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Sedimentary provenance of the Upper Devonian Old Red Sandstone of southern Ireland: An integrated multi-proxy detrital geochronology study 爱尔兰南部上泥盆纪老红砂岩的沉积出处:综合多代理析出地质年代研究
Journal of the Geological Society Pub Date : 2024-07-03 DOI: 10.1144/jgs2023-110
B. Fairey, Aidan Kerrison, P. Meere, Kieran F. Mulchrone, M. Zieger-Hofmann, A. Gärtner, Benita-Lisette Sonntag, U. Linnemann, Klaudia F. Kuiper, M. Ennis, Chris Mark, N. Cogné, David Chew
{"title":"Sedimentary provenance of the Upper Devonian Old Red Sandstone of southern Ireland: An integrated multi-proxy detrital geochronology study","authors":"B. Fairey, Aidan Kerrison, P. Meere, Kieran F. Mulchrone, M. Zieger-Hofmann, A. Gärtner, Benita-Lisette Sonntag, U. Linnemann, Klaudia F. Kuiper, M. Ennis, Chris Mark, N. Cogné, David Chew","doi":"10.1144/jgs2023-110","DOIUrl":"https://doi.org/10.1144/jgs2023-110","url":null,"abstract":"\u0000 The Devonian Old Red Sandstone (ORS) magnafacies of southern Ireland is hosted in the Lower Devonian Dingle Basin and the Upper Devonian Munster Basin. Following the closure of the Iapetus Ocean during the Caledonian Orogeny, the Dingle Basin developed as a pull-apart structure before being deformed by Acadian tectonic activity. The Munster Basin developed as a half-graben structure in response to post-Acadian N-S extension in the region. Thus, the Irish ORS provides insights into the region's tectonic history due to its temporal and spatial proximity to the Caledonian (∼475-425 Ma), Acadian (∼400-390 Ma) and Variscan orogenic events (∼390-290 Ma). This study presents the first detrital zircon and apatite U-Pb geochronological data for the UORS in southern Ireland in addition to detrital white mica\u0000 40\u0000 Ar/\u0000 39\u0000 Ar geochronological data to help unravel the depositional history of the Irish UORS and to assess the possible role of sedimentary recycling in Upper Devonian basin development.\u0000 \u0000  Most Upper ORS (UORS) samples contain few late Neoproterozoic detrital zircon grains and are instead dominated by early Palaeozoic and ca. 1.1 Ga zircons. These populations represent recycling of northerly-derived Ordovician to Silurian strata of the Southern-Uplands-Longford-Down terrane which are of Laurentian affinity, and not recycling of Lower ORS (which contain a significant number of late Neoproterozoic detrital zircons) as previously thought. Similar detrital zircon dates have been observed in Givetian-Frasnian quartzites of the Pulo do Lobo Zone on the Iberian Peninsula, providing a possible Rheic Ocean link with the UORS.","PeriodicalId":507891,"journal":{"name":"Journal of the Geological Society","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-07-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141683635","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
We don't know when plate tectonics began 我们不知道板块构造始于何时
Journal of the Geological Society Pub Date : 2024-04-25 DOI: 10.1144/jgs2023-212
T. M. Harrison
{"title":"We don't know when plate tectonics began","authors":"T. M. Harrison","doi":"10.1144/jgs2023-212","DOIUrl":"https://doi.org/10.1144/jgs2023-212","url":null,"abstract":"\u0000 Geologists have speculated when plate tectonics began since the dawn of that revolution, with recent estimates ranging from the last 20% of Earth history to within the first 5%. All such estimates rest on six types of evidence: preservation of modern plate tectonic features, detrital-zircon age spectra, trace element-isotope geochemistry, atmosphere-crust-mantle exchange, paleomagnetism, and model calculations. ‘Burke's Law’ suggests that the null hypothesis puts the onus on demonstrating when plate tectonics was\u0000 not\u0000 operating rather than requiring observation of plate tectonic features in the geologic record as assemblages presumed characteristic of plate tectonics could be lost from the geologic record (due to preservation biases) or never existed (due to secular changes). This issue has become salient as our community appears to be coalescing around the paradigm that plate tectonics began during the late Archean in the face of problematic evidence, much the same way it's done repeatedly over the past century (e.g., rejecting continental drift in preference to geosyncline theory). I summarize evidence from the six evidentiary types and conclude that we don't know when plate tectonics initiated. Claiming we do forestalls the day that we might truly understand an event at the heart of Earth history and habitability.\u0000","PeriodicalId":507891,"journal":{"name":"Journal of the Geological Society","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-04-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140656703","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Geochemistry and magmatic petrology of meta-ophiolites from the Bajgan Complex (Makran Accretionary Prism, SE Iran): New insights on the nature of the Early Cretaceous Middle East Neotethys 来自 Bajgan 复合体(伊朗东南部马克兰断积棱岩)的元玢岩的地球化学和岩浆岩石学:关于早白垩世中东新特提斯性质的新见解
Journal of the Geological Society Pub Date : 2024-04-25 DOI: 10.1144/jgs2024-043
E. Saccani, Edoardo Barbero, M. Delavari, A. Dolati, Valentina Brombin, M. Marroni, L. Pandolfi
{"title":"Geochemistry and magmatic petrology of meta-ophiolites from the Bajgan Complex (Makran Accretionary Prism, SE Iran): New insights on the nature of the Early Cretaceous Middle East Neotethys","authors":"E. Saccani, Edoardo Barbero, M. Delavari, A. Dolati, Valentina Brombin, M. Marroni, L. Pandolfi","doi":"10.1144/jgs2024-043","DOIUrl":"https://doi.org/10.1144/jgs2024-043","url":null,"abstract":"\u0000 The Bajgan Complex in the North Makran Domain (Makran Accretionary Prism) comprises disrupted meta-ophiolitic sequences originating from oceanic crust protoliths. They include ultramafic and mafic cumulates, isotropic gabbros, plagiogranites, and basalts. Ultramafic-mafic cumulates and plagiogranites exhibit compositions akin to rocks formed in mid-ocean ridge settings. Isotropic gabbro and basalt protoliths can be subdivided in three distinct geochemical types. Type-1 rocks is sub-alkaline (Nb/Y < 0.1) with low Th, Nb, and Ta contents and La\u0000 N\u0000 /Yb\u0000 N\u0000 ratios <1, resembling those of normal-type (N-) mid-ocean ridge basalts (MORB). Type-2 rocks display slight enrichment in Th, Ta, Nb (Nb/Y = 0.36 – 0.45), and La\u0000 N\u0000 /Yb\u0000 N\u0000 = 2.12 – 3.20, resembling the chemistry of enriched-type (E-) MORB. Type-3 basalts show an alkaline nature (Nb/Y=0.88-1.82), significant Th, Ta, Nb enrichment, and high La\u0000 N\u0000 /Yb\u0000 N\u0000 ratios (7.01 – 20.08), resembling the chemistry of alkaline basalts (OIB). Petrogenetic modeling indicates that N-MORB protoliths originated from a depleted MORB mantle source, while E-MORB and OIB protoliths were generated from partial melting of sub-oceanic depleted sources that underwent varying degrees of OIB-type enrichment. The Bajgan meta-ophiolitic protoliths were formed within a Late Jurassic to Cretaceous oceanic basin influenced by mantle plume activity and plume-ridge interaction.\u0000 \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.7193937\u0000","PeriodicalId":507891,"journal":{"name":"Journal of the Geological Society","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-04-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140653701","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Indicative meanings of geological sea-level indicators in the Solent region and Sussex coast (south coast of England) and implications for uplift rates 索伦特地区和苏塞克斯海岸(英格兰南部海岸)地质海平面指标的指示性含义及其对隆起率的影响
Journal of the Geological Society Pub Date : 2024-04-15 DOI: 10.1144/jgs2023-120
R. Briant, Martin R. Bates, Jenni Robertson, J. Schwenninger, John E. Whittaker
{"title":"Indicative meanings of geological sea-level indicators in the Solent region and Sussex coast (south coast of England) and implications for uplift rates","authors":"R. Briant, Martin R. Bates, Jenni Robertson, J. Schwenninger, John E. Whittaker","doi":"10.1144/jgs2023-120","DOIUrl":"https://doi.org/10.1144/jgs2023-120","url":null,"abstract":"The Solent Region and Sussex coastal plain in southern England have preserved palaeo- sea-level indicators from multiple interglacial periods, with a particularly complete record of deposition throughout the last interglacial. However, as yet, none of the research on these indicators have fully addressed the relationship of the different types of deposits preserved to mean sea-level. In this paper we apply recent approaches to estimating past relative sea-levels based on applying modern analogues to understand the indicative meaning of these indicators. We also apply a synchronous correlation model previously developed on rapidly uplifting coastlines to assess uplift rates. The uplift rates required to match the elevations of sequences suggest a significant decrease in uplift rates between the Late Wolstonian Substage and Ipswichian Stage – i.e. the c. 240 ka and c. 125 ka sea-level highstands, broadly equivalent to Marine Isotope Stages (MIS) 7 and 5e. This coincides in time with the final opening of the Straits of Dover.\u0000 \u0000 Supplementary material:\u0000 https://doi.org/10.6084/m9.figshare.c.7172532\u0000","PeriodicalId":507891,"journal":{"name":"Journal of the Geological Society","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-04-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140701812","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Neogene erosion surfaces and the Andean Uplift in Northern Peru 秘鲁北部新近纪侵蚀表面和安第斯隆起
Journal of the Geological Society Pub Date : 2024-04-15 DOI: 10.1144/jgs2023-089
J. J. Wilson
{"title":"Neogene erosion surfaces and the Andean Uplift in Northern Peru","authors":"J. J. Wilson","doi":"10.1144/jgs2023-089","DOIUrl":"https://doi.org/10.1144/jgs2023-089","url":null,"abstract":"The Andean flank in central Peru is characterized by stepped profiles involving up to 20 surfaces and pediments resulting from multiple episodes of uplift and erosion. The study area exhibits the same sequence of surfaces and pediments. Moreover, the erosional features are also recognised in the Eastern Cordillera in northern Peru. This report focuses on the highest seven features in the range ∼2800-4700m. Remnants of the four surfaces at more than 3800m, which were formed during the interval ∼18-12Ma, are found only south of latitude 6°- 6.5°S. The Miocene metallogenic belt associated with the Western Cordillera terminates abruptly at that same latitude. The area north of ∼6°S. does not have any features higher than ∼3500m, which is interpreted as indicating a later initiation of uplift. It also lacks any sign of magmatic activity. On the basis of these factors the Central Andes are considered to terminate at ∼6°S, the ranges to the north being assigned to the Northern Andes. Once episodic uplift was initiated in the area north of 6°S it continued at the same rhythm as in the region to the south. Moreover, there was no apparent change in the pattern of episodic uplift when the normal subduction regime changed to a flat slab regime at ∼11Ma, probably as a result of the subduction of the Inca Plateau. The distribution of the erosion surfaces indicates that episodic uplift affected the whole of the Andean block in northern Peru. It appears that the individual episodes occurred simultaneously and produced the same amount of uplift over the whole width of the cordilleras. Moreover, there is no sign of any interruption in the process, implying continuous orogeny from the Middle Miocene onwards.","PeriodicalId":507891,"journal":{"name":"Journal of the Geological Society","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-04-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140701640","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Neotectonics on the Namuncurá (Burdwood) Bank: Unveiling seafloor strike-slip processes along the North Scotia Ridge Namuncurá(伯德伍德)浅滩的新构造:揭示北斯科舍海脊的海底走向滑动过程
Journal of the Geological Society Pub Date : 2024-04-15 DOI: 10.1144/jgs2023-215
J. Ormazabal, S. Principi, F. Palma, D. Bran, J. Isola, F. Esteban, A. Tassone
{"title":"Neotectonics on the Namuncurá (Burdwood) Bank: Unveiling seafloor strike-slip processes along the North Scotia Ridge","authors":"J. Ormazabal, S. Principi, F. Palma, D. Bran, J. Isola, F. Esteban, A. Tassone","doi":"10.1144/jgs2023-215","DOIUrl":"https://doi.org/10.1144/jgs2023-215","url":null,"abstract":"\u0000 The North Scotia Ridge is the offshore morphostructural expression of the left-lateral transcurrent South America-Scotia Plate Boundary. Several blocks compose the ridge, including the scarcely studied Namuncurá Bank (NB, also known as Burdwood). We present the first detailed study of active structures on the seafloor of the western NB from a database of 3D and 2D seismic data, multibeam bathymetry, and sub-bottom profiles. This work assesses the architecture, style of deformation and Cenozoic evolution of NB, where several groups of faults, and\u0000 en echelon\u0000 folding, affects the seabed and shallow sub-bottom. These features compound the northernmost structures associated with a releasing bend, fitting well with a left-lateral Riedel shear model oriented at N74°E, slightly rotated with respect to the present-day plate boundary stress regime. The current tectonic scenario started with a main deformational phase in the Neogene, partially distributed by the Malvinas Fold-Thrust Belt, while modern deformation continues to be conditioned by pre-existing structures. This study allows for a better understanding of the tectonics of the North Scotia Ridge, a morphostructure that influences the circulation of the Antarctic Circumpolar Current thus impacting the global climate.\u0000","PeriodicalId":507891,"journal":{"name":"Journal of the Geological Society","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-04-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140703633","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
First identification of Late Mesozoic intraplate magmatism in the Chinese North Tianshan: Implications for the orogenic architecture and crustal evolution 首次发现中国北天山晚中生代板内岩浆活动:对造山构造和地壳演化的启示
Journal of the Geological Society Pub Date : 2024-04-10 DOI: 10.1144/jgs2023-176
Fujun Wang, Zhiyuan He, Rongfeng Ge, Meng Luo, Bihai Zheng, Zhiyong Zhang, Rongsong Tian, Yuanyuan Cao, Wenbin Zhu
{"title":"First identification of Late Mesozoic intraplate magmatism in the Chinese North Tianshan: Implications for the orogenic architecture and crustal evolution","authors":"Fujun Wang, Zhiyuan He, Rongfeng Ge, Meng Luo, Bihai Zheng, Zhiyong Zhang, Rongsong Tian, Yuanyuan Cao, Wenbin Zhu","doi":"10.1144/jgs2023-176","DOIUrl":"https://doi.org/10.1144/jgs2023-176","url":null,"abstract":"\u0000 The formation and dynamics of granitoids in an intra-continental setting are crucial for understanding the architecture and evolution of continental crust. Here, we report geochronological, geochemical, and Sr-Nd-Hf isotopic data for newly discovered late Mesozoic granitic intrusions in the Tianshan belt, northwestern China. These granitoids are I-type granites derived from an igneous precursor and were emplaced during ∼145-132 Ma. They have positive\u0000 \u0000 \u0000 ε\u0000 \u0000 \u0000 Nd\u0000 (t) values and young Nd model ages, together with relatively low Sr/Y ratios, indicating that they might have originated from partial melting of the juvenile lower crust. There is a prominent decoupling between zircon Hf and bulk rock Nd isotopes, which may have resulted from the early crystallization of Ti-rich minerals. These granitic intrusions also display subduction-related geochemical characteristics, which are likely inherited from the Paleozoic crustal sources that were metasomatized by subduction-related fluids. We conclude that these late Mesozoic granitoids were emplaced in an intra-continental setting, and were likely triggered by thermal relaxation due to crustal shortening and thickening. These data further imply that the Tianshan has changed into crustal reworking during the Mesozoic from its prominent crustal growth in the Paleozoic.\u0000 \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.7167890\u0000","PeriodicalId":507891,"journal":{"name":"Journal of the Geological Society","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-04-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140720117","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Watermass architecture of the Ordovician-Silurian Yangtze Sea (South China) and its palaeogeographic implications 奥陶纪-志留纪长江海(华南)的水体结构及其古地理影响
Journal of the Geological Society Pub Date : 2024-04-10 DOI: 10.1144/jgs2023-024
Xinqian Wang, Chen Zhan, T. Algeo, Jun Shen, Zhanhong Liu
{"title":"Watermass architecture of the Ordovician-Silurian Yangtze Sea (South China) and its palaeogeographic implications","authors":"Xinqian Wang, Chen Zhan, T. Algeo, Jun Shen, Zhanhong Liu","doi":"10.1144/jgs2023-024","DOIUrl":"https://doi.org/10.1144/jgs2023-024","url":null,"abstract":"\u0000 During the Late Ordovician Hirnantian Ice Age, the South China Craton experienced large changes in climate, eustasy, and environmental conditions, but their impact on the watermass architecture of the Yangtze Sea has not been thoroughly evaluated to date. Here, we reconstruct the salinity-redox structure of the Yangtze Sea based on five Upper Ordovician-lower Silurian shale successions representing a lateral transect, from a deep-water area of the Inner Yangtze Sea (IYS; Shuanghe section) across the shallow Hunan-Hubei Arch (Pengye, Jiaoye, and Qiliao sections) to the relatively deep-water Outer Yangtze Sea (OYS; Wangjiawan section). Carbon-isotope (\u0000 \u0000 \u0000 δ\u0000 \u0000 \u0000 13\u0000 C\u0000 org\u0000 ) profiles show that the Guanyinqiao Bed (recording peak Hirnantian glaciation) thins and is less completely preserved at sites on the flanks of the Hunan-Hubei Arch than in deeper-water areas to the SW and NE, reflecting bathymetric influences. Watermass salinities were mainly marine at Shuanghe and brackish at the other four study sites, with little variation between Interval I (pre-glaciation), Interval II (Hirnantian glaciation), and Interval III (post-glaciation). Redox proxies document mainly euxinia at Shuanghe and Wangjiawan and suboxia at the other sites during Interval I, with shifts toward more reducing (mostly euxinic) conditions at most sites during Intervals II and III, which shows that all study sections were deep enough to remain below the redoxcline during the glacio-eustatic lowstand. Two features of the Shuanghe section mark it as being unusual: it alone exhibits fully marine salinities, implying greater proximity to the open ocean than for the other four sites, and it exhibits an especially large shift toward more reducing conditions during Interval III (i.e., the post-Hirnantian transgression), implying greater water depths. These features are difficult to reconcile with the standard palaeogeographic model for the Ordovician-Silurian South China Craton, which is characterized by a geographically enclosed and restricted IYS and a more-open OYS, arguing instead for the SW end of the IYS having been connected to the global ocean and the OYS having been a restricted oceanic cul-de-sac. A review of sedimentologic and facies data for the IYS region suggests that our re-interpretation of the Ordovician-Silurian palaeogeography of the South China Craton is viable, although further vetting of this hypothesis will be needed.\u0000 \u0000 \u0000 Thematic collection:\u0000 This article is part of the Chemical Evolution of the Mid-Paleozoic Earth System and Biotic Response collection available at:\u0000 https://www.lyellcollection.org/topic/collections/chemical-evolution-of-the-mid-paleozoic-earth-system\u0000 \u0000 \u0000 Supplementary material:\u0000 https://doi.org/10.6084/m9.figshare.c.7170648\u0000","PeriodicalId":507891,"journal":{"name":"Journal of the Geological Society","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-04-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140720304","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 1
Tracing remnant of subducted Indian felsic crust: Insight from zircon studies 追踪印度熔岩地壳俯冲残余:锆石研究的启示
Journal of the Geological Society Pub Date : 2024-04-10 DOI: 10.1144/jgs2023-116
B. Mukherjee, Tania Saha
{"title":"Tracing remnant of subducted Indian felsic crust: Insight from zircon studies","authors":"B. Mukherjee, Tania Saha","doi":"10.1144/jgs2023-116","DOIUrl":"https://doi.org/10.1144/jgs2023-116","url":null,"abstract":"Zircon is a common mineral in nature that survives varied pressure and temperature conditions in the subduction process. It has excellent ability to reveal progressive metamorphic history. Hence it is useful in reconstruct the subduction tectonics in the collisional orogenic belts. In the Tso Morari Gneiss of Indus Suture Zone, Himalaya, eclogite boudins have registered imprint of subduction related ultrahigh-pressure (UHP) metamorphism, this imprint is however missing in the host gneisses. To search the missing link, zircons of the gneisses are studied. The zircons overgrowth and the numerous mineral inclusions indicating, metamorphic responses of the gneisses. The Raman spectra of minerals show, cores of the zircon consist of apatite and quartz, and in the surrounding overgrowth preserves quartz-coesite, c-polymorphs, and other metamorphic minerals. The distribution pattern of these minerals in the zircons is consistent with the Th/U ratios ranging 0.30 to 0.01 recognizes inner magmatic and outer metamorphic domains. The U-Pb ages from inner magmatic, at c. 500 Ma, and from outer metamorphic growth at c.45-42 Ma, suggests the former is the protolith age and later is metamorphic ages of the gneisses. The tectonic interpretation reveals, the subduction of Indian felsic crust to UHP depth (>100km) at c. 45 Ma.\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","PeriodicalId":507891,"journal":{"name":"Journal of the Geological Society","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-04-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140719282","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
The erosional and weathering response to arc-continent collision in New Guinea 新几内亚弧洲碰撞的侵蚀和风化反应
Journal of the Geological Society Pub Date : 2024-04-09 DOI: 10.1144/jgs2023-207
P. Clift, Yifan Du, M. Mohtadi, Katharina Pahnke, Mika Sutorius, Philipp Böning
{"title":"The erosional and weathering response to arc-continent collision in New Guinea","authors":"P. Clift, Yifan Du, M. Mohtadi, Katharina Pahnke, Mika Sutorius, Philipp Böning","doi":"10.1144/jgs2023-207","DOIUrl":"https://doi.org/10.1144/jgs2023-207","url":null,"abstract":"\u0000 Arc-continent collision is a fundamental stage in the plate tectonic cycle that allows the continental crust to grow and can influence global climate through chemical weathering. Collision between Australia and the oceanic North Coast Range-New Britain Arc began in the Middle Miocene resulting in uplift of the modern New Guinea Highlands. The temporal evolution of this collision and its erosional and weathering impacts is reconstructed here using sedimentary archives from the Gulf of Papua. Sr and Nd isotopes show dominant erosion from igneous arc-ophiolite crust, accounting for ∼40−70% of the total flux in the Early Miocene, and rising to ∼80−90% at 8 Ma, before falling again to 72−83% by the present day. Greater erosion from Australia-derived units accelerated in the Pliocene, like the classic Taiwan collision but with greater erosion from arc rather than continental units. Chemical alteration of the sediment increased through time, especially since ∼5 Ma, consistent with increasing kaolinite indicative of more tropical weathering. Erosion was focused in the high topography where mafic arc units are preferentially exposed. Comparison of sediment with bedrock compositions implies that the source terrains have been more efficient at removing CO\u0000 2\u0000 from the atmosphere compared to Himalayan drainages.\u0000 \u0000 \u0000 Supplementary material:\u0000 https://doi.org/10.6084/m9.figshare.c.7168147\u0000","PeriodicalId":507891,"journal":{"name":"Journal of the Geological Society","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-04-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140725337","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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