The widely distributed pitted cones in Utopia Planitia have several explanations, and they have been interpreted as mud volcanoes in the Zhurong landing area. The morphology and distribution characteristics of mud volcano cones can serve as indicators of stress direction and can also be used to calculate potential depth for mud sources. This information may assist in elucidating the potential formational scenarios of the mud volcanoes, which is of great significance to study the tectonic evolution in Utopia Planitia and possible water ice depths. The digital orthophoto map (DOM) and the digital elevation model (DEM) with spatial resolutions of 0.7 m and 3 m obtained by High Resolution Imaging Camera (HiRIC) from Tianwen-1 show that the mud volcanoes are distributed as both isolated cones and clustered cones in the Zhurong landing area. The age of the mud volcanoes is limited to the middle to late Amazonian (∼2.0 Ga - 400 Ma) based on the crater size-frequency distribution (CSFD); the depth range of the mud source is estimated to be ∼0.6–7.2 km by self-similar clustering analysis. The orientations of the aligned cones and the elongated mud vents indicate that the maximum horizontal stress (SH) directions during the formation of the mud volcanoes in the landing area are in the direction of N67°E, which is in good agreement with the orientations of the nearby troughs, suggesting that the formation of the mud volcanoes in the landing area may have been controlled by the fracturing of the lower part of the troughs. These features, compared with those reported in previous study of mud volcanism/cone morphology on Mars, collectively suggest that the mud volcanoes in the landing area may have formed in a geological scenario under conditions of volcanic destabilization. Further, the formation of the mud volcanoes, with the analysis of the SH, may have been influenced by both basin subsidence and the volcanism in the Elysium region. This study provides a new example of Martian mud volcano geologic formation scenarios, offers the feasibility of using the SH to analyze Martian mud volcano formation, and hints at active geologic phenomena on Mars during the Amazonian period.
乌托邦星广泛分布的凹陷锥体有多种解释，它们被解释为祝融着陆区的泥火山。泥火山锥体的形态和分布特征可以作为应力方向的指标，也可用于计算泥源的潜在深度。这些信息有助于阐明泥火山的潜在形成情况，对研究桃花江地块的构造演化和可能的水冰深度具有重要意义。天文一号高分辨率成像相机（HiRIC）获得的空间分辨率分别为0.7米和3米的数字正射影像图（DOM）和数字高程模型（DEM）显示，泥火山在祝融着陆区以孤立锥体和群集锥体两种形式分布。根据火山口大小-频率分布（CSFD），将泥火山的年龄限定在亚马逊中晚期（∼2.0 Ga - 400 Ma）；通过自相似聚类分析，估计泥源的深度范围为∼0.6-7.2 km。从排列的圆锥体和拉长的泥喷口的方向来看，着陆区泥火山形成过程中的最大水平应力（SH）方向为N67°E，这与附近海槽的走向十分吻合，表明着陆区泥火山的形成可能受海槽下部断裂的控制。这些特征与以往火星泥火山/火山锥形态研究中报告的特征相比，共同表明着陆区的泥火山可能是在火山不稳定的地质条件下形成的。此外，根据对SH的分析，泥火山的形成可能受到了盆地沉降和极乐地区火山活动的影响。这项研究为火星泥火山地质形成情景提供了一个新的实例，提供了利用SH分析火星泥火山形成的可行性，并暗示了亚马逊时期火星上活跃的地质现象。
{"title":"Potential formational scenarios of the mud volcanoes in the Zhurong landing area in Utopia Planitia, observed by Tianwen-1","authors":"Jingjing Zhang , Xin Ren , Yuan Chen , Hongbo Zhang , Zhibin Li , Zhaopeng Chen , Wenhui Wu , Wei Yan , Wangli Chen , Xiaoxia Zhang","doi":"10.1016/j.epsl.2024.119024","DOIUrl":"10.1016/j.epsl.2024.119024","url":null,"abstract":"<div><div>The widely distributed pitted cones in Utopia Planitia have several explanations, and they have been interpreted as mud volcanoes in the Zhurong landing area. The morphology and distribution characteristics of mud volcano cones can serve as indicators of stress direction and can also be used to calculate potential depth for mud sources. This information may assist in elucidating the potential formational scenarios of the mud volcanoes, which is of great significance to study the tectonic evolution in Utopia Planitia and possible water ice depths. The digital orthophoto map (DOM) and the digital elevation model (DEM) with spatial resolutions of 0.7 m and 3 m obtained by High Resolution Imaging Camera (HiRIC) from Tianwen-1 show that the mud volcanoes are distributed as both isolated cones and clustered cones in the Zhurong landing area. The age of the mud volcanoes is limited to the middle to late Amazonian (∼2.0 Ga - 400 Ma) based on the crater size-frequency distribution (CSFD); the depth range of the mud source is estimated to be ∼0.6–7.2 km by self-similar clustering analysis. The orientations of the aligned cones and the elongated mud vents indicate that the maximum horizontal stress (S<sub>H</sub>) directions during the formation of the mud volcanoes in the landing area are in the direction of N67°E, which is in good agreement with the orientations of the nearby troughs, suggesting that the formation of the mud volcanoes in the landing area may have been controlled by the fracturing of the lower part of the troughs. These features, compared with those reported in previous study of mud volcanism/cone morphology on Mars, collectively suggest that the mud volcanoes in the landing area may have formed in a geological scenario under conditions of volcanic destabilization. Further, the formation of the mud volcanoes, with the analysis of the S<sub>H</sub>, may have been influenced by both basin subsidence and the volcanism in the Elysium region. This study provides a new example of Martian mud volcano geologic formation scenarios, offers the feasibility of using the S<sub>H</sub> to analyze Martian mud volcano formation, and hints at active geologic phenomena on Mars during the Amazonian period.</div></div>","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":"647 ","pages":"Article 119024"},"PeriodicalIF":4.8,"publicationDate":"2024-09-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142326700","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}
Pub Date : 2024-09-27DOI: 10.1016/j.epsl.2024.118987
Erik J. Schoonover , Michael R. Ackerson , Joshua M. Garber , Andrew J. Smye , Andrew R. Kylander-Clark , Jesse R. Reimink
Upper-crustal granitoids are a late-stage product of crustal differentiation. This last stage in the evolution has been proposed to be the key interval that governs volcanic eruptions, ore formation, and fluid migration. Though numerous techniques have been employed to understand the evolution of late-stage felsic magmas, there remains little agreement regarding their crystallization histories. Here we use laser ablation depth profiling of zircon trace elements to probe the thermochemical evolution of well-characterized granitoid rocks from the Tuolumne Intrusive Suite (CA, USA). In combination with titanite trace-element data, we can determine the T-X trajectory of the magmatic system during zircon growth at the latest stage of crystallization. Our data also allows for a robust empirical calibration of the widely used Ti-in-zircon thermometer arising from the onset of titanite crystallization captured in zircon rims. These data show that Tuolumne zircon growth occurred at an aTiO2 of 0.4–0.5, which is lower than many previous estimates. We further model zircon growth up- and down-temperature from titanite saturation, and document extended thermochemical growth records preserved in zircons from these upper-crustal melts. The calculated temperatures are consistent with zircon growth from 775 to 625 °C, indicating that zircon growth occurred over a wide temperature range down to, or potentially below, the water-saturated granite solidus. These findings provide empirically-calibrated values for use in other Ti-in-zircon and Zr-in-titanite temperature calculations, particularly to understand late-stage, low-temperature melts in granitoid systems.
{"title":"Snapshots of magmatic evolution revealed by zircon depth profiling","authors":"Erik J. Schoonover , Michael R. Ackerson , Joshua M. Garber , Andrew J. Smye , Andrew R. Kylander-Clark , Jesse R. Reimink","doi":"10.1016/j.epsl.2024.118987","DOIUrl":"10.1016/j.epsl.2024.118987","url":null,"abstract":"<div><div>Upper-crustal granitoids are a late-stage product of crustal differentiation. This last stage in the evolution has been proposed to be the key interval that governs volcanic eruptions, ore formation, and fluid migration. Though numerous techniques have been employed to understand the evolution of late-stage felsic magmas, there remains little agreement regarding their crystallization histories. Here we use laser ablation depth profiling of zircon trace elements to probe the thermochemical evolution of well-characterized granitoid rocks from the Tuolumne Intrusive Suite (CA, USA). In combination with titanite trace-element data, we can determine the <em>T-X</em> trajectory of the magmatic system during zircon growth at the latest stage of crystallization. Our data also allows for a robust empirical calibration of the widely used Ti-in-zircon thermometer arising from the onset of titanite crystallization captured in zircon rims. These data show that Tuolumne zircon growth occurred at an <em>a</em>TiO<sub>2</sub> of 0.4–0.5, which is lower than many previous estimates. We further model zircon growth up- and down-temperature from titanite saturation, and document extended thermochemical growth records preserved in zircons from these upper-crustal melts. The calculated temperatures are consistent with zircon growth from 775 to 625 °C, indicating that zircon growth occurred over a wide temperature range down to, or potentially below, the water-saturated granite solidus. These findings provide empirically-calibrated values for use in other Ti-in-zircon and Zr-in-titanite temperature calculations, particularly to understand late-stage, low-temperature melts in granitoid systems.</div></div>","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":"647 ","pages":"Article 118987"},"PeriodicalIF":4.8,"publicationDate":"2024-09-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142326698","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}
Pub Date : 2024-09-27DOI: 10.1016/j.epsl.2024.119018
Samyak Pradhan, Indra Sekhar Sen
The carbon budget of the Himalayan-Tibetan orogen often neglects the poorly constrained CO2 fluxes from the mantle and metamorphism that emerge directly from hot springs or diffusely through the soil, which can potentially warm the climate. What exists are either metamorphic phase relations, thermodynamic model-based CO2 flux estimates, or field-based estimates in a single catchment extrapolated to the entire orogen having diverse geological and tectonics characteristics, heat flow, and hydrological regimes. Here, we apply a steady-state isotope mass balance model to observations of carbon isotope ratios to quantify the fluxes of CO2 degassed using a global compilation of hot springs located on the fault systems of the Himalayan Tibetan orogen. We estimate that the hot springs could degas up to ∼84 % of the dissolved CO2, releasing up to 1.5 ± 1.0 × 1011 mol CO2 yr-1. When combined with diffused soil CO2 emissions, the Himalayan Tibetan orogen has the potential to emit 3.0 ± 1.3 × 1011 mol CO2 yr-1, which is similar in magnitude to CO2 emission from continental rifts as well as the CO2 drawdown due to silicate weathering in the orogen. We find that CO2 released from the catchments of Himalayan-Tibetan orogen is primarily controlled by metamorphic processes , with secondary controls from mantle degassing , and carbonate dissolution (%) and is insensitive to contributions from younger biospheric sources. Reevaluation of the geological carbon budget in Narayani Basin, Nepal, shows that metamorphic CO2 in the collisional orogen is comparable to other carbon sources and sinks. We conclude that metamorphic CO2 could offset the CO2 drawdown by silicate weathering and OCbiosphere burial in the Himalayan-Tibet orogen, resulting in global warming over million-year time scales.
{"title":"Metamorphic CO2 fluxes offset the net geological carbon sink in the Himalayan-Tibetan orogen","authors":"Samyak Pradhan, Indra Sekhar Sen","doi":"10.1016/j.epsl.2024.119018","DOIUrl":"10.1016/j.epsl.2024.119018","url":null,"abstract":"<div><div>The carbon budget of the Himalayan-Tibetan orogen often neglects the poorly constrained CO<sub>2</sub> fluxes from the mantle and metamorphism that emerge directly from hot springs or diffusely through the soil, which can potentially warm the climate. What exists are either metamorphic phase relations, thermodynamic model-based CO<sub>2</sub> flux estimates, or field-based estimates in a single catchment extrapolated to the entire orogen having diverse geological and tectonics characteristics, heat flow, and hydrological regimes. Here, we apply a steady-state isotope mass balance model to observations of carbon isotope ratios to quantify the fluxes of CO<sub>2</sub> degassed using a global compilation of hot springs located on the fault systems of the Himalayan Tibetan orogen. We estimate that the hot springs could degas up to ∼84 % of the dissolved CO<sub>2</sub>, releasing up to 1.5 ± 1.0 × 10<sup>11</sup> mol CO<sub>2</sub> yr<sup>-1</sup>. When combined with diffused soil CO<sub>2</sub> emissions, the Himalayan Tibetan orogen has the potential to emit 3.0 ± 1.3 × 10<sup>11</sup> mol CO<sub>2</sub> yr<sup>-1</sup>, which is similar in magnitude to CO<sub>2</sub> emission from continental rifts as well as the CO<sub>2</sub> drawdown due to silicate weathering in the orogen. We find that CO<sub>2</sub> released from the catchments of Himalayan-Tibetan orogen is primarily controlled by metamorphic processes <span><math><mrow><mo>(</mo><msubsup><mn>79</mn><mrow><mo>−</mo><mn>25</mn></mrow><mrow><mo>+</mo><mn>21</mn></mrow></msubsup><mrow><mspace></mspace><mo>%</mo></mrow><mo>)</mo></mrow></math></span>, with secondary controls from mantle degassing <span><math><mrow><mo>(</mo><msubsup><mn>7</mn><mrow><mo>−</mo><mn>7</mn></mrow><mrow><mo>+</mo><mn>17</mn></mrow></msubsup><mrow><mspace></mspace><mo>%</mo></mrow><mo>)</mo></mrow></math></span>, and carbonate dissolution (<span><math><mrow><msubsup><mn>14</mn><mrow><mo>−</mo><mn>14</mn></mrow><mrow><mo>+</mo><mn>26</mn></mrow></msubsup><mspace></mspace></mrow></math></span>%) and is insensitive to contributions from younger biospheric sources. Reevaluation of the geological carbon budget in Narayani Basin, Nepal, shows that metamorphic CO<sub>2</sub> in the collisional orogen is comparable to other carbon sources and sinks. We conclude that metamorphic CO<sub>2</sub> could offset the CO<sub>2</sub> drawdown by silicate weathering and OC<sub>biosphere</sub> burial in the Himalayan-Tibet orogen, resulting in global warming over million-year time scales.</div></div>","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":"647 ","pages":"Article 119018"},"PeriodicalIF":4.8,"publicationDate":"2024-09-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142326699","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}
Pub Date : 2024-09-26DOI: 10.1016/j.epsl.2024.119020
Anna M. Rebaza , Ananya Mallik , Emily H.G. Cooperdock , Bridgett I. Holman
<div><div>Buoyant ultramafic-rich (serpentine- or chlorite-rich) mélange diapirs in sediment-starved subduction zones can transport slab material to arc sources. While the buoyancy of chlorite-rich mélanges was previously investigated, serpentine-rich mélanges were never explored. Thus, the overall contribution of ultramafic-rich mélanges to buoyancy, the conditions for diapir formation, and their fate in subduction zones are not well constrained. Here, we investigate the partial melting behavior and the associated density transformations of a serpentine-rich matrix (5–10 wt.% H<sub>2</sub>O) with minor sediments (9:1 ratio) at fore-arc (∼65 km) to sub-arc (∼95 km) depths (2–3 GPa and 800–1250 °C) and compare to that of chlorite-rich mélanges from the literature. Our results show that the solidus of serpentine-rich matrices is between 1050 and 1100 °C and requires either diapiric rise of the mélange into the hotter mantle wedge or interactions with a hotter asthenosphere through slab tears to partially melt and produce basaltic melts, whether in hot or cold slab channels. Chlorite-rich mélanges may account for the sources of some arc lavas, but partial melting of serpentine-rich mélanges produce melts depleted in CaO, TiO<sub>2</sub>, alkalis, and are highly enriched in MgO compared to basaltic arc lavas. Both serpentine-rich and chlorite-rich matrices dehydrate to form denser peridotite and lose buoyancy at ∼800 °C and ≥1000 °C, respectively. Even if diapirism initiates in such mélanges near the slab-mantle interface, they would likely lose buoyancy upon ascent into the hotter mantle wedge resulting in stalled or failed diapirs. Diapir growth (τa) is controlled by the interplay of density, thickness and viscosity of the mélange, as well as the timescale of slab subduction (τs) and thermal structure of the subduction zone. We observe that the onset of diapirs in cold subduction zones requires mélanges that may sometimes be thicker than that observed by field and geophysical studies, while hot subduction zones overall require thinner mélanges. Thus, ultramafic-rich mélange diapirs may occur but only under specific conditions and when the diapiric ascent timescale is faster than the thermal equilibration barrier of ∼800–1000 °C (especially at the core of the mélange). Dehydration or partial melting of ultramafic-rich mélanges can affect the large ion lithophile element (LILE), volatiles, and high-field strength element (HFSE) budgets in the mantle wedge. Partial melting (caused by a diapiric rise or slab tear) does not fractionate LILEs from HFSEs at <em>T</em> ≥ 1100 °C and if the mélange has a lower LILE/HFSE to begin with, that signature is transferred to arc sources. Dehydration releases aqueous fluids rich in fluid-mobile elements (LILE and volatiles) relative to HFSE. Thus, the characteristic high LILE/HFSE signature of aqueous fluids is transferred to arc magma sources. Given high LILE/HFSE ratio is a ubiquitous arc magma signature, but slab
{"title":"The fate of ultramafic-rich mélanges in cold to hot subduction zones: Implications for diapirism (or not) and chemical geodynamics","authors":"Anna M. Rebaza , Ananya Mallik , Emily H.G. Cooperdock , Bridgett I. Holman","doi":"10.1016/j.epsl.2024.119020","DOIUrl":"10.1016/j.epsl.2024.119020","url":null,"abstract":"<div><div>Buoyant ultramafic-rich (serpentine- or chlorite-rich) mélange diapirs in sediment-starved subduction zones can transport slab material to arc sources. While the buoyancy of chlorite-rich mélanges was previously investigated, serpentine-rich mélanges were never explored. Thus, the overall contribution of ultramafic-rich mélanges to buoyancy, the conditions for diapir formation, and their fate in subduction zones are not well constrained. Here, we investigate the partial melting behavior and the associated density transformations of a serpentine-rich matrix (5–10 wt.% H<sub>2</sub>O) with minor sediments (9:1 ratio) at fore-arc (∼65 km) to sub-arc (∼95 km) depths (2–3 GPa and 800–1250 °C) and compare to that of chlorite-rich mélanges from the literature. Our results show that the solidus of serpentine-rich matrices is between 1050 and 1100 °C and requires either diapiric rise of the mélange into the hotter mantle wedge or interactions with a hotter asthenosphere through slab tears to partially melt and produce basaltic melts, whether in hot or cold slab channels. Chlorite-rich mélanges may account for the sources of some arc lavas, but partial melting of serpentine-rich mélanges produce melts depleted in CaO, TiO<sub>2</sub>, alkalis, and are highly enriched in MgO compared to basaltic arc lavas. Both serpentine-rich and chlorite-rich matrices dehydrate to form denser peridotite and lose buoyancy at ∼800 °C and ≥1000 °C, respectively. Even if diapirism initiates in such mélanges near the slab-mantle interface, they would likely lose buoyancy upon ascent into the hotter mantle wedge resulting in stalled or failed diapirs. Diapir growth (τa) is controlled by the interplay of density, thickness and viscosity of the mélange, as well as the timescale of slab subduction (τs) and thermal structure of the subduction zone. We observe that the onset of diapirs in cold subduction zones requires mélanges that may sometimes be thicker than that observed by field and geophysical studies, while hot subduction zones overall require thinner mélanges. Thus, ultramafic-rich mélange diapirs may occur but only under specific conditions and when the diapiric ascent timescale is faster than the thermal equilibration barrier of ∼800–1000 °C (especially at the core of the mélange). Dehydration or partial melting of ultramafic-rich mélanges can affect the large ion lithophile element (LILE), volatiles, and high-field strength element (HFSE) budgets in the mantle wedge. Partial melting (caused by a diapiric rise or slab tear) does not fractionate LILEs from HFSEs at <em>T</em> ≥ 1100 °C and if the mélange has a lower LILE/HFSE to begin with, that signature is transferred to arc sources. Dehydration releases aqueous fluids rich in fluid-mobile elements (LILE and volatiles) relative to HFSE. Thus, the characteristic high LILE/HFSE signature of aqueous fluids is transferred to arc magma sources. Given high LILE/HFSE ratio is a ubiquitous arc magma signature, but slab","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":"647 ","pages":"Article 119020"},"PeriodicalIF":4.8,"publicationDate":"2024-09-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142322750","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}
Pub Date : 2024-09-24DOI: 10.1016/j.epsl.2024.119019
Zheng Tang , Jordi Julià , Walter D. Mooney , Yanqiang Wu
A uniform image of the mantle transition zone (MTZ) beneath western China and neighboring regions is produced through Variable Bin Radius Stacking of receiver functions. We utilized a large data set of 218,050 receiver functions from 1,991 broadband seismic stations. Our results, after 3-D velocity corrections, show significant lateral variations in topography of the 410- and 660-km discontinuity and thickness of the MTZ. The observed lateral variations of the MTZ correlate with seismic-velocity anomalies identified in independent tomographic studies, which are interpreted as cold and hot thermal anomalies from lithospheric downwellings and mantle upwellings, respectively. In the southern Tibetan Plateau, the MTZ topography reveals four segmented zones of up to ∼20 km thicker-than-average MTZ from west to east interfingered with regions of thin-to-normal MTZ. These segmented MTZ thickenings likely originate from a series of cold lithospheric fingers associated with the fragmented subduction of the Indian lithosphere, while the thin-to-normal MTZ may result from an absence of the subducting Indian slab. These observations provide novel evidence for the proposed fragmentation of the Indian subduction. Moreover, we observe regions of thickened MTZ under the Tien Shan orogen and the Qaidam block, which likely result from the foundering of cold delaminated/broken-off lithospheric blocks triggered by the underthrusting of the Junggar and Tarim blocks. Regions of thinned MTZ beneath the Tien Shan region are additionally observed, which could be attributed to counterflow upwellings.
{"title":"Receiver function image of the mantle transition zone beneath western China: Fragmented subduction and counterflow upwelling","authors":"Zheng Tang , Jordi Julià , Walter D. Mooney , Yanqiang Wu","doi":"10.1016/j.epsl.2024.119019","DOIUrl":"10.1016/j.epsl.2024.119019","url":null,"abstract":"<div><div>A uniform image of the mantle transition zone (MTZ) beneath western China and neighboring regions is produced through Variable Bin Radius Stacking of receiver functions. We utilized a large data set of 218,050 receiver functions from 1,991 broadband seismic stations. Our results, after 3-D velocity corrections, show significant lateral variations in topography of the 410- and 660-km discontinuity and thickness of the MTZ. The observed lateral variations of the MTZ correlate with seismic-velocity anomalies identified in independent tomographic studies, which are interpreted as cold and hot thermal anomalies from lithospheric downwellings and mantle upwellings, respectively. In the southern Tibetan Plateau, the MTZ topography reveals four segmented zones of up to ∼20 km thicker-than-average MTZ from west to east interfingered with regions of thin-to-normal MTZ. These segmented MTZ thickenings likely originate from a series of cold lithospheric fingers associated with the fragmented subduction of the Indian lithosphere, while the thin-to-normal MTZ may result from an absence of the subducting Indian slab. These observations provide novel evidence for the proposed fragmentation of the Indian subduction. Moreover, we observe regions of thickened MTZ under the Tien Shan orogen and the Qaidam block, which likely result from the foundering of cold delaminated/broken-off lithospheric blocks triggered by the underthrusting of the Junggar and Tarim blocks. Regions of thinned MTZ beneath the Tien Shan region are additionally observed, which could be attributed to counterflow upwellings.</div></div>","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":"647 ","pages":"Article 119019"},"PeriodicalIF":4.8,"publicationDate":"2024-09-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142315997","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}
Pub Date : 2024-09-24DOI: 10.1016/j.epsl.2024.119009
Gabriel Orozco , Luis E. Lara , Andrés Tassara
The interaction between upwelling plumes and the oceanic lithosphere can provide important clues about the internal structure and dynamics of the Earth. Plume-derived processes disturb the lithosphere at different depths, amplitudes, and wavelengths. While the spatially wider process is dynamic uplift, commonly described as on the order of 1000 km wide and 1 km high bathymetric swell, volcanism is the most focused plume manifestation. These two end-members are commonly described and measured in terms of volumetric rates, such as buoyancy flux and volcanic production rate, respectively. However, intermediate processes such as magmatic trapping at lithospheric depths, although reported, has remained less studied. While the topographic separation between volcanic and regional (non-volcanic) features has numerous developments, the recognition of signatures of processes occurring at intermediate depths is a problem that has been less studied.
To better understand the relationship between plate structure and the distribution of plume effects, we investigated the spatial distribution of topographic plume signatures on the relatively fast and thin oceanic Nazca plate. Using morphological criteria, we adjusted the width of two filtered surfaces, which together allow us to divide the bathymetric anomalies into three components that could be reflecting morphological features supported below, inside, and above the plate.
The resulting decomposition suggests the existence of two superimposed components of swells on the Nazca plate, contrasting in distribution, morphology, and nature: local swells exhibit a clear spatial correlation with volcanic chains. The regional swell component in turn collectively encompasses all hotspots in the Nazca plate and show widths up to 2000 km. We hypothesize distinct driving processes for both swell components, with local swells connected to the intra-lithospheric domain and regional swells probably associated with sub-lithospheric processes.
{"title":"Characterization and geodynamic interpretation of Nazca Plate bathymetric anomalies","authors":"Gabriel Orozco , Luis E. Lara , Andrés Tassara","doi":"10.1016/j.epsl.2024.119009","DOIUrl":"10.1016/j.epsl.2024.119009","url":null,"abstract":"<div><div>The interaction between upwelling plumes and the oceanic lithosphere can provide important clues about the internal structure and dynamics of the Earth. Plume-derived processes disturb the lithosphere at different depths, amplitudes, and wavelengths. While the spatially wider process is dynamic uplift, commonly described as on the order of 1000 km wide and 1 km high bathymetric swell, volcanism is the most focused plume manifestation. These two end-members are commonly described and measured in terms of volumetric rates, such as buoyancy flux and volcanic production rate, respectively. However, intermediate processes such as magmatic trapping at lithospheric depths, although reported, has remained less studied. While the topographic separation between volcanic and regional (non-volcanic) features has numerous developments, the recognition of signatures of processes occurring at intermediate depths is a problem that has been less studied.</div><div>To better understand the relationship between plate structure and the distribution of plume effects, we investigated the spatial distribution of topographic plume signatures on the relatively fast and thin oceanic Nazca plate. Using morphological criteria, we adjusted the width of two filtered surfaces, which together allow us to divide the bathymetric anomalies into three components that could be reflecting morphological features supported below, inside, and above the plate.</div><div>The resulting decomposition suggests the existence of two superimposed components of swells on the Nazca plate, contrasting in distribution, morphology, and nature: local swells exhibit a clear spatial correlation with volcanic chains. The regional swell component in turn collectively encompasses all hotspots in the Nazca plate and show widths up to 2000 km. We hypothesize distinct driving processes for both swell components, with local swells connected to the intra-lithospheric domain and regional swells probably associated with sub-lithospheric processes.</div></div>","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":"647 ","pages":"Article 119009"},"PeriodicalIF":4.8,"publicationDate":"2024-09-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142315995","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}
Pub Date : 2024-09-24DOI: 10.1016/j.epsl.2024.119022
F.P. Leitzke , J.J. Pakulla , J. Tusch , A. Ravindran , R. Gordilho-Barbosa , S.A. Zincone , M. Hellers , A.A. Martins , R.R. Spreafico , R. Yang , F. Wombacher , J.S.F. Barbosa , C. Münker
The oldest crustal remnants on Earth are represented by greenstone belts and tonalite-trondhjemite-granodiorite (TTG) associations that form most of Archean blocks worldwide. Although several studies reported combined long-lived radiogenic isotope and trace element data of Archean rocks, the chemical evolution of the early Earth is still a matter of debate, often due to younger metamorphic disturbance that overprints primary patterns. To provide further insights, combined data for short-lived (146Sm–142Nd and 182Hf–182W) and long-lived (147Sm–143Nd and 176Lu–176Hf) isotope systems were acquired from a set of Eo- to Paleoarchean amphibolites, TTG gneisses, granites and a gabbroic rock in the northern segment of the São Francisco Craton (SFC) in Brazil, a largely unexplored area regarding short-lived radiogenic isotope datasets. Our samples cover an age range from ca. 3.65 to 3.30 Ga comprising both mafic and felsic rocks. Excesses of µ182W in the samples indicate the presence of a long-lasting Hadean component in the source of Archean rocks from the SFC, which was preserved for at least ca. 1.0 Ga. Conversely, all samples depict µ142Nd similar to modern upper mantle values. The most plausible interpretation of the µ182W and µ142Nd data is a (partially) missing Hadean late veneer component similar to that previously found, for example, at the Pilbara Craton, in NW Australia.
地球上最古老的地壳遗迹以绿岩带和构成全球大部分阿新世岩块的碳酸盐岩-特长闪长岩-花岗闪长岩（TTG）组合为代表。尽管有多项研究报告了阿基坦岩石的长寿命放射性同位素和痕量元素综合数据，但早期地球的化学演化仍是一个争论不休的问题，这往往是由于较年轻的变质扰动覆盖了原生模式。为了提供更深入的见解，我们从巴西圣弗朗西斯科克拉通（SFC）北段的一组始新世至古新世闪长岩、TTG片麻岩、花岗岩和一块辉长岩中获取了短寿命（146Sm-142Nd和182Hf-182W）和长寿命（147Sm-143Nd和176Lu-176Hf）同位素系统的综合数据。我们的样本涵盖了约 3.65 至 3.30 Ga 的年龄范围，包括岩浆岩和长英岩。样品中过量的µ182W表明，在来自SFC的Archean岩石源中存在着一个长效的Hadean成分，它至少保存了约1.0 Ga。1.0 Ga。相反，所有样品的µ142Nd值都与现代上地幔值相似。对µ182W和µ142Nd数据最合理的解释是（部分）缺失的哈代晚期饰面成分，类似于以前在澳大利亚西北部皮尔巴拉克拉通发现的情况。
{"title":"Evidence for a missing late veneer from 182W and 142Nd systematics in the Archean São Francisco Craton","authors":"F.P. Leitzke , J.J. Pakulla , J. Tusch , A. Ravindran , R. Gordilho-Barbosa , S.A. Zincone , M. Hellers , A.A. Martins , R.R. Spreafico , R. Yang , F. Wombacher , J.S.F. Barbosa , C. Münker","doi":"10.1016/j.epsl.2024.119022","DOIUrl":"10.1016/j.epsl.2024.119022","url":null,"abstract":"<div><div>The oldest crustal remnants on Earth are represented by greenstone belts and tonalite-trondhjemite-granodiorite (TTG) associations that form most of Archean blocks worldwide. Although several studies reported combined long-lived radiogenic isotope and trace element data of Archean rocks, the chemical evolution of the early Earth is still a matter of debate, often due to younger metamorphic disturbance that overprints primary patterns. To provide further insights, combined data for short-lived (<sup>146</sup>Sm–<sup>142</sup>Nd and <sup>182</sup>Hf–<sup>182</sup>W) and long-lived (<sup>147</sup>Sm–<sup>143</sup>Nd and <sup>176</sup>Lu–<sup>176</sup>Hf) isotope systems were acquired from a set of Eo- to Paleoarchean amphibolites, TTG gneisses, granites and a gabbroic rock in the northern segment of the São Francisco Craton (SFC) in Brazil, a largely unexplored area regarding short-lived radiogenic isotope datasets. Our samples cover an age range from ca. 3.65 to 3.30 Ga comprising both mafic and felsic rocks. Excesses of µ<sup>182</sup>W in the samples indicate the presence of a long-lasting Hadean component in the source of Archean rocks from the SFC, which was preserved for at least ca. 1.0 Ga. Conversely, all samples depict µ<sup>142</sup>Nd similar to modern upper mantle values. The most plausible interpretation of the µ<sup>182</sup>W and µ<sup>142</sup>Nd data is a (partially) missing Hadean late veneer component similar to that previously found, for example, at the Pilbara Craton, in NW Australia.</div></div>","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":"647 ","pages":"Article 119022"},"PeriodicalIF":4.8,"publicationDate":"2024-09-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142315996","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}
The Xuanlong-type ironstone is a late Paleoproterozoic (∼1.64 Ga) hematite-dominated granular iron formation (GIF) in the North China Craton (NCC). However, recent geochemical studies indicated this GIF was precipitated in a weakly oxygenated environment. The conflicts between the mineral composition of the Xuanlong-type ironstone and its geochemical interpretations can be attributed to the potential occurrence of secondary hematite. Here we used paleomagnetic, rock magnetic measurements and petrographic analysis to determine the mineralization age of the hematite. Our objectives were to determine the primary iron mineralogy and to further explore the paleoenvironmental information preserved in the Xuanlong-type ironstone. Rock magnetic measurements and petrographic analysis identified Al-substituted hematite and siderite as the magnetic minerals. The high-temperature characteristic remanent magnetizations, which passed a C-classification reversal test and a fold test, yielded a paleomagnetic pole position at 51°N, 197°E. This pole position is in close proximity to the coeval paleomagnetic pole reconstructed from the ∼1.64 Ga Cuizhuang Formation in the southern NCC. Therefore, the high-temperature component of the natural remanent magnetization is interpreted as primary remanent magnetization acquired through crystal growth of Al-substituted hematite during early diagenesis. The degree of Al-substitution in hematite seems to be influenced by the alternating dense and porous laminae within the hematitic ooids of Xuanlong-type ironstones. It is hypothesized that these laminae are a result of periodic sea level fluctuations, considering that the ironstones were likely formed in a shallow water setting.
玄龙型铁岩是华北克拉通（NCC）晚古生代（∼1.64 Ga）以赤铁矿为主的粒状铁岩层（GIF）。然而，最近的地球化学研究表明，该GIF是在弱含氧环境中沉淀的。玄龙型铁岩的矿物组成与其地球化学解释之间的矛盾可归因于可能存在的次生赤铁矿。在这里，我们利用古地磁、岩石磁性测量和岩石学分析来确定赤铁矿的成矿年代。我们的目标是确定原生铁矿物学，并进一步探索玄龙型铁岩中保存的古环境信息。岩石磁性测量和岩相分析确定了铝代赤铁矿和菱铁矿为磁性矿物。高温特征剩磁通过了 C 级反转测试和褶皱测试，得出了位于北纬 51°、东经 197°的古地磁极位置。该磁极位置与南昌南部∼1.64Ga崔庄地层重建的共生古磁极位置相近。因此，天然剩磁中的高温成分被解释为在早期成岩过程中通过铝代赤铁矿晶体生长获得的原生剩磁。赤铁矿中的铝置换程度似乎受到玄龙型铁矿赤铁矿卵岩中致密和多孔层状交替的影响。考虑到这些铁石很可能是在浅水环境中形成的，因此推测这些层理是周期性海平面波动的结果。
{"title":"Paleomagnetic constraints on the primary iron minerals of the late Paleoproterozoic Xuanlong-type ironstone in the North China Craton","authors":"Yuhang Cai , Shuan-Hong Zhang , Junling Pei , Yabo Tong , Zaizheng Zhou , Lifu Hou","doi":"10.1016/j.epsl.2024.119013","DOIUrl":"10.1016/j.epsl.2024.119013","url":null,"abstract":"<div><div>The Xuanlong-type ironstone is a late Paleoproterozoic (∼1.64 Ga) hematite-dominated granular iron formation (GIF) in the North China Craton (NCC). However, recent geochemical studies indicated this GIF was precipitated in a weakly oxygenated environment. The conflicts between the mineral composition of the Xuanlong-type ironstone and its geochemical interpretations can be attributed to the potential occurrence of secondary hematite. Here we used paleomagnetic, rock magnetic measurements and petrographic analysis to determine the mineralization age of the hematite. Our objectives were to determine the primary iron mineralogy and to further explore the paleoenvironmental information preserved in the Xuanlong-type ironstone. Rock magnetic measurements and petrographic analysis identified Al-substituted hematite and siderite as the magnetic minerals. The high-temperature characteristic remanent magnetizations, which passed a C-classification reversal test and a fold test, yielded a paleomagnetic pole position at 51°N, 197°E. This pole position is in close proximity to the coeval paleomagnetic pole reconstructed from the ∼1.64 Ga Cuizhuang Formation in the southern NCC. Therefore, the high-temperature component of the natural remanent magnetization is interpreted as primary remanent magnetization acquired through crystal growth of Al-substituted hematite during early diagenesis. The degree of Al-substitution in hematite seems to be influenced by the alternating dense and porous laminae within the hematitic ooids of Xuanlong-type ironstones. It is hypothesized that these laminae are a result of periodic sea level fluctuations, considering that the ironstones were likely formed in a shallow water setting.</div></div>","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":"647 ","pages":"Article 119013"},"PeriodicalIF":4.8,"publicationDate":"2024-09-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142312629","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}
Pub Date : 2024-09-21DOI: 10.1016/j.epsl.2024.119014
Juan Liu , Juye Shi , Yongchao Lu , Xiaojie Fan , Ze Zhang , Rui Zhang , Zhixiang Wang , Ke Xu , Anguo Xiao , David B. Kemp , Chunju Huang
Carbon sources and sinks are primary components of the climate system, but their response to external forcing remain unconstrained, especially for past greenhouse climates. Lakes are important carbon sinks that play a key role in the global carbon cycle. In this study, we investigate organic carbon burial processes and the possible role played by astronomical forcing in low to middle latitude lakes in China during the Eocene. Sediment noise modeling of lake level fluctuations in the three basins suggests that TOC maxima coincided with lake level maxima. We suggest that elevated lake levels likely led to stagnation of bottom waters, thereby promoting the development and preservation of organic matter. Total organic carbon (TOC) data spanning the Eocene from three borehole cores of separate basins show a common cyclicity of ∼1.2 Myr. According to the three TOC time series studied, maxima in TOC are linked to maxima in long-term 1.2 Myr obliquity modulation cycles, with long-term 2.4 Myr eccentricity cycles either at a maxima or minima. Our analysis elucidates a likely control on the burial of organic carbon by long-term astronomical climate cycles. The superposition of different orbital cycles may have driven the process of differential enrichment of organic matter by inducing perturbations in the carbon cycle through nonlinear climate effects. Overall, our chemostratigraphy results illustrate the sensitivity of the terrestrial carbon cycle to orbital forcing on geological timescales.
{"title":"Astronomical forcing of terrestrial organic carbon burial in East Asia during the Eocene","authors":"Juan Liu , Juye Shi , Yongchao Lu , Xiaojie Fan , Ze Zhang , Rui Zhang , Zhixiang Wang , Ke Xu , Anguo Xiao , David B. Kemp , Chunju Huang","doi":"10.1016/j.epsl.2024.119014","DOIUrl":"10.1016/j.epsl.2024.119014","url":null,"abstract":"<div><p>Carbon sources and sinks are primary components of the climate system, but their response to external forcing remain unconstrained, especially for past greenhouse climates. Lakes are important carbon sinks that play a key role in the global carbon cycle. In this study, we investigate organic carbon burial processes and the possible role played by astronomical forcing in low to middle latitude lakes in China during the Eocene. Sediment noise modeling of lake level fluctuations in the three basins suggests that TOC maxima coincided with lake level maxima. We suggest that elevated lake levels likely led to stagnation of bottom waters, thereby promoting the development and preservation of organic matter. Total organic carbon (TOC) data spanning the Eocene from three borehole cores of separate basins show a common cyclicity of ∼1.2 Myr. According to the three TOC time series studied, maxima in TOC are linked to maxima in long-term 1.2 Myr obliquity modulation cycles, with long-term 2.4 Myr eccentricity cycles either at a maxima or minima. Our analysis elucidates a likely control on the burial of organic carbon by long-term astronomical climate cycles. The superposition of different orbital cycles may have driven the process of differential enrichment of organic matter by inducing perturbations in the carbon cycle through nonlinear climate effects. Overall, our chemostratigraphy results illustrate the sensitivity of the terrestrial carbon cycle to orbital forcing on geological timescales.</p></div>","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":"646 ","pages":"Article 119014"},"PeriodicalIF":4.8,"publicationDate":"2024-09-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142272576","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}
Pub Date : 2024-09-21DOI: 10.1016/j.epsl.2024.119015
Haiyang Liu , Ying-Yu Xue , Jörg Geldmacher , Kaj Hoernle , Uwe Wiechert , Shichao An , Hai-Ou Gu , He Sun , Fanfan Tian , Xiaoqiang Li , Kun Wang , Hongli Zhu , Wei-Dong Sun
The Madeira mantle plume is proposed to contain a complete package of recycled oceanic lithosphere. It has not been possible, however, to establish if both lower oceanic crust and peridotitic lithospheric mantle are present within the Madeira magma source. This study reports potassium (K) and oxygen isotope data of lavas from the Madeira Archipelago, which show that δ41K (-0.50 ± 0.06‰ to -0.31 ± 0.01‰) correlates with Sr-Nd-Pb-Hf isotopic compositions, confirming the incorporation of recycled crustal material. The increase in δ41K from Madeira's early shield stage lavas (-0.50 ± 0.06‰ to -0.40 ± 0.05‰) to the subsequent post-erosional stage lavas (-0.34 ± 0.04‰ to -0.31 ± 0.01‰) is consistent with the mantle source becoming progressively depleted in recycled upper oceanic crust (converted to eclogite or pyroxenite) through melt extraction with decreasing age. The post-erosional lavas, however, require a source with higher δ41K values than in depleted peridotitic lithospheric mantle. Modeling demonstrates that during dehydration of high-temperature altered lower oceanic crust, the initial heavy K isotopic signature is preserved, consistent with the high δ41K values of the post-erosional lavas being derived from hydrothermally-altered lower oceanic crust in the Madeira plume source. Consequently, K isotopes provide direct evidence that ocean island magma sources can contain both upper and lower recycled oceanic crust. This study provides important constraints on the cause of the temporal changes in geochemical composition of ocean island basalts, the origin of mantle heterogeneity and the recycling of K through subduction zones and the deep mantle.
马德拉地幔羽流被认为包含一整套回收的大洋岩石圈。然而，目前还无法确定马德拉岩浆源中是否同时存在下洋壳和橄榄岩岩石圈地幔。本研究报告了马德拉群岛熔岩的钾（K）和氧同位素数据，数据显示δ41K（-0.50 ± 0.06‰至-0.31 ± 0.01‰）与锶-钕-铅-铪同位素组成相关，证实了回收地壳物质的存在。从马德拉早期盾构期熔岩（-0.50±0.06‰至-0.40±0.05‰）到随后的后蚀变期熔岩（-0.34±0.04‰至-0.31±0.01‰），δ41K的增加与地幔源通过熔融萃取使回收的上洋壳（转化为斜长岩或辉长岩）随着年龄的降低而逐渐枯竭是一致的。然而，啮蚀后熔岩需要一个比贫化橄榄岩岩石圈地幔δ41K值更高的来源。建模表明，在高温蚀变的下洋壳脱水过程中，保留了最初的重 K 同位素特征，这与后断裂熔岩的高δ41K 值来自马德拉羽流源中的水热蚀变的下洋壳是一致的。因此，K 同位素提供了直接证据，证明大洋岛屿岩浆源可能同时包含上层和下层再循环大洋地壳。这项研究对大洋岛屿玄武岩地球化学组成的时间变化原因、地幔异质性的起源以及钾通过俯冲带和深地幔的循环提供了重要的制约因素。
{"title":"Potassium isotope evidence for subducted upper and lower oceanic crust in ocean island basalt sources","authors":"Haiyang Liu , Ying-Yu Xue , Jörg Geldmacher , Kaj Hoernle , Uwe Wiechert , Shichao An , Hai-Ou Gu , He Sun , Fanfan Tian , Xiaoqiang Li , Kun Wang , Hongli Zhu , Wei-Dong Sun","doi":"10.1016/j.epsl.2024.119015","DOIUrl":"10.1016/j.epsl.2024.119015","url":null,"abstract":"<div><p>The Madeira mantle plume is proposed to contain a complete package of recycled oceanic lithosphere. It has not been possible, however, to establish if both lower oceanic crust and peridotitic lithospheric mantle are present within the Madeira magma source. This study reports potassium (K) and oxygen isotope data of lavas from the Madeira Archipelago, which show that δ<sup>41</sup>K (-0.50 ± 0.06‰ to -0.31 ± 0.01‰) correlates with Sr-Nd-Pb-Hf isotopic compositions, confirming the incorporation of recycled crustal material. The increase in δ<sup>41</sup>K from Madeira's early shield stage lavas (-0.50 ± 0.06‰ to -0.40 ± 0.05‰) to the subsequent post-erosional stage lavas (-0.34 ± 0.04‰ to -0.31 ± 0.01‰) is consistent with the mantle source becoming progressively depleted in recycled upper oceanic crust (converted to eclogite or pyroxenite) through melt extraction with decreasing age. The post-erosional lavas, however, require a source with higher δ<sup>41</sup>K values than in depleted peridotitic lithospheric mantle. Modeling demonstrates that during dehydration of high-temperature altered lower oceanic crust, the initial heavy K isotopic signature is preserved, consistent with the high δ<sup>41</sup>K values of the post-erosional lavas being derived from hydrothermally-altered lower oceanic crust in the Madeira plume source. Consequently, K isotopes provide direct evidence that ocean island magma sources can contain both upper and lower recycled oceanic crust. This study provides important constraints on the cause of the temporal changes in geochemical composition of ocean island basalts, the origin of mantle heterogeneity and the recycling of K through subduction zones and the deep mantle.</p></div>","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":"646 ","pages":"Article 119015"},"PeriodicalIF":4.8,"publicationDate":"2024-09-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142272573","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}
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