Journal of the Geological Society最新文献

{"title":"Mineralogical and spectroscopic studies of rock-forming blue quartz phenocrysts from the metarhyolites of the Rio dos Remédios Group (Bahia, Brazil)","authors":"Danielle Cruz da Silva, Pedro L. Guzzo, Lauro Cézar Montefalco de Lira Santos, Gláucia Queiroga, Mahyra Tedeschi","doi":"10.1144/jgs2024-176","DOIUrl":"https://doi.org/10.1144/jgs2024-176","url":null,"abstract":"Blue quartz phenocrysts are encountered in felsic rocks and their metamorphosed equivalents. Despite their occurrence, detailed investigations into their crystal chemistry and mineralogical properties remain limited. This study focuses on a multiscale characterization of blue quartz phenocrysts hosted in metarhyolites from the Rio dos Remédios Group (Paramirim Aulacogen), one of the notable occurrences of blue quartz in Brazil. The mineralogy of the host rock was analysed using optical petrography, bi-polished plates and powder X-ray diffraction. Advanced techniques, including electron probe microanalysis (EPMA), infrared (IR) spectroscopy, and scanning and transmission electron microscopies, were employed to examine trace elements, OH-related defects and inclusions in quartz grains. In addition, electron paramagnetic resonance (EPR) was used to investigate coarse and fine powders of blue and colourless quartz phenocrysts. The study provides detailed insights into the crystal chemistry and microscopic properties of Rio dos Remédios quartz phenocrysts, highlighting Fe- and Ti-rich inclusions exsolved into the quartz matrix as the main distinction between blue and colourless regions. OH-related defects, grain size, and aspect ratio distributions were similar between the two varieties. These findings contribute to a better understanding of the mineralogical and chemical factors influencing the properties of blue quartz phenocrysts.","PeriodicalId":17320,"journal":{"name":"Journal of the Geological Society","volume":"183 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-07-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147901203","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Fluid inclusion and stable isotope fingerprints of the Paraná emerald deposit, Borborema Province, northeastern Brazil: implications for a tectonic–magmatic origin","authors":"José Ferreira de Araújo Neto, Ingrid de Souza Hoyer, Valmir da Silva Souza, Elder Yokoyama, Lauro Cézar Montefalco de Lira Santos","doi":"10.1144/jgs2025-004","DOIUrl":"https://doi.org/10.1144/jgs2025-004","url":null,"abstract":"Emerald from the Paraná deposit, in northeastern Brazil, is found in metasomatic phlogopite schists formed after fluid interactions between Be-bearing granitic pegmatites and Cr-rich mafic rocks within the Portalegre shear zone. This study combines fluid inclusion petrography, microthermometry, X-ray microtomography and stable isotope analyses to fingerprint the Paraná emerald deposit, providing critical insights into its formation within a tectonic–magmatic environment. Fluid inclusion analysis revealed two distinct fluid inclusion assemblages, with evidence of boiling processes triggered by tectonic stress. The distribution of fluid and phlogopite inclusions evidenced by X-ray microtomography indicate the presence of three stages of crystal growth, highly influenced by regional metamorphism and deformation. On the other hand, stable isotope data ( <mml:math xmlns:mml=\"http://www.w3.org/1998/Math/MathML\" id=\"IM1\" overflow=\"scroll\"> <mml:mi>δ</mml:mi> </mml:math> 18 O: +6.9 to +7.1‰; <mml:math xmlns:mml=\"http://www.w3.org/1998/Math/MathML\" id=\"IM2\" overflow=\"scroll\"> <mml:mi>δ</mml:mi> </mml:math> D: −76 to −93‰) are consistent with a magmatic origin for the hydrothermal fluids. These findings contribute to the understanding of emerald formation in the Borborema Province and to the discussion of the role of tectonic structures in emerald genesis, with the Portalegre shear zone interpreted as the main conduit for Be-rich pegmatite melts and fluids that led to the formation of the Paraná emerald during the final stage of the Brasiliano orogeny ( c. 528–524 Ma).","PeriodicalId":17320,"journal":{"name":"Journal of the Geological Society","volume":"182 5","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-05-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147918908","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Paleozoic subduction of the Palaeo-Asian Ocean plate: constraints from Ordovician–Carboniferous volcano-sedimentary rocks in the northern Beishan orogenic collage, NW China","authors":"Qingxiang Du, Sainan Wu, Jinrui Han, Xiaoli Shen, Yong Zhang","doi":"10.1144/jgs2023-153","DOIUrl":"https://doi.org/10.1144/jgs2023-153","url":null,"abstract":"The subduction history of the Hongshishan Ocean within the Beishan orogenic collage is crucial to our understanding of the evolutionary mechanisms of the Palaeo-Asian Ocean. We describe the petrography, age and geochemistry of an Ordovician–Carboniferous volcano-sedimentary succession that provides a record of the subduction history of the Hongshishan Ocean. We obtained early Ordovician zircon U–Pb ages (482 ± 6 and 472 ± 2 Ma) from the Xianshuihu Formation. The youngest weighted mean detrital zircon age from the Yuanbaoshan Formation is 421.0 ± 8.8 Ma. Most detrital zircons have prominent age peaks at 900–840 and 543–462 Ma, suggesting a main source from the southern Mongolian microcontinent. Volcanic rocks from the Baishan Formation yielded weighted mean ages of 300.3–299.3 Ma. During the Ordovician–Devonian, some volcanic arcs formed on the northern side of the Hongshishan–Baiheshan–Erlegen Ula ophiolitic belt, indicating that the Hongshishan Ocean had a northward subduction polarity. During the Carboniferous, continental arcs were well developed on both sides of the Hongshishan–Baiheshan–Erlegen Ula belt, suggesting bidirectional subduction. An archipelago of multiple arcs of the Hongshishan Ocean resembles that of the West Pacific Ocean. The change in subduction polarity can be attributed to the characteristics of multi-oceanic accretion.","PeriodicalId":17320,"journal":{"name":"Journal of the Geological Society","volume":"181 6","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-08-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147915627","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Magnetic fabric of OPS mélanges: a tool for unravelling protracted histories of oceanic plates from sea-floor spreading to tectonic emplacement into accretionary wedges","authors":"Lucia Pellerey, J. Žák, F. Tomek, Andrea Festa","doi":"10.1144/jgs2023-141","DOIUrl":"https://doi.org/10.1144/jgs2023-141","url":null,"abstract":"Multiple magnetic fabrics, referred to as F1–F5, were revealed through the anisotropy of magnetic susceptibility (AMS) in an Ocean Plate Stratigraphy (OPS) mélange of the Neoproterozoic–Cambrian Blovice accretionary complex, Bohemian Massif. The fabrics postdate the mélange formation and rotation of basalt blocks within the matrix and are interpreted in terms of a complex structural history of the mélange. Excluding local fabrics, the F1 fabric formed earlier along the mélange belt, recording shortening of the accretionary wedge front, whereas the higher-grade F4 fabric pervasively overprinted both blocks and matrix in the SW part of the belt, recording shearing and vertical shortening at deeper structural levels closer to a megathrust surface. The preservation of angular relationships between the F1 and F4 fabrics across different parts of mélange suggests that blocks were only strained and not rotated during deformation, exemplifying the notion that the OPS mélanges may be a product of deformation at very shallow levels. Finally, the F1–F5 fabrics may be viewed as snapshots in a protracted evolution of OPS mélanges, where earlier fabrics in basalt blocks may record the travel path of an oceanic plate from mid-ocean ridge towards the trench, before being overprinted in the accretionary wedge.\u0000 \u0000 Thematic collection:\u0000 This article is part of the Ophiolites, melanges and blueschists collection available at:\u0000 https://www.lyellcollection.org/topic/collections/ophiolites-melanges-and-blueschists\u0000 \u0000 \u0000 Supplementary material:\u0000 https://doi.org/10.6084/m9.figshare.c.7008173\u0000","PeriodicalId":17320,"journal":{"name":"Journal of the Geological Society","volume":"28 12","pages":""},"PeriodicalIF":2.7,"publicationDate":"2024-01-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139445122","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Interaction of surface processes and crustal flow in the Eastern Himalayan Syntaxis","authors":"Guangwei Li, Haibin Yang, M. Sandiford, Barry P. Kohn, Zhiqin Xu, Hanwen Dong, Dongxu Cai","doi":"10.1144/jgs2023-041","DOIUrl":"https://doi.org/10.1144/jgs2023-041","url":null,"abstract":"The syntaxes at the eastern and western ends of the Himalaya located at the Tsangpo and Indus gorge regions provide examples of the interplay between tectonics and erosion. A previous borehole study along the Yarlung River in the Eastern Himalayan Syntaxis (EHS) reveals a ∼1 km thick sedimentary wedge upstream of the Tsangpo gorge with a >2.5 Ma depositional age. However, mechanism of formation of this sedimentary wedge remains under debate. Here, we combine low-temperature thermochronology data and thermo-mechanical modelling to discuss how a sedimentary wedge formed at the highly eroded EHS. Our low-temperature thermochronology results show late Miocene fast cooling episodes focused at the Gyaca and Tsangpo gorges, which are interpreted to be related to coeval rifting at the former and rapid erosion and hot-crust upwelling at the latter. Constrained by the geological and geophysical observations, we apply thermo-mechanical models to illustrate the mechanism of formation of the sedimentary wedge and present high relief of the EHS. The numerical geodynamic model shows that localised erosion triggers middle ‘crust extrusion’ and regional topographic adjustment at the EHS.\u0000 \u0000 Thematic collection:\u0000 This article is part of the Mesozoic and Cenozoic tectonics, landscape and climate change collection available at:\u0000 https://www.lyellcollection.org/topic/collections/mesozoic-and-cenozoic-tectonics-landscape-and-climate-change\u0000 \u0000 \u0000 Supplementary material:\u0000 https://doi.org/10.6084/m9.figshare.c.7008098\u0000","PeriodicalId":17320,"journal":{"name":"Journal of the Geological Society","volume":"54 7","pages":""},"PeriodicalIF":2.7,"publicationDate":"2024-01-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139446024","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Coherent underplating of HP-LT blueschist packages and basement during Hellenic subduction recorded by zircon U-Pb data, Pelion, Greece","authors":"Emily R. Hinshaw, D. Stockli, Kostantinos Soukis","doi":"10.1144/jgs2023-147","DOIUrl":"https://doi.org/10.1144/jgs2023-147","url":null,"abstract":"Studies of high pressure-low temperature (HP-LT) metamorphic complexes are critical for advancing our understanding of subduction processes, such as underplating, metamorphism, and exhumation. Detailed new U-Pb zircon data of blueschist-facies metasedimentary units at Pelion indicate two distinct, stratigraphically upright, and coherent structural slices, with (1) the South Pelion slice consisting of strata with Permian-Late Cretaceous zircon maximum depositional ages (MDAs) and (2) the North Pelion slice comprising strata with Triassic-Late Cretaceous zircon MDAs. Both slices have Late Cretaceous strata at the top of the section with cosmopolitan detrital zircon (DZ) signatures. Ages from zircon U-Pb rim overgrowths correlate with existing constraints from subduction-metamorphism during the Paleocene-Eocene, with a possible second stage recorded during Basal underplating in the Late Eocene-Oligocene. DZ provenance data and multi-dimensional scaling (MDS) comparisons demonstrate a tectono-metamorphic linkage between the Pelion rocks and the Cycladic Blueschist Unit (CBU), and between the southern Pelion Basement and the Cycladic Basement (CB). Protolith deposition for Pelion blueschist-facies rocks occurred during Permo-Carboniferous intra-arc extension and Adria-Pindos rifting. Our results show that the Pelion blueschist-facies rocks, representing lateral equivalents of the CBU, are comprised of two separate, coherent upper-crustal slivers that were underplated and metamorphosed during Hellenic subduction beneath the Pelagonian margin.\u0000 \u0000 Thematic collection:\u0000 This article is part of the Ophiolites, melanges and blueschists collection available at:\u0000 https://www.lyellcollection.org/topic/collections/ophiolites-melanges-and-blueschists\u0000 \u0000 \u0000 Supplementary material:\u0000 https://doi.org/10.6084/m9.figshare.c.7008123\u0000","PeriodicalId":17320,"journal":{"name":"Journal of the Geological Society","volume":"42 10","pages":""},"PeriodicalIF":2.7,"publicationDate":"2024-01-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139448088","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Offscraping and shallow ophiolite accretion in the Ligurian Accretionary Wedge (Tuscan Apennines): role of seafloor structural inheritance","authors":"G. Nirta, F. Remitti, Edoardo Barbero, A. Festa","doi":"10.1144/jgs2023-189","DOIUrl":"https://doi.org/10.1144/jgs2023-189","url":null,"abstract":"The Morello Tectonic Unit in the Tuscan Apennines (Italy) represents the result of tectono-sedimentary deformation, occurring in the frontal part of the non-metamorphosed Ligurian Accretionary Wedge, which consists of ophiolitic slices imbricated with a sedimentary succession containing ophiolite-bearing sedimentary mélanges. Geological mapping, structural and stratigraphic observations, allow us to document that (i) the ophiolite-bearing sedimentary mélanges formed by gravitational reworking of material sourced from intrabasinal structural highs facing the oceanic basin environment from Jurassic to lower Eocene, before the middle Eocene accretion stage, and (ii) the ophiolitic tectonic slices represent the scraping off at shallow structural levels of part of these crustal oceanic highs sequence. The final internal architecture of the shallow frontal portion of the Ligurian Accretionary Wedge does not differ from those observed in metamorphosed orogenic belts and exhumed accretionary complexes throughout the world (e.g., blueschist and eclogite units of Western Alps). This suggests that to the classical model of subduction and metamorphism followed by accretion and mélange formation (i.e., underplating), a model in which frontal accretion and ophiolite mélange formation at a shallow level are followed by underthrusting and subduction can be added, providing additional constraints to a better reconstruction of orogenic belts and accretionary complexes evolution.\u0000 \u0000 Thematic collection:\u0000 This article is part of the Ophiolites, melanges and blueschists collection available at:\u0000 https://www.lyellcollection.org/topic/collections/ophiolites-melanges-and-blueschists\u0000","PeriodicalId":17320,"journal":{"name":"Journal of the Geological Society","volume":"7 9","pages":""},"PeriodicalIF":2.7,"publicationDate":"2024-01-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139382806","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Early Jurassic and Late Cretaceous plagiogranites in Nain-Baft ophiolitic mélange zone in Iran: remnants of rift–drift and SSZ evolution of a Neotethyan seaway","authors":"N. Shirdashtzadeh, Y. Dilek, H. Furnes, E. Dantas","doi":"10.1144/jgs2023-181","DOIUrl":"https://doi.org/10.1144/jgs2023-181","url":null,"abstract":"We have investigated the geology, geochemistry, and geochronology of various plagiogranite intrusions that are spatially associated with ophiolitic subunits in a mélange terrain exposed within the Nain–Baft fault zone along the western boundary of the Central–East Iranian Microcontinent (CEIM). One group of plagiogranites is intrusive into foliated amphibolites, whereas the plagiogranites of the other group are intrusive into gabbros, dike swarms, and pillow lavas that are tectonically juxtaposed. U–Pb zircon dating of the first group of plagiogranites has revealed near concordant crystallization ages of 176.94±0.71, 179.84±0.92, and 190.40±2.1 Ma, indicating the early Jurassic timing of their emplacement. U–Pb zircon dating of the second group of plagiogranites has revealed a weighted average age of 92.34±0.38 Ma, indicating that they were emplaced in the early Late Cretaceous. The Early Jurassic plagiogranites are low–K, sub–alkaline rocks with negative Eu anomalies, low Ti and high La and Ce contents. They display elevated LILE/HFSE ratios. They were part of a magmatic system which facilitated the earliest rift–drift stages of a Neotethyan seaway development, and their magmas were produced by fractional crystallization of a mafic melt associated with asthenospheric upwelling beneath a rift system. The Late Cretaceous plagiogranites are low–K, sub–alkaline rocks with negative Eu anomalies, high Y and low Ta contents. They show LREE depletion relative to flat HREE patterns, and high Ba/Th ratios. Magmas of these plagiogranites were the products of partial melting of amphibolites in the subducting oceanic lithosphere in the same Neotethyan seaway. Thus, we posit that plagiogranite rocks in suture zones can be excellent trackers of geochemical, geochronological, and magmatic evolution of various types of oceanic crust through rift–drift, seafloor spreading, and subduction initiation stages within the same ocean basins in the past.\u0000 \u0000 Thematic collection:\u0000 This article is part of the Ophiolites, melanges and blueschists collection available at:\u0000 https://www.lyellcollection.org/topic/collections/ophiolites-melanges-and-blueschists\u0000","PeriodicalId":17320,"journal":{"name":"Journal of the Geological Society","volume":"59 39","pages":""},"PeriodicalIF":2.7,"publicationDate":"2024-01-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139381878","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Mississippian olistostromes of Iberia revisited: Tectonic drivers of synorogenic carbonate platform/reef destruction","authors":"Í. F. Dias da Silva, Manuel Francisco Pereira, E. G. Clavijo, José Brandão Silva","doi":"10.1144/jgs2023-187","DOIUrl":"https://doi.org/10.1144/jgs2023-187","url":null,"abstract":"A review of the synorogenic basins formed on the Gondwana side of the Variscan orogen of Iberia is presented, highlighting the widespread ocurrence of calciturbiditic formations and olistostromes containing reef-limestone olistoliths in Iberia's Variscan basins. Using key-examples from the Variscan orogen for comparison (Azrou-Khenifra and Rhenohercynian basins), the significance of these olistostromes and flyschoid deposits is discussed. Our tectonic models of the Variscan belt in Iberia propose possible drivers of synorogenic carbonate platform/reef destruction responsible for the origin of calciturbidites and olistostromes. One model proposes the formation of an orogenic plateau by lateral flow of partially molten orogenic roots in the context of Laurussia-Gondwana convergence, following the destruction of the Rheic Ocean and Gondwana (lower) plate slab retreat. An alternative model invokes subduction of Paleotethys oceanic lithosphere beneath the Gondwana (upper) plate. Both emphasize the Mississippian occurrence of a significant thermal anomaly beneath Gondwana that favored strong lithosphere thinning, creating ideal conditions for synorogenic carbonate platform/reef destruction, and for the formation of calciturbidite deposits and olistostromes in Iberia. Variscan paleotopography would look alike in both situations. Thus, distinguishing these models is not straightforward, with differences in the kinematics of the regional tectonic transport in the superstructure of Mississippian gneiss domes.\u0000 \u0000 Thematic collection:\u0000 This article is part of the Ophiolites, melanges and blueschists collection available at:\u0000 https://www.lyellcollection.org/topic/collections/ophiolites-melanges-and-blueschists\u0000","PeriodicalId":17320,"journal":{"name":"Journal of the Geological Society","volume":"20 5","pages":""},"PeriodicalIF":2.7,"publicationDate":"2024-01-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139383904","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Dolomite formation during penecontemporaneous subaerial diagenesis: Evidence from modern dolomite crusts forming in lagoon Brejo do Espinho, Brazil","authors":"Meng Ning, Yao Wang, Judith A. McKenzie, C. Vasconcelos, Chenqing Li, Anjiang Shen, Feng Liang, Bing Shen","doi":"10.1144/jgs2023-159","DOIUrl":"https://doi.org/10.1144/jgs2023-159","url":null,"abstract":"\u0000 Early lithification of carbonate mud during the subaerial exposure stage, under semiarid conditions, has been proposed to facilitate dolomite formation. However, how the biogeochemical processes during subaerial diagenesis promote dolomite formation remains unclear. Here, we employ a multiproxy approach to investigate the process of dolomite formation by analyzing modern dolomite crusts forming in lagoon Brejo do Espinho (LBE). Petrological analysis reveals that the crusts comprise coexisting high-Mg calcite (HMC) and dolomite. Low Fe and Mn concentrations indicate the formation of dolomite under oxic conditions, while a higher Sr concentration in well-lithified crust suggests primary bacterial-induced dolomite precipitation. The Mg isotopic composition of the crusts exhibits a lighter value compared to that of modern sabkha dolomite, suggesting different dolomitization processes and Mg sources. More negative\u0000 \u0000 \u0000 δ\u0000 \u0000 \u0000 ¹³C values of the crusts than unlithified carbonate mud in LBE, indicating the incorporation of\u0000 13\u0000 C depleted organic carbon. The biogeochemical processes related to decaying organic matter during subaerial diagenesis generate partially oxidized organic matter that promotes Mg\u0000 2+\u0000 dehydration and enhances the dissolution of primary HMC, ultimately triggering the transition of HMC to dolomite or/and direct dolomite precipitation. The ancient \"dolomite factory\" operated through cyclic deposition of carbonate sediments and penecontemporaneous subaerial diagenesis.\u0000 \u0000 \u0000 Thematic collection:\u0000 This article is part of the Towards unravelling the ‘Dolomite Problem’: new approaches and novel perspectives collection available at:\u0000 https://www.lyellcollection.org/topic/collections/towards-unravelling-the-dolomite-problem\u0000","PeriodicalId":17320,"journal":{"name":"Journal of the Geological Society","volume":"113 4","pages":""},"PeriodicalIF":2.7,"publicationDate":"2024-01-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139383440","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}