Acta Geochimica最新文献

{"title":"Behavior of opaque minerals in the Jilin H5 chondrite experimentally shocked to 12–133 GPa pressures","authors":"Xiande Xie,&nbsp;Jiarui Lin,&nbsp;Haiyang Xian","doi":"10.1007/s11631-025-00840-4","DOIUrl":"10.1007/s11631-025-00840-4","url":null,"abstract":"<div><p>Recovered samples of Jilin H5 chondrite experimentally shocked to 12–133 GPa were studied to explore the behavior of opaque minerals under shock loading using SEM–EDS, Raman spectroscopy, and TIMA. The following results were obtained. Firstly, at pressures lower than 53 GPa, the opaque minerals still keep the unmelted state, while at 78 GPa and higher, FeNi metal and troilite form eutectic intergrowths occurring as disorderly fine veinlets filling the shock-induced fractures in silicate minerals. Secondly, single kamacite grains still maintain their contour at 12 GPa, but a part of brittle troilite grains was fragmented and squeezed into the shock-induced fractures within kamacite grains. At 53 and 133 GPa, many more troilite fragments are poured in the kamacite interior to form disordered hybrid aggregates or to form squiggly strips, respectively. Similar phenomena are observed within single troilite grains, but the mineral squeezed into troilite grains is kamacite. Thirdly, chromite is a hard and refractory oxide mineral. When the shock pressure rises step by step from 12 to 133 GPa, the shock effect of chromite is only fragmentation. Its grain size decreases from tens of µm at 53 GPa to a few µm at 133 GPa. And, fourthly, native copper exhibits distinct redistribution behavior at high temperature. In Jilin samples shock-loaded to 12 GPa, copper initially located at troilite–kamacite interfaces partially transferred into small troilite grains containing fine FeNi particles. At 53 and 133 GPa, native copper preferentially transferred into larger troilite grains containing more particles of eutectic FeNi metal.</p></div>","PeriodicalId":7151,"journal":{"name":"Acta Geochimica","volume":"45 1","pages":"30 - 41"},"PeriodicalIF":1.3,"publicationDate":"2026-01-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146090831","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Gas impurities in salt cavern hydrogen storage: Formation mechanisms and impacts","authors":"Nuruddeen Inuwa Aminu,&nbsp;Efenwengbe Nicholas Aminaho,&nbsp;Faith Aminaho","doi":"10.1007/s11631-025-00843-1","DOIUrl":"10.1007/s11631-025-00843-1","url":null,"abstract":"<div><p>Hydrogen (H₂) is increasingly recognized as a viable low-carbon energy carrier. It can be produced by electrolysis and only emits water when consumed in fuel cells, making it essentially carbon free at the point of use. To support a large-scale hydrogen economy, however, vast quantities of H₂ must be stored to balance seasonal and diurnal mismatches between intermittent renewable generation and end-use demand. Salt caverns have long been considered one of the most promising options for underground hydrogen storage (UHS), owing to their low permeability, high geomechanical stability, and favorable operational characteristics. Despite these advantages, salt caverns present challenges related to in situ gas impurity generation during H₂ residence. Natural salt formations contain mineral inclusions such as anhydrite, carbonates, clays, and metal sulfides, which may participate in geochemical reactions that introduce contaminants, including hydrogen sulfide (H₂S), carbon dioxide (CO₂), methane (CH₄), and other trace gases, into stored hydrogen. Microbial processes and materials corrosion may further contribute to impurity formation. This review synthesizes the current state of knowledge on impurity generation mechanisms in salt cavern hydrogen storage. It examines geochemical, microbiologic, and corrosion-related pathways that may alter hydrogen purity and evaluates the consequences of these impurities for cavern integrity, infrastructure performance, and hydrogen fuel-cell applications. Understanding the geochemical, microbial, and operational characteristics of individual storage sites is essential for predicting impurity behavior and developing effective mitigation strategies. Further work is needed to quantify reaction rates, constrain uncertainty, and support the design of safe and efficient UHS projects in the future.</p></div>","PeriodicalId":7151,"journal":{"name":"Acta Geochimica","volume":"45 4","pages":"803 - 832"},"PeriodicalIF":1.4,"publicationDate":"2026-01-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s11631-025-00843-1.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148781963","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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":"Mineral-chemical and thermobarometric constraints on magma evolution during relict subduction initiation in the Laxmi Basin, Northern Indian Ocean","authors":"Anju Pandey,&nbsp;Dhananjai K. Pandey","doi":"10.1007/s11631-025-00844-0","DOIUrl":"10.1007/s11631-025-00844-0","url":null,"abstract":"<div><p>Precise crustal characterisation of the Laxmi Basin (LB) in the northern Indian Ocean has intrigued researchers for several decades. The LB plays a vital role in the final dispersal of Gondwana and the early opening of the Arabian Sea. The International Ocean Discovery Program (IODP) Expedition 355 penetrated igneous basement in the LB for the first time and recovered forearc basalts (FAB) and boninitic forearc basalts (B-FAB) from Site U1457. Here, we investigate crystallisation and differentiation conditions of the source magma using mineral-chemical and thermobarometric constraints. Analyses of these basalts characterise the clinopyroxenes as high-Mg augites with low TiO₂, high large-ion lithophile element (LILE) concentrations, negative Nb anomalies, and low total rare earth element (REE) contents. Most of the clinopyroxenes exhibit positive Eu anomalies in chondrite-normalised profiles, indicating their crystallisation prior to plagioclase. Plagioclases, on the other hand, range from labradorite to bytownite with flat to slightly light REE (LREE)-enriched patterns and positive Eu anomalies. Furthermore, clinopyroxene thermobarometry suggests crystallisation at ~1.5–6 kbar pressure (i.e., ~9–22 km depth) within the estimated temperature range of 1053–1219 °C. We infer that crystallisation may have peaked at approximately 3.25–4.25 kbar (~15–20 km), aligning with Moho depths (~12–14 km), followed by differentiation in sub-crustal and near-surface reservoirs (~10–11 km). Overall mineral-chemical signatures and pressure–temperature conditions confirm a nascent subduction origin of LB lavas.</p></div>","PeriodicalId":7151,"journal":{"name":"Acta Geochimica","volume":"45 3","pages":"703 - 717"},"PeriodicalIF":1.3,"publicationDate":"2026-01-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148196266","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Mineralization Mechanism of Cobalt in the Dahongshan Copper-Iron-Cobalt Polymetallic Deposit in Yunnan, China","authors":"Xuhao Kang,&nbsp;Runsheng Han,&nbsp;Yanwei Zhao,&nbsp;Dong Zhao,&nbsp;Hongsheng Gong,&nbsp;Liuqing Meng,&nbsp;Xing Mao,&nbsp;Long Sun,&nbsp;Yinkang Zhou","doi":"10.1007/s11631-025-00835-1","DOIUrl":"10.1007/s11631-025-00835-1","url":null,"abstract":"<div><p>The Dahongshan Cu–Fe–Co deposit, a key example of the Kangdian Cu–Fe polymetallic belt, features several forms of mineralization, including volcanic exhalative-sedimentation, metamorphism, and hydrothermal superposition. This deposit is rich in Cu, Fe, Co, Au, and Mo and exhibits strong structural control. Although recent studies have demonstrated highly variable enrichment of Co in ores, knowledge about its occurrence, enrichment patterns, and mechanisms is lacking. This study examined these aspects using an electron probe micro-analyzer and laser ablation inductively coupled plasma mass spectrometry. This revealed clear Co enrichment in key ore minerals, indicated by the presence of cobaltite, pyrite, chalcopyrite, and magnetite. Cobaltite comprised 31.00%–34.26% of the Co detected. Pyrite, indicating isomorphic substitution by Co, accounted for 0.01%–5.38% of the Co detected. Lower Co concentrations were detected in inclusions in magnetite (55.37 ppm–226 ppm) and chalcopyrite (0–290 ppm). Mapping of lithofacies at the 280 m level revealed clear spatial differences. Cobalt enrichment was highest in sulfide ores, averaging 261.63 ppm, followed by oxide ores (42.7 ppm–241.9 ppm), metasomatic albitized tuff (18.7 ppm–148.1 ppm), garnet-biotite schist (80.0 ppm–143.3 ppm), carbonate minerals (21.1 ppm–70.7 ppm), and quartz (2.5 ppm–59.8 ppm). Co-reduction from the anticlinal core (exploration lines B136–B120) to the edges highlights how the Dibadu anticline affects the structure. The metallogenic model outlines a three-stage enrichment process: (1) Volcanic exhalative sedimentation occurs, and Co forms sulfides as Co–Cl (CoCl₄^2-) complexes break down. This breakdown occurs when igneous fluids mix with seawater and during oxidation events, resulting in significantly enriched cobaltite and stage pyrite (I). (2) The second stage involves regional metamorphism at 290–330 °C and 16%–32% salinity, which helps to remobilize Co via fluid extraction and recrystallization, thereby adding Co to stage pyrite (II) via isomorphism. (3) Hydrothermal superposition creates zoned mineral groups ([pyrite + chalcopyrite] → bornite → chalcocite) along fractures at lower temperatures (245.1–92.3 °C) and with varying redox states. In this stage, the presence of Co supports stage (III) pyrite formation.</p></div>","PeriodicalId":7151,"journal":{"name":"Acta Geochimica","volume":"45 5","pages":"1366 - 1389"},"PeriodicalIF":1.4,"publicationDate":"2025-12-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149098790","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Tracing the evolution of granitic magmas revealed by fayalite–ferrosilite-bearing microgranular enclaves in Jiuyishan area of South China Block","authors":"Jing-Yi Liu,&nbsp;Quan Ou,&nbsp;Jian-Qing Lai,&nbsp;Feng Zi,&nbsp;Kun Wang,&nbsp;Wen-Zhou Xiao,&nbsp;Zhi-Cheng Lin,&nbsp;Cui-Yun Wang,&nbsp;Qian-Cheng Feng,&nbsp;Jia Liao","doi":"10.1007/s11631-025-00838-y","DOIUrl":"10.1007/s11631-025-00838-y","url":null,"abstract":"<div><p>Fayalite–ferrosilite-bearing enclaves in granite are a special phenomenon, and their formation mechanism is unclear. Here, a set of fayalite–ferrosilite-bearing microgranular enclaves occurred in granites from the Jiuyishan area, South China Block. The mineral grains (e.g., quartz–feldspar–biotite) show obvious cataclastic textures in host, while there are various mineral reaction textures (e.g., fayalite replaced by ferrosilite) in microgranular enclaves. The host rocks have high SiO₂ (68.40–70.59 wt%) contents and low Mg# (15–19). They exhibit fractionated chondrite-normalized rare-earth element (REE) patterns with negative Eu anomalies, Nb–Ta depletion, strongly positive Pb, and negative Sr anomalies. Both fayalite [Fa_87.5–92.7, (Fe₂SiO₄) ratios] and ferrosilite [Fs_74.6–79.9; (Fe₂Si₂O₆) ratios] grains show narrow variations in major elemental compositions, and their REE patterns are characteristic of heavy REE enrichment. All the estimated results of mineral crystallization conditions indicate that the related magma experienced a normal evolutionary trend. Moreover, there is no obvious difference in the crystallization conditions of the common minerals (e.g., biotites and Fe–Ti oxides) in the two microgranular enclaves and their host. Based on a previous study, we suggest that the studied microgranular enclaves were most likely generated by the accumulation of early crystallized minerals accompanied by their reactions with host magma during the rapid ascent and emplacement of granitic magmas. Comparison with other ferromagnesian mineral-bearing granites worldwide, the equilibrium state has not yet been reached between the studied ferromagnesian mineral and its host. This could be a new case for the genesis of ferromagnesian mineral-bearing granites.</p></div>","PeriodicalId":7151,"journal":{"name":"Acta Geochimica","volume":"45 3","pages":"751 - 766"},"PeriodicalIF":1.3,"publicationDate":"2025-12-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148196234","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Zircon textural and elemental evidence for the thermal state of the Carboniferous Oytag pluton in the West Kunlun Orogenic Belt, northwest China","authors":"Bingjin Yu,&nbsp;Yanjun Wang,&nbsp;Ying Wei,&nbsp;Shuilong Wang,&nbsp;Chuanlong Xu,&nbsp;Chengquan Wu,&nbsp;Weiguang Zhu,&nbsp;Chengbiao Leng","doi":"10.1007/s11631-025-00841-3","DOIUrl":"10.1007/s11631-025-00841-3","url":null,"abstract":"<div><p>This study presents new cathodoluminescence images and trace element data for zircon from the Carboniferous Oytag pluton in the West Kunlun Orogenic Belt, northwest China. We identify oscillatory and sector-zoned zircon grains that reflect equilibrium and disequilibrium crystal growth within the same trondhjemite pluton. The oscillatory zircon grains display negative correlations between Hf (10,638–13,648 ppm) and Ti (1.95–4.18 ppm) contents, highlighting the dominating role of fractionation in evolving magmas. In contrast, the sector-zoned zircon grains exhibit highly variable Ti contents (0.72–6.07 ppm) uncorrelated with Hf (8951–10,085 ppm), likely reflecting rapid cooling. At a fast growth rate with high undercooling, compatible elements (e.g., Hf) are not efficiently incorporated into the crystal lattice, while incompatible elements (e.g., Nb) are not promptly removed from the crystallizing front. Hf/Nb ratios in the light prismatic sectors are higher than those in the dark pyramidal sectors but overlap with those in the equilibrium oscillatory zircon. It is suggested that the light prismatic sectors are closer to the equilibrium with melts than dark pyramidal sectors. We attribute the formation of sector-zoned and oscillatory zircon to fast and slow cooling rates at the margin and interior of the Oytag pluton, respectively. We further infer that early, small magmatic systems may solidify at faster cooling rates than their postdating counterparts during the development of the Oytag back-arc basin.</p></div>","PeriodicalId":7151,"journal":{"name":"Acta Geochimica","volume":"45 3","pages":"639 - 651"},"PeriodicalIF":1.3,"publicationDate":"2025-12-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148196245","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Phosphorus fractions of ornithogenic soil profiles in coral islands using P k-edge XANES, sequential extraction, and 31P-NMR spectroscopy","authors":"Xianglong Xi,&nbsp;Yongli Zhou,&nbsp;Xueying Wang,&nbsp;Zhangqin Zheng,&nbsp;Yulu Xue,&nbsp;Libin Wu,&nbsp;Liqiang Xu,&nbsp;Xiaodong Liu","doi":"10.1007/s11631-025-00837-z","DOIUrl":"10.1007/s11631-025-00837-z","url":null,"abstract":"<div><p>The Xisha Islands accumulated significant amounts of phosphorus (P) due to seabird guano input. However, the seabird population has declined significantly in recent years as a result of climate change and human activities. As plant communities develop, significant amounts of organic matter and nitrogen were introduced into the soil through plant humus. To investigate the effects of different sources on the distribution of phosphorus fractions during the past ~1000 years of ecological evolution, we conducted <i>k-edge</i> x-ray absorption near-edge structural spectroscopy (XANES), sequential extraction, and ³¹P nuclear magnetic resonance (³¹P-NMR) of soil phosphorus in two ornithogenic soil profiles from the Xisha Islands. Combining these methods, the results revealed that magnesium-bound phosphorus (Mg-P) in modern guano underwent mineralization after deposition, and its content decreased by &gt; 50%. Subsequently, it may be released and combine with the abundant calcium-bearing minerals to transform into calcium-bound phosphorus (Ca-P). The results of XANES and sequential extraction indicated that Ca-P dominated the soil phosphorus pool by up to 70%–90%. The distributions of total organic carbon, total nitrogen, and total phosphorus in the soil profile are consistent with the evolutionary characteristics of nutrient supply from guano or plant humus during historical periods. In addition, although plant humus has lower total phosphorus content than guano, it may be an important source of organic phosphorus for topsoil. This study provides insights into the evolution of coral island ecosystems by examining phosphorus fractions and sources of phosphorus and offers valuable references for understanding nutrient cycling on tropical coral islands.</p></div>","PeriodicalId":7151,"journal":{"name":"Acta Geochimica","volume":"45 4","pages":"1041 - 1054"},"PeriodicalIF":1.4,"publicationDate":"2025-11-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148783423","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Geochemical and baddeleyite U–Pb geochronological characteristics of the 1.64 Ga diabase in the Southwestern Ordos Block: Implications for Paleoproterozoic extension, Neoproterozoic uplift and erosion, and Early Cretaceous extension","authors":"Yinglei Chang,&nbsp;Jinhai Luo,&nbsp;Zhuo Chen,&nbsp;Haotian Zhi,&nbsp;Bo Ji","doi":"10.1007/s11631-025-00832-4","DOIUrl":"10.1007/s11631-025-00832-4","url":null,"abstract":"<div><p>The Ordos Block (OB), a cratonic terrane with Archean-Paleoproterozoic crystalline basement in the western North China Craton (NCC), has long been considered tectonically stable. However, its basement architecture and Precambrian evolution remain poorly constrained due to extensive sedimentary cover and limited basement exposure. Here we present the first integrated petrological-geochemical-geochronological study of the previously unreported Maxia diabase from the southwestern OB margin. Outcropping in an abandoned quarry, the diabase is unconformably overlain by Ediacaran microclastic-carbonate sequences, preserving a well-developed paleoweathering surface. Whole-rock geochemical data suggest magma generation in an intracontinental rift setting. Both chondrite- and primitive mantle-normalized trace element patterns show remarkable similarities to regional Paleoproterozoic rift-related mafic suites. Laser ablation-inductively coupled plasma–mass spectrometry (LA-ICP-MS) baddeleyite U–Pb dating yields a discordia with an upper intercept age of 1643 ± 23 Ma and a lower intercept age of 122 ± 75 Ma. The upper intercept age of 1643 ± 23 Ma, representing the first documented evidence of ca. 1.64 Ga mafic magmatism along this cratonic margin, combined with regional geological constraints, indicates prolonged extensional tectonism (ca. 2.01–1.64 Ga) during the Columbia supercontinent assembly. The lower intercept age of 122 ± 75 Ma correlates with Early Cretaceous lithospheric thinning and NCC destruction during regional extensional reactivation. The paleoweathering surface between the diabase and Ediacaran strata records approximately 1 billion years of subaerial exposure (1643–635 Ma), attesting to prolonged regional weathering and exhumation. These results demonstrate that the Maxia diabase serves as an excellent archive for probing multiple magmatic events and early tectonic evolution since the Proterozoic at the southwestern margin of the OB.</p></div>","PeriodicalId":7151,"journal":{"name":"Acta Geochimica","volume":"45 4","pages":"1023 - 1040"},"PeriodicalIF":1.4,"publicationDate":"2025-11-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148783190","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Explosive lunar fission above a large low-velocity province","authors":"Matthew R. Edwards","doi":"10.1007/s11631-025-00834-2","DOIUrl":"10.1007/s11631-025-00834-2","url":null,"abstract":"<div><p>The giant impact hypothesis for the Moon’s origin has had difficulty explaining the nearly identical isotopic compositions of Moon rocks and rocks from Earth’s silicate mantle and crust. These similarities are instead more compatible with the Darwin-Wise hypothesis that the Moon arose by fission of a rapidly spinning Earth. To overcome problems with the fission model concerning structural stability and angular momentum conservation, some authors suggested that lunar fission was feasible on a more slowly rotating Earth if assisted by a nuclear explosion near the core-mantle boundary. In this light we consider the possible roles of the large low-velocity provinces (LLVPs). These long-lived structures have been implicated in diverse geophysical processes ranging from deep mantle plumes to continental breakup and mass extinction events. While the LLVPs have been seen as possible remnants of the giant impactor, we propose that one of them was the site of lunar ejection. Internal heating of the liquid core is suggested to have given rise to an equatorial belt just under the core-mantle boundary analogous to the one recently detected by Ma and Tkalčić [Sci Adv 10(35):eadn5562, 2024]. Upwellings of heat and volatiles from this belt then generated two antipodal, equatorial bulges: the precursors of the Pacific and African LLVPs. Prior to the emergence of plate tectonics, core heat was mainly dissipated by networks of deep mantle plumes extending above the proto-LLVPs. These plume networks represent conduits of weakened mantle through which proto-lunar materials could later rise in a focused ejection. Continuing heat buildup in the core eventually triggered a cataclysmic explosion in the Pacific proto-LLVP, possibly analogous to a planetary-scale kimberlite eruption. This explosion launched LLVP and overlying mantle material into a low Earth orbit, where it coalesced to form the Moon. Some possible sources of additional energy to power the explosion are considered, including nuclear fission, bolide impacts and a hypothetical gravitational decay process culminating in a ‘Ʌ event’.</p></div>","PeriodicalId":7151,"journal":{"name":"Acta Geochimica","volume":"45 1","pages":"15 - 29"},"PeriodicalIF":1.3,"publicationDate":"2025-11-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s11631-025-00834-2.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146090828","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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":"Minimum measured temperature at which np-Fe0 forms in ilmenite of lunar soil: Evidence from in-situ TEM heating experiments","authors":"Ziyan Qin,&nbsp;Yang Li,&nbsp;Chen Li,&nbsp;Ronghua Pang,&nbsp;Yuanyun Wen,&nbsp;Rui Li,&nbsp;Zixuan Han,&nbsp;Wenhui Ma,&nbsp;Xiongyao Li,&nbsp;Jianzhong Liu","doi":"10.1007/s11631-025-00831-5","DOIUrl":"10.1007/s11631-025-00831-5","url":null,"abstract":"<div><p>Nanophase iron particles (np-Fe⁰) have multiple formation mechanisms in lunar soil, which are mostly related to meteorite and micrometeorite impacts. Thermal modification of the impact is critical. Metal oxides have unique chemical and physical properties that allow np-Fe⁰ to form at a lower initial reaction temperature. Through the in-situ heating experiment of ilmenite in the Chang’e-5 sample, it was found that ilmenite can form np-Fe⁰ at 400 °C under high vacuum (10^–6 Pa). This fills in the missing information on the lowest measured temperature at which ilmenite forms np-Fe⁰. At 400–800 °C, only np-Fe⁰ and vesicles were formed without new Ti-rich minerals. At the same time, thermodynamic calculations showed that decomposition of ilmenite occurs in two stages. The experiments correspond to the initial stage of ilmenite thermal decomposition under high vacuum. The study explains the thermal decomposition reaction of ilmenite in a vacuum environment, provides a reference for the minimum measured temperature required for the formation of np-Fe⁰, and further improves the formation mechanism of np-Fe⁰.</p></div>","PeriodicalId":7151,"journal":{"name":"Acta Geochimica","volume":"45 1","pages":"55 - 64"},"PeriodicalIF":1.3,"publicationDate":"2025-11-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146091026","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}