Lithos最新文献

{"title":"Sulfur cycling in the gabbroic section of the Oman ophiolite","authors":"Ana P. Jesus ,&nbsp;Harald Strauss ,&nbsp;Mário A. Gonçalves ,&nbsp;Michelle Harris ,&nbsp;Diogo Silva ,&nbsp;Martin J. Whitehouse ,&nbsp;Damon A.H. Teagle","doi":"10.1016/j.lithos.2024.107913","DOIUrl":"10.1016/j.lithos.2024.107913","url":null,"abstract":"<div><div>We present sulfur mineralogy and isotope geochemistry from the gabbro transect of the Oman Drilling Project to unravel the sulfur cycle during hydrothermal alteration of the plutonic oceanic crust. The sheeted dike–gabbro transition (Hole GT3A) shows low sulfide‑sulfur concentrations (GT3A_median = 178 ppm, σ = 4873 ppm) but with great sulfur isotope variability (δ³⁴S = −12.8 to 14.4 ‰ V-CDT, weighted average + 5.8 ‰) and unusually heavy compositions relative to in-situ or ophiolitic crust. These features are consistent with abiogenic thermochemical sulfate reduction during intense hydrothermal alteration under greenschist facies conditions which formed a low-variance and relatively high-<em>f</em>S₂ assemblage of pyrite ± chalcopyrite ± bornite. The heaviest isotope compositions (+10 to +14 ‰) occur within 10 m of the uppermost gabbro screen suggesting focused fluid-rock exchange with isotope enrichment relative to seawater due to closed-system reservoir effects. The change in isotope compositions from +5 to 0 ‰ in the overlying sheeted dike reflect fluids gradually buffered by magmatic sulfur to signatures similar to the Oman Volcanogenic Massive Sulfide deposits. Hole GT3A represents a deep hydrothermal reaction zone with extensive S and base metal losses and incorporation of up to ∼80 % seawater-derived sulfate. The amount of Cu and Zn released in a 1 km³ crustal section similar to Hole GT3A is ∼3 times greater than the average contents of Omani VMS deposits.</div><div>The mid to lower crustal section (Holes GT2A and GT1A) mostly preserves MORB sulfur isotope compositions but highly variable sulfide‑sulfur contents (GT2A_median = 454, σ = 693 ppm, GT1A_median = 114, σ = 277 ppm). Away from fault zones, silicate microvein networks enabled variable sulfide and metal remobilization. Magmatic sulfides persist as remobilized remnants along with sulfidation reactions and mild isotopic enrichments (&lt;+2.7 ‰) in secondary sulfides (millerite + siegenite-polydimite_ss + pyrite). The mid-lower crustal section experienced redistribution of magmatic sulfur mixed with minor inputs of seawater-derived sulfur (&lt;10 %), under very low fluid/rock ratios and moderate sulfur fugacities, that chiefly preserved base metal abundances in secondary sulfides. The many faulted intervals present in Holes GT1A and GT2A record near complete sulfur and metal leaching of magmatic sulfides without the deposition of secondary sulfides, but preserve sulfate with a Cretaceous seawater sulfate‑sulfur isotope signature (+16.1 to +17.3 ‰). These structures are the expression of crustal scale channeled hydrothermal recharge fluid flow and record a previously unaccounted sulfur budget introduced in the deep crust.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"494 ","pages":"Article 107913"},"PeriodicalIF":2.9,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143161962","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":"Diachronous closure of the Mongol-Okhotsk Ocean (MOO) during Middle Mesozoic","authors":"Zhiqi Yu ,&nbsp;Huichuan Liu ,&nbsp;Jianwei Zi ,&nbsp;Wenqi Li ,&nbsp;Yiren Wang ,&nbsp;Yingying Wang ,&nbsp;Hanying Guo","doi":"10.1016/j.lithos.2024.107934","DOIUrl":"10.1016/j.lithos.2024.107934","url":null,"abstract":"<div><div>The Mongol-Okhotsk suture belt (MOSZ) is an integral part of the Central Asian orogenic belt (CAOB), the formation and evolution of MOSZ are significant factors contributing to the geotectonic framework of northeast Asia. However, there has been ongoing debate about the closure timing of MOO, particularly given the absence of petrogeological data in Northeastern Mongolia (NE Mongolia). This paper provides new zircon U<img>Pb dating, whole-rock elemental and Hf-Sr-Nd isotope data of two granodiorite plutons at Tsav (198 Ma) and Nomint (173–171 Ma), NE Mongolia, located in the central segment of the MOSZ. Both plutons are I-type granodiorites, but the Nomint granodiorites have high Sr/Y values, indicating an affinity to adakite. The 198 Ma Tsav granodiorites originated from partial melting of mafic lower crust within an Andean-type active continental margin setting, while the 173–171 Ma Nomint granodiorites derived from the thickened lower crust within the post-collisional setting. During the Early-Middle Jurassic, the central segment of MOO (C. MOO) might have closed. Combined with published data, we propose that the MOO closed through diachronous, southward subduction, with the closure of its eastern segment later than the western segment by 40 million years.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"494 ","pages":"Article 107934"},"PeriodicalIF":2.9,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143161968","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":"Mineralogy and geochemistry of a dunite dyke from the Monchetundra mafic Intrusion (Fennoscandian Shield): Evidence for petrogenesis and ophiolite-type affiliation","authors":"Victor V. Chashchin ,&nbsp;Yevgeny E. Savchenko","doi":"10.1016/j.lithos.2024.107939","DOIUrl":"10.1016/j.lithos.2024.107939","url":null,"abstract":"<div><div>Numerous dyke- and sill-like dunites have been discovered in the Paleoproterozoic Monchetundra mafic intrusion (MMI) located northeast of the Fennoscandian Shield. The subject of our study was a 35-m-thick dunite dyke discovered during exploration drilling of the low-sulfide Pt<img>Pd Loypishnyun deposit. These dunites contain a xenolith of the amphibolized orthopyroxenite and have undergone uneven, locally intense serpentinization, resulting in serpentinite formation. The host norites and orthopyroxenites underwent tectono-thermal transformations at contact with the dunites in the form of thin zones of serpentine-tremolite, tremolite, and cummingtonite rocks. These dunites are important because they record magmatic events after the formation of the MMI associated with the reactivation of the cratonic mantle. This study reports the mineral composition and the whole-rock major and trace element contents in 23 samples collected from dunite section and host rocks. The primary magmatic minerals in the dunites were olivine (Fo_86.7–92.7) with an elevated Ni content (up to 0.57 wt% NiO) and accessory chromite (60–85 %<em>Cr#</em>). Dunites are characterized by high magnesium (80–87 %<em>Mg#</em>), nickel (1590–2990 ppm Ni), chromium (up to 1.7 wt% Cr₂O₃), and iron oxidation coefficient (82–65 %<em>Fe</em>^<em>3+</em><em>#</em>). They are depleted in rare earth elements (1.3–0.43 ppm REE_tot), Ta, Sr, Zr, and Hf and are enriched in U, Th, and Ti. Based on <em>Cr#</em> (Chr)/Fo (Ol) and V/Al₂O₃ ratios, the parental magma of the dunites formed as a result of partial (30–40 %) melting of the fertile MORB mantle. Dunite crystallization occurred at 1355–1060 °C under the control of the FMQ buffer. Comparative analysis showed that the MMI dunites are similar in olivine composition to the alpine-type Pados intrusion and the Phanerozoic ophiolites of Oman, have a closer chromite composition to the Finnish Paleoproterozoic ophiolites, and generally similar in chemical composition to all except for lower SiO₂ and CaO contents in the MMI dunites. In the REE patterns, the MMI dunites were closest to those of Pados. We suggest that the formation of MMI dunite dykes was associated with the rise of parental melt through a crack network in the continental crust. This process is likely associated with extensional conditions resulting from the uplift of a mantle diapir. The results obtained indicate that MMI dunites are most likely ophiolite-type intrusive bodies and they characterize the setting of the initial stage of oceanic crust formation in the northeastern Fennoscandian Shield.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"494 ","pages":"Article 107939"},"PeriodicalIF":2.9,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143161970","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 of chromite deposit in the Sartohay ophiolite, NW China: Insights from chromite and its mineral inclusions","authors":"Qi-Qi Pan ,&nbsp;Jian-Guo Liu ,&nbsp;Xia Liu ,&nbsp;Ben-Xun Su ,&nbsp;Yan Xiao ,&nbsp;Qing-Shan Peng","doi":"10.1016/j.lithos.2024.107918","DOIUrl":"10.1016/j.lithos.2024.107918","url":null,"abstract":"<div><div>This study investigated chromite and its mineral inclusions from the Sartohay chromite deposit in NW China to explore the evolution of the parental magma and the genesis of the chromitites. Chromite grains in the Sartohay chromitite bodies have Cr# values (100 × Cr/(Cr + Al)) of 46.1–59.3, Mg# values (100 × Mg/(Mg + Fe²⁺)) of 47.3–70.5, and TiO₂ contents of &lt; 0.72 wt%, classifying them as typical high-Al variety. Numerous primary monomineralic and polymineralic inclusions have been identified within chromite, including olivine, clinopyroxene, orthopyroxene, amphibole, Na-plagioclase, and several less common minerals such as calcite, magnetite, magnesite, apatite, grossular, and corundum. The morphological features of these inclusions indicate that some were encapsulated as solid silicates, while others formed from melts trapped within chromite. The high Mg# characteristics of olivine and pyroxene inclusions, along with the zoning texture observed in elemental mapping images of amphibole inclusions, suggest that these inclusions have undergone elemental exchange with host chromite. The presence of crustal minerals, such as Na-plagioclase, indicates that crustal materials have been incorporated into the mantle through subduction recycling. The inferred parental melt compositions in equilibrium with chromite suggest that these chromitites likely formed from MORB-like melts. The interaction between this magma and harzburgites would generate a more silicic magma, from which high-Al chromitites formed.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"494 ","pages":"Article 107918"},"PeriodicalIF":2.9,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143162009","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":"A Precambrian basement beneath the King George Island (Antarctica Peninsula) revealed by zircon xenocrystals from Eocene to Miocene volcanic rocks","authors":"Hao Xing ,&nbsp;Junling Pei ,&nbsp;Liang Gao ,&nbsp;Jinfeng Wen ,&nbsp;Joaquín Bastías ,&nbsp;Xiatian Zhang","doi":"10.1016/j.lithos.2024.107899","DOIUrl":"10.1016/j.lithos.2024.107899","url":null,"abstract":"<div><div>Our knowledge of the Precambrian geological records of the deep crust beneath the Antarctic Peninsula is still sparse. The King George Island located in the northwestern part of the South Shetland Islands (Antarctic Peninsula) is mainly covered by the Cenozoic volcanic and intrusive rocks. This study presents new petrological, geochronological (LA-ICP-MS zircon U<img>Pb dates), and geochemical data from the King George Island volcanic rocks. The accidental discovery of zircon xenocrysts within these volcanic rocks offers valuable insights into the composition of the deep crust in the region. The zircon ages indicate the evidence of a Proterozoic to Cambrian basement in the King George Island. Among them, 56 zircons with 90–99 % concordance yielded ages ranging from 101 ± 1.7 Ma to 2407 ± 46 Ma. Major age peaks were identified approximately ca. 1.8–1.6 Ga, ca. 1.2–0.75 Ga, and ca. 0.55–0.5 Ga. These zircon xenocryst populations show age ranges and ε_Hf(t) values similar to those of basement rocks of the South America (Patagonia) continental block. This similarity suggests that the Proterozoic to Cambrian Patagonia crustal fragments may extend into the King George Island, South Shetland Islands (Antarctic Peninsula). Accordingly, we consider the paleogeographic position of the South Shetland Islands was probably at the southwestern end of the South America, forming the southwestern margin of Gondwana during the Early Mesozoic.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"494 ","pages":"Article 107899"},"PeriodicalIF":2.9,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143161543","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":"Decoding the evolution of Paleo-Tethys: Geochemical and geochronological reinterpretation of the Paleozoic ultra-mafic to felsic rocks in Northeast Iran","authors":"Hadi Karimi ,&nbsp;Hripsime Gevorgyan ,&nbsp;Lothar Ratschbacher ,&nbsp;Zhao Yang ,&nbsp;Axel Gerdes ,&nbsp;Abbas Etemadi","doi":"10.1016/j.lithos.2024.107916","DOIUrl":"10.1016/j.lithos.2024.107916","url":null,"abstract":"<div><div>The tectono-magmatic evolution of NE Iran records the Paleozoic–early Mesozoic formation and consumption of the Paleo-Tethys Ocean. Debates focus on how the regionally-distributed basement exposures and their diverse evolution settings—such as rifting, oceanic-plateau formation, arc magmatism, and collision—are connected. The compositionally diverse meta-igneous rocks comprise the early Paleozoic Neyshabur complex, the Mississippian–Cisuralian Vakilabad complex (‘Mashhad metamorphics’), the Cisuralian Fariman complex, and the Frasnian–Permian Darreh Anjir complex; the age assignment is preliminary. Combining new field, geochemical, and geochronologic data with published ones, we specify the connection and evolution of these complexes. The Neyshabur complex has dominantly alkaline and subordinate tholeiitic rocks dated at 490–435 Ma (U<img>Pb zircon). In terms of high field strength element rations, such as Nb/Y vs. Zr/Y, they record long-lasting, mantle-plume triggered continental rifting along the northern Gondwana margin. A ∼ 364 Ma (U<img>Pb apatite) age dates hydrothermal alteration and deformation, possibly recording the integration of this complex into an oceanic accretionary wedge. Circa 195 Ma (Ar/Ar amphibole and plagioclase) metamorphism dates collisional-wedge formation, i.e., the collision of the Central Iranian (Gondwana) and Turan Blocks (Eurasia). In the Vakilabad complex, 281–268 Ma (Ar/Ar amphibole) ages of meta-komatiite/gabbro match those (∼276 Ma; cumulate) of ultra-mafic to mafic rocks of the southern Fariman complex; a ∼ 320 Ma (U<img>Pb titanite) age of tholeiitic basalt in the Vakilabad complex supports the presence of older rocks, suggested by Carboniferous radiolarian cherts. 188–183 Ma (Ar/Ar mica) metamorphism again dates collisional-wedge formation. The Darreh Anjir-complex rocks with a supra-subduction zone signature record subduction beneath an oceanic plateau within the Paleo-Tethys Ocean. The Vakilabad and the southern Fariman complexes comprise an oceanic plateau built by a mantle plume. This plateau accreted to the hanging-wall plate prior to the terminal collision, detached from the lower plate, blocked the subduction, and caused slab break-off and slab-window formation; the slab window allowed plume material to ascend. The northern Fariman complex documents this process: the rising plume material— depleted by the extraction of OIB-like magma—mixed with fluids from the subducting slab, creating boninite-like magmas. Calc-alkaline andesitic magmas, likely originating from the mantle wedge, coexisted with the OIB-like and boninite-like magmas. Our study provides an evolution model that integrates the various complexes of NE Iran into a common Late Cambrian to Late Triassic evolution of the Paleo-Tethys.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"494 ","pages":"Article 107916"},"PeriodicalIF":2.9,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143161551","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":"Calcium and iron isotope fractionation during felsic magma differentiation","authors":"Qiu-Yun Guan ,&nbsp;Jin-Xiang Li ,&nbsp;Ya-Li Sun ,&nbsp;Shi-Lei Tang ,&nbsp;Noreen J. Evans ,&nbsp;Zhao-Feng Zhang ,&nbsp;Li-Yun Zhang ,&nbsp;Fu-Long Cai ,&nbsp;Wei-Ming Fan ,&nbsp;Lin Ding","doi":"10.1016/j.lithos.2024.107893","DOIUrl":"10.1016/j.lithos.2024.107893","url":null,"abstract":"<div><div>Stable calcium (Ca) and iron (Fe) isotopes could provide a new way to investigate granite petrogenesis, and their isotope fractionation mechanisms in felsic magmas have been increasingly understood through continuous efforts in recent years. However, comprehensive Ca and Fe isotope fractionation during highly fractionated magmas is still unclear. This study presents Ca and Fe isotope data for some fractionated granites from Southern Myanmar. The δ^56/54Fe values of the less fractionated Eocene granites range from 0.11 ± 0.03 ‰ to 0.23 ± 0.04 ‰. The highly fractionated Late Cretaceous and Paleocene granites clearly exhibit 0.15 ‰ and 0.42 ‰ variations in δ^56/54Fe values, respectively. These δ^56/54Fe values are negatively correlated with those of Fe₂O_3T, TiO₂ contents and (La/Yb)_N ratios, suggesting that more evolved melts are enriched in heavy Fe isotopes, primarily as a result of fractional crystallization of Fe-rich minerals enriched in light Fe isotopes (e.g., biotite and ilmenite). Some Late Cretaceous granites with low Nb/Ta and Zr/Hf ratios display relatively low δ^56/54Fe values, which may be modified by exsolved fluids enriched in light Fe isotopes. Moreover, the δ^44/40Ca values of the Late Cretaceous, Paleocene, and Eocene granites range from 0.71 ± 0.07 ‰ to 0.90 ± 0.06 ‰, 0.62 ± 0.08 ‰ to 0.89 ± 0.06 ‰, and 0.66 ± 0.06 ‰ to 0.75 ± 0.05 ‰, respectively. Most of the studied granites have relatively consistent Ca isotopic compositions with those of the continental crust. Combined with high δ^44/40Ca values (up to 0.90 ‰), the studied granites have a weakly negative correlation between δ^44/40Ca values and Eu/Eu^⁎ ratios. This evidence suggests that fractional crystallization of plagioclase with light Ca isotopes may also be a reason for Ca isotope fractionation during felsic magma differentiation, in addition to crustal magma sources and crustal contamination. Additionally, a Late Cretaceous granite with a high (Dy/Yb)_N ratio has the lowest δ^44/40Ca value (0.52 ± 0.06 ‰), possibly reflecting the presence of residual garnet in the source. The affirmation of significant Ca and Fe isotope fractionation in highly evolved melts strengthens the utility of Fe and Ca isotopes as tracers of magma differentiation.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"494 ","pages":"Article 107893"},"PeriodicalIF":2.9,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143161961","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":"Origin and evolution of sub-caldera magmatic systems before and during the caldera-forming eruptions of the Furongshan caldera, SE China","authors":"Ming-Lu Li ,&nbsp;Zhen-Yu He ,&nbsp;Tian-Yu Lu ,&nbsp;Li-Li Yan","doi":"10.1016/j.lithos.2025.107974","DOIUrl":"10.1016/j.lithos.2025.107974","url":null,"abstract":"<div><div>The formation of collapse caldera is commonly associated with large-scale eruptions of silicic magmas, where the magma reservoirs generally undergo long-term accumulation and maturation processes before the caldera-forming eruptions. However, the pre-caldera eruptions have been less documented, since such eruption products are usually concealed by subsequent collapse and filling. The Furongshan caldera in SE China preserves the records of both the pre-caldera and caldera-forming eruption products, providing vital insights into the evolution of the magmatic systems from pre-caldera to caldera-forming eruptions. The pre-caldera volcanic rocks are characterized by small-volume dacite with relatively low SiO₂ contents (64–65 wt%), while the caldera-forming volcanic rocks are relatively large-volume crystal-rich tuff with high crystal contents (35–45 vol%) and relatively high SiO₂ contents (70–78 wt%). LA-ICP-MS zircon U-Pb dating results show that the age of pre-caldera dacite is 151 ± 1 Ma, and the age of caldera-forming crystal-rich tuff is 148 ± 1–144 ± 1 Ma, which indicates a prolonged evolution of the caldera magmatic systems. Zircon trace elements of the caldera-forming crystal-rich tuff show relatively low Ti contents and Eu/Eu* ratios, consistent with relatively low magma temperatures and high magmatic differentiation. The pre-caldera dacite and the caldera-forming crystal-rich tuff further show different zircon Hf isotopic compositions, with ε_Hf(<em>t</em>) values of −8.7 to −3.5 and −14.2 to −5.5, respectively, indicating higher crustal contributions in the magma of the caldera-forming crystal-rich tuff. We suggest that from the pre-caldera to caldera-forming eruptions at the Furongshan caldera, the contribution of crustal materials in the magma systems increased, and the magmas also gradually evolved, which well recorded the maturation process of the magmatic system of caldera-forming eruption. The eruption of caldera-forming crystal-rich tuff may be related to magma recharge and associated mush rejuvenation within the magma reservoirs.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"496 ","pages":"Article 107974"},"PeriodicalIF":2.9,"publicationDate":"2025-01-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143320755","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":"Laterally differential composition and dynamics of a continental collision belt: Evidence from the North Qaidam orogenic system (western China)","authors":"Hao-Qin Sun,&nbsp;Qing Xiong,&nbsp;Qiang Ma,&nbsp;Si-Yi Cao,&nbsp;Xiang Zhou,&nbsp;Hong-Kun Dai,&nbsp;Wei Wang,&nbsp;Jian-Ping Zheng","doi":"10.1016/j.lithos.2025.107968","DOIUrl":"10.1016/j.lithos.2025.107968","url":null,"abstract":"<div><div>Revealing the large-scale, along-strike variations of composition and evolution of continental collisional belts remains a challenging task. Here, we report new zircon U-Pb ages, Lu-Hf isotopes and whole-rock major elements of granitoids, combined with a synthesis of published geochemical data of magmatic rocks across the whole North Qaidam collisional orogenic system (western China). Geochemical comparison and mapping reveal a pronounced dichotomy between the eastern and western segments during the ∼460–360 Ma orogeny. We observed that the eastern magmatism was continuous, with the magma source transition from mixed mantle-crust reservoirs to a solely exhumed continental crust at ∼420–410 Ma. A gradual increase in asthenosphere-derived magmatism triggered a magmatic burst at ∼400–380 Ma, followed by the orogen-collapse-related mafic magmatism at ∼380–360 Ma. In contrast, the western segment experienced a two-phase magmatism interrupted by a hiatus at ∼400–380 Ma. The earlier phase originated mainly from the moderately evolved and fractionated felsic magmas with variable older crustal components, while the later switched to asthenosphere-sourced mafic magmatism similar to that in the east. These contrasting features suggest that a relatively flat continental slab in the west gradually attached onto the overlying plate during ∼460–400 Ma, completely shutting down the western magmatism during ∼400–380 Ma. Meanwhile, the oceanic and continental slabs in the east progressively steepened until the slab broke off at ∼400–380 Ma. The whole orogenic root was finally removed together at ∼380–360 Ma. This study shows that slab tearing and differential slab behaviors may be a common feature of convergent and collisional orogens.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"496 ","pages":"Article 107968"},"PeriodicalIF":2.9,"publicationDate":"2025-01-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143321012","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":"Multi-stage continental crust maturation in accreted oceanic terranes: Evidences from granitoids in the Qinling Orogen, Central China","authors":"Yadi Zhuang ,&nbsp;Wenxiang Zhang ,&nbsp;Yujie Zhao ,&nbsp;Guangyan Zhou ,&nbsp;Yuanbao Wu","doi":"10.1016/j.lithos.2025.107969","DOIUrl":"10.1016/j.lithos.2025.107969","url":null,"abstract":"<div><div>Accreted oceanic arc terranes are crucial sites for net continental crust growth. It is intriguing how the mafic oceanic arcs can subsequently evolve into high-Si and K-rich mature continental crust. The granitoid Xizhuanghe and Dongzijie plutons display enriched geochemical composition and occur in the same oceanic arc unit of the Paleozoic Qinling orogen. They provide an ideal opportunity to reveal the mechanism for transforming mafic oceanic arcs to continental crust. The Xizhuanghe and Dongzijie granites have zircon U<img>Pb ages of ca. 460 Ma and 454 Ma, respectively, after the collision between the Erlangping and North Qinling units. Geochemically, both of them display low Mg# (38.9–45.4 vs. 18.9–43.4) values and arc-type trace element distribution patterns. According to the different K₂O/Na₂O ratios, the Xizhuanghe pluton is relatively sodic I-type granites, while the Dongzijie pluton belongs to typical potassic species. They are characterized by depleted Sr-Nd-Hf compositions (Xizhuanghe: ⁸⁷Sr/⁸⁶Sr_i = 0.704171–0.704692, ε_Nd(t) = +1.68 ∼ +2.23, zircon ε_Hf(t) = +5.9 ∼ +9.8; Dongzijie: ⁸⁷Sr/⁸⁶Sr_i = 0.694356–0.705627, ε_Nd(t) = −0.94 ∼ +1.37, zircon ε_Hf(t) = +8.1 ∼ +11.9) and zircon δ¹⁸O values (Xizhuanghe: 4.31–5.15 ‰; Dongzijie: 3.30–5.19 ‰) lower than those of normal mantle zircon, indicating that the mafic precursors of the two plutons might be the Erlangping lower oceanic crust, which might be heterogeneously modified in a supra-subduction zone and have experienced high-temperature hydrothermally alteration with seawater. We suggest that the Xizhuanghe pluton can directly be produced by partial melting of such mafic oceanic crust, while the Dongzijie pluton needs additional fractionation process: dehydration melting of sodic felsic rocks generated by partial melting of the enriched lower oceanic crust. Our finding highlights the significance of the enriched oceanic crust and multi-stage differentiation within oceanic arc crust plays an important role for progressively crust maturation in accretionary orogens.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"496 ","pages":"Article 107969"},"PeriodicalIF":2.9,"publicationDate":"2025-01-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143320149","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}