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The upper sandy loess unit L9 on the Chinese Loess Plateau (CLP) corresponds to marine isotope stages 22–24, and it represents aeolian deposition under conditions of extreme aridification. However, the forcing mechanism remains controversial. Numerous paleomagnetic studies in the eastern CLP show that the coarsest part of L9 is remagnetized and has a normal geomagnetic polarity. However, our results show that in loess sections in the western CLP the coarsest part of L9 records a primary reverse polarity. This spatially inconsistent magnetization pattern originates mainly from the different magnetic carriers of the characteristic remanent magnetization (hematite in the western CLP and magnetite in the eastern CLP), which suggests a different dust provenance between the western and eastern CLP. We ascribe this spatial contrast in dust provenance to the episodic uplift of the northeastern Tibetan Plateau, which also led to the extreme aridification of the East Asian interior at ∼900 ka. Plain Language Summary Climatic extremes have destructive impacts on human society and the natural environment. In the wind‐blown dust deposits (loess) of the Chinese Loess Plateau (CLP), several loess layers are exceptionally coarse‐grained, representing deposition under conditions of extreme aridification. Among these loess beds, the upper sandy loess layer L9, corresponding to marine isotope stages 22–24, has attracted much research attention. An important reason for this is the widely reported remagnetization of the coarsest part of L9 in loess sections in the eastern CLP. However, our present work found that for the coarsest part of L9 in the loess sections in the western CLP, the reported remagnetization is disappeared. This spatially inconsistent magnetization pattern originates mainly from the different magnetic carriers of the characteristic remanent magnetization, hematite in the western Loess Plateau and magnetite in the eastern Loess Plateau. We propose that the enhanced glacial grinding and the denudation of mountains caused by the uplift of the northeastern Tibetan Plateau led to the production of enormous quantities of fluvial and fluvioglacial materials rich in hematite, which were supplied specifically to the western CLP. This uplift also resulted in the occurrence of extreme aridification in the East Asian interior at ∼900 ka. Key Points The coarsest part of L9 in the western Loess Plateau has a reverse geomagnetic polarity, unlike the normal polarity in the eastern part This spatially inconsistent magnetization results mainly from a spatial difference in magnetic carriers Uplift of the northeastern Tibetan Plateau at ∼900 ka caused the enrichment of detrital hematite specifically in the western Loess Plateau

The absence of reliable paleomagnetic constraints from the Lhasa Block has led to alternative interpretations of its late Paleozoic position and timing of rifting from Gondwana, reflecting uncertainties in early Neo‐Tethyan paleogeography. This study presents paleomagnetic and geochronological data from the middle Permian Luobadui Formation, providing a new paleogeographic constraint on the Lhasa Block. Despite possible remagnetization, the dual‐polarity magnetization, hosted in different minerals and lithologies, likely represents a middle Permian remanence. This constraint implies the Lhasa Block was located at 16.7 ± 5.3°S at 267.8 ± 5 Ma, following its rifting from Gondwana. New U‐Pb detrital zircon ages from sandstones further suggest the Lhasa Block was located along the northwestern margin of Australia prior to rifting. Integrating other geological evidence, we propose that the Bangong Co‐Nujiang and Yarlung‐Zangbo oceans, now preserved as sutures flanking the Lhasa Block, both opened before the middle Permian, potentially representing branches of the same nascent oceanic corridor (Neo‐Tethys). Plain Language Summary The Lhasa Block, located in southern Tibet, is critical to understanding the early tectonic evolution of the Neo‐Tethys Ocean, which separated Gondwana from Laurasia during the late Paleozoic to early Mesozoic. However, the timing and mechanisms of the Lhasa Block's rifting from Gondwana remain controversial, with several competing models proposing different scenarios. In this study, we present new paleomagnetic and geochronological data from middle Permian strata of the Lhasa Block, which suggest that this block may have rifted from the northwestern margin of the Australian sector of Gondwana before ∼268 Ma. Combined with other geological evidence, we propose that the Bangong Co‐Nujiang and Yarlung‐Zangbo oceans, now preserved as sutures to the north and south of the present Lhasa Block, were branches of the Neo‐Tethys Ocean and probably existed side by side in an east‐west orientation during the middle Permian. This study thus provides important insights into the tectonic history of the Lhasa Block and the early evolution of the Neo‐Tethys Ocean. Key Points The Lhasa Block was positioned at approximately 17°S around 268 Ma The Lhasa Block may have rifted from the northwestern margin of the Australian sector of Gondwana before the middle Permian The Bangong Co‐Nujiang and Yarlung‐Zangbo oceans likely opened before the middle Permian, possibly as branches of the nascent Neo‐Tethys

Crustal deformation and hydrothermal percolation related to the India‐Asia collision have caused extensive remagnetization of the Tethyan Himalaya Terrane (THT). The present work identified three phases of regional remagnetization during 62.3–50.0 Ma for the east‐central THT. Consequently, a model of three‐stage India‐Asia collision was proposed. The east‐central THT first collided with the southward migrated southern margin of the Lhasa Terrane (LT) at 5.4 ± 0.9°N during 62.3–60.9 Ma. Subsequently, the THT continuously moved northward and pushed the southern margin of the LT back to its original position prior to the initiation of fore‐arc and back‐arc extension on both sides of the Gangdese magmatic arc. Since the final suturing of the THT with Asia at ∼10°N during 59.8–58.0 Ma, the east‐central THT remained stationary until India collided with it at 10.9 ± 5.1°N at ∼50.0 Ma. Plain Language Summary The collision of India and Asia caused intense tectonic deformation and hydrothermal alteration throughout the Tethyan Himalaya Terrane (THT), which resulted in the large‐scale remagnetization in the THT. The regional remagnetization of the THT can be used to constrain the India‐Asia collision process, on the premise that the time of remagnetization can be determined. Based on this assumption, we measured two representative Paleocene remagnetized components from Early Jurassic limestones in the Gyangze Basin in the east‐central THT. These remagnetized components, combined with non‐remagnetized components and remagnetization events recorded in the adjacent areas, suggest that the east‐central THT experienced three phases of regional remagnetization during 62.3–50.0 Ma. The first and second phases of remagnetization in the north‐central part of the east‐central THT occurred at the paleolatitude of 5.4 ± 0.9°N at 62.3–60.9 Ma and 10.3 ± 1.0°N–9.5 ± 1.1°N at 59.8–58.0 Ma, respectively. The third phase of remagnetization occurred in the southern part of the east‐central THT, at the paleolatitude of 10.9 ± 5.1°N at ∼50.0 Ma. Consequently, a model of three‐stage India‐Asia collision and southward spreading tectonic deformation of the THT was proposed based on these successive remagnetizations. Key Points The east‐central Tethyan Himalaya Terrane (THT) experienced three phases of large‐scale remagnetization during 62.3–50.0 Ma The collision of THT with the Lhasa Terrane commenced at 62.3–60.9 Ma and finished at 59.8–58.5 Ma India finally collided with the THT at the paleolatitude of ∼10.9 ± 5.1°N at ∼50.0 Ma

The drift history of the Tethyan Himalaya provides key constraints on the India‐Asia collision, Himalayan‐Tibetan orogenesis, and associated global climate change. Here we present rock magnetic, petrographic, geochronologic, and paleomagnetic results of the Bolinxiala Formation limestones in the western Tethyan Himalaya. In situ calcite U‐Pb dating and biostratigraphy indicate that the Bolinxiala Formation limestones were formed during the Early Cretaceous (∼125–100 Ma), not Middle Jurassic as previously thought. The site‐mean direction for the 23 sites is Dg = 23.3°, Ig = +10.0°, kg = 40.1 and α95 = 4.8° in situ and Ds = 20.8°, Is = +19.0°, ks = 67.2 and α95 = 3.7° after tilt‐correction, yielding a paleomagnetic pole position at 61.6°N, 212.9°E with A95 = 2.7°, corresponding to a paleolatitude of 10.3° ± 2.7°N. A positive fold test indicates a prefolding origin. When compared with reliable Cretaceous–Eocene paleopoles from the western Tethyan Himalaya, we suggest that the Bolinxiala Formation limestones likely underwent remagnetization during ∼54–49 Ma. Petrologic evidence, including the presence of framboidal oxides derived from sulfides (primarily pyrite) and calcite veins, supports chemical remanent magnetization as the primary mechanism responsible for the remagnetization. Our new results, combined with reliable Cretaceous paleomagnetic data from the western Lhasa terrane, indicate that the western part of the India‐Asia collision occurred no later than ∼54–49 Ma.

Framboidal pyrrhotite, in sharp contrast to framboidal pyrite, has been rarely reported, and its formation remains poorly understood. Here we report its clear identification in a shale‐gas well core and explore its potential as a proxy for diagenesis or low‐grade metamorphism of organic‐rich sediments. A range of complementary results including petrography, geochemistry, rock magnetism and paleomagnetism, collectively support the identification of framboidal pyrrhotite, whose coexistence with other framboidal minerals indicates pseudomorphic replacement of framboidal pyrite. A strong correlation between total organic carbon and natural remanent magnetization, together with its restriction to organic‐rich layers, highlights organic matter's role in its genesis. Paleomagnetic and vitrinite reflectance data further link its formation to magmatic heating (∼274°C). We therefore propose hydrothermal replacement of framboidal pyrite by framboidal pyrrhotite, involving heating and organic matter. This study highlights its diagnostic features, key conditions, and proxy potential for hydrothermal alteration and low‐grade metamorphism in organic‐rich sediments.

We report paleomagnetic records of Matuyama–Brunhes geomagnetic polarity reversal and associated key tephra layers from the Early–Middle Pleistocene marine sedimentary succession in the Boso Peninsula. The outcrop is in Terasaki, Chiba, Japan and ~ 25 km northeast of the Chiba section. The sediment succession consists of a massive siltstone layer of the Kokumoto Formation, Kazusa Group. A tephra layer was identified in the middle of the outcrop with chemical composition comparable to that of the Byk-E tephra layer from the Chiba section defining the base of the Chibanian Stage. Oriented paleomagnetic samples were collected at intervals of 1–10 cm from the siltstone. To identify the primary remanent magnetization, progressive alternating field demagnetization (PAFD) and progressive thermal demagnetization (PThD) were conducted on pilot samples. Identification of primary magnetization with PAFD was not successful, especially for reversely magnetized samples. In addition, magnetization during PThD showed sharp drops around 175 °C, which decreased gradually between 175 °C and ~ 300 °C, and became unstable above ~ 350 °C. To extract the primary remanent magnetization while avoiding laboratory alteration by heating, a PThD up to 175 °C followed by PAFD was conducted. Combined analysis of remagnetization circles enables extraction of primary magnetization with improved reliability. Rock magnetic experiments were conducted during stepwise heating to understand the magnetic minerals involved and to evaluate the influence of laboratory heating. During heating, FORC-PCA revealed significant changes of magnetic minerals at 200 °C, 400 °C, 450 °C and 550 °C. Rock magnetic analyses and electron microscopy indicate that titanomagnetite/magnetite are magnetic minerals contributing to primary remanent magnetization. Greigite was also identified preserving secondary magnetizations during sub-seafloor diagenesis. The presence of feroxyhyte is suggested as secondary magnetization through the weathering of pyrite by exposure to the air after the Boso Peninsula uplift. The correlation of relative paleointensity with the Chiba section provides an age model with sedimentation rates of 30 cm/kyr and 18 cm/kr for the intervals above and below the Byk-E tephra. VGP latitudes are highly consistent with those from the Chiba section based on the age model, which assigns the main directional swing from reversed to normal polarities as 772.8 ± 0.5 ka.

—In the paper, we present the results of paleomagnetic studies on numerous intrusive bodies of the Bashkirian megazone, a major tectonic zone of the Southern Urals. More than 70 intrusions in various parts of the Bashkirian megazone (in the northern, central, and southern part of the structure) were sampled. The studied intrusions have Riphean age. However, as a significant part of the rocks of the Southern Urals, these intrusive bodies were remagnetized during the Late Paleozoic collision within the Urals fold belt. Here, we discuss the secondary Late Paleozoic component of natural remanent magnetization. According to the obtained paleomagnetic data, the secondary Late Paleozoic component in most of the Bashkirian megazone is post-folding, i.e., formed after the completion of the main phase of fold deformations in the Southern Urals. A comparison of paleomagnetic directions obtained from intrusions in different parts of the Bashkirian megazone showed that there were no significant movements of individual parts of the Bashkirian megazone relative to each other after the formation of the Late Paleozoic component. The Late Paleozoic remanence component yielded a paleomagnetic pole of Plong = 171.6°, Plat = 39.9°, α 95 = 5.9°, and N = 6 from six regions (38 sites) in the Bashkirian megazone. The obtained pole is statistically indistinguishable from the mean of 15 poles for Stable Europe with ages of 280–301 Ma. Thus, the secondary Late Paleozoic component in the Bashkirian megazone formed approximately 280–301 million years ago, after which the Bashkirian megazone did not experience any relative motions with respect to the East European craton.

Experiments demonstrate that magnetic nanoparticles, embedded in a tissue, very often form heterogeneous structures of various shapes and topologies. These structures (clusters) can significantly affect macroscopical properties of the composite system, in part its ability to generate heat under an alternating magnetic field (so-called magnetic hyperthermia). If the energy of magnetic interaction between the particles significantly exceeds the thermal energy of the system, the particles can form the closed ring-shaped clusters. In this work, we propose a relatively simple model of the heat production by the particles united in the ‘ring’ and immobilized in a host medium. Mathematically, this model is based on the phenomenological Debye equation of kinetics of the particles remagnetization. Magnetic interaction between all particles in the cluster is taken into account. Our results show that the appearance of the clusters can significantly decrease the thermal effect. This article is part of the theme issue ‘Transport phenomena in complex systems (part 1)’.

How and when sedimentary rocks record Earth's magnetic field is complex. Most studies assume a time‐progressive lock‐in mechanism during sediment deposition called depositional remanent magnetization (DRM). However, magnetic minerals can also form in situ, recording a chemical remanent magnetization (CRM) that is discontinuous in time. Disentangling the two mechanisms represents a major hurdle, and differences in their recording efficiencies remain unexplored. Here, our theoretical solutions demonstrate that CRM intensities exceed DRM by a factor of six when acquired in the same magnetic field. Novel experiments growing greigite (Fe3S4) in sediments and subsequent redeposition under identical magnetic field conditions confirm the predicted difference in recording efficiency. Thus, if left unrecognized, CRM leads to overestimated paleointensity and deserves more attention when interpreting Earth's magnetic history from sedimentary records. Recognition of fundamental differences between CRM and DRM characteristics provide a way forward to distinguish the recording mechanisms through routine laboratory protocols. Plain Language Summary Remanent magnetizations preserved in sedimentary rocks serve as a continuous record of Earth’s magnetic field history and play a fundamental role in understanding the Earth system. It is commonly assumed that magnetic minerals align with the magnetic field as a particle settles through the water column, known as a depositional remanent magnetization (DRM). However, diagenesis can lead to chemical growth of magnetic minerals, known as a chemical remanent magnetization (CRM). CRM lacks stratigraphic continuity and can obscure or completely overprint the original magnetization any time after sediment deposition, leading to a magnetic record that is uncorrelated with the age of the rock. Yet, CRMs go largely unrecognized. Theory and experiments in our paper document that CRMs record the magnetic field six times more efficiently than DRMs. Our work provides a way to distinguish the two through routine laboratory protocols. Key Points Recording efficiency of chemical remanent magnetization (CRM) is six times higher than depositional remanent magnetization (DRM) Undetected chemical remanences lead to overestimated relative paleointensity estimates Comparison of natural and laboratory magnetization and demagnetization behavior help identify chemical remanent magnetizations in sediments

Paleomagnetic analysis has been carried out on Late Neoproterozoic dike swarms from two areas along the Red Sea coast: 13 dikes (87 samples) close to the Um Rus gold mine and eight dikes (59 samples) at Sadi Salem. Rock magnetic experiments indicate that the main carrier of magnetization of these dikes is titanomagnetite and/or magnetite. Most samples display a component of magnetization (CA) that is in agreement with previously published Paleo-Late Neoproterozoic poles from other dikes and from one ore complex. But they cluster around the Cenozoic (0–60 Ma) portion of Torsvik's Gondwana apparent polar wander path (APWP) when plotted in southern African coordinates. We suggest two causes of this behavior (remagnetization related to the opening of the Red Sea or later emplacement of the dikes along pre-existing Paleo-Late Neoproterozoic fractures) will have to be tested with new reliable paleomagnetic data on carefully dated rocks. A second component (CB) seen in many of our samples but which is difficult to estimate is in agreement with Late Neoproterozoic granite poles and a dike supposed to be Triassic in age. However, all these poles plot on the Jurassic-Cretaceous portion (80–200 Ma) of Torsvik's path. These results, as well as the Cambro-Carboniferous sediments from Sinai and the Late Neoproterozoic Dokhan volcanic formation that cluster around the Late Paleozoic portion (280–300 Ma) of Torsvik's APWP, are tentatively interpreted as global viscous remagnetizations acquired, respectively, during the Cretaceous Normal and the Kiaman Reverse superchrons.