Abstract Tetrapod (amphibian and amniote) fossils of Carboniferous age are known almost exclusively from the southern part of a palaeoequatorial Euramerican province. The stratigraphic distribution of Carboniferous tetrapod fossils is used to identify five land-vertebrate faunachrons: (1) Hortonbluffian (Givetian–early Visean), the time between the first appearance datum (FAD) of tetrapods to the beginning of the Doran; (2) Doran (late Visean–early Bashkirian), the time between the FAD of the baphetid Loxomma and the beginning of the Nyranyan; (3) Nyranyan (late Bashkirian–Moscovian), the time between the FAD of the eureptile Hylonomus and the beginning of the Cobrean; (4) Cobrean (Kasimovian–late Gzhelian), the time between the FAD of the eupelycosaur Ianthasaurus and the beginning of the Coyotean; and (5) Coyotean (late Gzhelian–early Permian), the time between the FAD of the eupelycosaur Sphenacodon and the beginning of the Seymouran. This biochronology provides insight into some important evolutionary events in Carboniferous tetrapod evolution.
{"title":"Carboniferous tetrapod biostratigraphy, biochronology and evolutionary events","authors":"S. Lucas","doi":"10.1144/SP512-2021-5","DOIUrl":"https://doi.org/10.1144/SP512-2021-5","url":null,"abstract":"Abstract Tetrapod (amphibian and amniote) fossils of Carboniferous age are known almost exclusively from the southern part of a palaeoequatorial Euramerican province. The stratigraphic distribution of Carboniferous tetrapod fossils is used to identify five land-vertebrate faunachrons: (1) Hortonbluffian (Givetian–early Visean), the time between the first appearance datum (FAD) of tetrapods to the beginning of the Doran; (2) Doran (late Visean–early Bashkirian), the time between the FAD of the baphetid Loxomma and the beginning of the Nyranyan; (3) Nyranyan (late Bashkirian–Moscovian), the time between the FAD of the eureptile Hylonomus and the beginning of the Cobrean; (4) Cobrean (Kasimovian–late Gzhelian), the time between the FAD of the eupelycosaur Ianthasaurus and the beginning of the Coyotean; and (5) Coyotean (late Gzhelian–early Permian), the time between the FAD of the eupelycosaur Sphenacodon and the beginning of the Seymouran. This biochronology provides insight into some important evolutionary events in Carboniferous tetrapod evolution.","PeriodicalId":22055,"journal":{"name":"Special Publications","volume":"44 1","pages":"965 - 1001"},"PeriodicalIF":0.0,"publicationDate":"2021-05-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88305551","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}
S. Mahapatro, M. L. Renjith, R. K. Martha, R. Patel, D. Upadhyay, D. Sarma
Abstract In this study, we constrain the petrogenesis and U–Pb zircon age of a newly discovered alkaline complex, christened the Chaitma Alkaline Complex at the southern margin of the Central Indian Tectonic Zone in central India. The Chaitma Alkaline Complex comprises syenites and gabbros, emplaced coevally, and show features consistent with magma mixing. Geochemically, syenites are potassic–ultrapotassic (K2O/Na2O: 0.79–3.42), and contain high Ba (c. 800–2700 ppm) and Sr (c. 1400–3200 ppm). They show enrichment of the light rare earth elements (LREEs) relative to the heavy rare earth elements (HREEs) (La/Yb: 32–103) and do not display any Eu anomaly. Based on their geochemical signatures, such as low MgO (<0.87 wt%), Ni (8–16 ppm) and Cr (7–44 ppm) contents and prominent Zr–Hf negative anomaly, the syenites are inferred to have been derived by partial melting of a carbonated/metasomatized thickened lower crustal source. The coeval gabbros are undersaturated in silica (41–44 wt%), with relatively high total alkalis (Na2O + K2O: 3.7–5.1 wt%), Fe2O3 (17–19 wt%), P2O5 (3.1–4.9 wt%), Sr (1600–3400 ppm) and Ba (300–3500 ppm) contents. These have low MgO (<4.8 wt%), Ni (13–30 ppm) and Cr (18–84 ppm). Their chemistry is interpreted to be the result of interaction with the syenitic magma. These geochemical characters along with the high LREE/HREE ratio, negative trough in Nb–Ta, Zr–Hf, Ti, Sr and Rb, and positive spike of Pb in a multielement diagram, and enrichment of LILEs over HFSEs indicate their derivation from a metasomatized subduction-modified garnet–peridotite mantle source. Our study indicates that syenites and gabbros of the Chaitma Alkaline Complex were formed from genetically unrelated parental magmas derived from distinct sources. U–Pb dating of zircon yielded a magmatic emplacement age of 1626 ± 15 Ma for the syenites. The Chaitma Alkaline Complex was presumably formed during a short period of crustal extension in the midst of a protracted period of continent–continent collision and granulite-grade metamorphism (c. 1.71–1.58 Ga) at the southern margin of the Central Indian Tectonic Zone.
{"title":"Petrogenesis and U–Pb zircon dating of the Chaitma Alkaline Complex from the southern margin of the Central Indian Tectonic Zone: geodynamic implications","authors":"S. Mahapatro, M. L. Renjith, R. K. Martha, R. Patel, D. Upadhyay, D. Sarma","doi":"10.1144/SP513-2021-28","DOIUrl":"https://doi.org/10.1144/SP513-2021-28","url":null,"abstract":"Abstract In this study, we constrain the petrogenesis and U–Pb zircon age of a newly discovered alkaline complex, christened the Chaitma Alkaline Complex at the southern margin of the Central Indian Tectonic Zone in central India. The Chaitma Alkaline Complex comprises syenites and gabbros, emplaced coevally, and show features consistent with magma mixing. Geochemically, syenites are potassic–ultrapotassic (K2O/Na2O: 0.79–3.42), and contain high Ba (c. 800–2700 ppm) and Sr (c. 1400–3200 ppm). They show enrichment of the light rare earth elements (LREEs) relative to the heavy rare earth elements (HREEs) (La/Yb: 32–103) and do not display any Eu anomaly. Based on their geochemical signatures, such as low MgO (<0.87 wt%), Ni (8–16 ppm) and Cr (7–44 ppm) contents and prominent Zr–Hf negative anomaly, the syenites are inferred to have been derived by partial melting of a carbonated/metasomatized thickened lower crustal source. The coeval gabbros are undersaturated in silica (41–44 wt%), with relatively high total alkalis (Na2O + K2O: 3.7–5.1 wt%), Fe2O3 (17–19 wt%), P2O5 (3.1–4.9 wt%), Sr (1600–3400 ppm) and Ba (300–3500 ppm) contents. These have low MgO (<4.8 wt%), Ni (13–30 ppm) and Cr (18–84 ppm). Their chemistry is interpreted to be the result of interaction with the syenitic magma. These geochemical characters along with the high LREE/HREE ratio, negative trough in Nb–Ta, Zr–Hf, Ti, Sr and Rb, and positive spike of Pb in a multielement diagram, and enrichment of LILEs over HFSEs indicate their derivation from a metasomatized subduction-modified garnet–peridotite mantle source. Our study indicates that syenites and gabbros of the Chaitma Alkaline Complex were formed from genetically unrelated parental magmas derived from distinct sources. U–Pb dating of zircon yielded a magmatic emplacement age of 1626 ± 15 Ma for the syenites. The Chaitma Alkaline Complex was presumably formed during a short period of crustal extension in the midst of a protracted period of continent–continent collision and granulite-grade metamorphism (c. 1.71–1.58 Ga) at the southern margin of the Central Indian Tectonic Zone.","PeriodicalId":22055,"journal":{"name":"Special Publications","volume":"58 1","pages":"351 - 379"},"PeriodicalIF":0.0,"publicationDate":"2021-05-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88267187","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}
Abstract Identification and naming of fossil and subfossil organisms are not easy tasks. We are in the midst of a paradigm shift in how NPP taxa are named, driven in large part by (1) molecular clock taxonomic efforts in the past 25 years and (2) greater connectivity among scientific communities. Concurrent with this is the understanding that sometimes a name is not necessary, and identifying acronyms, pending further taxonomic work, or where fragmentary or synapomorphic remains cannot be assigned to their original taxon, are sufficient. The overarching goal of the paradigm shift is to maintain stability of the code and avoid increasing the number of names that refer to single taxa. The history and current state of nomenclature for non-pollen palynomorphs groups, highlighting recent developments with dinoflagellates and fungi, is given, and recommendations for a unified approach to NPP nomenclature through geological time are made.
{"title":"Nomenclature: how do we designate NPP taxa?","authors":"J. O'Keefe, N. N. Nuñez Otaño, M. V. Bianchinotti","doi":"10.1144/SP511-2020-119","DOIUrl":"https://doi.org/10.1144/SP511-2020-119","url":null,"abstract":"Abstract Identification and naming of fossil and subfossil organisms are not easy tasks. We are in the midst of a paradigm shift in how NPP taxa are named, driven in large part by (1) molecular clock taxonomic efforts in the past 25 years and (2) greater connectivity among scientific communities. Concurrent with this is the understanding that sometimes a name is not necessary, and identifying acronyms, pending further taxonomic work, or where fragmentary or synapomorphic remains cannot be assigned to their original taxon, are sufficient. The overarching goal of the paradigm shift is to maintain stability of the code and avoid increasing the number of names that refer to single taxa. The history and current state of nomenclature for non-pollen palynomorphs groups, highlighting recent developments with dinoflagellates and fungi, is given, and recommendations for a unified approach to NPP nomenclature through geological time are made.","PeriodicalId":22055,"journal":{"name":"Special Publications","volume":"26 1","pages":"77 - 89"},"PeriodicalIF":0.0,"publicationDate":"2021-04-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91073433","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}
Abstract Non-pollen palynomorphs (NPPs) are widely used to detect human activities, in addition to the anthropogenic indicators used in palynology. This paper first tries to determine the best way to approach most probable number (MPN) counting for young scientists. It then looks at the anthropogenic indicators and the different types of human activity that can reveal the studied taxa. Among the different fungal spores, coprophilous fungi are very useful to evidence pastoral activities and grazing pressure. Numerous taxa related to dung are also indicators of decaying organic matter and deserve our attention. Erosion processes due to human activities increase the representation of fungal spores. Development of carbonicolous fungal spores in association with fire and algal assemblages due to eutrophication are also considered. Indeed, studies focusing on modern analogues have greatly improved our understanding of spore taphonomy, and the relationship between spore abundance and local livestock biomass and composition.
{"title":"Detecting human impacts: non-pollen palynomorphs as proxies for human impact on the environment","authors":"E. Gauthier, I. Jouffroy-Bapicot","doi":"10.1144/SP511-2020-54","DOIUrl":"https://doi.org/10.1144/SP511-2020-54","url":null,"abstract":"Abstract Non-pollen palynomorphs (NPPs) are widely used to detect human activities, in addition to the anthropogenic indicators used in palynology. This paper first tries to determine the best way to approach most probable number (MPN) counting for young scientists. It then looks at the anthropogenic indicators and the different types of human activity that can reveal the studied taxa. Among the different fungal spores, coprophilous fungi are very useful to evidence pastoral activities and grazing pressure. Numerous taxa related to dung are also indicators of decaying organic matter and deserve our attention. Erosion processes due to human activities increase the representation of fungal spores. Development of carbonicolous fungal spores in association with fire and algal assemblages due to eutrophication are also considered. Indeed, studies focusing on modern analogues have greatly improved our understanding of spore taphonomy, and the relationship between spore abundance and local livestock biomass and composition.","PeriodicalId":22055,"journal":{"name":"Special Publications","volume":"21 1","pages":"233 - 244"},"PeriodicalIF":0.0,"publicationDate":"2021-04-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85970879","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}
L. Angiolini, G. Cisterna, Bernard Mottequin, S. Shen, G. Muttoni
Abstract We present an updated look at Carboniferous brachiopod biozonation from most of the world framed into a revised Carboniferous palaeogeography, based on a selection of the literature published on Carboniferous brachiopods since the nineteenth century. The biostratigraphic significance of the most important brachiopod taxa is synthesized in seven geographical correlations. The Mississippian is characterized by rich brachiopod faunas, with widespread taxa with a good potential for global correlation, such as Rugosochonetes, Delepinea, Buxtonia, Antiquatonia, Spinocarinifera, Marginatia, Fluctuaria, Ovatia, Rhipidomella, Lamellosathyris, Unispirifer, Tylothyris and Syringothyris. From the mid-Visean to the late Serpukhovian, taxa of gigantoproductidines are biostratigraphically significant, and occur everywhere except South America and Australia, which remain as distinct faunal successions for most of the period. A major turnover occurs at the beginning of the Pennsylvanian, characterized by a higher degree of provincialism. Pennsylvanian brachiopod faunas are diverse in China, Russia and North America, but otherwise they are less developed and are characterized mostly by endemic taxa, hampering long-distance correlation. An exception is the rapid diversification of taxa of the Choristitinae, which were widespread from the Bashkirian to the Moscovian, allowing long-distance correlation.
{"title":"Global Carboniferous brachiopod biostratigraphy","authors":"L. Angiolini, G. Cisterna, Bernard Mottequin, S. Shen, G. Muttoni","doi":"10.1144/SP512-2020-225","DOIUrl":"https://doi.org/10.1144/SP512-2020-225","url":null,"abstract":"Abstract We present an updated look at Carboniferous brachiopod biozonation from most of the world framed into a revised Carboniferous palaeogeography, based on a selection of the literature published on Carboniferous brachiopods since the nineteenth century. The biostratigraphic significance of the most important brachiopod taxa is synthesized in seven geographical correlations. The Mississippian is characterized by rich brachiopod faunas, with widespread taxa with a good potential for global correlation, such as Rugosochonetes, Delepinea, Buxtonia, Antiquatonia, Spinocarinifera, Marginatia, Fluctuaria, Ovatia, Rhipidomella, Lamellosathyris, Unispirifer, Tylothyris and Syringothyris. From the mid-Visean to the late Serpukhovian, taxa of gigantoproductidines are biostratigraphically significant, and occur everywhere except South America and Australia, which remain as distinct faunal successions for most of the period. A major turnover occurs at the beginning of the Pennsylvanian, characterized by a higher degree of provincialism. Pennsylvanian brachiopod faunas are diverse in China, Russia and North America, but otherwise they are less developed and are characterized mostly by endemic taxa, hampering long-distance correlation. An exception is the rapid diversification of taxa of the Choristitinae, which were widespread from the Bashkirian to the Moscovian, allowing long-distance correlation.","PeriodicalId":22055,"journal":{"name":"Special Publications","volume":"101 1","pages":"497 - 550"},"PeriodicalIF":0.0,"publicationDate":"2021-04-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79146257","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}
Abstract Ophiuroids, the slender-armed cousins of starfish, constitute an important component of modern marine benthos and have been used successfully in the exploration of (palaeo)-ecological and evolutionary trends, yet their fossil record is still poorly known. One of the major gaps in the known palaeobiodiversity of this group coincides with a global palaeoenvironmental crisis during the early Toarcian (Early Jurassic, 183 myr ago), known as the Jenkyns Event. Here we describe ophiuroid remains retrieved from a series of samples from the Dudelange (Luxembourg) drill core, which spans the lower part of the Toarcian, between the top of the Pliensbachian and the onset of the Jenkyns Event. A total of 21 species are recorded, including three new genera and 12 new species. Ophiuroid diversity and abundance fluctuate in parallel with depositional facies, with lowest values coinciding with black shales. Highest diversities, including exceptional occurrences of taxa nowadays restricted to deep-sea areas, are recorded from just below the black shales, corresponding to the onset of the Jenkyns Event. Our results show that even small (100 g) bulk sediment samples retrieved from drill cores can yield numerous identifiable ophiuroid remains, thus unlocking this group for the study of faunal change across palaeoenvironmental crises.
{"title":"Brittlestar diversity at the dawn of the Jenkyns Event (early Toarcian Oceanic Anoxic Event): new microfossils from the Dudelange drill core, Luxembourg","authors":"B. Thuy, Lea D. Numberger-Thuy","doi":"10.1144/SP514-2021-3","DOIUrl":"https://doi.org/10.1144/SP514-2021-3","url":null,"abstract":"Abstract Ophiuroids, the slender-armed cousins of starfish, constitute an important component of modern marine benthos and have been used successfully in the exploration of (palaeo)-ecological and evolutionary trends, yet their fossil record is still poorly known. One of the major gaps in the known palaeobiodiversity of this group coincides with a global palaeoenvironmental crisis during the early Toarcian (Early Jurassic, 183 myr ago), known as the Jenkyns Event. Here we describe ophiuroid remains retrieved from a series of samples from the Dudelange (Luxembourg) drill core, which spans the lower part of the Toarcian, between the top of the Pliensbachian and the onset of the Jenkyns Event. A total of 21 species are recorded, including three new genera and 12 new species. Ophiuroid diversity and abundance fluctuate in parallel with depositional facies, with lowest values coinciding with black shales. Highest diversities, including exceptional occurrences of taxa nowadays restricted to deep-sea areas, are recorded from just below the black shales, corresponding to the onset of the Jenkyns Event. Our results show that even small (100 g) bulk sediment samples retrieved from drill cores can yield numerous identifiable ophiuroid remains, thus unlocking this group for the study of faunal change across palaeoenvironmental crises.","PeriodicalId":22055,"journal":{"name":"Special Publications","volume":"20 1","pages":"83 - 119"},"PeriodicalIF":0.0,"publicationDate":"2021-04-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85781739","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}
M. Dora, K. Randive, R. Meshram, T. Meshram, S. Baswani, M. Korakoppa, V. P. Malviya
Abstract The lamproites and kimberlites are well known from the Eastern Bastar Craton, Central India. However, a Proterozoic lamprophyre dyke is discussed here, from the Western Bastar Craton (WBC). The field geology, petrographic, mineralogical and whole-rock and in-situ trace element geochemistry of biotite are described to understand the petrogenesis and lithospheric evolution in the WBC. The Thanewasna lamprophyre (TL) is undeformed and unmetamorphosed, intruded into c. 2.5 Ga charnockite and metagabbro but closely associated with c. 1.62 Ga undeformed Mul granite. The TL has a characteristic porphyritic texture, dominated by phenocrysts of biotite, microphenocryst of amphibole, clinopyroxene and a groundmass controlled by feldspar. Mineral chemistry of biotite and amphibole suggest a calc-alkaline (CAL) type, and pyroxene chemistry reveals an orogenic setting. The TL is characterized by high SiO2 and low TiO2, MgO, Ni and Cr, consistent with its subcontinental lithospheric origin. The presence of crustal xenolith and ocelli texture followed by observed variations in Th/Yb, Hf/Sm, La/Nb, Ta/La, Nb/Yb, Ba/Nb indicate substantial crustal contamination. Whole-rock and in-situ biotite analysis by laser ablation inductively coupled plasma mass spectrometry show low concentrations of Ni (30–50 ppm) and Cr (70–150 ppm), pointing to the parental magma evolved nature. Enrichment in H2O, reflected in magmatic mica dominance, combined with high large ion lithophile element, Th/Yb ratios, and striking negative Nb–Ta anomalies in trace element patterns, is consistent with a source that was metasomatized by hydrous fluids corresponding to those generated by subduction-related processes. Significant Zr–Hf and Ti anomalies in the primitive mantle normalized multi-element plots and the rare earth element pattern of the TL, similar to the global CAL average trend, including Eastern Dharwar Craton lamprophyres. Our findings provide substantial petrological and geochemical constraints on petrogenesis and geodynamics. However, the geodynamic trigger that generated CAL magmatism and its role in Cu–Au metallogeny in the WBC, Central India, is presently indistinct in the absence of isotopic studies. Nevertheless, the lamprophyre dyke is emplaced close to the Cu–(Au) deposit at Thanewasna.
{"title":"Petrogenesis of a calc-alkaline lamprophyre (minette) from Thanewasna, Western Bastar Craton, Central India: insights from mineral, bulk rock and in-situ trace element geochemistry","authors":"M. Dora, K. Randive, R. Meshram, T. Meshram, S. Baswani, M. Korakoppa, V. P. Malviya","doi":"10.1144/SP513-2020-258","DOIUrl":"https://doi.org/10.1144/SP513-2020-258","url":null,"abstract":"Abstract The lamproites and kimberlites are well known from the Eastern Bastar Craton, Central India. However, a Proterozoic lamprophyre dyke is discussed here, from the Western Bastar Craton (WBC). The field geology, petrographic, mineralogical and whole-rock and in-situ trace element geochemistry of biotite are described to understand the petrogenesis and lithospheric evolution in the WBC. The Thanewasna lamprophyre (TL) is undeformed and unmetamorphosed, intruded into c. 2.5 Ga charnockite and metagabbro but closely associated with c. 1.62 Ga undeformed Mul granite. The TL has a characteristic porphyritic texture, dominated by phenocrysts of biotite, microphenocryst of amphibole, clinopyroxene and a groundmass controlled by feldspar. Mineral chemistry of biotite and amphibole suggest a calc-alkaline (CAL) type, and pyroxene chemistry reveals an orogenic setting. The TL is characterized by high SiO2 and low TiO2, MgO, Ni and Cr, consistent with its subcontinental lithospheric origin. The presence of crustal xenolith and ocelli texture followed by observed variations in Th/Yb, Hf/Sm, La/Nb, Ta/La, Nb/Yb, Ba/Nb indicate substantial crustal contamination. Whole-rock and in-situ biotite analysis by laser ablation inductively coupled plasma mass spectrometry show low concentrations of Ni (30–50 ppm) and Cr (70–150 ppm), pointing to the parental magma evolved nature. Enrichment in H2O, reflected in magmatic mica dominance, combined with high large ion lithophile element, Th/Yb ratios, and striking negative Nb–Ta anomalies in trace element patterns, is consistent with a source that was metasomatized by hydrous fluids corresponding to those generated by subduction-related processes. Significant Zr–Hf and Ti anomalies in the primitive mantle normalized multi-element plots and the rare earth element pattern of the TL, similar to the global CAL average trend, including Eastern Dharwar Craton lamprophyres. Our findings provide substantial petrological and geochemical constraints on petrogenesis and geodynamics. However, the geodynamic trigger that generated CAL magmatism and its role in Cu–Au metallogeny in the WBC, Central India, is presently indistinct in the absence of isotopic studies. Nevertheless, the lamprophyre dyke is emplaced close to the Cu–(Au) deposit at Thanewasna.","PeriodicalId":22055,"journal":{"name":"Special Publications","volume":"90 1","pages":"179 - 207"},"PeriodicalIF":0.0,"publicationDate":"2021-04-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85641702","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}
Abstract This Special Publication combines results obtained by interdisciplinary groups from numerous academic institutions working on Paleoproterozoic formations to decipher the origins of the main mineralization resources in the West African Craton (WAC) and their impacts on African economic development. Structural, geophysical, sedimentological, stratigraphical, geochemical, petrophysical and mineralogical analyses have been used to highlight the complexities involved in mineralization emplacement and its origin and evolution within the WAC. Fourteen articles, mainly of basic research carried out in the WAC and surrounding areas, contribute to new knowledge in mineral research with updated references. They show that the geodynamic evolution of the WAC is complex from one area to another: it involves subduction, collision and obduction during several deformation phases ranging from Birimian (2.3–2.0 Ga) to Pan-African (650–450 Ma) events. Mineralization is mainly controlled by tectonics within shear zones, orogenic belts, basins and faulting systems occurring in the various corridors. Mineralized fluid circulation is stressed and injected into appropriate formations and precipitate several types of well-documented ore deposits: porphyry, metal-bearing, volcanogenic massive sulfide, sedimentary exhalative and lateritic. Various modelling techniques, when integrated, help in understanding the mechanisms of mineralization emplacement, some of which are still a matter of debate. Traditional and industrial exploitation of ore deposits, mainly gold, may inadvertently cause pollution to water tables and rivers, thus affecting the environment including watersheds. The challenge for further studies is mitigation for sustainable development that can be appropriately used to minimize such damage. The aim of this volume is thus to bring new insights to research activities on ore deposits within the WAC.
本特刊综合了多家古元古代学术机构跨学科研究小组的成果，揭示了西非克拉通(WAC)主要矿化资源的来源及其对非洲经济发展的影响。构造、地球物理、沉积学、地层学、地球化学、岩石物理和矿物学分析已被用来强调矿化侵位及其在WAC内的起源和演化的复杂性。14篇文章，主要是在WAC和周边地区进行的基础研究，为矿物研究提供了新的知识，并更新了参考文献。它们表明，WAC的地球动力学演化是复杂的，在briimian (2.3-2.0 Ga)到pan - africa (650-450 Ma)的几个变形阶段，WAC经历了俯冲、碰撞和逆冲。成矿作用主要受剪切带、造山带、盆地和各走廊断裂体系内的构造控制。矿化流体循环被强调并注入到适当的地层中，沉淀了几种有充分记录的矿床:斑岩型、含金属型、火山成因块状硫化物型、沉积喷发型和红土型。各种建模技术综合起来，有助于理解矿化侵位的机制，其中一些仍然是一个有争议的问题。传统和工业开采矿藏，主要是金矿，可能无意中对地下水位和河流造成污染，从而影响包括流域在内的环境。进一步研究面临的挑战是，可以适当地利用减轻影响促进可持续发展，以尽量减少这种损害。因此，本卷的目的是为WAC内的矿床研究活动带来新的见解。
{"title":"Mineralization and sustainable development in the West African Craton: from field observations to modelling","authors":"T. Aïfa","doi":"10.1144/SP502-2021-21","DOIUrl":"https://doi.org/10.1144/SP502-2021-21","url":null,"abstract":"Abstract This Special Publication combines results obtained by interdisciplinary groups from numerous academic institutions working on Paleoproterozoic formations to decipher the origins of the main mineralization resources in the West African Craton (WAC) and their impacts on African economic development. Structural, geophysical, sedimentological, stratigraphical, geochemical, petrophysical and mineralogical analyses have been used to highlight the complexities involved in mineralization emplacement and its origin and evolution within the WAC. Fourteen articles, mainly of basic research carried out in the WAC and surrounding areas, contribute to new knowledge in mineral research with updated references. They show that the geodynamic evolution of the WAC is complex from one area to another: it involves subduction, collision and obduction during several deformation phases ranging from Birimian (2.3–2.0 Ga) to Pan-African (650–450 Ma) events. Mineralization is mainly controlled by tectonics within shear zones, orogenic belts, basins and faulting systems occurring in the various corridors. Mineralized fluid circulation is stressed and injected into appropriate formations and precipitate several types of well-documented ore deposits: porphyry, metal-bearing, volcanogenic massive sulfide, sedimentary exhalative and lateritic. Various modelling techniques, when integrated, help in understanding the mechanisms of mineralization emplacement, some of which are still a matter of debate. Traditional and industrial exploitation of ore deposits, mainly gold, may inadvertently cause pollution to water tables and rivers, thus affecting the environment including watersheds. The challenge for further studies is mitigation for sustainable development that can be appropriately used to minimize such damage. The aim of this volume is thus to bring new insights to research activities on ore deposits within the WAC.","PeriodicalId":22055,"journal":{"name":"Special Publications","volume":"1 1","pages":"1 - 29"},"PeriodicalIF":0.0,"publicationDate":"2021-04-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83705031","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}
S. Lucas, M. Stimson, Olivia A. King, J. Calder, Chris F. Mansky, Brian L. Hebert, A. Hunt
Abstract The Carboniferous record of tetrapod footprints is mostly of Euramerican origin and provides the basis for a footprint biostratigraphy and biochronology of Carboniferous time that identifies four tetrapod footprint biochrons: (1) stem-tetrapod biochron of Middle Devonian–early Tournaisian age; (2) Hylopus biochron of middle Tournaisian–early Bashkirian age; (3) Notalacerta–Dromopus interval biochron of early Bashkirian–Kasimovian age; and (4) Dromopus biochron of Kasimovian–early Permian age. Particularly significant is the Carboniferous tetrapod footprint record of the Maritimes basin of eastern Canada (New Brunswick, Nova Scotia and Prince Edward Island), which encompasses well-dated and stratigraphically superposed footprint assemblages of Early Mississippian–early Permian age. The Carboniferous tetrapod footprint record provides these important biostratigraphic datums: (1) oldest temnospondyls (middle Tournaisian); (2) oldest reptiliomorphs, likely anthracosaurs (middle Tournaisian); (3) oldest amniotes (early Bashkirian); and (4) oldest high-fibre herbivores (Bashkirian). Carboniferous tetrapod footprints thus provide significant insight into some major events of the Carboniferous evolution of tetrapods.
{"title":"Carboniferous tetrapod footprint biostratigraphy, biochronology and evolutionary events","authors":"S. Lucas, M. Stimson, Olivia A. King, J. Calder, Chris F. Mansky, Brian L. Hebert, A. Hunt","doi":"10.1144/SP512-2020-235","DOIUrl":"https://doi.org/10.1144/SP512-2020-235","url":null,"abstract":"Abstract The Carboniferous record of tetrapod footprints is mostly of Euramerican origin and provides the basis for a footprint biostratigraphy and biochronology of Carboniferous time that identifies four tetrapod footprint biochrons: (1) stem-tetrapod biochron of Middle Devonian–early Tournaisian age; (2) Hylopus biochron of middle Tournaisian–early Bashkirian age; (3) Notalacerta–Dromopus interval biochron of early Bashkirian–Kasimovian age; and (4) Dromopus biochron of Kasimovian–early Permian age. Particularly significant is the Carboniferous tetrapod footprint record of the Maritimes basin of eastern Canada (New Brunswick, Nova Scotia and Prince Edward Island), which encompasses well-dated and stratigraphically superposed footprint assemblages of Early Mississippian–early Permian age. The Carboniferous tetrapod footprint record provides these important biostratigraphic datums: (1) oldest temnospondyls (middle Tournaisian); (2) oldest reptiliomorphs, likely anthracosaurs (middle Tournaisian); (3) oldest amniotes (early Bashkirian); and (4) oldest high-fibre herbivores (Bashkirian). Carboniferous tetrapod footprints thus provide significant insight into some major events of the Carboniferous evolution of tetrapods.","PeriodicalId":22055,"journal":{"name":"Special Publications","volume":"46 1","pages":"933 - 963"},"PeriodicalIF":0.0,"publicationDate":"2021-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80655951","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}
Abstract The Halaha River–Chaoer River (HC) volcanic field in the Greater Hinggan Mountain Range (NE China) consists of at least 41 monogenetic basaltic volcanoes. Strombolian, violent Strombolian and phreatomagmatic eruptions, as well as the transitional eruptions, generated simple volcanic cones (single vent) and composite volcanic cones (multiple vents). The simple elongated cone is the most abundant geomorphology type. By analysing the elongated crater and coalescent aligned circular crater, cone breaching and depression, and aligned vents, we identified a number of magma-feeding fissures. The majority of these fissures strike NE–ENE. Accordingly, we infer that the regional stress field affected volcanism in the HC field. The lavas in this field are alkali basalts that are enriched in light rare earth elements (La/YbN = 7.9–24.5). Their ocean island basalt-like rare earth element and spider-diagram patterns, high Nb/U ratios and high TiO2 contents (>2 wt%) indicate that the basalts were derived from the asthenosphere mantle. Both the asthenosphere upwelling and the tectonic forces are the key controlling factors of the volcanism in the HC field.
{"title":"Geomorphology and geochemistry of the Late Cenozoic volcanoes in the Halaha River–Chaoer River volcanic fields, western Greater Hinggan Mountain Range, NE China","authors":"Yong-Wei Zhao, H. Zou, Ni Li","doi":"10.1144/SP510-2020-82","DOIUrl":"https://doi.org/10.1144/SP510-2020-82","url":null,"abstract":"Abstract The Halaha River–Chaoer River (HC) volcanic field in the Greater Hinggan Mountain Range (NE China) consists of at least 41 monogenetic basaltic volcanoes. Strombolian, violent Strombolian and phreatomagmatic eruptions, as well as the transitional eruptions, generated simple volcanic cones (single vent) and composite volcanic cones (multiple vents). The simple elongated cone is the most abundant geomorphology type. By analysing the elongated crater and coalescent aligned circular crater, cone breaching and depression, and aligned vents, we identified a number of magma-feeding fissures. The majority of these fissures strike NE–ENE. Accordingly, we infer that the regional stress field affected volcanism in the HC field. The lavas in this field are alkali basalts that are enriched in light rare earth elements (La/YbN = 7.9–24.5). Their ocean island basalt-like rare earth element and spider-diagram patterns, high Nb/U ratios and high TiO2 contents (>2 wt%) indicate that the basalts were derived from the asthenosphere mantle. Both the asthenosphere upwelling and the tectonic forces are the key controlling factors of the volcanism in the HC field.","PeriodicalId":22055,"journal":{"name":"Special Publications","volume":"91 1","pages":"81 - 97"},"PeriodicalIF":0.0,"publicationDate":"2021-03-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78099832","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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