Lithos最新文献

{"title":"Neoarchean crustal thickness and geothermal gradient of northwestern Yangtze Craton, South China: Constraints from geochemistry and zircon U-Pb-Hf isotopes of TTGs","authors":"Peiwen Liu ,&nbsp;Xiaozhong Ding ,&nbsp;Yanxue Liu ,&nbsp;Guochen Dong ,&nbsp;Jibiao Zhang ,&nbsp;Tingdong Li","doi":"10.1016/j.lithos.2025.108248","DOIUrl":"10.1016/j.lithos.2025.108248","url":null,"abstract":"<div><div>The Neoarchean geodynamic regimes of the continental crust formation and evolution of the Yangtze Craton remain enigmatic. The thickness and geothermal gradient of the continental crust could provide direct clues for understanding the geodynamic regimes of the early Earth. The lower crust-derived tonalite–trondhjemite–granodiorite (TTG) is an ideal lithology because its melting pressure and temperature conditions can be used to estimate the minimum crustal thickness and Moho temperature. In the Yudongzi Complex of the northwestern Yangtze Craton, three episodes of Neoarchean TTG magmatism are recognized at ∼2.75–2.7 Ga, ∼2.62–2.60 Ga and ∼ 2.53–2.50 Ga. These TTGs are characterized by low MgO (0.28–1.07 wt%), Cr (3.80–10.64 wt%) and Ni contents (2.06–7.86 wt%) and Mg# values (21–45), high Sr/Y (41.2–235.3) and (La/Yb)_N (19.6–127.9) values and positive ɛ_Hf(t) values of +1.5 to +6.8 and are derived from the partial melting of juvenile thickened lower crust. The thermodynamic and trace element simulation results indicate that the geochemical compositions of these three episodes of crust-derived TTG magmas are best matched by the melts generated at 1.2 GPa and 830 °C, 1.4 GPa and 870 °C and 1.3 GPa and 840 °C, respectively. Together with the thermodynamic formula, we estimate the Neoarchean crustal thicknesses as 36–43 km with geothermal gradients of 14–21 °C/km for the ∼2.75–2.7 Ga TTG gneisses, 43–50 km with geothermal gradients of 12–17 °C/km for the ∼2.62–2.60 Ga TTG gneisses and 40–46 km with geothermal gradients of 13–18 °C/km for the ∼2.52–2.50 Ga TTG gneisses. These observations, in conjunction with the occurrence of coeval subduction-related igneous rocks in the adjacent region, suggest that the cratonic lithosphere has gradually stabilized and that slab subduction was the most likely geodynamic regime leading to the Neoarchean magmatism in the northwestern Yangtze Craton.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"516 ","pages":"Article 108248"},"PeriodicalIF":2.5,"publicationDate":"2025-09-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145046311","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":"Ultramafic rocks in the Bay of Islands Ophiolite complex, Newfoundland Appalachians.","authors":"Keiko Hattori ,&nbsp;Fabio G. Stern ,&nbsp;Jean H. Bédard","doi":"10.1016/j.lithos.2025.108249","DOIUrl":"10.1016/j.lithos.2025.108249","url":null,"abstract":"<div><div>The Bay of Islands Ophiolite Complex of the western Newfoundland Appalachians is exposed in four massifs, from north to south: Table Mountain, North Arm Mountain, Blow-me-Down Mountain, and the Lewis Hills. Each massif contains a mantle tectonite unit dominated by harzburgite with subordinate lherzolitic rocks, with minor dykes and lenses of dunite and pyroxenite. In the Blow-me-Down Mountain massif, a thick dunite layer (up to 5 km), separates the gabbroic unit from harzburgitic mantle tectonites. This paper focuses on the harzburgitic and dunitic facies of the Blow-me-Down Mountain massif, with additional samples from the North Arm Mountain and Table Mountain massifs. Bulk rock compositions and mineral chemistry of olivine and spinel indicate that the harzburgites are mantle restites, whereas dunites are cumulates formed from mafic melt. Concentrations of Ir-type PGE are consistently high for harzburgite and variably low for dunite, supporting this interpretation. Values of spinel Cr# in harzburgites and subordinate lherzolites show a wide range (0.3 to 0.9). Mantle harzburgites with low spinel Cr# (&lt; 0.6) have mineral-chemical signatures similar to abyssal peridotites formed at a slow spreading ridge. The magmatism during this period produced overlying tholeiitic gabbros and basalts. High spinel Cr# values (&gt; 0.6) in harzburgite require extensive partial melting in a subduction setting. This change in the tectonic setting is supported by clinopyroxene compositions and dunite dykes with high Cr# (&lt; 0.9) cutting earlier formed mantle harzburgite and gabbro units.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"516 ","pages":"Article 108249"},"PeriodicalIF":2.5,"publicationDate":"2025-09-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145106458","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":"Petrogenesis of granitic pegmatites in the Chinese Altay: Insights from apatite, garnet, and quartz geochemistry","authors":"Xin Zhang ,&nbsp;Meng-Tao Wang ,&nbsp;Zhan-Long Ma ,&nbsp;Zi-Zeng Liu ,&nbsp;Jing-Yu Zhao ,&nbsp;Zheng-Hang Lv ,&nbsp;Hui Zhang ,&nbsp;Yong Tang","doi":"10.1016/j.lithos.2025.108250","DOIUrl":"10.1016/j.lithos.2025.108250","url":null,"abstract":"<div><div>Granitic pegmatites, derived from highly evolved and volatile-rich felsic magmas, represent one of the world’s major sources of rare metals, including Li, Be, Nb, Ta, Zr, Hf, Rb, and Cs. Despite their economic importance, the petrogenesis of pegmatites remains a subject of considerable debate. In this study, we conducted in situ major- and trace-element analyses of apatite, garnet, and quartz from six pegmatite bodies (Xiaokalasu, Dakalasu, Yelaman, Jiamanhaba, Amulagong, and Tiemulete) in the Chinese Altay, using laser ablation–inductively coupled plasma–mass spectrometry (LA-ICP-MS). Apatite samples display elevated MnO contents (0.08–7.39wt%; mean = 1.5; N = 78), low Zr/Hf ratios (0.38–69.43; mean = 9.67), and high Y/Ho ratios (29.63–120.97; mean = 45.26). Garnet samples exhibit variable Zr/Hf ratios (4.91–239.59; mean = 31.67; N = 101) but consistently high Y/Ho ratios (27.29–240.84; mean = 50.94). Quartz samples are characterized by high Ge/Ti ratios (0.16–7.68; mean = 1.12; N = 172) and Al/Ti ratios (1.22–1952.20; mean = 40.12). These diagnostic geochemical signatures provide strong evidence for a hydrothermal origin, confirming that the magmas of these six pegmatites reached magmatic fluid saturation during crystallization, as predicted by the J-B model. Importantly, distinct ionic radii, charge, chemical reactivity, and crystal structure account for the varied geochemical behaviours of rare metals during hydrothermal processes: (1) Nb-Ta concentrations show only weak correlations with Y/Ho ratios, suggesting limited hydrothermal influence on their enrichment; (2) In contrast, Li concentrations exhibit strong positive correlations with both Al/Ti and Ge/Ti ratios, indicating significant hydrothermal mobilization and subsequent mineralization. These results provide new constraints on the hydrothermal processes controlling rare-element enrichment and mineralization, offering particularly valuable insights into the mechanisms of Li enrichment.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"516 ","pages":"Article 108250"},"PeriodicalIF":2.5,"publicationDate":"2025-09-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145061212","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":"Geochemical and geochronological insights into the metal fertility of magmas associated with the Kennon Cu–Au porphyry deposit of Black Mountain in the Baguio Mineral District, North Luzon, Philippines.","authors":"Kennethjer Alejo ,&nbsp;Mayuko Fukuyama","doi":"10.1016/j.lithos.2025.108243","DOIUrl":"10.1016/j.lithos.2025.108243","url":null,"abstract":"<div><div>New geochronological, whole-rock, and zircon geochemical data for diorite and andesite porphyries from the Kennon Cu–Au porphyry deposit located in the Black Mountain intrusive complex, in the Baguio Mineral District in the Benguet Province, Northern Luzon, Philippines, are presented to evaluate ore-forming processes. The U–Pb geochronological data indicate that diorite and andesite porphyries were emplaced synchronously at ∼3.36 to 3.10 Ma, coinciding with the mineralization event driven by the fertile Pliocene magmatism related to the subduction of the Scarborough ridge along the Manila Trench. Whole-rock and zircon geochemistry show moderate to high degrees of magmatic fractionation, as reflected in Nb/Ta, Zr/Hf, and Rb/Sr ratios, along with zircon Dy/Yb, Hf, and Th/U values. Zircon trace element characteristics, including Ce⁴⁺/Ce³⁺ ratios (&gt;300), Eu/Eu^⁎ (&gt;0.4), and (Ce/Nd)/Y (&gt;0.01), indicate high oxygen fugacity and water content, supported by the presence of magnetite, hornblende, and apatite in samples. Crystallization temperatures ranging from 726 to 835 °C and oxygen fugacity values (ΔFMQ +0.99 to +1.17) calculated from zircon trace element data fall within the typical range of intrusion-related Au deposits. Furthermore, the combination of the oxygen fugacity and whole-rock Fe content places it in the Cu field. These results demonstrate that high oxidation states and elevated water contents typically associated with primitive magmas can coexist with significant fractionation in mid-crustal, hydrous, oxidized magma chambers.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"516 ","pages":"Article 108243"},"PeriodicalIF":2.5,"publicationDate":"2025-09-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145046312","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Chemical controls on lithium mobility in granitic pegmatites: Constraints from experiments on spodumene stability","authors":"Yongchao Liu ,&nbsp;Qiang Liu ,&nbsp;Rolf L. Romer ,&nbsp;Jiankang Li","doi":"10.1016/j.lithos.2025.108242","DOIUrl":"10.1016/j.lithos.2025.108242","url":null,"abstract":"<div><div>The dependence of the stability of spodumene (LiAlSi₂O₆) on fluid composition and pegmatite-forming mineral assemblage was investigated by in situ experiments using a hydrothermal diamond-anvil cell and Raman spectroscopy at 550–700 °C and 400–750 MPa. Our results show that Li-rich weakly alkaline (pH) conditions are favorable for spodumene crystallization. Spodumene formation from Li-rich systems is suppressed by high levels of Na and/or K and, thus, is controlled by alkali activity. This implies that the formation of hydrothermal and magmatic spodumene requires earlier removal of Na and K from the fluid or melt. Experimental metasomatism shows that spodumene is susceptible to hydrothermal alteration and is readily converted to alkali feldspar in alkaline to neutral sodic/potassic hydrothermal fluids and to muscovite in acid and potassic fluids. This implies that intense post-magmatic hydrothermal overprint in open systems can completely destroy spodumene mineralization in pegmatites. The results of our study confirm earlier speculation that the alkalinity of hydrous melts or fluids has a major influence on lithium mobility in granitic pegmatites.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"516 ","pages":"Article 108242"},"PeriodicalIF":2.5,"publicationDate":"2025-09-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145019274","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":"A mineralogical perspective on the granite alkali feldspar megacrysts paradox","authors":"A. Idini ,&nbsp;D. Fancello ,&nbsp;P. Mameli ,&nbsp;S. Ferrero ,&nbsp;S. Cuccuru ,&nbsp;L. Casini","doi":"10.1016/j.lithos.2025.108229","DOIUrl":"10.1016/j.lithos.2025.108229","url":null,"abstract":"<div><div>Alkali feldspar megacrysts (commonly named K-feldspar) are a distinctive feature of many plutonic rocks. Yet, there is still no consensus on their origin. Two main contrasting explanations have been proposed so far: (i) the megacrysts form late during the crystallization history of the plutonic rock in which they occur and attain their large size in a melt-poor – even subsolidus – environment, or (ii) the megacrysts crystallize at an early stage and grow in the presence of large volumes of melt. In this article we address the applicability of these models to the alkali feldspar megacrysts of the Castellaccio Pluton (NW Sardinia, Italy). Petrographic observations and microstructural analysis of the megacrysts highlight the systematic occurrence of relict K-bearing mineral inclusions – biotite, muscovite and oligoclase – rimmed by anorthoclase and K-rich albite. We interpret these microstructures as evidence of reactions between partially assimilated K-bearing phases, likely from wall-rock, and the incoming melt. The chemical assimilation of K-bearing phases is proposed as the mechanism of K and Al enrichment necessary for the megacrysts growth.</div><div>The temperatures of the megacrysts crystallization, calculated by Ti-in-K-feldspar thermometer, are estimated at <em>c.</em> 820 ± 60 or 780 ± 60 °C, depending on the calculated TiO₂ activity in the whole rock (0.47–0.62).</div><div>Finally, the strong positive europium anomaly and enrichment in barium in the megacrysts with respect to the whole-rock compositions exclude significant plagioclase fractionation, thus supporting megacrysts formation at the early stage of the cooling history. All the results of our work point toward a magmatic origin and evolution of the K-feldspar megacrysts in the Castellaccio granite pluton.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"516 ","pages":"Article 108229"},"PeriodicalIF":2.5,"publicationDate":"2025-09-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145266345","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":"Baddeleyite containing ordered srilankite (ZrTi2O6) from Eppawala, Sri Lanka","authors":"Lutz Nasdala ,&nbsp;Gerald Giester ,&nbsp;Chutimun Chanmuang N. ,&nbsp;Christoph Hauzenberger ,&nbsp;Fabien Pascale ,&nbsp;Roberto Dovesi ,&nbsp;G.W.A. Rohan Fernando ,&nbsp;K.A. Geeth Sameera ,&nbsp;Martin Ende ,&nbsp;Gerlinde Habler","doi":"10.1016/j.lithos.2025.108230","DOIUrl":"10.1016/j.lithos.2025.108230","url":null,"abstract":"<div><div>Megacrysts of baddeleyite have been found in a (latest Neoproterozoic) carbonatite near Eppawala, Sri Lanka. The material was characterised using a combination of structural, chemical and spectroscopic analysis techniques, revealing notable internal heterogeneity. The baddeleyite contains variable, significant volume fractions affected by secondary alteration. Further detailed studies will be needed before the material can be considered as potential primary reference material in U-Pb and other isotope-analytical studies. Most remarkable, however, is the occurrence of lamellae of ordered ZrTi₂O₆ (orthorhombic space group <em>Pbcn</em> with <em>a</em> = 14.198 ± 0.002 Å, <em>b</em> = 5.326 ± 0.001 Å, <em>c</em> = 5.002 ± 0.001 Å). Single-crystal X-ray diffraction and Raman microspectroscopy results, including a calculated spectrum, are presented for the newly recognised ordered form of ZrTi₂O₆. In this phase, Zr is eight- and Ti is six-coordinated. It seems to be a hitherto unknown polymorph: So far, only disordered ZrTi₂O₆ with both Zr and Ti in octahedral sites was known to occur in nature. Revisiting known srilankite samples appears worthwhile.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"516 ","pages":"Article 108230"},"PeriodicalIF":2.5,"publicationDate":"2025-08-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144933814","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":"The behaviour of halogens in the magmatic-hydrothermal evolution of Sn-W systems and their potential as fluid source indicators","authors":"Mauro Bongiovanni ,&nbsp;Tobias Fusswinkel ,&nbsp;Michael A.W. Marks","doi":"10.1016/j.lithos.2025.108233","DOIUrl":"10.1016/j.lithos.2025.108233","url":null,"abstract":"<div><div>A regional assessment of the halogens distribution across the Sn-W mineralised Cornubian batholith is presented in this study, including a comprehensive dataset of the halogen chemistry of whole rocks, minerals and fluids.</div><div>Overall, the F content in most halogen-bearing minerals increases with progressive differentiation of the granite. On the other hand, Cl only increases during early stages of magmatic fractionation, in correspondence to the second regional pulse of magma across the region (forming G3 granite), and the successive exsolution of fluid from the melt resulted in a rapid drop in Cl content, observed in both whole rock content and halogen-bearing minerals (in particular micas and apatite).</div><div>The fluid inclusion record, covering the entire evolution from magmatic to hydrothermal conditions, shows no evident differences in terms of halogen ratios between intermediate density fluids, brines and diluted fluids. However, a significant decrease in Br/Cl and I/Cl for late magmatic and late hydrothermal samples is observed. This shift can be attributed to mixing with an external fluid relatively poor in Br and I, or to the effect of progressive fractionation, causing a decrease in both ratios according to existing experimental studies, with the latter hypothesis being preferred.</div><div>The overlap in Br/I across all samples suggest that Br and I do not significantly fractionate from each other during the magmatic-hydrothermal evolution of such granites, and behave similarly to Cl. This represents further evidence that the external fluids mixing with magmatic fluids giving rise to the Sn-W and polymetallic mineralisation across the Cornubian batholith are halogen-free and therefore have a meteoric origin.</div><div>Whole-rock leaching experiments demonstrate that Cl, Br and possibly I are for the most part not tightly-bound to minerals, but rather hosted in fluid inclusions or forming weak bonds on mineral surfaces, whereas F is obviously strongly bound in micas, apatite and tourmaline, and in very evolved granites (G5 and Gx) in fluorite and topaz.</div><div>This study shows the potential of triple halogens analysis (Cl-Br-I) in recognising fluid sources and as tracer of fluid mixing even at large scale, independently from other tracers more commonly used in the literature to discern these processes.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"516 ","pages":"Article 108233"},"PeriodicalIF":2.5,"publicationDate":"2025-08-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144997537","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":"Property and composition of fluids from the subducting oceanic slab: Constraints from multiple veins from SW Tianshan, China","authors":"Zheng-Hua Pan ,&nbsp;Ren-Xu Chen ,&nbsp;Tie-Nan Chen ,&nbsp;Zhuang-Zhuang Yin ,&nbsp;Bing Gong ,&nbsp;Xiang-Ping Zha ,&nbsp;Chuang Wang","doi":"10.1016/j.lithos.2025.108231","DOIUrl":"10.1016/j.lithos.2025.108231","url":null,"abstract":"<div><div>Fluid properties and compositions play critical roles in element mobility and crust-mantle interactions in subduction zones. Veins within high/ultrahigh-pressure metabasites record fluid flow in subduction zones. A comprehensive study combining whole-rock and mineral major and trace element contents, halogen contents and zirconology was conducted on various veins—omphacite, garnet-quartz, quartz and epidote-quartz veins—from SW Tianshan. The results are used to quantitatively reconstruct the properties and compositions of slab-derived fluids during oceanic subduction and exhumation. Omp veins formed during prograde metamorphism (1.8–2.2 GPa; 466–544 °C), whereas Grt-Qz veins formed during early exhumation (1.2–1.4 GPa; 544–621 °C; 303 ± 4 Ma). Qz veins and some Ep-Qz veins formed at ∼287 Ma during eclogite- to amphibolite-facies retrogression (∼1.0 GPa; 493–557 °C), whereas the remaining Ep-Qz veins precipitated during late exhumation (0.6–0.8 GPa; 485–521 °C; 229 ± 7 Ma). Mineral element and isotope data indicate that Omp, Grt-Qz, and Ep-Qz veins formed from aqueous fluids derived from dehydration of metamafic rocks, whereas Qz veins involved serpentinite-derived fluids. Vein-forming aqueous fluids contained 0.04–0.88 wt% F and up to 4.56 wt% Cl. High-pressure fluids forming Omp and Grt-Qz veins exhibit elevated abundances of Ca, Al, Mg, Fe, LILE, HFSE, REE and halogens compared to low-pressure fluids forming Qz and Ep-Qz veins, confirming the role of halogens in enhancing element solubility in aqueous fluids. Whole-rock F/Cl ratios of the veins positively correlate with metal ion, LREE, MREE and HFSE contents. Apatite F/Cl ratios also correlate strongly with rutile Nb/Ta ratios across all vein types. These observations suggest that halogen compositions critically control element solubility in aqueous fluids, particularly for HFSE. As halogen signatures vary in slab-derived fluids during progressive oceanic subduction, they generate distinct element mobility patterns.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"516 ","pages":"Article 108231"},"PeriodicalIF":2.5,"publicationDate":"2025-08-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144933816","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":"Boundary conditions for the petrogenesis of plagioclase ultraphyric basalts (PUB) from the northeast (NE) pacific ridge system: Constraints from plagioclase-hosted melt inclusions","authors":"Madison X. Betts ,&nbsp;Gokce K. Ustunisik ,&nbsp;Roger L. Nielsen ,&nbsp;Olivia G. Daynes","doi":"10.1016/j.lithos.2025.108232","DOIUrl":"10.1016/j.lithos.2025.108232","url":null,"abstract":"<div><div>The crystal cargo in plagioclase ultraphyric basalts (PUB) together with their melt inclusions (MI) record changes in the major, trace, and isotopic compositions of magmas as they evolve. That geochemical signature provides evidence for the identity and relative significance of the igneous processes such as fractionation, mixing, assimilation, and degassing that modify their host magmas during transport from the melting regime to the surface. This investigation focuses on a case study quantifying the relative roles of these processes active globally at mid-ocean ridges (MOR) based on data collected from plagioclase megacrysts and their homogenized MI from a set of PUB lavas sampled at Blanco Fracture Zone (BFZ), Gorda Ridge, and Endeavor segment of Juan de Fuca (JdF) Ridge in the Northeast (NE) Pacific Ridge system. We combine results for major element phase equilibria calculations based on the MELTS algorithm and apply the major element chemistry, including phase proportions and compositions, to estimate the impact of fractional crystallization and partial melting in the generation and differentiation of these PUB lavas. Our results, in the form of a set of simulations that are based on a range of conditions, enclose the MI, megacryst, and associated lava data and suggest that much of the compositional variation exhibited can be bracketed by 8–20 % incremental batch melting of a heterogeneous mantle protolith, followed by a combined 65–75 % polybaric and isobaric fractional crystallization during ascent. Therefore, only 25–35 % of magma generated in the melting regime survive as liquids to be erupted as lavas.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"516 ","pages":"Article 108232"},"PeriodicalIF":2.5,"publicationDate":"2025-08-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144989536","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}