Geochemistry Geophysics Geosystems最新文献

{"title":"Source Geometry and Rupture Characteristics of the 20 February 2023 Mw 6.4 Hatay (Türkiye) Earthquake at Southwest Edge of the East Anatolian Fault","authors":"Seda Yolsal-Çevikbilen,&nbsp;Tuncay Taymaz,&nbsp;Tahir Serkan Irmak,&nbsp;Ceyhun Erman,&nbsp;Metin Kahraman,&nbsp;Berkan Özkan,&nbsp;Tuna Eken,&nbsp;Taylan Öcalan,&nbsp;Ali Hasan Doğan,&nbsp;Cemali Altuntaş","doi":"10.1029/2023GC011353","DOIUrl":"https://doi.org/10.1029/2023GC011353","url":null,"abstract":"<div>\u0000 \u0000 \u0000 <section>\u0000 \u0000 <p>Following the catastrophic 6 February 2023 <i>Mw</i> 7.8 and <i>Mw</i> 7.6 Kahramanmaraş earthquakes in the East Anatolian Fault Zone (EAFZ; southeast Türkiye), numerous aftershocks occurred along the major branches of this left-lateral shear zone. The spatio-temporal distribution of the earthquakes implied the stress-triggering effects of co-seismic ruptures on closely connected fault segments over large distances. On the 20 February 2023 two earthquakes with <i>Mw</i> 6.4 and <i>Mw</i> 5.2 struck Hatay (Türkiye) located near the Samandağ-Antakya segment of the EAFZ. To understand the rupture evolution of these earthquakes, we first re-located the aftershock sequence that occurred over a 3-month period in the Hatay-Syria region. A normal faulting mechanism with a significant amount of left-lateral strike-slip component at a shallow focal depth of 12 km was estimated for the 2023 <i>Mw</i> 6.4 earthquake from the inversion of seismological data. Our slip models describe a relatively simple and unilateral rupture propagation along about 36 km-long active segments of the EAFZ. The co-seismic horizontal displacements inferred from the Global Navigation Satellite System data are compatible with the oblique slip kinematics. Furthermore, we suggest that this earthquake did not produce notable tsunami waves on the adjacent coasts since the rupture plane did not extend to the seafloor of the Eastern Mediterranean with substantial amount of vertical displacement. We reckon that a future large earthquake (Mw ≥ 7.0) in the Hatay-Syria region where increased stress was transferred to the fault segments of the EAFZ and the Dead Sea Fault Zone (DSFZ) after the 2023 earthquakes will be a probable source of tsunami at the coastal plains of the Eastern Mediterranean Sea region.</p>\u0000 </section>\u0000 </div>","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":null,"pages":null},"PeriodicalIF":2.9,"publicationDate":"2024-10-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2023GC011353","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142438979","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":"Re-Evaluating Water Column Reoxygenation During the End Permian Mass Extinction","authors":"F. Yang,&nbsp;S. Li,&nbsp;K. Y. An,&nbsp;D. P. G. Bond,&nbsp;R. Ao,&nbsp;X. B. Wu,&nbsp;L. L. Ma,&nbsp;Y. D. Sun","doi":"10.1029/2024GC011779","DOIUrl":"https://doi.org/10.1029/2024GC011779","url":null,"abstract":"<p>Ocean anoxia is considered a key driver of the end-Permian mass extinction (EPME). However, it is much debated whether there was an ocean reoxygenation phase during, and in the aftermath, of the EPME. Evidence for ocean reoxygenation is often inferred from the absence of framboidal pyrite in some boundary marine sediments (termed the “framboid gap”). To reconstruct ocean redox evolution across the EPME, we investigated the carbon isotopic, sedimentological, and redox records of the Ruichang and Ehtan sections in South China. These documents two negative δ¹³C_carb excursions and the development of anoxia associated with deepening leading up to the Permian-Triassic boundary. Above the level at which most siliceous organisms became extinct, pyrite framboid and iron proxies indicate that water column redox conditions were predominantly oxygenated but sporadically anoxic/ferruginous [non-sulfidic, free Fe(II) in the water] at Ruichang, while ferruginous conditions were more widely developed at Ehtan. These contrasting redox states are characteristic of a dynamic ocean redox landscape in the extinction interval. The “framboid gap” is seen in strata deposited under both oxic and ferruginous conditions, suggesting that the availability of decomposable organic matter for sulfate reduction additionally controlled framboid genesis. Our data confirm that oxygenated conditions were developed in some deep water basins during the EPME.</p>","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":null,"pages":null},"PeriodicalIF":2.9,"publicationDate":"2024-10-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024GC011779","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142404297","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 Silent VOICE—Searching for Geochemical Markers to Track the Impact of Late Jurassic Rift Tectonics","authors":"Jennifer M. Galloway,&nbsp;Thomas Hadlari,&nbsp;Keith Dewing,&nbsp;Terence Poulton,&nbsp;Stephen E. Grasby,&nbsp;Lutz Reinhardt,&nbsp;Mikhail Rogov,&nbsp;Jack Longman,&nbsp;Madeleine Vickers","doi":"10.1029/2024GC011490","DOIUrl":"https://doi.org/10.1029/2024GC011490","url":null,"abstract":"<p>A causal mechanism for the Volgian Isotopic Carbon Excursion (VOICE) remains enigmatic. Elemental geochemical profiles of the Deer Bay Formation, Sverdrup Basin, Arctic Canada that record the VOICE and contemporaneous strata are herein examined to provide insight into depositional environments during Late Jurassic-Early Cretaceous time. Silver (Ag) and Cadmium (Cd) are enriched across the VOICE at localities on Axel Heiberg Island, and in Tithonian (∼Volgian) strata of Ellef Ringnes Island. Other redox-sensitive trace elements do not exhibit spatially or temporally consistent patterns and indicate oxic conditions. A lack of relationship across the VOICE between Ag and the quality, quantity, and isotopic composition of organic matter suggests that the negative isotope excursion and interval of Ag enrichment are not merely functions of changes in organic matter source or amount, while a lack of spatially consistent change in geochemical indices of weathering similarly excludes climate change and/or sediment provenance as a driver. Therefore, in a ventilated setting and without marked changes in organic matter content, Ag enrichment may be due to hydrothermal activity. Contemporaneous Ag enrichment in strata from Svalbard suggests that a source of hot fluid sufficient to produce Ag-rich seawater may have been related to rifting in the adjacent proto-Amerasia Basin. Hydrothermal activity may also have been a widespread source of isotopically depleted carbon. This work develops new geochemical fingerprints that may be used to trace the spatial extent of hydrothermal events that do not leave an extinction pattern but may nonetheless have a far-reaching influence on biogeochemical systems.</p>","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":null,"pages":null},"PeriodicalIF":2.9,"publicationDate":"2024-10-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024GC011490","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142404191","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":"Oriented Acicular Rutile Inclusions in Eclogites: Exsolutions From Majoritic Garnet or Shock Needles?","authors":"Jian-Jun Yang,&nbsp;Hai-Jun Xu,&nbsp;Takao Hirajima","doi":"10.1029/2024GC011712","DOIUrl":"https://doi.org/10.1029/2024GC011712","url":null,"abstract":"<p>Oriented rutile needles (ORNs) forming a triangular network on the cross sections of garnet crystals have been widely used together with omphacite inclusions as evidence for exsolution from a majoritic garnet and exhumation of the host rocks from great depths (&gt;200 km) in the Earth. A coronitic eclogite at Yangkou in the Chinese Su-Lu high-pressure metamorphic belt contains ORNs that are only found in the reddish cores of garnet porphyroblasts. The texture formed by the ORNs is not restricted to garnet but extends into the coexisting other minerals, which together form pseudomorphs after augite. Therefore, the ORNs are not specifically related to the host garnet and cannot be exsolutions therefrom. The outer zones of the garnet porphyroblasts in contact with plagioclase pseudomorphs are pale and rutile-free but contain minute inclusions of omphacite, quartz, kyanite, phengite, and K-feldspar, typical of coronitic garnet between augite and plagioclase. Electron backscatter diffraction reveals no optimum matching of the low index crystallographic directions of rutile and garnet as required by an exsolution mechanism. On the other hand, the ORNs resemble the amorphous lamellae in quartz and zircon in meteorite and seismic shocked rocks, and are inferred to have crystallized earlier in seismic shocked augite and were then overgrown by the host minerals. By contrast, the rutile particles in garnet cataclasites in a nearby eclogite breccia display deformed and explosive patterns and random crystallographic orientations. All these observations are best explained by the seismic shock compression and rarefaction scenario proposed earlier.</p>","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":null,"pages":null},"PeriodicalIF":2.9,"publicationDate":"2024-10-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024GC011712","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142404293","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":"Obtaining High-Resolution Magnetic Records From Speleothems Using Magnetic Microscopy","authors":"Cauê S. Borlina,&nbsp;Eduardo A. Lima,&nbsp;Joshua M. Feinberg,&nbsp;Plinio Jaqueto,&nbsp;Ioan Lascu,&nbsp;Ricardo I. F. Trindade,&nbsp;Eric Font,&nbsp;Elisa M. Sánchez-Moreno,&nbsp;Luca Antonio Dimuccio,&nbsp;Yusuke Yokoyama,&nbsp;Josep M. Parés,&nbsp;Benjamin P. Weiss,&nbsp;Jeffrey A. Dorale","doi":"10.1029/2024GC011594","DOIUrl":"https://doi.org/10.1029/2024GC011594","url":null,"abstract":"<p>Speleothems are mineral deposits capable of recording detrital and/or chemical remanent magnetization at annual timescales. They can offer high-resolution paleomagnetic records of short-term variations in Earth's magnetic field, crucial for understanding the evolution of the dynamo. Owing to limitations on the magnetic moment sensitivity of commercial cryogenic rock magnetometers (∼10⁻¹¹ Am²), paleomagnetic studies of speleothems have been limited to samples with volumes of several hundreds of mm³, averaging tens to hundreds of years of magnetic variation. Nonetheless, smaller samples (∼1–10 mm³) can be measured using superconducting quantum interference device (SQUID) microscopy, with a sensitivity better than ∼10⁻¹⁵ Am². To determine the application of SQUID microscopy for obtaining robust high-resolution records from small-volume speleothem samples, we analyzed three different stalagmites collected from Lapa dos Morcegos Cave (Portugal), Pau d'Alho Cave (Brazil), and Crevice Cave (United States). These stalagmites are representative of a range of magnetic properties and have been previously studied with conventional rock magnetometers. We show that by using SQUID microscopy we can achieve a five-fold improvement in temporal resolution for samples with higher abundances of magnetic carriers (e.g., Pau d'Alho Cave and Lapa dos Morcegos Cave). In contrast, speleothems with low abundances of magnetic carriers (e.g., Crevice Cave) do not benefit from higher resolution analysis and are best analyzed using conventional rock magnetometers. Overall, by targeting speleothem samples with high concentrations of magnetic carriers we can increase the temporal resolution of magnetic records, setting the stage for resolving geomagnetic variations at short time scales.</p>","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":null,"pages":null},"PeriodicalIF":2.9,"publicationDate":"2024-10-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024GC011594","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142404320","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":"Spread or Splash: The Ubiquitous Role of Droplets in Mafic Explosive Eruptions","authors":"Pier Paolo Comida,&nbsp;Thomas J. Jones","doi":"10.1029/2024GC011770","DOIUrl":"https://doi.org/10.1029/2024GC011770","url":null,"abstract":"<p>Magma fragmentation is an essential process driving explosive volcanic eruptions, generating a distribution of pyroclasts with characteristic shape and grain size. These characteristics are often used to inform on the energetics of magma fragmentation and the associated eruption style and intensity. However, a portion of these pyroclasts, droplets when still in the molten state, are likely to be generated through impact mechanisms (i.e., collisions), and subsequent secondary fragmentation (i.e., splashing). Here, we successfully apply and dynamically scale concepts and findings of liquid droplet impacts in engineering to magma fragmentation processes in volcanology. We compile and model physical data for two mafic melt compositions (kimberlite and basalt) and use specific eruption examples from Igwisi Hills, Kīlauea and Stromboli volcanoes to define composition-specific impact dynamics. Pyroclast impact dynamics have a direct control on in-conduit processes, eruption dynamics, and ash dispersal. For low viscosity mafic melts such as kimberlite and basalt, pyroclast impacts can lead to both splash and deposition on the conduit wall, resulting either in conduit clearing or conduit narrowing, respectively. In both cases, shifting the impact regime toward surface deposition will lead to an inexorable decay in explosiveness, potentially switching the eruption style to effusive behavior. This has direct consequences for the transport of volcanic ash at the surface and inferring magma fragmentation processes (e.g., energies) from the depositional record.</p>","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":null,"pages":null},"PeriodicalIF":2.9,"publicationDate":"2024-10-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024GC011770","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142404188","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":"Patterns of Plio-Pleistocene Ice Volume Variability Recorded by the Large-Magnitude Explosive Eruptions From the Kamchatka-Kurile Volcanic Arc","authors":"Susanne M. Straub,&nbsp;Brendan Reilly,&nbsp;Maureen E. Raymo,&nbsp;Arturo Gómez-Tuena,&nbsp;Kuo-Lung Wang,&nbsp;Elisabeth Widom,&nbsp;David Kuentz,&nbsp;Richard J. Arculus","doi":"10.1029/2024GC011748","DOIUrl":"https://doi.org/10.1029/2024GC011748","url":null,"abstract":"<p>Marine fallout ash beds can provide continuous, time-precise records of highly explosive arc volcanism that can be linked with the climate record. An evaluation of revised Plio-Pleistocene (0–4 Myr) tephrostratigraphies from Ocean Drilling Program Sites 881, 882, and 884 confirms cyclicity of the Kamchatka-Kurile arc volcanism and a marked increase just after the intensification of the Northern Hemisphere glaciation at 2.73 Ma. The compositional constancy of the Kamchatka-Kurile volcano-magma systems through time points to external modulation of volcanic cyclicity and frequency. The stacked tephra record reveals periodic peaks in arc volcanicity at ∼0.3, ∼1.0, ∼1.6, ∼2.5, and ∼3.8 Myr that coincide with maxima of the global ice volume variability that have been linked with the amplitude modulation of the precession (0.3, 1.0 Myr) and obliquity (1.6, 2.5 and 3.8 Myr) bands. A simple model of a decreasing obliquity variance across the mid-Pleistocene Transition at constant precession variance produces an excellent correlation of ash bed cycles with the variability of global benthic δ¹⁸O (<i>r</i>² = 0.75), which implies that climate, and not direct orbital forcing, modulates Kamchatka-Kurile arc volcanism. The rising influence of precession variance in the Kamchatka-Kurile ash bed record after the mid-Pleistocene Transition contrasts with the dominant 100 kyr signal in the benthic δ¹⁸O global ice volume variability, which may either reflect limitations of the ash bed record or an regional rather than global influence of ice volume variability. Our results indicate that climate influences the Kamchatka-Kurile arc volcanism, which may influence climate only by feedback.</p>","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":null,"pages":null},"PeriodicalIF":2.9,"publicationDate":"2024-10-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024GC011748","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142404216","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":"Multi-Stage Magmatism During Slab Exhumation Drives the Geochemical Evolution of Continental Crust: Insights From Paleozoic Granitoids in South Altyn, Western China","authors":"Long Tian,&nbsp;Liang Liu,&nbsp;Danling Chen,&nbsp;Yuting Cao,&nbsp;Yongsheng Gai,&nbsp;Tuo Ma,&nbsp;Qian Wang,&nbsp;Lei Kang","doi":"10.1029/2024GC011553","DOIUrl":"https://doi.org/10.1029/2024GC011553","url":null,"abstract":"<p>The present continental crust is characterized by a felsic upper crust and a mafic lower crust, resulting from significant geochemical differentiation over geological time. While various processes have been proposed to explain this differentiation, subduction zones remain pivotal regions for understanding the compositional evolution of continental crust. This study focuses on the South Altyn (SA) continental subduction-collision belt in western China, a unique setting that experienced ultra-deep (&gt;300 km) continental subduction followed by multi-stage exhumation. We present a comprehensive study of four granitoid suites from Tatelekebulake (TTLK) area in SA: biotite granite (BG), monzogranite (MG), K-feldspar granite (KG), and leucogranite (LG). Comprehensive studies on petrology, geochemistry and zircon U-Pb dating show that these granitoids formed at 494, 451, 414, and 418 Ma, respectively, and originated from protoliths with affinity to the subducted continental crust in SA. Phase equilibrium modeling suggests that BG formed at ∼800°C and 0.6 GPa, while the MG, KG, and LG formed by differentiation crystallization of the BG magma under progressively decreasing temperature and pressure conditions (750°C, 0.5 GPa; 740–700°C, 0.2 GPa; and 700–640°C, 0.1 GPa, respectively). These results, combined with previous studies, allow us to reconstruct the tectonic processes of continental exhumation and subsequent orogenic collapse in SA during the Early Paleozoic. Importantly, our findings reveal that magmatism derived from partial melting of subducted continental crust can promote the geochemical evolution of continental crust toward more felsic compositions, even in the absence of significant crustal growth or mantle-derived magmatism. This study provides a valuable case for understanding the compositional evolution of continental crust in deep subduction zones and challenges conventional models that rely heavily on arc magmatism for crustal differentiation. Moreover, our results contribute to a broader understanding of crustal evolution processes in collisional orogens worldwide and highlight the importance of recycling and differentiation of subducted continental material in shaping crustal compositions.</p>","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":null,"pages":null},"PeriodicalIF":2.9,"publicationDate":"2024-10-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024GC011553","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142404269","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":"Nd Isotopic Equilibration During Channelized Melt Transport Through the Lithosphere: A Feasibility Study Using Idealized Numerical Models","authors":"Mousumi Roy,&nbsp;G. Lang Farmer,&nbsp;Kellen Malone","doi":"10.1029/2024GC011593","DOIUrl":"https://doi.org/10.1029/2024GC011593","url":null,"abstract":"&lt;p&gt;This study is motivated by the observed variability in trace element isotopic and chemical compositions of primitive (Si&lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;msub&gt;\u0000 &lt;mi&gt;O&lt;/mi&gt;\u0000 &lt;mn&gt;2&lt;/mn&gt;\u0000 &lt;/msub&gt;\u0000 &lt;mo&gt;&lt;&lt;/mo&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; ${mathrm{O}}_{2}&lt; $&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt;52 wt %) basalts in southwest North America (SWNA) during the Cenozoic transition from subduction to extension. Specifically, we focus on processes that may explain the enigmatic observation that in some localities, basalts with low Ta/Th, consistent with parental melts in a subduction setting, have &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;msub&gt;\u0000 &lt;mi&gt;ε&lt;/mi&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mi&gt;N&lt;/mi&gt;\u0000 &lt;mi&gt;d&lt;/mi&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;/msub&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; ${varepsilon }_{Nd}$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt; signatures consistent with continental lithospheric mantle (CLM). In locations with the oldest CLM (Proterozoic and Archean), Cenozoic basalts with low Ta/Th have &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;msub&gt;\u0000 &lt;mi&gt;ε&lt;/mi&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mi&gt;N&lt;/mi&gt;\u0000 &lt;mi&gt;d&lt;/mi&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;/msub&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; ${varepsilon }_{Nd}$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt; well below zero. We model channelized magma transport through the CLM using simple 1D transport models to explore the extent to which diffusive and reactive mass exchange can modify Nd isotopic compositions via open system melt-wallrock interactions. For geologically reasonable channel spacings and volume fractions, we quantify the reactive assimilation rates required for incoming melt with a different &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;msub&gt;\u0000 &lt;mi&gt;ε&lt;/mi&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mi&gt;N&lt;/mi&gt;\u0000 &lt;mi&gt;d&lt;/mi&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;/msub&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; ${varepsilon }_{Nd}$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt; than the wall-rock to undergo a substantial isotopic shift during &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mo&gt;≈&lt;/mo&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; ${approx} $&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt;10 km channelized melt transport. In the presence of grain boundaries, e","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":null,"pages":null},"PeriodicalIF":2.9,"publicationDate":"2024-09-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024GC011593","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142359900","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":"Paleomagnetic Constraints on the Rapid Plate Shift of North China Block During the Jurassic From ∼155 Ma Dykes and Sills","authors":"Pengfei Wang,&nbsp;Zhiyu Yi,&nbsp;Joseph G. Meert,&nbsp;Yu-Shu Liu,&nbsp;Silin Yang,&nbsp;Fei Wang,&nbsp;Zaijun Li,&nbsp;Baochun Huang","doi":"10.1029/2024GC011671","DOIUrl":"https://doi.org/10.1029/2024GC011671","url":null,"abstract":"<p>A large-scale apparent polar wander occurred during the Jurassic interval, which is interpreted as true polar wander (TPW). As the motion is nearly orthogonal to the TPW axis, the North China Block (NCB) experienced the largest latitudinal and environmental changes and provides unique constraints on Jurassic TPW. However, due to the lack and uneven quality of paleomagnetic data, TPW records in North China are controversial. Here, we report a new paleomagnetic pole (80.8°N, 13.0°E, A₉₅ = 7.4°) from the late Jurassic sills and dykes that intrude the Nandaling and Xiahuayuan formations in the NCB. The new pole places the NCB at 36.8° ± 7.4°N at 155 ± 3.4 Ma, using Beijing as the reference site. Combined with the reliable Jurassic poles, our study reveals a large, steady southward shift of 37.3° ± 7.2° for the NCB during the Middle and Late Jurassic, and reflects a component of TPW. The position of ∼155 Ma pole also supports significant TPW prior to ∼160 Ma and agrees with proposals attributing the diachronous 165–155 Ma aridification across the Eastern Asian blocks.</p>","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":null,"pages":null},"PeriodicalIF":2.9,"publicationDate":"2024-09-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024GC011671","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142359927","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}