Earth and Planetary Science Letters最新文献

{"title":"Composition and age constraints on a Hadean enriched mantle source revealed by the Paleoarchean São Tomé layered intrusion, NE Brazil","authors":"V.B. Garcia ,&nbsp;J. O'Neil ,&nbsp;E.L. Dantas ,&nbsp;C.T. Augustin","doi":"10.1016/j.epsl.2024.119051","DOIUrl":"10.1016/j.epsl.2024.119051","url":null,"abstract":"<div><div>Evidence for Hadean depleted mantle reservoir(s) is well-established by mantle-derived rocks from multiple Archean complexes showing excesses in ¹⁴²Nd compared to the modern mantle. Yet, the existence of an early enriched mantle source, which should have concomitantly formed during these Hadean silicate differentiation event(s), has only been recently confirmed by well-resolved ¹⁴²Nd deficits measured in Paleoarchean mafic amphibolites from the São José do Campestre massif of the Borborema Province, NE Brazil. To investigate the nature and extent of this early-formed enriched reservoir, a series of samples from the Seridó belt, NE Brazil, have been investigated for their geochemical and coupled ^147,146Sm-^143,142Nd isotopic compositions, focusing on the Paleoarchean São Tomé layered intrusion. The São Tomé intrusion is composed of layers of metamorphosed mafic and ultramafic rocks with whole-rock trace element compositions and high olivine crystal Ni contents consistent with an incompatible trace element enriched pyroxenitic mantle source. Most analyzed samples from the Seridó belt yielded negative µ¹⁴²Nd, as low as ∼ -20 (representing the lowest ¹⁴²Nd/¹⁴⁴Nd ratio ever measured in terrestrial rocks), with an average µ¹⁴²Nd for the São Tomé intrusion of -9.6 ± 1.4. The São Tomé samples interpreted as the least isotopically disturbed yielded an ¹⁴⁷Sm-¹⁴³Nd isochron age of 3551 ± 368 Ma, consistent with previous zircon U-Pb ages, with an initial ε¹⁴³Nd = -1.7 ± 1.2. Coupling the long-lived ¹⁴⁷Sm-¹⁴³Nd and the short-lived ¹⁴⁶Sm-¹⁴²Nd systems for the São Tomé rocks suggests a Hadean enriched mantle source formed at ∼4.44 Ga with a ¹⁴⁷Sm/¹⁴⁴Nd of ∼0.18, which may be complementary to the early depleted mantle recorded by Eoarchean rocks from the North Atlantic Craton, possibly formed during magma ocean crystallization. These results also imply that the record of this Hadean enriched mantle source is not restricted to the São José do Campestre massif but extends to a larger portion of the Borborema Province.</div></div>","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":"647 ","pages":"Article 119051"},"PeriodicalIF":4.8,"publicationDate":"2024-10-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142419319","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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":"Dynamic evolution of competing same-dip double subduction: New perspectives of the Neo-Tethyan plate tectonics","authors":"Arnab Roy ,&nbsp;Nibir Mandal ,&nbsp;Jeroen Van Hunen","doi":"10.1016/j.epsl.2024.119032","DOIUrl":"10.1016/j.epsl.2024.119032","url":null,"abstract":"<div><div><em>Same-dip double-subduction</em> (SDDS) systems are widely reported from present as well as past complex convergent plate tectonic configurations. However, the dynamics of their evolution is poorly understood, which is crucial to conceptualize anomalous subducting slab kinematics and associated observed geological phenomena, such as irregular trench migration rates, high convergence velocities, and slab break-off. To bridge this gap, we develop dynamic thermo-mechanical subduction models and investigate the initiation and evolution of SDDS systems, considering three different initial plate configurations: oceanic, oceanic-continental and multiple continental settings, based on Neo-Tethyan paleo-reconstructions. Each model offers new insights into the complex tectonic history of the major Neo-Tethyan subduction zones, particularly the Indo–Eurasian and Andaman convergent systems. We evaluate the slab-slab interactions, trench and subduction kinematics, inter-plate reorganization, and temporally varying mantle flow patterns involved in the dynamic evolution of these SDDS systems. The oceanic SDDS model simulations reveal that a sizable oceanic plate can initiate two subduction zones synchronously, and they evolve unequally in a competing mode, leading to exceptionally high convergence rates (∼16–17 cm/year) for a prolonged duration (∼7–8 Myr). This finding explains the coeval activity of coupled subduction zones in the Indo-Eurasia convergence during the Cretaceous evolution of the Neo-Tethys. We further implement a corresponding single subduction model to assess the additional effects of competing slab kinematics in an oceanic SDDS setting. The ocean-continent SDDS model, on the other hand, localizes subduction preferentially at passive margins between the oceanic plate and the continental block, forming double subduction zones that grow almost equally to form a spreading centre between the two trenches. These model results allow to reconstruct the Cenozoic evolution of the eastern Neo-Tethyan region, which ultimately led to the development of the Andaman subduction zone. We also show the post-Cretaceous evolution of the Indo–Eurasian collision zone as a consequence of the SDDS dynamics in presence of multiple continental blocks. These dynamics facilitated slab break-off, transforming the SDDS into a single subduction system in a relatively short time frame (∼3 Myr). We finish with a synthesis of the paleo-reconstructions of the Neo-Tethys in the perspective of these SDDS models.</div></div>","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":"647 ","pages":"Article 119032"},"PeriodicalIF":4.8,"publicationDate":"2024-10-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142419321","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Magnetotelluric evidence for the formation of the layered Sask Craton by flat slab subduction","authors":"B.F.W. Chase,&nbsp;M.J. Unsworth","doi":"10.1016/j.epsl.2024.119027","DOIUrl":"10.1016/j.epsl.2024.119027","url":null,"abstract":"<div><div>Long-period magnetotelluric (MT) data were collected at 56 locations over the Sask Craton in 2021 and 2022. The data were combined with existing broadband data and inverted to produce a 3-D resistivity model of the Sask Craton and Trans-Hudson Orogen (THO). The model reveals a number of northeast striking electrically conductive crustal structures that extend into the mantle lithosphere. In the mantle lithosphere, these conductors coalesce into a single large low resistivity anomaly in the depth range 70–85 km termed the Northern Sask Craton (NSC) conductor. The resistivity of the NSC conductor is attributed to sulfides deposited along an interface between a flat slab that was accreted to the base of the pre-THO Sask Craton lithosphere during closure of the Manikewan Ocean. Kimberlites have erupted along the margin of the NSC conductor. The boundary of the conductor likely represents deep-seated faults and mantle terrane boundaries formed during flat slab subduction that allowed the ascent of kimberlite melts. The resistivity of the northeast-trending conductors can be interpreted as due to graphite and sulfides precipitated by past fluid or melt flow during ocean closure and orogensis. A number of these conductors are located beneath known mineral districts and trends and may represent source pathways for regional base and precious metal deposits. Other conductors may represent possible, previously unknown, regions hosting mineralization. Many of these conductors are associated with major regional faults and shear zones, which may be deep-seated features that helped to guide both kimberlites and mineralizing fluids. Of the prominent northeast-trending conductors west of the Sask Craton, one corresponds to the previously reported North American Central Plains (NACP) conductor. The new model shows that this conductor abruptly terminates at 54 °N and is not observed farther south in the model. This shows that the NACP is not as spatially continuous as previously suggested, suggesting that the tectonic processes that formed the THO were not as uniform along-strike as shown in existing tectonic models. The connection of one of the northeast-trending anomalies to the NSC conductor suggests that a previously unrecognized phase of east-dipping subduction may have occurred beneath the Sask Craton as the THO was formed.</div></div>","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":"647 ","pages":"Article 119027"},"PeriodicalIF":4.8,"publicationDate":"2024-10-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142419316","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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":"Lithium isotopes track changes in continental weathering regimes across the end-Permian mass extinction in Southwest China","authors":"Rong-Hui Ye ,&nbsp;Feifei Zhang ,&nbsp;Guang-Yi Wei ,&nbsp;Jianbo Chen ,&nbsp;Zhuo Feng ,&nbsp;Shu-zhong Shen","doi":"10.1016/j.epsl.2024.119045","DOIUrl":"10.1016/j.epsl.2024.119045","url":null,"abstract":"<div><div>It has been assumed there was a massive amount of volcanic CO₂ injection into the Permian-Triassic atmosphere and ocean systems, leading to rapid climatic warming and expansion of marine anoxia. However, it remains intriguing how Earth recovered from such a CO₂-driven hyperthermal condition. One potential mechanism involves the negative feedback between continental silicate weathering and atmospheric CO₂, which could have helped maintain habitability across the end-Permian mass extinction (EPME) interval. This process can be examined using lithium isotopes (δ⁷Li), which reflect the balance of physical erosion and chemical weathering, and chemical weathering indices such as the Chemical Index of Alteration (CIA), which indicates the chemical alteration of parent materials during weathering. In this study, we analyze siliciclastic sedimentary rocks from the Lopingian to Lower Triassic depositional sequences in the HK-1 drill core at the Lengqinggou section, a terrestrial coastal depositional environment in Southwest China, to reconstruct changes in continental chemical weathering intensity across the EPME. We observed a significant ∼4 ‰ positive shift in δ⁷Li, accompanied by a marked decrease in Li content from 26 ppm to 6 ppm. Our corrected CIA data (CIA_corr) also exhibits a considerable decrease from 94 to 59 across the EPME. The new δ⁷Li and CIA_corr data from the terrestrial section indicate a decrease in overall chemical weathering intensity in Southwest China, alongside an increase in physical erosion rates, suggesting a shift from a transport-limited to a kinetically limited weathering regime across the EPME. These changes in the continental weathering regime appear to be linked to active volcanic activity near the South China Block, which led to massive deforestation and the collapse of soil systems. Dramatic reductions in chemical weathering intensity may result in inefficient atmospheric CO₂ consumption through silicate weathering if other climatic and tectonic conditions remain constant, potentially contribute to maintaining high global surface temperatures and prolonged marine anoxia into the Early Triassic.</div></div>","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":"647 ","pages":"Article 119045"},"PeriodicalIF":4.8,"publicationDate":"2024-10-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142419318","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Clumped isotopes constrain thermogenic and secondary microbial methane origins in coal bed methane","authors":"Xinchu Wang ,&nbsp;Biying Chen ,&nbsp;Hui Nai ,&nbsp;Cong-Qiang Liu ,&nbsp;Guannan Dong ,&nbsp;Naizhong Zhang ,&nbsp;Si-Liang Li ,&nbsp;Jonathan Gropp ,&nbsp;Jennifer McIntosh ,&nbsp;Rob M. Ellam ,&nbsp;John M. Eiler ,&nbsp;Sheng Xu","doi":"10.1016/j.epsl.2024.119023","DOIUrl":"10.1016/j.epsl.2024.119023","url":null,"abstract":"<div><div>Methane is an economic energy resource and potent greenhouse gas. Distinguishing secondary microbial methane from thermogenic gas is important for natural gas exploration and consideration of subsurface microbial activity in the global carbon cycle, but remains challenging. To understand controls on methane origins in natural gas systems, we investigated the methane clumped isotopologue distributions in the Qinshui Basin high-thermal maturity coal bed methane (CBM) reservoir. Here, near-equilibrium clumped isotopologues distribution (Δ¹³CH₃D and Δ¹²CH₂D₂) inferred a temperature interval of 21.6–252.3 °C. The high-temperature thermodynamic equilibrium most likely represents original thermogenic CBM characteristics during coalification. The low-temperature equilibrium clumped isotopologue distributions suggest microbial alteration to CH₄ isotopic bond ordering by increased enzymatically catalyzed isotopic exchange. The independent constraints from clumped isotopes, integrated with other geochemical and genomic evidence, confirm notable secondary microbial methane from biodegradation in the highly mature reservoir. Thus, methane clumped isotopes can be used as unequivocal tracers to distinguish secondary microbial methane from thermogenic gases and hence provide the ability to incorporate them separately into global methane budgets.</div></div>","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":"647 ","pages":"Article 119023"},"PeriodicalIF":4.8,"publicationDate":"2024-10-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142419380","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Experimental investigation of hydrogen isotope fractionation during hydration of olivine-hosted melt inclusions: Implications for D/H in Baffin Island picrites","authors":"Yuxiang Zhang ,&nbsp;Glenn Gaetani ,&nbsp;Ayla Pamukçu ,&nbsp;Brian Monteleone ,&nbsp;Lee Saper","doi":"10.1016/j.epsl.2024.119052","DOIUrl":"10.1016/j.epsl.2024.119052","url":null,"abstract":"<div><div>Olivine-hosted melt inclusions are used to investigate the hydrogen isotope compositions (D/H) of Earth's mantle reservoirs. Studies have shown, however, that hydrogen in melt inclusion can equilibrate rapidly in response to changes to the external environment via the diffusion of protons (H⁺) and deuterons (D⁺) through the host olivine. Given that protons diffuse faster than deuterons, a kinetic fractionation of hydrogen isotopes is expected to accompany both the hydration and dehydration of melt inclusions. Other volatile species in the melt inclusion may also be affected by changes to the internal pressure and/or oxygen fugacity (<em>f</em>O₂). Here we report results from experiments designed to investigate the behaviors of volatiles and hydrogen isotopes during the hydration of olivine-hosted melt inclusions. We show that the concentration of H₂O in initially H₂O-poor inclusions increases rapidly (up to ∼4 wt.% within 24 h) when the host olivine is in contact with aqueous fluid at 1200 °C and 300 MPa. The extent of hydration is controlled by time, temperature, melt inclusion volume, and H⁺ diffusion distance. Hydrogen isotopes initially become lighter (i.e., D/H decreases) as hydration proceeds, defining a negative correlation with H₂O concentration. This trend reverses with increasing hydration as the inclusions must eventually equilibrate with the external fluid. These experimental results agree well with diffusion calculations carried out using a spherical geometry and a lattice diffusivity of 10^–11.2±0.2 m²/s for H⁺ at 1200 °C. Therefore, anomalously light hydrogen isotopes in olivine-hosted melt inclusions from Baffin Island may not be taken as representative of the composition of the mantle source unless post-entrapment hydration can be excluded as a possibility. An increase in CO₂ concentration and a significant drop in sulfur concentration accompany hydration of the melt inclusions in our experiments. The former is consistent with an observed decrease in vapor bubble size and results from a hydration-induced internal pressure increase. The latter is ascribed to the exsolution of molten sulfide from the silicate melt, which might be related to a lower <em>f</em>O₂ in the experiments as compared to the starting materials. We find no evidence for exchange of F or Cl between the melt inclusion and external fluid.</div></div>","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":"647 ","pages":"Article 119052"},"PeriodicalIF":4.8,"publicationDate":"2024-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142419379","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Regional-scale, high-resolution measurements of hilltop curvature reveal tectonic, climatic, and lithologic controls on hillslope morphology","authors":"William T. Struble ,&nbsp;Fiona J. Clubb ,&nbsp;Joshua J. Roering","doi":"10.1016/j.epsl.2024.119044","DOIUrl":"10.1016/j.epsl.2024.119044","url":null,"abstract":"<div><div>Climate, tectonics, lithology, and biology are encoded within the morphology of landforms. Hillslopes record uplift and erosion rate through hilltop curvature, in which sharper, more convex hilltops correspond with more rapid erosion rates. However, past hilltop curvature studies that map uplift and erosion rates have been limited to small spatial scales largely due to relatively slow speeds of curvature measurement techniques. This lack of regional-scale observations has made deconvolving the relative contributions of tectonics, climate, and lithology to hillslope morphology a challenge. Here, we used high performance computing and continuous wavelet transforms of topography to rapidly map hilltop curvature in the steep and dissected Oregon Coast Range (OCR) and the adjacent gentler Cascadia Forearc Lowland (CFL) in western Oregon, amounting to ∼43,000 km² of 1 m lidar data. We additionally compared mapped hilltop curvature to published erosion rates derived from cosmogenic ¹⁰Be, including 11 newly sampled watersheds. We observed that hilltops are systematically sharper in the OCR than in the CFL, and we noted a linear relationship between catchment-averaged erosion rate and hilltop curvature, consistent with previous observations and theory that erosion rate scales linearly with hilltop curvature in soil-mantled landscapes. The boundary between the OCR and CFL, as demarcated by hilltop curvature, is often abrupt and occurs across mapped structures that separate disparate baselevels but where lithology and mean annual precipitation remain constant. Thus, while we observed significant variability in hilltop curvature that results from secondary lithologic and climatic controls, our results demonstrate that hillslope morphology in western Oregon is set primarily by uplift via tectonically-controlled baselevel lowering rates. These regional interpretations additionally highlight the computational advantages of the wavelet transform for rapidly quantifying hilltop curvature.</div></div>","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":"647 ","pages":"Article 119044"},"PeriodicalIF":4.8,"publicationDate":"2024-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142419378","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Martian seismic anisotropy underneath Elysium Planitia revealed by direct S wave splitting","authors":"Jing Shi ,&nbsp;Cunrui Han ,&nbsp;Tao Wang ,&nbsp;Chao Qi ,&nbsp;Han Chen ,&nbsp;Zhihan Yu ,&nbsp;Jiaqi Geng ,&nbsp;Minghan Yang ,&nbsp;Xu Wang ,&nbsp;Ling Chen ,&nbsp;Hejiu Hui","doi":"10.1016/j.epsl.2024.119047","DOIUrl":"10.1016/j.epsl.2024.119047","url":null,"abstract":"<div><div>Seismic anisotropy, arising from the crystallographic/lattice-preferred orientation of anisotropic minerals or the shape-preferred orientation of melts or cracks, can establish a critical link between Mars's past evolution and its current state. So far, seismic anisotropy in Mars has been proposed due to different velocities of vertically and horizontally polarized shear waves in the Martian crust, obtained from crustal converted waves, multiples, and surface waves recorded by the InSight seismometer. However, the shear wave splitting, which stands out as a straightforward indicator of seismic anisotropy, has not been reported using marsquake records. In this study, we employ low-frequency marsquakes detected by the InSight seismometer to reveal shear wave splitting in marsquake recordings. We find that the direct <em>S</em> waves of three marsquake recordings (S0173a, S0235b, and S1133c) with high signal-to-noise ratios exhibit the splitting phenomenon. We rule out the possibility of apparent anisotropy through synthetic tests, affirming the presence of seismic anisotropy in Mars. The delay time measured from the direct <em>S</em> wave splitting is too large to be solely attributed to the seismic anisotropy in the upper crust (0 – 10 km) beneath the InSight. Thus, seismic anisotropy in the deeper region of Mars is required. Combined with other geophysical evidence near the InSight landing site, the seismic anisotropy observed in this study implies the aligned cracks in the crust are greater than 10 km beneath the InSight and/or the existence of mantle flow underneath the Elysium Planitia of Mars.</div></div>","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":"647 ","pages":"Article 119047"},"PeriodicalIF":4.8,"publicationDate":"2024-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142419375","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Long-term isostatic relaxation of large terrestrial impact structures: structural characteristics inferred from scaled analogue experiments","authors":"Jan Oliver Eisermann,&nbsp;Ulrich Riller","doi":"10.1016/j.epsl.2024.119029","DOIUrl":"10.1016/j.epsl.2024.119029","url":null,"abstract":"<div><div>Crater floor fractures are prominent post-cratering structural vestiges that are known from large impact craters on rocky celestial bodies. Two mechanisms have been proposed to explain the formation of crater floor fractures: emplacement of horizontal igneous sheets below crater floors and isostatic re-equilibration of crust underlying target rocks, i.e., crustal relaxation. Here, we use two-layer analogue experiments to model the deformation of lower and upper crust following crater formation, scaled to the physical conditions on Earth, to explore the structural and kinematic consequences of crustal relaxation. Specifically, the structural evolution of model upper crust was systematically analysed for various initial depths and diameters of crater floors, gleaned from previous numerical models for average continental crust. The analogue modelling results provide quantitative estimates of the duration, geometry and distribution of deformation zones in the upper crust and, for the first time, a quantitative relationship between the diameter, depth and fracture geometry of crater floors. The experiments also show that crater floor uplift is accomplished by long-wavelength subsidence of the crater periphery, which may operate on time scales of hundreds of thousands of years in nature. We conclude that patterns of natural crater floor fractures, including impact melt rock dikes known from the Sudbury and Vredefort impact structures, can be caused by long-term uplift of the crater floor, compensated by lateral crustal flow toward the crater centre.</div></div>","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":"647 ","pages":"Article 119029"},"PeriodicalIF":4.8,"publicationDate":"2024-09-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142359451","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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":"A distinct type of MORB formed by two-stage melting of a hybrid mantle during Gondwana breakup","authors":"Maxim Portnyagin ,&nbsp;Antje Dürkefälden ,&nbsp;Folkmar Hauff ,&nbsp;Andrey Gurenko ,&nbsp;Daniel A. Frick ,&nbsp;Dieter Garbe-Schönberg ,&nbsp;Kaj Hoernle","doi":"10.1016/j.epsl.2024.119021","DOIUrl":"10.1016/j.epsl.2024.119021","url":null,"abstract":"<div><div>The nature of magmatism associated with the breakup of the Gondwana supercontinent remains controversial. Here we report compositions of volcanic glasses from Jurassic (∼155 Ma) seafloor adjacent to the Investigator Ridge, providing new insights on magma generation in the embryonic Indian Ocean. These samples have exceptionally primitive compositions with the highest MgO (∼10.6 wt%) content found thus far in mid-ocean-ridge basalt (MORB) glasses globally. They also have FeO-rich (∼10 wt%) compositions, strongly fractionated HREE patterns (Dy/Yb ∼1.24 versus 1.4–1.5 in the prevailing mantle), highly depleted contents of moderately incompatible elements (Zr, MREE) but elevated contents of highly incompatible elements and enriched Sr–Nd–Hf–Pb isotopic characteristics. A long-lived and hot mantle plume may not be required to explain the composition of these basalts associated with more typical but also Fe-rich MORB in the Argo Basin. Instead, we propose that these magmas can originate at normal or only moderately elevated temperatures from less magnesian mantle consisting of undepleted high-Mg# peridotite and residual, previously melted under thick continental lithosphere low-Mg# eclogite, likely MORB-like recycled oceanic crust. Re-melting of such hybrid mantle occurred during continental breakup, possibly due to induced active upwelling at continental edges and involved interaction with trace element and isotopically enriched subcontinental lithosphere. Together with basalts from the Red Sea deeps, the Jurassic rocks from the Indian Ocean represent a distinct type of MORB formed by multi-stage melting of lithologically heterogeneous mantle during continental breakup.</div></div>","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":"647 ","pages":"Article 119021"},"PeriodicalIF":4.8,"publicationDate":"2024-09-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142359452","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}