroxide solubility experiments are combined with available literature data to improve these models from 25 to 250 °C and optimize the thermodynamic properties of Dy³⁺ and Dy hydroxyl complexes using GEMSFITS. Batch-type solubility experiments were conducted from 150 to 250 °C and at saturated water vapor pressure in perchloric acid solutions with initial pH values of 2 to 5 in 0.5 pH unit increments. The measured solubility of Dy hydroxide is retrograde with temperature and decreases with pH. The logarithm of total dissolved Dy molality ranges from −2.3 to −5.3 at 150 °C (pH 4.7–5.5), from −2.4 to −5.6 at 200 °C (pH 3.9–5.1), and from −3.7 to −6.9 at 250 °C (pH of 3.4 and 5.0). The optimized standard partial molal Gibbs energies of formation (∆_<em>f</em><em>G</em>°_<em>T</em>) derived for Dy³⁺ and DyOH²⁺ display a close to linear relationship with temperature, fitting with previous optimizations based on DyPO₄ solubility data in the literature. A comparison of the optimized ∆_<em>f</em><em>G</em>°_<em>T</em> values for aqueous Dy species with predictions from available HKF parameters indicates significant differences ranging from +11 to −26 kJ/mol between 25 and 250 °C. The experimental fits are used to derive the Dy hydroxide solubility products (<em>K</em>_s0) and formation constants for the hydrolysis of Dy (<em>β</em>_<em>n</em> with <em>n</em> = 1 to 3; Dy³⁺ + <em>n</em>OH⁻ = DyOH_<em>n</em>^3-<em>n</em>) as a function of temperature. The optimization method presented yields accurate thermodynamic properties for the Dy³⁺ aqua ions and the DyOH²⁺ species at the acidic to mildly acidic pH studied whereas more experimental work is needed at near-neutral and alkaline conditions to better constrain the other hydroxyl complexes. The optimized thermodynamic data have a significant impact on geochemical modeling of the mobility and solubility of REE minerals in acidic hydrothermal fluids.</div></div>","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"674 ","pages":"Article 122576"},"PeriodicalIF":3.6,"publicationDate":"2024-12-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142887303","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}