Lithos最新文献

{"title":"Garnet and clinopyroxene from 1.98 Ga Kimozero kimberlites, Karelia, Russia: Evidence of the multistage evolution of the ancient lithospheric mantle","authors":"A.A. Nosova , A.V. Kargin , K.G. Erofeeva , A.Ya. Dokuchaev , I.A. Kondrashov , O.I. Okina","doi":"10.1016/j.lithos.2024.107911","DOIUrl":"10.1016/j.lithos.2024.107911","url":null,"abstract":"<div><div>We present the major and trace element data for garnets and clinopyroxenes from the heavy mineral concentrate of the 1.98 Ga Kimozero kimberlites, Karelia, Russia, in the context of mantle petrology and evolution.</div><div>All studied garnets are characterized by high-Cr-Ca compositions with CaO and Cr<sub>2</sub>O<sub>3</sub> contents up to 13 wt% and classified as garnets from the wehrlite paragenesis. The uvarovite content could reach up to 0.29 mol%. Kimozero garnets are characterized by low TiO<sub>2</sub> concentrations and highly enriched in light rare earth elements, distinguishing them from the classical garnet from peridotite xenoliths and megacrysts from Phanerozoic kimberlites.</div><div>Based on the variations in garnet composition, we suggest that at 1.98 Ga, the lithospheric mantle of the Karelian craton underwent several tectonothermal events. The high Cr<sub>2</sub>O<sub>3</sub> compositions of the studied garnets we propose that the protolith of the Kimozero garnets was a highly depleted high-Mg# high-Cr mantle substrate that underwent extensive melting in the spinel-garnet stability region and that the Cr-rich garnet has a spinel precursor. The high CaO content and elevated LREE and HFSE concentrations indicate that the Kimozero garnets suggested multiple stages of mantle metasomatism. Garnets with high CaO and Cr<sub>2</sub>O<sub>3</sub> composition and weakly sinusoidal REE patterns with low Zr/Hf and La/Yb ratios and high Ti/Eu ratios suggested water-rich carbonate fluid as the agent of mantle metasomatism. An increasing the Zr/Hf and La/Yb ratios with low Ti/Eu and significant LREE enrichment in some Kimozero garnets indicates an increasing role of carbonate fluid in the metasomatic processes. Enrichment in the HREE and Zr concentrations, along with decreasing CaO and Cr<sub>2</sub>O<sub>3</sub> in garnet, may reflect an additional stage of mantle metasomatism associated with early stages of mantle plume ascent.</div><div>Clinopyroxene xenocrysts are predominantly Cr-diopsides with Mg# values ranging 0.85–0.92 with Cr<sub>2</sub>O<sub>3</sub> (1.32–4.03 wt%) and Na<sub>2</sub>O (1.67–2.81 wt%) concentrations, low TiO<sub>2</sub> contents and enrichment in light rare earth elements (Ce<img>Nd) compared to heavy rare earth elements. Such clinopyroxenes could be formed by a metasomatic process, specifically the interaction of melts that have equilibrated to MARID-type mantle metasomatites with the depleted lithospheric mantle.</div><div>The mineralogy of xenocrysts from the Kimozero kimberlite differs from the widespread xenogenic mantle mineralogy of the Neoproterozoic and Phanerozoic kimberlites. The high-Cr and low-Ti contents of the garnets and clinopyroxenes and the presence of uvarovite garnets could be the characteristics of the ancient lithospheric mantle, which was not preserved until the Phanerozoic due to the cooling of the Earth, and numerous plume and metasomatic events that perturbed the subcontinental","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"494 ","pages":"Article 107911"},"PeriodicalIF":2.9,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143161512","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Chemical and boron isotope composition of multiple generations of tourmaline from the Nassarawa lithium-rich pegmatites, Nigeria: Implications for the mechanism of lithium enrichment","authors":"Junteng Lv ,&nbsp;Xin Chen ,&nbsp;Junsheng Jiang ,&nbsp;Hans-Peter Schertl ,&nbsp;Liang Cao ,&nbsp;Xiaojia Jiang","doi":"10.1016/j.lithos.2024.107936","DOIUrl":"10.1016/j.lithos.2024.107936","url":null,"abstract":"<div><div>Pegmatites are the primary global source of rare metal lithium (Li). While previous studies highlight the importance of high granitic magma differentiation in the formation of lithium-rich pegmatites, the processes and timescales of magmatic fractionation remain unclear. Specifically, it is uncertain whether lithium-rich melts originate from multiple magmatic pulses or a single continuous fractional crystallization event. This study presents elemental mapping, in-situ trace element analysis, and boron isotope data for four generations of tourmaline sourced from the lithium mineralization of the Nassarawa-Keffi pegmatitic belt in Nigeria. Tourmaline grains intergrowth with plagioclase, quartz, and K-feldspar, display compositional zoning and resorption-precipitation textures, indicating incremental growth predominantly influenced by the injection of multistage magma batches. The notable periodic increases in Li and Mn contents, accompanied by decreases in Fe, as well as the distinct variation trends in the Li/Sc, Li/K, and Li/Ge ratios across the four tourmaline generations, suggest the involvement of at least four distinct melt pulses. The narrow δ¹¹B values observed across all tourmaline generations indicate a single magmatic source. The observed decrease in δ¹¹B values in the later tourmaline generations is likely due to fluid exsolution and mineral crystallization processes. Subsequent magma pulses exhibit higher lithium concentrations than earlier, suggesting that multistage melt pulses and high fractional crystallization within a deep magmatic reservoir are essential for lithium enrichment in the Nassarawa lithium-rich pegmatites. Based on these findings, we propose an alternative model in which multiple melt-release events from a single cooling magmatic reservoir contribute to the formation of lithium-rich pegmatites.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"494 ","pages":"Article 107936"},"PeriodicalIF":2.9,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143161860","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":"Petrography and geochemistry of heterogeneous mantle peridotites from the Banovina Ophiolite Complex, Croatia","authors":"Šime Bilić ,&nbsp;Vesnica Garašić ,&nbsp;Alan B. Woodland ,&nbsp;Hans-Michael Seitz","doi":"10.1016/j.lithos.2025.107942","DOIUrl":"10.1016/j.lithos.2025.107942","url":null,"abstract":"<div><div>This study investigated the petrographic and geochemical characteristics of highly serpentinised and heterogenic mantle peridotites exposed in Banovina, central Croatia, which represent the basal ophiolitic unit of the Central Dinaridic Ophiolite Belt (CDOB). Results indicate the existence of two structurally and chemically different sets of peridotites that outcrop along two geographically distinct belts. The northern belt contains mostly serpentinite breccias and serpentinised, depleted and predominantly porphyroclastic lherzolites (N spinel lherzolites and N plagioclase lherzolites) that form part of an ophiolitic mélange. In contrast, the southern belt contains larger masses of peridotites that comprise predominantly fertile lherzolites (S spinel lherzolites) with equigranular to porphyroclastic textures. Bulk rock chemistry reveals that the S spinel lherzolites have lower Cr# and Mg# and higher Al₂O₃, CaO, Na₂O, TiO₂ and REE contents than the N lherzolites. The same relations are also observed when comparing pyroxenes compositions from S and N lherzolites. Trace element signatures of clinopyroxene and orthopyroxene from the two belts are completely different and indicate a different petrogenetic history. Spinels from all N lherzolites have higher Cr# than those from the S lherzolites. Differences between N plagioclase and N spinel lherzolites are most evident from the significantly higher Cr# and TiO₂ in the spinel from plagioclase lherzolites, reflecting subsolidus plagioclase formation. Geochemical and petrographic analysis indicates a subcontinental origin of the S spinel lherzolites and a suboceanic (MOR) origin of the N lherzolites. Both types come with their own petrographic and geochemical heterogeneities that suggest complex and multi-phase petrogenesis. Overall, the results correlate well with studies from other neighboring CDOB localities.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"494 ","pages":"Article 107942"},"PeriodicalIF":2.9,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143161958","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":"New integrations of UPb zircon data from Caledonian intrusions in the Southern Uplands of Scotland","authors":"Chloe A.R. Gemmell ,&nbsp;Iain Neill ,&nbsp;Mark Wildman ,&nbsp;Careen MacRae ,&nbsp;David Currie ,&nbsp;Joshua F. Einsle","doi":"10.1016/j.lithos.2024.107941","DOIUrl":"10.1016/j.lithos.2024.107941","url":null,"abstract":"<div><div>The Laurentian margin in Britain and Ireland experienced the Caledonian-Acadian orogenies resulting from Palaeozoic closure of the Iapetus Ocean and accretion of Baltica and peri-Gondwanan terranes. However, the age and significance of magmatism remain contested, without a geologically consistent geodynamic reconstruction. We have interrogated the U<img>Pb zircon record of intrusive complexes within the Southern Uplands-Down-Longford accretionary complex, focused on the Southern Uplands in Scotland. New texturally constrained laser ablation data are presented from the Carsphairn, Black Stockarton Moor, Bengairn, and Cheviot complexes. In these locations, most zircons contain poorly zoned cores with ²⁰⁶Pb/²³⁸U ages no older than ∼ 424 Ma, chemically comparable with younger magmatic overgrowths. Magmatic overgrowth ages confirm emplacement of Carsphairn at ∼ 414–411 Ma, Black Stockarton Moor and Bengairn at ∼ 410–408 Ma, and Cheviot at ∼ 400 Ma. Across the accretionary complex, the onset of zircon growth from ∼ 424 Ma appears to mark slab roll-back processes. Zircon cores may represent stalling and crystallisation of magmas in the deep crust, whilst emplacement into the shallow crust after ∼ 415 Ma accompanies the onset of regional transtension. We do not feel there is sufficient evidence to directly attribute magmatism to slab breakoff, despite this process being popularly championed in Scottish and Irish geology. We discuss the latest geodynamic interpretations of magmatism during the Caledonian-Acadian events, including events to the south of the Iapetus suture, and argue that complete zircon histories have a role to play in reconstruction of ancient orogens.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"494 ","pages":"Article 107941"},"PeriodicalIF":2.9,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143162020","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":"The timing of the Middle Triassic magmatism in the Dolomites area (Southern Alps, Italy): UPb geochronology of zircon and titanite hosted in plutonic rocks and phonolite dykes","authors":"Nicolò Nardini ,&nbsp;Federico Casetta ,&nbsp;Ryan B. Ickert ,&nbsp;Lorenzo Tavazzani ,&nbsp;Disha C. Okhai ,&nbsp;Stefano Peres ,&nbsp;Elio Dellantonio ,&nbsp;Theodoros Ntaflos ,&nbsp;Massimo Coltorti","doi":"10.1016/j.lithos.2024.107894","DOIUrl":"10.1016/j.lithos.2024.107894","url":null,"abstract":"<div><div>The Middle Triassic magmatic event in the Southern Alps (Italy) is characterised by the emplacement and eruption of multiple magma batches with different geochemical affinities in a short time span. In this work, we present the first geochemical and geochronological data on highly differentiated alkaline dykes (phonolites) exposed in and near the Middle Triassic Predazzo magmatic complex (Southern Alps, Italy) and a first complete geochronological survey of the Predazzo pluton. The phonolites, cutting the Middle Triassic volcanic sequences, are sodalite- and aegirine-bearing and have titanite, apatite and magnetite as accessory phases. Their trace element concentration reflects a geochemical signature similar to the orogenic-like signature typical of the Middle Triassic magmatic rocks of the Predazzo complex. New in situ U<img>Pb dating on titanite from the phonolite dykes and U<img>Pb dating on zircon separates from all the magmatic units of the Predazzo pluton show that the phonolite dykes were emplaced between 233.8 ± 3.1 Ma and 238.1 ± 4.5 Ma, i.e., overlapping to and postdating the emplacement and crystallisation of plutonic rocks, which yield ages ranging from 237.97 ± 0.15 Ma to 238.31 ± 0.13 Ma. The ages obtained for the diverse suites of the pluton are in good agreement with previous dating and show that silica-saturated to -undersaturated rocks were placed within the same context in a short time span. Thermometry and hygrometry on titanite, clinopyroxene and K-feldspar revealed that phonolites represent volatile- and REE-rich (H₂O = 8 ± 0.6 wt%) highly differentiated alkaline melts intruding at relatively low T (752–868 °C), which easily caused the spatially related Cu<img>W mineralisation. Comparisons with sub-volcanic rocks exposed in the Central (Edolo) and Western Alps (Finero mafic complex) indicate that the phonolites still preserve the orogenic signature of the Middle Triassic event in the Southalpine, that characterise all magmas emplaced before the opening of the Alpine Tethys in the Late Triassic. These new geochronological constraints on the Predazzo pluton and phonolite dykes enable us to outline the complete sequence of magmatic events associated with the emplacement of the Predazzo volcano-plutonic complex during Mid-Triassic and to speculate about the genesis of Cu<img>W mineralisation.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"494 ","pages":"Article 107894"},"PeriodicalIF":2.9,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143161003","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":"The fate of solid-phase transfer in subduction zones: Evidence from Ti-oxides in Luobusa ophiolitic chromitite","authors":"Fahui Xiong ,&nbsp;Basem Zoheir ,&nbsp;Tian Qiu ,&nbsp;Xiangzhen Xu ,&nbsp;Weibin Gui ,&nbsp;Jingsui Yang","doi":"10.1016/j.lithos.2024.107892","DOIUrl":"10.1016/j.lithos.2024.107892","url":null,"abstract":"<div><div>The transport of hydrous components from a subducting oceanic plate to the supra-subduction lithospheric mantle and their influence on arc magmas is well-documented. Yet the transfer of solid-phase materials remains enigmatic, despite an increasing body of literature regarding inherited rutile in well-characterized arc magmas and ophiolitic chromitites. The mechanism governing the introduction of solid phases into the overlying mantle wedge as well as the duration of their residence are poorly understood. This study investigates mineralogical and geochemical characteristics of rutile inclusions in the Luobusa chromitite of southern Tibet.</div><div>In the investigated chromitite, rutile, associated with ilmenite, corundum, ulvöspinel, zircon, and melt silicate inclusions, exhibits geochemical characteristics indicative of derivation from crustal mafic rocks. Estimated formation or recrystallization temperatures of rutile range from 570 to 675 °C at approximately 1.2 GPa. These temperature estimates illustrate the challenges of obtaining accurate dating, as the rutile U<img>Pb system resets near 600 °C. The Fe/Zr ratios in Luobusa rutile serve as indicators of H₂O/Zr ratios, suggesting a significant role for hydrous components in the behavior of high field strength elements (HFSE) during subduction processes.</div><div>A fluid-assisted transport mechanism likely facilitated the movement of HFSE, such as Ti, V, Zr, Nb, and Ta, within accessory mineral phases into the supra-subduction mantle wedge. The presence of rutile and polymorphs of TiO₂, including Ti_0.82Si_0.18O₂ and TiO₂-II, within chromite crystals underscores the extensive recycling and recrystallization processes occurring under diverse mantle conditions during the genesis and evolution of the Luobusa ophiolites.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"494 ","pages":"Article 107892"},"PeriodicalIF":2.9,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143161069","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":"Troilite nano-inclusions in apatite: Implications for melt immiscibility from a lamprophyric magma","authors":"Marina Martínez ,&nbsp;Mercè Corbella","doi":"10.1016/j.lithos.2024.107896","DOIUrl":"10.1016/j.lithos.2024.107896","url":null,"abstract":"<div><div>Calcium phosphate apatite is a volatile-rich mineral ubiquitous in terrestrial and planetary igneous rocks and can form by a variety of processes. However, the utilization of this powerful mineral for unraveling complex magmatic systems is challenged due to its crystallographic complexity. Recent work has demonstrated that examination by transmission electron microscopy (TEM) can reveal nanostructures that are of paramount importance for a correct interpretation of its chemistry. Here, we have examined different apatite grains from two thin sections of Les Guilleries lamprophyre dykes (NE Spain), representing the last pulses of deep magma ascension at the end of the Variscan orogeny. We have identified two different generations of F-rich apatites (magmatic and hydrothermal), which have been examined by SEM, EPMA, TEM, and Raman spectroscopy. Primary, magmatic apatites are close to rounded and even-sized, whereas secondary, hydrothermal apatites are highly acicular, cut most of the mineral phases, and contain slightly higher amounts of Cl and detectable rare-earth elements compared to magmatic apatites. Transmission electron microscopy work shows that magmatic apatites contain abundant nano-inclusions (∼5–60 nm in size) in their cores, consisting of euhedral, negative crystals of troilite, an amorphous phase, and/or a possible gas phase. We argue that fluctuations of temperature during ascent of the lamprophyric magma triggered S saturation and subsequent unmixing of a Fe<img>S melt from the silicate magma. The immiscible Fe<img>S melt was trapped in negative crystals of rapidly growing apatite grains. During ascent of the magma, an additional fluctuation of temperature slowed its growth rate and prevented the generation of new, negative crystals, thus the rims of these apatite grains grew free of inclusions. Upon cooling, troilite crystallized at a temperature of ∼950 °C and relatively high oxygen and sulfur fugacities (log <em>f</em>S₂ ≈ −7; log <em>f</em>O₂ &lt; −8.5). The crystallizing troilite was likely followed by exsolution of a Si,Cl-bearing aqueous fluid and a gas phase. Finally, some Cl (∼0.43 wt%) and Si (∼2.87 wt%) from the aqueous fluid phase within the inclusions migrated outwards and interacted with the host apatite at very localized scales (a few nanometers). This study suggests that the unmixing of Fe<img>S melts during calc-alkaline magmatism may be more common than previously recognized, which has important implications for potentially concentrate economically valuable elements that may lead to the formation of ore deposits.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"494 ","pages":"Article 107896"},"PeriodicalIF":2.9,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143161072","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":"Granitoids from St. Martin/Maarten Island, Caribbean: Insights on the role of mantle processes in the Lesser Antilles arc","authors":"Petros Koutsovitis ,&nbsp;Michiel J. van der Meulen ,&nbsp;Tirza van Daalen ,&nbsp;Pavlos Tyrologou ,&nbsp;Nikolaos Koukouzas ,&nbsp;Alkiviadis Sideridis ,&nbsp;Christos Karkalis ,&nbsp;Michel Grégoire ,&nbsp;Petros Petrounias ,&nbsp;Theodoros Ntaflos ,&nbsp;Konstantinos Lentas","doi":"10.1016/j.lithos.2024.107926","DOIUrl":"10.1016/j.lithos.2024.107926","url":null,"abstract":"<div><div>The granitoids in St. Martin Island, Lesser Antilles – Caribbean, consist of granodiorites (Type-I low REE; Type-II high REE), leucotonalites, melatonalites and Qz-monzodiorites. These are I-type calc-alkaline granitoids, although classification of the newly identified melatonalites remains enigmatic, likely reflecting magma mixing between different sources for their formation. Geothermometry applications yield high formation temperatures for the melatonalites and the Type-II granodiorites exceeding by ∼100 °C those calculated for the other granitoids. Pressure conditions were relatively high for the melatonalites and granodiorites (∼4.2 and ∼ 4.0 kbar respectively), with the lowest assigned to the leucotonalites (∼1.8 kbar). Magnesiohornblende crystallized at the final crystallization stages (∼740 °C; ∼2.5 km depth), under hydrous (H₂O = ∼3.5 wt%) and highly oxidizing conditions (ΔNNO up to +2.7).</div><div>Fractional crystallization significantly contributed to the compositional variability of the evolved granitoid lithotypes, with plagioclase being preferably fractionated in the Type-I granodiorites, relative to the Type-II granodiorites that mostly involved K-feldspar removal. Additionally, fluctuation of the hydrous and slab-derived fluid fluxes further promoted granitoid differentiation. Geochemical and Sr-Nd isotopic data reveal restricted sediment contamination of the mantle wedge. Melatonalites and Type-II granodiorites appear to have been formed during the early evolution stages of subduction initiation, whereas leucotonalites represent the late-stage shallow crystallization granitoid phase.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"494 ","pages":"Article 107926"},"PeriodicalIF":2.9,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143161963","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":"Trans-crustal magmatic processes revealed by amphibole breakdown textures at the Quillacas monogenetic volcanic center, Bolivia","authors":"L.C. Velázquez Santana ,&nbsp;C.L. McLeod ,&nbsp;B. Shaulis ,&nbsp;M. Loocke ,&nbsp;R. Al Gbory","doi":"10.1016/j.lithos.2024.107891","DOIUrl":"10.1016/j.lithos.2024.107891","url":null,"abstract":"<div><div>Amphibole exerts a fundamental control on arc magma petrogenesis, differentiation, and the long-term evolution of the arc crust. This study identifies two texturally distinct amphibole populations within andesitic lavas and entrained hornblendite cumulates at the Quillacas monogenetic volcanic center in the Eastern Altiplano, Bolivia. Within the hornblendites, all amphiboles are tschermakitic, large (≤800 μm) with thick, granular reaction rims (avg. 27 μm thickness). In the host andesites, tschermakites are also the dominant amphibole species but are smaller (250–400 μm) with thin, symplectic reaction rims (avg. 7–9 μm thickness). An intergrowth of symplectic and granular reaction rims is also observed in this population. The amphibole populations within the Quillacas magmatic system also record irregular volumetric decomposition where amphibole is replaced by mineral aggregates of plagioclase, pyroxene, and oxide within the crystal. This suggests the occurrence of a relatively slow reaction between the amphibole and melt trapped in fractures and cleavages during decompression-induced degassing. Geothermobarometry indicates that the hornblendite cumulate tschermakites crystallized at P-T conditions ranging from 467 to 598 ± 12 % MPa and 945–991 ± 22 °C. The host andesite tschermakites crystallized at P-T conditions ranging from 448 to 570 ± 12 % MPa and 928–1004 ± 22 °C. These geothermobarometric constraints correspond to depths of 16–24 km, which, within this region of the Central Andean crust, coincides with a regionally extensive low-seismic velocity zone. The texturally distinct amphibole populations imply that a multi-stage trans-crustal magmatic system is likely present beneath the Quillacas volcanic center. In this scenario, a crystal mush zone exists at upper crustal depths where the hornblendite cumulate tschermakites initially crystallized. Magma recharge into this mush zone initiated a reaction between hornblendite cumulates and the melt which formed the amphibole granular rims. This recharge event also transported the host andesite tschermakites that subsequently developed symplectic rims due to heating and ascent-driven decompression. This study supports the presence of amphibole-dominated mush filters in the upper crust of the Central Andean arc and advances our understanding of amphibole's role in the evolution of arc magmatic systems.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"494 ","pages":"Article 107891"},"PeriodicalIF":2.9,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143161004","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":"Petrogenesis of the Early Cretaceous volcanic-intrusive complex in northern North China Craton: Implications for crustal magma system evolution","authors":"Duo Zhang ,&nbsp;Deyou Sun ,&nbsp;Jun Gou ,&nbsp;Jian Zhou ,&nbsp;Changdong Wang ,&nbsp;Wenbo Sun ,&nbsp;Li Tian","doi":"10.1016/j.lithos.2024.107924","DOIUrl":"10.1016/j.lithos.2024.107924","url":null,"abstract":"<div><div>Identifying the origin and evolution of silicic magma is crucial for elucidating the transcrustal magmatic system and the evolution of continental crust. The Early Cretaceous volcanic-intrusive complex in the Kulongshan area provides an important insight into the evolution of silicic magma. Zircon U<img>Pb dating indicates that these spatially associated rocks formed between 140 and 131 Ma. The volcanic and subvolcanic rocks and alkali feldspar–alkaline granites are high silica (SiO₂ = 75.79–77.89 wt%) and alkali-rich and demonstrate strong negative Eu anomalies (Eu/Eu* = 0.02–0.06), as is typical of A-type rocks. Significant geochemical discontinuities were found between the potassium (K)-feldspar granite porphyry (SiO₂ = 67.86–70.80 wt%, Eu/Eu* = 0.20–0.44) and the high-silica rocks. These rocks exhibit ε_Hf(t) and T_DM2 values ranging from −18.1 to −9.2 and 2.34 to 1.84 Ga, respectively, indicating that the magmas originated from partial melting of the Paleoproterozoic continental crust. The geochemical characteristics show that the high-silica volcanic and subvolcanic rocks, along with the alkali-feldspar–alkaline granites, display a distinct trend of fractional crystallization. The K-feldspar granite porphyry exhibits distinct characteristics of feldspar accumulation. The consistent material source of the Kulongshan volcanic-intrusive complex suggests that the magma may have ascended from the source area, leading to magma interaction in the deep magma reservoir, followed by fractional crystallization in the shallow magma reservoir. The results indicate that Early Cretaceous high-silica rocks were formed via the extraction and coalescence of interstitial melts within the magma reservoir, with the K-feldspar granite porphyry representing residual crystal accumulation.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"494 ","pages":"Article 107924"},"PeriodicalIF":2.9,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143161550","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}