{"title":"Magnetic and radiometric signatures of alkaline rocks and gabbros from the Ponta Grossa Arch, southeastern Paraná Basin, Brazil","authors":"V. Silva, F. J. Ferreira","doi":"10.1590/2317-4889202120200051","DOIUrl":null,"url":null,"abstract":"Abstract We present airborne magnetic and radiometric characteristics of some igneous suites from the Ponta Grossa Arch Alkaline Province (southern Brazil), namely the Bairro da Cruz, Banhadao, Barra do Itapirapua, Mato Preto and Tunas complexes, Barra do Teixeira Phonolite, Itapirapua Nepheline syenite, and Jose Fernandes Gabbro. We applied magnetic susceptibility 3D inversions using the total magnetic anomaly data together with its analytic signal of the vertical integral and the vertical integral of the analytic signal for the Bairro da Cruz, Jose Fernandes, and Tunas intrusions. Gamma-ray spectrometric methods involved analyses of basic, ternary, and ratio maps, thorium-normalized parameters, and radioelement concentrations at sampled data points. Stacked profiles from geophysical data were generated for each rock. The Bairro da Cruz, Jose Fernandes, and Tunas intrusions are associated with dipolar anomalies with normal polarity whereas their inversions show low magnetic susceptibility values. Gamma-ray spectrometric results allowed us to verify that all complexes are enriched mainly in eTh. Carbonatite bodies showed the highest contents of eTh and eU. Our findings are consistent with geophysical responses of alkaline bodies and impact the understanding of geophysical signatures, especially radiometric ones, of alkaline provinces in Brazil.","PeriodicalId":9221,"journal":{"name":"Brazilian Journal of Geology","volume":null,"pages":null},"PeriodicalIF":1.3000,"publicationDate":"2021-08-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Brazilian Journal of Geology","FirstCategoryId":"89","ListUrlMain":"https://doi.org/10.1590/2317-4889202120200051","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}
引用次数: 0
Abstract
Abstract We present airborne magnetic and radiometric characteristics of some igneous suites from the Ponta Grossa Arch Alkaline Province (southern Brazil), namely the Bairro da Cruz, Banhadao, Barra do Itapirapua, Mato Preto and Tunas complexes, Barra do Teixeira Phonolite, Itapirapua Nepheline syenite, and Jose Fernandes Gabbro. We applied magnetic susceptibility 3D inversions using the total magnetic anomaly data together with its analytic signal of the vertical integral and the vertical integral of the analytic signal for the Bairro da Cruz, Jose Fernandes, and Tunas intrusions. Gamma-ray spectrometric methods involved analyses of basic, ternary, and ratio maps, thorium-normalized parameters, and radioelement concentrations at sampled data points. Stacked profiles from geophysical data were generated for each rock. The Bairro da Cruz, Jose Fernandes, and Tunas intrusions are associated with dipolar anomalies with normal polarity whereas their inversions show low magnetic susceptibility values. Gamma-ray spectrometric results allowed us to verify that all complexes are enriched mainly in eTh. Carbonatite bodies showed the highest contents of eTh and eU. Our findings are consistent with geophysical responses of alkaline bodies and impact the understanding of geophysical signatures, especially radiometric ones, of alkaline provinces in Brazil.
摘要研究了巴西南部蓬塔格罗萨Arch Alkaline Province的一些火成岩套系,即Bairro da Cruz、Banhadao、Barra do Itapirapua、matto Preto和Tunas杂岩、Barra do Teixeira Phonolite、Itapirapua Nepheline正长岩和Jose Fernandes辉长岩的航空磁和辐射特征。针对Bairro da Cruz、Jose Fernandes和Tunas侵入体,利用总磁异常数据及其垂向积分解析信号和垂向积分解析信号进行磁化率三维反演。伽玛射线光谱分析方法包括分析基本图、三元图和比值图、钍归一化参数和采样数据点的放射性元素浓度。根据地球物理数据为每块岩石生成叠加剖面。Bairro da Cruz、Jose Fernandes和Tunas侵入体与正极性的偶极异常有关,而它们的反转显示出低磁化率值。伽玛射线谱分析结果证实所有配合物主要富集在eTh中。碳酸盐岩中eTh和eU含量最高。我们的发现与巴西碱矿体的地球物理响应一致,并影响了对巴西碱矿省地球物理特征,特别是辐射特征的理解。
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.