Contributions to Mineralogy and Petrology最新文献

{"title":"Protracted cooling in a long-lived Orosirian orogen: insights from major and trace element diffusion modeling in metamorphic garnet","authors":"Jia-Hui Liu,&nbsp;Thorsten A. Markmann,&nbsp;Hugo Dominguez,&nbsp;Jinghui Guo,&nbsp;Qian W. L. Zhang,&nbsp;Liangliang Zhang,&nbsp;Guochun Zhao,&nbsp;Pierre Lanari","doi":"10.1007/s00410-025-02290-w","DOIUrl":"10.1007/s00410-025-02290-w","url":null,"abstract":"<div><p>Constraining the cooling timescales/rates of metamorphic rocks of orogens is critical for understanding their tectonic settings and geodynamic mechanisms, especially their links to plate tectonics and the formation of the continental lithosphere. The Orosirian period (2.1–1.8 Ga) is characterized by widespread orogenesis and is potentially linked to the onset of global plate tectonics, yet the metamorphic cooling histories of Orosirian orogens remain underexplored. This study applies a dual-constraint diffusion modeling approach, integrating both major (Fe, Mn, Mg, Ca) and trace elements (HREE + Y) in garnet. This is based on multi-mineral microprobe and laser ablation mapping to two metamorphic rocks from the Wutai–Fuping crustal section of the Trans-North China Orogen (TNCO). Sample 20FP09, collected from the Wanzi Supracrustal Rocks, records a two-stage retrograde <i>P–T</i> path: an isothermal decompression (ITD) from the M2 peak (725 ° C/0.9 GPa) to M3 decompression (725 ° C/0.6 GPa), followed by isobaric cooling (IBC) to M4 (550 ° C/0.4 GPa). Sample L17, from the Shizui Subgroup, preserves a single cooling segment from the M2T peak (680 ° C/0.6 GPa) to M3 (550 ° C/0.4 GPa). Diffusion modeling using multiple experimental datasets of diffusion coefficients yields an ITD duration of 1–4 Myr and an IBC duration of 11–31 Myr for sample 20FP09, and a single 35–50 Myr cooling interval for sample L17. Together, these results indicate a protracted cooling duration of 13–50 Myr, corresponding to a cooling rate of 2–13 ° C/Myr for the TNCO. Such rates are significantly slower than those of Phanerozoic orogens (&gt; 100 ° C/Myr). This implies that Orosirian orogenesis may have involved in prolonged thermal relaxation within a hot, weak Paleoproterozoic lithosphere, likely influenced by higher mantle temperatures and orogenic thermal structures. This study also demonstrates the importance of large datasets containing high spatial element maps for obtaining robust constraints on metamorphic timescales; and offers a first-order empirical estimate of Sc diffusivity in garnet, which remains experimentally unconstrained.</p></div>","PeriodicalId":526,"journal":{"name":"Contributions to Mineralogy and Petrology","volume":"181 2","pages":""},"PeriodicalIF":3.7,"publicationDate":"2026-01-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146027116","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":"Calbuco and Osorno volcanoes (Chile) tap into mantle sources that only differ by their water content","authors":"Jacqueline Vander Auwera,&nbsp;Tonin Bechon,&nbsp;Salvatrice Montalbano,&nbsp;Bernard Charlier,&nbsp;Olivier Bolle,&nbsp;Pierre Schiano,&nbsp;Nicolas Cluzel,&nbsp;Jean-Luc Devidal,&nbsp;Luisa Ottolini,&nbsp;Luis E. Lara,&nbsp;Olivier Namur,&nbsp;Thomas van Gerve","doi":"10.1007/s00410-025-02282-w","DOIUrl":"10.1007/s00410-025-02282-w","url":null,"abstract":"<div><p>The Osorno and Calbuco stratovolcanoes are situated just 27 km apart along the volcanic arc front of the Central Southern Volcanic Zone (Chile), yet they exhibit significantly different characteristics. Notably, Calbuco intermediate to andesitic lavas contain amphibole, which is absent in Osorno, and has a much higher explosivity (up to VEI = 4 to 5). Their olivine-hosted melt inclusions (MI) display similar major elements differentiation trends. Incompatible trace element ratios overlap in both volcanoes and therefore do not correlate with the H₂O and Cl contents. Indeed, MIs data and petrological hygrometers indicate higher volatiles content at Calbuco (~ 3 wt% @ 51.3 wt% SiO₂, 951–3232 ppm) compared to Osorno (~ 1 wt% @ 50.5 wt% SiO₂, 521–1091 ppm). Because the Cpx-only geobarometers and geophysical data both place the Osorno and Calbuco main magma reservoirs at the same depth, their differing volatile contents are interpreted as inherited from the mantle melts. Their calculated primary magmas result from similar to identical partial melting fractions of mantle sources that differ only in their H₂O content. The mantle source beneath Calbuco partially melted at a lower temperature, possibly because of the slightly more trench ward position of the volcano, which projects vertically into a cooler part of the mantle wedge “nose”. The lack of correlation between incompatible elements and H₂O content is interpreted as resulting from evidence for a decoupling between H₂O, transported mainly in a solute-poor fluid, and incompatible elements, which are delivered by melts derived from the subducting oceanic lithosphere. The variability of the mantle wedge H₂O concentration and the uncorrelated content of slab tracers and H₂O have also been observed at a global scale.</p></div>","PeriodicalId":526,"journal":{"name":"Contributions to Mineralogy and Petrology","volume":"181 2","pages":""},"PeriodicalIF":3.7,"publicationDate":"2026-01-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146027115","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":"Reactions, element transfer, and fracturing at ultramafic rock–sediment contacts: insights from reaction experiments at 500 °C and 1 GPa","authors":"Shunya Okino,&nbsp;Atsushi Okamoto,&nbsp;Ryosuke Oyanagi,&nbsp;Yukiko Kita,&nbsp;Sando Sawa,&nbsp;Jun Muto","doi":"10.1007/s00410-025-02283-9","DOIUrl":"10.1007/s00410-025-02283-9","url":null,"abstract":"<div>\u0000 \u0000 <p>Metasomatic reactions affect the mechanical properties of the interface between the mantle wedge and a subducting plate. However, the controls on fluid-mediated reactions that occur at the interface, involving mass transfer, volume change, and deformation, are poorly constrained. In this study, we experimentally investigated metasomatic reactions at the boundary between mantle rocks (serpentinite and harzburgite) and sedimentary rocks (quartzite or pelitic schist) at 500 °C and 1 GPa, using an assembly with a core of metasedimentary rock sandwiched between serpentinite and harzburgite. In all experimental runs, talc formed preferentially in the mantle rocks. In experiments using quartzite, talc formed along pre-existing fractures in serpentinite and as a layer within harzburgite, while no obvious alteration occurred in the quartzite. In experiments using pelitic schist, talc formed within tree-like fractures in serpentinite, whereas in harzburgite it formed as a layer or wedge-like filling. In the pelitic schist, albite porphyroblasts were preferentially replaced by Mg-rich saponite. These observations and mass balance calculations indicate that: (1) the solid volume-decreasing reactions in serpentinite accompanying reaction-induced fracturing and solid volume-increasing reaction in harzburgite caused the contrasting textures in the two rock types; and (2) Al-bearing minerals in the sedimentary rocks absorbed Mg, which facilitated the overall progress of the Mg-releasing, talc-forming reactions in the mantle rocks. These results suggest that compositional heterogeneity in subducting sediments can produce variations in the talc distribution and rheological properties at the slab–mantle interface, potentially affecting the location of episodic tremor and slip in a mantle wedge corner.</p>\u0000 </div>","PeriodicalId":526,"journal":{"name":"Contributions to Mineralogy and Petrology","volume":"181 2","pages":""},"PeriodicalIF":3.7,"publicationDate":"2026-01-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00410-025-02283-9.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145993755","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":"Phase equilibria modelling and geochronology of Ediacaran-Cambrian granites in West Garo Hills, Assam-Meghalaya Gneissic Complex, NE India: implications for East Gondwana assembly","authors":"Rhituparna Gogoi,&nbsp;Pranjit Hazarika,&nbsp;Dewashish Upadhyay","doi":"10.1007/s00410-025-02284-8","DOIUrl":"10.1007/s00410-025-02284-8","url":null,"abstract":"<div><p>The Assam-Meghalaya Gneissic Complex (AMGC) in northeast India represents the eastern fringe of the Precambrian Indian Shield and comprises Meso- to Neoproterozoic migmatitic quartzofeldspathic gneisses, foliated granitoids, metapelites and Ediacaran-Cambrian granites. Our work focuses on the petrogenesis of garnet-bearing and garnet-absent granites of the West Garo Hills (WGH), in the westernmost AMGC, that are intrusive into basement quartzofeldspathic gneisses (QFG) and foliated granitoids. We use phase equilibria modelling to evaluate whether partial melting of basement rocks could have produced the Ediacaran-Cambrian granites in the area. Textural and chemical characteristics of garnet support a magmatic origin. Phase equilibria modelling, carried out on garnet-bearing granite, indicates that the garnet core composition equilibrated at ∼7.5 kb/830°C, while rim composition record ∼5.3 kb/730°C. Phase equilibria modelling suggests that the QFG and metapelite basement rocks were metamorphosed at ∼5.5 kb/750°C and ~ 5.7 kb/740°C, respectively. U-Pb dating of monazite and xenotime in the granite, the host QFG, and pegmatites yielded comparable 591 − 542 Ma, 582 − 540 Ma and 562 − 460 Ma ages, respectively, which date the timing of high-grade metamorphism and granite emplacement during Pan-African orogenesis. Our melt-reintegrated phase equilibria modelling suggests that partial melting of basement QFG and associated metapelite with varying degrees of fractional crystallization could produce melts having composition similar to those of the granites in the WGH. A comparison of the modelled melt compositions with the compiled granite data from the entire AMGC suggests that basement QFG-derived melts can largely explain the composition of the Ediacaran-Cambrian granites.</p></div>","PeriodicalId":526,"journal":{"name":"Contributions to Mineralogy and Petrology","volume":"181 1","pages":""},"PeriodicalIF":3.7,"publicationDate":"2026-01-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145930772","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":"Mantle heterogeneity and complicated melt migration revealed by chemical gradients across the dunite-harzburgite sequence in the Zedong ophiolite, South Tibet","authors":"Zhen-Yu Zhang,&nbsp;Chuan-Zhou Liu,&nbsp;Yan Liang,&nbsp;Tong Liu,&nbsp;Chang Zhang,&nbsp;Bo-Da Liu","doi":"10.1007/s00410-025-02287-5","DOIUrl":"10.1007/s00410-025-02287-5","url":null,"abstract":"<div>\u0000 \u0000 <p>Dunite channels are critical pathways for melt extraction and migration within the asthenosphere. Although their formation within mantle peridotite sequences is often attributed to melt-rock interaction, the underlying physical processes remain poorly constrained. This study examines variations in both major and trace elements across a dunite-harzburgite sequence in the Zedong ophiolite to better understand these physical processes. Geochemical profiles across the dunite-harzburgite transect reveal concentration gradients near the dunite-harzburgite contact, particularly within the harzburgite. Such compositional variations were interpreted through two-dimensional numerical simulations, coupled with diffusion and advection in porous media. The results indicate that trace element gradients in olivine can be produced by a melt flow along the dunite–harzburgite boundary with lateral advection from dunite to harzburgite, which is consistent with those observed in the field. Trace element patterns of the interstitial clinopyroxene grains within the dunite suggest their crystallization from a final pulse of percolating melt through the channel during the waning stage of the melt transport system, which probably occurred shortly before the ophiolite obduction. Integrating these results with previous studies on mafic–ultramafic rocks in the Moho Transition Zone (MTZ), we propose that the dunite–harzburgite sequence in the Zedong ophiolite was initially generated in the asthenosphere beneath an ultra-slow spreading ridge, which subsequently experienced a multi-stage history of melt migration and melt–rock interaction during progressive mantle upwelling. Such a complex history significantly influenced the lithological and geochemical architecture of the MTZ of the ophiolite. Overall, results from this study demonstrate that both dunites and their surrounding harzburgites bear variable concentration gradients, resulting from both mantle heterogeneity and variations in melt compositions within individual dunite channel.</p>\u0000 </div>","PeriodicalId":526,"journal":{"name":"Contributions to Mineralogy and Petrology","volume":"181 1","pages":""},"PeriodicalIF":3.7,"publicationDate":"2026-01-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145930711","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 transition from magmatic to hydrothermal crystallization conditions of a shallow-level granitic pluton","authors":"G. T. Thompson,&nbsp;C. J. Rufledt,&nbsp;J. B. Thomas","doi":"10.1007/s00410-025-02280-y","DOIUrl":"10.1007/s00410-025-02280-y","url":null,"abstract":"<div><p>Many thermobarometric methods applied to granitic composition rocks that crystallized at &lt; 5 kbar yield temperature estimates ~ 50 to 100 °C lower than the widely used haplogranite water-saturated solidus. To address thermobarometric discrepancies, we investigated a shallow-level granitic pluton that is not enriched in fluxing elements such as Li, B, P, or F. The Rito del Medio pluton (RDMP) near Questa, New Mexico contains numerous minerals and inclusions suitable for thermobarometric estimates, and it has abundant miarolitic cavities that represent the final crystallization stages. Occurrences of coexisting melt and fluid inclusions show that groundmass minerals crystallized from a water-saturated magma. After groundmass crystallization, the pluton transitioned to a fluid-dominated system manifested by the crystallization of freestanding minerals contained in the miarolitic cavities. The granite contains mica, feldspar, quartz, primary fluid inclusions in quartz, and accessory minerals including garnet with quartz inclusions. We used minerals and their inclusions in both paragenetic contexts to track changes in P, T, and mineral and fluid compositions that accompanied the magmatic-to-hydrothermal transition. Resultant univariant curves from thermobarometry for the groundmass minerals converge at ~ 1.9 to 2.1 kbar and ~ 590 to 625 °C indicating final magmatic crystallization. To address discrepancies between thermobarometric results and the haplogranite solidus, we performed crystallization experiments at 2 kbar, which show that RDMP compositions magmas complete crystallization at temperatures ~ 620–625 °C. Univariant curves for thermobarometric approaches applied to the RDMP miarolitic cavity minerals converge at ~ 1.5 to 2.1 kbar and ~ 500 to 525 °C defining the transition to hydrothermal crystallization conditions.</p></div>","PeriodicalId":526,"journal":{"name":"Contributions to Mineralogy and Petrology","volume":"181 1","pages":""},"PeriodicalIF":3.7,"publicationDate":"2026-01-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00410-025-02280-y.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145930589","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":"Growth and deformation of apatite across metamorphic facies during collisional orogenesis","authors":"Yanyan Zhang,&nbsp;Zhongbao Zhao,&nbsp;Wentao Cao,&nbsp;Jinxue Du,&nbsp;Zuolin Tian,&nbsp;Paul D. Bons,&nbsp;Xuxuan Ma,&nbsp;Xiaohong Mao,&nbsp;Fenghua Liang,&nbsp;Zhiyong Zhu,&nbsp;Haibing Li,&nbsp;Guocan Wang","doi":"10.1007/s00410-025-02293-7","DOIUrl":"10.1007/s00410-025-02293-7","url":null,"abstract":"<div><p>Apatite is a key accessory phase in metamorphic rocks, capable of recording mineral growth, deformation, and fluid-rock interaction across a wide range of metamorphic conditions. To evaluate the mechanisms of apatite growth and deformation, we present an integrated microstructural and geochemical study of apatite in high-pressure granulite- to lower amphibolite-facies rocks from the Eastern Himalayan Syntaxis, Tibetan Plateau. Cathodoluminescence imaging, electron backscatter diffraction, electron probe microanalysis, and in situ laser ablation inductively coupled plasma mass spectrometry trace element data were combined to assess apatite growth histories and post-crystallization modifications. In high-pressure granulite-facies samples, apatite grains display strong shape-preferred orientation (SPO) and significant intragranular deformation but lack a crystallographic preferred orientation (CPO), consistent with pre-peak metamorphism growth and experienced peak metamorphic conditions. Medium-pressure granulite-facies apatite shows oscillatory zoning, weak SPO and CPO, and limited deformation, indicating post-tectonic growth from compositionally homogeneous fluids. Apatite from upper amphibolite-facies samples preserves both strong SPO and CPO, with only minor deformation features, suggesting syn-tectonic crystallization during foliation development. In lower amphibolite-facies rocks, apatite is characterized by core-mantle structures, weak SPO, but CPO subparallel to stretching lineation, and variable trace element patterns, consistent with episodic growth during fluid-mediated dissolution–precipitation under retrograde conditions. Systematic variations in apatite chemistry—including decreasing Sr/Y, ΣLREE, and (La/Yb)_N, and increasing Th/U and F/Cl with decreasing metamorphic grade—reflect the influence of metamorphic fluid composition, mineral reaction pathways, and elemental partition among mineral phases at corresponding metamorphic conditions. Despite differences in deformation and growth history, consistent correlations between texture and composition suggest localized, short-range fluid-mediated element redistribution. Our results demonstrate that multiple generations of apatite can be distinguished through integrated microstructural and geochemical datasets, providing a robust archive of pressure–temperature (<i>P–T</i>) conditions and fluid evolution in metamorphic terranes.</p></div>","PeriodicalId":526,"journal":{"name":"Contributions to Mineralogy and Petrology","volume":"181 1","pages":""},"PeriodicalIF":3.7,"publicationDate":"2026-01-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145929937","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":"Impurity poisoning as a mechanism for the formation of zircon oscillatory growth zones","authors":"Marisa D. Acosta,&nbsp;James M. Watkins,&nbsp;Denis Fougerouse,&nbsp;Michelle L. Foley,&nbsp;Oliver Plümper,&nbsp;David W. Saxey,&nbsp;Steven M. Reddy,&nbsp;Mark H. Reed","doi":"10.1007/s00410-025-02288-4","DOIUrl":"10.1007/s00410-025-02288-4","url":null,"abstract":"<div><p>Oscillatory zoning — alternating high- and low-impurity (trace element) zones — is a hallmark of magmatic zircon from felsic systems and preserves the history of magmatic systems. Although commonly attributed to fluctuations in temperature, pressure, or melt composition, the mechanisms driving this zoning remain uncertain. Here, we show that high-impurity growth zones, which appear homogeneous when imaged with a scanning electron microscope (SEM), actually consist of finer-scale growth zones when viewed at the nanoscale - and still finer zones are revealed at the atomic scale. The apparent homogeneity in SEM images results from electron beam convolution, where features smaller than the beam’s interaction volume cannot be resolved. Backscattered electron images have higher spatial resolution than cathodoluminescent images, but high-impurity zones imaged with both are found to consist of finer zones at the atomic scale when imaged with atom probe tomography. Adjacent low-impurity zones are homogeneous across all scales. We interpret these observations as evidence of impurity poisoning during near-equilibrium zircon growth. Faceted crystal growth at low supersaturation leads to rejection of impurities, except for those allowed by equilibrium partitioning. Rejected impurities accumulate on the crystal surface, blocking normal incorporation of atoms and temporarily halting growth. When supersaturation exceeds a critical threshold, growth resumes, trapping the adsorbed impurities and forming a high-impurity zone. These findings not only help to resolve the origin of oscillatory zoning in zircon but also establish a generalizable mechanism of impurity poisoning during near-equilibrium crystal growth, redefining how mineral records are interpreted in igneous systems and beyond.</p></div>","PeriodicalId":526,"journal":{"name":"Contributions to Mineralogy and Petrology","volume":"181 1","pages":""},"PeriodicalIF":3.7,"publicationDate":"2026-01-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145929902","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":"Creep behaviour of omphacite and amphibole-plagioclase symplectite: the role of heterogeneous hydration in the Tso Morari eclogite during retrogression","authors":"Dripta Dutta,&nbsp;Takeshi Imayama,&nbsp;Dyuti Prakash Sarkar,&nbsp;Jun-ichi Ando,&nbsp;Kaushik Das","doi":"10.1007/s00410-025-02281-x","DOIUrl":"10.1007/s00410-025-02281-x","url":null,"abstract":"<div><p>Replacement reactions progress to varying degrees depending on the P-T conditions, exhumation rates, and fluid availability. The preservation of reactants and retrogressed products allows for the reconstruction of microstructural and mineralogical progression, which we investigated using electron backscattered diffraction and microprobe analyses on the omphacite, amphibole-plagioclase symplectite, and matrix amphibole of the Tso Morari eclogite. Elliptical shapes, absence of chemical zonation, and scarce subgrains suggest that omphacite grains deformed via body diffusion creep. Because of the heterogeneous distribution of externally derived hydrous fluids in the eclogite, the omphacite is replaced by amphibole-plagioclase symplectite either partially along the peripheries (S1 symplectite) or completely (S2 symplectite). Strong omphacite CPOs, caused by growth anisotropy, are inherited by the symplectite constituents such that &lt; 001 &gt; _Omp//&lt;001 &gt; _Amp//&lt;010 &gt; _Plag, &lt; 010 &gt; _Omp//&lt;010 &gt; _Amp, and &lt; 100 &gt; _Omp//&lt;100 &gt; _Amp//&lt;001 &gt; _Plag. Both generations of amphibole grains, i.e., in S1 and S2, crystallised during exhumation. The S1 amphibole grains are poorer in Si (6.75–7.34 apfu) and crystallised earlier than those in S2 (Si = 7.29–7.79 apfu). Elevated stresses at the reaction interfaces deformed the plagioclase in S1 via dislocation creep. In contrast, due to fluid abundance, the plagioclase in S2 deformed via diffusion creep-accommodated grain boundary sliding. The misorientations across the subgrain boundaries in the amphibole grains constituting S1 and S2 are similar to those in the amphibole of the eclogite matrix and the garnet amphibolites. The amphibole grains in S1, eclogite matrix, and garnet amphibolites deformed via dislocation creep, whereas dislocation-accommodated grain boundary sliding deformed those in S2.</p></div>","PeriodicalId":526,"journal":{"name":"Contributions to Mineralogy and Petrology","volume":"181 1","pages":""},"PeriodicalIF":3.7,"publicationDate":"2025-12-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00410-025-02281-x.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145694959","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":"Linking crystal shape and dynamic undercooling: a new framework for inferring magmatic crystallization histories","authors":"Amanda Lindoo,&nbsp;Madeleine C. S. Humphreys,&nbsp;Charlotte Gordon,&nbsp;Martin F. Mangler,&nbsp;Edward W. Llewellin,&nbsp;Richard A. Brooker,&nbsp;Fabian B. Wadsworth,&nbsp;Eshbal Geifman","doi":"10.1007/s00410-025-02278-6","DOIUrl":"10.1007/s00410-025-02278-6","url":null,"abstract":"<div><p>Magmas contain crystals exhibiting diverse shapes and sizes, yet the relationship between crystal shape (specifically aspect ratio) and undercooling (<span>(Delta T)</span>), the driving force for crystallization, remains poorly constrained. Crystal shape should correlate with undercooling because undercooling governs the growth regime (interface-controlled versus diffusion-controlled) and thus the resulting crystal form. Prior experiments confirm that large nominal undercoolings drive transitions from polyhedral to hopper, skeletal, or dendritic forms. Large undercoolings reflect rapid decompression or cooling, differing from slower cooling rates typical of magmatic intrusions and storage systems. In such slowly cooled environments, crystals remain polyhedral, exhibiting subtle shape variations. Accurately quantifying crystal shape evolution at relatively low undercoolings could provide critical insights into crystallization histories, improving interpretations of the timescales and processes governing magma storage and eruption dynamics. Experimental verification of correlations between aspect ratios of polyhedral crystals and cooling rates remains inconclusive, possibly because nominal undercooling neglects the dynamic evolution of undercooling throughout crystallization. To address this, we introduce <i>average instantaneous undercooling</i> (<span>(overline{{Delta T_{I} }})</span>), a metric capturing dynamic undercooling history during crystallization. Through controlled cooling experiments and numerical modelling, we demonstrate that higher <span>(overline{{Delta T_{I} }})</span> histories produce tabular, high aspect ratio plagioclase crystals, whereas lower <span>(overline{{Delta T_{I} }})</span> produces more prismatic crystals with lower aspect ratios. These variations in shape reflect undercooling-driven shifts in the predominant growth mechanism operating on different crystal faces. By quantitatively linking crystal shape to <span>(overline{{Delta T_{I} }})</span>, our study provides a new approach for reconstructing crystallization histories in magmas under varying <i>pH2O-T-t</i> conditions.</p></div>","PeriodicalId":526,"journal":{"name":"Contributions to Mineralogy and Petrology","volume":"180 12","pages":""},"PeriodicalIF":3.7,"publicationDate":"2025-12-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12669325/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145666666","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}