Acta Geochimica最新文献

{"title":"Features of the spatial and seasonal distribution of hydrocarbons in water of the North Crimean Canal, Crimea","authors":"O. V. Soloveva,&nbsp;E. A. Tikhonova,&nbsp;N. Yu. Mirzoeva","doi":"10.1007/s11631-024-00719-w","DOIUrl":"10.1007/s11631-024-00719-w","url":null,"abstract":"<div><p>The North Crimean Canal is a watercourse originating from the Kakhovka Reservoir and flowing into the Crimean Peninsula. The canal is an important source of drinking water supply and is also used to irrigate agricultural lands and fill fish farms. Due to its location, in recent years its functioning has not been stable, and the processes occurring along the canal have been poorly studied. In this study, we determined the content (with a safety assessment), features of spatial and seasonal distribution, and potential sources of hydrocarbons in the water of the North Crimean Canal, Crimea. During the study period (from March to November 2023) in the primary canal, the content of aliphatic hydrocarbons did not exceed sanitary standards (0.05 mg·L⁻¹). Their increased concentrations in the secondary canals could be associated with the input of organic substances into the canal water as it moves across the Crimean Peninsula. The composition of <i>n-</i>alkanes had temporal and spatial variability. In the period from spring to autumn, the content of autochthonous compounds decreased sharply. The share of allochthonous compounds increased as a consequence of the natural processes. The analysis of biogeochemical markers showed that autochthonous compounds produced by phytoplankton predominated in the spring–summer period. Subsequently, they had less importance, and the main share was accounted for allochthonous <i>n-</i>alkanes.</p></div>","PeriodicalId":7151,"journal":{"name":"Acta Geochimica","volume":"44 2","pages":"247 - 259"},"PeriodicalIF":1.4,"publicationDate":"2024-07-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141656572","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":"Geochemistry and petrogenesis of magnesian high-K granitoids from Bundelkhand Craton, Central India: New insights into crustal evolution","authors":"Shailendra K. Prajapati,&nbsp;Meraj Alam,&nbsp;Parashar Mishra,&nbsp;Hemant Kumar","doi":"10.1007/s11631-024-00717-y","DOIUrl":"10.1007/s11631-024-00717-y","url":null,"abstract":"<div><h3>Background</h3><p>The Bundelkhand Craton is significant for preserving the multiphase granitoids magmatism from Paleoarchean to Neoarchean periods. It consists of a variety of granite rocks, including TTGs, sanukitoids, and high-K granitoids. This study presents geochemical characteristics of high-silica (68.97 wt.%–73.99 wt.%), low-silica (58.73 wt.%–69.94 wt.%), and high K₂O (2.77 wt.%–6.16 wt.%) contents of granitoids.</p><h3>Objective</h3><p>The data on Bundelkhand Craton's granitic magmatism and geodynamics is not sufficiently robust. Geochemical data from this study will be used to further understand the origin, source, and petrogenesis of granitoid rocks and their implications for the evolution of geodynamics.</p><h3>Methodology</h3><p>Twenty-one samples were collected and analyzed for major, trace, and REE elements. Major elements were measured using X-ray fluorescence spectrometry (XRF), and trace and REE elements were analyzed by ICP-MS. Standard procedures from the Geological Survey of India were followed.</p><h3>Results</h3><p>The geochemical analysis presents high-silica (68.97-73.99 wt. %), low-silica (58.73-69.94 wt. %), and high K2O (2.77-6.16 wt. %) contents in granitoids, classified as granite-granodiorite. The rocks are calcic to calcalkalic, magnesian, and range from peraluminous to metaluminous composition. REE patterns showed strong LREE enrichment relative to HREEs, with prominent negative Eu anomalies corresponding to earlier plagioclase fractionation. Multi-element patterns revealed negative anomalies in Nb, Sr, P, and Ti and positive anomalies in Pb.</p><h3>Conclusion</h3><p>The geochemical signatures attributed to the post-collisional magma generation and continental crustal contamination. The studied rocks show A-type and A2-type lineage, suggesting they originated from the melting of continental crust during transitional/post-collisional tectonic activity. The formation of hybrid granitoids in the Bundelkhand Craton is connected to the fractionation of hybrid magmas in shallow-seated magma chambers during these tectonic processes.</p></div>","PeriodicalId":7151,"journal":{"name":"Acta Geochimica","volume":"44 1","pages":"36 - 58"},"PeriodicalIF":1.4,"publicationDate":"2024-07-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141661514","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":"Geochemistry and mineral chemistry of granitic rocks from west Wadi El Gemal area, southern Eastern Desert of Egypt: Indicators for highly fractionated syn- to post-collisional Neoproterozoic felsic magmatism","authors":"Hesham Mokhtar,&nbsp;Adel A. Surour,&nbsp;Mokhles K. Azer,&nbsp;Minghua Ren,&nbsp;Amir Said","doi":"10.1007/s11631-024-00714-1","DOIUrl":"10.1007/s11631-024-00714-1","url":null,"abstract":"<div><p>Leucogranite, pegmatite, and aplite from selected areas in the Wadi El Gemal area in the southern Eastern Desert of Egypt were investigated geochemically for their petrogenesis. These rocks represent a significant episode of felsic magmatism during the late stage of the Pan-African orogeny in the evolution of the Arabian–Nubian Shield (ANS) during the Late Neoproterozoic. On a petrographic basis, the leucogranite is sometimes garnetiferous and can be distinguished into monzogranite, syenogranite, and alkali feldspar granite. The analyses of muscovite, biotite, garnet, and apatite reveal the magmatic nature of the studied leucogranite. The investigated leucogranite, pegmatite, and aplite are alkali-calcic, calc-alkaline, and peraluminous. The peraluminous nature of these rocks is evidenced by using the chemical analyses of biotite. These studied rocks show a slight enrichment in light rare-earth elements (LREEs) and large-ion lithophile elements (LILE, especially Rb and Th), with an insignificant depletion of heavy rare-earth elements (HREEs). On a geochemical basis, the leucogranite, pegmatite, and aplite in the study area crystallized from multiple-sourced melts that include mafic, metagraywake, and pelitic. They were derived from melts generated at crystallization temperatures around 568–900 °C for leucogranite, 553–781 °C for pegmatite, and 639–779 °C for aplite based on the Zr saturation geothermometers, and at a pressure around 0.39–0.48 GPa, i.e. shallow depth intrusions. The studied felsic rocks have strong negative Eu anomalies, which are very consistent with an upper crust composition, indicating fractionation of feldspar cumulates. Also, they show a moderate La/Sm ratio indicating combined magmatic processes represented by partial melting and fractional crystallization. Integration of whole-rock chemical composition and mineral microanalysis suggests that felsic magmatism in the west Wadi El Gemal area produced voluminous masses of syn- to post-collisional granite, pegmatite, and aplite. An evolutionary three-stage model is presented to understand late magmatism in the ANS in terms of a geodynamic model. Such a model discusses the propagation of felsic magmatism in the ANS during syn-collisional to post-collisional stages.</p></div>","PeriodicalId":7151,"journal":{"name":"Acta Geochimica","volume":"44 1","pages":"163 - 188"},"PeriodicalIF":1.4,"publicationDate":"2024-07-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141673228","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":"Fresh insights into the onset of big mantle wedge beneath the North China Craton","authors":"Yingpeng Wang,&nbsp;Xuance Wang,&nbsp;Wen Zhang,&nbsp;Xiaowei Yu,&nbsp;Ligong Wang,&nbsp;Jinhui Wang,&nbsp;Peigang Zhu,&nbsp;Yongbin Wang","doi":"10.1007/s11631-024-00716-z","DOIUrl":"10.1007/s11631-024-00716-z","url":null,"abstract":"<div><p>The onset of the big mantle wedge (BMW) structure beneath the North China Craton remains debated. Research on the genesis of Late Mesozoic granites associated with gold deposits in the Jiaodong Peninsula above the BMW could provide fresh insights into this question. The monzogranite from the Zhaoxian-Shaling gold district was intruded during 154–148 Ma. This I-type granite has high-K calc-alkaline and metaluminous characteristics. The monzogranite formed at medium temperatures (718–770 °C) and was generated in a thickened lower crust at depths within the stability field of garnet. The monzogranite's high zircon Ce⁴⁺/Ce³⁺ and Eu_N/Eu_N* values and low FeO^T/MgO ratios, suggest that it formed in a high oxygen environment. Its variable ε_Hf(t) values with T_DM2 of 1.93–2.87 Ga imply that it originated from the melting of ancient crust basement, with contributions from mantle-derived materials. The granite's enrichment in LREEs and LILEs, and depletion in HREEs and HFSEs, along with its trace element tectonic discrimination diagrams and medium Sr/Y, indicate an adakite affinity in an active continental margin setting. The transition from S-type granites to I-type granites and finally to A-type granites observed in the eastern part of North China Craton suggests a shift in the tectonic environment from compression to extension. This change is also reflected in the transition from flat subduction to steep subduction. Therefore, the monzogranite was formed in a tectonic transition setting triggered by a change in the subduction angle of the Paleo-Pacific Ocean slab during the Late Jurassic. This event may have marked the initiation of the BMW above the North China Craton.</p></div>","PeriodicalId":7151,"journal":{"name":"Acta Geochimica","volume":"44 1","pages":"145 - 162"},"PeriodicalIF":1.4,"publicationDate":"2024-07-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141687288","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":"Mineralogical and geochemical characterization of the Wadi Natash volcanic field (WNVF), Egypt: Alkaline magmatism in a Late Cretaceous continental rift system","authors":"Adel A. Surour,&nbsp;Ahmed A. Madani,&nbsp;Mohamed A. El-Sharkawi","doi":"10.1007/s11631-024-00702-5","DOIUrl":"10.1007/s11631-024-00702-5","url":null,"abstract":"<div><p>The Wadi Natash volcanic field (WNVF) in the south of the Eastern Desert of Egypt is a typical example of well-preserved intraplate alkaline magmatism during the Late Cretaceous, i.e., prior to the Oligo-Miocene Red Sea rift. We compiled stratigraphic sections at two sectors; namely East Gabal Nuqra and West Khashm Natash (WKN) where the volcanic flows are intercalated with the Turonian Abu Agag sandstone with occasional paleosols when volcanic activity is intermittent. Peridotite mantle xenoliths are encountered in the first sector whereas flows in the second sector are interrupted by trachyte plugs and ring dykes. On a geochemical basis, the mafic melt originating from the lithospheric mantle beneath the WNVF practiced ~ 5% partial melting of phlogopite-bearing garnet peridotite. Basalts dominate in the two sectors and highly evolved (silicic) rocks are confined to the WKN sector. Rejuvenation of ancient Precambrian fractures following the NW–SE and ENE-WSW trends facilitated the ascend of Late Cretaceous mantle-derived alkaline magma. Structurally, the WNVF developed at the eastern shoulder of the so-called “Kom Ombo-Nuqra-Kharit rift system” that represents a well-defined NW-trending intracontinental rift basin in the southern Eastern Desert. In such a structural setup, the Natash volcanic are confined to half-grabens at the East Gabal Nuqra sector whereas the West Khashm Natash sector is subjected to extensional stresses that propagated eastwards. The WNVF is a typical example of fluvial clastics (Turonian) intercalation with rift-related alkaline volcanic rocks in northeast Africa.</p></div>","PeriodicalId":7151,"journal":{"name":"Acta Geochimica","volume":"43 6","pages":"1169 - 1191"},"PeriodicalIF":1.4,"publicationDate":"2024-06-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142664451","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":"Geochemistry of Neoproterozoic metavolcanic rocks from the Tahtai Logomiti area, Tigrai, Northern Ethiopia: Implication for petrogenesis and tectonic settings","authors":"Azeb Gebremicale,&nbsp;Mulugeta Alene,&nbsp;Teklay Gidey","doi":"10.1007/s11631-024-00712-3","DOIUrl":"10.1007/s11631-024-00712-3","url":null,"abstract":"<div><p>The Tahtai Logomiti area is characterized by metavolcanic and metavolcaniclastic interbedded with clastic and carbonate metasedimentary rocks of Neoproterozoic age. New geological, petrographic, major, and trace elements data were used to evaluate the metamorphism, petrogenesis, and paleo-tectonic setting of the area. The field and petrographic observation indicate that the area has undergone greenschist facies metamorphism. Based on mineralogy and geochemical attributes, these metavolcanic rocks are classified as basalt, basaltic-andesite, andesite, and dacite. The moderate degrees of light rare earth element (LREE) enrichment, flat heavy rare earth element (HREE) pattern, and low Nb/Y ratio, represent shallow mantle sources. In addition to that, the TiO₂/Yb vs. Nb/Yb diagram, high (La/Yb)N ratio (&gt; 3.44), indicates shallow melting and depleted magma sources. However, the high ratios of (Th/Ta) &gt; 3.8, (La/Ta) &gt; 38, and low ratios of (Th/La) &lt; 1, (Nb/La) &lt; 1, and high Pb content would indicate crustal contamination of the magma. The discrimination diagram and trace element ratios (Nb/Y, La/Sc, La/Y, and La/Th) indicate that the metavolcanic rocks have a calc-alkaline affinity. In addition, the Zr-Nb-Y and Th-Hf-Ta plots show that the rocks formed under a volcanic-arc setting. The general petrological and geochemical characteristics of the Tahtai Logomiti metavolcanic rocks suggest that the area is associated with subduction-related arc accretion of the Arabian Nubian Shield.</p></div>","PeriodicalId":7151,"journal":{"name":"Acta Geochimica","volume":"44 1","pages":"128 - 144"},"PeriodicalIF":1.4,"publicationDate":"2024-06-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143362025","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":"Assessing the impact of climate change on dissolved oxygen using a flow field ecosystem model that takes into account the anaerobic and aerobic environment of bottom sediments","authors":"Jinichi Koue","doi":"10.1007/s11631-024-00711-4","DOIUrl":"10.1007/s11631-024-00711-4","url":null,"abstract":"<div><p>This study examines the potential impacts of climate change on Lake Biwa, Japan’s largest freshwater lake, with a focus on temperature, wind speed, and precipitation variations. Leveraging data from the IPCC Sixth Assessment Report, including CCP scenarios, projecting a significant temperature rise of 3.3–5.7 °C in the case of very high GHG emission power, the research investigates how these shifts may influence dissolved oxygen levels in Lake Biwa. Through a one-dimensional model incorporating sediment redox reactions, various scenarios where air temperature and wind speed are changed are simulated. It is revealed that a 5 °C increase in air temperature leads to decreasing 1–2 mg/L of dissolved oxygen concentrations from the surface layer to the bottom layer, while a decrease in air temperature tends to elevate 1–3 mg/L of oxygen levels. Moreover, doubling wind speed enhances surface layer oxygen but diminishes it in deeper layers due to increased mixing. Seasonal variations in wind effects are noted, with significant surface layer oxygen increases from 0.4 to 0.8 mg/L during summer to autumn, increases from 0.4 to 0.8 mg/L in autumn to winter due to intensified vertical mixing. This phenomenon impacts the lake’s oxygen cycle year-round. In contrast, precipitation changes show limited impact on oxygen levels, suggesting minor influence compared to other meteorological factors. The study suggests the necessity of comprehensive three-dimensional models that account for lake-specific and geographical factors for accurate predictions of future water conditions. A holistic approach integrating nutrient levels, water temperature, and river inflow is deemed essential for sustainable management of Lake Biwa’s water resources, particularly in addressing precipitation variations.</p></div>","PeriodicalId":7151,"journal":{"name":"Acta Geochimica","volume":"44 1","pages":"11 - 22"},"PeriodicalIF":1.4,"publicationDate":"2024-06-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s11631-024-00711-4.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143362027","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":"Petrogenesis of late Cretaceous high Ba–Sr granodiorites, SE Lhasa block, China: implications for the reworking of juvenile crust and continental growth","authors":"Li-Hang Lin,&nbsp;Ren-Zhi Zhu,&nbsp;Shao-Cong Lai,&nbsp;Jiang-Feng Qin,&nbsp;Yu Zhu,&nbsp;Shao-Wei Zhao,&nbsp;Min Liu","doi":"10.1007/s11631-024-00708-z","DOIUrl":"10.1007/s11631-024-00708-z","url":null,"abstract":"<div><p>The high Ba–Sr rocks can provide significant clues about the evolution of the continent lithosphere, but their petrogenesis remains controversial. Identifying the Late Cretaceous high Ba–Sr granodiorites in the SE Lhasa Block could potentially provide valuable insights into the continent evolution of the Qinghai-Tibet Plateau. Zircon U–Pb ages suggest that the granodiorites were emplaced at 87.32 ± 0.43 Ma. Geochemically, the high Ba–Sr granodiorites are characterized by elevated K₂O + Na₂O contents (8.18–8.73 wt%) and K₂O/Na₂O ratios (0.99–1.25, mostly &gt; 1), and belong to high-K calc-alkaline to shoshonitic series. The Yonglaga granodiorites show notably high Sr (653–783 ppm) and Ba (1346–1531 ppm) contents, plus high Sr/Y (30.92–38.18) and (La/Yb)_N (27.7–34.7) ratios, but low Y (20.0–22.8 ppm) and Yb (1.92–2.19 ppm) contents with absence of negative Eu anomalies (δEu = 0.83–0.88), all similar to typical high Ba–Sr granitoids. The variable zircon <i>ε</i>Hf(<i>t</i>) values of − 4.58 to + 12.97, elevated initial ⁸⁷Sr/⁸⁶Sr isotopic ratios of 0.707254 to 0.707322 and low <i>ε</i>Nd(<i>t</i>) values of − 2.8 to − 3.6 with decoupling from the Hf system suggest that a metasomatized mantle source included significant recycled ancient materials. The occurrence of such high Ba–Sr intrusions indicates previous contributions of metasomatized mantle-derived juvenile material to the continents, which imply the growth of continental crust during the Late Cretaceous in the SE Lhasa. Together with regional data, we infer that the underplated mafic magma provides a significant amount of heat, which leads to partial melting of the juvenile crust. The melting of the metasomatized mantle could produce a juvenile mafic lower crust, from which the high Ba–Sr granitoids were derived from reworking of previous mafic crust during the Late Cretaceous (ca. 100–80 Ma) in the SE Lhasa.</p></div>","PeriodicalId":7151,"journal":{"name":"Acta Geochimica","volume":"44 1","pages":"86 - 111"},"PeriodicalIF":1.4,"publicationDate":"2024-06-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143362179","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":"Unveiling Nb–Ta mineralization processes: Insight from quartz textural and chemical characteristics in the Songshugang deposit, Jiangxi Province, South China","authors":"Hengsong Zhang,&nbsp;Shaohao Zou,&nbsp;Xilian Chen,&nbsp;Deru Xu,&nbsp;Zhilin Wang,&nbsp;Yongwen Zhang,&nbsp;Hua Wang","doi":"10.1007/s11631-024-00705-2","DOIUrl":"10.1007/s11631-024-00705-2","url":null,"abstract":"&lt;div&gt;&lt;p&gt;The Songshugang deposit is a large Ta–Nb deposit in South China, with Ta–Nb mineralization associated genetically with the granite and pegmatite. A diversity of quartz from topaz–albite granite, quartz–mica pegmatite, quartz–feldspar pegmatite, and quartz–fluorite pegmatite at Songshugang was studied by CL and LA–ICP–MS in order to constrain enrichment mechanisms of Nb and Ta and to find geochemical indicators of quartz for rare metal deposits. Cathodoluminescence image illuminates a canvas of complexity, the quartz from topaz–albite granite, quartz–mica pegmatite, quartz–feldspar pegmatite, and quartz–fluorite pegmatite, exhibits numerous dark CL streaks, patches, and a series of healed fractures. These textures suggest that the rocks were fractured because of deep crustal pressure, and underwent later hydrothermal metasomatism and quartz filling. The quartz from quartz–fluorite pegmatite present limited patches or fractures but distinct growth bands, indicating that the melt fluid composition during the formation of quartz at this stage varies greatly and is less affected by mechanical fragmentation. The LA–ICP–MS analysis of quartz shows that there is a positive correlation between Al and Li in the quartz from topaz–albite granite, quartz–mica pegmatite, quartz–feldspar pegmatite, to quartz–fluorite pegmatite, indicating that Al mainly enters the quartz lattice through charge compensation substitution mechanism with Li. However, our data deviate from the theoretical Li:Al mass ratio of ~ 1:3.89 in quartz, indicating that there may be competition between H&lt;sup&gt;+&lt;/sup&gt; and Li in a water-rich magmatic environment. The quartz from topaz–albite granite is enriched in K and Na elements, and the quartz from quartz–fluorite pegmatite is enriched in fluorite with a low Ca content in quartz, further elucidating that these rocks were subjected to hydrothermal metasomatism. From topaz–albitite granite to quartz–fluorite pegmatite, Al, Li and Ge content and Al/Ti, Ge/Ti, Sb/Ti ratios in quartz gradually increased, but Ti content gradually decreased, reflecting the high evolution of magma, which can enrich rare metal elements. Based on the characteristics of quartz CL textures and trace elements in topaz–albite granite, quartz–mica pegmatite, quartz–feldspar pegmatite, and quartz–fluorite pegmatite, combined with the albitization and K-feldspathization of rocks, it is suggested that the Nb–Ta mineralization in Songshugang may be influenced by the combined action of magmatic crystallization differentiation and fluid metasomatism. By comparing the quartz in the Songshugang pluton with the quartz in the granite type and pegmatite type rare metal deposits recognized in the world, the Songshugang pegmatite share similarities with the LCT-type pegmatite. Combined with previous studies, the Ge/Ti &gt; 0.1 and Ti &lt; 10 ppm, as well as Al, Li, Ge, Sb, K, Na contents and Al/Ti, Sb/Ti ratios in quartz have the potential to be a powerful exploration marker fo","PeriodicalId":7151,"journal":{"name":"Acta Geochimica","volume":"43 4","pages":"737 - 753"},"PeriodicalIF":1.4,"publicationDate":"2024-06-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142413058","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":"Rebuilding the theory of isotope fractionation for evaporation of silicate melts under vacuum condition","authors":"Jie Wang,&nbsp;Yun Liu","doi":"10.1007/s11631-024-00709-y","DOIUrl":"10.1007/s11631-024-00709-y","url":null,"abstract":"<div><p>Isotope effects are pivotal in understanding silicate melt evaporation and planetary accretion processes. Based on the Hertz–Knudsen equation, the current theory often fails to predict observed isotope fractionations of laboratory experiments due to its oversimplified assumptions. Here, we point out that the Hertz-Knudsen-equation-based theory is incomplete for silicate melt evaporation cases and can only be used for situations where the vaporized species is identical to the one in the melt. We propose a new model designed for silicate melt evaporation under vacuum. Our model considers multiple steps including mass transfer, chemical reaction, and nucleation. Our derivations reveal a kinetic isotopic fractionation factor (KIFF or <i>α</i>) <i>α</i>_{our model} = [<i>m</i>(¹species)/<i>m</i>(²species)]^0.5, where <i>m</i>(species) is the mass of the reactant of reaction/nucleation-limiting step or species of diffusion-limiting step and superscript 1 and 2 represent light and heavy isotopes, respectively. This model can effectively reproduce most reported KIFFs of laboratory experiments for various elements, i.e., Mg, Si, K, Rb, Fe, Ca, and Ti. And, the KIFF-mixing model referring that an overall rate of evaporation can be determined by two steps jointly can account for the effects of low <i>P</i>_H2 pressure, composition, and temperature. In addition, we find that chemical reactions, diffusion, and nucleation can control the overall rate of evaporation of silicate melts by using the fitting slope in ln(− ln<i>f</i>) versus ln(<i>t</i>). Notably, our model allows for the theoretical calculations of parameters like activation energy (<i>E</i>_a), providing a novel approach to studying compositional and environmental effects on evaporation processes, and shedding light on the formation and evolution of the proto-solar and Earth-Moon systems.</p></div>","PeriodicalId":7151,"journal":{"name":"Acta Geochimica","volume":"43 4","pages":"661 - 676"},"PeriodicalIF":1.4,"publicationDate":"2024-06-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141344907","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}