Geochemistry Geophysics Geosystems最新文献

{"title":"Rift-Related Low-Pressure–High-Temperature Granulite Facies Metamorphism Generates Widespread Peraluminous Crustal Melts: Evidence From the Early Jurassic Mexican Crust","authors":"Anthony Ramírez-Salazar,&nbsp;Mattia Parolari,&nbsp;Arturo Gómez-Tuena,&nbsp;Fernando Ortega-Gutiérrez,&nbsp;Mariano Elías-Herrera","doi":"10.1029/2024GC012019","DOIUrl":"https://doi.org/10.1029/2024GC012019","url":null,"abstract":"<p>High heat fluxes occurring in rift settings are expected to generate partially melted low-pressure–high-temperature granulites (LP–HTG). Therefore, studying these rocks can offer valuable insights into crustal reworking during extension. However, our interpretations are limited by the rarity of LP–HTG in the metamorphic record. To better assess the genesis of partially melted LP–HTG, it is relevant to identify their protolith and associated melt as well as to characterize their P-T evolution. We study the Tejupilco area in Mexico to present the case of the Pepechuca metapelitic xenoliths and the Tizapa metagranite, the latter belonging to the Nazas Igneous Province (NIP). This site serves as an excellent location to outline the partial melting history of the eastern and southern regions of the Mexican crust during the Jurassic. Geochemical and geochronological data, combined with thermodynamic modeling, show that the mid- to upper-crustal protoliths of the Pepechuca xenoliths—a metamorphosed portion of Triassic turbidite sequences—experienced anomalously high T/P (&gt;1700°C/GPa) regional prograde metamorphism and hydrate-breakdown partial melting during the Early Jurassic (182.2 ± 2.4 Ma). A combination of isotopic, geochronological, and modeling data demonstrates that the Tizapa metagranite originated from the melting of rocks akin to the Pepechuca xenoliths. We also show that the LP–HTG metamorphism occurred in a rift setting during the breakup of Western Pangea. Hence, our results demonstrate that rifting is a viable mechanism for crustal reworking during LP–HTG metamorphism and for the generation of peraluminous felsic igneous rocks, such as those found in the anatectic Jurassic NIP.</p>","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":"26 5","pages":""},"PeriodicalIF":2.9,"publicationDate":"2025-05-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024GC012019","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143901041","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Heterogeneous Mantle Metasomatism Controlled by Continental Subduction: Evidence From Post-Collisional Mafic Rocks in the North Qaidam Orogen","authors":"Xiangyu Gao,&nbsp;Shengyao Yu,&nbsp;Yu Qi,&nbsp;Lintao Wang,&nbsp;Chuanzhi Li,&nbsp;Xiaocong Jiang,&nbsp;Xingzhou Jiang,&nbsp;Yang Yu","doi":"10.1029/2025GC012179","DOIUrl":"https://doi.org/10.1029/2025GC012179","url":null,"abstract":"<p>Post-collisional mafic rocks not only record geodynamic processes at the end of the orogenic cycle but also retain various clues regarding preceding interactions between subducted slabs and mantle wedges. However, the latter and related indicators have often been overlooked; in particular, how the continental crust interacts with the mantle in subduction zones and modifies its nature remains ambiguous. This study of post-collisional mafic rocks in the North Qaidam orogen provides new insights into sophisticated crust–mantle interactions via variable continental subduction. These post-collisional mafic rocks are consistent with the geochemical nature of arc lava and originated from partial melting of the antecedent metasomatic mantle. Although they possess relatively uniform whole-rock Sr–Nd isotopes, the mafic rocks from the ultrahigh-pressure metamorphic terranes present more enriched zircon Hf isotopes and remarkable signals of melt-driven mantle metasomatism than the other rocks within the non-ultrahigh-pressure metamorphic zone. This is attributed to spatially variable continental subduction and the consequent differentiated crust–mantle interactions. Trace element modeling also reveals that a greater proportion of continental component-derived metasomatic melts are needed to form mafic rocks in ultrahigh-pressure metamorphic terranes. The whole-rock magnesium isotopes are between −0.15‰ and −0.38‰, which are negatively correlated with (⁸⁷Sr/⁸⁶Sr)_<i>i</i> and positively correlated with <i>ɛ</i>_Nd(<i>t</i>) and <i>ɛ</i>_Hf(<i>t</i>). These findings indicate that these mafic rocks exhibit lighter magnesium isotopes when their mantle source is metasomatized by more continental component-derived melts enriched with radiogenic isotopes. The geochemical distinctions of the post-collisional mafic rocks verify the contributions from continental subduction to heterogeneous mantle metasomatism and magmatic diversity.</p>","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":"26 5","pages":""},"PeriodicalIF":2.9,"publicationDate":"2025-04-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2025GC012179","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143888882","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Timing of Dike and Sill Emplacement in the Inner Aureole of the Alta Stock, Utah Determined by Zircon and Monazite Petrochronology","authors":"C. J. Beno,&nbsp;M. A. Stearns,&nbsp;J. R. Bowman,&nbsp;J. M. Bartley,&nbsp;D. P. Fernandez,&nbsp;A. R. C. Kylander-Clark","doi":"10.1029/2024GC011946","DOIUrl":"https://doi.org/10.1029/2024GC011946","url":null,"abstract":"<p>Detailed geochronology from two compositionally distinct generations of dikes and sills intruded into the Alta metamorphic aureole, north-central Utah, complement previous geochronologic studies from the Alta stock, providing information on the timing of magmatism and the nature of emplacement. Uranium/thorium-lead dates and chemistry were measured in zircon and monazite from these intrusions and associated reaction selvages in hornfels by split-stream laser ablation techniques. Concordant zircon U-Pb dates (<i>n</i> = 532) define a dispersed population of dates that range from ∼38 to 32 Ma. Monazite Th-Pb dates (<i>n</i> = 888) from granodioritic compositions range from ∼40 to 32 Ma. Evaluation of ²⁰⁸Pb/²³²Th and ²⁰⁷Pb/²⁰⁶Pb-corrected dates with respect to common Pb, U and Th/U values allows rigorous evaluation of the effects of excess ²⁰⁶Pb in these young monazites, yielding concordant ²⁰⁸Pb/²³²Th and ²⁰⁷Pb/²⁰⁶Pb-corrected dates in monazites from the granodiorite, consistent with zircon dates from the same thin sections. Leucogranite sills and dikes, which cross-cut the older granodiorite, have younger monazite dates from ∼33 to 28 Ma. Elevated heavy rare earth element concentrations and trends of larger negative Eu anomalies in the youngest monazites suggest crystallization from an evolved melt. Integration of these new geochronology results and field relationships with prior results from the Alta stock indicate the granodiorite represents the oldest material emplaced in the Alta system. Leucogranite aplite/pegmatite dikes and sills in the inner Alta aureole were emplaced during the final stage of Alta stock construction by injection of evolved water-rich magmas.</p>","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":"26 5","pages":""},"PeriodicalIF":2.9,"publicationDate":"2025-04-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024GC011946","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143889029","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Micro-Scale Characterization of Marine Sediment Structures: The Potential and Challenges of X-Ray μCT Imaging","authors":"R. Gatter,&nbsp;G. Bartzke,&nbsp;B. N. Madhusudhan,&nbsp;S. Ahmed,&nbsp;M. Clare,&nbsp;M. Vardy,&nbsp;K. Huhn","doi":"10.1029/2024GC011840","DOIUrl":"https://doi.org/10.1029/2024GC011840","url":null,"abstract":"<p>Natural marine sediments are heterogeneous with respect to sediment-physical properties, and have a wide range in composition and structures. For many years, sediment-physical characterization has relied primarily on laboratory experiments. However, the investigation of small-(grain-)scale sedimentary structures, which appear to control many sediment (re-)depositional and emplacement mechanisms, requires new analytical methods. Here, we test high-resolution X-ray synchrotron micro-tomography (μCT) to qualitatively and quantitatively investigate structural differences, in 3D, between two lithological end-member types of marine sediments: a coarse-grained, sandy sediment and a fine-grained, silty-clay sediment. Our results show clear compositional and structural differences between the two end-members, as well as between samples taken from the same lithological unit. These differences can be attributed partly to different sediment types, that is, coarse-versus fine-grained sediments, but also reveal a dependency on the sedimentation regime. We find that pore space distribution is highly spatially variable, even down to a sub-millimeter scale. Such high variability in porosity would be missed by standard geotechnical experiments, which only provide information averaged over far larger sediment samples. The identification of small-(grain-)scale changes in pore space, however, directly impacts sediment properties such as permeability, which in turn is crucial for the understanding of geological processes such as fluid flow and storage capacity of sediments and assessing hazards such as the preconditioning of submerged slopes to collapse. Our results therefore demonstrate the potential of μCT to investigate the internal structure of natural sediments, obtaining information that is not resolved or lost in data acquired through other analytical methods.</p>","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":"26 4","pages":""},"PeriodicalIF":2.9,"publicationDate":"2025-04-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024GC011840","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143879779","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Enigmatic Deep-Water Seafloor Depressions East of Tortue Island, Northern Haiti Margin","authors":"A. Oliveira de Sá,&nbsp;S. Lafuerza,&nbsp;S. Leroy,&nbsp;E. d’Acremont,&nbsp;E. Ducassou,&nbsp;R. Deschamps,&nbsp;K. Fauquembergue,&nbsp;S. Zaragosi,&nbsp;J. L. Granja-Bruña,&nbsp;R. Momplaisir,&nbsp;D. Boisson","doi":"10.1029/2024GC012089","DOIUrl":"https://doi.org/10.1029/2024GC012089","url":null,"abstract":"<p>A widespread area of seafloor depressions - circular, arcuate to elongated-shaped - has been found along the Northern Haitian coast, at water depths between 600 and 2,000 m. Characterized by wavelengths spanning several hundred meters and heights of tens of meters, these depressions are linked with a series of narrow ridges boasting varied morphologies. Our analysis integrating multichannel seismic reflection, high-resolution bathymetry data, and sedimentological and geochemical evaluations of surface sediment cores indicates that present-day seafloor morphology results from the interaction of slope bottom currents with the seafloor. The analyzed sediment cores exhibit hemipelagites, silty and sandy contourites, fine-grained turbidites and reworked sand layers, implying sedimentation in a contourite drift system. This is further corroborated by seismic reflection data depicting wavy reflectors and aggradational stacking features typical of contourite drifts. Seafloor depressions are likely erosional features formed on the top of a contourite drift formed by the interaction of bottom currents with an irregular seafloor morphology. The seafloor equilibrium was initially disturbed by mass-wasting events. Subsequently, the quasi-steady flow of along-slope bottom currents influenced sedimentary distribution and controlled the morphology of the seafloor depressions-constant re-shaping through erosion on their flanks. The resulting rough seafloor could have facilitated the destabilization of bottom currents and the development of erosive eddies responsible for the current morphology of the seafloor depressions. This study highlights the interplay between sedimentary processes (accumulation and compaction) and bottom currents, showing how their combined effects influence slope sedimentation and seafloor geomorphology, forming unique erosional features.</p>","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":"26 4","pages":""},"PeriodicalIF":2.9,"publicationDate":"2025-04-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024GC012089","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143884155","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Cenozoic Structurally Controlled Hydrothermal Activity Revealed by Apatite Thermochronology in the Convoy Range (Southern Victoria Land, Antarctica)","authors":"M. Fioraso,&nbsp;V. Olivetti,&nbsp;F. Balsamo,&nbsp;F. Rossetti,&nbsp;M. Zattin,&nbsp;G. Cornamusini","doi":"10.1029/2024GC012005","DOIUrl":"https://doi.org/10.1029/2024GC012005","url":null,"abstract":"<p>The Transantarctic Mountains form the longest and highest extensional mountain range on Earth, marking the boundary between the Antarctic craton and the Mesozoic-Cenozoic rifted Ross Sea lithosphere. During the Cenozoic, deep offshore troughs, such as the Terror Rift, developed at the front of the Transantarctic Mountains in response to transtensional dextral kinematics that overprinted an older phase of orthogonal rifting. On land, few direct age constraints of Cenozoic faulting exist, and evidence of fault activity is often inferred from fission track age dating. In this study, we focused on the Convoy Range block in southern Victoria Land, a region with limited field surveys and thermochronological data. We present the results of multiscale structural analysis, geothermometry, and apatite fission-track thermochronology aimed at reconstructing the fault architecture and timing of deformation. The fault pattern is dominated mainly by nearly N-S striking normal faults, with a subordinate system of right-lateral transtensional faults. Brittle deformation is accompanied by diffuse propylitic alteration and carbonatization, providing evidence of hydrothermal fluid-rock interaction in a mesothermal environment (∼175–325°C). Fission track ages of fault rocks as young as ∼23 Ma are interpreted as local thermal resetting along faults, potentially constraining the age of deformation. These results document a case of structurally controlled hydrothermal fluid flow coeval to Cenozoic transtensional reactivation in Victoria Land, with important implications for the onset of Cenozoic volcanism in the region.</p>","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":"26 4","pages":""},"PeriodicalIF":2.9,"publicationDate":"2025-04-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024GC012005","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143884154","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Cascading Earthquake Swarms in the Northern Taupō Volcanic Zone, New Zealand","authors":"S. Aber,&nbsp;C. J. Ebinger,&nbsp;A. C. Gase,&nbsp;C. Kalugana,&nbsp;F. Illsley-Kemp,&nbsp;I. Hamling,&nbsp;S. Sabir,&nbsp;M. K. Savage,&nbsp;J. Eccles,&nbsp;S. Hreinsdottir,&nbsp;J. Ristau,&nbsp;J. James-Le","doi":"10.1029/2024GC012079","DOIUrl":"https://doi.org/10.1029/2024GC012079","url":null,"abstract":"<p>The spatiotemporal characteristics of infrequent back-arc rifting events and their relationships to volcanic unrest as well as other transient processes within the subduction system are not well known. We report 10 spatio-temporal swarms of earthquakes that occurred along ∼175 km of the northern and central Taupō Volcanic Zone (TVZ) March–September 2019. The swarms lack clear mainshock-aftershock distributions, suggesting involvement of pressurized fluids. The most energetic swarms occurred beneath the southwestern flank of Whakaari/White Island volcano (WI) and were accompanied by elevated SO₂ emissions and ∼8 mm southwest displacement of the edifice. Focal mechanisms of the WI swarms suggest horizontal dilation in the direction of tectonic extension achieved by slip along networks of closely spaced, NE-striking normal faults linked by oblique-slip to strike-slip faults. Given the small GNSS displacements and upward-migrating swarms, we favor the interpretation that magmatic volatiles were released along faults in response to changes in crustal stress. Based on the punctuated, cascading nature of swarms along the northern TVZ, we hypothesize that faults and magmatic systems are fluid-rich, experiencing aseismic creep, and critically stressed, raising the possibility that small changes in crustal stress from slow slip along the Hikurangi subduction zone caused a reduction in the minimum horizontal stress. This change occurred along the entire northern TVZ over ∼5 months, potentially contributing to widespread volcanic unrest. The probable release of magmatic fluids from shallow magma bodies in the vicinity of WI between May and June argues against a causal relation to the 9 December 2019 WI eruption.</p>","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":"26 4","pages":""},"PeriodicalIF":2.9,"publicationDate":"2025-04-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024GC012079","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143875658","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Seismic Structure of the Mid to Upper Crust at the Santorini-Kolumbo Magma System From Joint Earthquake and Active Source Vp-Vs Tomography","authors":"R. S. Hufstetler,&nbsp;E. E. E. Hooft,&nbsp;D. R. Toomey,&nbsp;B. P. VanderBeek,&nbsp;C. B. Papazachos,&nbsp;N. Chatzis","doi":"10.1029/2024GC012022","DOIUrl":"https://doi.org/10.1029/2024GC012022","url":null,"abstract":"<p>Santorini volcano has a history of caldera-forming eruptions, most recently in the Late Bronze Age, at 3.4 kya, and remains volcanically active. The Kolumbo submarine volcano, located 7 km to the northeast of Santorini, erupted in 1650 AD in a deadly phreatomagmatic eruption. Ongoing seismic activity and active hydrothermal venting at Kolumbo indicate this volcano is a significant hazard to the Santorini region. The magma source for Santorini and the Kolumbo edifice are considered separate in the shallow crust, though their deeper magma distribution is not yet constrained. In this study, we improve constraints on the mid-crustal magma system of Santorini caldera and the nearby Kolumbo volcano using local earthquake tomography. We use 1515 P-wave and 1435 S-wave arrival times from 63 local earthquakes with magnitudes from 0.5 to 3.0 that occurred between 5 and 15 km depth together with an existing data set of active source Pg arrivals. The upper crustal magma system beneath Santorini is imaged to at least 6 km depth, and to 12 km depth beneath Kolumbo. We recover a high P-wave velocity layer (∼6–8 km) under the Kolumbo magma reservoir that we infer is a rheologically strong seismogenic layer. We also recover a mid-crustal magma body below 8 km depth located to the NE of Santorini and Kolumbo.</p>","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":"26 4","pages":""},"PeriodicalIF":2.9,"publicationDate":"2025-04-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024GC012022","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143875634","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Pore Fluid Origins, Circulation, and Links With Methane Hydrate on the South-Central Chilean Margin","authors":"Vincent J. Clementi,&nbsp;Wei-Li Hong,&nbsp;Yair Rosenthal,&nbsp;Samantha C. Bova,&nbsp;Laurel B. Childress","doi":"10.1029/2025GC012195","DOIUrl":"https://doi.org/10.1029/2025GC012195","url":null,"abstract":"<p>The chemical composition of marine sedimentary pore waters, notably freshening signals inferred from decreases in dissolved Cl⁻, have demonstrated a link between methane hydrate accumulation and the circulation of fluids and gases in convergent margin systems. However, the south-central Chilean Margin (32–46°S) lacks geochemical evidence for this relationship. In 2019, D/V <i>JOIDES Resolution</i> Expedition 379T drilled two sites (J1005 and J1006) near legacy site ODP 1233 (41°S) and recovered 120 m sediment cores from a seafloor venting structure. The sites are less than 10 km apart but exhibit differences in pore water chemistry and methane hydrate occurrence. The extent of Cl⁻ decrease is a function of distance from the venting structure, with the greatest freshening (and only recovery of methane hydrate) occurring at the closest site. Methane fluxes follow the same pattern, suggesting a common influence. Increasing oxygen and decreasing hydrogen isotopes point to mineral bound water originating ∼2.5 km below the seafloor as the primary source of pore water freshening. In contrast, marine silicate weathering coupled to methanogenesis, authigenic carbonate formation, and the alteration of oceanic crust regulate Sr systematics. These spatial heterogeneities indicate that fluid migration is attributable to regional overpressures in the accretionary complex and flows along narrow fault structures. We suggest that the focused migration of deep, gas-charged fluids serves as a model for regional methane hydrate accumulation, reconciling model estimates and field observations. Collectively, our results highlight an important link between regional hydrogeology, diagenetic processes, and methane hydrate formation on the south-central Chilean Margin.</p>","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":"26 4","pages":""},"PeriodicalIF":2.9,"publicationDate":"2025-04-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2025GC012195","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143875637","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Quantitative Microstructural Analysis of Exhumed Epidote-Amphibolites and Plate Interface Rheology in Warm Subduction Zones","authors":"Laurens H. Kleijbeuker,&nbsp;Hamed Amiri,&nbsp;Maartje F. Hamers,&nbsp;Alissa J. Kotowski","doi":"10.1029/2024GC011886","DOIUrl":"https://doi.org/10.1029/2024GC011886","url":null,"abstract":"<p>Epidote-amphibolites form along the plate interface during subduction infancy and are stable in warm, mature subduction zones that generate slow earthquakes. Epidote-amphibolite rheology therefore likely influences plate-scale processes during plate boundary formation and grain-scale processes that give rise to slip transients. We present optical and electron microscopy of naturally deformed epidote-amphibolites from beneath the Oman ophiolite (∼7–10 kbar, 400–550°C) to characterize their deformation behavior. Epidote-amphibolites are fine-grained, strongly foliated and lineated, and exhibit polyphase fabrics in which amphiboles (grain size ∼10–50 μm) and epidotes (grain size ∼5–20 μm) are strain-accommodating phases. Two-point correlation connectivity analysis demonstrates that amphiboles are well-connected regardless of phase proportions/distributions. Chemical analysis and electron backscatter diffraction reveals amphibole syn-kinematic metamorphic zonations, strong crystallographic and shape - preferred orientations (CPOs and SPOs), subgrain geometries indicating (hk0)[001] slip, and high average Grain Orientation Spreads (GOS; ∼6°), interpreted as coupled dissolution-precipitation creep (DPC) and dislocation glide. Epidotes record weak CPOs, low intragranular misorientations, moderate SPOs, and low GOS (∼0–2°), interpreted as deformation by DPC. Depending on phase distributions, epidote-amphibolite rheology can be approximated as interconnected weak layers of amphibole dissolution creep or a composite rheology of plasticity and fluid-assisted/diffusion-accommodated creep. We estimate stress from quartz piezometry (∼30–45 MPa) and strain rates from flow laws and geologic data (6 · 10⁻¹¹ to 10⁻¹³ s⁻¹), and calculate equivalent viscosities of &lt;10¹⁸ Pa-s. On tectonic timescales, such low viscosities are consistent with epidote-amphibolites serving as strain localizing agents during subduction infancy. On seismic timescales, coupled dislocation glide and diffusion creep exemplify a strain-hardening deformation state that could culminate in creep transients.</p>","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":"26 4","pages":""},"PeriodicalIF":2.9,"publicationDate":"2025-04-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024GC011886","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143875636","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}