We use seismic reflection data acquired by a winter-over expedition on drifting sea ice in the central Arctic Ocean to explore a possible spatial and temporal magmatic relation between the sub-bottom geology of part of the deep Arctic Ocean and the Mesozoic volcanic rocks found on the islands and the bordering continental shelf of Franz Josef Land and Svalbard? The new data set from the North American segment (85 o – 90 o N) of the Lomonosov Ridge, central Arctic Ocean documents several Mesozoic volcanic pulses over a distance of ˞600 km along the ridge. This volcanism borders a domain of high magnetic field intensity over the adjacent Alpha Ridge in the deep basin where the magnetic source rocks and recent seismic reflection data indicate extensive Mesozoic magmatism. We suggest the Mesozoic volcanism on the Lomonosov Ridge in its paleo-position at the former continental margin north of Franz Josef Land and Svalbard spatially link the Mesozoic magmatic pulses of the continental High Arctic Large Igneous Province (HALIP) of polar Europe to volcanism on the adjacent Alpha Ridge in the deep Arctic Ocean. Increased input of heat to the upper crust on the Lomonosov Ridge enhanced maturation of hydrocarbon source rocks as manifested by the presence of gas/fluid escape pipes restricted to the area of volcanism.
{"title":"The High Arctic Large Igneous Province: first seismic-stratigraphic evidence for multiple Mesozoic volcanic pulses on the Lomonosov Ridge, central Arctic Ocean","authors":"Y. Kristoffersen, E. Harris Nilsen, J. Hall","doi":"10.1144/jgs2022-153","DOIUrl":"https://doi.org/10.1144/jgs2022-153","url":null,"abstract":"\u0000 We use seismic reflection data acquired by a winter-over expedition on drifting sea ice in the central Arctic Ocean to explore a possible spatial and temporal magmatic relation between the sub-bottom geology of part of the deep Arctic Ocean and the Mesozoic volcanic rocks found on the islands and the bordering continental shelf of Franz Josef Land and Svalbard? The new data set from the North American segment (85\u0000 o\u0000 – 90\u0000 o\u0000 N) of the Lomonosov Ridge, central Arctic Ocean documents several Mesozoic volcanic pulses over a distance of ˞600 km along the ridge. This volcanism borders a domain of high magnetic field intensity over the adjacent Alpha Ridge in the deep basin where the magnetic source rocks and recent seismic reflection data indicate extensive Mesozoic magmatism. We suggest the Mesozoic volcanism on the Lomonosov Ridge in its paleo-position at the former continental margin north of Franz Josef Land and Svalbard spatially link the Mesozoic magmatic pulses of the continental High Arctic Large Igneous Province (HALIP) of polar Europe to volcanism on the adjacent Alpha Ridge in the deep Arctic Ocean. Increased input of heat to the upper crust on the Lomonosov Ridge enhanced maturation of hydrocarbon source rocks as manifested by the presence of gas/fluid escape pipes restricted to the area of volcanism.\u0000","PeriodicalId":17320,"journal":{"name":"Journal of the Geological Society","volume":" ","pages":""},"PeriodicalIF":2.7,"publicationDate":"2023-05-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46337889","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}
C. Cruz, P. Nogueira, Jaime Máximo, F. Noronha, H. Sant’Ovaia
The Santa Eulália Plutonic Complex is formed by two main granites, G0 and G1 granites. Within the G0 granite there are metasedimentary carbonate and pelitic rocks (roof pendants) and elongated masses of mafic-intermediate rocks (M-group). The host rocks comprise a diversified sequence of igneous, metasedimentary and metamorphic rocks. The study area is constrained by Variscan structures formed in a transpressional/transtensional sinistral tectonic regime – the Tomar-Badajoz-Córdoba sinistral shear zone, and is cut by the Alter do Chão and Assumar faults. The geological complexity of the area makes hard to determine the emplacement mechanism of the pluton. Herein, a model is proposed for the ascent and emplacement of the pluton; this model can also be applied to similar post-collision Variscan granites. The gravity anomalies suggest that the pluton is slightly asymmetric and extends to the south-southeast beneath the host rocks, and its main root has a thicknesses of more than 8 km in its deepest areas. Complementarly, the available radiometric data for an extended area embracing several regional plutons suggest a W-E magmatic alignment. The Variscan structures likely constituted efficient crustal discontinuities enabling the generation and ascent of magma. Our model involves a W-E magmatic axis for magma spreading along extensional fractures (T-fractures) related to the Tomar-Badajoz-Córdoba shear zone. The opening movement along these fractures, created divergent forces that allowed the ascent and emplacement of the plutonic rocks. The importance of these fractures is well represented by the outcrops of the porphyritic biotite granites (Ervedal, Fronteira and G1 granites).
Santa Eulália Plutonic杂岩由两种主要花岗岩G0和G1形成。在G0花岗岩内，存在变质沉积碳酸盐岩和泥质岩（屋顶悬垂物）以及细长的镁铁质中间岩（M组）。寄主岩石由火成岩、变质沉积岩和变质岩组成。该研究区域受到华力西构造的制约，华力西结构形成于挤压/张拉左旋构造体系——托马尔-巴达约兹-科尔多瓦左旋剪切带，并被Alter do Chão和Assumar断层切割。该地区地质复杂，很难确定深成岩体的侵位机制。在此，提出了深成岩体上升和侵位的模型；该模型也可应用于类似的碰撞后华力西花岗岩。重力异常表明，该深成岩体略微不对称，在寄主岩石下方向东南偏南延伸，其主根在最深区域的厚度超过8公里。补充的是，包含几个区域性深成岩体的扩展区域的可用辐射数据表明了W-E岩浆排列。华力西构造可能构成了有效的地壳不连续性，使岩浆能够产生和上升。我们的模型涉及一个W-E岩浆轴，用于沿着与托马尔-巴达霍斯-科尔多瓦剪切带有关的伸展裂缝（T裂缝）传播的岩浆。沿着这些裂缝的张开运动产生了不同的力，使深成岩体得以上升和就位。斑状黑云母花岗岩（Ervedal、Fronteira和G1花岗岩）的露头充分体现了这些断裂的重要性。
{"title":"New insights for an emplacement model for the Santa Eulália Plutonic Complex (SW of Iberian Peninsula)","authors":"C. Cruz, P. Nogueira, Jaime Máximo, F. Noronha, H. Sant’Ovaia","doi":"10.1144/jgs2022-131","DOIUrl":"https://doi.org/10.1144/jgs2022-131","url":null,"abstract":"The Santa Eulália Plutonic Complex is formed by two main granites, G0 and G1 granites. Within the G0 granite there are metasedimentary carbonate and pelitic rocks (roof pendants) and elongated masses of mafic-intermediate rocks (M-group). The host rocks comprise a diversified sequence of igneous, metasedimentary and metamorphic rocks. The study area is constrained by Variscan structures formed in a transpressional/transtensional sinistral tectonic regime – the Tomar-Badajoz-Córdoba sinistral shear zone, and is cut by the Alter do Chão and Assumar faults. The geological complexity of the area makes hard to determine the emplacement mechanism of the pluton. Herein, a model is proposed for the ascent and emplacement of the pluton; this model can also be applied to similar post-collision Variscan granites. The gravity anomalies suggest that the pluton is slightly asymmetric and extends to the south-southeast beneath the host rocks, and its main root has a thicknesses of more than 8 km in its deepest areas. Complementarly, the available radiometric data for an extended area embracing several regional plutons suggest a W-E magmatic alignment. The Variscan structures likely constituted efficient crustal discontinuities enabling the generation and ascent of magma. Our model involves a W-E magmatic axis for magma spreading along extensional fractures (T-fractures) related to the Tomar-Badajoz-Córdoba shear zone. The opening movement along these fractures, created divergent forces that allowed the ascent and emplacement of the plutonic rocks. The importance of these fractures is well represented by the outcrops of the porphyritic biotite granites (Ervedal, Fronteira and G1 granites).","PeriodicalId":17320,"journal":{"name":"Journal of the Geological Society","volume":" ","pages":""},"PeriodicalIF":2.7,"publicationDate":"2023-05-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48214522","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}
F. Perez‐Torrado, J. Carracedo, H. Guillou, A. Rodríguez-González, J. Fernández-Turiel
Fuerteventura and Lanzarote (Eastern Canary Islands), form the oldest emerged part of the archipelago. Geologically, they can be considered a single edifice, constituting a continuous volcanic ridge extending 250 km from SW to NE. This work completes the dating and the determination of the magnetic stratigraphy of the shields and the rejuvenated volcanism of Fuerteventura and Lanzarote, refining the volcanic stratigraphy and cartography. The new unspiked K-Ar ages and magnetostratigraphy of Fuerteventura and Lanzarote indicate that these islands developed patterns similar to those of the Central and Western Canary Islands, building adjacent and successively superimposed basaltic shield volcanoes during the Miocene, between 20.19 ± 0.30 and 6.30 ± 0.11 Ma. The overlay of post-Miocene rejuvenated volcanism hinders the extent and interrelationship of the shields. These materials constitute only a small fraction by volume but cover a large part of the islands. Despite this, it is confirmed that the disposition of the shields is opposite to the insular progression induced by the hot spot, suggesting the presence of some SW-NE propagation volcanic front or fracture to explain its direction of development. Supplementary material: https://doi.org/10.6084/m9.figshare.c.6641464
{"title":"Age, duration, and spatial distribution of ocean shields and rejuvenated volcanism: Fuerteventura and Lanzarote, Eastern Canaries","authors":"F. Perez‐Torrado, J. Carracedo, H. Guillou, A. Rodríguez-González, J. Fernández-Turiel","doi":"10.1144/jgs2022-112","DOIUrl":"https://doi.org/10.1144/jgs2022-112","url":null,"abstract":"Fuerteventura and Lanzarote (Eastern Canary Islands), form the oldest emerged part of the archipelago. Geologically, they can be considered a single edifice, constituting a continuous volcanic ridge extending 250 km from SW to NE. This work completes the dating and the determination of the magnetic stratigraphy of the shields and the rejuvenated volcanism of Fuerteventura and Lanzarote, refining the volcanic stratigraphy and cartography. The new unspiked K-Ar ages and magnetostratigraphy of Fuerteventura and Lanzarote indicate that these islands developed patterns similar to those of the Central and Western Canary Islands, building adjacent and successively superimposed basaltic shield volcanoes during the Miocene, between 20.19 ± 0.30 and 6.30 ± 0.11 Ma. The overlay of post-Miocene rejuvenated volcanism hinders the extent and interrelationship of the shields. These materials constitute only a small fraction by volume but cover a large part of the islands. Despite this, it is confirmed that the disposition of the shields is opposite to the insular progression induced by the hot spot, suggesting the presence of some SW-NE propagation volcanic front or fracture to explain its direction of development.\u0000 \u0000 Supplementary material:\u0000 https://doi.org/10.6084/m9.figshare.c.6641464\u0000","PeriodicalId":17320,"journal":{"name":"Journal of the Geological Society","volume":" ","pages":""},"PeriodicalIF":2.7,"publicationDate":"2023-05-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48320895","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}
Nuo Li, Bo Zhang, M. Danišík, Yan‐jing Chen, D. Selby, W. Xiao
The Central Asian Orogenic Belt (CAOB) represents a Late Paleozoic archipelago. Yet the crustal growth, reworking and exhumation of individual microcontinental massifs remain poorly constrained. Here, we utilize the Axi epithermal deposit to examine continental preservation and exhumation of CAOB in the Chinese Western Tianshan. Zircon U-Pb dating and geochemistry demonstrate that the andesitic host rock formed by incremental addition of magma in an Andean-type magmatic arc setting at 362, 354 and 342 Ma. Pyrite Re-Os data and textural evidence reveal two mineralization events at 355 and 332 Ma. Zircon (U-Th)/He data reveal temperatures of ∼180 °C until 317.8 ± 9.8 Ma, which is interpreted to record the timing of exhumation of the andesite and gold orebodies prior to their burial by Carboniferous aged sediments. Further sedimentary concealment continued until the Late Mesozoic, when the system was re-exhumed between 148.6 ± 8.6 and 120.0 ± 13 Ma at a rate of ∼9.8 m/Ma as shown by apatite (U-Th)/He data . Collectively, the geo-/thermochronology demonstrates that the Chinese Western Tianshan records the transition from compressional to extensional tectonism during the Late Paleozoic and the Late Mesozoic. The shallow epithermal mineralization was protected from erosion by post-mineralization deposition. Supplementary material: https://doi.org/10.6084/m9.figshare.c.6640014
{"title":"Formation - exhumation history of the Carboniferous Axi epithermal gold deposit in the Chinese Western Tianshan based on zircon U-Pb and pyrite Re - Os geochronology, and (U-Th)/He zircon - apatite thermochronometry","authors":"Nuo Li, Bo Zhang, M. Danišík, Yan‐jing Chen, D. Selby, W. Xiao","doi":"10.1144/jgs2021-150","DOIUrl":"https://doi.org/10.1144/jgs2021-150","url":null,"abstract":"The Central Asian Orogenic Belt (CAOB) represents a Late Paleozoic archipelago. Yet the crustal growth, reworking and exhumation of individual microcontinental massifs remain poorly constrained. Here, we utilize the Axi epithermal deposit to examine continental preservation and exhumation of CAOB in the Chinese Western Tianshan. Zircon U-Pb dating and geochemistry demonstrate that the andesitic host rock formed by incremental addition of magma in an Andean-type magmatic arc setting at 362, 354 and 342 Ma. Pyrite Re-Os data and textural evidence reveal two mineralization events at 355 and 332 Ma. Zircon (U-Th)/He data reveal temperatures of ∼180 °C until 317.8 ± 9.8 Ma, which is interpreted to record the timing of exhumation of the andesite and gold orebodies prior to their burial by Carboniferous aged sediments. Further sedimentary concealment continued until the Late Mesozoic, when the system was re-exhumed between 148.6 ± 8.6 and 120.0 ± 13 Ma at a rate of ∼9.8 m/Ma as shown by apatite (U-Th)/He data . Collectively, the geo-/thermochronology demonstrates that the Chinese Western Tianshan records the transition from compressional to extensional tectonism during the Late Paleozoic and the Late Mesozoic. The shallow epithermal mineralization was protected from erosion by post-mineralization deposition.\u0000 \u0000 Supplementary material:\u0000 https://doi.org/10.6084/m9.figshare.c.6640014","PeriodicalId":17320,"journal":{"name":"Journal of the Geological Society","volume":" ","pages":""},"PeriodicalIF":2.7,"publicationDate":"2023-05-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48944304","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}
T. Riley, A. Burton‐Johnson, K. Hogan, A. Carter, P. Leat
The Cenozoic development of the Scotia Sea and opening of Drake Passage led to the dispersal of crustal blocks of the North and South Scotia ridges that today have a strong influence on the pathway of the Antarctic circumpolar current. The pre-translation positions of the crustal fragments of the Scotia ridges are uncertain, with correlations to both the Antarctic and South American plates. We present direct geochronology ( 40 Ar/ 39 Ar) from Bruce and Jane banks of the South Scotia Ridge that yield Late Cretaceous – Paleogene ages indicating a pre-translation magmatic history. Basaltic magmatism from Bruce Bank is calc-alkaline, akin to Cenozoic magmatism of the South Orkney microcontinent and the South Shetlands Islands, and in agreement with pre-translation tectonic models that place the crustal blocks of the South Scotia Ridge adjacent to the northern Antarctic Peninsula arc. The intra-oceanic arc magmatism at Jane Bank is Late Cretaceous in age (97.2 ± 1.1 Ma), and is not consistent with models suggesting a Miocene origin as part of the ancestral South Sandwich arc. The development of westward-directed subduction adjacent to Jane Bank is predicted in some tectonic models as a consequence of Late Cretaceous plate dynamics that developed prior to the Oligocene – Miocene ancestral arc. Supplementary material: https://doi.org/10.6084/m9.figshare.c.6639909
{"title":"Cretaceous – Paleogene tectonic reconstructions of the South Scotia Ridge and implications for the initiation of subduction in the Scotia Sea","authors":"T. Riley, A. Burton‐Johnson, K. Hogan, A. Carter, P. Leat","doi":"10.1144/jgs2023-013","DOIUrl":"https://doi.org/10.1144/jgs2023-013","url":null,"abstract":"\u0000 The Cenozoic development of the Scotia Sea and opening of Drake Passage led to the dispersal of crustal blocks of the North and South Scotia ridges that today have a strong influence on the pathway of the Antarctic circumpolar current. The pre-translation positions of the crustal fragments of the Scotia ridges are uncertain, with correlations to both the Antarctic and South American plates. We present direct geochronology (\u0000 40\u0000 Ar/\u0000 39\u0000 Ar) from Bruce and Jane banks of the South Scotia Ridge that yield Late Cretaceous – Paleogene ages indicating a pre-translation magmatic history. Basaltic magmatism from Bruce Bank is calc-alkaline, akin to Cenozoic magmatism of the South Orkney microcontinent and the South Shetlands Islands, and in agreement with pre-translation tectonic models that place the crustal blocks of the South Scotia Ridge adjacent to the northern Antarctic Peninsula arc. The intra-oceanic arc magmatism at Jane Bank is Late Cretaceous in age (97.2 ± 1.1 Ma), and is not consistent with models suggesting a Miocene origin as part of the ancestral South Sandwich arc. The development of westward-directed subduction adjacent to Jane Bank is predicted in some tectonic models as a consequence of Late Cretaceous plate dynamics that developed prior to the Oligocene – Miocene ancestral arc.\u0000 \u0000 \u0000 Supplementary material:\u0000 https://doi.org/10.6084/m9.figshare.c.6639909\u0000","PeriodicalId":17320,"journal":{"name":"Journal of the Geological Society","volume":" ","pages":""},"PeriodicalIF":2.7,"publicationDate":"2023-05-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42458379","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}
C. Barnes, J. Majka, R. Callegari, K. Walczak, G. Ziemniak, M. Bukała
The upper gneiss unit is exposed in the northernmost Seve Nappe Complex (SNC) in the Scandinavian Caledonides. To investigate the Caledonian tectonic history of the unit, in-situ white mica and biotite 40 Ar/ 39 Ar geochronology was applied to a leucogranite and two paragneisses. The leucogranite exhibits low strain traits. Biotite porphyroblasts yielded a cooling age of 459 ± 2 Ma. White mica that replace biotite and plagioclase provided a crystallization age of 436 ± 5 Ma. White mica in both paragneisses exhibit high strain characteristics associated with top-to-E sense of shear. One paragneiss provided dispersed late Cambrian to Late Ordovician dates with the youngest approximating deformation at 459 ± 2 Ma. The older dates are interpreted to reflect 40 Ar inherited from a previous metamorphic event. The second paragneiss yielded a deformation age of 434 ± 2 Ma. The collective dataset is interpreted to record: 1) exhumation of the upper gneiss unit at c. 459 Ma, 2) deformation and fluid-infiltration at c. 434 Ma during continental collision. The events closely resemble the deformation histories of other northern SNC terranes. Synthesizing these results with other northern SNC terranes suggests that the Baltican margin underwent oblique, south-to-north subduction during late Cambrian time. Thematic collection: This article is part of the Caledonian Wilson cycle collection available at: https://www.lyellcollection.org/topic/collections/the-caledonian-wilson-cycle Supplementary material: https://doi.org/10.6084/m9.figshare.c.6639993
{"title":"Ordovician-Silurian deformation of the Neoproterozoic upper gneiss unit in the northern Seve Nappe Complex: Implications for subduction of the Baltican margin","authors":"C. Barnes, J. Majka, R. Callegari, K. Walczak, G. Ziemniak, M. Bukała","doi":"10.1144/jgs2022-161","DOIUrl":"https://doi.org/10.1144/jgs2022-161","url":null,"abstract":"\u0000 The upper gneiss unit is exposed in the northernmost Seve Nappe Complex (SNC) in the Scandinavian Caledonides. To investigate the Caledonian tectonic history of the unit,\u0000 in-situ\u0000 white mica and biotite\u0000 40\u0000 Ar/\u0000 39\u0000 Ar geochronology was applied to a leucogranite and two paragneisses. The leucogranite exhibits low strain traits. Biotite porphyroblasts yielded a cooling age of 459 ± 2 Ma. White mica that replace biotite and plagioclase provided a crystallization age of 436 ± 5 Ma. White mica in both paragneisses exhibit high strain characteristics associated with top-to-E sense of shear. One paragneiss provided dispersed late Cambrian to Late Ordovician dates with the youngest approximating deformation at 459 ± 2 Ma. The older dates are interpreted to reflect\u0000 40\u0000 Ar inherited from a previous metamorphic event. The second paragneiss yielded a deformation age of 434 ± 2 Ma. The collective dataset is interpreted to record: 1) exhumation of the upper gneiss unit at c. 459 Ma, 2) deformation and fluid-infiltration at c. 434 Ma during continental collision. The events closely resemble the deformation histories of other northern SNC terranes. Synthesizing these results with other northern SNC terranes suggests that the Baltican margin underwent oblique, south-to-north subduction during late Cambrian time.\u0000 \u0000 \u0000 Thematic collection:\u0000 This article is part of the Caledonian Wilson cycle collection available at:\u0000 https://www.lyellcollection.org/topic/collections/the-caledonian-wilson-cycle\u0000 \u0000 \u0000 Supplementary material:\u0000 https://doi.org/10.6084/m9.figshare.c.6639993\u0000","PeriodicalId":17320,"journal":{"name":"Journal of the Geological Society","volume":" ","pages":""},"PeriodicalIF":2.7,"publicationDate":"2023-05-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41363965","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}
Ery C. Hughes, Lee Saper, Philippa Liggins, Hugh St.C. O'Neill, Edward M. Stolper
The behaviour of sulfur in magmas is complex because it dissolves as both sulfide (S 2− ) and sulfate (S 6+ ) in silicate melt. Interesting aspects of the behaviour of sulfur are the solubility minimum (SS min ) and maxima (SS max ) observed with varying oxygen fugacity ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mi>f</mml:mi> <mml:mrow> <mml:msub> <mml:mrow> <mml:mi mathvariant="normal">O</mml:mi> </mml:mrow> <mml:mn>2</mml:mn> </mml:msub> </mml:mrow> </mml:msub> </mml:math> ). We use a simple ternary model (silicate–S 2 –O 2 ) to explore the varying <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mi>f</mml:mi> <mml:mrow> <mml:msub> <mml:mrow> <mml:mi mathvariant="normal">O</mml:mi> </mml:mrow> <mml:mn>2</mml:mn> </mml:msub> </mml:mrow> </mml:msub> </mml:math> paths where these phenomena occur. Both SS min and SS max occur when S 2− and S 6+ are present in the silicate melt in similar quantities owing to the differing solubility mechanisms of melt species containing these oxidation states of sulfur. At constant T , a minimum in dissolved total S content in vapour-saturated silicate melt ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msubsup> <mml:mi>w</mml:mi> <mml:mrow> <mml:msub> <mml:mrow> <mml:mi mathvariant="normal">S</mml:mi> </mml:mrow> <mml:mrow> <mml:mi mathvariant="normal">T</mml:mi> </mml:mrow> </mml:msub> </mml:mrow> <mml:mi>m</mml:mi> </mml:msubsup> </mml:math> ) occurs along paths of increasing <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mi>f</mml:mi> <mml:mrow> <mml:msub> <mml:mrow> <mml:mi mathvariant="normal">O</mml:mi> </mml:mrow> <mml:mn>2</mml:mn> </mml:msub> </mml:mrow> </mml:msub> </mml:math> and either constant <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mi>f</mml:mi> <mml:mrow> <mml:msub> <mml:mrow> <mml:mi mathvariant="normal">S</mml:mi> </mml:mrow> <mml:mn>2</mml:mn> </mml:msub> </mml:mrow> </mml:msub> </mml:math> or constant P . For paths on which <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msubsup> <mml:mi>w</mml:mi> <mml:mrow> <mml:msub> <mml:mrow> <mml:mi mathvariant="normal">S</mml:mi> </mml:mrow> <mml:mrow> <mml:mi mathvariant="normal">T</mml:mi> </mml:mrow> </mml:msub> </mml:mrow> <mml:mi>m</mml:mi> </mml:msubsup> </mml:math> is held constant with increasing <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mi>f</mml:mi> <mml:mrow> <mml:msub> <mml:mrow> <mml:mi mathvariant="normal">O</mml:mi> </mml:mrow> <mml:mn>2</mml:mn> </mml:msub> </mml:mrow> </mml:msub> </mml:math> , the SS min is expressed as a maximum in P . The SS min occurs when the fraction of S 6+ in the melt ([S 6+ /S T ] m ) is 0.25 for constant <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mi>f</mml:mi> <
硫在岩浆中的行为是复杂的，因为它在硅酸盐熔体中以硫化物(s2−)和硫酸盐(s6 +)的形式溶解。硫的行为有趣的方面是溶解度最小值(SS min)和最大值(SS max)随氧逸度(o2)的变化而变化。我们使用一个简单的三元模型(硅酸盐- s2 - o2)来探索这些现象发生的不同的o2路径。由于含硫氧化态的熔体溶解度机制不同，当s2 -和s6 +在硅酸盐熔体中以相似数量存在时，SS min和SS max都会发生。当温度恒定时，蒸汽饱和硅酸盐熔体中溶解总硫含量(w S T m)的最小值出现在o2增加和fs2恒定或P恒定的路径上。对于w S T m随o2的增加而保持不变的路径，SS min表示为P的最大值。当熔体中s6 +的分数([s6 + /S T] m)为0.25时，熔体中s6 +的分数([s6 + /S T] m)为0.25，当wst m和P恒定时，[s6 + /S T] m≈0.75时，出现SS min。在我们建模的简单系统中，在封闭或开放系统降压过程中，不会遇到最小的w - S - T - m。然而，在脱气过程中，SS min标志着从还原到氧化的变化。当硅酸盐熔体与至少两相(蒸汽、硫化物熔体和/或硬石膏)成倍饱和时，就会出现各种SS最大值。SS min和SS max是地幔熔融、岩浆混合和脱气等岩浆过程的重要特征。这些概念影响使用熔体包裹体计算蒸汽饱和压力、二氧化氧和二氧化硫排放压力。补充材料:用于创建图形的其他信息和数据可在https://doi.org/10.6084/m9.figshare.c.6274527上获得主题集合:本文是地球系统硫集合的一部分，可在https://www.lyellcollection.org/topic/collections/sulfur-in-the-earth-system上获得
{"title":"The sulfur solubility minimum and maximum in silicate melt","authors":"Ery C. Hughes, Lee Saper, Philippa Liggins, Hugh St.C. O'Neill, Edward M. Stolper","doi":"10.1144/jgs2021-125","DOIUrl":"https://doi.org/10.1144/jgs2021-125","url":null,"abstract":"The behaviour of sulfur in magmas is complex because it dissolves as both sulfide (S 2− ) and sulfate (S 6+ ) in silicate melt. Interesting aspects of the behaviour of sulfur are the solubility minimum (SS min ) and maxima (SS max ) observed with varying oxygen fugacity ( <mml:math xmlns:mml=\"http://www.w3.org/1998/Math/MathML\" overflow=\"scroll\"> <mml:msub> <mml:mi>f</mml:mi> <mml:mrow> <mml:msub> <mml:mrow> <mml:mi mathvariant=\"normal\">O</mml:mi> </mml:mrow> <mml:mn>2</mml:mn> </mml:msub> </mml:mrow> </mml:msub> </mml:math> ). We use a simple ternary model (silicate–S 2 –O 2 ) to explore the varying <mml:math xmlns:mml=\"http://www.w3.org/1998/Math/MathML\" overflow=\"scroll\"> <mml:msub> <mml:mi>f</mml:mi> <mml:mrow> <mml:msub> <mml:mrow> <mml:mi mathvariant=\"normal\">O</mml:mi> </mml:mrow> <mml:mn>2</mml:mn> </mml:msub> </mml:mrow> </mml:msub> </mml:math> paths where these phenomena occur. Both SS min and SS max occur when S 2− and S 6+ are present in the silicate melt in similar quantities owing to the differing solubility mechanisms of melt species containing these oxidation states of sulfur. At constant T , a minimum in dissolved total S content in vapour-saturated silicate melt ( <mml:math xmlns:mml=\"http://www.w3.org/1998/Math/MathML\" overflow=\"scroll\"> <mml:msubsup> <mml:mi>w</mml:mi> <mml:mrow> <mml:msub> <mml:mrow> <mml:mi mathvariant=\"normal\">S</mml:mi> </mml:mrow> <mml:mrow> <mml:mi mathvariant=\"normal\">T</mml:mi> </mml:mrow> </mml:msub> </mml:mrow> <mml:mi>m</mml:mi> </mml:msubsup> </mml:math> ) occurs along paths of increasing <mml:math xmlns:mml=\"http://www.w3.org/1998/Math/MathML\" overflow=\"scroll\"> <mml:msub> <mml:mi>f</mml:mi> <mml:mrow> <mml:msub> <mml:mrow> <mml:mi mathvariant=\"normal\">O</mml:mi> </mml:mrow> <mml:mn>2</mml:mn> </mml:msub> </mml:mrow> </mml:msub> </mml:math> and either constant <mml:math xmlns:mml=\"http://www.w3.org/1998/Math/MathML\" overflow=\"scroll\"> <mml:msub> <mml:mi>f</mml:mi> <mml:mrow> <mml:msub> <mml:mrow> <mml:mi mathvariant=\"normal\">S</mml:mi> </mml:mrow> <mml:mn>2</mml:mn> </mml:msub> </mml:mrow> </mml:msub> </mml:math> or constant P . For paths on which <mml:math xmlns:mml=\"http://www.w3.org/1998/Math/MathML\" overflow=\"scroll\"> <mml:msubsup> <mml:mi>w</mml:mi> <mml:mrow> <mml:msub> <mml:mrow> <mml:mi mathvariant=\"normal\">S</mml:mi> </mml:mrow> <mml:mrow> <mml:mi mathvariant=\"normal\">T</mml:mi> </mml:mrow> </mml:msub> </mml:mrow> <mml:mi>m</mml:mi> </mml:msubsup> </mml:math> is held constant with increasing <mml:math xmlns:mml=\"http://www.w3.org/1998/Math/MathML\" overflow=\"scroll\"> <mml:msub> <mml:mi>f</mml:mi> <mml:mrow> <mml:msub> <mml:mrow> <mml:mi mathvariant=\"normal\">O</mml:mi> </mml:mrow> <mml:mn>2</mml:mn> </mml:msub> </mml:mrow> </mml:msub> </mml:math> , the SS min is expressed as a maximum in P . The SS min occurs when the fraction of S 6+ in the melt ([S 6+ /S T ] m ) is 0.25 for constant <mml:math xmlns:mml=\"http://www.w3.org/1998/Math/MathML\" overflow=\"scroll\"> <mml:msub> <mml:mi>f</mml:mi> <","PeriodicalId":17320,"journal":{"name":"Journal of the Geological Society","volume":"24 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-05-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136011885","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}
Regional structural cross-sections based on seismic, borehole and surface data portray the foothills geometry of the Tierra del Fuego fold-thrust belt. Andean contraction was accommodated by two main deformation mechanisms: 1) A lower duplex thrust system that involves mainly Cretaceous deposits, with floor and roof thrusts at the base of the Cretaceous and close to the base of the Cenozoic, respectively; and 2) A series of detachment and faulted detachment anticlines in the Cenozoic, detached in mudstones above the roof thrust of the underlying duplex thrust system. Less common structures include fault bend and fault propagation folds. Basement fault reactivation is only locally important, with most Jurassic grabens and half-grabens preserved without inversion. Shortening along the foothills is modest, with values ranging from ∼8 to 4.6 kilometers. This region of the fold-thrust belt has hydrocarbon exploration interest; however, it is largely underexplored. Several large anticlines preserving Cenozoic clastic rocks have not been tested to date. The key risk for these structures is the charge, as the thick mudstone package forming their detachment isolates potential Cenozoic reservoirs from the Lower Cretaceous source rocks. Duplex thrust systems at depth may constitute a potential exploration play, provided brittle intervals were naturally fractured.
{"title":"Structural styles of the Tierra del Fuego fold-thrust belt foothills, Argentina","authors":"F. Fuentes","doi":"10.1144/jgs2022-182","DOIUrl":"https://doi.org/10.1144/jgs2022-182","url":null,"abstract":"Regional structural cross-sections based on seismic, borehole and surface data portray the foothills geometry of the Tierra del Fuego fold-thrust belt. Andean contraction was accommodated by two main deformation mechanisms: 1) A lower duplex thrust system that involves mainly Cretaceous deposits, with floor and roof thrusts at the base of the Cretaceous and close to the base of the Cenozoic, respectively; and 2) A series of detachment and faulted detachment anticlines in the Cenozoic, detached in mudstones above the roof thrust of the underlying duplex thrust system. Less common structures include fault bend and fault propagation folds. Basement fault reactivation is only locally important, with most Jurassic grabens and half-grabens preserved without inversion. Shortening along the foothills is modest, with values ranging from ∼8 to 4.6 kilometers. This region of the fold-thrust belt has hydrocarbon exploration interest; however, it is largely underexplored. Several large anticlines preserving Cenozoic clastic rocks have not been tested to date. The key risk for these structures is the charge, as the thick mudstone package forming their detachment isolates potential Cenozoic reservoirs from the Lower Cretaceous source rocks. Duplex thrust systems at depth may constitute a potential exploration play, provided brittle intervals were naturally fractured.","PeriodicalId":17320,"journal":{"name":"Journal of the Geological Society","volume":" ","pages":""},"PeriodicalIF":2.7,"publicationDate":"2023-04-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47844137","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}
High resolution correlations between boreholes are commonly based on a combination of geophysical well log data and biostratigraphy and, when these conflict, resolution can be contentious and difficult. Such a situation exists in the Middle Turonian chalks of the Anglo-Paris Basin, where electrical resistivity logs, registering thin but seemingly laterally continuous beds of clay-rich chalk (marls) in mostly uncored boreholes, provide apparently straightforward correlations across broad regions. In contrast, detailed biostratigraphical analysis using microcrinoids provides very different results, showing the presence of a major hiatus associated with a hardground and differing significantly from the geophysical correlations. Detailed re-examination of this contentious problem, utilising exposures adjacent to boreholes, demonstrates the supremacy of detailed biostratigraphical analysis, independently supported by regional thickness patterns, cyclostratigraphy and geochemistry. Although closely spaced geophysical well logs can afford convincing correlations, their use in correlation over broader geographical regions leads to erroneous and misleading conclusions.
{"title":"Biostratigraphy versus geophysics; correlation of Middle Turonian chalks in the Anglo-Paris Basin","authors":"Andy Gale","doi":"10.1144/jgs2023-010","DOIUrl":"https://doi.org/10.1144/jgs2023-010","url":null,"abstract":"High resolution correlations between boreholes are commonly based on a combination of geophysical well log data and biostratigraphy and, when these conflict, resolution can be contentious and difficult. Such a situation exists in the Middle Turonian chalks of the Anglo-Paris Basin, where electrical resistivity logs, registering thin but seemingly laterally continuous beds of clay-rich chalk (marls) in mostly uncored boreholes, provide apparently straightforward correlations across broad regions. In contrast, detailed biostratigraphical analysis using microcrinoids provides very different results, showing the presence of a major hiatus associated with a hardground and differing significantly from the geophysical correlations. Detailed re-examination of this contentious problem, utilising exposures adjacent to boreholes, demonstrates the supremacy of detailed biostratigraphical analysis, independently supported by regional thickness patterns, cyclostratigraphy and geochemistry. Although closely spaced geophysical well logs can afford convincing correlations, their use in correlation over broader geographical regions leads to erroneous and misleading conclusions.","PeriodicalId":17320,"journal":{"name":"Journal of the Geological Society","volume":" ","pages":""},"PeriodicalIF":2.7,"publicationDate":"2023-04-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46235439","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}
K. Edgar, Lewis Haller, Daniel D. Cashmore, E. Dunne, R. Butler
Dinosaur tracks are a key means of determining the palaeoecology and distribution of dinosaurs through time. They provide a highly complementary information source to the body (skeletal) fossil record but differ in preserving direct evidence of animals’ interactions with their environment. The UK has a rich history of ∼200 yrs of dinosaur track discovery but no recent synthesis exists. Here, we present a new dataset of dinosaur tracks in the UK. This dataset shows a close correlation between the distribution of terrestrial sediments and the preservation of dinosaur tracks through the Mesozoic, providing discrete snapshots into dinosaur communities in the Upper Triassic, Middle Jurassic and Lower Cretaceous. The dinosaur track record shows similar broad patterns of diversity and relative abundance of the major dinosaur groups (Theropoda, Sauropodomorpha, Ornithopoda, and Thyreophora) through time to the body fossil record, although differs in that body fossils are found (albeit infrequently) in marine sediments. There is a broad trend towards higher numbers of track occurrences through time and a notable increase in the relative abundance of ornithopod tracks following the Jurassic-Cretaceous boundary. The track record remains an underutilised resource with the potential to provide a much fuller view of Mesozoic dinosaur ecosystems. Supplementary material: https://doi.org/10.6084/m9.figshare.c.6606634
{"title":"Stratigraphic and geographic distribution of dinosaur tracks in the UK","authors":"K. Edgar, Lewis Haller, Daniel D. Cashmore, E. Dunne, R. Butler","doi":"10.1144/jgs2023-003","DOIUrl":"https://doi.org/10.1144/jgs2023-003","url":null,"abstract":"Dinosaur tracks are a key means of determining the palaeoecology and distribution of dinosaurs through time. They provide a highly complementary information source to the body (skeletal) fossil record but differ in preserving direct evidence of animals’ interactions with their environment. The UK has a rich history of ∼200 yrs of dinosaur track discovery but no recent synthesis exists. Here, we present a new dataset of dinosaur tracks in the UK. This dataset shows a close correlation between the distribution of terrestrial sediments and the preservation of dinosaur tracks through the Mesozoic, providing discrete snapshots into dinosaur communities in the Upper Triassic, Middle Jurassic and Lower Cretaceous. The dinosaur track record shows similar broad patterns of diversity and relative abundance of the major dinosaur groups (Theropoda, Sauropodomorpha, Ornithopoda, and Thyreophora) through time to the body fossil record, although differs in that body fossils are found (albeit infrequently) in marine sediments. There is a broad trend towards higher numbers of track occurrences through time and a notable increase in the relative abundance of ornithopod tracks following the Jurassic-Cretaceous boundary. The track record remains an underutilised resource with the potential to provide a much fuller view of Mesozoic dinosaur ecosystems.\u0000 \u0000 Supplementary material:\u0000 https://doi.org/10.6084/m9.figshare.c.6606634\u0000","PeriodicalId":17320,"journal":{"name":"Journal of the Geological Society","volume":" ","pages":""},"PeriodicalIF":2.7,"publicationDate":"2023-04-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49315341","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}
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