Geological Society of America Bulletin最新文献

{"title":"Evolution and uranium mineralization of the northern Ordos Basin revealed by detrital zircons of the Jurassic strata","authors":"Yuan Liu, Hang Liu, Yang-Quan Jiao, Jun‐Hong Zhao","doi":"10.1130/b37488.1","DOIUrl":"https://doi.org/10.1130/b37488.1","url":null,"abstract":"Stable sedimentary basins with complex evolutionary histories generally develop various epigenetic resources, such as sandstone-type uranium deposits. However, the genetic linkage between basin evolution and subsequent uranium mineralization remains unclear. Detrital zircon is a robust mineral, and its U-Pb ages and Lu-Hf isotopes are essential for tracing the evolution of sedimentary basins. The Ordos Basin is the largest intracontinental basin and uranium deposit region in the North China Craton. It consists of Cambrian to Ordovician marine deposits and Carboniferous to Jurassic terrestrial successions, and the origins of the terrigenous clastic sequences are dominantly influenced by the neighboring orogenic belts. This study presents new whole-rock elemental data, detrital zircon U-Pb ages, and Lu-Hf isotopes for the sandstones from the Jurassic Zhiluo Formation of the northern Ordos Basin. With data from the Paleozoic sedimentary rocks of the basin and the southern Central Asian Orogenic Belt, this study aimed to determine sediment provenances, the evolution of the northern Ordos Basin, and the potential implications for uranium mineralization. Detrital zircons from the Zhiluo Formation are generally rounded and preserve magmatic zoning structures. Their ages display four populations, 330−245 Ma, 470−350 Ma, 2100−1650 Ma, and 2750−2200 Ma, which are consistent with the tectono-thermal events of the Central Asian Orogenic Belt and the Yinshan Belt to the north, and the Alxa Block to the northwest. Both their detrital zircon ages and εHf(t) values are similar to those of the underlying sedimentary rocks. In addition, the formation has recycled carbonaceous debris, diverse clastic fragments, and Triassic fossils, and its sandstones show low index of compositional variability values (0.79−0.97) and high SiO2/Al2O3 (5.33−7.25) and Th/Sc (0.71−1.97) ratios. These lines of evidence suggest that the detritus of the Zhiluo Formation was partially derived from the underlying sedimentary strata. It should be noted that the Paleozoic to Mesozoic strata of the northern Ordos Basin also have detrital zircon age patterns and εHf(t) values similar to those of the southern Central Asian Orogenic Belt, and the secular evolution of the Ordos Basin is therefore considered to have been controlled by subduction of the Paleo-Asian Ocean and collision between the Central Asian Orogenic Belt and the North China Craton, as well as the post-collisional crustal extension that ensued. The carbonaceous debris in the Zhiluo Formation provided a reductive environment for the subsequent crystallization of reducing minerals and uranium mineralization.","PeriodicalId":55104,"journal":{"name":"Geological Society of America Bulletin","volume":null,"pages":null},"PeriodicalIF":3.9,"publicationDate":"2024-08-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141921795","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":"Late Eocene sodic calc-alkaline lamprophyre in Gangdese batholith, southern Tibet: Implications for mantle metasomatism by carbonatitic melt","authors":"Guangxu Li, Lingsen Zeng, Li-E Gao, Lilong Yan, Linghao Zhao, Yi-hong Tian","doi":"10.1130/b37566.1","DOIUrl":"https://doi.org/10.1130/b37566.1","url":null,"abstract":"Similar to oceanic lithosphere, the progressive and continuous subduction of continental lithosphere could lead to early dehydration and subsequent melting of the subducting slab. Melting subducted carbonate materials could release carbonatitic melts and trigger melting of the overlying lithospheric mantle and the formation of different types of alkaline and calc-alkaline rocks. In this paper, we present a study on a suite of mafic dikes of sodic calc-alkaline lamprophyre (CAL) composition in the eastern Gangdese batholith, southern Tibet. These dikes, emplaced ca. 36.9 ± 0.3 Ma, are characterized by (1) high CaO and Na2O but low K2O content and hence exceptionally high Na2O/K2O ratios (>2.3 up to 68.1); (2) negative anomalies of Nb-Ta-Zr-Hf-Ti, and (3) strong enrichment in light rare earth elements and large ion lithophile elements. Significantly low Rb/Sr (<0.06) and Dy/Yb (<2.5), coupled with high Ba/Rb (>31 up to 1447), suggest their derivation by low-degree partial melting of amphibole-bearing peridotite within the garnet-facies lherzolite field. Compared to those in depleted mantle, they are also characterized by high initial 87Sr/86Sr (0.7074−0.7078), 207Pb/204Pb(t) (15.74−15.75), and 208Pb/204Pb(t) (39.39−39.41), but relatively low εNd(t) values (−1.8 to +2.4) and 206Pb/204Pb(t) (18.81−18.82) and zircon εHf(t) values (+2.7 to +7.3). In terms of Sr-Nd isotope systematics, they are more enriched than those in Mesozoic−Cenozoic magmatic rocks, but more depleted than younger (after 30 Ma) potassic−ultrapotassic rocks within the Gangdese batholith, which requires a different mantle source. These lamprophyres contain abundant carbonate minerals with a linear correlation between CaO and CO2, which suggests primary carbonate phases and a mantle source region rich in carbonate materials. We propose that sodic CAL was generated by the partial melting of an enriched lithospheric mantle metasomatized by carbonatitic melts derived from the subducted Indian continental crust. The emplacement of lamprophyres is associated with E-W extension induced by local post-collisional delamination of thickened lower continental crust (∼75 km) after the collision between India and Asia.","PeriodicalId":55104,"journal":{"name":"Geological Society of America Bulletin","volume":null,"pages":null},"PeriodicalIF":3.9,"publicationDate":"2024-08-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141929429","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":"Quaternary volcanism in southeastern Tibetan Plateau: A record of Neo-Tethyan oceanic slab stagnant in the mantle transition zone","authors":"Huan Kang, Yongwei Zhao, Xiaoran Zhang, Liyun Zhang, Huiping Zhang, Haibo Zou","doi":"10.1130/b37546.1","DOIUrl":"https://doi.org/10.1130/b37546.1","url":null,"abstract":"Tibetan lateral mantle flow could help to decipher the material movement mechanisms within global plate convergence zones. However, the front edge of this mantle flow is unclear. We conducted petrological, geochronological, mineralogical, geochemical, and Sr-Nd-Pb isotopic investigations of Quaternary intracontinental alkali basalts from southwestern Yunnan (south of 27°N) to determine the petrogenesis of the Quaternary alkali basalts in the southeastern Tibetan Plateau in particular and to trace the recent Tibetan lateral mantle flow. Alkali basalts in the region are mainly basanite and trachybasalt that erupted during the Pleistocene epoch. They possess highly incompatible elemental and radiogenic Sr-Nd-Pb isotopic compositions similar to those of the oceanic-island basalts, consistent with melts derived from asthenospheric mantle with a low degree of partial melting. Calculated magma water contents of regional alkali basalts range from 1.32 ± 0.48 wt% to 2.23 ± 0.18 wt%, which corresponds to water content of their mantle source comprising 269 ppm to 3591 ppm, which is significantly higher than that of the normal upper mantle (i.e., 50−250 ppm). Quantitative trace-element modeling and dramatic variations in oceanic crust−sensitive indicators such as Eu/Eu*, Sr/Sr*, Ce/Pb, (Nb/Th)N-PM, and (Ta/U)N-PM indicate variable contributions of upper and lower oceanic crust to magma sources. Systematic examinations of petrological, geochemical, and geophysical evidence reveal that the temporary small-volume Quaternary volcanism in the southeastern Tibetan Plateau is unrelated to Tibetan southeastward mantle flow but is primarily attributed to stagnant Neo-Tethyan slab in the mantle transition zone. Our study offers a distinctive perspective for reconciling the geochemical features of intracontinental alkali basalts and highlights the potential role of alkali basalts in tracing the front edge of recent Tibetan lateral mantle flow.","PeriodicalId":55104,"journal":{"name":"Geological Society of America Bulletin","volume":null,"pages":null},"PeriodicalIF":3.9,"publicationDate":"2024-08-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141927864","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":"Salinity reconstruction in Proterozoic depositional systems","authors":"Zhanhong Liu, T. Algeo, Jochen J. Brocks, Lennart M. van Maldegem, G. Gilleaudeau, Linda C. Kah, Meng Cheng, Wenchao Yu","doi":"10.1130/b37489.1","DOIUrl":"https://doi.org/10.1130/b37489.1","url":null,"abstract":"Although elemental proxies (i.e., boron/gallium [B/Ga], strontium/barium [Sr/Ba], and sulfur/total organic carbon [S/TOC]) have been extensively used to evaluate paleo-watermass salinities in Phanerozoic shales and marls, their application to Precambrian-age formations has been limited. Here, we evaluate these proxies for five depositional systems ranging in age from late Paleoproterozoic to late Neoproterozoic. Our analysis shows that the range of B/Ga ratios encountered (∼2−9) matches that seen in Phanerozoic deposits and is consistent with a spectrum of salinity conditions ranging from freshwater (B/Ga < 3) to brackish (B/Ga 3−6) to marine (B/Ga 6−12). Furthermore, all B/Ga-based salinity assignments are consistent with existing paleosalinity inferences, including fully marine conditions for the ca. 650 Ma Areyonga-Aralka and ca. 1640 Ma Barney Creek formations in Australia, mixed brackish-marine conditions for the ca. 650 Ma Datangpo Formation in China and the ca. 1100 Ma El Mreiti Group shales in Mauritania, and low-brackish conditions for the ca. 1080 Ma Nonesuch Formation in North America. Our salinity assessment for the Nonesuch Formation is particularly significant in view of extended debate regarding the lacustrine versus marine character of this unit. The influences of diagenesis and clay-mineral assemblages on B/Ga-based salinity interpretations are generally minor to insignificant. The Sr/Ba proxy yielded systematically lower salinity estimates than the B/Ga proxy based on salinity facies thresholds established from modern aqueous systems, a pattern that we interpret to reflect reduced Sr concentrations in Proterozoic seawater. The S content and S/TOC ratios of all units are sufficiently high as to preclude freshwater conditions (incidentally indicating that Proterozoic seawater sulfate concentrations were higher than sometimes inferred). These findings demonstrate that elemental salinity proxies, especially B/Ga, are broadly applicable to shale formations of Proterozoic age, providing an important new tool for paleoenvironmental analysis that has the potential to reshape our understanding of life-environment co-evolution in deep-time systems.","PeriodicalId":55104,"journal":{"name":"Geological Society of America Bulletin","volume":null,"pages":null},"PeriodicalIF":3.9,"publicationDate":"2024-07-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141800069","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":"Evidence for large Holocene earthquakes along the Yangsan fault in the SE Korean Peninsula revealed in three-dimensional paleoseismic trenches","authors":"S. Naik, Thomas K. Rockwell, Su-Ho Jeong, Young-Seog Kim, H. Shin, Jeong-Heon Choi, S. Ha, Moon Son","doi":"10.1130/b37275.1","DOIUrl":"https://doi.org/10.1130/b37275.1","url":null,"abstract":"The Yangsan fault is the most prominent NNE-SSW−striking active right-lateral strike-slip fault crossing the Korean Peninsula, with a continuous trace of ∼200 km. It can likely generate large earthquakes; however, the paleoseismic information on slip per event, slip rate, and timing of past ruptures along this fault remains sparse. To explore these parameters for the Yangsan fault, we excavated trenches across the central segment of the fault, which showed evidence for at least five surface-rupturing earthquakes preserved in Quaternary fluvial deposits. The timing of these earthquakes is discussed based on luminescence and radiocarbon ages. A close examination of three-dimensional trench exposures revealed that the most recent event(s) occurred during or slightly after the third century CE (one-event interpretation) or sixth to eighth century CE (two-event interpretation), and it was associated with 4.5 m to 5.3 m of lateral displacement of a paleochannel. The observed lateral displacement indicates that large earthquakes with a magnitude of around Mw 7 have taken place in the recent past, which is the first-ever direct evidence of large-magnitude earthquakes along the Yangsan fault. The penultimate event occurred after 17 ± 1 ka, whereas an earlier late Quaternary event occurred in the late Pleistocene, suggesting a recurrence interval in the range of 10,000 yr, and a consequent slip rate on the order of 0.5 mm/yr. The oldest observed ruptures are preserved below an erosional unconformity that probably dates back to the last interglacial period, based on infrared stimulated luminescence ages. An unknown number of ruptures may have occurred between the unconformity and subsequent sedimentation during the latest Pleistocene to Holocene period. Historical earthquake records indicate clustered behavior of moderate and large earthquakes along the Yangsan fault. Past faulting events and implied recurrence intervals constrain the long-term faulting behavior along the Yangsan fault and will contribute to a better seismic hazard assessment in the southeastern part of the Korean Peninsula.","PeriodicalId":55104,"journal":{"name":"Geological Society of America Bulletin","volume":null,"pages":null},"PeriodicalIF":3.9,"publicationDate":"2024-07-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141803481","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":"Eocene tearing and fragmentation of Indian lithosphere beneath the Woka rift, southern Tibet","authors":"Lin Gong, Qiang Wang, A. C. Kerr, Huayong Chen, Jingjing Fan, Zilong Wang, Dongjing Xu, Qiji Yang","doi":"10.1130/b37577.1","DOIUrl":"https://doi.org/10.1130/b37577.1","url":null,"abstract":"When and how the syncontractional N-S−trending rifts formed in the Himalayan-Tibetan Plateau are crucial, yet unsolved issues that could help establish the interplay between geodynamic evolution and uplift of the plateau. Recent geophysical observations indicate that although Indian lithosphere tearing is the most likely trigger for rift formation, the timing of this tearing remains uncertain. To address this issue, we studied the Woka rift, which represents a typical N-S−trending rift in southern Tibet. Our results show that granitoids from the hanging wall and footwall of the Woka rift have significantly different magma crystallization temperatures (770−860 °C versus 650−750 °C) and crustal thickness (∼40 km versus ∼60 km) during the Eocene. These differences were most likely linked to tearing of the Indian lithosphere. The integration of crustal thickness trends and bedrock emplacement depth from the Eocene to the Oligocene suggest that the hanging wall exhumed at a faster rate than the footwall. From this information, it is clear that the Woka rift did not undergo E-W extension during this period. Integrating data from geophysics, thermochronology, mantle-derived, N-S−trending dikes, and adakitic rocks, we propose that Indian lithospheric tearing and fragmentation during the Eocene caused weakening of the Tibetan middle-lower crust rather than directly triggering surface extension of the Woka rift. This study has significant implications for the deep lithospheric processes and surface responses in the Himalayan-Tibetan Plateau.","PeriodicalId":55104,"journal":{"name":"Geological Society of America Bulletin","volume":null,"pages":null},"PeriodicalIF":3.9,"publicationDate":"2024-07-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141808869","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":"Age, sedimentology, and deformational history of the Mesozoic Franciscan accretionary complex, Angel Island, California, USA","authors":"Meghomita Das, Owen Anfinson, Christie Rowe, Nicolas Schroeder","doi":"10.1130/b37239.1","DOIUrl":"https://doi.org/10.1130/b37239.1","url":null,"abstract":"The Franciscan Complex represents the forearc accretionary wedge that formed during late Mesozoic−Cenozoic subduction in California, USA, and preserves detailed records of long-lived subduction and exhumation of high-pressure, low-temperature rocks. As one of the world’s largest exposed subduction complexes, it records the evolution of subduction dynamics that correspond to the tectonic development of the western USA.\u0000 Lithotectonic units within the Franciscan Complex represent different stages, mechanisms, and depths of accretion in the subduction history. Previous authors have proposed subdivisions for the Franciscan Complex, but as the metasedimentary units are very similar over large spatial and temporal scales, they have been difficult to map except on the broadest scales. This restricts the potential for researchers to characterize past tectonic events and subduction/exhumation mechanisms.\u0000 Angel Island in the San Francisco Bay has previously been mapped as an undivided blueschist-facies metasedimentary unit thrust over lower-grade metasediments along the Quarry Point thrust, but we find that the Angel Island units include lithologic and metamorphic diversity spanning nearly the entire range of variability for the Franciscan Complex. We present new mapping, lithologic descriptions, and detrital zircon U-Pb geochronology to propose a new lithostratigraphy for Angel Island consisting of seven structurally juxtaposed units ranging from sub-metamorphic to low blueschist. The structurally highest and structurally lowest units are sub-blueschist grade, and the center of the fault-bounded stack consists of blueschist-grade metasediments separated by a thin sliver of sodic-amphibole metabasalt. The blueschist units and structurally higher sub-blueschist−grade units have maximum depositional ages of ca. 108−110 Ma, which is consistent with similar grade units from across the Bay Area, and they match well with respect to lithology and metamorphic grade. The structurally lowest units below the Quarry Point thrust have similar provenance but younger maximum depositional ages of ca. 97 Ma. These units have been suggested by previous authors to be affiliated with either Alcatraz or Marin Headlands rocks, which have similar depositional ages but show much more diversity in detrital zircon age spectra, which makes their association debatable.\u0000 These results offer the first high-resolution detrital zircon U-Pb geochronologic dataset from the Franciscan Complex that allows definition of the diversity of age and provenance within a previously defined regional unit, which should be considered in future work attempting regional correlations with regional sample distribution.","PeriodicalId":55104,"journal":{"name":"Geological Society of America Bulletin","volume":null,"pages":null},"PeriodicalIF":3.9,"publicationDate":"2024-07-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141822109","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":"Mud cohesion governs unvegetated meander migration rates and deposit architecture","authors":"M. Douglas, Kimberly Litwin Miller, Michael P. Lamb","doi":"10.1130/b37315.1","DOIUrl":"https://doi.org/10.1130/b37315.1","url":null,"abstract":"Vegetation is thought to be a main source of riverbank cohesion, enabling meandering and a deposit architecture characterized by sandy channel belts isolated in mudstone. However, early Earth and Mars had meandering rivers without vegetation, implying that other sources of bank strength can allow meandering with potentially different deposit characteristics. Here we studied the Amargosa River in Death Valley, California, USA, as a modern analog of meandering rivers without vegetation. We monitored flow and erosion at two bends and used radiocarbon dating of strandlines to quantify flood frequency. We also sampled cutbank mud and constrained an erosion theory using flume experiments. Cutbank erosion occurred for floods with >2 yr recurrence intervals, and 18 cm occurred for an ∼6 yr reoccurrence, bankfull event. Mud set the rate of meander migration: salt crusts rapidly and completely dissolved during floods, vegetation was absent, and mud entrainment theory matched observed erosion rates. Flood-frequency analysis showed that most bank erosion occurs at flows below bankfull, challenging the threshold channel hypothesis. We used meander migration rates to constrain the time scale of channel-belt formation and compared it to the time scale of avulsion. These calculations, combined with floodplain facies mapping and core sedimentology, indicated a likely deposit architecture of sandy point bar accretion sets intermixed with muddy overbank facies. This deposit architecture is characteristic of vegetated meandering rivers, but due to muddy banks, occurred for the Amargosa River in the absence of plants.","PeriodicalId":55104,"journal":{"name":"Geological Society of America Bulletin","volume":null,"pages":null},"PeriodicalIF":3.9,"publicationDate":"2024-07-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141822042","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":"Oceanic anoxic event 3 in Arctic Canada—Arc volcanism and ocean fertilization drove anoxia","authors":"S. Grasby, James L Crowley, M. Mohr, Jeanne B. Percival, O. Ardakani, Jennifer M. Galloway, M. Bringué, I. R. Smith, Wanju Yuan","doi":"10.1130/b37632.1","DOIUrl":"https://doi.org/10.1130/b37632.1","url":null,"abstract":"The global extent of the Late Cretaceous oceanic anoxic event 3 (OAE 3) remains uncertain. It is not considered to have extended into the Boreal Realm. To test this, we examined Late Cretaceous organic- and metal-rich black mudstones of the Smoking Hills Formation in Arctic Canada. New high-precision U-Pb zircon ages indicate that deposition of the Smoking Hills Formation (88.535−78.230 Ma) was temporally coincident with OAE 3, indicating a much broader global expression of this event than previously thought. OAE 3 was likely manifest throughout the proto−Arctic Ocean (now Arctic Canada). Abundant bentonite layers and cryptotephra within the Smoking Hills Formation have rare earth element (REE) patterns that are consistent with ashfall derived from Cretaceous arc volcanism. Anomalously high organic matter content in the Smoking Hills Formation, as compared to underlying and overlying units, suggests that ocean fertilization led to enhanced productivity and metal drawdown. A peak in arc volcanism may have been a key driver of the OAE 3 event. We also explored the potential use of cadmium as a geochemical marker of volcanism and show that high volcanogenic metal loading could affect the use of Cd and other proxies for marine productivity (e.g., Zn, Cu).","PeriodicalId":55104,"journal":{"name":"Geological Society of America Bulletin","volume":null,"pages":null},"PeriodicalIF":3.9,"publicationDate":"2024-07-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141820655","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":"3-D model reveals thermal decomposition as a potential driver of seismicity in the Apennines, Italy","authors":"Thanushika Gunatilake, Stephen A. Miller","doi":"10.1130/b37234.1","DOIUrl":"https://doi.org/10.1130/b37234.1","url":null,"abstract":"Earthquakes in the Central Apennines of Italy generate extensive aftershock sequences, with high-pressure CO2 often implicated as an important contributor to seismogenesis. Fluid pressure diffusion (through porous media) of mantle-derived high-pressure CO2 trapped in reservoirs is assumed to drive these sequences, yet seismic evidence of diffusion fronts remains elusive. We show here that co-seismic thermal decomposition also imposes numerous additional and isolated high fluid pressure sources that diffuse to drive the aftershock sequences. Numerical simulations mimic the generation of thermally decomposed fluids and reproduce the 2009 L’Aquila Mw 6.3 and the 2016 Amatrice-Visso-Norcia Mw 6.5 earthquake sequences. We identify hydraulic barriers and a minimum magnitude (Mw > 4) for thermal decomposition, which generate significant aftershock sequences in carbonates. The implications of thermal decomposition in seismogenesis are far-reaching and can be applied to any system, such as within subduction zones.","PeriodicalId":55104,"journal":{"name":"Geological Society of America Bulletin","volume":null,"pages":null},"PeriodicalIF":3.9,"publicationDate":"2024-07-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141826713","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}