Contributions to Mineralogy and Petrology最新文献

{"title":"Brittle initiation of dissolution–precipitation creep in plagioclase-rich rocks: insights from the Bergen arcs, Norway","authors":"Jo Moore,&nbsp;Sandra Piazolo,&nbsp;Andreas Beinlich,&nbsp;Håkon Austrheim,&nbsp;Andrew Putnis","doi":"10.1007/s00410-024-02141-0","DOIUrl":"10.1007/s00410-024-02141-0","url":null,"abstract":"<div><p>The initiation of ductile shear zones commonly occurs spatially associated with fluid-rock reactions along brittle precursors. In many cases the relative timing of fracturing, fluid infiltration, reaction, and recrystallisation is unclear, making it difficult to disentangle mechanisms of shear zone initiation from subsequent deformation and recrystallisation. Here we present the study of the transition from a dry plagioclase-diopside-garnet-scapolite host granulite-facies lithology to (1) a low strain amphibolite-facies rock, and (2) a transition from low strain to high strain amphibolite-facies lithologies. Hydration of the granulite-facies precursor at amphibolite-facies conditions produces an assemblage comprised dominantly of plagioclase-amphibole-zoisite-clinozoisite-kyanite-scapolite-quartz. Detailed study of plagioclase chemistry and microstructures across these two transitions using Electron Backscatter Diffraction (EBSD) and Wavelength Dispersive Spectrometry (WDS) allows us to assess the degree of coupling between deformation and fluid-rock reaction across the outcrop. Plagioclase behaves dominantly in a brittle manner at the hydration interface and so the initial weakening of the rock is attributed to grain size reduction caused by fracture damage and fluid infiltration at amphibolite-facies conditions. Extensive fracturing-induced grain size reduction locally increases permeability and allows for continuing plagioclase and secondary mineral growth during shear. Based on plagioclase microstructures, such as, an inherited but dispersed crystallographic preferred orientation (CPO), truncation of chemical zoning, and the dominance of fine (5–150 µm), slightly elongate, polygonal grains we conclude that deformation is dominantly facilitated by dissolution–precipitation creep assisted by grain boundary sliding in the shear zone.</p></div>","PeriodicalId":526,"journal":{"name":"Contributions to Mineralogy and Petrology","volume":"179 6","pages":""},"PeriodicalIF":3.5,"publicationDate":"2024-05-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00410-024-02141-0.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141148022","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":"Laser ablation (in situ) Lu-Hf geochronology of epidote group minerals","authors":"Jie Yu,&nbsp;Stijn Glorie,&nbsp;Martin Hand,&nbsp;Alexander Simpson,&nbsp;Sarah Gilbert,&nbsp;Kristoffer Szilas,&nbsp;Nick Roberts,&nbsp;Mark Pawley,&nbsp;Yanbo Cheng","doi":"10.1007/s00410-024-02143-y","DOIUrl":"10.1007/s00410-024-02143-y","url":null,"abstract":"<div><p>Epidote group minerals, including allanite, clinozoisite and epidote are common in a range of metamorphic, igneous and hydrothermal systems, and are stable across a wide range of pressure<i>–</i>temperature (<i>P–T</i>) conditions. These minerals can incorporate substantial amounts of rare earth elements (REEs) during their crystallisation, making them potential candidates for Lu–Hf geochronology to provide age constraints on various geological processes. Here we report on a first exploration into the feasibility of in situ Lu–Hf geochronology for epidote group minerals from various geological settings and compare the results with age constraints from other geochronometers. Magmatic allanite samples from pegmatites and monzogranites in the Greenland anorthosite complex, Coompana Province and Qingling Orogen provided dates consistent with magmatic events spanning from c. 2660 to 1171 Ma. In the Qingling pegmatites, a younger phase of hydrothermal allanite was dated at c. 215 Ma, consistent with the timing of regional REE mineralisation. Allanite from the Yambah Shear Zone, Strangways Metamorphic Complex, yielded Lu–Hf age of c. 430 Ma. It predates the garnet and apatite growth at c. 380 Ma, suggesting the Lu–Hf system can be preserved in allanite during prograde amphibolite-facies metamorphism. Additionally, Lu–Hf dates for hydrothermal clinozoisite and epidote are consistent with the timing of hydrothermal alteration and mineralisation in a range of settings, demonstrating the utility of the technique for mineral exploration. Despite the current lack of matrix-matched reference materials, the successful application of laser ablation Lu–Hf geochronology to epidote group minerals offers valuable geochronological insights into various geological processes that can be difficult to access through other geochronometers.</p></div>","PeriodicalId":526,"journal":{"name":"Contributions to Mineralogy and Petrology","volume":"179 6","pages":""},"PeriodicalIF":3.5,"publicationDate":"2024-05-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00410-024-02143-y.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141148102","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":"Stressful crystal histories recorded around melt inclusions in volcanic quartz","authors":"Tyler Cadena,&nbsp;Michael Manga,&nbsp;Kenneth Befus,&nbsp;Nobumichi Tamura","doi":"10.1007/s00410-024-02126-z","DOIUrl":"10.1007/s00410-024-02126-z","url":null,"abstract":"<div><p>Magma ascent and eruption are driven by a set of internally and externally generated stresses that act upon the magma. We present microstructural maps around melt inclusions in quartz crystals from six large rhyolitic eruptions using synchrotron Laue X-ray microdiffraction to quantify elastic residual strain and stress. We measure plastic strain using average diffraction peak width and lattice misorientation, highlighting dislocations and subgrain boundaries. Quartz crystals across studied magma systems preserve similar and relatively small magnitudes of elastic residual stress (mean 53–135 MPa, median 46–116 MPa) in comparison to the strength of quartz (~ 10 GPa). However, the distribution of strain in the lattice around inclusions varies between samples. We hypothesize that dislocation and twin systems may be established during compaction of crystal-rich magma, which affects the magnitude and distribution of preserved elastic strains. Given the lack of stress-free haloes around faceted inclusions, we conclude that most residual strain and stress was imparted after inclusion faceting. Fragmentation may be one of the final strain events that superimposes stresses of ~ 100 MPa across all studied crystals. Overall, volcanic quartz crystals preserve complex, overprinted deformation textures indicating that quartz crystals have prolonged deformation histories throughout storage, fragmentation, and eruption.</p></div>","PeriodicalId":526,"journal":{"name":"Contributions to Mineralogy and Petrology","volume":"179 6","pages":""},"PeriodicalIF":3.5,"publicationDate":"2024-05-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00410-024-02126-z.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141148075","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":"Melt inclusions in zircon: a window to understanding the structure and evolution of the magmatic system beneath the Laguna del Maule volcanic field","authors":"Kei Shimizu,&nbsp;Tyler B. Blum,&nbsp;Chloe E. Bonamici,&nbsp;John H. Fournelle,&nbsp;Christine E. Jilly-Rehak,&nbsp;Noriko T. Kita,&nbsp;Kouki Kitajima,&nbsp;Jacob D. Klug,&nbsp;Will O. Nachlas,&nbsp;Brad S. Singer,&nbsp;Michael J. Spicuzza,&nbsp;Alexander V. Sobolev,&nbsp;Bryan A. Wathen,&nbsp;John W. Valley","doi":"10.1007/s00410-024-02133-0","DOIUrl":"10.1007/s00410-024-02133-0","url":null,"abstract":"<div><p>Explosive silicic eruptions pose a significant threat to society, yet the development and destabilization of the underlying silicic magmatic systems are still controversial. Zircons provide simultaneous information on the trace element composition and age of silicic magmatic systems, while melt inclusions in quartz and plagioclase yield important constraints on their volatile content as well as magma storage depth. Melt inclusions in zircons (MIZs) combine these data from a single mineral grain, recording the age, storage depth, temperature, and composition of magmas, and thus provide unique constraints on the structure and evolution of silicic magmatic systems. We studied MIZs from the Laguna del Maule (LdM) volcanic field in the southern Andes that is among the most active Pleistocene-Holocene rhyolitic volcanic centers worldwide and a potentially hazardous system displaying inflation rates in excess of 25 cm/yr. The host zircon ages suggest that the LdM MIZ record extends to ~ 30 kyr before eruption, in contrast to the melt inclusions in LdM plagioclase and quartz crystals that formed only decades to centuries before eruption. The major element compositions of MIZs are minimally affected by post-entrapment crystallization, and agree well with the LdM rhyolitic whole rock data. The MIZs record long-term differences in zircon-saturated melt composition between two eruptive units (rdm: Rhyolite of the Laguna del Maule vs. rle: Rhyolite of Los Espejos). The more evolved major element composition of rle MIZs than rdm MIZs, suggests a long-term deeper connection of the rdm crystal mush to a more primitive magma body than that of the rle. The evidence of slow H diffusion observed in MIZs suggest that their H₂O contents are not significantly affected by diffusion of H through the host zircon. The magma storage pressures of 1.1 to 2.8 kbars recorded by the H₂O contents of rdm and rle MIZs are consistent with the optimal emplacement window (2.0 ± 0.5 kbar) of silicic magma reservoir growth, storage, and eruptibility based on thermomechanical modeling (Huber et al. 2019).</p></div>","PeriodicalId":526,"journal":{"name":"Contributions to Mineralogy and Petrology","volume":"179 6","pages":""},"PeriodicalIF":3.5,"publicationDate":"2024-05-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140968904","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":"Experimental insights into the mineralogy and melt-rock reactions produced by lunar cumulate mantle overturn","authors":"J. L. Scholpp,&nbsp;N. Dygert","doi":"10.1007/s00410-024-02134-z","DOIUrl":"10.1007/s00410-024-02134-z","url":null,"abstract":"<div><p>Hybridization of the lunar mantle during the overturn (sinking) of Fe- and Ti–rich ilmenite-bearing clinopyroxenite cumulates (IBC) in the lunar interior is called upon to explain the high TiO₂ abundances of lunar basalts. Chemical reactions that occur after juxtaposition of IBC and mantle peridotite are poorly constrained. We experimentally investigated these reactions in experiments that adjoin an IBC glass against presynthesized dunite in a reaction couple at temperatures of 1100–1300 °C and pressures of 0.5–2.02 GPa for 0.33–31.66 h. These conditions produced experiments near to well above the solidus temperature of the IBC. Near solidus experiments produce garnet in the IBC at 2 GPa. Supersolidus experiments exhibit dissolution of olivine material into the IBC melt and the formation of clinopyroxene at the IBC melt-dunite interface. Dunite dissolution is attributed to the olivine undersaturated composition of the IBC melt. In both near- and supersolidus experiments, compositional variations produced by solid-state diffusion across the IBC melt-dunite interface are observed. When pressure increases, temperature decreases, or IBC melts become closer to olivine saturation, dissolution slows, and the effects of solid-state diffusion in the dunite become more evident. Similar chemical exchange reactions would occur in the lunar mantle as downwelling IBC and lunar peridotites are juxtaposed by cumulate overturn. Hybridized lunar mantle sources are expected to contain 47–84% normative peridotite and 16–53% IBC. Simple numerical simulations suggest that in addition to dissolution–precipitation reactions, mechanical mixing may be required to produce volumetrically significant hybridized mantle sources over geologically-relevant timescales.</p></div>","PeriodicalId":526,"journal":{"name":"Contributions to Mineralogy and Petrology","volume":"179 6","pages":""},"PeriodicalIF":3.5,"publicationDate":"2024-05-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140925368","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 sector-zoned garnet in graphitic metapelite from the Danba dome, eastern Tibetan Plateau (SW China)","authors":"Z. M.G. Li,&nbsp;F. Gaidies,&nbsp;Y.-C. Chen,&nbsp;Y.-L. Zhao,&nbsp;C.-M. Wu","doi":"10.1007/s00410-024-02139-8","DOIUrl":"10.1007/s00410-024-02139-8","url":null,"abstract":"<div><p>Texturally and chemically sector-zoned garnet crystals in two contiguous metapelitic rocks from the Danba dome, eastern Tibetan Plateau (SW China) were investigated. A petrographic boundary in one of the rocks (sample 21DB103) separates a thin section into two zones. Whereas one zone containing sector-zoned garnet and fined-grained matrix is enriched in graphite and quartz, the other zone encompasses garnets with relatively regular habit in a coarse-grained matrix poor in graphite and quartz. The two zones are distinct with regards to the chemical compositions of biotite and plagioclase, as well as the major and trace element zoning patterns of garnet. Electron back-scattered diffraction analysis shows that all the investigated garnet crystals in this sample are single crystals. Relatively higher <i>P-T</i> conditions are estimated for the initial growth of sector-zoned garnet (~ 5.0 kbar / ~540 ℃) compared to the regular garnet (~ 3.8 kbar / ~510 ℃) in this rock, possibly indicating that growth of the sector-zoned garnet postdates growth of the regular garnet. Texturally and chemically radial sectors with garnet-quartz intergrowths and irregular sectors of garnet are preserved in the other graphite-rich rock (sample 21DB104). Isopleth thermobarometry applied to the core of the largest garnet crystal exhibiting sector zoning in this sample reveals <i>P-T</i> conditions of initial garnet crystallization (~ 4.4 kbar / ~512 ℃) that deviate far (~ 0.8 kbar/~45 ℃) from equilibrium, potentially indicating significant overstepping required for garnet nucleation. Plagioclase inclusions in garnet display varying trace element abundances, indicating their replacements of different preexisting phases. These results suggest that abundant graphite may play a pivotal role in changing fluid conditions and reducing the solubility of SiO₂ to grow sector-zoned garnet, as well as impeding matrix coarsening. Development of sector-zoned core and dodecahedral faces of garnet may be related to rapid growth with changes in crystal morphology. Irregular sectors may have developed through fluid infiltration and local chemical adjustments.</p></div>","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":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140942296","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 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,&nbsp;Carsten Münker,&nbsp;Josua J. Pakulla,&nbsp;Eric Hasenstab-Dübeler,&nbsp;Christian S. Marien,&nbsp;Toni Schulz,&nbsp;Maria Kirchenbaur,&nbsp;Kathrin P. Schneider,&nbsp;Robin Tordy,&nbsp;Vera Schmitt,&nbsp;Frank Wombacher","doi":"10.1007/s00410-024-02137-w","DOIUrl":"10.1007/s00410-024-02137-w","url":null,"abstract":"&lt;div&gt;&lt;p&gt;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&lt;sub&gt;2&lt;/sub&gt;-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 (&lt;sup&gt;86&lt;/sup&gt;Sr/&lt;sup&gt;87&lt;/sup&gt;Sr up to 0.705408) and variable Pb isotope compositions (&lt;sup&gt;206&lt;/sup&gt;Pb/&lt;sup&gt;204&lt;/sup&gt;Pb = 18.61–19.70, &lt;sup&gt;207&lt;/sup&gt;Pb/&lt;sup&gt;204&lt;/sup&gt;Pb = 15.62–15.67 and &lt;sup&gt;208&lt;/sup&gt;Pb/&lt;sup&gt;204&lt;/sup&gt;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 &lt;sup&gt;187&lt;/sup&gt;Os/&lt;sup&gt;188&lt;/sup&gt;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}