Celso de Barros Gomes, Piero Comin-Chiaramonti, Victor Fernandez Velázquez
{"title":"巴拉圭东部的钠碱性岩浆活动:地球化学和岩石学意义","authors":"Celso de Barros Gomes, Piero Comin-Chiaramonti, Victor Fernandez Velázquez","doi":"10.1590/2317-4889202320220095","DOIUrl":null,"url":null,"abstract":"Associated with subordinate potassic rocks, Mesozoic to Cenozoic sodic alkaline rocks are represented by four distinct provinces in Eastern Paraguay: Alto Paraguay, Central, Misiones, and Asunción; additional Rio Apa and Amambay provinces are exclusively of potassic affinity. Alkaline magmatism is clearly controlled by a tectonic extensional regime that generated NW-SE-trending faults and grabens. It varies in composition, with the intrusive sodic rocks mainly composed of foid syenites and quartz-bearing syenites and the potassic ones of syenites, syenogabbros, and gabbros, all of which are accompanied by fine-grained hypoabissal and volcanic counterparts. In the Central Province, potassic and sodic rocks occur together and are represented by two distinct magmatic series: basanites-phonolites and alkali basalts-trachytes/trachyphonolites. Ultramafic sodic rocks (ankaratrites and nephelinites) are uniquely found in the Misiones and Asunción provinces. In general, the sodic rocks exhibit LILE enrichment, high field strength elements depletion, and Nb-Ta positive anomalies in the mantle's normalized incompatible elements (IE) distribution. Chondrite-normalized rare earth element (REE) diagrams point to strong REE enrichment and high light/heavy rare earth element fractionation in different subparallel patterns. Conversely, the potassic rocks display negative anomalies of Nb-Ta and are fractionated in REE. In the initial Sri versus Ndi diagram, the sodic rocks approach to bulk earth, whereas the potassic ones plot into the Sr-enriched quadrant. Sr-Nd-Pb isotope data suggest that a high U/Pb mantle component played an important role in the genesis of the Late Early Cretaceous and Tertiary sodic magmas, while an enriched mantle component dominated the Early Cretaceous potassic magmas. The close association of potassic and sodic rocks implies that their parental magmas derived from a subcontinental mantle variable in composition enriched in IE.","PeriodicalId":9221,"journal":{"name":"Brazilian Journal of Geology","volume":"22 1","pages":"0"},"PeriodicalIF":1.3000,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":"{\"title\":\"Sodic alkaline magmatism in Eastern Paraguay revisited: geochemical and petrological implications\",\"authors\":\"Celso de Barros Gomes, Piero Comin-Chiaramonti, Victor Fernandez Velázquez\",\"doi\":\"10.1590/2317-4889202320220095\",\"DOIUrl\":null,\"url\":null,\"abstract\":\"Associated with subordinate potassic rocks, Mesozoic to Cenozoic sodic alkaline rocks are represented by four distinct provinces in Eastern Paraguay: Alto Paraguay, Central, Misiones, and Asunción; additional Rio Apa and Amambay provinces are exclusively of potassic affinity. Alkaline magmatism is clearly controlled by a tectonic extensional regime that generated NW-SE-trending faults and grabens. It varies in composition, with the intrusive sodic rocks mainly composed of foid syenites and quartz-bearing syenites and the potassic ones of syenites, syenogabbros, and gabbros, all of which are accompanied by fine-grained hypoabissal and volcanic counterparts. In the Central Province, potassic and sodic rocks occur together and are represented by two distinct magmatic series: basanites-phonolites and alkali basalts-trachytes/trachyphonolites. Ultramafic sodic rocks (ankaratrites and nephelinites) are uniquely found in the Misiones and Asunción provinces. In general, the sodic rocks exhibit LILE enrichment, high field strength elements depletion, and Nb-Ta positive anomalies in the mantle's normalized incompatible elements (IE) distribution. Chondrite-normalized rare earth element (REE) diagrams point to strong REE enrichment and high light/heavy rare earth element fractionation in different subparallel patterns. Conversely, the potassic rocks display negative anomalies of Nb-Ta and are fractionated in REE. In the initial Sri versus Ndi diagram, the sodic rocks approach to bulk earth, whereas the potassic ones plot into the Sr-enriched quadrant. Sr-Nd-Pb isotope data suggest that a high U/Pb mantle component played an important role in the genesis of the Late Early Cretaceous and Tertiary sodic magmas, while an enriched mantle component dominated the Early Cretaceous potassic magmas. The close association of potassic and sodic rocks implies that their parental magmas derived from a subcontinental mantle variable in composition enriched in IE.\",\"PeriodicalId\":9221,\"journal\":{\"name\":\"Brazilian Journal of Geology\",\"volume\":\"22 1\",\"pages\":\"0\"},\"PeriodicalIF\":1.3000,\"publicationDate\":\"2023-01-01\",\"publicationTypes\":\"Journal Article\",\"fieldsOfStudy\":null,\"isOpenAccess\":false,\"openAccessPdf\":\"\",\"citationCount\":\"0\",\"resultStr\":null,\"platform\":\"Semanticscholar\",\"paperid\":null,\"PeriodicalName\":\"Brazilian Journal of Geology\",\"FirstCategoryId\":\"1085\",\"ListUrlMain\":\"https://doi.org/10.1590/2317-4889202320220095\",\"RegionNum\":4,\"RegionCategory\":\"地球科学\",\"ArticlePicture\":[],\"TitleCN\":null,\"AbstractTextCN\":null,\"PMCID\":null,\"EPubDate\":\"\",\"PubModel\":\"\",\"JCR\":\"Q3\",\"JCRName\":\"GEOSCIENCES, MULTIDISCIPLINARY\",\"Score\":null,\"Total\":0}","platform":"Semanticscholar","paperid":null,"PeriodicalName":"Brazilian Journal of Geology","FirstCategoryId":"1085","ListUrlMain":"https://doi.org/10.1590/2317-4889202320220095","RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q3","JCRName":"GEOSCIENCES, MULTIDISCIPLINARY","Score":null,"Total":0}
Sodic alkaline magmatism in Eastern Paraguay revisited: geochemical and petrological implications
Associated with subordinate potassic rocks, Mesozoic to Cenozoic sodic alkaline rocks are represented by four distinct provinces in Eastern Paraguay: Alto Paraguay, Central, Misiones, and Asunción; additional Rio Apa and Amambay provinces are exclusively of potassic affinity. Alkaline magmatism is clearly controlled by a tectonic extensional regime that generated NW-SE-trending faults and grabens. It varies in composition, with the intrusive sodic rocks mainly composed of foid syenites and quartz-bearing syenites and the potassic ones of syenites, syenogabbros, and gabbros, all of which are accompanied by fine-grained hypoabissal and volcanic counterparts. In the Central Province, potassic and sodic rocks occur together and are represented by two distinct magmatic series: basanites-phonolites and alkali basalts-trachytes/trachyphonolites. Ultramafic sodic rocks (ankaratrites and nephelinites) are uniquely found in the Misiones and Asunción provinces. In general, the sodic rocks exhibit LILE enrichment, high field strength elements depletion, and Nb-Ta positive anomalies in the mantle's normalized incompatible elements (IE) distribution. Chondrite-normalized rare earth element (REE) diagrams point to strong REE enrichment and high light/heavy rare earth element fractionation in different subparallel patterns. Conversely, the potassic rocks display negative anomalies of Nb-Ta and are fractionated in REE. In the initial Sri versus Ndi diagram, the sodic rocks approach to bulk earth, whereas the potassic ones plot into the Sr-enriched quadrant. Sr-Nd-Pb isotope data suggest that a high U/Pb mantle component played an important role in the genesis of the Late Early Cretaceous and Tertiary sodic magmas, while an enriched mantle component dominated the Early Cretaceous potassic magmas. The close association of potassic and sodic rocks implies that their parental magmas derived from a subcontinental mantle variable in composition enriched in IE.
期刊介绍:
The Brazilian Journal of Geology (BJG) is a quarterly journal published by the Brazilian Geological Society with an electronic open access version that provides an in-ternacional medium for the publication of original scientific work of broad interest concerned with all aspects of the earth sciences in Brazil, South America, and Antarctica, in-cluding oceanic regions adjacent to these regions. The BJG publishes papers with a regional appeal and more than local significance in the fields of mineralogy, petrology, geochemistry, paleontology, sedimentology, stratigraphy, structural geology, tectonics, neotectonics, geophysics applied to geology, volcanology, metallogeny and mineral deposits, marine geology, glaciology, paleoclimatology, geochronology, biostratigraphy, engineering geology, hydrogeology, geological hazards and remote sensing, providing a niche for interdisciplinary work on regional geology and Earth history.
The BJG publishes articles (including review articles), rapid communications, articles with accelerated review processes, editorials, and discussions (brief, objective and concise comments on recent papers published in BJG with replies by authors).
Manuscripts must be written in English. Companion papers will not be accepted.