Lithos最新文献

{"title":"Geochemical study of UHP serpentinites in southwestern Tianshan, China and its implications for trace elements deep recycling","authors":"Tingting Shen ,&nbsp;José Alberto Padrón-Navarta ,&nbsp;Thomas Bader ,&nbsp;Congcong Lin ,&nbsp;Tian Qiu ,&nbsp;Jingsui Yang","doi":"10.1016/j.lithos.2024.107867","DOIUrl":"10.1016/j.lithos.2024.107867","url":null,"abstract":"<div><div>Serpentinites play a crucial role in the recycling of elements and volatiles in subduction zones. We studied the geochemistry of Changawuzi serpentinites from Chinese southwestern Tianshan, which underwent ultrahigh-pressure (UHP) metamorphism. The bulk rock compositions of the serpentinites suggest that Changawuzi serpentinites originated from a variably depleted mantle and were subsequently enriched in fluid-mobile elements (FMEs) during initial serpentinization. Integrated analyses of trace element concentrations (Cs, U, As, and Sb), Sr–Nd–Pb isotopic compositions, and geological context collectively indicate that serpentinization likely occurred within the interior of the subducted slab. During the early stages of subduction, the concentrations of rare earth elements (REE), high-field-strength elements (HFSE), and other trace elements (such as Cs, Rb, Ba, Th, and U) decrease from low-grade lizardite to high-grade antigorite, as well as from primary clinopyroxene to metamorphic diopside. FMEs, particularly boron (B), are significantly enriched in lizardite, and the majority are liberated during prograde subduction, resulting in the metamorphic transformation from lizardite to antigorite. The uptake and variation of Sb and As in Changawuzi serpentinites are relatively minor. At peak metamorphic conditions, olivine, Ti-chondrodite and Ti-clinohumite become the main minerals hosting trace elements (such as REE, B, Sb, As and Li) that were released during partial antigorite dehydration and clinopyroxene re-equilibration. Ti-chondrodite/Ti-clinohumite as isolated grains or as lamellae within metamorphic olivine have the potential to carry HFSE, FMEs (particularly B and Li) and H₂O into the deeper mantle beyond the dehydration of serpentinites, potentially impacting arc magmatism and the global cycling of these elements.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"492 ","pages":"Article 107867"},"PeriodicalIF":2.9,"publicationDate":"2024-11-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142703894","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":"U-Pb ages and Hf isotopic composition of detrital zircon in western Algarve Triassic sandstone (SW Iberia): Implications for crustal evolution, provenance, and paleogeography","authors":"Manuel Francisco Pereira,&nbsp;Cristina Gama","doi":"10.1016/j.lithos.2024.107871","DOIUrl":"10.1016/j.lithos.2024.107871","url":null,"abstract":"<div><div>The Triassic paleogeographic configuration before the Central Atlantic Ocean's opening and the Pangea's breakup establishes that Iberia was close to North America and North Africa. We present U<img>Pb and Hf isotope data of Triassic siliciclastic rocks of the Western Algarve basin (Southwest Iberia, Portugal) to draw inferences on their provenance to define the crustal evolution of the potential sources. Detrital zircon age populations of five samples of Triassic sandstones (68–80 % Neoproterozoic; 5–23 % Paleoproterozoic; 5–14 % Mesoproterozoic; &lt;5 % Archaen and &lt; 4 % Paleozoic) differ significantly from those of the underlying Carboniferous turbidites of the South Portuguese Zone suggesting provenance from outside present-day SW Iberia. Hf isotope signatures of the zircon grains from the western Algarve Triassic sandstones unravel a complex crustal evolution characterized by successive cycles of input of juvenile magmas and magmas derived from the reworking of older crust. Archean detrital zircon grains with positive εHf(t) values and model ages of 3.1–3 Ga indicate juvenile crust formation (Leonian event), while a grain dated at ca. 2.6 Ga showing negative εHf(t) values and model ages of 3.1 Ga suggests that the Archean crust became reworked later (Liberian event). Zircon grains dated between 2.4 and 2.5 Ga having positive to slightly negative εHf(t) values and model ages of 3.3–2.6 Ga model ages correspond to magmatism older than the Eburnean event known in the Reguibat shield, involving a juvenile component mixed with variable proportions of reworked Archean crust. Younger Paleoproterozoic grains (ca. 2.10 to 2.05 Ga; Eburnean-Birimian event) having positive εHf(t) values and model ages of 2.3–2.1 Ga and negative εHf(t) values and model ages of 3.6–2.6 Ga, also indicate interaction of juvenile sources with mixing of old crust. Mesoproterozoic grains show positive εHf(t) values and model ages of 2.3–2.1 Ga, suggesting juvenile crust formation and reworking of the Eburnean crust. Neoproterozoic (ca. 695–555 Ma) detrital zircon with positive εHf(t) values and model ages of 0.76–0.58 Ga point to juvenile crust formation (i.e. Cadomian/Pan-African and Avalonian arcs). They also have negative εHf(t) values in the range − 21.6 to −11.7 and model ages of 3.2–2.1 Ga, suggesting reworking of older crust. In summary, the εHf(t) values and U<img>Pb age pattern of the zircon grains from the Triassic siliciclastic rocks are similar to NW Africa and North America potential sources. Still, there is a notable gap in juvenile crust production during the Siderian in the peri-Eastern Laurentia, Avalonia, and Ganderia potential sources unknown in NW Africa. The lack of ca. 525–380 Ma and ca. 380–330 Ma detrital zircon in the western Algarve Triassic sandstones makes it challenging to admit an Atlantic margin of North America and SW Iberia provenance.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"490 ","pages":"Article 107871"},"PeriodicalIF":2.9,"publicationDate":"2024-11-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142658300","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":"Zinc and iron isotopic compositions of Cenozoic basalts in Inner Mongolia: New insights into deep carbon recycling related to Paleo-Asian slab subduction","authors":"Zhao-Xue Wang ,&nbsp;Tianhao Wu ,&nbsp;Sheng-Ao Liu","doi":"10.1016/j.lithos.2024.107866","DOIUrl":"10.1016/j.lithos.2024.107866","url":null,"abstract":"<div><div>The origin of Cenozoic basalts in Inner Mongolia has been debated in recent years. Although the heavier-than-mantle zinc isotopic compositions indicate recycled carbonate in their sources, the recycled carbonate has been attributed to two different subducting oceanic slabs (Paleo-Asian vs. Paleo-Pacific). To further address this issue, Cenozoic basalts located in the west of the North-South Gravity Lineament (NSGL) in Inner Mongolia are investigated, and the sampling profile is approximately parallel to the NSGL (i.e., from southwest to northeast; SW-NE). These basalts have notably heavier zinc (δ⁶⁶Zn = 0.47–0.52 ‰) and iron (δ⁵⁶Fe = 0.18–0.24 ‰) isotopic compositions than those of the mantle, which cannot be interpreted by magmatic processes (differentiation and partial melting). Instead, the involvement of recycled carbonates in sources is a viable explanation for the high δ⁶⁶Zn characteristics, supported by high P₂O₅ contents and low Hf/Hf*. In addition, samples with high δ⁵⁶Fe also display high Fe/Mn (69–81) related to Cenozoic basalts from the east of the NSGL, indicating the existence of a pyroxenite component in sources in addition to carbonated peridotites. Combining with literature data, we found that basalts distributed in the SW-NE direction in Inner Mongolia have similarly heavy Zn and Fe isotopic compositions. This provides further constraints that mantle carbonate metasomatism in the west of the NSGL was most likely to have been caused by southeastward subduction of the Paleo-Asian oceanic slab, instead of northward subduction of the Paleo-Asian oceanic slab or subduction of the Paleo-Pacific oceanic slab.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"492 ","pages":"Article 107866"},"PeriodicalIF":2.9,"publicationDate":"2024-11-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142703893","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":"Cumulate granites and extraction of interstitial high-silica melts: The case of leucogranites in the northern Tibetan Plateau","authors":"Peng Wang ,&nbsp;Xiangsong Wang ,&nbsp;Guochun Zhao ,&nbsp;Roberto F. Weinberg ,&nbsp;Qian Liu","doi":"10.1016/j.lithos.2024.107869","DOIUrl":"10.1016/j.lithos.2024.107869","url":null,"abstract":"<div><div>Accumulation of crystals and extraction of melt play a crucial role in generating diverse intermediate to felsic rocks. However, the process of separating crystals and melt in granitic rocks with high silica content remains a topic of debate. In this paper, detailed petrographic, geochemical, and isotopic observations reveal that the ca. 424 Ma Aoyiyayilake S-type granitic batholith, located in Eastern Kunlun of northern Tibetan Plateau, is composed of low- and high- SiO₂ units that resulted from crystal accumulation and melt extraction respectively. Petrographically, the presence of fractures filled with quartz and oligoclase indicates compaction and fracturing occurred in the presence of melt, resulting in the extraction of melts to produce the high-SiO₂ granites. Geochemically, the high-SiO₂ granites have higher depletions in Eu, lower light rare earth elements, large ion lithophile elements (e.g., Ba and Sr) and P content than the low-SiO₂ granites. This is due to the fractional crystallization of rock-forming minerals (e.g., oligoclase and orthoclase) and accessory minerals (e.g., apatite), consistent with the proportions of minerals in the two units, e.g., ∼0.3 % apatite in the low-SiO₂ granites and undetected apatite in the high-SiO₂ granites. Isotopically, the high-SiO₂ granites display lower δ¹¹B of −16.1 ‰ and − 17. compared to −15.7 ‰ to −7.14 ‰ in low-SiO₂ granite, which is attributed to the crystallization of muscovite. These characteristics serve as significant indicators of efficient magma fractionation during the formation of high-SiO₂ granites.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"492 ","pages":"Article 107869"},"PeriodicalIF":2.9,"publicationDate":"2024-11-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142720899","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":"Magmatic differentiation of peralkaline granites: Constraints from iron isotope fractionation between Fe-bearing minerals","authors":"De-Hong Du ,&nbsp;Xiao-Lei Wang ,&nbsp;Hang Xu ,&nbsp;Shuo Wang ,&nbsp;Ying-Ze Zhang ,&nbsp;Weiqiang Li","doi":"10.1016/j.lithos.2024.107863","DOIUrl":"10.1016/j.lithos.2024.107863","url":null,"abstract":"<div><div>Iron isotopes have been found useful in tracing magmatic processes of calc-alkaline granitic magmas, but its application in peralkaline granitic systems is hampered by the lack of information regarding the Fe isotope fractionation factors between alkali-rich ferromagnesian silicate minerals and Fe<img>Ti oxides. To better understand the behavior of Fe isotopes during peralkaline magma differentiation, we carried out high-precision Fe isotope analyses on peralkaline and associated metaluminous high-silica granite rocks and Fe-bearing minerals separated from the rocks in Zhoushan archipelago, southeast China. The Fe-bearing mineral show a large dispersion in Fe isotope compositions, with δ⁵⁶Fe ranging from 0.03 ‰ to 0.70 ‰, following the sequence of K-feldspar ≥ magnetite &gt; aegirine &gt; arfvedsonite &gt; ilmenite. The δ⁵⁶Fe differences between the mineral pairs are relatively consistent. Based on the magmatic temperatures defined by quartz-zircon oxygen isotopic geothermometer, the temperature-dependent equilibrium Fe isotope fractionation functions between following mineral pairs are obtained: Δ⁵⁶Fe_{aegirine-arfvedsonite} = 0.20 (± 0.07) × 10⁶/T², Δ⁵⁶Fe_{magnetite-arfvedsonite} = 0.38 (± 0.06) × 10⁶/T², and Δ⁵⁶Fe_{magnetite-aegirine} = 0.16 (± 0.04) × 10⁶/T². The bulk peralkaline granites have variable but generally high δ⁵⁶Fe values ranging from 0.28 ± 0.03 ‰ to 0.62 ± 0.04 ‰, with a mean of 0.42 ± 0.09 ‰ (1SD), which are higher than those of the associated metaluminous granitic samples (δ⁵⁶Fe = 0.22 ± 0.05 ‰, 1SD). Furthermore, δ⁵⁶Fe values of the peralkaline granites are negatively correlated with Sm/Yb and MnO, consistent with removal of isotopically light Fe-enriched arfvedsonite, implying that peralkaline granites experienced extensive magma differentiation regardless whether they were derived from differentiation of mantle-derived basaltic melts or partial melting of curst sources. Our results highlight a large Fe isotope fractionation between alkali ferromagnesian silicates and oxides, confirming Fe isotopes as a potential tool in tracking the differentiation processes of peralkaline magmas.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"490 ","pages":"Article 107863"},"PeriodicalIF":2.9,"publicationDate":"2024-11-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142658304","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":"Temporal variation in oxygen isotopes of peraluminous granites derived from sedimentary sources","authors":"Claire E. Bucholz,&nbsp;Juan D. Hernández-Montenegro","doi":"10.1016/j.lithos.2024.107864","DOIUrl":"10.1016/j.lithos.2024.107864","url":null,"abstract":"<div><div>The oxygen isotopic composition of magmatic rocks provides critical constraints on the contributions of crust versus mantle in their genesis. Peraluminous granites derived from partial melting of sedimentary rocks offer a unique archive to examine how the oxygen isotope composition of sedimentary rocks recycled into magmas has changed throughout Earth history. In this study, we explore this record through a two-pronged approach. First, we compile a comprehensive dataset of oxygen isotope bulk-rock and mineral analyses from globally distributed peraluminous granites and volcanic rocks ranging in age from 3.2 billion years to 6 million years. Second, we model the isotopic fractionation between sedimentary source rocks and derivative melts, as well as minerals in equilibrium with the melt during anatexis. Our compilation demonstrates a progressive increase in δ¹⁸O values of zircon and garnet from the Archean to Paleoproterozoic and again in the latest Neoproterozoic to Phanerozoic. Specifically, the average δ¹⁸O of zircon from peraluminous granites increases from 6.7 ± 1.0 ‰ to 9.5 ± 0.8 ‰ at ∼ 2.35 Ga, followed by another increase to 10.4 ± 0.7 ‰ after 600 Ma (errors are ± 1 s.d.). These observations align with the sedimentary rock record which suggests enhanced weathering and clay deposition resulting from tectonic and biological forcings. Furthermore, the increase in δ¹⁸O of peraluminous granites broadly mirrors similar secular increases in the δ¹⁸O values of siliciclastic sedimentary rocks. However, using our modeled fractionations between melt and source rock, the reconstructed source-rock δ¹⁸O values capture only the lower end of the siliciclastic sedimentary rock range, suggesting that sedimentary rocks recycled into magmas have, on average, lower δ¹⁸O values than coeval clay-rich shales. We propose that any global analyses of oxygen isotopes in magmatic rocks or zircon should use the average values of calculated source rocks for peraluminous granites in defining crustal contributions. Furthermore, our study highlights the broader implications of the observed trends, including the progressive contamination of the mantle and elevation of its δ¹⁸O values.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"492 ","pages":"Article 107864"},"PeriodicalIF":2.9,"publicationDate":"2024-11-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142703910","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":"Pressure-Temperature-time paths from metapelites reveal Neoproterozoic continental crust underthrusting related to the West Gondwana amalgamation","authors":"Alice Westin ,&nbsp;Mahyra Tedeschi ,&nbsp;Mario C. Campos Neto ,&nbsp;George L. Luvizotto ,&nbsp;Rafael G. Motta ,&nbsp;Augusto G. Nobre ,&nbsp;Rômulo A. Ando","doi":"10.1016/j.lithos.2024.107865","DOIUrl":"10.1016/j.lithos.2024.107865","url":null,"abstract":"<div><div>In this contribution, we employed a petrochronological approach to investigate the tectonometamorphic evolution of Al-rich garnet-staurolite and garnet-staurolite-kyanite (biotite- and plagioclase-free) metapelites of the southernmost portion of the Neoproterozoic Brasília orogen. We have reconstructed the first prograde to peak pressure-temperature-time (P-T-t) paths reported for metamorphic units of the area, by combining petrographic analyses, quantitative compositional mapping of major elements, phase equilibrium modeling, and EPMA Th–U–Pb monazite chemical dating. The metamorphic reactions involved in the prograde metamorphic evolution are discussed, including the effects of garnet fractionation, exhaustion of reactants, and re-equilibration reactions on the major-element composition of garnet porphyroblasts, and their influence on <em>P-T</em> condition estimates. Raman spectroscopy on carbonaceous material (RSCM) thermometry provided insights into the synkinematic retrograde path. A steep prograde path marked by two stages is recorded by the garnet porphyroblasts of garnet-staurolite-muscovite (±kyanite) schists: (i) 555–585 °C and 0.60–0.90 GPa; (ii) 590–635 °C and 1.0–1.4 GPa. Monazite crystals record the prograde to peak path from <em>ca.</em> 630–625 Ma to <em>ca.</em> 605–595 Ma. Matrix graphite crystals suggest post-peak cooling to 400–500 °C concurrent with the late stages of development of the main foliation. The reconstructed P-T-t paths indicate an intermediate d<em>T</em>/d<em>P</em> metamorphism, and a burial rate of ∼0.55 km/Ma, with garnet compositional zoning suggesting that the high-pressure P-T-t path resulted from a single metamorphic event. The corresponding geothermal gradients, and <em>in-situ</em> ages, combined with regional evidence, suggest that peak metamorphic conditions were attained during collisional underthrusting of the continental crust related to the West Gondwana amalgamation.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"490 ","pages":"Article 107865"},"PeriodicalIF":2.9,"publicationDate":"2024-11-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142658369","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":"Tracking HFSE associated with high salinity fluid during HP metamorphism in the Zavkhan Terrane, Western Mongolia","authors":"Manzshir Bayarbold ,&nbsp;Atsushi Okamoto ,&nbsp;Masaoki Uno ,&nbsp;Otgonbayar Dandar ,&nbsp;Mayuko Fukuyama ,&nbsp;Geri Agroli ,&nbsp;Noriyoshi Tsuchiya","doi":"10.1016/j.lithos.2024.107853","DOIUrl":"10.1016/j.lithos.2024.107853","url":null,"abstract":"<div><div>Garnets often exhibit high concentrations of heavy rare-earth elements, which provide crucial insights into element mobility and fluid dynamics during metamorphism. This research reports on the distributions of trace and major elements in garnets from the Khungui eclogite of the Zavkhan Terrane in Western Mongolia. Within the eclogite sample, two types of garnets were identified, featuring dissimilar microstructures and compositional zoning: aggregate-type garnet with asymmetric zoning (Grt1) and euhedral garnet with concentric zoning (Grt2). Previous studies determined that Grt2 formation occurred in the pre-eclogite stage to eclogite facies (2.1–2.2 GPa and 580–610 °C), associated with the infiltration of high-saline fluids. The hexagonal-shaped pseudomorphs of Ti-bearing minerals associated with Grt1 suggest that the nucleation of titanite and garnet was simultaneously accelerated by the destabilization of Ti-augite during pre-eclogite metamorphism. This process could have contributed to the formation of aggregation textures, where Ti-bearing minerals are closely associated with Grt1 in the Khungui eclogite. Based on major divalent elemental composition zoning and trace element characteristics, both Grt1 and Grt2 in the Khungui eclogite are formed simultaneously from the pre-eclogite to eclogite stages. The cores (high Fe + Mg + Mn; Y + REE) of Grt1 and Grt2 are attributed to Rayleigh fractionation or a diffusion-limited uptake process. In contrast, the growth mechanisms of the Grt1 rim and Grt2 rim are distinct during the eclogite stage. The Grt1 rim is explained by a dissolution–reprecipitation, which resulted in the atoll texture observed in Grt1. The Grt2 rim (high Ca; low Y + REE) grew through a mechanism consistent with that of the Grt2 core. The major and trace element zonings of these garnets provide insights into element mobility related to Ti-bearing minerals and infiltration of high salinity fluids at different stages: (1) the mobilization of Ti and V increased under eclogite facies conditions (growth stage of garnet) compared to the pre-eclogite stage, with the mobility of Ti, Nb, Ta elements being pronounced under the exhumation stage (Rt–Ilm–Ttn2), possibly because of the infiltration of high-saline fluids and an increase in temperature, and (2) post-growth compositional modification of Grt1 was induced by a localized transport of Fe, Mg, Mn, and Ca elements in response to the replacement of ilmenite by titanite during decompression (0.1–0.5 GPa and 421–534 °C). The contrasting zoning of garnet in Khungui eclogite indicates dissimilar scales of element mobility under eclogite facies conditions (over a thin-section scale) and during decompression (up to several centimeters or beyond).</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"490 ","pages":"Article 107853"},"PeriodicalIF":2.9,"publicationDate":"2024-11-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142658368","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":"Triassic–Jurassic alkaline magmatism in the Ivrea-Verbano Zone, Southern Alps: A zircon perspective on mantle sources and geodynamic significance","authors":"Mattia Bonazzi ,&nbsp;Abimbola C. Ogunyele ,&nbsp;Tommaso Giovanardi ,&nbsp;Maurizio Mazzucchelli ,&nbsp;Alessandro Decarlis ,&nbsp;Alessio Sanfilippo ,&nbsp;Alberto Zanetti","doi":"10.1016/j.lithos.2024.107854","DOIUrl":"10.1016/j.lithos.2024.107854","url":null,"abstract":"<div><div>The Ivrea-Verbano Zone (IVZ; western Southern Alps) consists of a distinctive sequence of the lower continental crust of the Adriatic plate, extending down to the subcontinental lithospheric mantle. It is characterized by a large variety of intrusive bodies of variable geochemical composition and age, offering a unique insight into the evolution of mantle-derived magmatism in post-collisional and extensional geodynamic settings. In this study, we characterize a suite of alkaline dykes intruding a mantle massif – the Finero Phlogopite Peridotite in northern IVZ. These dykes include zircon-bearing diorites and anorthosites, mainly composed by HFSE-rich amphibole and phlogopite, albite (&gt;90 vol% in anorthosites) and apatite. Zircon, monazite, ilmenite, titanite, Nb-rich oxides, and carbonates are common accessory minerals. Additionally, a “composite” diorite dyke containing both HFSE-rich and HFSE-poor amphiboles was investigated. The study is aimed at providing new trace element, U-Pb geochronological and Lu-Hf isotopes dataset on zircon from these alkaline dykes, to refine the understanding of their mantle source characteristics, emplacement age and geodynamic implications. The trace element composition of zircons from the studied dykes points to segregation from melts with alkaline to ultra-alkaline affinity. Concordia U-Pb ages of zircon from the alkaline diorite dykes span from 221 to 191 Ma, which are interpreted as the result of multiple crystallization/recrystallization stages related to different magmatic pulses. Conversely, zircon from anorthosite and composite diorite dykes yield a narrow time range of 198–202 Ma, highlighting the occurrence of a magmatic pulse around ca. 200 Ma. The εHf_(t) values (+13.4 to +5.7) of zircon from the alkaline diorite dykes are significantly more positive compared to the values in those from anorthosite and composite diorite dykes (+4.2 to −0.4), suggesting that the parental melts were derived from heterogeneous asthenospheric mantle sources with low to moderate amount of recycled continental crust components. Our data and reappraisal of the literature indicate that the IVZ experienced a protracted period of alkaline magmatism from ca. 235 Ma to 185 Ma. The melts migrated along mantle shear zones during the Triassic-Jurassic lithospheric extension. Different pulses of alkaline magmatism were associated with relevant extensional tectonic stages recorded by the continental crust, presumably triggering a passive uplift of heterogenous asthenospheric reservoirs over a front of at least 500 km. This tectono-magmatic cycle is a precursor to the focused rifting stage which caused the opening of the Jurassic Alpine Tethys, enhancing Pangea fragmentation.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"490 ","pages":"Article 107854"},"PeriodicalIF":2.9,"publicationDate":"2024-11-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142658302","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":"Paleoproterozoic sediment-derived magmas reveal a late orogenic stage in the southern São Francisco Craton, Brazil: Evidence from petrogenesis of the 2.0 Ga Cupim Pluton leucogranites","authors":"Syro Lacerda ,&nbsp;Martin Guitreau ,&nbsp;Leonardo Gonçalves ,&nbsp;Hugo Moreira ,&nbsp;Cristiane C. Gonçalves ,&nbsp;Marco Aurélio Pinheiro ,&nbsp;Cassiano Costa e Castro ,&nbsp;Régis Doucelance","doi":"10.1016/j.lithos.2024.107852","DOIUrl":"10.1016/j.lithos.2024.107852","url":null,"abstract":"<div><div>Sediment-derived granites (S-type) can provide detailed information about continental crust reworking processes and tectonic regimes through time. Their compositions reflect the nature of sedimentary rocks that melted to form them. Inherited accessory minerals in these granites can provide information regarding the age and nature of the crustal rocks that contributed to the formation of their sedimentary source rock. In addition, S-type granites typically form during collisional stages in modern orogens, and their Precambrian records can provide clues about ancient tectonics. In this contribution, we present a detailed petrogenesis of the Cupim Pluton, located in the Paleoproterozoic Mineiro Belt (Brazil). The Cupim pluton is composed of two-mica and garnet-bearing leucogranites that are strongly peraluminous (ASI &gt; 1.1), high-K (K₂O/Na₂O &gt; 1), low MgO + FeO + TiO₂ (&lt;2 wt%). Its composition is similar to that of melts experimentally produced by muscovite/biotite dehydration melting reactions. Rb/Sr and Rb/Ba ratios suggest that these leucogranites are formed by the melting of heterogeneous sedimentary source(s). Zircon crystals from the Cupim Pluton unveil a protracted crustal melting period (2.01–1.98 Ga) hitherto unknown in the Mineiro Belt, which itself discloses a late collisional orogenic stage in southern São Francisco Craton. Igneous zircon crystals exhibit εHf_(t) between −16.4 and − 0.6, and δ³⁰Si between −1.16 and − 0.26 ‰, which is typical for zircon from sediment-derived granites. Hafnium isotope variations reflect mixing between at least two crustal sources, which is in line with inherited zircon cores that evidence major Archean and minor Paleoproterozoic sediment contributions. The emplacement of the Cupim Pluton leucogranites ends a subduction-collision cycle, following a long period of TTG-sanukitoid magma production, and promoted the stabilization of the southern São Francisco Craton.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"490 ","pages":"Article 107852"},"PeriodicalIF":2.9,"publicationDate":"2024-11-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142658301","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}