Contributions to Mineralogy and Petrology最新文献

{"title":"Petrogenesis of volcanic rocks from the Quaternary Eifel volcanic fields, Germany: detailed insights from combined trace-element and Sr–Nd–Hf–Pb–Os isotope data","authors":"Mike W. Jansen, Carsten Münker, Josua J. Pakulla, Eric Hasenstab-Dübeler, Christian S. Marien, Toni Schulz, Maria Kirchenbaur, Kathrin P. Schneider, Robin Tordy, Vera Schmitt, Frank Wombacher","doi":"10.1007/s00410-024-02137-w","DOIUrl":"10.1007/s00410-024-02137-w","url":null,"abstract":"<div><p>Quaternary rocks from the East and West Eifel volcanic fields in western Germany are a key suite of intraplate volcanic rocks that can provide insights into volcanism of the Central European Volcanic Province (CEVP) and into continental intraplate volcanism in general. We present a comprehensive dataset for Eifel lavas including isotope as well as major and trace element data for 59 samples covering representative compositions of the different volcanic fields. In line with previous studies, the lavas are all SiO<sub>2</sub>-undersaturated, alkaline-rich and mainly comprise primitive basanites, melilitites, and nephelinites (Mg# ≥ 57). Geochemical compositions of samples from both volcanic subfields display distinct differences in their trace-element as well as radiogenic isotope compositions, largely confirming previous subdivisions. Coupled trace-element and radiogenic Sr–Nd–Hf–Pb–Os isotope compositions can now provide firm evidence for spatially heterogeneous mantle sources and compositionally distinct magmatic pulses. Within the West Eifel Field, Sr–Nd–Pb isotope compositions of the younger (≤80 ka), ONB-suite (olivine-nephelinite-basanite) are similar to FOZO (FOcal ZOne) or the EAR (European Asthenospheric Reservoir) and resemble compositions that have been previously reported from plume-sourced ocean island basalts (OIB). In marked difference, older (700 Ma to 80 ka) volcanic rocks from the F-suite (Foidite) in the West Eifel field and from the entire east Eifel Field tap a more enriched mantle component, as illustrated by more radiogenic Sr isotope (<sup>86</sup>Sr/<sup>87</sup>Sr up to 0.705408) and variable Pb isotope compositions (<sup>206</sup>Pb/<sup>204</sup>Pb = 18.61–19.70, <sup>207</sup>Pb/<sup>204</sup>Pb = 15.62–15.67 and <sup>208</sup>Pb/<sup>204</sup>Pb = 38.89–39.76). Combined trace-element compositions of ONB-suite samples are in good agreement with results from batch melting models suggesting a hybrid composition of Eifel magmas formed through mixing 10% of a FOZO-like melt with 90% of a DMM-like melt, similar to melts from the Tertiary HEVF. However, radiogenic Sr–Nd–Pb isotope compositions of F-suite and EEVF and some ONB lavas require the admixture of melts from lithospheric mantle sources. Elevated Nb/Ta and Lu/Hf ratios in combination with variable <sup>187</sup>Os/<sup>188</sup>Os ratios can now demonstrate the presence of residual carbonated eclogite components, either in the lithosphere or in the asthenospheric mantle. Finally, by combining geochemical and temporal constraints of Tertiary and Quaternary volcanism it becomes evident that CEVP volcanism in central and western Germany has resulted from compositionally distinct magmatic pulses that tap separate mantle sources. Although the presence of a mantle plume can neither be fully confirmed nor excluded, plume-like melt pulses which partially tap carbonated eclogite domains that interact to variable extents with the lithosphere provide a viable explanatio","PeriodicalId":526,"journal":{"name":"Contributions to Mineralogy and Petrology","volume":"179 6","pages":""},"PeriodicalIF":3.5,"publicationDate":"2024-05-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11081932/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140911022","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":"Petrologically controlled oxygen isotopic classification of cogenetic magmatic and metamorphic sapphire from Quaternary volcanic fields in the Eifel, Germany","authors":"Sebastian Schmidt,&nbsp;Andreas Hertwig,&nbsp;Katharina Cionoiu,&nbsp;Christof Schäfer,&nbsp;Axel K. Schmitt","doi":"10.1007/s00410-024-02136-x","DOIUrl":"10.1007/s00410-024-02136-x","url":null,"abstract":"<div><p>Gem sapphire is commonly retrieved from primary and secondary deposits associated with alkali basaltic fields, but its source rocks are rarely preserved. The Eifel (Rhenish Massif, western Germany), although not producing gem sapphire, shares many petrologic and geochemical similarities with such fields worldwide. Due to the young age of volcanic deposits and active quarrying, sapphire-bearing rocks are readily accessible, along with detrital sapphire from modern sediments. Here, oxygen isotope and trace element compositions are reported for 223 sapphire grains, and rutile and zircon inclusions in sapphire were dated indicating crystallization synchronous with Paleogene–Quaternary volcanism. Endmembers in δ¹⁸O range are sapphires from syenites representing mantle-derived differentiated melts with minor crustal contamination (~4–6‰) and contact metamorphic mica schists (&gt;10‰) as purely crustal source rocks. Intermediate values between ~6 and 10‰ require variable degrees of mantle-crust hybridization. Lower crustal granulite sources are dismissed based on their oxygen isotopic compositions being lower than most sapphire crystals. Diffusion modelling of sharp oxygen isotopic zonation in compositionally zoned crystals precludes crystal residence at &gt;900 °C over the lifetime of evolved magma reservoirs in the Eifel (c. 50 ka). This argues against direct mantle or lower crustal sapphire origins. Instead, low temperature residence is consistent with sharp δ¹⁸O gradients, coexisting andalusite, and fluid inclusion barometry. Hence, Eifel sapphire crystallization is attributed to contact metamorphic aureoles around upper crustal (5–7 km) magma bodies where phonolite, trachyte, and carbonatite melts differentiated from mafic parental magmas, and reacted with metasedimentary wall rocks.</p></div>","PeriodicalId":526,"journal":{"name":"Contributions to Mineralogy and Petrology","volume":"179 6","pages":""},"PeriodicalIF":3.5,"publicationDate":"2024-05-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00410-024-02136-x.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140942301","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":"A multi-methodological approach to record dynamics and timescales of the plumbing system of Zaro (Ischia Island, Italy)","authors":"Carlo Pelullo,&nbsp;Sumit Chakraborty,&nbsp;Chiara Paola Montagna,&nbsp;Ilenia Arienzo,&nbsp;Richard James Brown,&nbsp;Massimo D’Antonio,&nbsp;Sandro de Vita,&nbsp;Claudia D’Oriano,&nbsp;Manuela Nazzari,&nbsp;Lucia Pappalardo,&nbsp;Paola Petrosino","doi":"10.1007/s00410-024-02138-9","DOIUrl":"10.1007/s00410-024-02138-9","url":null,"abstract":"<div><p>Determining the time spans of processes related to the assembly of eruptible magma at active volcanoes is fundamental to understand magma chamber dynamics and assess volcanic hazard. This information can be recorded in the chemical zoning of crystals. Nevertheless, this kind of study is still poorly employed for the active volcanoes of the Neapolitan area (Southern Italy), in particular, for Ischia island where the risk is extremely high and this information can provide the basis for probabilistic volcanic hazard assessment. For these reasons, we acquired chemical composition on clinopyroxene crystals erupted at Ischia during the Zaro eruption (6.6 ± 2.2 ka) and performed numerical simulations of the input of mafic magma into a trachytic reservoir, in order to investigate various aspects of pre-eruptive dynamics occurring at different timescales. This event emplaced a ~ 0.1 km³ lava complex, in which the main trachytic lava flows host abundant mafic to felsic enclaves. Previous petrological investigation suggested that mafic magma(s) mixed/mingled with a trachytic one, before the eruption. In this work, the clinopyroxene zoning patterns depict the growth of crystals in different magmatic environments, recording sequential changes occurred in the plumbing system before the eruption. The evolution of the plumbing system involved a hierarchy of timescales: <i>a few hours</i> for magma mingling caused by mafic recharge(s) and likely occurred multiple times over <i>a decade</i> during which a dominant magmatic environment was sustained before the eruption. Such timescales must be considered in volcanic hazard assessment at Ischia and similar active volcanoes in densely populated areas.</p></div>","PeriodicalId":526,"journal":{"name":"Contributions to Mineralogy and Petrology","volume":"179 5","pages":""},"PeriodicalIF":3.5,"publicationDate":"2024-05-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00410-024-02138-9.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140886032","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":"Dynamics of the oceanic dike–gabbro transition revealed by petrology and geochemistry of the Yunzhug ophiolite, central Tibet","authors":"Tong Liu,&nbsp;Chuan-Zhou Liu,&nbsp;Zhen-Yu Zhang,&nbsp;Wei-Qi Zhang,&nbsp;Wen-Bin Ji,&nbsp;Chang Zhang,&nbsp;Ross N. Mitchell","doi":"10.1007/s00410-024-02135-y","DOIUrl":"10.1007/s00410-024-02135-y","url":null,"abstract":"<div><p>The dynamics and magma transport at the boundary between the upper and lower oceanic crusts (i.e., the dike–gabbro transition) are crucial for understanding the crustal accretion beneath mid-ocean ridges, which however have been studied at quite a few sites such as the East Pacific Rise and ophiolites like Troodos and Oman. Here we present detailed geological, petrological, and geochemical data for the dike–gabbro transition and associated basalts in the Yunzhug ophiolite, central Tibet, to constrain the complex magmatic processes in this specific horizon. The Yunzhug ophiolite contains a large (~ 20 km²) well-exposed sheeted dike complex, which is rooted in a dike–gabbro transition that consists of diverse lithologies, including diabase, gabbro, and minor porphyritic diabase. Petrographically, the Yunzhug gabbros could be grouped into the dominant Plg (plagioclase)-euhedral gabbros (euhedral–subhedral plagioclases enclosed in clinopyroxene oikocrysts) and a small amount of Cpx (clinopyroxene)-euhedral gabbros (with abundant euhedral clinopyroxenes). Plagioclases and their equilibrated melts of the two types of gabbros are similar, whereas clinopyroxenes and their equilibrated melts of the Cpx-euhedral gabbros are more primary and depleted than those of the Plg-euhedral gabbros. These petrographic and geochemical features suggest an earlier crystallization of clinopyroxene for the Cpx-euhedral gabbros, which is best explained by occasional water input in the magmatic system. Nevertheless, the modeled equilibrated melts of the two types of gabbros have compositions indistinguishable from the whole rock compositions of diabases and basalts, indicating a direct genetic linkage between these rocks. The unusual porphyritic diabases, on the other hand, provide evidence supporting for plagioclase accumulation and aggregation during magma upward migration, thus may have served as a unique way for magma to transport from the lower to upper crust. Studies of the Yunzhug ophiolite thus provide some key constraints on the complex magmatic processes in the oceanic dike–gabbro transition, regarding its dynamic accretion and magmatic plumbing mechanisms.</p></div>","PeriodicalId":526,"journal":{"name":"Contributions to Mineralogy and Petrology","volume":"179 5","pages":""},"PeriodicalIF":3.5,"publicationDate":"2024-05-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140836403","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 effect of potassium on aluminous phase stability in the lower mantle","authors":"Elena-Marie Rogmann,&nbsp;Eleanor S. Jennings,&nbsp;Jennifer Ross,&nbsp;Nobuyoshi Miyajima,&nbsp;Michael J. Walter,&nbsp;Simon C. Kohn,&nbsp;Oliver T. Lord","doi":"10.1007/s00410-024-02129-w","DOIUrl":"10.1007/s00410-024-02129-w","url":null,"abstract":"<div><p>The aluminous calcium-ferrite type phase (CF) and new aluminous phase (NAL) are thought to hold the excess alumina produced by the decomposition of garnet in MORB compositions in the lower mantle. The respective stabilities of CF and NAL in the nepheline-spinel binary (NaAlSiO<span>(_{4})</span>–MgAl<span>(_{2})</span>O<span>(_{4})</span>) are well established. However with the addition of further components the phase relations at lower mantle conditions remain unclear. Here we investigate a range of compositions around the nepheline apex of the nepheline-kalsilite-spinel compositional join (NaAlSiO<span>(_{4})</span>–KAlSiO<span>(_{4})</span>–MgAl<span>(_{2})</span>O<span>(_{4})</span>) at 28–78 GPa and 2000 K. Our experiments indicate that even small amounts of a kalsilite (KAlSiO<span>(_{4})</span>) component dramatically impact phase relations. We find NAL to be stable up to at least 71 GPa in potassium-bearing compositions. This demonstrates the stabilizing effect of potassium on NAL, because NAL is not observed at pressures above 48 GPa on the nepheline-spinel binary. We also observe a broadening of the CF stability field to incorporate larger amounts of potassium with increasing pressure. For pressures below 50 GPa only minor amounts (<span>(&lt;0.011(1)frac{K}{K+Na+Mg})</span>) of potassium are soluble in CF, whereas at 68 GPa, we find a solubility in CF of at least <span>(0.088(3)frac{K}{K+Na+Mg})</span>. This indicates that CF and NAL are suitable hosts of the alkali content of MORB compositions at lower mantle conditions. For sedimentary compositions at lower mantle pressures, we expect K-Hollandite to be stable in addition to CF and NAL for pressures of 28–48 GPa, based on our simplified compositions.</p></div>","PeriodicalId":526,"journal":{"name":"Contributions to Mineralogy and Petrology","volume":"179 5","pages":""},"PeriodicalIF":3.5,"publicationDate":"2024-04-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00410-024-02129-w.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140651948","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":"Compositional evolution of slab-derived fluids during ascent: implications from trace-element partition between hydrous melts and Cl-free or Cl-rich aqueous fluids","authors":"Hajime Taniuchi,&nbsp;Tatsuhiko Kawamoto,&nbsp;Takayuki Nakatani,&nbsp;Osamu Ishizuka,&nbsp;Toshihiro Suzuki,&nbsp;Akihiko Tomiya","doi":"10.1007/s00410-024-02122-3","DOIUrl":"10.1007/s00410-024-02122-3","url":null,"abstract":"<div><p>Slab-derived supercritical liquids separate into aqueous fluids and hydrous melts during their migration. Separated aqueous fluids further release melt components that cannot be dissolved during ascent. During these processes, elemental partitioning occurs, which may contribute to the geochemical evolution of subduction-zone fluids. Here, we report new experimental results of partition coefficients between a hydrous dacitic melt and Cl-free or Cl-rich aqueous fluids (D^fluid/melt) for 26 elements at a temperature of 1100°C and pressures of 0.3 and 0.7 GPa using internally-heated pressure vessels. Our results reveal that high-field strength elements (HFSE), except Th, are hardly partitioned into aqueous fluids, regardless of their salinity and pressure conditions. In contrast, the partitioning of other elements varies depending on the fluid salinity. D^fluid/melt of large-ion lithophile elements (LILE) and U increases with salinity, whereas that of rare earth elements (REE) and Th decreases. These results predict that slab-derived aqueous fluids can evolve to become richer in LILE and U and poorer in HFSE and REE by separating melt components, which explains the LILE- and U-rich and HFSE- and REE-poor characteristics of subduction-zone magmas. This also explains the higher LILE/HFSE and LILE/REE ratios in frontal-arc basalts than in rear-arc basalts: frontal-arc basalts can be generated by the addition of aqueous fluids that sufficiently separate the melt components at shallower depths, whereas rear-arc basalts are generated by the addition of supercritical liquids or aqueous fluid that insufficiently separate the melt components at greater depths. Such separation of melt components from ascending slab-derived fluid can determine the geochemical signature and across-arc compositional variation of subduction-zone magmas.</p></div>","PeriodicalId":526,"journal":{"name":"Contributions to Mineralogy and Petrology","volume":"179 5","pages":""},"PeriodicalIF":3.5,"publicationDate":"2024-04-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140652652","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":"Trace-element mobility in pelite-derived supercritical fluid-melt at subduction-zone conditions","authors":"A. G. Sokol,&nbsp;O. A. Kozmenko,&nbsp;A. N. Kruk,&nbsp;S. Y. Skuzovatov,&nbsp;D. V. Kiseleva","doi":"10.1007/s00410-024-02131-2","DOIUrl":"10.1007/s00410-024-02131-2","url":null,"abstract":"<div><p>The mobility of trace elements in supercritical fluid-melt derived from pelite rich in volatiles has been studied experimentally at pressures from 3.0 to 7.8 GPa and temperatures from 750 to 1090 °С using the diamond trap method. The experiments simulate the conditions of warm and hot subduction, in which pelite either retains the whole inventory of volatiles or releases a fluid in three successive devolatilization steps. The 3.0 GPa and 750 °С runs with pelite rich in volatiles yield a supercritical fluid (SCF) which attains equilibrium with an eclogitic residue bearing phengite and accessory rutile, zircon, and monazite. At ≥5.5 GPa and ≥850 °С, above the second critical endpoint, the SCF transforms into a supercritical fluid-melt (SCFM) which acquires higher concentrations of almost all incompatible trace elements while the mineral assemblage of the equilibrium eclogitic residue remains the same but lacks monazite. The trace-element enrichment of SCFM is most prominent for Ba, Sr, LREE, Th, and U. At the hot subduction conditions, the fluid-melt likewise contains more K, Rb, Zr, and Hf, though LREE contents become lower. The negative Nb anomaly persists in all cases. SCFM has its trace-element composition generally similar to that of hydrous melt derived from oceanic sediments, but contains more REEs and water. Partitioning of LILE, HFSE, and LREE between the SCFM and residue phases mainly depends on the fluid-melt fraction and stability of host phengite, monazite, zircon, and rutile. Thus, sediment-derived SCFM can carry both fluid-mobile and sediment-melt elements to regions of arc- and back-arc magma generation and can translate the negative Nb anomaly inherited from sediment into the magmas. Early devolatilization of pelite increases the stability of monazite and phengite in the residue and provides efficient LREE, K and Rb transport to the mantle depths of ~ 250 km. Effective LREE and Th depletion of UHP metamorphic rocks is possible by SCFM release near peak metamorphic conditions.</p></div>","PeriodicalId":526,"journal":{"name":"Contributions to Mineralogy and Petrology","volume":"179 5","pages":""},"PeriodicalIF":3.5,"publicationDate":"2024-04-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140657582","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":"Remobilization and enrichment of Nb during magmatic and hydrothermal processes: insights from titanite in Nb-rich dyke swarms of South Qinling, China","authors":"Yuxiang Zhu,&nbsp;Lianxun Wang,&nbsp;Yuanming Pan,&nbsp;Changqian Ma,&nbsp;Zhenbing She","doi":"10.1007/s00410-024-02120-5","DOIUrl":"10.1007/s00410-024-02120-5","url":null,"abstract":"&lt;div&gt;&lt;p&gt;Giant Nb deposits hosted by alkaline igneous rocks worldwide are characterized by hydrothermal and/or metamorphic modifications after magmatic crystallization. However, the impact of secondary processes on Nb mineralization in alkaline igneous rocks remains controversial. In this study, U–Pb ages, elemental, and Nd isotope compositions of titanite from a series of Nb-rich dyke swarms in the Ziyang region of South Qinling (China) have been investigated to unveil Nb remobilization and enrichment histories during magmatic and hydrothermal processes. Three types of titanite are documented: magmatic, deuteric, and hydrothermal. The magmatic titanite (Ttn I) grains are euhedral wedge-shaped, while the deuteric type (Ttn II) occurs as coronas on magmatic ilmenite. The hydrothermal titanite (Ttn III) occurs as either bead-like clusters within the cleavage planes of chloritized biotite or as anhedral grains (lesser than 200 &lt;i&gt;μ&lt;/i&gt;m in diameter) coexisting with hydrothermal actinolite, chlorite, fluorite, and/or REE-rich oxides. The magmatic titanite grains from the most primitive igneous rocks have U–Pb ages of 455 ± 25 Ma and are characterized by high levels of Nb&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;5&lt;/sub&gt; (up to 1.4 wt%) and other high field strength elements (HFSE, up to 1.3 wt% ZrO&lt;sub&gt;2&lt;/sub&gt;), rare earth elements (REE), and V, and high mean crystallization temperatures (880 ± 40 °C), suggesting that they nucleated and crystallized in a high-&lt;i&gt;T&lt;/i&gt; and Nb-rich alkaline magma during the Early Paleozoic. The gradual decrease in V, Sr, and Ba in Ttn I from mafic to intermediate dykes exemplifies the role of fractionation on magmatic enrichment of Nb (mean of 170 ppm and 7300 ppm for Ttn I in mafic and intermediate dykes, respectively) and other incompatible elements (e.g., Ta, Zr, Hf, Sn, Y, and REE) in the residual melt. The deuteric and hydrothermal types of titanites in each lithology have lower concentrations of HFSE (e.g., Nb mean of 140 ppm and 860 ppm for Ttn II in mafic and intermediate dykes, respectively), Sn, LREE, and Y but higher Al, F, V, Sr, and HREE contents than their magmatic counterpart. The deuteric and hydrothermal types of titanite have U–Pb ages of 420 ± 25 Ma and 232 ± 49 Ma, respectively, supporting two distinct hydrothermal events at Ziyang. The magmatic and deuteric types of titanite have similar ranges of εNd(t) values (+ 1.4 to + 3.5 and + 2 to + 4.2, respectively), indicative of a common source for these two generations. The hydrothermal titanite also has comparable εNd(t) values (+ 0.8 to + 2.7) to the magmatic and deuteric types, indicating a minimal external contribution to Nd (and by analogy Nb as well) from the late hydrothermal fluids. The deuteric and late hydrothermal F-rich fluids in Ziyang dyke swarms both remobilized the dispersed Nb in magmatic ilmenite, amphibole, and biotite to form secondary titanite (Ttn II, III), which is beneficial to the metallurgical extraction of this critical metal. Therefore, both magmatic ","PeriodicalId":526,"journal":{"name":"Contributions to Mineralogy and Petrology","volume":"179 5","pages":""},"PeriodicalIF":3.5,"publicationDate":"2024-04-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140677061","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":"Multi-stage ultrahigh temperature metamorphism in the lower crust of the Kaapvaal craton recorded by U–Pb ages of garnet","authors":"Q. Shu,&nbsp;A. Beranoaguirre,&nbsp;R. Albert,&nbsp;L. J. Millonig,&nbsp;J. B. Walters,&nbsp;H. R. Marschall,&nbsp;A. Gerdes,&nbsp;H. E. Hoefer,&nbsp;D. Hezel,&nbsp;G. P. Brey","doi":"10.1007/s00410-024-02121-4","DOIUrl":"10.1007/s00410-024-02121-4","url":null,"abstract":"<div><p>U–Pb ages were determined by split-stream LA-SF/MC-ICPMS in garnets from UHT granulite xenoliths (Star mine, South Africa; 124 Ma). They give a considerable age range of 400 million years with well-defined maximas at 3.09, 3.01 and 2.75 Ga. The oldest peak overlaps with the changeover from tonalites to K-granites at 3.14–3.04 Ga and with zircon ages of the mid-crustal granulites of the Vredefort dome (3.1 Ga) in the wake of the 3.2 Ga collision of three terrains that compose the Witwatersrand block. Subduction (or sagduction) of the uppermost crust in an ultrahot orogen setting brought shales and greenstones to the lower crust. Ultrahigh temperature (UHT) conditions are the result of high mantle potential temperatures and self- heating by the radioactive inventory of the subducted lithologies. Metamorphism, anatexis to very high degrees and melt extraction left UHT granulites as residue. Rejuvenation of UHT conditions was brought about by Dominion Group magmatism between 3.0 and 2.95 Ga. Magmatic uprise caused intense shearing in the lower crust followed by recrystallisation of the shear zones to generate the younger garnet age group. Ventersdorp flood basalt volcanism caused similar processes at around 2.72 Ga and generated the third garnet age group. Zircon gives U–Pb ages mainly around 2.72 Ga (both literature and our own data) i.e. zircon adjusted or newly crystallized at the youngest UHT event. Only few zircon grains retained older ages up to 2.94 Ga. Still unconstrained, but very high closure temperatures (≥ 1100 °C) for the U–Pb system in garnet keep the memory of the oldest ages in UHT granulites. Such ages can only be reset by recrystallization. This way, garnet records a prolonged high-temperature history of the lower crust of the Kaapvaal craton.</p></div>","PeriodicalId":526,"journal":{"name":"Contributions to Mineralogy and Petrology","volume":"179 5","pages":""},"PeriodicalIF":3.5,"publicationDate":"2024-04-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00410-024-02121-4.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140673097","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":"Geochemistry and volatile contents of olivine-hosted melt inclusions from Mt. Etna tholeiitic and alkaline magmatism","authors":"P. P. Giacomoni,&nbsp;M. Masotta,&nbsp;G. Delpech,&nbsp;G. Lanzafame,&nbsp;C. Ferlito,&nbsp;J. Villeneuve,&nbsp;M. Coltorti","doi":"10.1007/s00410-024-02116-1","DOIUrl":"10.1007/s00410-024-02116-1","url":null,"abstract":"<div><p>The analysis of olivine-hosted melt inclusions (MIs) from the whole sub-alkaline and alkaline magmatic suites of Mt. Etna provides fundamental information about the composition of undifferentiated magmas and their pristine volatile content. Olivine crystals (Fo_88-66) were selected for Secondary Ion Mass Spectrometry (SIMS) analysis of volatile species (H₂O, CO₂, F, Cl and S) contained in their host MIs, after preliminary high-pressure/high-temperature re-homogenization, which allowed to reduce the developing of cracks in the host olivine and diffusion-driven outgassing of volatiles from the melt inclusions. This permitted to explore the compositional variability of volatiles of undifferentiated melts and the degassing behavior through the feeding system. The studied MIs show significant major elements compositional heterogeneities (44.57–52.37 wt% SiO₂; 3.60–7.51 wt% Na₂O + K₂O). Fractionation modelling was performed with Rhyolite-MELTs under variable <i>f</i>O₂ regimes (∆FMQ + 1.5 to + 3), starting from the less evolved MIs compositions and ultimately reproducing most of the observed compositional trends. Mantle melting modelling was used to replicate the observed MIs composition, starting from a spinel-lherzolitic source, accounting for the alkalinity and Fe content of reproduced melts by varying the eutectic contribution of Amph/Phlog and Opx/Cpx respectively. Although most of the studied MIs were degassed in an open-conduit regime, the observed range of volatile concentration in MIs (2.42–6.14 wt% H₂O; 308–8474 ppm CO₂; 132–697 ppm F; 221–1766 ppm Cl and 16–1992 ppm S) is correlated with a slight decrease in the molar H₂O/(H₂O + CO₂) ratio from early tholeiites to the recent 2015 alkaline products. This observation allows to estimate a minimum 12,250 ppm CO₂ and a maximum of 6.14 wt% H₂O in primary melts of the current activity.</p></div>","PeriodicalId":526,"journal":{"name":"Contributions to Mineralogy and Petrology","volume":"179 5","pages":""},"PeriodicalIF":3.5,"publicationDate":"2024-04-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00410-024-02116-1.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140675679","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}