Lithos最新文献

{"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}

{"title":"Paleocene Katisho ultramafic-mafic-intermediate igneous rocks in the Ladakh Batholith, northern Pakistan: Implications for the transition from intra-oceanic to Andean type arc setting","authors":"Zahid Hussain ,&nbsp;Chuan-Lin Zhang ,&nbsp;Masumeh Sargazi ,&nbsp;Irfan Maqbool Bhat ,&nbsp;Xian-Tao Ye ,&nbsp;Zhi-Hao Song ,&nbsp;Muhammad Farhan ,&nbsp;Zaheen Ullah ,&nbsp;Tehseen Zafar ,&nbsp;Amjad Hussain ,&nbsp;Syed Asim Hussain","doi":"10.1016/j.lithos.2024.107910","DOIUrl":"10.1016/j.lithos.2024.107910","url":null,"abstract":"<div><div>The Kohistan-Ladakh Arc records terrane accretion and continental growth history from the opening to the closure of the Neo-Tethys. However, its role in the Neo-Tethys evolution and implication for continental crustal growth remain debated. This study present the first comprehensive dataset on the newly identified Katisho ultramafic-mafic-intermediate rocks within the Ladakh Batholith, including field and petrographic features, in-situ zircon U<img>Pb ages and Lu<img>Hf analysis, mineral chemistry, bulk-rock elemental and isotopic (Sr<img>Nd) compositions, aiming to have a better understanding the building up of the Kohistan-Ladakh arc and its role in the Neo-Tethys evolution. The Katisho gabbros and granodiorites, located on the northwestern side of the Ladakh Batholith, contain irregular ultramafic enclaves. Zircon U<img>Pb dating reveals that the gabbro and granodiorite were emplaced coevally at ca. 66.6 Ma. Geochemical signatures, such as enriched LILE, depleted HFSE, and consistent LREE-enriched REE patterns, show typical features of the arc-related calc-alkaline magmatisim. Their depleted whole-rock Sr ([⁸⁷Sr/⁸⁶Sr]_<em>i</em> = 0.7041 to 0.7045), Nd [εNd(t) = +2.4 to +3.2], and zircon Hf [εHf(t) = +4.1 to +11.1] isotopic compositions, along with their elemental features (enriched LILE, low FC3MS values [0.4‐–0.6], and Cpx: Grt ratio = 6:1) collectively demonstrate a common origin from a depleted lithospheric mantle source, predominantly spinel-bearing peridotite metasomatized by slab-derived fluids. The diverse type of the intrusions can be attributed to the fractional crystallization of a common primary mafic magma. This study, combined with previous research, concludes that the Paleocene Katisho intrusions were genetically related to the rollback of the Neo-Tethyan Oceanic slab beneath the Asian margin. This magmatic phase marks the transition of the Kohistan-Ladakh arc from an intra-oceanic arc to an Andean-type continental margin, prior the India-Asia collision.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"494 ","pages":"Article 107910"},"PeriodicalIF":2.9,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143161554","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":"Genesis and geodynamic setting of granitoids at the giant Siahdik S1 porphyry CuAu deposit, Chagai belt, Western Pakistan","authors":"Xiaoyu Wang ,&nbsp;Wenchang Li ,&nbsp;Rolf L. Romer ,&nbsp;Fucheng Yang ,&nbsp;Jiangyong Li ,&nbsp;Ke Liu ,&nbsp;Zhijun Zhang ,&nbsp;Liwei Yan","doi":"10.1016/j.lithos.2024.107919","DOIUrl":"10.1016/j.lithos.2024.107919","url":null,"abstract":"<div><div>The Siahdik deposit is a newly discovered giant porphyry Cu<img>Au deposit (&gt;8 Mt. Cu) in the western Chagai magmatic belt, Pakistan. The deposit includes a western (3.27 Mt. at 0.32 % Cu and 0.12 g/t Au) and an eastern (4.84 Mt. at 0.48 % Cu and 0.10 g/t Au) mineralization center. The origin and tectonic settings of granitoids at this deposit is not clear, in particular as different magmatic units show strong mineralization. Our new age data show that the western porphyry center includes pre-mineralization biotite granites (42.7 ± 0.4 Ma), ore-bearing granodiorites (40.6 ± 0.5 Ma), ore-forming quartz-diorite porphyries (24.4 ± 0.2 Ma), and post-mineralization andesite porphyries (24.0 ± 0.3 Ma). Eight molybdenite samples from mineralized granodiorites and quartz-diorite porphyries yield Re<img>Os model ages of 24.8–25.2 Ma with a weighted average age of 25.0 ± 0.3 Ma, implying that all mineralization belongs to the younger group of magmatic rocks. The Middle Eocene biotite granites and granodiorites are high-K calc-alkaline series rocks, whereas the Late Oligocene quartz-diorite porphyries and andesite porphyries are medium-K calc-alkaline series rocks with high Sr/Y ratios. These granitic rocks are enriched in the large ion lithophile elements Rb, Ba, and K and light rare earth elements and depleted in heavy rare earth elements and the high-field strength elements Nb, Ta, and Ti. They have relatively low (⁸⁷Sr/⁸⁶Sr)_i values (0.70407–0.70575), positive ε_Nd(t) (1.4 to 3.7) and ε_Hf(t) values (+10.7 to +21.4), and mantle-like zircon δ¹⁸O values (+4.09 to +6.48), typical for magmas derived from a relatively enriched mantle source that was modified by components from the subducted slab. The compositions of zircon crystals from the granitoids of the deposit indicate that the parental magmas – in particular the fertile quartz-diorite porphyries – were relatively oxidized. These geochemical and isotopic features, along with the absence of inherited zircon grains suggest that the parental magmas of the Late Oligocene porphyry Cu<img>Au deposit most probably were derived from the partial melting of the metasomatized mantle wedge, with minor contributions from crust materials. The deposit formed in a continental arc setting during northward subduction of the Neo-Tethys. The studied porphyry Cu<img>Au deposit is related to a highly oxidized, H₂O- and volatile-rich magmatic system.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"494 ","pages":"Article 107919"},"PeriodicalIF":2.9,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143161960","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":"Compositional diversity of continental arc magmatism caused by variable degrees of mantle melting: A Gangdese case study","authors":"Zhi-Guo Zhou ,&nbsp;Ze Liu ,&nbsp;Qing Wang ,&nbsp;Di-Cheng Zhu ,&nbsp;Peter A. Cawood ,&nbsp;Yu An ,&nbsp;Li Liu ,&nbsp;Liang-Liang Zhang ,&nbsp;Jin-Cheng Xie","doi":"10.1016/j.lithos.2024.107935","DOIUrl":"10.1016/j.lithos.2024.107935","url":null,"abstract":"<div><div>Compositional diversity of magmatism in continental arcs is common and can be collectively attributed to the combination of intra-crustal and extra-crustal processes, but distinguishing their relative contributions remains a challenge. This study investigates processes controlling the compositional diversity in the ca. 220–150 Ma intrusive rocks from the central Gangdese arc (88–92°E) in southern Tibet. New and published zircon Hf isotopic data reveal that assimilation with enriched crustal materials is insignificant for these rocks, but is evident for the coeval intrusive rocks from the eastern Gangdese arc (92–94°E). Our comprehensive dataset reveals progressive increases in highly incompatible elemental (HIEs; e.g., Cs and Rb) concentrations and Rb/Sr ratios in the basaltic rocks from ca. 220 to 150 Ma, coinciding with an increase in crustal thickness from ∼25–30 km to ∼35–40 km and the progressive waning of arc magmatic intensity during this time period. This temporal trend, coupled with the similar HIE enrichment trends recorded by the intrusive rocks from the Kohistan arc, suggest that the decreasing degrees of mantle melting due to progressive mantle cooling played a primary control on the compositional diversity. This work provides a way to trace how varying degrees of mantle melting, in addition to intra-crustal processes, impact the compositional diversity of continental arc magmatism.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"494 ","pages":"Article 107935"},"PeriodicalIF":2.9,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143161964","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":"Growth processes of zircon crystals in a granitic magma chamber, variation in UPb age, titanium concentration, and Th/U in relation to internal texture","authors":"Takashi Yuguchi ,&nbsp;Kyoka Endo ,&nbsp;Satoshi Suzuki ,&nbsp;Yasuhiro Ogita ,&nbsp;Shuhei Sakata ,&nbsp;Tatsunori Yokoyama ,&nbsp;Takumi Imura ,&nbsp;Takeshi Ohno ,&nbsp;Eiji Sasao","doi":"10.1016/j.lithos.2024.107909","DOIUrl":"10.1016/j.lithos.2024.107909","url":null,"abstract":"<div><div>This study describes the growth characteristics of zircon crystals in the Kuki granite from the Kitakami Mountains in northeastern Japan as the key for elucidating granitic magma chamber processes. Using two approaches, analyses based on multiple sections of separated zircon crystals and thin-section-based zircon crystal analyses, we determined the characteristics of the 3D internal structure of the crystals, variations in U<img>Pb age, Ti concentrations, and Th/U in relation to crystal texture, and the crystallization sequence between zircon crystals and other minerals (i.e., biotite, quartz, and K-feldspar) within the magma chamber. The textures, which occupy a large proportion of zircon, comprise low luminescence homogeneous cores (LLCs) and oscillatory zoning (OZ). The 3D distribution of the zircon internal structure can be classified into three types: Type 1 zircon comprising LLCs and the surrounding OZ and Types 2 and 3 zircon crystals composed entirely of OZ from the cores to the rims and characterized by brightness and darkness cores, respectively. LLC and OZ grew at temperatures from approximately 900 to 800 °C and 850 to 700 °C, respectively, and LLC has a higher Th/U than that of OZ, indicating that fractional crystallization progression as the magma chamber cooled resulted in the transition from LLC to OZ. In the progression of fractional crystallization, the diffusion rate deceleration with decreasing magma temperatures triggered the transition from interfacial reaction-controlled growth producing LLC to diffusion-controlled growth producing OZ. In the thin-section analysis, zircon crystals which contained in different minerals are characterized by different Th/U values. The variation in Th/U and the crystallization temperature of zircon crystals considering the surrounding minerals can be used to elucidate the differentiation and mineral crystallization in magma chamber processes over a wide range of temperature conditions.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"494 ","pages":"Article 107909"},"PeriodicalIF":2.9,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143161063","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":"Zircon U-Pb ages, trace elements, and Hf isotopes establish a genetic link between volcanic ash beds and porphyritic intrusions during early Silurian in the South China Block","authors":"Tianrui Wang ,&nbsp;Bo Ran ,&nbsp;Shugen Liu ,&nbsp;M. Santosh ,&nbsp;Zhiwu Li ,&nbsp;Yuyue Han ,&nbsp;Yuehao Ye","doi":"10.1016/j.lithos.2024.107890","DOIUrl":"10.1016/j.lithos.2024.107890","url":null,"abstract":"<div><div>The provenance of the Late Ordovician to Early Silurian volcanic ash beds (VABs) in the South China Block (SCB) remains debated. In this study, we provide new zircon U-Pb age, trace element, and Hf isotope data of bentonites, crystal tuffs, and porphyritic intrusions from the Longmaxi Formation of the Dabashan area in the northern margin of the SCB with a view to investigate the composition, tectonic setting, and source of their parent magmas. The zircon U-Pb ages show that the volcanic eruption and magma emplacement occurred in the Early Silurian (ca. 440–434 Ma). The zircon trace element compositions are consistent with A-type parent magmas formed in intraplate extensional settings. The positive ε_Hf(t) values (+1.7 to +6.9) of zircon indicate an enriched mantle source for the magma, with possible crustal input. The similar U-Pb ages, trace element compositions, and ε_Hf(t) values of zircon grains from VABs and porphyritic intrusion in the Dabashan area suggest that their parent magmas shared similar sources. These A-type parent magmas could have originated in intraplate extension settings on the passive margin of the northern SCB during the subduction of the Proto-Tethys Ocean towards the North Qinling Terrane. Our results suggest that the Paleo-Tethys oceanic basin did not open before the Early Silurian (ca. 434 Ma) in the Dabashan area.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"494 ","pages":"Article 107890"},"PeriodicalIF":2.9,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143161065","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}