Journal of Petrology最新文献

{"title":"Correction to: Textures and Chemistry of Crystal Cargo of the Pleiades Volcanic Field, Antarctica: Potential Influence of Ice Load in Modulating the Plumbing System","authors":"","doi":"10.1093/petrology/egae051","DOIUrl":"https://doi.org/10.1093/petrology/egae051","url":null,"abstract":"","PeriodicalId":16751,"journal":{"name":"Journal of Petrology","volume":null,"pages":null},"PeriodicalIF":3.9,"publicationDate":"2024-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141055030","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 and isotope geochemistry of Tschicoma Formation intermediate composition dome complexes, Jemez Mountains volcanic field, New Mexico, USA","authors":"Clara M Waelkens, John Stix, Fraser Goff, Dominique Weis","doi":"10.1093/petrology/egae045","DOIUrl":"https://doi.org/10.1093/petrology/egae045","url":null,"abstract":"Repeated intrusions of mafic magma have long been known to be a driver of long-lived magmatic systems. Although the importance of mafic recharge of silicic magma systems is well-documented in igneous petrology, the origin of this recharge magma is sometimes obscure. By examining the pre-caldera intermediate dome complexes of the Tschicoma Formation and their relationship to a dacitic recharge event into the Tshirege Member of the Bandelier Tuff, we aim to better understand the origin of mafic recharge events into the Bandelier magma chamber of Valles caldera, and the relationship between different stages of volcanic activity within the broader Jemez Mountains volcanic field (JMVF). Based on major, trace element and radiogenic isotopic data, we divide the Tschicoma Formation into three geochemical groups with similar petrologic evolutionary paths. The Cerro Grande, Cerro Rubio and Pajarito Mountain volcanic dome complexes form group A and have assimilated various amounts of a granitoid crustal component with low εNd, εHf and radiogenic Pb. Group B consists of the Sawyer Dome, Rendija Canyon and Caballo Mountain dome complexes, which have principally evolved through different degrees of fractional crystallisation of the same parent magma, itself a result of complex interactions of a mafic mantle-derived magma with the crust. The dacite domes and flows around Tschicoma Peak and the newly-described Cañada Bonita dacite form group C and are the result of mixing of Rendija Canyon magma with mafic recharge magma which is preserved as distinct mafic enclaves. At a later stage of the JMVF, during the eruption of the Tshirege Member, distinctive hornblende-dacite pumices formed as a result of the influx of more mafic recharge magma into the system, which mobilised a pre-existing dacite intrusion and injected it into the Tshirege rhyolite (Stimac, 1996; Boro et al., 2020). Based on trace element and isotopic compositions, we propose that dacite which was injected into the Tshirege magma chamber was related to the earlier-erupted Tschicoma Formation and itself represents a mixing product of Tshirege rhyolite and a precursor to the Tschicoma dacites. This implies that the Tschicoma magmatic system was long-lived yet dormant during the eruption of the Otowi Member of the Bandelier Tuff, then was reactivated shortly before the Tshirege eruption, temporarily co-existing and interacting with the Bandelier system as it erupted.","PeriodicalId":16751,"journal":{"name":"Journal of Petrology","volume":null,"pages":null},"PeriodicalIF":3.9,"publicationDate":"2024-04-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140841977","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Geochemical evidence of plume sources for high-MgO lavas in the WK Orogenic Belt","authors":"Zhiguo Cheng, Zhaochong Zhang, Mingde Lang, M Santosh, Lijuan Xu, Jingao Liu","doi":"10.1093/petrology/egae042","DOIUrl":"https://doi.org/10.1093/petrology/egae042","url":null,"abstract":"Plume-derived high-MgO lavas provide important information on the lithological, thermal and chemical variations of Earth’s deep mantle. Here we present results from detailed field, mineralogical and geochemical studies of Late Permian-Late Triassic high-MgO lavas near the Chalukou area in the Western Kunlun (WK) orogenic belt, NW China. The major element compositions of the lavas show extremely high MgO contents (26.6-33.8 wt.%) in accordance with olivine accumulation. The parental magma is inferred to be picritic in composition with MgO of 17.2±0.9 wt.%. Olivine Zn/Fe and Mn/Zn ratios suggest a peridotite dominated source with a minor fraction of pyroxenite. The temperature and oxygen fugacity estimates based on multi-methods including olivine-melt Mg-Fe equilibria, Al-in-olivine and olivine-spinel thermometry and oxybarometer yield a mantle potential temperature of 1522-1556 °C and high oxygen fugacity of FMQ+0.93. The H2O contents in the picrite flows are estimated as 3.67±1.0 wt.%, indicating the volatile-rich nature of parental magma and its mantle source. The immobile trace element features show that the WK picrites are OIB-like, with the enrichment in light rare earth elements and positive Nb, Ta, Zr and Hf anomalies. Furthermore, the Nd-O-Os isotopes display typical mantle values without involvement of recycled materials. Our results suggest the high-MgO volcanism in the WK orogenic belt originated from a volatile-rich plume source.","PeriodicalId":16751,"journal":{"name":"Journal of Petrology","volume":null,"pages":null},"PeriodicalIF":3.9,"publicationDate":"2024-04-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140615459","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":"Allanite in mantle eclogite xenoliths","authors":"Denis S Mikhailenko, Sonja Aulbach, Aleksandr S Stepanov, Andrey V Korsakov, Le Zhang, Yi-Gang Xu","doi":"10.1093/petrology/egae041","DOIUrl":"https://doi.org/10.1093/petrology/egae041","url":null,"abstract":"Rare-Earth Elements (REE) are key geochemical tracers of crust-mantle differentiation, but there are few direct data on REE-rich minerals in mantle rocks. Here, we report the combined petrography and comprehensive chemical and isotopic characterization of three coesite- and kyanite-bearing eclogite xenoliths from the Udachnaya kimberlite pipe (Siberian craton), which are unusual in that two xenoliths (one with diamond and graphite) contain discrete, idiomorphic crystals of allanite at the grain boundaries of garnet and omphacite. Another xenolith contains allanite as part of a complex aggregate of calcite, apatite, barite, and celestine hosted by serpentine, which is a low-temperature secondary minerals likely result from metasomatic reaction at shallower depths during the transport of eclogite by the erupting kimberlite melt. The bulk rock composition reconstructed from the trace element composition of garnet and omphacite show marked depletion in LREE, precluding equilibration with kimberlite melt, whereas the measured bulk compositions show chondrite-normalized REE patterns with conspicuous depletions of Ce-Pr-Nd relative to La and Sm. The presence of 0.005 – 0.008 wt. % of allanite, texturally and chemically out of equilibrium with the rock-forming minerals, allows balancing the LREE and Sm-Nd budget of the rock, whereas Th and U require additional hosts. This not only highlights the utility of measuring bulk eclogite xenoliths in bringing this unusual component to light, but also demonstrates that the long-known incompatible element enrichment in bulk eclogites reflects the deposition of discrete phases rather than merely bulk kimberlite melt addition. Although allanite is stable in metabasalts at the pressure-temperature conditions of 1025 – 1080 °C and 3.6 – 4.8 GPa recorded by the eclogite xenoliths, its association with Ba-Sr minerals suggests its formation via reaction of the host eclogites with kimberlite melt. This is supported by the similarity in 143Nd/144Nd ratios between bulk eclogite (0.51227 – 0.51249) and the host kimberlite at eruption, whereas clinopyroxene in part retains unradiogenic Sr (87Sr/86Sr = 0.70205 ± 0.00011) related to ancient depletion. The discovery of allanite in the Udachnaya eclogites demonstrates that this REE mineral can form when omphacite and grossular-rich garnet in eclogite breakdown in contact with REE- and alkali-rich carbonatite/kimberlite melt, and may be more common than hitherto recognized. Crystallization of allanite in the cratonic mantle eclogite reservoir may also help explain the difference in LREE abundances between the more strongly enriched carbonatite/kimberlite at depth and the final erupted product. It is likely that allanite is overlooked at eclogites xenoliths, while it is common accessory mineral, hosting REE in orogenic UHP/HP eclogites. Further studies are required to deciphered the peculiarities in metamorphic history recorded in eclogites xenoliths and orogenic eclogites as well ","PeriodicalId":16751,"journal":{"name":"Journal of Petrology","volume":null,"pages":null},"PeriodicalIF":3.9,"publicationDate":"2024-04-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140615403","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":"Petrology, Geochemistry and Mantle Minerals of the Walgidee Hills Lamproite, West Kimberley, Western Australia","authors":"A L Jaques","doi":"10.1093/petrology/egae040","DOIUrl":"https://doi.org/10.1093/petrology/egae040","url":null,"abstract":"The 17.44 Ma Walgidee Hills lamproite in the West Kimberley province of Western Australia is the type locality for several K-, Ba- and Ti-rich minerals characteristic of lamproites and, at 490 ha, the largest known lamproite. The Walgidee Hills pipe comprises a thin sequence of tuffs and breccia formed by explosive eruptions that excavated a large shallow crater that was infilled by lamproite magma which cooled and crystallised in situ. The lamproite is zoned in grain size, mineralogy, and mineral and rock composition from porphyritic olivine lamproite at the margin through medium grained lamproite comprised of olivine (altered), titanian phlogopite, diopside, leucite (altered) and titanian potassic richterite to coarse gained lamproite rich in potassic richterite, priderite, jeppeite, perovskite, apatite, wadeite and noonkanbahite at the centre of the body. Compositional zoning is evident across the lamproite in phlogopite (to lower Mg and Al, higher Fe), potassic richterite (to higher Fe and Na, lower Ti), priderite (to lower Cr) and perovskite (to lower Cr and Fe, higher Na, Sr, Y, Nb, U, REE). The Walgidee Hills lamproite is ultrapotassic and ranges from olivine lamproite (up to ~21 wt % MgO, ~800 μg/g Ni, ~4 wt % K2O) to sanidine/leucite-rich lamproite (~7 wt % MgO, ≤100 μg/g Ni, ~7 wt % K2O) at the centre of the pipe. The lamproite has low Al2O3, total Fe, Na2O and CaO (except for intensely carbonate-veined rocks at the centre) and is highly enriched in TiO2 (3−6.5 wt %), Ba, Rb, Sr, Zr and LREE (LaN = 150−520 x primitive mantle). A transect and geochemical contours show MgO, Ni and Cr contents decrease and P, K, Ti, Fe, Rb, Sr, Y, Zr, Nb, REE, Hf, Pb, Th and U abundances increase inwards to the most evolved rocks at the centre of the pipe, consistent with fractionation by inwards in situ crystallisation. The parent magma is estimated from the composition of the porphyritic olivine lamproite at the margins of the pipe to have ~16 ± 1 wt % MgO, ~600 μg/g Ni, ~6 wt % K2O with La/Yb ~ 150. Modelling suggests that the most MgO-rich lamproites result from entrainment of ~15–20 wt % mantle olivine in the parent magma. Cooling of the magma resulted in fractional crystallisation of olivine and in situ crystallisation with the evolved coarse-grained lamproites at the centre of the pipe crystallised from residual magma enriched in the more incompatible elements. Mantle xenocrysts include abundant Cr-Al spinel, chrome diopside, chrome pyrope, and rare diamond. Thermobarometry on the Cr diopside xenocrysts defines a cold paleogeotherm of ~38 mW/m2 and a thick lithosphere (~235 km) extending from the Kimberley craton. Many of the Cr diopsides from the deeper lithospheric mantle are enriched in K, Ba and LREE and these, and the Ti-rich spinel xenocrysts, are inferred to be derived from metasomatised mantle peridotite. The enriched trace element and Sr-Nd-Pb isotopic signatures of the Walgidee Hills lamproite suggest derivation from or extensive incorpora","PeriodicalId":16751,"journal":{"name":"Journal of Petrology","volume":null,"pages":null},"PeriodicalIF":3.9,"publicationDate":"2024-04-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140617922","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":"Arc foundations and subduction initiation: Insights into the magmatic evolution of the lower crust/upper mantle of the Izu-Bonin forearc during subduction initiation","authors":"Matthew P Loocke, Jonathan E Snow","doi":"10.1093/petrology/egae038","DOIUrl":"https://doi.org/10.1093/petrology/egae038","url":null,"abstract":"Our understanding of the processes at work in the lower crust/upper mantle transition zone during subduction initiation and early arc development has suffered from a general lack of in situ samples. Here, we present the results of petrographic and geochemical analysis of 34 samples (9 harzburgites, 13 dunites, 2 orthopyroxenites, 3 olivine-gabbros, and 7 wehrlites) collected from the inner trench wall of the Bonin Ridge, Izu-Bonin forearc. The sample suite records three main melt-rock reaction events involving melts with forearc basalt (FAB)-like, boninitic, and transitional compositions. The wehrlitic and gabbroic rocks trend towards more transitional to FAB compositions and the rest towards more boninitic compositions. The crosscutting occurrence of all three events in a single sample (wehrlite D31-106) establishes a relative timing of the events like that reported for the volcanic edifice of the Bonin Ridge, which transitioned from forearc basalt volcanism at subduction initiation (c.a., 51-52 Ma) to boninitic volcanism (c.a., 50-51 Ma) as the subduction system matured. We therefore suggest that the lower crust/upper mantle transition of the Bonin Ridge preserves a record of the transition from FAB melts created by decompression melting at subduction initiation to arc-type flux melting and boninitic volcanism thereafter. Orthopyroxenites and two anomalously fresh harzburgites from the sample suite are suggested to represent the later boninitic melts and possibly the result of hybridization between such melts and residual peridotites, respectively. Diffuse melt-rock reaction between the later boninites and/or subduction-related fluids and the earlier-formed FAB-related crust is recorded by enrichments in fluid mobile elements and depletions in first row transition metals in clinopyroxenes from a metasomatic vein in wehrlite sample D31-106. The chemistry of the wehrlitic and gabbroic clinopyroxenes suggests that they crystallized from hydrous, highly-depleted melts which lack a slab fluid signature. We thus suggest that highly-depleted melt fractions might be created early on during subduction initiation by the introduction of seawater into the proto-mantle wedge. The overall FAB-like nature of the crustal wehrlites and gabbros would suggest that most of the lower arc crust was created by forearc extension during/following subduction initiation and that later, mature arc volcanism may have contributed little or no material to the lower crust/upper mantle record in the outer forearc.","PeriodicalId":16751,"journal":{"name":"Journal of Petrology","volume":null,"pages":null},"PeriodicalIF":3.9,"publicationDate":"2024-04-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140585430","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":"Machine Learning in Petrology: State-of-the-Art and Future Perspectives","authors":"Maurizio Petrelli","doi":"10.1093/petrology/egae036","DOIUrl":"https://doi.org/10.1093/petrology/egae036","url":null,"abstract":"The present manuscript reports on the state-of-the-art and future perspectives of Machine Learning (ML) in petrology. To achieve this goal, it first introduces the basics of ML, including definitions, core concepts, and applications. Then, it starts reviewing the state-of-the-art of ML in petrology. Established applications mainly concern the so-called data-driven discovery and involve specific tasks like clustering, dimensionality reduction, classification, and regression. Among them, clustering and dimensionality reduction have been demonstrated to be valuable for decoding the chemical record stored in igneous and metamorphic phases and to enhance data visualization, respectively. Classification and regression tasks find applications, for example, in petrotectonic discrimination and geo-thermobarometry, respectively. The main core of the manuscript consists of depicting emerging trends and the future directions of ML in petrological investigations. I propose a future scenario where ML methods will progressively integrate and support established petrological methods in automating time-consuming and repetitive tasks, improving current models, and boosting discovery. In this framework, promising applications include (a) the acquisition of new multimodal petrologic data, (b) the development of data fusion techniques, physics-informed ML models, and ML-supported numerical simulations, and (c) the continuous exploration of the ML potential in petrology. To boost the contribution of ML in petrology, our main challenges are: (a) to improve the ability of ML models to capture the complexity of petrologic processes, (b) progressively link machine learning algorithms with the physical and thermodynamic nature of the investigated problems, (c) to start a collaborative effort among researchers coming from different disciplines, both in research and teaching.","PeriodicalId":16751,"journal":{"name":"Journal of Petrology","volume":null,"pages":null},"PeriodicalIF":3.9,"publicationDate":"2024-03-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140322199","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":"Fluoritites produced by crystallization of carbonate-fluoride magma","authors":"Aleksandr S Stepanov, Jovid Aminov, Sharifjon Odinaev, Farukh Sh Iskandarov, Shao-Yong Jiang, Nikolai S Karmanov","doi":"10.1093/petrology/egae033","DOIUrl":"https://doi.org/10.1093/petrology/egae033","url":null,"abstract":"Fluorite-dominated rocks are occasionally found in association with carbonatites, but their geologic and petrologic relations are rarely reported. The Dunkeldyk area of the Pamir mountains in south-eastern Tajikistan contains dikes of distinctive rocks composed of calcite, fluorite, celestine-barite, sulfides, apatite, with minor quartz, biotite, and REE-fluorcarbonates. The dikes have sharp contacts with the host (meta-)sedimentary rocks and layering with ribbons, ranging from fluorite-bearing calcite carbonatites to fluoritites (rocks with >50% fluorite). The fluoritites are characterised by high Ca, F, Ba, Sr, REE and S coupled with anomalously low O. The geologic relations and textures suggest a magmatic origin of the dikes from melts close to calcite-fluorite eutectic that experienced nucleation-controlled differentiation during the crystallization of dikes and the formation of fluoritite cumulates in larger intrusions. The Dunkeldyk dikes demonstrate that sizable geological bodies of fluorite-dominated rocks could form from carbonate-fluoride melts originating by differentiation of alkaline silicate magmas.","PeriodicalId":16751,"journal":{"name":"Journal of Petrology","volume":null,"pages":null},"PeriodicalIF":3.9,"publicationDate":"2024-03-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140325884","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":"Sub-arc mantle heterogeneity of the Northern Luzon Volcanic Arc: mineral and whole rock compositional variability in mantle xenoliths from Lutao Island","authors":"J Gregory Shellnutt, Meng-Wan Yeh, Tung-Yi Lee, Yoshiyuki Iizuka, Wei-Yu Chen, M P Manu Prasanth","doi":"10.1093/petrology/egae037","DOIUrl":"https://doi.org/10.1093/petrology/egae037","url":null,"abstract":"Mantle xenoliths hosted in volcanic rocks from the island of Lutao offer a glimpse into the nature of the mantle beneath the northern Luzon volcanic arc. The xenoliths are spinel-bearing and composed mostly of harzburgite with one lherzolite and one olivine orthopyroxenite. The olivine (Fo92.5-88.9), orthopyroxene (Mg# = 94.6-89.2), and clinopyroxene (Wo49.1-38.1En57.0-45.4Fs3.0-11.0) compositions are similar to those of abyssal peridotites. The spinel compositions are variable and can be principally divided into high-Al (Cr# < 45) and low-Al (Cr# > 45) groupings. The whole rock compositions are similar to abyssal peridotite (Al2O3 = 0.95-2.07 wt%; Mg# = 88.5-90.9) and have U-shaped chondrite normalized rare earth element patterns. The Sr-Nd isotopes of the xenoliths are broadly chondritic (87Sr/86Sri = 0.704400-0.707908; εNd(t) = 0.0-+1.5). The two-pyroxene equilibrium temperatures range from 900-1200°C with the majority of temperature estimates >1000°C. The olivine-orthopyroxene-spinel oxygen barometry estimates yielded ΔFMQ values from 0 to +2 and correspond to moderately oxidizing to oxidizing conditions. The xenoliths are likely derived from the Philippine Sea Plate lithospheric mantle that was modified by melt extraction and/or fluid enrichment processes. Trace element and isotopic mixing modeling indicate that 1% to 2% contamination by subducted South China Sea sediment can explain the Sr-Nd isotopic enrichment and Th and U elemental variability within the xenoliths assuming an initial composition similar to enriched depleted mid-ocean ridge mantle (E-DMM). The anomalously high two-pyroxene equilibrium temperatures of the Lutao xenoliths relative to other regions of the northern Luzon volcanic arc (Iraya < 1000°C) indicate that they were affected by a high temperature event that was likely a consequence of recent intra-arc rifting that occurred after collision (< 6 Ma) between the Luzon arc and the Eurasian margin.","PeriodicalId":16751,"journal":{"name":"Journal of Petrology","volume":null,"pages":null},"PeriodicalIF":3.9,"publicationDate":"2024-03-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140322287","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":"Self-organisation in gabbroic cumulates: a new patterning mechanism driven by differential migration of immiscible liquids in a crystal mush?","authors":"Marian B Holness","doi":"10.1093/petrology/egae034","DOIUrl":"https://doi.org/10.1093/petrology/egae034","url":null,"abstract":"Self-organisation in plutonic igneous rocks has been suggested to form by a variety of mechanisms including oscillatory nucleation and growth, competitive particle growth (CPG), and preferential dissolution and re-precipitation during fluid infiltration enhanced by compaction, with driving forces including reduction of the interfacial energy budget by either Ostwald ripening or because the energy of boundaries between two grains of the same mineral is less than that between two grains of different minerals. An investigation of the Stillwater inch-scale layering shows that the CPG patterning mechanism leaves a characteristic microstructural signature preserving evidence for a highly interconnected melt in textural equilibrium, and slow super- and sub-solidus cooling: such a signature is also preserved in chromite-bearing fine-scale layers in the Bushveld intrusion. The cm-scale micro-rhythmic layering of the Skaergaard intrusion, superimposed on single modally-graded layers, does not have these microstructural features. Furthermore, the energy of all relevant inter-phase grain boundaries in the Skaergaard gabbros is less than that of grain boundaries involving only one mineral, viscous compaction was not a significant process in the Skaergaard intrusion, and patterning by oscillatory nucleation and growth is precluded by the fact that the micro-rhythmic layering is superimposed on modally graded layers formed by sedimentation. A new patterning mechanism is proposed, operational only in intrusions in which the interstitial liquid of the crystal mush intersects a binode and splits into two immiscible conjugates. Cm-scale separation of the immiscible conjugate liquids in a compositionally-graded mush, due to both gravity and capillary forces, leads to layering due to differences in their wetting properties. The positive feedback required for pattern formation is due to the two immiscible conjugates predominantly crystallising the minerals which they preferentially wet.","PeriodicalId":16751,"journal":{"name":"Journal of Petrology","volume":null,"pages":null},"PeriodicalIF":3.9,"publicationDate":"2024-03-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140322193","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}